OBRABOTKAMETALLOV TECHNOLOGY Vol. 24 No. 3 2022 was equipped with. Proximity sensor that the machine is equipped with helped in measuring the speed of the disk (rpm) having least count of 1 rpm with 1 % accuracy. In general, in the compression process pressure on the piston ring varied in the range 2 to 25 bar and temperature in the range 50–200oC with a sliding velocity of 5 m/s. Based on this, ranges of normal load, interface temperature and sliding speed were selected, which are shown in Table 1. Experiments were planned systematically to investigate the effect of input parameters on specifi c wear rates with a wide range of design space. In total, fi fteen experiments were carried out at a 5-kilometer distance without repeating the central run experiment. Sliding velocities were obtained by selecting the track diameter on the disk and corresponding rotation of the disk. Ta b l e 1 Levels of parameters selected to evaluate specifi c wear rate Parameter Low level Moderate level High level Normal load (FN) (N) 20 100 180 Interface temperature (T) (oC) 50 100 150 Sliding velocity (v) (m/s) 2 5 8 Track distance: 5 km Results and Discussion Dry sliding wear characteristics of PTFE composite (a pin material) against SS304 stainless steel plate (a disk material) were performed on a pin-on-disk machine. Experiments were performed as per DoE; normal load, interface temperature, and sliding velocity were varied in the ranges as shown in Table 1. On the pin-on-disk machine, the normal load was applied to the pin by transferring (seesaw arrangement) the weights attached at the other end of the rod. The corresponding temperature was set by turning on the heater and the temperature attained was measured by a thermocouple. The required sliding speed was obtained by selecting the appropriate track diameter on the disk and selecting the corresponding rotation speed of the disk. The test was carried out at a 5-kilometer track distance (approx. 14–17 min). A digital readout for wear, friction force corresponding to process parameters such as normal load, temperature, and disk rotation speed was monitored from the Control panel. The Control panel was attached to a desktop computer. Variation in friction force and wear with respect to test time to cover track distance of 5 km was also monitored on a desktop computer using Windcom software. Experimental matrix with process parameters such as normal load, interface temperature, sliding speed and corresponding results is shown in Table 2. Theoretically, the wear rate was calculated by Eq. 1. However, volume loss was obtained by measuring the weight loss of the pin prior to and following the test. Volume loss is calculated by using Eq. 2. volume loss Specific wear rate = , load sliding distance (1) where mass loss Volume loss = . density (2) An experimental-based mathematical model as shown in Eq. 3 was developed to predict wear rate in terms of normal load (FN), interface temperature (T), and sliding speed (v). The developed model is also
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