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The effect of footwear sole abrasion on the coefficient of friction on melting and hard ice
Abstract
Footwear sole wear by natural use or artificial abrasion either increases or decreases slip resistance on floors with and without lubricant. The objectives of this paper were to study the effect of footwear sole abrasive wear on slip resistance on ice with respect to temperature, and to compare the slip resistance of abraded soles on melting and hard ice with that on lubricated steel plate. The kinetic coefficient of friction (COF) of nine pairs of footwear were measured with the stationary step simulator developed at the Finnish Institute of Occupational Health, before and after the new footwear soles were artificially abraded. Two-way factorial ANOVA showed that the abrasion of nine pairs of footwear had no significant effect on COF on melting ice (Mean COF with abrasion=0.056, std=0.0158, COF without abrasion=0.055, std=0.0205, P=0.805). On hard ice, however, the COF of abraded soles measured (mean COF=0.244) was significantly higher than without abrasion (mean COF=0.180, p<0.001), and than abraded soles on lubricated steel (mean=0.137, p<0.001). There is statistical significance between the three types of surfaces (p<0.001). On hard ice, regardless of abrasion, curling footwear with crepe rubber soling showed significantly higher COF (mean=0.343 after abrasion, 0.261 before abrasion) than other types (p<0.001). The results indicate that artificially abraded footwear is more slip resistant than new one for use on hard ice. The abrasion requirement could be specified if developing a new standard to measure COF on ice in the future. Of the footwear measured, the curling footwear with crepe rubber soling performed best in terms of slip resistance property. Therefore, Crepe rubber soling is highly recommended for use on hard ice. Melting ice is much more slippery, in which sole abrasion does not improve slip resistance. Thus, additional measures should be taken to reduce slip and fall risk.
... A PU sole is the most slip resistant soling for use on oily and wet floors (Manning et al., 1985, Manning and Jones, 1994, Gao et al., 2003. Grönqvist and Hirvonen (1995) recommended soft heel and sole materials of thermoplastic rubber (rather than PU) for winter footwear for use on dry ice (-10°C), believing that PU was not safe enough on wet ice (0°C). ...
... The coefficient of friction on melting and hard ice showed that on melting ice, all types of footwear soles had lowest COF. Crepe rubber is recommended for use on hard ice (Gao et al., 2003). There seems to be no universal soling material which is slip-resistant on different icy surfaces, e.g., dry and wet ice. ...
... The materials and the friction properties of ice and snow change with different temperatures. Tests have shown that on wet ice practically all shoe materials are very slippery (Gao et al., 2003, Gao andAbeysekera, 2004b). ...
... Atmospheric icing occurs when water droplets in the atmosphere freeze and adhere to surfaces [1], leading to various safety and energy issues. Accumulation of atmospheric icing on aircraft wings, air intake system of vehicles, cameras of autonomous vehicles, and roads and cable-stayed brides negatively impacts transportation industry [2][3][4][5][6]. Moreover, atmospheric icing can lead to electrical outages by failure of power transmission lines [7], reduce of power generation by solar panels [8] and wind turbines [9], and disrupt of offshore oil and gas production [3], impacting energy industry. ...
... Falling of snow from these surfaces can cause severe damages to the structures, vehicles, and individuals beneath them. Slipping of pedestrians and cars on surfaces covered with ice and snow is another common phenomenon causing injuries and safety concerns, making the design of surfaces with increased ice/snow friction necessary [6,27]. Moreover, snow accumulation on visual sensors of autonomous vehicles (AV) can block them and lead to malfunction of such autonomous features. ...
Snow accumulation alters the energy budget of engineered (i.e. photovoltaic panels) and natural surfaces (i.e. earth) by affecting the amount of solar energy these surfaces can absorb. Falling of accumulated snow from overhead structures (i.e. telecommunication towers, power lines, wind turbines, and bridge cables) and slipping pedestrians and vehicles on surfaces covered with snow and ice can lead to injuries and safety issues. This review article aimed to provide an overview of snow from its nucleation/formation fundamentals to its interaction with man-made and natural surfaces leading to its accumulation, followed by its removal via shedding and/or melting. Mechanical, thermal, and thermodynamics properties of snow were reviewed providing insights on their impact on snow interaction with surfaces. Finally, currently-available active and passive techniques to mitigate issues associated with snow accumulation on surfaces were reviewed, and perspectives on challenges ahead were provided.
... The materials may change their properties at temperatures below 0°C and with any abrasion that occurs. Also, the friction properties of the ice and snow change with different temperatures (Gao et al., 2003(Gao et al., , 2004. At temperatures above 0°C ice and compacted snow may be covered with water film that acts as a lubricant. ...
... Footwear for temperatures between +5°C and À10°C should have sole material COF measured on wet ice, and footwear for temperatures below À10°C should have sole material COF measured on hard ice and with footwear conditioned in cold. However, several tests have shown that on wet ice most shoe materials are very slippery (Gao et al., 2003(Gao et al., , 2004. Thus, these tests may not be very significant and shoes for the range of +5°C to À10°C could be tested by both other methods instead, unless a new special sole material was developed for these conditions. ...
In cold climates all user requirements for footwear (insulation, waterproof, vapor permeability, drying, etc.) cannot be met easily due to their conflicting nature. Defining user conditions is important. Cold may be roughly divided into the three ranges (>+5; + 5 to − 10; <−10°C). The choice of proper footwear may be based on this approach. It also reduces some of the conflicting user requirements. Under any defined user condition it is important to take proper care of the feet and the footwear. The best performance can be achieved when considering at the design stage that not only the materials in footwear but also the whole foot-sock-footwear system should work together.
... According to their assessment, the nature of the material from which the sole is made and its firmness are the crucial factors determining the adhesion on dry ice. Higher probability of slipping on melting or wet ice has been confirmed by Gao et al. [5], who has also examined the effect that the sole has on the friction coefficient. ...
