Microscopic observations of the progressive wear on shoe surfaces that affect the slip resistance characteristics

摘要

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, R{sub}a) and root mean square (RMS, R{sub}q) roughness, maximum mean peak-to-valley height (R{sub}(tm)), maximum mean peak height (Rpm), maximum mean depth (R{sub}(vm)), and average asperity slope (△a) 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 R{sub}a 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.