Contact conditions variation with time challenge the common steady state lubrication characteristic estimations. Wear test devices usually apply a constant load on the contact surfaces. These apparatuses should improve to have the possibility of time variation
condition testing. In this study, a load-varying system has been designed to complete the pin-on-disk wear test device. By adding this system, it is possible to change the load with time in different patterns. The intensity of the current passing through a magnetic
coil mounted on the load lever is controlled by an electronic control unit to produce instance load. Several tests are designed with 10w40 oil as lubricant in the contact between the pin of 100-chrome-6 bearing steel and the ST37 steel disc. Four different patterns of time-varying load, including ascending, descending, sinusoidal, and ascending-descending patterns are investigated. The results show that the variable load created by the system completely affects the contact friction behavior and the type of load change
pattern is effective in the measured friction force. The decrease of friction force is observed in all cases with an increase in the linear speed. It is found that, in a complete cycle the friction coefficient shows a reverse trend with respect to the normal load pattern.