Study of effect of specimen thickness, gelatin concentration, normal force and sliding velocity on the stick-slip vibrations of gelatin hydrogel

Soft solids undergo stick-slip instability which is characterized by the velocity weakening effect where interfacial shear stress decreases with sliding velocity. Soft solids show the hysteresis of energy release rate (G) during the stick and slip phase of a stick-slip cycle. In the present study, the effect of specimen thickness on G is studied by conducting the direct shear sliding experiments on gelatin hydrogel and glass substrate. Interfacial shear stress and corresponding crack lengths obtained during the slide-hold-slide (SHS) experiments are used to determine G analytically. Significance of specimen thickness, normal stress, gelatin concentration and sliding velocity on the hysteresis of G during a stick-slip cycle is discussed in detail. Increase in the specimen thickness, normal stress and gelatin concentration lead to an increase in the hysteresis of G as well as tendency of stick-slip instability. However, increase in the sliding velocity leads to decrease in hysteresis.