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The effect of shoe sole tread groove depth on the friction coefficient with different tread groove widths, floors and contaminants
Abstract
Slipping and falling are common phenomena in both workplaces and our daily activities. The risks associated with slipping and falling are related to the materials of footwear/floor, contamination condition, and geometric design of the sole. Shoe soles of various tread design are very common. Tread pattern of the shoe affects friction especially under liquid-contaminated conditions. Verification of the effects of tread groove depth is significant in assisting designers in designing proper footwear for workers exposed to slippery floor conditions. In this study, we measured the friction coefficients using the Neolite footwear pads on the terrazzo, steel, and vinyl floors under three liquid-contaminated conditions. A Brungraber Mark II slipmeter was used. The footwear pads had tread grooves with a width of either 3 or 9mm. The depth of the tread grooves ranged from 1 to 5mm. The results showed that tread groove depth affected the friction coefficients significantly. Higher friction values were recorded for footwear pads with deeper tread grooves on wet and water-detergent-contaminated floors. The averaged coefficient of friction (COF) gain per tread groove depth increase in millimeter under these two surface conditions ranged from 0.018 to 0.108, depending on the tread groove width, floor, and contaminant.
... Sperry (1942) refined this technique to create razor siping, involving cutting thin lines into a sole to provide better traction (O'Meara, 2014), producing the first set of deck shoes. Manipulation of tread groove depth and orientation affects COF readings significantly in nonmarine footwear Li et al., 2006;Liu, Lee, Lin, Li, & Chen, 2013). The structural integrity of the siping of a sole would appear to be dependent on the hardness of that sole, however, there is no proven correlation between sole hardness and COF in commercial footwear (Gao, Abeysekera, Hirvonen, & Gr€ onqvist, 2004). ...
... This concept can be simplified into editing and analysing the brightness of a photo; a more accessible technique requiring less equipment. As identified by Li et al. (2006), surface, in this case deck coverage, impacts COF. Hendricks' (2013) study on surfaces only compared six variations of boat decking, some of which were unsustainable for full deck coverage, using only one shoe on a variable inclining plane. ...
... This is due to the squeeze film effect created by the liquid between the floor and the sole isolating the contact surface area, and thus reducing the friction, as explained by Moore (1972). Many studies using standard contaminants show a trend between all substances tested; a greater tread groove and depth combined with grooves long enough to drain the liquid increase the COF (Li et al., 2006). Such contaminants are generally water, a water and detergent solution, or oil, however, there do not appear to be any studies involving the use of saltwater. ...
There is a distinct lack of research into the vital role and impact of marine footwear on the safety of crew members. Using a variable inclining plane, the grip interaction between marine footwear and common vessel deck surfaces was measured. Angle of slip measurements were used to calculate static coefficient of friction (COF) values. Nine shoes and eight deck surfaces were tested. From the measurements, the static COF values were calculated with mean values representing performance level, and a two-way ANOVA showed that both shoe and deck choice impacted the static COF (p < 0.001). Some marine footwear soles performed more successfully on one specific deck surface whilst others performed on a multitude of deck surfaces. A Pearson’s correlation test found a significant correlation between sole heel hardness and COF (p < 0.001). Findings from this research have potential safety implications in the design and marketing of marine footwear in relation to deck surfaces and highlighted the need for further research within the marine environment.
... Footwear characteristics such as the boot shaft height, mass, mid-sole hardness and thickness, elevated heels and type of material of the footwear influence balance and gait and ultimately the slip propensity in a slippery condition. Especially, the effect of the shoe sole tread patterns on slip propensity (Li et al., 2006;Li and Chen, 2005) and the effect of heel height on slip propensity have been studied previously (Blanchette et al., 2011). Design characteristics such tread groove depth, width and pattern help in prevention of slips and falls in liquid collected walking surfaces. ...
... Design characteristics such tread groove depth, width and pattern help in prevention of slips and falls in liquid collected walking surfaces. The average coefficient of friction gain per mm of tread groove depth under slippery conditions ranged from 0.018 to 0.108 (Li et al., 2006), while wider tread groove and tread groove orientation that are perpendicular to the friction measurement have higher coefficient of friction. High heeled shoes have been shown to use a greater utilized coefficient of friction thereby increasing the friction demand during walking which is related to an increase in the resultant shear force and a decrease in the vertical force and thereby increasing the probability of a slip (Blanchette et al., 2011). ...
... Although none of the slips trials resulted in a fall, the STD demonstrated significantly greater slip parameters that can contribute to an increased incidence of slip induced falls compared to the MIN. Extrinsic factors such as the footwear's geometrical design characteristics have been shown to affect human balance, gait and slip outcomes (Chander et al., 2014(Chander et al., , 2015a(Chander et al., , 2015bPerry et al., 2007;Menant et al., 2008;Chander et al., 2016aChander et al., , 2016bChander et al., , 2017 and especially the sole design parameters such as the depth, width and orientation of the tread groove have been demonstrated as important factors affecting the coefficient of friction between the footwear-floor interface (Li and Chen, 2005;Li et al., 2006;Chander et al., 2016b). Even though the surface area of the sole of STD was greater than MIN's sole (288.6 ± 24.1 cm 2 compared to 235.4 ± 8.2 cm 2 ), the number of tread grooves were more in MIN compared to STD. ...
Introduction
Slips, trips and falls due to an induced loss balance have been identified as the leading cause of occupational injuries. This study aimed to analyze the impact of two military boots, standard boot (STD) and minimalist boot (MIN) on slip events, before (PRE) and after (POST) a military type load carrying task.
Methods
Sixteen male participants (age: 27 ± 3.9 years; height: 178 ± 6.2 cm, mass: 87 ± 12.4 kg) were tested for heel kinematics using motion capture, during unexpected (US) and expected slips (ES) both before and after the task. Slip parameters of heel slip distance (HSD) and mean heel slip velocity (MHSV) were analyzed with a 2 (STD × MIN) × 2 (PRE × POST) × 2 (US × ES) repeated measures ANOVA.
Results
Significantly greater HSD (p = 0.002) and MHSV (p = 0.001) were demonstrated in STD compared to MIN, regardless of the load carrying workload and the type of slip. No significant interactions between boots, workload and slip type were found. MIN exhibited a greater percent of non-hazardous slips compared to STD.
Conclusions
Greater HSD and MHSV seen in STD, suggests that MIN performed better under slippery conditions. The military type workload and the type of slip did not appear to influence slip parameters, with boot differences seen as the major influence on these slip outcomes. MIN boot's better performance could be attributed to the minimalist sole, tread and groove pattern, lighter mass and flexible shaft aiding in better maneuvering under slippery conditions.
Relevance to industry
Slip outcomes in two different military boots, before and after a military type load carrying workload are addressed. The lighter minimalist tactical boot outperformed the standard tactical boot, under slippery conditions. Findings from this study will help offer suggestions for footwear design in the military, especially for maneuvering slippery environment.
... Previous research has also suggested that variability exists across shoes that are marketed as SR (Health and Safety Laboratory U.K., 2009). Certain outsole features like tread depth, width, orientation and hardness affect ACOF (Blanchette and Powers, 2015a;Chen, 2004, 2005;Li et al., 2006;Strobel et al., 2012;Tsai and Powers, 2008). Most of this previous research used custom outsole designs (Blanchette and Powers, 2015a;Chen, 2004, 2005;Li et al., 2006) as opposed to commercially available shoes. ...
... Certain outsole features like tread depth, width, orientation and hardness affect ACOF (Blanchette and Powers, 2015a;Chen, 2004, 2005;Li et al., 2006;Strobel et al., 2012;Tsai and Powers, 2008). Most of this previous research used custom outsole designs (Blanchette and Powers, 2015a;Chen, 2004, 2005;Li et al., 2006) as opposed to commercially available shoes. A recent review paper noted the incongruence in complexity between custom outsole designs and actual shoes (Chang et al., 2016). ...
... Therefore, a range of ACOF values exist for a given shoe across different potential test conditions. Furthermore, the rank order of ACOF across different shoes can change across different floorings or contaminants (Grönqvist, 1995;Li et al., 2006). Previous researchers have suggested that tests should be conducted using realistic floorings and contaminants (i.e., environmental fidelity) to account for these complexities (Chang et al., 2003). ...
The variability in friction and slip propensity across slip resistant (SR) shoes is poorly understood. This study aimed to quantify the impact of shoe design features on the available coefficient of friction (ACOF) across shoes labeled as SR. Differences in ACOF and the slipping rate across SR shoes were also quantified. Twelve shoes were tested across five types of flooring and three contaminant conditions using a whole shoe mechanical slip tester. Geometric and hardness parameters were measured to determine the effect of heel outsole design on ACOF. The rate of slipping was evaluated for three of the shoes on vinyl tile with canola oil using human subjects. Differences in ACOF were significant across shoe outsole designs (p < .001). ACOF was correlated with geometrical and hardness parameters. Rate of slipping was lower for the highest ACOF shoe (p < .001). This information can be used to guide SR shoe selection and design.
... Several tread groove parameters have been shown to influence friction performance under contaminated conditions, including tread groove orientation, width, and depth [22]- [30]. For example, Li et al. [23]- [26] analyzed the optimal configuration of slip-resistant footwear to discern the impact of varying tread depths and widths under different conditions. Their findings emphasized that both tread groove width and tread groove depth were significant factors affecting J u s t A c c e p t e d the COF on the wet and water-detergent-contaminated floors. ...
... Pre-printing sample models for AtomStack Cambrian 3D printer(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) and SLA printer(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). ...
This study investigates the effect of various tread designs to enhance grip on both dry and wet friction, aiming to reduce slip and fall accidents, especially in slip-prone workplaces and among the elderly. The research involves analyzing frictional performance and deformation characteristics through dry and wet friction testing. Computer-aided design (CAD) software was used to create digital models of various tread patterns and two different additive manufacturing (AM) techniques : Fused Filament Fabrication (FFF) and Stereolithography (SLA) printing, were used to 3D print block samples with tread patterns, and the materials used were Thermoplastic Rubber (TPR) filament and photocurable elastomeric resin. A specialized friction testing machine was used to measure the friction force of the treads on a glass surface under dry and wet conditions. A high-speed camera recorded the treads' deformation and water drainage during testing. The results revealed the influence of tread pattern designs with two different rubber-like materials on friction and deformation, as well as performance on various contact surfaces.
