Determination of critical velocity of gelatin hydrogel sliding on a smooth glass substrate

Abstract

Soft solids such as rubbers, elastomers, gels show jerky or intermittent motion called as stick slip while sliding on a hard surfaces such as glass, metals or rocks. Stick slip causes friction induced vibration, squeaking or squealing sound, loss of energy and loss in positional accuracy. Stick slip exists for low sliding velocities and disappears above a certain velocity known as a critical velocity above which steady sliding exists. Critical velocity depends upon the properties of soft solids, properties of substrate, normal stress, specimen height, stiffness of sliding system, surrounding temperature and humidity etc. Hence understanding the effect of these parameters is extremely important to avoid or minimize the effects of stick slip in sliding systems. In the present study, quadratic model is generated for critical velocity in terms of gelatin concentration, normal stress and specimen thickness. Effect of these parameters on the response is discussed in detail and the results are validated with the established trends mentioned in the literature. Finally the spatio-temporal analysis of sliding interfaces has been performed to understand the rupture and healing of the interface during the stick slip as well as steady sliding.