Effect of scragging on parameters in viscoplastic model for filled rubber

Abstract A simple viscoplastic model for the stress–strain behaviour of filled rubber is presented. It consists, for a given strain, of additive contributions to stress from hyperviscoelasticity and time independent hysteresis. Rubber components are often subjected to scragging, i.e. preconditioning to a large strain, before carefully assessing their load deflection behaviour and comparing it to specification. The choice of scragging strain, however, affects the load deflection behaviour. It is found that this effect may be approximately captured, for modelling purposes, by regarding the modulus of the time-independent hysteresis contribution to be a function of the scragging strain and the time elapsed since scragging.