... One of the known methods to control friction forces is designing friction surfaces by forming grooves. Generally, grooves on the surfaces of tires and sliding parts of machines are formed to reduce undesirable lubrication in wet conditions, which leads to a decrease in the friction coefficient and results in accidental slippage [8][9][10][11]. However, the dependence of friction force on grooves in dry conditions has not been established clearly. ...
... Generally, grooves on friction surfaces are designed to control lubrication properties in wet conditions. It is considered that the friction coefficient at the wet interface increases with the width and depth of the grooves, because they can eject more lubricant from the friction interface [8][9][10][11]. However, this study reveals that the groove size also affects friction in dry conditions. The static friction coefficient in dry conditions decreases with increases in groove width and depth. ...
This study numerically investigated the friction of viscoelastic objects with grooves. A 3D viscoelastic block with grooves on a rigid substrate is slowly pushed from the lateral side under uniform pressure on the top surface. The local friction force at the interface between the block and the substrate obeys Amontons’ law. Numerical results obtained using the finite element method reveal that the static friction coefficient decreases with increasing groove width and depth. The propagation of the precursor slip is observed before bulk sliding. Furthermore, bulk sliding occurs when the area of slow precursor slip reaches a critical value, which decreases with increasing groove size. A theoretical analysis based on a simplified model reveals that the static friction coefficient is related to the critical area of the precursor, which is determined by the instability of the precursor. A scaling law for the critical area is theoretically predicted, and it indicates that the decrease in the effective viscosity due to the formation of the grooves leads to a decrease in the static friction coefficient. The validity of the theoretical prediction is numerically confirmed.
Graphical Abstract
... Many studies have been conducted on the friction of rubber shoe soles under wet conditions [3][4][5][6][7][8][9][10][11][12][13][14]. The slip resistance of rubber shoe soles under wet conditions is affected by the geometric parameters of the outsole, such as the direction, width, and depth of tread grooves [3][4][5][6][7][8][9]; the length-width aspect ratio of tread blocks [10]; the apparent contact area and hardness of tread blocks [11,12]; and the surface topography [13,14]. ...
... Many studies have been conducted on the friction of rubber shoe soles under wet conditions [3][4][5][6][7][8][9][10][11][12][13][14]. The slip resistance of rubber shoe soles under wet conditions is affected by the geometric parameters of the outsole, such as the direction, width, and depth of tread grooves [3][4][5][6][7][8][9]; the length-width aspect ratio of tread blocks [10]; the apparent contact area and hardness of tread blocks [11,12]; and the surface topography [13,14]. In addition, the effects of wear-induced changes in these geometric parameters on slip resistance have been reported [15][16][17][18][19]. Hemler et al. [17] reported that the fluid force increased and the friction coefficient decreased with an increase in outsole wear [17,18]. ...
... One of the known methods to control friction forces is designing friction surfaces by forming grooves. Generally, grooves on the surfaces of tires and sliding parts of machines are formed to reduce undesirable lubrication in wet conditions, which leads to a decrease in the friction coefficient and results in accidental slippage [8][9][10][11]. However, the dependence of friction force on grooves in dry conditions has not been established clearly. ...
... Generally, grooves on friction surfaces are designed to control lubrication properties in wet conditions. It is considered that the friction coefficient at the wet interface increases with the width and depth of the grooves, because they can eject more lubricant from the friction interface [8][9][10][11]. However, this study reveals that the groove size also affects friction in dry conditions. The static friction coefficient in dry conditions decreases with increases in groove width and depth. ...
This study numerically investigated the friction of viscoelastic objects with grooves. A 3D viscoelastic block with grooves on a rigid substrate is slowly pushed from the lateral side under uniform pressure on the top surface. The local friction force at the interface between the block and the substrate obeys Amontons’ law. Numerical results obtained using the finite element method reveal that the static friction coefficient decreases with increasing groove width and depth. The propagation of the precursor slip is observed before bulk sliding. Furthermore, bulk sliding occurs when the area of slow precursor slip reaches a critical value, which decreases with increasing groove size. A theoretical analysis based on a simplified model reveals that the static friction coefficient is related to the critical area of the precursor, which is determined by the instability of the precursor. A scaling law for the critical area is theoretically predicted, and it indicates that the decrease in the effective viscosity due to the formation of the grooves leads to a decrease in the static friction coefficient. The validity of the theoretical prediction is numerically confirmed.
... The weight of the supportive footwear was 313 to 342 gm across the size range. The outersole had a 10 degree bevel into the heel region [33,34], grooves perpendicular to the sole (1.2 mm deep and 2.4 mm wide) across the heel surface area [35], and perpendicular grooves (5 mm deep and 12 mm wide) across the rest of the sole [36,37]. A textured insole was also constructed from 4 mm thick ethyl vinyl acetate (Shore A 25 [32]) with dome-shaped projections (3 mm high and 8 mm diameter, Shore A 85 [32]) placed across the forefoot in a 15 mm diamond pattern and along the lateral border, extending to the heel. ...
... Finally, as with our previous study [12], our assessment protocol did not include any tests specifically targeting slip resistance, so the slip resistant features of the outersole of the supportive footwear were not evaluated. However, the outersole design features have previously been shown to enhance slip resistance [33][34][35][36][37], and are likely to be superior to those of the minimalist footwear. ...
Background:
Footwear has been shown to influence balance and is an important consideration in relation to the prevention of falls. However, it remains unclear as to what type of footwear is most beneficial for balance in older people: sturdy, supportive footwear, or minimalist footwear to maximise plantar sensory input. The objectives of this study were therefore to compare standing balance and walking stability in older women wearing these two footwear styles, and to investigate participants' perceptions in relation to comfort, ease of use and fit.
Methods:
Older women (n = 20) aged 66 to 82 years (mean 73.4, SD 3.9) performed a series of laboratory tests of standing balance (eyes open and closed on floor and foam rubber mat, near tandem standing) and walking stability (treadmill, level and irregular surface) using a wearable sensor motion analysis system. Participants were tested wearing supportive footwear (incorporating design features to improve balance) and minimalist footwear. Perceptions of the footwear were documented using structured questionnaires.
Results:
There were no statistically significant differences in balance performance between the supportive and minimalist footwear. Participants perceived the supportive footwear to be significantly more attractive to self and others, easier to put on and off but heavier compared to the minimalist footwear. Overall comfort was similar between the footwear conditions, although the supportive footwear was reported to be significantly more comfortable in the heel, arch height, heel cup, heel width and forefoot width regions. Eighteen participants (90%) reported that they felt more stable in the supportive footwear and 17 (85%) reported that they would consider wearing them to reduce their risk of falling.
Conclusion:
Balance performance and walking stability were similar in supportive footwear designed to reduce the risk of falling and minimalist footwear, although participants preferred the supportive footwear in relation to aesthetics, ease of use, comfort and perceived stability. Prospective studies are now required to ascertain the longer-term advantages and disadvantages of these footwear styles on comfort and stability in older people.
Trial registration:
Australian New Zealand Clinical Trials Registry. ACTRN12622001257752p, 20/9/2022 (prospectively registered).
... Indeed, the degree of sole wear and tear is largely affected by workplacespecific conditions as exposure to chemical and mechanical factors, including abrasion, modifies the sole and floor surfaces, and, by the same token, the coefficient of friction and traction. While walking on rough surfaces may increase the coefficient of friction, smooth flooring may polish the soles, substantially decreasing it over time [18]. ...
... These results are consistent with papers by Leclercq et al. [8] and Grönqvist [16]. Way et al. [18], who examined the natural use of footwear on oily surfaces for more than a year, reported that friction usually changed throughout the period of use. In the case of PU, friction improved after a short period of time. ...
This work aimed to study the end of service life of soles of protective footwear resistant to selected mechanical factors and mineral oil. Three sole variants were examined; made from poly(ethylene-co-vinyl acetate) (EVA), poly(vinyl chloride) (PVC) and polyurethane (PU), currently widely used in all-rubber protective footwear. The preliminary study focused on the abrasion resistance and bending strength of the three sole materials after different times of exposure to mineral oil. Changes in density and hardness of the examined materials were evaluated following exposure to cyclical factors. Statistical analysis was performed to identify significant differences between the three types of polymers in terms of abrasion resistance, density and hardness following exposure to mineral oil for three different periods. Surface morphology of the sole materials was examined by means of scanning electron microscopy. The presented studies elucidate the effects of mineral oil on the basic mechanical parameters of all-rubber footwear soles.
... The risks associated with slipping and falling are related to the material surface of footwear/floor surface, contamination condition and the geometric design of the sole (Li et al., 2006). Shoe soles of various tread design are very common. ...
... Tread pattern of the shoe affects friction, especially, under liquid-contaminated conditions. Verification of the effects of tread groove depth is significant in assisting designers in designing proper footwear for workers exposed to slippery conditions (Li et al., 2006). Sole material samples, in this exploit, are prepared in stripes to fit the testing equipment. ...
Data from the Accident Centre of the Korle-Bu Teaching Hospital, Accra, Ghana, indicate that between January 2016 and December 2017, there were 19.7% injuries due to falls with 13.7% resulting in deaths. These injuries and deaths may be due to floor surface finishes that have the tendency to cause slip fall and also exacerbated by the floor condition and footwear in contact. In this exploratory studies, tests are conducted on six selected floor surfaces and five footwear soles under dry, wed and dust or oil contaminated conditions for their slip potentials. The tests were performed with pendulum test apparatus. The footwear sole material surfaces that show better performance are leather, commando and rubber. They have Pendulum Test Value (PTV) of about 30, indicating moderate risk in slip fall and 1 in 20,000 probability of fall. Dust contamination as applied to other floor surfaces show commando sole performing above 35 PTV with all floor surfaces. Porcelain tiles, when wet, are able to maintain above low slip potential with leather, commando and rubber camp soles but with high slip probability with others. Also, Porcelain tiles have high slip probability when contaminated with dust. From the findings, it is clear that slip fall can occur if the foot wear is not appropriate with the surface conditions. In developing countries, selecting the appropriate slip-resistant footwear is severely challenged, because of non-existent of data. Further investigation is needed for various footwear soles available leading to developing database for public education in avoiding slip falls.
