An Integrated Transient and Steady-state Adhesive Wear Model

Wear coefficient is an important wear parameter. However, its value is often determined from wear tests which are conducted without taking into account both their transient wear and steadystate wear. This has resulted in wear coefficient values varying greatly from one case to another when they are determined by different investigators, making meaningful comparison difficult. Research work done recently has found that more consistent steady-state wear coefficient values would be obtainable with the application of an integrated transient and steady-state adhesive wear model. Figure 1 shows that a wear volume versus distance curve can be divided into two regimes, the transient wear regime and the steady-state wear regime. The volume (or weight) loss is initially curvilinear and the rate of volume loss per unit sliding distance decreases until at P where it joins with the straight line PQ. The amount of volume loss in the regime given by OP is the transient wear and PQ is the steady-state wear. The standard method to calculate the wear coefficient is to make use of the total volume loss and the total sliding distance covered. Hence the standard wear coefficient value obtained from a volume loss versus distance curve is a function of the sliding distance. Due to the higher initial running-in wear rates, it has a higher value initially and will reach a steady-state value as shown in Fig.3. This practice would therefore give a higher steady-state wear coefficient value since the higher wear rate from the transient wear is included in its computation. Furthermore, it is sometimes difficult to decide whether the steady-state wear has actually reached in an experiment.