An experimental study and modeling of loading and unloading of nonlinear viscoelastic contacts

The latency model is an analytical model for describing the behavior of nonlinear viscoelastic contact interface in robotic grasping and manipulation. The latency model is based on experimental observation of viscoelastic materials which exhibit the behavior of both elastic and temporal responses when subject to external force or displacement. It is postulated that such materials display latency in response of external influence by the rearrangement of molecules, holes, and structures in order to achieve an equilibrium state corresponding to the instantaneous loading. As a result, we propose that there are temporal latent activities in progress before the material reaches the equilibrium state. In the previous study [21], the latent activity of strain re-distribution with a prescribed constant displacement was presented using both theoretical modeling and experimental results. In this paper, we build upon this latency model to study the behavior of viscoelastic materials under different loading rates with experimental results. The latency model is employed to explain the behavior of responses of hard and soft viscoelastic materials typically found in robotic contact and grasping.