... In Japan, slip and fall accidents accounted for 33% of all occupational injuries, and the annual number of fatalities had exceeded 4000 over the last decade [3]. The conditions of stepping friction pair consisting of outsole and ground have a significant influence on their available traction during walking, such as material and pattern shape of the outsole [4][5][6][7][8], shoe-floor-contaminant conditions [9][10][11][12], material and shape of the pavement [9,10,13,14]. In general, slipping occurs when the available traction provided by a shoe-surface combination is less than the traction required to perform a given action [15][16][17]. ...
... In Japan, slip and fall accidents accounted for 33% of all occupational injuries, and the annual number of fatalities had exceeded 4000 over the last decade [3]. The conditions of stepping friction pair consisting of outsole and ground have a significant influence on their available traction during walking, such as material and pattern shape of the outsole [4][5][6][7][8], shoe-floor-contaminant conditions [9][10][11][12], material and shape of the pavement [9,10,13,14]. In general, slipping occurs when the available traction provided by a shoe-surface combination is less than the traction required to perform a given action [15][16][17]. ...
Abstract There are various walking pavements in daily life. Slip accidents will happen if required friction for safe walking is greater than available friction between the foot and ground surface. Existing researches mostly focus on horizontal or slope pavements, whereas the cross‐slope walkways are less. A self‐developed gait friction test platform was used to test friction, distribution of plantar pressure and spatiotemporal parameters of human walking under cross‐slope condition. With the increase of cross‐slope angles, the mediolateral friction increases (R 2 = 0.972, P
... The frictional performance of slip resistant footwear has been extensively studied experimentally [4][5][6][7][8][9]. Two studies by Li and Chen (2004) and Li and Chin (2005), investigated how certain tread design parameters affect friction on contaminated surfaces using bespoke tread patterns [4,5]. ...
... Defining k c in terms of the loaded area during compression (length l multiplied by width w), the undeformed block thickness (t) and the compression modulus (E c ) gives Equation (6). ...
Within this paper, a three-dimensional finite element (FE) model of a uniformly loaded, single rubber block, is described and run using loading conditions replicative of a standard slip resistant footwear test. The FE model considers rubber hyperelastic and viscoelastic material properties, obtained using dynamic mechanical analysis. The performance of the FE model was evaluated through analytical compression analysis and experimental contact area testing. The effect of tread grooves was investigated with relation to slip-resistance during walking. Analysis and discussion are provided of the tread model's sliding contact areas, contact pressure, stress, and front edge mechanics.
... Little attention was exerted to measure the friction coefficient of rubber footwear soles sliding against dry and contaminated brake pedal pads. The majority of previous researches studied the frictional behaviour of the sliding of bare foot as well as foot wear soles against different types of floorings [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . Soft material like rubber tends to a higher effective contact area and more pronounced microscopic deformations when mechanically interacting with the surface asperities of a rigid material, greater friction coefficients can be expected for rubber than for plastic [1] . ...
... The friction decrease may be due to the increased ability of the tread to form hydrodynamic wedge as the tread width increased. Tread groove designs are helpful in facilitating contact between the shoe sole and floor on liquid contaminated surface [9][10][11][12] . The effectiveness of a tread groove design depends on the contaminant, footwear material and floor. ...
The present work discusses the effect of the treads width of the rubber brake pedal pads on the friction coefficient. Measurement of friction coefficient generated by bare foot and rubber footwear soles sliding against the brake pedal pads of different treads width in dry, sand contaminated, water and oil lubricated conditions is discussed. Experiments of the sliding of bare foot against the rubber pedal pad showed that friction coefficient of dry sliding significantly decreased with increasing tread width. The sliding direction has no effect on the friction coefficient for the tested pads. In the presence of sand particles separating the two contact surfaces, load had no influence on friction coefficient. Friction coefficient slightly decreased with increasing tread width. For water wetted pedal pad, friction coefficient displayed higher values than that observed for the condition of presence of sand particles. Friction values showed consistent trend with increasing the tread width. Friction displayed by oil lubricated pedal pads was the lowest and the sliding condition could be considered as unsafe.
... Low available friction between the shoe and flooring increases the risk of slips and subsequent falls [4,5]. Shoe tread design characteristics such as tread depth [6], tread width [7], the size of the region without tread [8], and the available contact area between shoe and flooring [9] influence the available friction at the shoe-floor interface and therefore affect the risk of slips and falls [6][7][8]10]. These properties change across a shoe's lifetime as tread becomes worn. ...
... Low available friction between the shoe and flooring increases the risk of slips and subsequent falls [4,5]. Shoe tread design characteristics such as tread depth [6], tread width [7], the size of the region without tread [8], and the available contact area between shoe and flooring [9] influence the available friction at the shoe-floor interface and therefore affect the risk of slips and falls [6][7][8]10]. These properties change across a shoe's lifetime as tread becomes worn. ...
Worn shoes increase the risk of slip-and-fall accidents. Few research efforts have attempted to predict the progression of shoe wear. This study presents a computational modeling framework that simulates wear progression in footwear outsoles based on finite element analysis and Archard's equation for wear. The results of the computational model were qualitatively and quantitatively compared with experimental results from shoes subjected to an accelerated wear protocol. Key variables of interest were the order in which individual tread blocks were worn and the size of the worn region. The order in which shoe treads became completely worn were strongly correlated between the model and experiment (rs > 0.74, p < 0.005 for all of the shoes). The ability of the model to predict the size of the worn region varied across the shoe designs. Findings demonstrate the capability of the computational modeling methodology to provide realistic predictions of shoe wear progression. This model represents a promising first step to developing a model that can guide footwear replacement programs and footwear design with durable slip-resistance.
... Ura et al. [4] studied temperature's influence on outsole slip resistance. Besides, there have been several studies [5][6][7][8] focused on the effect of outsole pattern. Li et al. [6] investigated the effect of depth of outsole pattern on slip resistance. ...
... Besides, there have been several studies [5][6][7][8] focused on the effect of outsole pattern. Li et al. [6] investigated the effect of depth of outsole pattern on slip resistance. Yamaguchi et al. [7] and Shao-Xun et al. [8] studied the relationship of different contact surfaces and the outsole pattern. ...
Finite element analysis (FEA) has been widely used in engineering and construction in simulating forces and interactions and its application in footwear have become quite ripe by being researched for over 30 years. The aim of this study was to investigate the slip resistance of the outsole to learn (1) the feasibility of FEA in the test of outsole slip resistance (2) frictional interactions between outsole and contact surface by experiment test and finite element analysis. A static friction tester was used for static slip resistance test and a SATRA STM 603 slip resistance tester was used for dynamic slip resistance test. Outcome showed that value of SCoF was a little bit higher than that of DCoF both in ET and FEA, and value of coefficients obtained in ET was higher. With the increase of COF value, the displacement of outsole decreased while stress of the outsole increased. In conclusion, FEA application is feasible in footwear resistance testing. Stability of the outsole with superior slip resistance is good in both longitudinal and transverse direction. During walking, it has a strong resistance to the slipping tendency to prevent tumble and sprain.
... However, the medical and food industries often cannot increase surface roughness due to hygiene requirements [17,18]. Thus, efforts to optimize footwear slip resistance have included improvements in sole patterns [19][20][21][22][23], hardness [24][25][26] and materials [21,27,28]. Footwear soles, typically made from viscoelastic elastomers [9], have complex material properties that affect slip resistance [29]. ...
... The anti-slip properties of the shoe outsole can be significantly affected by the design of the thread pattern. Parameters such as thread depth or width, their orientation, and density can significantly affect the COF values [107,108]. ...
The most important role of footwear is to ensure safe, functional walking, and foot protection. For the proper functionality of not only the work shoes, the anti-slip behavior of the shoe under various conditions and environments plays an important role in the prevention of slips, trips, falls, and consequent injuries. This article is intended to review the current understanding of the frictional mechanisms between shoe outsoles and various counterfaces that impact the evaluation of outsole slipperiness. Current research focuses on the mechanisms driving outsole friction on different ground surfaces or the definition and description of parameters that influence outsole friction. Subsequently, the review discusses the effect of various surface contaminants on footwear friction. Lastly, challenges and outlooks in the field of footwear outsoles are briefly mentioned.
... Previous work has shown that footwear friction is affected by the dimension and distribution of drainage grooves. For instance, studies conducted by Li et al. (2006), Li and Chin (2005a), and Chen (2004, 2005) explored the influence of tread groove width, depth, and orientation on COF values. They used a slip-meter to test different footwear pads and found that tread grooves that were wider, deeper, and perpendicular to the friction measurement yielded higher COF values on water and water-detergent conditions but were negligible on oil most likely due to the high viscosity. ...
... In these slipevents,the available coefficient of friction decreases between the two surfaces due to shoe tread design [52], roughness [53] and hardness [54] parameter between two interacting surfaces [32,33].Shoe sole are usually made up of viscoelastic rubber like materials, which arecapableof redistributingpressure under the shoe to reduce the pressure at local points [55]. The viscoelastic property of the shoe sole also attenuate the shock during the shoe impact on the floor [56]. ...
Domain first development of Robotic Slip Simulator to measure shoe-floor-contaminant friction parameters and validation of results by Computer models. Study demonstrated that during the human slip phenomenon, around half of the human weight is supported by contaminant when there is lack shoe thread. The finding is important for designing of shoe thread in Shoe Industry and tire thread design in Tire industry.
... Several studies have reported that increasing fluid pressures over the un-treaded or worn region resulted in decreased traction. In another study by Li et al. [24], the effect of varying tread parameters on the ACOF was studied in several slipping conditions, and significant differences were reported in the ACOF outcomes. Quantifying fluid pressure and the capability of an outsole to disperse the excess fluid require additional attachments to the slip testers and are dependent on the flow losses and sensitivity of the sensor, which can hamper the results. ...