... Undoubtedly, the dynamics (kinetic) coefficient of friction (COF) of the sole to the icy surface is of particular importance for this resistance. As established, COF depends on the roughness and structure of the material for soles production, in the case smoother surfaces and softer materials have a higher grip [5]. ...
... The most common primary reasons for falls were slips, trips and losses of balance 14) . The inclined surfaces increased the risk of slip and fall incidents due to potentially large shear forces at the shoe/floor interface 14,16) , frictional properties of the support surface 14) , and low friction induced by various contaminations such as precipitation, condensation, snow or ice 14,15,17) . While there are numerous studies on balance control in quiet stance 2, 6-8, 10, 12, 18) , investigations on standing balance on inclined supporting surface materials in relation to induced perturbations and reduced friction are not well documented. ...
... Furthermore, the slip risk could also be higher if more slippery materials were used in either the shoe soles or underfoot surface. For example, the available coefficient of friction on melting ice (0.06) could be much smaller 17,38) than those on the two surfaces tested, and smaller than the utilised COF obtained in present study. Therefore, to maintain standing balance on icy roofs is very difficult and slip and fall risks are extremely high. ...
Working and walking environments often involve standing positions on different surfaces with inclination and different friction. In this study, standing balance of thirteen participants during sudden and irregular external perturbation to calf muscles while standing was investigated. The aim of the study was to evaluate the combined effect of surface inclination and friction on standing balance. The main findings when eyes closed revealed that the standing utilised coefficient of friction (μSUCOF) increased when the surface was inclined for both high and low friction materials. The anterior-posterior torque increased more anteriorly when the surface was inclined toes down and when the surface friction was low. The results indicate that the anterior-posterior torque is a sensitive parameter when evaluating standing balance ability and slip risk. On inclined surface, particularly on the surface with lower friction, the potential slip and fall risk is higher due to the increase of standing utilised coefficient of friction and increased forward turning torque.
... The study reported here and Gao and Abeysekera (2002) showed that the footwear with the PU outsole is slippery on ice, and even more slippery than nitrile and natural rubber outsoles. The latest comparative study of the COF of soling materials on hard ice (7 108C), melting ice (08C) and lubricated steel showed that PU soling is not superior to other tested materials on hard ice and melting ice ( Gao et al. 2003). Therefore, there seems to be no universal soling material, which is slip resistant on different surfaces, e.g. ...
... The latest research has shown that the artificial abrasion of footwear can significantly increase COF on hard ice (108C). However, after abrasion, the increase of COF of PU soling was not significantly more than other materials ( Gao et al. 2003). The roles of both footwear and floor surface roughness in the measurement of slipperiness, as well as various techniques, parameters and instruments for roughness measure- ments are reviewed by Chang et al. (2001b). ...
The objective of this paper is to explore the slip resistant properties of footwear on ice
... The materials may change their properties at temperatures below 0˚C and with abrasion. The friction properties of the ice and snow also change with different temperatures 31,33) . At temperatures above 0˚C, ice and trampled snow may be covered with a water film that acts as a lubricant. ...
... Tests have shown that on wet ice practically all shoe materials are very slippery 31,33) . Thus, these tests may not be very meaningful and shoes for the range of +5 to -10˚C should be tested by both methods. ...
The paper summarizes the research on cold protection of feet. There exist several conflicting requirements for the choice of the best suited footwear for cold exposure. These conflicts are related to various environmental factors, protection needs and user comfort issues. In order to reduce such conflicts and simplify the choice of proper footwear the paper suggests dividing the cold into specific ranges that are related to properties and state of water and its possibility to penetrate into, evaporate from or condensate in footwear. The thermo-physiological background and reactions in foot are briefly explained, and main problems and risks related to cold injuries, mechanical injuries and slipping discussed. Footwear thermal insulation is the most important factor for protection against cold. The issues related to measuring the insulation and the practical use of measured values are described, but also the effect of socks, and footwear size. Other means for reducing heat losses, such as PCM and electrical heating are touched. The most important variable that affects footwear thermal insulation and foot comfort is moisture in footwear. In combination with motion they may reduce insulation and thus protection against cold by 45%. The paper includes recommendations for better foot comfort in cold.
... The study reported here and Gao and Abeysekera (2002) showed that the footwear with the PU outsole is slippery on ice, and even more slippery than nitrile and natural rubber outsoles. The latest comparative study of the COF of soling materials on hard ice (7 108C), melting ice (08C) and lubricated steel showed that PU soling is not superior to other tested materials on hard ice and melting ice (Gao et al. 2003). Therefore, there seems to be no universal soling material, which is slip resistant on different surfaces, e.g. ...
... The latest research has shown that the artificial abrasion of footwear can significantly increase COF on hard ice (108C). However, after abrasion, the increase of COF of PU soling was not significantly more than other materials (Gao et al. 2003). The roles of both footwear and floor surface roughness in the measurement of slipperiness, as well as various techniques, parameters and instruments for roughness measurements are reviewed by Chang et al. (2001b). ...
Current research on slipperiness of footwear has mainly focused on floors and lubricated floors. Slips and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in winter season in many parts of the world. However, in comparison with the size of the problem, research on slips and falls on icy and snowy surfaces has been scarce. The objective of this paper is to explore the slip resistant properties of footwear (soling materials, roughness and hardness) on ice. The coefficients of kinetic friction of four different soling materials (synthetic rubber, nitrile rubber, natural rubber and polyurethane) were measured on ice (-12 degrees C). The outsole roughness and hardness were also measured. Results showed that the polyurethane soling did not perform better than synthetic rubber, nitrile rubber and natural rubber on pure hard ice (-12 degrees C). Soling roughness was positively correlated with the coefficient of kinetic friction. The most slip resistant soling material (polyurethane) on floors and lubricated floors may not provide sufficient slip resistance on ice.
