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For understanding the long term fretting mechanism, the effect of normal force on the fretting wear behavior of 690 TT heat transfer tube against 304 stainless steel (SS) ball in simulated secondary water with 10 6 total fretting cycles was studied. The changes of the friction coefficients can be divided into five stages: small and slowly increase stage, sharply increase to a peak point, dramatically decrease to a steady value, steady stage, and continuously increase stage. And the friction coefficient decreases with the increase of the normal force. The morphologies of the worn scars under different normal forces are quite different. A stratified layer structure is formed on the 690 TT surface during the fretting wear process when the normal force is 60N. [ABSTRACT FROM AUTHOR]

The friction between an elastomer and a rigid substrate may depend on a large number of system and loading parameters. Based on a general structure of the law of friction, we propose a generalized master curve procedure for elastomer friction where the significant governing parameter – indentation depth (or normal force) was taken into account. Unlike the generation of the classical master curve by horizontal shifting of dependence “friction - logarithm of velocity” for different temperatures, in the case of various indentation depth the shifting in both horizontal and vertical direction is required. We experimentally investigated coefficient of friction of elastomer on sliding velocity for different indentation depths and temperatures, and generated a ‘master curve’ according to this hypothesis. [ABSTRACT FROM AUTHOR]

This paper studies the tribocorrosion behaviour of Ti-6Al-4 V in phosphate buffered saline under reciprocating frequencies of 1, 5, 10, 15, 20, and 25 Hz at different normal forces of 3.5, 6, 10.8, and 17.5 N using a customised ball-on-disk test set-up. The tribocorroded scars were then post-assessed by scanning electron microscopy and energy dispersive x-ray spectroscopy, atomic force microscopy, profilometry, and confocal microscopy. The results demonstrated a unique pattern for the total volume loss versus frequency such that the loss was maximum at 5 Hz with a subsequent reduction from 5 to 15 Hz, and a final stabilisation beyond 15 Hz. Compared to the total and chemical losses, mechanical volume loss showed more significant variations with frequency. The results indicated complex interactions between the normal force and frequency in relation to the total material loss from the alloy. These findings challenge the general understanding of an increase in the total loss with increasing frequency. • Tribocorrosion of Ti-6Al-4 V was studied under various normal forces and frequencies. • Variations in total material loss with frequency with a maximum occurring at 5 Hz. • Mechanical part of total material loss was more sensitive to changes in frequency. • Complex interactions between normal force and frequency determined the total loss. [ABSTRACT FROM AUTHOR]

Abstract: A method for measuring the coefficient of friction between sliding solid bodies has been developed. In the proposed method, both frictional and normal forces are measured as inertial forces acting on masses. Two pneumatic linear bearings, one placed horizontally and the other vertically, are used to realize a linear motion with a sufficiently small friction acting on the masses, i.e., the moving parts of the linear bearings. The inertial force acting on each mass is calculated from the velocity of the mass; this velocity is determined with a high accuracy by measuring the Doppler shift frequency of a laser light beam that is reflected off the mass using an optical interferometer. The performance of the proposed method is demonstrated by measuring the coefficient of friction between a car wiper blade and a glass surface. [Copyright &y& Elsevier]

The fluid flow in cluster magnetorheological-porous foam finishing method (CMRFF) was studied for planner finishing in this study. A normal force model composed by magnetic and hydrodynamic force was established for CMRFF. The normal force is generated by the integral of pressure distribution on workpiece surface and the average relative error between theoretical and experimental results is less than 5.737%. CMRFF can achieve much higher normal force compared with traditional cluster magnetorheological finishing method (CMRF). In the finishing processes of silicon wafer, the surface roughness reduced from 49.66 nm to 16.991 nm in CMRFF in 45 min, compared with 50.559 nm–22.891 nm in CMRF, which indicates the effectiveness of CMRFF in improving surface finishing rate and quality. • A normal force model composed by magnetic and hydrodynamic force is built for CMRFF. • Fluid flow of MRPF in porous foam enhances the normal force in CMRFF process. • Porous foam reduces the adverse effect of centrifugal force on MRPF. • Shear elastic layer thickness considers magnetic field and centrifugal effect. • CMRFF effectively improve the surface finishing rate and quality compared to CMRF. [ABSTRACT FROM AUTHOR]