Accidental injuries due to slips and falls are considered serious threats to public safety. Sufficient friction at the footwear and flooring interface is essential to reduce slip-related risks. The presence of slippery fluidic contaminants, such as water, further reduces friction and increases the risks of slip-related accidents drastically. While the effect of floorings and contaminants on footwear traction has been measured extensively across a variety of footwear designs, only a few studies have explored the science of the outsole design and its role in providing sufficient traction. In this work, the tread design of a commonly encountered outsole pattern, i.e., with vertically oriented tread channels, was parametrically altered across its width and gap. Based on the impressions of an original footwear design, nine outsoles were fabricated. The induced fluid pressures, mass flow rates, and traction were quantified by using a computational fluid dynamics (CFD) framework and through slip testing experiments. Outsoles that had wide treads with small gaps decreased the overall slipping risk on dry floorings. As compared to the tread area, tread gaps were found to be a dominating parameter in providing adequate shoe–floor traction in wet slipping conditions. The methods, including the outcomes presented in this work, are anticipated to advance the understanding of the science behind footwear friction and help footwear manufacturers optimize outsole designs to reduce slip and fall risks.
... We hypothesize that small changes in the depth and layout of these different materials can have a large impact on overall slip resistance performance. Previous work on the impact of tread design have established key principles (Li et al., 2006;Liu et al., 2013), but these design principles have never been tested with footwear with composite material on icy surfaces. Therefore, we propose to investigate the interaction of four tread pattern features on slip resistance of footwear on ice made of a combination of composite and conventional materials. ...
The ultimate goal of this research is to prevent fall-related injuries for workers exposed to outdoor winter conditions through the development of slip-resistant footwear based on novel composite materials and optimization of tread pattern design to retain its properties over extended use. This research will answer the following research question: how do tread pattern design features (tread depth, shape, orientation, and surface area) effect the slip-resistance of footwear with outsoles made up of a combination of novel composite and conventional materials? The objective of this project is to identify the relationship between tread pattern and slip-resistance on icy surfaces for footwear based on novel composite materials.
... Currently, some companies provide tread gauges for individuals to test their shoes (ShoesForCrews, 2019), based on the presumed relationship between tread depth and ACOF (Li & Chen, 2005;Li et al., 2006). Additionally, Beschorner et al. (2020) recommended comparing the size of the continuous worn region on the shoe outsole to the size of a AA or AAA battery to determine if worn shoes should be replaced. ...
Occupational ApplicationsWe investigated the association between shoe wear rate and several metrics describing an individual's spatiotemporal gait characteristics (cadence, step length, and preferred walking speed). No associations were found, indicating that alternative metrics should be investigated to predict the individualized rate at which workers wear down shoe tread.Technical AbstractBackground: Shoe wear has been associated with increased slips and falls in the workplace. People wear down shoe tread at different rates; therefore, individualized shoe replacement timelines could improve resource targeting for organizations that use time as a basis for shoe replacement. Previous work has found that the shoe-floor kinetics, such as the friction requirements of walking, correlate with shoe wear rate. The use of easily measured metrics such as cadence, step length, or preferred walking speed to predict wear has not yet been investigated despite their relationship with friction requirements.
Purpose:
This study seeks to determine the association between shoe wear rate and gait spatiotemporal characteristics.
Methods:
Thirteen participants completed a longitudinal shoe wear study that consisted of a gait assessment followed by prolonged shoe wear in two pairs of slip resistant shoes. The gait assessment was comprised of dry level-ground walking trials; kinematic and kinetic data were collected through optical motion capture and force plates. The participants' mean cadence, step length, and preferred walking speed were calculated. The participants then wore their shoes at work; the shoe wear rate was determined by measuring the periodic volumetric tread loss during this wear-at-work portion of the study.
Results:
Three linear regression models found no significant association between the chosen gait metrics and the shoe wear rate.
Conclusions:
The lack of an association between the spatiotemporal gait characteristics and shoe wear rate indicates that these factors may not explain the differences in wear rate between participants. This negative finding suggests that other measures such as the required coefficient of friction are better for individualizing footwear replacement guidelines.
... Specifically, multiple mechanisms are relevant to friction performance, which can lead to nonlinear responses to design changes. For example, increasing the height of tread channels can be beneficial or detrimental depending on the operating conditions [18,24,39]. Thus, the effects of design changes are context dependent. ...
New technologies that enhance our understanding of shoe-floor mechanics have opened opportunities to address slip and fall accidents. Footwear has been identified as one critical factor capable of reducing an individual’s risk. Thus, this moment is ripe for reducing the burden of slips, trips, and fall events. New technology can be broadly categorized into: 1) new modeling methods for predicting footwear friction performance; 2) new experimental methods for characterizing friction mechanics; and 3) new human-centred methods for characterizing interactions between the footwear and the user. These emerging technologies have the potential to elevate friction and traction performance of footwear and enhance the information available to ergonomics professionals to match appropriate footwear to applications. However, the deployment of these technologies is only beginning to guide footwear design and consumer behaviors. Thus, the footwear manufacturers’ perspective in implementing new technology will also be presented. In this workshop, we will A) present information regarding emerging technologies in addition to their benefits and limitations; and B) survey the audience, disaggregated by industry sector, to obtain new data on the potential for these technologies to be accepted and implemented by professionals.
... Moreover, the attached kirigami grips may change the gait of the study participants and affect the braking forces. Therefore, we can make outsoles that cover the entire sole and consist of two portions to achieve further friction improvement over all of the stages of stance: (1) a top portion consisting of the kirigami pattern made of textured sheets to increase the friction in the push-off stage and (2) a bottom portion (heel region) made of dimpled or tread groove patterns (no kirigami pattern) to generate higher braking forces and increase friction in the weight-acceptance phase and finally reduce the risk of slip [44][45][46] . ...
Falls and subsequent complications are major contributors to morbidity and mortality, especially in older adults. Here, by taking inspiration from claws and scales found in nature, we show that buckling kirigami structures applied to footwear outsoles generate higher friction forces in the forefoot and transversally to the direction of movement. We identified optimal kirigami designs capable of modulating friction for a range of surfaces, including ice, by evaluating the performance of the dynamic kirigami outsoles through numerical simulations and in vitro friction testing, as well as via human-gait force-plate measurements. We anticipate that lightweight kirigami metasurfaces applied to footwear outsoles could help mitigate the risk of slips and falls in a range of environments.
... Shoe friction performance is dependent on the outsole geometry. Previous studies have identified tread parameters (size, orientation, depth, contact area) that affect traction performance [7][8][9][10]. The effects of material thickness ratios, resultant rubber tread block stiffness, and surface roughness on the friction coefficient have also been explored [10,11]. ...
Slips and falls are a leading cause of injuries in the workplace. The risk of slipping increases as shoe tread wears. Knowledge of the mechanics relating shoe wear to slip risk is needed to develop fall-prevention strategies. This research applies a rectangular, tapered-wedge bearing solution to worn shoes and compares the results to experimentally measured under-shoe fluid pressure results. Changes in the size of the shoe outsole worn region and fluid dispersion capabilities were recorded for four, slip-resistant shoes which were systematically abraded. The film thickness predicted by the solution correlated well with the measured force supported by the fluid. The results provide support that the tapered-wedge solution can be used to assess slip risk in worn shoes.
... Variations in tread design (i.e. tread depth and width) have been shown to affect ACOF (Li and Chen, 2004;Li et al., 2006;Yamaguchi et al., 2017). Channels in shoe tread provide fluid dispersion pathways to reduce hydrodynamic pressures (Strandberg, 1985;Tisserand, 1985) and have been shown to reduce the risk of slipping compared to shoes without such channels . ...
Shoe wear is known to increase slipping risk, but few studies have systematically studied this relationship. This study investigated the impact of progressive shoe wear on the available coefficient of friction (ACOF) and under-shoe fluid dynamics. Five different slip-resistant shoes were progressively worn using an accelerated, abrasive, wear protocol. The ACOF and fluid forces (the load supported by the fluid) were measured as shoes were slipped across a surface contaminated with a diluted glycerol solution. As the shoes became worn, an initial increase in ACOF was followed by a steady decrease. Low fluid forces were observed prior to wear followed by increased fluid forces as the worn region became larger. Results suggest that traction performance decreases particularly when the heel region without tread exceeds a size of 800 mm2. This study supports the concept of developing shoe replacement guidelines based upon the size of the worn region to reduce occupational slips.
... Rough surfaces are inherent to everyday life, and on the macroscopic scale can range from tectonic plates [1] to the soles of running shoes [2]. Despite many surfaces seeming smooth, at the microscopic scale every surface has some level of roughness [3,4], which leads to phenomena that are often not obvious as an extension from the macroscopic world. ...
A colloidal particle is driven across a temporally oscillating one-dimensional optical potential energy landscape and its particle motion is analysed. Different modes of dynamic mode locking are observed and are confirmed with the use of phase portraits. The effect of the oscillation frequency on the mode locked step width is addressed and the results are discussed in light of a high-frequency theory and compared to simulations. Furthermore, the influence of the coupling between the particle and the optical landscape on mode locking is probed by increasing the maximum depth of the optical landscape. Stronger coupling is seen to increase the width of mode locked steps. Finally, transport across the temporally oscillating landscape is studied by measuring the effective diffusion coefficient of a mobile particle, which is seen to be highly sensitive to the driving velocity and mode locking.
... A rubber block with a rough/smooth surface area ratio of 50:50 achieved a static friction coefficient value of around 0.5 and a dynamic friction coefficient value greater than 0.5. Using a Brungraber Mark II slip meter, Li et al. [10][11][12] investigated the influence of tread patterns with groove orientations of 0°, 45°, and 90°to the sliding direction on the friction coefficient. A rubber block with tread grooves perpendicular to the sliding direction showed the highest friction coefficient under lubricated conditions. ...