... Some studies have indicated that sole roughness influences friction performance in the presence of liquids, while others have not found such a trend [22,23,27]. In the presence of ice, sole roughness has been associated with improved friction [28][29][30]. Lastly, the material has an important role in friction. Material properties can influence the deformability of the surface, which can change the contact region and subsequently alter friction performance [22,31]. ...
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.
... Outsole parameters including contact area (Iraqi et al., 2020;Jones et al., 2018), tread channel features (depth and width) (Beschorner and Singh, 2012;Blanchette and Powers, 2015;Chen, 2004, 2005), and material hardness (Cowap et al., 2015;Iraqi et al., 2020;Jones et al., 2018;Moore et al., 2012;Strobel et al., 2012) have been shown to influence COF. Furthermore, naturally worn (Gr€ onqvist, 1995;Hemler et al., 2018) and artificially worn shoes (Beschorner and Singh, 2012;Gao et al., 2003;Hemler and Beschorner, 2017) have demonstrated a reduced shoe-floor COF on oily surfaces relative to their new counterparts. Lower COF values are associated with higher slip risk (Beschorner et al., 2019a;Hanson et al., 1999;Iraqi et al., 2018). ...
Worn shoes are known to contribute to slip-and-fall risk, a common cause of workplace injuries. However, guidelines for replacing shoes are not well developed. Recent experiments and lubrication theory suggest that the size of the worn region is an important contributor to the shoe tread's ability to drain fluid and therefore the under-shoe friction. This study evaluated a simple test for comparing the size of the worn region relative to a common object (AAA and AA battery) as a means of determining shoe replacement. This study consisted of three components involving slip-resistant shoes: Experiment #1: a longitudinal, mechanical, accelerated wear experiment; Experiment #2: a longitudinal experiment where the same shoes were tested after each month of worker use; and Experiment #3: a cross-sectional experiment that exposed participants to a slippery condition, while donning their own worn shoes. The COF (Experiments #1 and #2); under-shoe fluid pressure (all experiments); and slip severity (Experiment #3) were compared across outcomes (fail/pass) of the battery tests. Larger fluid pressures, lower coefficient of friction, and more severe slips were observed for shoes that failed the battery tests compared with those passing the tests. This method offers promise for assessing loss in friction and an increase in slip risk for slip-resistant shoes.
... A major and prominent factor for stability when walking on ice-covered surfaces constitutes the friction produced between the shoe sole surface and the ice-covered surface. The foregoing conclusion is confirmed by a number of studies in the field of friction produced between the winter shoes soles made of different materials and icecovered surfaces [4][5][6]. There are a number of researches in the patent literature related to new materials for winter soles and boots soles that guarantee a high coefficient of friction when walking. ...
The subject matter of the present research constitutes a study of the technique of friction between samples and prototypes of soles made of composite materials comprising natural rubber characterized with ingredients originating from renewable sources produced in the course of their contact with an ice surface. Methods and devices were developed in order to investigate the static and dynamic friction force and the change with regard to frictional force in the event of contact with regard to three varieties of forms of ice: melting ice (ice with a layer of water on it, temperature: 0 to 1 °C), wet ice (temperature: - 4° -5° C) and dry ice (temperature: - 10° - 12° C). Coefficients of static and dynamic friction, along with change of the friction coefficient were obtained for 14 types of elastomers and ingredients from renewable sources - natural rubber, silicon dioxide extracted from the process of burning rice husks and microcrystalline cellulose, and using rapeseed oil as a technological additive. It has been ascertained and concluded that all tested materials have demonstrated highest friction coefficient in the event of contact produced with dry ice being the maximum coefficient of friction equal to 0.61. The most unfavorable and dangerous hypothesis for exposure of pedestrians to the effect of on an ice- covered surface are the cases of contact with wet ice and melting ice. There is no correlation of the coefficient of friction for the different materials under conditions of dry ice, wet and melting ice. The composites with the highest coefficient of friction under circumstances of wet and melting ice have been used to produce prototypes of soles, having identical pattern, and experimental results were obtained for the coefficients of friction and the friction coefficient change /rise/ in the event of contact produced with regard to dry, wet and melting ice. By means of implementation of the 3D printing technology, patterns of footwear soles with identical dimensions were made of the same material but with different patterns and results were obtained for the impact of the pattern on the static and dynamic coefficient of friction produced in the course of a contact with an ice surface in its three relevant states - dry, wet and melting ice. The implementation of this study has been funded by the Operational Program 2014BG16RFOP002 - Innovation and Competitiveness, Procedure: BG16R-FOP002-1.002 - Support for the development of innovations by start-ups, Grant Agreement BG16R-FOP002-1.002-0028-C01 Eco-footwear soles on elastomeric basis with improved ice and snow grip.
... Marked differences are also observed in the values for mechanical loss angle tangent at 0 °C and 60 °C. It is obvious, even surprising, that the vulcanizates containing RHA-IND at 0 °C have values 4-5 times higher than the values for the two other samples, indicating that those vulcanizates would also have a very high friction on ice and snow, i.e., they would be suitable for winter applications (winter shoe soles, extreme hiking footwear, ski boot soles, winter tire treads, etc.), where friction on ice is very important [34,35]. With respect to the mechanical loss angle tangent at 60 °C, the vulcanizates containing RHA-BG have values 2 to 2.5 times lower than those of the other samples. ...
