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21 ReferencesThe effect of surface roughness on dynamic friction between neolite and quarry tile
Abstract
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.
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- In fact, the non-linear nature of the friction caused by the complex contribution of each parameter to the frictional properties, in addition to the great diversity of external factors (i.e., surface contaminants, temperature, surface irregularity, etc.), makes it very difficult to develop a mathematical model of the friction between shoe sole and the ground floor. However, since friction is perceived as an important footwear property, an alternative approach was applied to include the friction test in the VSTB: based on previous knowledge (e.g., Li and Chen, 2004; Chang, 1998; Manning and Jones, 2001), a set of key questions were defined in order to allow a qualitative assessment of the friction properties of a sole. These questions refer to, for example, the area of braking, the area of propulsion, the design and placement of the studs, and so on.
- Measurement of kinetics friction is a challenging task. In this research the effective environmental factors in %BW means normalized force by dividing on body weight of each subjectFig. 1 The COF patterns during a normal and drop foot stride in medio-lateral (x) and antero-posterior (y) direction and the absolute component (H and P respectively represent the normal subjects and drop foot patients) Australas Phys Eng Sci Med (2012) 35:187–191 189 shoe interface such as drainage capacity between shoe and floor, viscoelastic mechanical properties of the shoe sole, floor surface roughness [9,272829303132, floor surface waviness [31, 32], and contaminant condition2728293031 which considered to be important by other researchers have been ignored using bare foot. But in this study, the goal was not to quantify the COF in drop foot patients in different conditions; instead the aim was to assess the effect of human factors on shoe-trituration among drop foot patients.
[Show abstract] [Hide abstract] ABSTRACT: The aim of this study was examining the effect of human factors such as plantar friction, contact period time, and impulse on shoe-sole trituration of drop foot patients. Twenty-five patients with drop foot and twenty normal subjects were recruited in the study. The force plate and its related software's recorded human factor (coefficient of friction, ground reaction force, time of stance phase) as time dependent parameters. Dynamic coefficient of friction patterns were categorized based on their magnitude versus time when the longitudinal axis of the sole was plotted as the Y-axis and the transverse axis of the sole as X-axis during stance phase. The result of this research indicated that the average coefficient of friction among drop foot patients is 77.53 % (p value <0.05) lower than the normal subjects. Also the time of stance phase among drop foot patients is 7.56 % (p value <0.05) greater than normal subjects. There is no difference in the peaks, of vertical ground reaction force between normal and control group. The findings of this research revealed that the time of stance phase has a key role in shoe-sole trituration of patients with drop foot.- In fact, because each testing instrument has different concepts, systemic parameters and mechanical principles, it can be misleading to adopt a reference COF value without any citation to the instrument used for the slip resistance measures. Recent studies have highlighted the importance of surface roughness on slip resistance evaluations and measured a number of surface roughness parameters to identify any correlations between the surface coarseness and slip resistance properties (Harris and Shaw, 1988; Proctor and Coleman, 1988; Stevenson et al., 1989; Manning et al., 1991; Proctor, 1993; Manning and Jones, 1994; Grönqvist, 1995; Jones et al., 1995; Rowland et al., 1996; Wilson, 1996; Manning et al., 1998; Chang, 1998 Chang, , 1999 Chang, , 2000 Chang, , 2001 Chang, , 2002 Fendley et al., 1999; Chang and Matz, 2000; Smith, 2000, 2003; Kim et al., 2001; Kim, 2004a,b; Kim, 2006a,b; Kim and Nagata, 2008a,b). As stated in those studies, there are convincing evidences that surface roughness on the shoe and floor surfaces affect slipperiness significantly.