In this study, we investigate the frictional behavior of an ethylene vinyl acetate copolymer (EVA) foam/styrene butadiene rubber (SBR) laminated block using a dead-weight-type tribometer to identify the design guidelines for shoe tread patterns to provide variable friction control. The friction coefficient was highest when the ratio of the EVA foam thickness with respect to the total block thickness was high (i.e., 0.2–0.8) because of the increased contact area. Further, the friction coefficient of the laminated block specimen increased with the normalized parameter, which is the ratio of shear deformation and bending deformation in the bulk material. These results indicate that increasing the shear deformation component prevents the detachment of the specimen's trailing edge and maintains the contact area at the specimen–floor interface, resulting in increased friction coefficients. Our observations are expected to contribute to a detailed understanding of how to control the friction of the resin-foam/rubber-laminated block materials.
... To better understand the complexities associated with friction measurements, Chang et al. (2003) suggested testing shoes on realistic floors and contaminant conditions. Current footwear traction testing reports are typically limited to a few flooring and contaminant conditions, leading to questions about the footwear's performance on other floor-contaminant conditions (Blanchette & Powers, 2015;Li, Wu, & Lin, 2006). Increasing the number of shoes, contaminants, or floorings, can greatly expand the number of test conditions. ...
Background:
To prevent slip and fall events at the workplace, mechanical slip testing is conducted on shoes. Such experiments may involve redundant testing across floorings and contaminant conditions, causing wasted time and effort.
Purpose:
Quantify the correlations between shoe traction across different contaminant-flooring conditions to reduce redundant slip testing efforts.
Methods:
The available coefficient-of-friction (ACOF) was quantified for 17 shoes across five floorings and three contaminant conditions. Redundant testing conditions were identified when the shoe ACOF values for one floor-contaminant condition were highly correlated with a second floor-contaminant condition.
Results:
High correlations were observed among quarry floorings across different contaminants and among vinyl (composite tile) floorings with the same contaminant. However, vinyl floorings exhibited low correlations with quarry floorings. Low correlations were also observed across contaminants within vinyl tiles.
Conclusions:
This study was able to determine the generalizability of traction performance of shoes across vinyl and quarry floorings. This information is anticipated to reduce redundant traction testing of shoes across vinyl and quarry floorings.
... Another challenging concern is about controlling and maintaining texture conditions of the floor surfaces because they seem to be continuously modified by abundant reasons such as maturing, erosion, fouling, and sustaining [1,6]. Accordingly, gradual wear and damage progress are inevitable and may significantly impact on traction functions [7][8][9][10]. is issue was reported by several studies in the views of profile roughness, textures, and friction properties [11][12][13][14][15][16][17]. However, inclusive investigates on flooring wear behaviours and effects on pedestrian fall safety assessments are scared to find in the literature [18][19][20][21]. ...
The recent literature identified that certain types of smooth floors and flooring materials showed good slip-resistance performance under moderately contaminated situations such as water wet and soapsuds-covered conditions. However, topographic structures of such flat floor/walkway surfaces are significantly changed by wear and tear developments with continuous ambulation. A number of reasons seem to be involved in flooring wear developments, but such changes may result in substantial losses of slip resistance (or traction) functions. Even though the importance of this issue is wide, it is scarce to find any systematic investigations on tribophysical characteristics of smooth floors (<10 µ m in Ra roughness) and their wear impacts on traction performance. Moreover, it is difficult to find studies on wear progress of floors and its impacts on pedestrian fall safety assessments. This study focuses on exploring wear activities of smooth resilient floors and disclosing wear consequences on traction properties. To measure slip-resistance features and investigate wear advances of smooth resilient floors, dynamic friction tests were carried out amongst purposely arranged 4 flat specimens (polymethyl methacrylate: PMMA) and 3 shoes. Wear formations and progressions of the PMMA surfaces were methodically evaluated by observing surface profiles during the tests. The test outcomes evidently presented that initial surface features of the PMMA specimens were significantly modified by primary-, secondary-, and shared-wear mechanisms and significantly influenced traction performance. This study may have design applications for the safety enhancements of smooth floors/footpaths to preclude pedestrian fall incidents.
Heavy-duty legged robots have played an important role in material transportation, planet exploration, and other fields due to their unique advantages in complex and harsh terrain environments. The instability phenomenon of the heavy-duty legged robots often arises during the dynamic interactions between the supporting feet and the intricate terrains, which significantly impact the ability of the heavy-duty legged robots to move rapidly and accomplish tasks. Therefore, it is necessary to assess the mechanical behavior of foot–terrain interactions for the heavy-duty legged robots. In order to achieve the above goal, a systematic literature review methodology is employed to examine recent technical scientific publications, aiming to identify both current and prospective research fields. The characteristics of supporting feet for different heavy-duty legged robots are compared and analyzed. The foot–terrain mechanical models of the heavy-duty legged robots are discussed. The problems that need further research are summarized and presented, which is conducive to further deepening and expanding the research on the mechanical behavior of foot–terrain interactions for heavy-duty legged robots.
Computer technology influences the capability to enhance the functionality of manufacturing and product design technologies. Innovations in computational design and digital manufacturing empower designers and manufacturers to create novel representations and algorithms for designing, analyzing, and planning the production of highly complicated products achievable through state-of-the-art technology. Various principles, including computational physics, geometric reasoning, and automated spatial planning, enable engineers to generate entirely new categories of products in the footwear industry. This study aims to review the methods and tools that have been published in the literature for the last twenty years, and provide a better understanding of the parameters, tools, and controls that contribute to the design and manufacturing processes of shoes. The main focus is on highlighting the product design-related trends within the footwear industry. A structured framework becomes apparent in the literature through the grouping and presentation of information. This framework facilitates drawing conclusions about the trends and existing needs derived from in-depth research in the field of footwear. Additionally, it reveals the upcoming methods and tools that will contribute to the enhancement and development of this emerging and promising industry sector. In conclusion, the categorization limitation within the footwear industry could serve as the foundation for exploring key areas to be analyzed further in other industries, for instance, in furniture, clothing, and packaging.
Slipping is a major cause of occupational accidents and numerous footwear factors and features, as well as the testing conditions, affects a shoe's ability to resist slipping. The aim of this study was to compare slip resistance certification data from five certified shoes with measurements performed on a mechanical test setup in accordance with the ISO 20347:2012 standard, as well as determining their performance in a biofidelic setup that resembles the biomechanics of slipping. Certification data attributed Shoe #3 with the highest slip resistance, and our mechanical assessment of the same footwear models showed that Shoe #2 had the higher slip resistance and was superior under more biofidelic testing parameters. Based on our mechanical evaluations, specific engineering considerations such as an increase in both the heel beveling and the midsole thickness can advantageously enhance slip resistance. Further investigation in a clinical setting will provide insights on how these engineered footwear adjustments could enhance friction and ultimately enhance occupational safety.
This chapter provides information on the effect of the change in tread pattern of the footwear outsoles on the slip risk probability. The various parameters such as tread contact region and shore A hardness of the footwear and its effect on the slip probability especially in contaminated flooring scenarios were particularly highlighted. The recent study involving the vertical tread patterns that are also commonly found in the formal footwear was discussed. The process of replicating and fabrication of the vertical polyurethane-based outsoles was specifically elaborated. The process of slip testing experiments utilizing the biofidelic slip tester was also highlighted. The variation in the frictional performance of the developed vertical footwear tread patterns when slip testing was performed in dry and wet condition was specifically focused upon in this chapter. The effect of tread width and tread gap on the frictional performance of the vertical outsoles in dry and wet slip testing conditions was highlighted. The parameters mainly tread width and tread gap were ultimately found to be the main footwear tread design factors in manufacturing slip resistant footwear.
Slips and falls on ice are common causes of injury in the winter and can result in economic loss. Using slip resistant winter footwear is a key factor in reducing the risk of slips and eventually falls. In this study, we develop a model that classifies footwear outsoles based on how slip resistant they are on icy surfaces. Our dataset consisted of outsole images of 89 winter footwear samples that were previously tested and rated with a human-centred protocol called the Maximum Achievable Angle (MAA). We applied a transfer learning technique where the best classification model used the DenseNet169 pre-trained model and obtained an accuracy and F1-score of 0.93 ± 0.01 and 0.73 ± 0.03, respectively. Our results suggest that the proposed model was able to properly identify high and low slip resistance quality tread patterns. Our findings confirmed that a footwear’s tread pattern has a direct impact on its slip resistance. The proposed model will help footwear manufacturers to improve their workflow and increase product quality which can ultimately decrease the events of slips and falls.
Background
Footwear has been shown to influence balance and is an important consideration in relation to the prevention of falls. However, it remains unclear as to what type of footwear is most beneficial for balance in older people: sturdy, supportive footwear, or minimalist footwear to maximise plantar sensory input. The objectives of this study were therefore to compare standing balance and walking stability in older women wearing these two footwear styles, and to investigate participants’ perceptions in relation to comfort, ease of use and fit.
Methods
Older women (n = 20) aged 66 to 82 years (mean 73.4, SD 3.9) performed a series of laboratory tests of standing balance (eyes open and closed on floor and foam rubber mat, near tandem standing) and walking stability (treadmill, level and irregular surface) using a wearable sensor motion analysis system. Participants were tested wearing supportive footwear (incorporating design features to improve balance) and minimalist footwear. Perceptions of the footwear were documented using structured questionnaires.
Results
There were no statistically significant differences in balance performance between the supportive and minimalist footwear. However, trends were observed which indicated that standing balance was better in the minimalist footwear, while walking stability was better in the supportive footwear. Participants perceived the supportive footwear to be significantly more attractive to self and others, easier to put on and off but heavier compared to the minimalist footwear. Overall comfort was similar between the footwear conditions, although the supportive footwear was reported to be significantly more comfortable in the heel, arch height, heel cup, heel width and forefoot width regions. Eighteen participants (90%) reported that they felt more stable in the supportive footwear and 17 (85%) reported that they would consider wearing them to reduce their risk of falling.
Conclusion
Balance performance and walking stability were similar in supportive footwear designed to reduce the risk of falling and minimalist footwear, although participants preferred the supportive footwear in relation to aesthetics, ease of use, comfort and perceived stability. Prospective studies are now required to ascertain the longer-term advantages and disadvantages of these footwear styles on comfort and stability in older people.