Natural products from agricultural wastes are finding importance in the polymer industry due to their many advantages such as being lightweight, low cost and environmentally friendly. In the present study the potential of the two types of rice husk ash (RHA) prepared under different conditions as fillers in natural rubber-based elastomer composites was investigated. The fillers were prepared by rice husks incineration and characterized by means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) specific surface area, Hg-porosimetry and N2-adsorption. The evaluation involved determining the vulcanization characteristics of the compounds and their physical and mechanical characteristics, resistance to thermal aging as well as the dynamic properties of the vulcanizates containing RHA. It has been found that the ash from rice husk has good potential as filler in elastomers, especially as a substitute for synthetic commercially available silica. RHA improves the grip on ice and snow better than standard silica and may be used in formulations for shoe soles used for winter sports, extreme hiking footwear, ski boot soles, winter tire protectors, etc. Its quality depends on the conditions under which rice husk is incinerated. It is recommended to run the process at a temperature not higher than 800 °C. In particular, cases in which the vulcanizates contain biogenic silica have very interesting characteristics like improved modulus at 300% of elongation, lower residual elongation, higher mechanical loss angle tangent at 0 °C and lower at 60 °C, and are superior to those of the vulcanizates containing commercially available filler Ultrasil® 7000 GR.
... On the other hand, on wet ice only the tread design has an influence on the friction properties. The high slipperiness of ice was also analyzed by Gao et al [4], who have measured the effect of sole abrasive wear on the coefficient of friction on dry and melting ice. ...
A study on the effect of glass fibers/rubber composites on the grip on ice has been conducted in order to develop new materials for ski boot soles with increased grip in winter environments. The study has been conducted analyzing the friction of a composite material and of a ski boot sole containing an insert made of the composite material and comparing the results with those obtained using rubber and a thermoplastic elastomer. The analysis of the morphology of the composite surface, by Scanning Electron Microscopy, shows a homogenous distribution of glass fibers of approximately 10μm of diameter in the rubber matrix. Moreover, the measure of the contact angle shows that the composite material has a higher water repellency compared to the rubber matrix. The measure of the coefficient of friction indicates a significant effect of the glass fibers on the grip on icy surfaces. The increased grip can be ascribed to the stiffness of the glass fibers that are able to have a mechanical grip on the ice surface and to the increased contact angle and water repellency of the composite that decrease the formation of a water layer below the sole.
... Gao et al. (2008a,b) used a short, 2.7 m ice walkway inclined at 0 , 6 , and 8 to compare lower extremity muscle activity during gait on ice at À10 C to gait on a reference, non-ice ramp. In studies of footwear slip-resistance, Gao et al. (2003Gao et al. ( , 2004Gao et al. ( , 2008b conducted experiments using a stationary mechanical portable step simulator device, developed at the Finnish Institute of Occupational Health (Gr€ onqvist et al., 1989), on surfaces including ice to show the effects of abrasion, sole material, hardness, and roughness on relative COF of a variety of footwear. Bruce et al. (1986) measured the COF of winter anti-slip devices by attaching subjects in series to a load cell and a winch that dragged the subjects across a hockey rink. ...
More informative tests of winter footwear performance are required in order to identify footwear that will prevent injurious slips and falls on icy conditions. In this study, eight participants tested four styles of winter boots on smooth wet ice. The surface was progressively tilted to create increasing longitudinal and cross-slopes until participants could no longer continue standing or walking. Maximum achievable incline angles provided consistent measures of footwear slip resistance and demonstrated better resolution than mechanical tests. One footwear outsole material and tread combination outperformed the others on wet ice allowing participants to successfully walk on steep longitudinal slopes of 17.5° ± 1.9° (mean ± SD). By further exploiting the methodology to include additional surfaces and contaminants, such tests could be used to optimize tread designs and materials that are ideal for reducing the risk of slips and falls.
Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.
... On hard ice, i.e. at a cold temperature, one would expect that a might be partly controlled by the microstructure of the slider surface. This would be consistent with the findings that micro-roughness of a slider does not affect ice friction at warm temperatures but increases it at colder temperatures (Gao et al, 2003;Kietzig et al., 2009). The prediction of our model that μ decreases with increasing a is in accordance with measurements by Kietzig et al. (2011) on polished and nanopatterned surfaces. ...
... Current winter and safety footwear, and footwear believed to be slip resistant by manufacturers do not provide enough slip resistance on melting ice (Gao and Abeysekera, 2002;Gao et al., 2003). No safety footwear soling provides adequate grip on dry ice (Manning and Jones, 2001). ...
The objective of this paper was to investigate whether living experience in winter climate and winter sport helps to prevent slips and falls on ice and snow. A questionnaire survey was conducted among foreigners at Luleå University of Technology of Sweden, where winter season lasts for six months in a year. Seventy respondents replied. The results of ordinal regression showed that the slip frequency according to a 5-point rating scale decreased as the living experience in cold environments increased (B=−0.0113, p=0.019). A logistic regression was applied to model the probability of fall events occurrence based on the experience of living in cold climate. The results showed that the fall events reduced as living experience increased (B=−0.030, p=0.001). Chi-square test showed that fall events in those who took part in winter sport were significantly less than in those who did not participate in winter sport (χ2=10.745, p=0.001). The findings imply that experience of living in cold environments and training in gait balance on ice and snow can have positive effects in preventing slips and falls for inexperienced workers and pedestrians. This study also revealed that the majority of fall events happened on hard ice covered with snow while wearing ordinary winter footwear, indicating the need to improve slip resistance.
... One interesting finding was that the fall accidents happened mostly on ice covered with snow (Fig. 2). Previous laboratory studies showed that melting ice is more slippery than hard ice (Gro¨nqvist, 1995;Gao et al., 2003). However, the slip resistance between footwear and ice covered with snow surfaces has not been reported in laboratory studies. ...
