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28 ReferencesThe effect of surface roughness and contaminant on the dynamic friction of porcelain tile
Abstract
Surface roughness affects friction, but it is not clear what surface roughness characteristics are better correlated with friction. The average of the maximum height above the mean line in each cut-off length (Rpm) and the arithmetical average of surface slope (deltaa) had the highest correlation with dynamic friction coefficient in a previous study. The previous study was expanded to two different footwear materials and four different contaminants on a porcelain tile in the current investigation. The results showed that dynamic friction decreased as the interface speed and glycerol content in the contaminant were increased due to the hydrodynamic lubrication effect. Deltaa had the highest correlation with friction for most of the test conditions with neolite. For Four S rubber, friction coefficient appeared to have the highest correlation with the parameters related to the surface void volume at 30% glycerol content, related to the surface slope at 70 and 85% glycerol contents, and related to the peak to valley distance at 99% glycerol content. A good indicator of surface slip resistance probably should consist of the surface parameters representing the surface slope, the surface void volume and the surface peak-to-valley distance with the coefficients determined by the system parameters.
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- ReferencesReferences28
- Li, Chang, and Leamon [22] and Chang [34] discussed the effects of floor roughness under both dry and liquid contaminated conditions. The roughness on the floor surface also affects the friction on the floor when there are solid particles due to possible interlocking effects [24, 26].
[Show abstract] [Hide abstract] ABSTRACT: Solid particles on the floor, both dry and wet, are common but their effects on the friction on the floor were seldom discussed in the literature. In this study, friction measurements were conducted to test the effects of particle size of solid contaminants on the friction coefficient on the floor under footwear, floor, and surface conditions. The results supported the hypothesis that particle size of solids affected the friction coefficient and the effects depended on footwear, floor, and surface conditions. On dry surfaces, solid particles resulted in friction loss when the Neolite footwear pad was used. On the other hand, solid particles provided additional friction when measured with the ethylene vinyl acetate (EVA) footwear pad. On wet surfaces, introducing solid particles made the floors more slip-resistant and such effects depended on particle size. This study provides information for better understanding of the mechanism of slipping when solid contaminants are present.- 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.- The significant correlation between the surface roughness and DFC values under the lubricated condition clearly supports the main theory of the role of floor surface roughness on slip resistance performance in this study. This result is consistent with previous studies reporting functional relationships between the surface roughness and DFC values under contaminated conditions (Chang, 1999Chang, , 2001 Manning and Jones, 2001). However, the lack of correlation between the surface roughness and DFC values under the clean-and-dry surface condition indicates involvement of multiple mechanisms of slip resistance properties and possible strong effects of other material characteristics such as wear development during the dynamic friction tests.
[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.- They found that the wear rate exhibits no significant correlation with the scribed groove angle, and that the wear rate increases with increased roughness. Wen-Ruey Chang [12] [13], investigated the effect of roughness on the coefficient of friction of some footwear materials against porcelain tile and quarry tile. He used 22 surface roughness parameters to find correlation between coefficient friction and surface roughness.
[Show abstract] [Hide abstract] ABSTRACT: In this study, effect of counterface roughness on dry sliding wear of polyoximethylene (POM) and polypropylene (PP) against stainless steel discs (HRC 52) is investigated. A pad on disc tribotester was used. Cylindrical surfaces of discs were used as wearing surfaces. Polymer specimens were produced as cylindrical pins. One of end faces of each pin was formed in the same radius of the discs. Normal force and sliding speed were constant. Roughness of the discs was produced by cylindrical grinding. Very low roughness values (mean of profile deviations Ra < 0.15 μm) were produced by using SiC emery paper after grinding. Ra parameters of the discs were measured both in axial (perpandicular to grinding traces) and circumferential direction (parallel to grinding traces). Average radius of curvature of the asperities Rav was computed by numerical analysis using raw surface profile data obtained from roughness measurements. Axial roughness measurements were chosen to illustrate the variation of wear rate and coefficient of friction with counterface roughness. Axial Ra values were varying from almost 0.1 – 3 μm. Disc surfaces were observed using an optical microscope. Worn polymer pin surfaces were observed by a Scanning electron microscope (SEM) to investigate wear mechanisms. SEM micro-photographs of the pins which worked against counterfaces with an axial roughness Ra = 0.3 μm and Ra = 3 μm were taken. As a result, it was seen that steady state wear rates of POM and PP increase with increasing disc surface roughness, and that circumferential Ra parameter may be effective to explain the interesting variation of wear rate with axial Ra , for axial Ra = 1–2.5 μm. PP and POM were observed to form no transfer film on the counterfaces. According to the SEM micro-photographs, for axial Ra = 0.3 μm some fatigue cracks were observed on the wear surface of the POM pins. For axial Ra = 3 μm, for both polymers, traces which were evident of abrasive wear, tearing and wear debris which was irregularly shaped particles were observed. It was investigated whether the relationship between wear rate and Rav conforms to the “fatigue wear model” of Hollander and Lancaster. In this investigation, asperities on the disc surfaces were assumed to have hemi-cylindrical shape and the radius of the hemi-cylinder is taken as Rav calculated from axial roughness profiles. It was seen that the results obtained for axial Ra = 0.1–1 μm, conform to the fatigue wear model.- Measurement of the COF between footwear material and floor has been the subject of much research (Stevenson et al., 1989; Manning et al., 1990; Gr€ onqvist, 1995; Leclercq et al., 1995; Chang and Matz, 2001 ). Extensions of friction measurement to roughness measurement have also been reported (Gr€ onqvist et al., 1990; Manning and Jones, 2001; Chang, 1998 Chang, , 1999 Chang, , 2001 Chang, , 2002a Chang et al., 2001a). In addition to friction and roughness measurements, subjective measurement has also been discussed (Swensen et al., 1992; Myung et al., 1993; Cohen and Cohen, 1994a,b; Gr€ onqvist et al., 2001).
[Show abstract] [Hide abstract] ABSTRACT: 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.- It is generally believed that rougher floors provide higher friction than smoother floors. The effects of floor roughness have been discussed by Chang (1998, 1999, 2001, 2002a) and Chang et al. (2001a). It is common that floor tiles embedded grit to form a spiked surface.
[Show abstract] [Hide abstract] ABSTRACT: The factors affecting the slip-resistance of footwear such as footwear and floor materials, floor surface conditions, floor roughness, and shoe sole tread design have been discussed in the literature. However, most of the investigations were conducted using new footwear and floor materials. Theoretically, shoe sole materials change after repetitive exposure to the sun and rain during normal usage. Sliding of shoe sole on the floor results in the wear-out the tread patterns. Repetitive impact of shoe sole on the floor may also result in physical properties change. The hypotheses of this project were that footwear usage result in reduction in slip-resistance which could lead to higher likelihood of slip & fall incidence and the reduction in slip-resistance is footwear material-dependent. The objectives of this study were to test these hypotheses. Twenty male subjects, split into two groups evenly, were recruited and tested in a footwear usage experiment for six months. One type of footwear will be assigned to each group. The roughness, abrasion, and slip-resistance of the shoe sole of the new and used shoes were measured and compared. The effects of footwear usage on slip-resistance for two types of shoes tested were discussed along with the consideration of the changes in physical properties such as hardness, abrasion, and tread patterns. The results of the study show that the hardness and abrasive values of the shoe soles did not change significantly after a six month usage. The tread pattern, or sole-floor contact area, and the coefficient of friction of the used shoes were significantly different from those of the new shoes.
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