Trial registration: Australian New Zeland Clinical Trials Registry. ACTRN12622001257752p, 20/9/2022 (prospectively registered). https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=384670&isReview=true
Introduction:
Annually, approximately 250,000 people climb Mount Fuji in Japan. Nonetheless, only few studies have examined the prevalence of falls and related factors on Mount Fuji.
Methods:
We conducted a questionnaire survey of 1061 participants (703 men and 358 women) who had climbed Mount Fuji. The following information was collected: age, height, body weight, luggage weight, experience on Mount Fuji, experience on other mountains, presence or absence of a tour guide, single-day climber or overnight-stay lodger, information on the downhill trail (volcanic gravel, long distance, and the risk of falls), presence or absence of trekking poles, shoe type, shoe sole condition, and fatigue feeling.
Results:
The fall rate in women (174/358; 49%) was greater than that in men (246/703; 35%). A prediction model using multiple logistic regression (no fall, 0; fall, 1) indicated that the following factors decreased the risk of falls: male sex, younger age, previous experience on Mount Fuji, having information about long-distance downhill trails, wearing hiking shoes or mountaineering boots rather than other types of shoes (eg, running shoes, sneakers) or worn-out shoes, and not feeling fatigued. Additionally, the following factors may decrease the risk of falls in women only: experience hiking on any other mountains, not being part of a guided tour, and using trekking poles.
Conclusions:
Women had a higher risk of falls on Mount Fuji than men. Specifically, having less experience on any other mountains, being part of a guided tour, and nonuse of trekking poles may relate to higher risks of falls in women. These results suggest that different precautionary measures for men and women are useful.
Many important problems in elasto-hydrodynamic lubrication arise when one of the contacting bodies is elastically soft. An example is the squeezing of a thin liquid film between a rigid sphere/cylinder and a soft elastic substrate, in which the sphere may not be sliding and be subjected only to normal loads (stationary contact), or it can be sheared at the same time and undergo steady or non-steady sliding. These problems are notoriously difficult to solve for soft solids under large loads and thin lubricant films. For this reason, indentation and sliding problems have usually been analyzed separately, and solutions for transient sliding problems are few. Here we develop a numerical method that avoids difficult-to-converge iterative methods and is able to solve both normal indentation and/or transient sliding lubrication problems. The scheme is fully automatic, stable, and efficient and requires only a linear matrix equation to be solved at every time step. We present solutions of two transient sliding problems: in the first of which, a rigid sphere undergoes transient normal lubricated contact followed by transient sliding on an elastic half space. In the second, a rigid cylinder undergoes transient lubricated sliding on an elastic foundation.
The friction between a glass plate and rubber blocks with different end-face corner radii was investigated. Under dry conditions, rubber blocks with a large end-face corner radius (r = 0.83 mm) exhibited greater friction coefficients than those with a small end-face corner radius (r = 0.11 mm). Conversely, friction coefficients for r = 0.11 mm were greater than those for r = 0.83 mm under lubrication conditions. Further, the friction coefficients for r = 0.11 mm increased as the sliding velocity and lubricant viscosity increased owing to the formation of the fluid-free gap at the contact interface.
This chapter study focuses on exploring wear activities of smooth resilient floors and disclosing wear consequences on traction properties. To measure slip resistance features and investigate wear advances of smooth resilient floors, dynamic friction tests are carried out amongst purposely arranged four flat specimens (polymethyl methacrylate: PMMA) and three shoes. Wear formations and progressions of the PMMA surfaces are methodically evaluated by observing surface finishes quantitatively and qualitatively during the tests. The test outcomes evidently present that initial surface features of the PMMA specimens were significantly modified by primary-, secondary-, and shared-wear mechanisms and considerably influenced traction performances. Explored concepts, ideas, and findings from this chapter may have design applications for the safety enhancements of smooth floors/footpaths to preclude pedestrian fall incidents.
Knowledge limitations, ambiguities, and indecisiveness at the modeling stage of a risk assessment model can tend to induce structural errors in the model. Operational logic misuse and fuzzy values misrepresentation are a major source of structural error that can overestimate or underestimate the overall risk assessment values. This paper proposes generic risk assessment models to overcome reliability limitations in risk assessment of concurrent events. An enhanced rotational fuzzy model for quantifying possible subjective risk values is proposed to be used along with Fuzzy Fault Tree Analysis (FFTA) model for risk assessment. A fault tree is built upon a generic but inclusive risk breakdown structure, which can help avoid assessment underestimation by providing a structure for deducting influential events from the top risk event under assessment. Adequate operational logic gates are suggested to avoid assessment overestimation related to accumulating the effect of dependent, redundant, and non-concurrent risks, and ignoring the effectiveness of the existing safety precautions and measures that may reduce or eliminate risks. The proposed FFTA model can be used as a prognostic risk assessment tool to combine the influence of concurrent risks from basic events at the bottom of the tree to the top risk event defined by risk assessor. The FFTA risk assessment model is applied to five different sample cases, with a case of graphical and numerical details, to illustrate the general applicability on diverse domains, namely, truss failure during placement risk, slipping risk, frozen pipe burst risk, virus spread risk, and project completion delay risk.
Footwear outsole design is an important factor for shoe-floor friction and for preventing slipping. Shoes with small, uniformly-separated tread blocks (often included on slip-resistant shoes) have decreased slip risk due to their increased friction and better under-shoe fluid drainage. However, these traction performance metrics (friction and fluid drainage) diminish with wear. This study quantifies shoe traction performance in response to natural wear and compares the relationship between common wear metrics: time, distance walked, and worn region size (WRS). Participants wore two pairs of shoes in the workplace for up to 11 months and the distance walked was tracked with a pedometer. After each month of wear, traction performance and WRS of each shoe were measured. Traction performance was quantified by the under-shoe available coefficient of friction and fluid force during a simulated slip test. Increased wear (months worn, distance walked, and WRS) was associated with decreased traction performance. A WRS of 800 mm² was associated with reductions in friction of 16–38% and increases in fluid force by 286–528%. Three and six months of wear were associated with WRS values of 251 mm² and 462 mm² and distances of 203 km and 519 km, respectively. A walking distance of 500 km was associated with a WRS of 406 mm². This study showed that all of these wear metrics are good indicators of shoe traction performance loss. Thus, the most practical metric in a particular application can be selected. We argue that WRS may be the best indicator due to variations in wear rate from the user and environment. Therefore, tracking footwear usage and monitoring outsole wear can aid in shoe replacement recommendations to reduce slips and falls.
Occupational Applications:
Slips and falls are among the most common reason for non-fatal work accidents. Preventing slips in the workplace can be achieved by ensuring sufficient friction between the shoe and floor. As shoes are worn down, there is a decrease in the coefficient of friction, which increases the risk of injury from a slip and fall for the wearer. We found that shoes worn in the workplace commonly had friction performance that is about 25% lower than their new condition and that this effect was largest for shoes with the highest initial friction performance. These results inform the magnitude of improvement in friction performance that can be achieved through footwear replacement programs.Technical Abstract: Background: As slip-resistant shoes are naturally worn, the coefficient of friction (COF) decreases. Proper and timely shoe replacement is an important factor for preventing injuries related to slips. Knowledge of the change in COF for naturally worn shoes in the workplace, relative to the COF of their new counterparts, is needed for a better understanding in this area. Methods: Slip-resistant shoes worn in the workplace and their new counterparts were mechanically tested to assess their COF. Eighteen pairs of shoes (new and worn) were tested on a whole-shoe slip testing device that simulates under-shoe slipping conditions. The COF was calculated for each pair of shoes at a shoe-floor angle of 17 ± 1° relative to the ground surface, a speed of 0.5 m/s, and a mean normal force of 250 ± 10 N. Results: A mean decrease in COF of 0.055 (25%) was observed when comparing the naturally worn shoes with the new shoes. New shoes with an initial higher COF showed a larger loss in COF due to wear. Conclusions: Naturally worn, slip-resistant shoes have substantively reduced COF compared to their new counterparts. These findings demonstrate the potential for programs that monitor and replace slip-resistant shoes as a means to prevent slips.
Minimal footwear has become more ubiquitous; however, it may increase slip severity. This study specifically examined the slipping kinematics of flip-flop sandals. Invoked slips from standing were evaluated in dry and wet tile, and a unique wet footbed + wet tile condition, with 40, 50, and 60% bodyweight (BW) committed to the slipping foot. Water did not alter peak slip velocity (PV) at 40% BW, but PV increased with greater slip-foot force on wet tile by ~1 m/s. Interestingly, when floor-contact was lost during the slip, the flip-flops could come off the heel. This decoupling occurred most often when both the tile and footbed were either dry or wet. Given that both decoupling and greater PV were observed on wet tile, slipping in flip-flops under wet conditions may have more serious consequences. The results highlight that slips may occur at both the foot—flip-flop, and flip-flop—tile interfaces.
The main aim of this paper is to study the behavior of different types of floor materials suitable for wheelchair users. The study depends on determining the values of friction coefficient displayed by the wheelchair and the tested floor materials. Finite element 3D model of friction pair is introduced and analyzed using commercial finite element software ABAQUS/CAE. The friction coefficient values obtained from the experimental results are used as input data of the simulation model to achieve the same characteristics. It can be concluded that each case of the three tested rubber specimens-show friction values suitable for safe walking. Also it can be noticed that as the rubber hardness decreases friction coefficient increases. The simulation model makes it easy to determine the contact stress between friction pair and contact slip rates. INTRODUCTION Wheelchairs used when walking is difficult or impossible due to illness, injury, or disability. Wheelchairs come in a wide variety of formats to meet the specific needs of their users. Although most wheelchair users are able to comfortably move a joystick and make a fine movement correction when driving, others are only able to click on switches. On the other hand, wheelchair users needs smooth and hard floor, where wet flat surfaces can become extremely slippery cause slip and fall accidents. For controller design therefore, it is necessary that the wheelchair model is comprehensive enough to reflect real situations. There is an increasing demand to investigate proper solutions for reducing slip and fall accidents. The friction of footwear on floor coverings is responsible of the occurrence of slips and falls. The slip resistance is normally assessed on the basis of friction coefficient measured with footwear materials sliding against floorings.