Slips and falls and associated outdoor injuries are prevalent in cold climates. The objectives of this field investigation were to describe the consequences of slips and falls on ice and snow and the associated injuries, to assess the risks of various icy and snowy surfaces, to identify design needs of footwear, and to ascertain preventive measure preferences of outdoor workers. The organizations investigated were a newspaper delivery service, a military regiment, mining and construction industries. The results showed that fall events occur most frequently on ice covered with snow. This is due to the difficulty of perceiving hidden risks in order to adjust gait strategies. The professional footwear provided does not provide enough protection against slips and falls. Slip resistant properties are ranked as one of the top requirements by the users. Their most preferred preventive measures are footwear with anti-slip properties and the application of anti-slip materials, such as sand or salt.
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.
A set of thermoplastic materials employed in soles for alpine skiing boots were characterized in terms of chemical composition, cristallinity, hardness, surface roughness, and grip. The results of friction experiments on different substrates reproducing the real environmental scenarios point out that materials provide more grip as they become softer. Moreover, higher roughness results in lower dynamic coefficient of friction (COF). Finite element simulations corroborate the experimental measures of COF and let to rationalize the role of material elasticity and surface roughness on the frictional characteristics of soles. The measure of grip on an inclined wet surface provides analogous results, indicating that COF can be used as key performance indicator in the design of ski-boot soles and of other anti-slip equipments in wet and icy environments.
In cold climates all user requirements for footwear (insulation, waterproof, vapour permeability, drying, etc.) cannot be met easily due to their conflicting nature. Defining user conditions is important. Cold may be roughly divided into the three ranges (>+5; +5 to -10; <-10 °C). The choice of proper footwear may be based on this approach. It also reduces some of the conflicting user requirements. Under any defined user condition it is important to take proper care of the feet and the footwear. The best performance can be achieved when considering already at the design stage that not only the materials in footwear but also the whole foot-sock-footwear system should work together.
Slip resistance of footwear sole affects the comfort and safety of shoes directly, and slip resistance is mainly expressed by the coefficient of friction. Within a certain range, the greater the coefficient of friction, the better the slip resistance. In order to determine the safety performance of shoes, the system will obtain the coefficient of friction by measuring the tension and pressure put on shoes, so it’s very important to do the measurement precisely. Based on QT development environment and Monitoring-controlling System of footwear sole friction, the software will execute real-time receiving, processing, controlling, displaying, drawing and saving collected data of tension and pressure via serial communication and finally on the basis of the system test to verify the correctness of the software and measurement accuracy
The slip resistance of pedestrian surfaces is usually characterized by friction coefficients measured with samples of shoe sole materials. The factors that influence the results of friction measurements were investigated for two elastomer materials and leather using the portable tribometer Floor Slide Control 2000, which was operated under varying conditions in a climate chamber on two reference surfaces. The friction behaviour observed was in accordance with viscoelastic material properties and depended on the softness of the shoe sole materials. Temperature and mechanical abrasion of the sole materials during the measurements were the factors with the greatest systematic effects on the dynamic coefficients of friction. In some cases, the coefficients of friction also depended on the direction in which a test material was slid along the same track, indicating an influence of local floor surface variations. For dry leather, the influence of relative air humidity on the measured friction coefficients strongly depended on the floor surface. Due to varying systematic influences, the standard deviations of the friction coefficients in series of 20 repetitive measurements (repeatability standard deviation) differed for the individual material combinations. Linear regression analysis of the data revealed that pure random contributions to the repeatability standard deviation were similar and around 0.005 for all investigated materials.
The current European standards for professional footwear require that the outsoles of safety and protective footwear are oil resistant. Because of this obligatory requirement, non-oil resistant materials cannot be used as outsoles in professional footwear even if some of them have been found to be more slip resistant in winter conditions than oil resistant materials. The slip resistance properties of professional footwear in winter conditions should be improved since they have been found to provide an inadequate grip on icy surfaces. The aim of this study was to establish whether there is a significant difference between oil resistant and non-oil resistant outsoles and, therefore, a need to change the EN standards regarding oil resistance to improve the grip provided by professional footwear. The Portable Slip Simulator of FIOH was used to measure the slip resistance of various outsole materials both in simulated winter conditions and in standard test conditions. Oil resistant outsoles were found to have poorer slip resistance characteristics than non-oil resistant ones, and they also hardened significantly due to cold. Based on these results, it is concluded that the current European standards on professional footwear should be altered to make oil resistance an additional requirement, so that non-oil resistant materials could be used in cases where the risk of slipping outweighs that caused by oil contamination.
For years stevedores and labour protection authorities in Finland have been concerned about the safety properties of lumber wraps. The wraps used to protect lumber during transportation and warehousing have proven to be slippery especially in wintertime when covered e.g. by ice, snow or frost. The aim of this project was to reduce the risk of industrial accidents in stevedoring of the lumber bundles by developing a measurement method that can estimate the slipperiness of lumber wraps, and by determining the slip resistance values required for safe working.The slip resistance of lumber wraps was assessed by test subjects in laboratory walking tests using paired comparison and subjective rating. The results obtained in the walking tests were used to estimate the validity and reliability of the developed measurement method. The method presented adopts a well-established slip resistance method, and the lumber wrap is covered with frost to produce a slippery surface. The results of slip resistance measurements showed a significant correlation (paired comparison: r=0.933, p
We highlight a novel composite fabrication method based on solution casting, electrospinning, and film stacking for preparing highly transparent nylon-6 nanofiber reinforced thermoplastic polyurethane (TPU) composite films. The procedure is simple and can be extended to the other thermoplastics. The morphology of fiber/matrix interface and the properties of composite films were also investigated. The method led to a significant reinforcement in mechanical properties of TPU like tensile strength, E modulus, strain, and toughness just using very small amounts of nylon fibers (about 0.4-1.7 wt %; 150-300 nm diameter). The enhanced mechanical properties were achieved without sacrificing optical properties like transparency of TPU.
