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The purpose of this investigation was to characterize the dependence of paper-to-paper friction on the sliding direction of the previous slide for various paper grades. Static and kinetic friction forces and coefficients of friction were measured using a friction tester based on the horizontal plane principle. The papers were also characterized with respect to fiber-rising tendency and they were imaged by environmental scanning electron microscopy (ESEM).The results showed that uncoated papers exhibited a behavior where the coefficient of friction rapidly decreased to a low value with repeated slides over the same track in the same direction. When the sliding direction was reversed the coefficient of friction increased and maintained a high level. A term called friction hysteresis is defined to quantify these effects in order to relate the behavior of the coefficient of friction to various characteristics of the paper. ESEM imaging showed that sliding caused fiber ends to rise out of the plane of the paper surface and to align themselves in the sliding direction. A correlation was found between the magnitude of friction hysteresis of the different papers and the total area of the raised fibers. The results suggest that friction hysteresis is due to the interlocking of fiber ends on the paper surfaces and that the degree of interlocking is influenced by the orientation of fiber ends relative to the sliding direction. [Copyright &y& Elsevier]

This paper presents friction tests results of AISI 1006 low-carbon steel and an AISI 52100 bearing steel using a spiral pin-on-disk apparatus. 3 mm diameter pins on two average (0.06 or 0.20 mm) diameters glass particle coated abrasive paper were used. The normal force applied was 20 N, the tangential sliding speed was 0.08 m/s, and the radial pin movement was 20 mm/min. The micro-indentation hardness of the pins was measured before and after testing. In general, the higher the strain hardening, the higher was the friction coefficient. For AISI 1006, which wore in a severe regime, the strain hardening intensity depended on the abrasive particle size. For AISI 52100, which wore in a mild regime, the particle size had no effect. Tests on AISI 1006 exhibited paper loading, but tests on AISI 52100 exhibited abrasive particle fragmentation. [Copyright &y& Elsevier]

During an abrasive wear process with emery paper, the influence of grain size and abrasion duration on the tribological behaviour of textile fabrics were studied with a rotative tribometer for fabrics and an optical hairiness meter, the latter measuring the hairiness quantity on the fabric surface. First of all, the effect of the abrasive material graining on the state of the worn fabric surface is shown. Using a fine grain size leads to a worn fabric at the microscopic scale (fibre). Using a coarse grain size shows that the state of the fabric surface is completely different, since the fibre surface is not worn. Actually, some fibres are partly pulled out from the fabric, then this is an abrasion at the mesoscopic scale (yarn). Afterwards, the results show a cyclic behaviour of the fabric friction relative to the time due to a cyclic change of the fabric surface. Thus, this study brings into light the non-linear surface wear of textile fabrics. [Copyright &y& Elsevier]