The present work discusses the friction behavior of different floor materials when rubber sole slid against them under dry, water and detergent wet sliding conditions. In order to offer durable and elastic behavior as well as shock absorption for the tiles, polyurethane (PU) coating was applied on the surface of cement tiles. Then rubber, sand and glass granulates as well as steel wires were used as filling and reinforcing addition to PU.
It was found that at dry and wet sliding, friction coefficient displayed by tiles coated by PU filled by glass granulates showed the highest friction values. It seems that abrasive action of the glass granulates into the rubber surface was responsible for that behavior. Rubber coating displayed relatively lower value of friction coefficient followed by the unfilled PU coating. Cement tiles and tiles coated by PU and reinforced by steel wires offered the lowest values. Coating cement tiles by PU filled by sand particles showed higher values of friction coefficient at dry sliding. In contradiction to that, presence of water and detergent film caused drastic friction decrease due to the presence of multi tiny reservoirs that during sliding the fluid gets up to the sliding surface forming a film and consequently friction decreased.
Sheet-type resin floors possess a risk of slipping during rains or liquid spills. We investigated the friction properties of vinyl flooring sheets using shoes and glycerol solution, and clarified the combined effect of the groove's depth and width and a urethane coating on the coefficient of friction (COF). According to the analysis, the static COF could be expressed using the spreading coefficient. All the dynamic COFs could be expressed using the spreading coefficient and aspect ratio of the grooves. All the COFs were significantly affected by the interfacial tension at the triple line but were relatively unaffected by the groove shape.
Falls resulting from slips on walkway surfaces are a significant source of injury in society. To measure friction between the floor and the shoe, various types of tribometers and ASTM standards have been developed to assess walkway slip-resistance with the goal of improving pedestrian safety. The purpose of this study was to determine the repeatability and bias of the PIAST and VIT tribometers under both dry and wet conditions. Both devices were tested on an AMTI force platform over a wide range of angles. Bias was assessed by comparing the tribometer slip resistance reading to the actual Fx/Fz ratio measured by the force plate, while reliability was established by evaluating the ability of the tribometers to reproduce Fx, Fz, and the Fx/Fz ratio. Both tribometers demonstrated high degrees of bias and repeatability under both wet and dry conditions; however, each measured different slip-resistance values for the same surface. Further study should be directed at establishing which tribometer best simulates initial foot contact during gait with respect to measuring slip resistance.
Measurement of the coefficient of friction (COF) between the shoe/sole and the floor is essential in understanding the risk of slipping accidents. In this research, the COF of five floor materials commonly used on a university campus, under five surface conditions including dry and four liquid spillage conditions, were measured. The COF measurements were conducted using a Brungraber Mark II slip tester with four footwear materials: leather, neolite, ethylene vinyl acetate, and blown rubber. The results of the COF measurements showed that floor tile, footwear material, and surface conditions were all significant factors affecting the COF. Interactions between these factors were also significant. Four surface roughness parameters (Ra, Rtm, Rpm, Rq) of the five tiles selected in the friction measurement were measured using a profilometer. The roughness of the two ceramic tiles was significantly higher than the three non-ceramic tiles. The correlation between the four roughness parameters and the measured COF was very high (r=0.932 to 0.99) under both wet and water–detergent conditions. The tile and surface conditions in the friction measurements were presented to 24 subjects and the subjective evaluation of floor slipperiness was determined. The differences of the scores from the five surface conditions were statistically significant. The difference under floor tile conditions with the same spillage condition was, however, not significant. Spearman's rank correlation coefficients between subjective score and measured COF using neolite footwear were in the range of 0.8–0.975 for the five floors under all the surface conditions. This implies that subjective scores may reasonably reflect floor slipperiness measured with the Brungraber Mark II slip tester using neolite footwear pad.
The significance of occupational falls is established through analysis of workers' compensation data of a major insurance company. The data covered 11% of the American privately insured workforce and exposure estimates were based on Bureau of Labor Statistics demographics. The number of incidents and the relative cost of falls were examined by age, gender, industry, climate and geographic region and empirical data are presented. These data establish the enormous cost of falls measured in terms of individual pain and suffering and in losses to industrial organizations.
Description
The purpose of ASTM sponsored F13 Committee Symposium titled "Slips, Stumbles, and Falls: Pedestrian Footwear and Surfaces" was the presentation of new ideas relating to pedestrian walking related accidents.
In this study, progressive wear and surface alterations which take place on the shoe surfaces during the repetitive slip resistance measurements are outlined in an attempt to formulate a general picture of the friction and wear mechanisms involved. A theory on the different types of surface alterations and wear evolution of the shoe surface was then developed. The surface changes and wear progress were quantified using conventional surface roughness parameters as well as a set of visual examinations based on a scanning electron microscope and extended it to three-dimensional interpretation. Surface profiles of the three different shoes were recorded using a laser scanning confocal microscope. A number of surface roughness parameters, viz., the center line average (CLA, Ra) and root mean square (RMS, Rq) roughness, maximum mean peak-to-valley height (Rtm), maximum mean peak height (Rpm), maximum mean depth (Rvm), and average asperity slope (Δa) were calculated. The analysis showed that the surface textures of each shoe underwent marked variations during the entire rubbing processes. It was concluded from the surface roughness measurements that the Ra roughness parameter was correlated with the standard deviation of peak heights and also had a linear relationship with the average asperity slope. Results from the surface roughness parameters also indicated that variations in the geometry of the shoe heels had a major effect on the slip resistance characteristics. Furthermore, it was found from the microscopic observations that the progressive wear was more severe than expected and initiated in the very early stage of sliding. The progressive wear was initiated by ploughing after only a few rubbings and this mechanism immediately was followed by simultaneous ploughing and abrasion. Micro-topographic information as described in this study may provide a useful information for the understanding of friction and wear mechanisms and the interpretation of any slip resistance result.Relevance to industrySlipping and falling accidents are a major ergonomic and safety concern in the workplace and the general community. Prevention of slip hazard has focused on designing “slip resistant” footwear and floor surfaces. This study is primarily concerned with surface alterations and wear detection of the shoe soling from a microscopic point of view. Microscopic approaches may provide additional useful information on the analysis of slip resistance performance.
The great number of slipping accidents indicates that footwear providing good slip resistance must be rare. Slip resistance seems to be a purely physical phenomenon, however, more knowledge of the mechanisms of friction is needed to develop slip-resistant footwear and to ensure safer walking in slippery conditions. In the present study the influence of the normal wear of shoe heels and soles on their frictional properties was clarified. The slip resistance of three types of new and used safety shoes on four relatively slippery floor-contaminant combinations, was assessed with a prototype apparatus, which simulates the movements of a human foot and the forces applied to the underfoot surface during an actual slip. The used shoes were collected from 27 workers in a shipbuilding company and classified by sight into four wear classes: Good, satisfactory, poor, and worn-out. The assessed shoe heels and soles were in general more slippery when new compared to used heels and soles. However, footwear must be discarded before the tread pattern is worn-out. Used microcellular polyurethane (PU) heels and soles gave a considerably higher coefficient of kinetic friction (μk) on contaminated floors than used heels and soles made of compact nitrile (NR) and compact styrene rubber (SR). The heel-slide coefficient of kinetic friction (μkl) for used versus new shoes was on average 66% higher for PU (0·216 versus 0·130), 27% higher for SR (0·143 versus 0·113), and 7% lower for NR (0·098 versus 0·105). The fundamental mechanisms of friction between shoe soles and contaminated floors were also discussed, and experiments with seven slabs of sole materials were carried out to assess contact pressure effects from the viewpoint of slipping. Slip resistance particularly seemed to depend on the squeeze film and the contact pressure effects between the soling materials and the floor. An increasing contact pressure dramatically reduced the μk, thus indicating that the slip resistance varies considerably during the normal gait cycle. Hence, average friction readings are probably not at all decisive from the slip resistance point of view. An instantaneous coefficient of friction may be more relevant, because in walking the time available to achieve a sufficient coefficient of friction to avoid a slip is only a few tenths of a second.
Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following:
There are two commonly held beliefs concerning high-heeled shoes for females. The first is that high-heeled shoes are prone to cause slipping accidents. The second is that high-heeled shoes heighten the muscular load on the lower legs more than low-heeled shoes. Reports on high-heeled shoe slip resistance assessment together with a discussion on leg muscular activities when wearing high heels are, however, rare in the literature. This study assessed four commonly used female shoes, two high heels and two flat-soled shoes on four floor tiles via friction measurements and a gait experiment. In the gait experiment, the electromyographic (EMG) activities of the four muscles on the right shank of the subjects were recorded. Subjective ratings for shoe/floor slipperiness and the muscular effort in the right shank were also collected. The friction measurement results showed that the coefficient of friction (COF) for the rubber-soled high-heeled shoes was significantly lower than that for the other three shoes. Conversely, the COF for the polyurethane-soled high-heeled shoes was significantly greater than that for the other three shoes. The gait experiment results showed that high-heeled shoes resulted in significantly greater normalized EMG for the tibialis anterior, peroneus longus and soleus in the right shank during walking. The subjective rating results showed that high heels were unfavorable in terms of both slip-resistance and muscular effort in the right shank. Based on assessment of the four shoes, wearing flat-soled shoes, compared to the high h eels, has the benefits of lower shank muscular load and proper slip resistance. This study provides a scientific basis for shoe designers when designing suitable female footwear concerning slip resistance and the muscular load on the lower legs.
The validity, repeatability, precision and consistency of coefficient of friction (COF) measurements taken with three portable in situ floor slipperiness testers were evaluated. The selected test instruments represented three common operating principles, a towed-sled (Gabbrielli SM), a pendulum (Portable Skid Resistance Tester), and an articulated-strut with simultaneous application of normal and shear forces (Brungraber Mark II). The performance of these devices was studied against a force platform and a biomechanically validated slip simulator as reference equipment. The precision and consistency of the PSRT was acceptable but was reduced at higher COF levels. The validity of the PSRT for pedestrian slip resistance measurement must be improved. The BMII was more valid but less consistent and precise than the pendulum. The overall performance of the GSM was poor. The validity of this instrument can be seriously questioned. None of the testers was able to meet the technical specifications given in their appropriate instructions for use. The present study indicates that there is an urgent need to design more credible in-situ flooring slip resistance testers.Relevance to industryValid and reliable in situ tests of floorings, walkways and stairs are needed for routine control of slipping and falling injury risks and for monitoring the effects of preventive actions at the workplaces. Maintenance personnel must search for proper restoring and housekeeping strategies for enhancing a safer environment. Flooring manufacturers, on the contrary, need to verify and improve the optimum design of their products.