In Finland about 70,000 people are annually injured in pedestrian and bicycle falling accidents occurred at the street, walkways and courtyards. Around 2/3 of these occur when the walking surface is covered by ice or snow. In general, slipping is caused by both environmental and human factors. The primary environmental factor behind slipping accidents is slip resistance characteristics of underfoot surface. Especially in winter slipping accidents are mainly due to inadequate friction between footwear and underfoot surfaces. Portable devices measuring friction, i.e. slipmeters, may be used for assessing slipperiness on different walking surfaces in situ. During winter seasons 2003 and 2004 a study was performed to evaluate the usability of portable slip simulator for measuring slipperiness of walkways on varying weather conditions and to assess slip resistance of different footwear. The Portable Slip Simulator proved to be applicable for measuring in situ the slipperiness of wintry walking surfaces and evaluating quality of winter maintenance. Significant differences in traction between footwear were found especially in normal Finnish climate winter days when friction provided by slip-resistant footwear was multifold compared to a poorer one. On very slippery icy surfaces no footwear provided enough grip and, therefore, in such conditions anti-slip devices should be used.
Current research on slips and falls has mainly focused on floors and/or contaminated floors. Although icy and snowy surfaces near melting temperature are more slippery, more important still, slip and falls on icy and snowy surfaces involve not only outdoor workers, but also pedestrians and the general public; and occur in cold regions and in the winter season in many parts of the world. However, in comparison with the size of the problem, research work done so far in this area has been limited. The objective of this paper is to present a systems perspective of slip and fall accidents, with special focus on its occurrence on icy and snowy surfaces. In order to explore the aetiology of slip and fall accidents further, and to provide the basis for prevention, the authors put forward a systems model towards the slips and falls on icy and snowy surfaces based on a review of literature and current knowledge. Various contributing factors are systematically discussed to highlight the multi-factorial nature of the problem, providing the possibility of a multi-faceted approach to reach systematic prevention. Unresolved issues related to slips and falls on ice and snow are also identified, which necessitate further research.
This study aims to investigate the effects of shoe traction and obstacle height on friction during walking to better understand the mechanisms required to avoid slippage following obstacle clearance. Ten male subjects walked at a self-selected pace during eight different conditions: four obstacle heights (0%, 10%, 20% and 40% of limb length) while wearing two different pairs of shoes (low and high traction). Frictional forces were calculated from the ground reaction forces following obstacle clearance, which were sampled with a Kistler platform at 960 Hz. All frictional peaks increased with increases in obstacle height. Low traction shoes yielded smaller peaks than high traction shoes. The transition from braking to propulsion occurred sooner due to altered control strategies with increased obstacle height. Collectively, these results provided insights into kinetic strategies of leading limb when confronted with low traction and high obstacle environments. This study provides valuable information into the adaptations used to reduce the potential of slips/falls when confronted with environments characterised by low shoe-floor friction and obstacles. It also provides the necessary foundation to explore the combined effects of shoe traction and obstacle clearance in elderly people, more sensitive to slippage.
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.
A new theory, in which friction is interpreted as the energy flux required to form surface at contact asperities, is applied to sliding on ice and snow. The results of this theoretical investigation show that in dry friction the relevant contact areas are of almost molecular scale. The properties of the interface layer in ice and snow friction arc poorly known, so that the implications of this new theory are somewhat speculative. However, qualitative agreement with experimental data is good, and the theory provides explanations to the success of some empirically developed methods of improving the frictional properties of skis and sledges.
The paper describes friction experiments on smooth icy surfaces at various temperatures. Speed and temperature variations for NR gum rubber shows that in principle the WLF transformation can be applied to friction on ice, and friction—temperature curves may be interpreted as being part of the friction master curve on smooth solid surfaces. Very near the melting point the friction decreases rapidly for all polymers, and this appears to be associated with changes in the nature of the icy surface. At low temperatures, the friction—temperature curves do not only agree in shape with curves obtained on glass but reach similar values in magnitude also. Black and oil extension effects are also similar to those expected from friction experiments on other surfaces. The blending of polymers, either in the gum state or filled with carbon black, broadens the region of high friction, enveloping the friction curves of the two polymers making up the blend. Depending on the temperature region, either one of the c...
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 kinetic coefficient of friction mu has been measured for both freshwater, granular ice and saltwater, columnar ice sliding against itself. The variables were ambient temperature (-3 C to -40 C), sliding velocity (5 x 10-7-5 x 10-2 m s-1), normal pressure (0.007-1.0 MPa) and grain size (2.5-6.0 mm). Generally, mu decreased with increasing velocity and with increasing temperature, but was relatively insensitive to both pressure and grain size over the ranges investigated. At the lower temperatures (-30 C and -40 C) the frictionvelocity curve exhibited a peak at intermediate velocities. The friction coefficients for freshwater and saltwater ice were almost indistinguishable at higher temperatures (-3 C and -10 C), but saline ice had lower friction at lower temperatures. The results are explained in terms of frictional heating, creep and fracture.
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:
A new theory, in which friction is interpreted as the energy flux required to form surface at contact asperities, is applied to sliding on ice and snow. The results of this theoretical investigation show that in dry friction the relevant contact areas are of almost molecular scale. The properties of the interface layer in ice and snow friction are poorly known, so that the implications of this new theory are somewhat speculative. However, qualitative agreement with experimental data is good, and the theory provides explanations to the success of some empirically developed methods of improving the frictional properties of skis and sledges. -Author
Official statistics indicate that slipping is one of the most common causes of accidents. Falls contribute to about 40% of the 4000 fatal accidents that occur annually in Sweden. In fact, falls are more common than motor vehicles as a registered cause of accidental deaths. During 1975 occupational injuries caused approximately 3 million sickness-days and 26% of them were due to falling accidents. The actual involvement of skidding cannot be evaluated, because slip-ups have been registered only as a subgroup of “falls on the same level”. However, skidding may initiate other types of accidents as well. This is supported by preliminary data from a new occupational injury information system. The computer based system allows selective retrievals. In one of the first outputs slip-ups are involved in at least 25 accidents out of 102 including “fall to a lower level” during house construction work. Thus it is urgently necessary to improve the slipping resistance of shoes, floors and walking surfaces. Development is guided by friction measurement with different kinds of apparatus. Unfortunately, many of these are based on an oversimplified theory of static friction, which seems to be quite irrelevant due to the viscoelastic properties of shoe soles and heels. However, even if the apparatus measures dynamic friction, tests must be performed with forces and motions closely resembling a real human skid. Otherwise, friction measurements and real slipping resistance will be poorly correlated.