[Show abstract] [Hide abstract] ABSTRACT: Literature has shown a general trend that slip resistance performance improves with floor surface roughness. However, whether slip resistance properties are linearly correlated with surface topographies of the floors or what roughness levels are required for effective slip resistance performance still remain to be answered. This pilot study aimed to investigate slip resistance properties and identify functional levels of floor surface roughness for practical design applications in reducing the risk of slip and fall incidents. A theory model was proposed to characterize functional levels of surface roughness of floor surfaces by introducing a new concept of three distinctive zones. A series of dynamic friction tests were conducted using 3 shoes and 9 floor specimens under clean-and-dry as well as soapsuds-covered slippery wet environments. The results showed that all the tested floor-shoe combinations provided sufficient slip resistances performance under the clean-and-dry condition. A significant effect of floor type (surface roughness) on dynamic friction coefficient (DFC) was found in the soapsuds-covered wet condition. As compared to the surface roughness effects, the shoe-type effects were relatively small. Under the soapsuds-covered wet condition, floors with 50 μm in Ra roughness scale seemed to represent an upper bound in the functional range of floor surface roughness for slip resistance because further increase of surface roughness provided no additional benefit. A lower bound of the functional range for slip resistance under the soapsuds-covered wet condition was estimated from the requirement of DFC > 0.4 at Ra ≅ 17 μm. Findings from this study may have potential safety implications in the floor surface design for reducing slip and fall hazards.- The British Slip Resistance Group reported that measurement of the 'Rz' parameter allow slipperiness to be predicted for a range of common materials [15]. Other studies [16-18] have reported that 'Ra' has a strong correlation with the friction coefficient. It is generally known that the surface roughness of a floor is directly related to slip resistance in the presence of contaminants such as water or oil.
[Show abstract] [Hide abstract] ABSTRACT: To challenge the problem of slipperiness, various slipmeters have been developed to assess slip hazard. The performance of in-situ slipmeter is, however, still unclear under the various floor conditions. The main objectives of this study were to evaluate the performance of three kinds of slipmeters under real conditions, and to find their dynamic and kinematic characteristics, which were compared with gait test results. Four common restaurant floor materials were tested under five contaminants. Slipmeters and human gaits were measured by high speed camera and force plate to find and compare their dynamic and kinematic characteristics. The contact pressures and built-up ratio were below those of subjects. The sliding velocity of British Pendulum Tester was above those of subjects, while those of BOT-3000 and English XL were below those of subjects. From the three meters, the English XL showed the highest overall correlation coefficient (r = 0.964) between slip index and R(a), while the rest did not show statistical significance with surface roughness parameters (R(a), R(z)). The English XL only showed statistical significance (p < 0.01) between slip index and contaminants. The static coefficient of friction obtained with the BOT-3000 showed good consistency and repeatability (CV < 0.1) as compared to the results for the BPT (CV > 0.2) and English XL (CV < 0.2). It is unclear whether surface roughness can be a reliable and objective indicator of the friction coefficient under real floor conditions, and the viscosity of contaminants can affect the friction coefficient of the same floors. Therefore, to evaluate slipperiness, the performance of the slipmeters needed to improve.- Therefore, in order to ensure a safe environment for pedestrians wearing footwear, the slip safety of marble surface coverings should be determined in wet and dry conditions. Previous studies determined that surface roughness was the most important factor affecting slip resistance, as it affects friction in surface coverings [5]. Any increase in the roughness of surface covering also crucially decreases slipping [6,7].
- In fact, the non-linear nature of the friction caused by the complex contribution of each parameter to the frictional properties, in addition to the great diversity of external factors (i.e., surface contaminants, temperature, surface irregularity, etc.), makes it very difficult to develop a mathematical model of the friction between shoe sole and the ground floor. However, since friction is perceived as an important footwear property, an alternative approach was applied to include the friction test in the VSTB: based on previous knowledge (e.g., Li and Chen, 2004; Chang, 1998; Manning and Jones, 2001), a set of key questions were defined in order to allow a qualitative assessment of the friction properties of a sole. These questions refer to, for example, the area of braking, the area of propulsion, the design and placement of the studs, and so on.
[Show abstract] [Hide abstract] ABSTRACT: This paper presents a new virtual-engineering platform, called as virtual shoe test bed (VSTB), for supporting the design of footwear from the engineering point of view. The proposed VSTB system includes various functional design criteria in order to support the definition of the best solution for each product utilising scenarios based on user needs and preferences. Using the proposed virtual-engineering system a designer is able to simulate the behaviour of footwear components and the interaction between shoe and user in order to derive a predictive estimation of the fitting, thermal comfort and performance ratings without the necessity to manufacture and validate physical prototypes. The present paper describes the architecture, the tests implemented in the final system along with corresponding lab experiments conducted in terms of industrial validation. All results and hints for future research are reported and discussed.
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