A sample of 40 slip, trip and fall accidents occurring during the delivery of mail were subject to detailed follow-up investigation. Interviews were conducted with accident-involved employees as soon as possible after each incident (mean time between accident and interview=9.5 days). Interviews were held at the location of the accident and covered the sequence of events and related individual, equipment and organisational aspects. The study took place October–March, reflecting the period when most accidents occur. The majority of accidents involved snow or ice (70%). A combination of slippery conditions, use of footwear with worn tread, and time-saving behaviour was found in 50% of accidents. It is suggested that a second important combination is the presence of tripping hazards and the unsafe practice of preparing mail for the next delivery while walking. Poor lighting was considered a problem in 20% of cases. Other problems identified included deficiencies with training and a low level of safety-related activity by local managers. It is concluded that there are opportunities for intervention that should reduce the frequency of these accidents.
Different institutions reported different results for friction measurements of identical material combination and surface conditions using identical slipmeters. The objective of this study was to evaluate three factors, slip criterion, sample, and time, that could contribute to such differences with two commonly used slipmeters, the Brungraber Mark II and the English XL. Friction between 16 commonly used footwear materials and three floor materials was measured under four surface conditions with two slip criteria at the interface. Some of the measurements were repeated at a different time. The results indicated that variations due to different samples were probably the smallest statistically among the three factors evaluated. The effect of slip criterion on friction coefficient could be quite significant compared with the effect of time for some material combinations and surface conditions. A more consistent slip criterion could potentially reduce the differences significantly in the results reported among different institutions.
The shoe sole geometrical design parameters, such as tread groove orientation and groove width, were believed to be important factors affecting the COF between the shoe/floor interface. In this study, friction measurements using a Brungraber Mark II slipmeter were conducted under three footwear materials, three floors, and three contamination conditions. Six tread groove designs (2 widths × 3 orientations) on the footwear pads were tested. The results showed that all the footwear materials, floors, and the contamination conditions affected the measured COF significantly. In addition, the tread groove orientation and width also affected the COF significantly. It was found that wider grooved footwear pads resulted in higher COF values and footwear pads with tread grooves perpendicular to the friction measurement direction had higher COF values. A linear regression model using COF as the dependent variable and tread groove width, tread groove orientation, footwear material, floor, and contaminated conditions as independent variables was established. The lack of fit test result for the model was significant at p < 0.0001, indicating that the model adequately fit the friction measurement data.
It is known that surface roughness affects friction. However, it is not clear which surface characteristics are better correlated with friction. An extensive search for a relationship between surface roughness parameters and friction was completed in this study. Surface roughness on unglazed quarry tiles was systematically altered by sand blasting. A commercially available pin-on-disk tester was used to measure dynamic friction under broad testing conditions at the interface. A commercially available profilometer was used to measure the surface roughness of the tiles. The results indicated that, among the surface parameters evaluated in this study, Rpm and a had the highest correlation with friction. Rpm is the average of the maximum height above the mean line in each cut-off length and represents the averaged void volume among asperities on the surface.a is the arithmetical average of surface slope and is related to the rate of asperity deformation during a sliding contact. The averaged surface parameters generated from eight surface measurements from an area of interest were sufficient to give a fairly good indication of surface friction.
There have been 50 years of research in walking/working surface slipperiness and coefficient of friction (COF) measurements. Nevertheless, numerous standards address slip/fall accidents only in terms of requiring surfaces to be qualitatively “nonslippery.” The literature useful for establishing quantitative criteria for “slippery” vs. “slip-resistant” have been summarized here. A performance definition for “slippery work surfaces” is proposed. Recommendations applicable to standards-making organizations are made, including changing terms such as “non-slip” to “slip-resistant” and defining “slippery” in terms of quantitative COF values. For persons walking unloaded on level surfaces, a COF standard of 0.5 would be reasonable. Research is recommended to determine if “slip-resistance” requirements and accident prevention could be achieved more easily be controlling the type of shoe, type of task, or amount of surface contaminant rather than controlling only the COF of the basic surface and its coating.
Sumario: This paper is concerned with the study of the tribological phenomena that occur in slipping accident analysis. This analysis considers the state of the floor surface, the lubricant that covers it and the elastomer itself since, within the scope of prevention of slip-induced falls, concern is with the friction present between a lubricated surface and a sole of a shoe because slipping arises principally on wet, greasy or lubricated surfaces
Initial research by the INRS showed the importance of biomechanical factors in the causes of accidents by slipping. Dynamic friction was shown to be far more significant than static friction. The measuring procedure which has been developed does not provide a model of walking or slipping but a physical measurement giving the same ranking as subject evaluation methods. Systematic measurements show the effect on slip resistance of the material used and the configuration of the sole. Following publication of these results, manufacturers have improved the slip resistance of shoes. An internationally acceptable method (ISO) should, however, be developed so that slip resistance, which is such an important factor in accident prevention, can be given as much attention as other features of the sole. Scientific research on the psychophysiology of equilibrium on slippery surfaces is needed, as is applied research on friction with lubricated elastomers and on-site research into floor-surface friction.
Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following: (A) returning to safety footwear soled with the microcellular polyurethane AP66033; (B) abrading all new and smooth footwear solings with a belt sanding machine coated with P100 grit; (C) avoiding the use of floor polish; (D) informing the general public about the poor slip resistance of ordinary footwear on ice and the lowering of slip resistance in cold weather.
Risk factors for slip, trip and fall accidents (STFA) during the delivery of mail were identified using a range of accident-centred and accident-independent methods. Key factors included slippery underfoot conditions, non-weather related environmental hazards (e.g., uneven paving, steps, inadequate lighting), poor slip resistance from footwear, unsafe working practices, management safety practices, and underlying organisational influences. Intervention measures were recommended that target STFA risks at three levels: slip resistance, exposure to hazardous conditions, and employee behaviour in the face of hazardous conditions. The use of a participative approach to intervention selection and design enabled allowance for the organisational context to be made.
The slip resistance of 16 commonly used footwear materials was measured with the Brungraber Mark II and the English XL on 3 floor surfaces under surface conditions of dry, wet, oily and oily wet. Three samples were used for each material combination and surface condition. The results of a one way ANOVA analysis indicated that the differences among different samples were statistically significant for a large number of material combinations and surface conditions. The results indicated that the ranking of materials based on their slip resistance values depends highly on the slipmeters, floor surfaces and surface conditions. For contaminated surfaces including wet, oily and oily wet surfaces, the slip resistance obtained with the English XL was usually higher than that measured with the Brungraber Mark II. The correlation coefficients between the slip resistance obtained with these two slipmeters calculated for different surface conditions indicated a strong correlation with statistical significance.
This paper seeks to address questions related to friction measurement such as how friction is related to human-centred assessment and actual slipping, and how repeatable friction measurements are. Commonly used devices for slipperiness measurement are surveyed and their characteristics compared with suggested test conditions from biomechanical observations summarized in Part 1. The issues of device validity, repeatability, reproducibility and usability are examined from the published literature. Friction assessment using the mechanical measurement devices described appears generally valid and reliable. However, the validity of most devices could be improved by bringing them within the range of human slipping conditions observed in biomechanical studies. Future studies should clearly describe the performance limitations of any device and its results and should consider whether the device conditions reflect these actual human slipping conditions. There is also a need for validation studies of more devices by walking experiments.
Slips and falls are major problems in occupational injuries in which floor slipperiness is a critical issue. Most of the studies on slipperiness assessments were conducted in laboratories. Field assessments are rarely reported in the literature. This study investigated floor slipperiness in seven kitchen areas of 10 western-style fast-food restaurants in Taiwan using both objective and subjective measurements which were conducted by friction measurements and by employees' ratings of floor slipperiness, respectively. The friction measurement results showed that the sink area had the lowest average friction in the kitchens. Employees, however, rated both the sink and back vat (chicken fry) areas as the most slippery areas. The Pearson's and Spearman's correlation coefficients between the averaged friction coefficients and subjective ratings for all 70 evaluated areas across all 10 restaurants were 0.49 and 0.45, respectively, with p < 0.0001 for both. The results indicate that average friction coefficient and perception are in fair agreement, suggesting that both might be reasonably good indicators of slipperiness.
Tread groove design is very common in footwear. However, coefficient of friction (COF) measurements between the footwear material and floor using a slipmeter were commonly performed using flat footwear pads. Such measurements might underestimate the actual slip resistance of the footwear pad. This research investigates the effects of the tread groove width on the measured COF using four footwear materials, three floors, and four liquid-contamination conditions using a Brungraber Mark II slipmeter. The analysis of variance results indicated that the footwear material, floor, contamination conditions, and groove width were all significant (p < 0.0001) factors affecting the measured COF. The hypothesis that wider tread grooves result in higher COF values was true with some exceptions especially on oil contaminated floors. A regression model, with an R2 of 0.91, was established to describe and predict the relationship between the COF and the tread groove width under footwear material/floor/contamination conditions.
Slip resistance-field measurements using two modern slipmeters
- B C Grieser
- T P Rhoades
- R J Shah
Grieser, B.C., Rhoades, T.P., Shah, R.J., 2002. Slip resistance-field
measurements using two modern slipmeters. Prof. Saf., 43-48.
Standard method of test for using a portable inclinable articulated strut slip tester (PIAST)
American Society for Testing and Materials F-1677-05, 2005. Standard
method of test for using a portable inclinable articulated strut slip
tester (PIAST), Annual Book of ASTM Standards, vol. 15.07, West
Conshohochen, PA.
Slip resistance—field measurements using two modern slipmeters
- Grieser