A recently invented walking traction test method was chosen to measure the coefficient of friction (c.o.f.) of thirteen pairs of discarded working footwear. Floor surfaces were lubricated with a water-based wetting agent and four grades of mineral oil. The footwear were also tested on wet and dry ice. The maximum c.o.f. attained prior to each slip was recorded whilst walking forwards and again whilst walking backwards on the heels.Results for the thirteen footwear samples were ranked in descending order of c.o.f. for each floor and lubricant combination, and rank orders for the seven most slippery surfaces were compared. Kendall's coefficient of concordance W = 0.73 for walking forwards and 0.79 for walking backwards; P < 0.001. Rank orders for each of the seven surfaces were also compared with mean rank orders. Correlation coefficients r, all reached or exceeded 0.92 (P < 0.005) on rough plastic and stainless steel coated in 121.4 or 88.2 cSt oil (at 17.5°C) and on water lubricated glazed white tiles. On dry ice, r = 0.49; P < 0.05. The correlation between mean rank orders of footwear on forward and backward walking was 0.95; P < 0.005.The c.o.f. recorded whilst walking backwards was 37.7% lower than the forward walking c.o.f., supporting the hypothesis that dangerous slips are likely to occur on heel strike. There was also a significant correlation between roughness of soling and c.o.f.; P < 0.01.This method of measuring c.o.f. is now being applied to eliminate the most slippery footwear with the long-term aim of selecting the safest solings for specific environments.
The recommendations made after the analysis of accidents following an incident of slipping often include the use of anti-slip footwear and/or the installation of an anti-slip floor covering. Such recommendations make it necessary to study biomechanical and tribologic phenomena that occur during slipping, in particular in order to develop criteria for the evaluation of the slip resistance of footwear and floor surfaces. Consequently, research which deals with the prevention of slipping is more or less directly related to the methodology of measuring slip resistance, and can have many objectives, including:1.the study of the conditions or accident-related factors encountered at the time of slipping in an industrial context;2.the analysis of the dynamic of slipping at the interface between a slippery floor and the foot;3.the analysis of tribologic phenomena that occur at this interface;4.the choice of a relevant criterion to assess the slip resistance; or5.the development of a test bench.The results of these studies can be used to express preventative recommendations or to support/discuss standardisation projects on the measurement of the slip resistance of protective shoes or floor coverings. Globally speaking, these studies have contributed to a better understanding of the complexity of slips and of their prevention, and it is for this reason that they are reviewed in the current paper. Special emphasis will be placed on the differences observed between the different approaches rather than on the multitude of (occasionally contradictory) results obtained from them. This literature review has allowed us to partially explain the reasons that slow down progress in harmonising methods for the measurement of slip resistance, and also to explain the more recent studies on perturbed locomotion or posture. These studies have been undertaken on the strategies used to confront the risk of falling or to cope with the loss of balance.
The coefficient of kinetic friction of 49 types of footwear was determined using a prototype apparatus simulating actual foot slippage on dry and wet smooth ice at surface temperatures of − 10° C and 0° C, respectively. The effects of soling material type, hardness, and tread design on the frictional properties were assessed in particular. In addition the effect of strewing sand on ice was studied. The fundamental mechanisms of the friction of polymers on ice are discussed briefly in the paper.The properties of ice had the greatest influence on the coefficient of kinetic friction, and hence, slip resistance. Of the assessed footwear, over 90% was classified as very slippery on wet ice, and 60% as slippery on dry ice. Five footwear types were slip-resistant on dry ice but only one on wet ice. None were slip-resistant on both wet and dry ice. Soft heel and sole materials (Shore A < 60) of thermoplastic rubber with a cleated area as large as possible are recommended for winter footwear on dry ice. For wet ice, however, new developments are needed, e.g. very hard (Shore A > 85) soling materials with sharp cleats in combination with a softer base material. Strewing sand on ice improved the slip resistance to a safer level, particularly on wet ice.
Slips and falls on icy roads often result in fractures or sprains and is a major problem in Nordic countries. Walking trials by 25 subjects wearing four types of winter shoes on five different icy walking surfaces provided subjective and objective measures of tendency to slip and number of slips, respectively. Since friction is a major determinant of a slip, the influence of material spread on icy surfaces, the surface temperatures and the shoe soling characteristics versus the Coefficient of Friction (COF) of the shoes were measured. Sand and gravel on icy roads had positive effects on improving COF. The study revealed that the aetiology of slips and falls is multi-faceted and attempts to solve the problem must adopt a systems approach. Perception of risk, aging, training, experience and postural balance are other factors to be considered in preventing slips and falls. Future research should concentrate on the degree of impact of each factor to the aetiology of slips and falls, which can help to decide priority action in preventing slips and falls.Relevance to industryThe personal protective devices used by outdoor workers during winter season have to provide two types of protection, namely, protection from an occupational hazard and protection from the cold climate. Safety shoes used on snow or ice covered surfaces add a third type of protection, namely, an anti-slip quality of the shoe. The 3rd protection can be achieved from among other things, by improving the friction of the shoe soles.
