No abstract

Most mechanical systems (in particular, gear transmission system) undergo relative motion which results in increased friction phenomenon (friction coefficient, stresses, and wear rate) and thereby results in loss of efficiency. Mechanical parts undergo relative motion in different geometry configurations and orientations that induce a different state of stress as a result of friction. Till date, attempts are being made to minimize the friction with full sphere pin geometry configuration. The present work focused to reduce the frictional and wear rate, and experiments are conducted with tribo-pairs. i.e., nickel-coated pin surface slide against Al6061 alloy disc. The friction studies are carried out at different loads and geometries of pin surfaces (sphere and hemisphere configured at different orientations such as full sphere and hemisphere configured at 0°, 45°, and 90°) to induce different stress states with reference to sliding directions. Change in the geometry of EN8 pin material and their orientation with reference to sliding direction resulted in a different state of stress. The resulting stress levels were examined under the scanning electron microscope, which revealed the mechanisms of adhesion, abrasion, and extrusion. At a lower magnitude of orientation and load, the extent of asperity breaking lessens and material removal from pin surface decreases. Abrasion wear mechanism was observed corresponding to full sphere configuration on Al 6061 disc, whereas adhesive wear mechanisms are seen with hemisphere pins. The amount of aluminum transfer on pin surface with a hemisphere pin is comparatively more than that of full sphere configuration. At a lower magnitude of state of stress, the mechanism of sliding was dominated by the adhesion effect. At a higher level of state of stress, the mechanism of sliding was dominated by abrasion and extrusion.

In the present study, experiments have been carried out by sliding hard elastic material on ductile flat surface. The different state of stress has been achieved by changing the geometry of hard material and different orientation of changed geometry with respect to sliding direction. Experiments have been carried out using pin on disc wear test rig. The tests were conducted with Al6061 alloy disc and EN8 alloy steel pin with different tip geometries and orientations. The obtained results revealed that coefficient of friction was higher at lower loads compared to higher loads in hemisphere pin geometry. An exception has been found at 90° orientation at low loads. It has been attributed to adhesive effect. The state of stress and its configuration with respect to direction of sliding was found to influence the sliding phenomenon. Micrograph studies revealed damages due to adhesion, abrasion and extrusion.