The objectives were to identify risk groups, risk environments, contributory factors, and consequences with regard to non-fatal pedestrian injuries in a defined population. The study group comprised all patients living in the county of Västmanland, Sweden, who had visited a physician or dentist because of non-fatal injury during one year. Pedestrian injuries were found to account for 41% of all injuries in the traffic area. The greatest risk of sustaining an injury was faced by females aged 50 years or older, and by males aged 10–29. Wintery conditions were clearly associated with increased injury rates, with 51% of injuries incurred during November to January. Falls were involved in 82% of the injuries, mostly from slipping, particularly in urban areas. Fractures were more common among persons aged 50 or older, while sprains predominated at younger ages. Persons who had slipped often made more than one visit to a hospital emergency department, and were hospitalized more often than those who had stumbled.
Climatic conditions may affect the incidence of fractures and fall deaths. Analysis of national fatality data shows that among white women, those living in colder climates have higher rates of fall deaths. Fall deaths increase in winter in all regions, but especially so in colder states. In a prospective cohort study of 96,506 predominantly white female nurses 35-59 years of age, we found that, after controlling for personal and lifestyle characteristics, those women residing in colder climate also had a higher incidence of hip and forearm fracture. In colder states, fracture rates were substantially higher in winter than in summer. A cold climate appears to be a significant risk factor for both fractures and fall deaths among white women, particularly as they age.
An apparatus to measure the coefficient of kinetic friction (mu k) between the shoe sole and the underfoot surface was constructed, and a method including criteria to evaluate the risk of slipping during walking was developed. The apparatus is a prototype stationary step simulator capable of simulating the movements of a human foot and the forces applied to the underfoot surface during an actual slip, and the drainage capability of the contact surface between the shoe sole and the flooring when different lubricants or contaminants are used. The apparatus consists of a movable artificial foot controlled by a computer with the aid of three hydraulic cylinders. The frictional force (F mu), the normal force (FN) and their ratio (mu k = F mu/FN) are measured with a two-way force platform when the foot slides along its surface. Two separate gait patterns, heel-side (mu k 1) and sole-slide (mu k 2) gait pattern, are used for the evaluations. The method classifies studied shoe, lubricant and underfoot surface combinations into five slip resistance classes according to the measured mu k 1. The slip resistance assessments are specified with some complementary safety criteria, e.g., the ratio mu k 1/mu k 2. The reliability of the developed measurement method was assessed in an international comparison test. According to available results discussed in this paper, our method seems to be valid and the slip resistance measurements seem to be repeatable.
A field trial of footwear was commenced 5 years ago to try and find the most suitable boots to prevent slipping accidents on floors contaminated with mineral oil. After preliminary trials nitrile rubber (NR) and microcellular polyurethane (PU) were selected for comparison. Boots soled and heeled with these materials were worn by 12 volunteers for periods of up to 2 years. Friction was measured at intervals throughout the trial by determining the angle of slip on an oily steel plate.Smooth, wet or oily floors caused polishing of the soles, whereas loose metal chippings on the floor roughened the surface and improved friction. Microcellular PU resisted polishing better than NR and had a longer life.In the final phase of the trial, volunteers who had tested NR boots wore PU and vice versa. A direct comparison of the two materials tested by seven volunteers revealed that PU always produced higher angles of slip than NR. Mean coefficient of friction (COF) for PU was 0·26 and for NR was 0·18.The COF of PU boots improved between the first and second test, indicating that the smooth surface of new boots reduces friction and should be abraded before use.We conclude that microcellular PU is the best material tested to date for boots used on floors contaminated with mineral oil.
Relatively few occupational epidemiological studies have been conducted concerning the association between cold ambient temperatures and cold exposure injuries, and fewer still of traumatic occupational injuries and cold ambient temperatures.
The association of ambient temperature and wind data from the National Climatic Data Center with injury data from mines reported to the Mine Safety and Health Administration (MSHA) was evaluated over a 6 year period from 1985-1990; 72,716 injuries from the seven states with the most numerous injuries were included. Temperature and wind data from each state's metropolitan weather stations were averaged for each day of the 6 year period. A weighted linear regression tested the relationship of ungrouped daily temperature and injury rate for all injury classes. For cold exposure injuries and fall injuries, relative incidence rates for grouped temperature data were fit with Poisson regression.
As temperatures decreased, injury rates increased for both cold exposure injuries and slip and fall injuries. The association of slip and fall injuries with temperature was inverse but not strictly linear. The strongest association appeared with temperatures 29 degrees F and below. The injury rates for other accident categories increased with increasing ambient temperatures.
This study suggests that statewide average ambient temperature reflects the expected association between the thermal environment and cold exposure injuries for workers, but more importantly, documents an association between ambient temperatures and occupational slip and fall injuries.
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.
Inter-record linkage between two Swedish databases on population and injury was effected to provide information on occupational slip, trip and fall (STF) accidents. The text descriptions in more than 1600 accident reports from occupational groups with high incidence rates of STF accidents were categorised by gender and age and the factors contributing to the accidents studied. Both older male and female workers had higher rates of reported STF accidents than younger workers, but it was established that within any one occupation the workplace hazards were common to all. Both for men and for women, the initial approach to the prevention of STF accidents should be to improve orderliness in the workplace.
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.
Friction has been widely used as a measure of slipperiness. However, controversies around friction measurements remain. The purposes of this paper are to summarize understanding about friction measurement related to slipperiness assessment of shoe and floor interface and to define test conditions based on biomechanical observations. In addition, friction mechanisms at shoe and floor interface on dry, liquid and solid contaminated, and on icy surfaces are discussed. It is concluded that static friction measurement, by the traditional use of a drag-type device, is only suitable for dry and clean surfaces, and dynamic and transition friction methods are needed to properly estimate the potential risk on contaminated surfaces. Furthermore, at least some of the conditions at the shoe/floor interface during actual slip accidents should be replicated as test conditions for friction measurements, such as sliding speed, contact pressure and normal force build-up rate.
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