Study on the three-dimensional stress-relaxation diagram of cattlehide shoe upper leathers

Due to the structural hierarchy of collagen and the fiber weave pattern within skins and hides, leathers exhibit complicated viscoelastic behaviors. In this study, the stress-relaxation behaviors of chrome-tanned cattlehide shoe upper leathers were investigated. A generalized Maxwell model with four units is used to describe the stress-relaxation behavior of leather held at the strains of 23.0%, 30.9%, 37.2%, 42.6% and 51.9%, respectively. A method to get a three-dimensional stress-relaxation diagram with stress–strain–time coordinate is introduced in this paper, from which the stress of leathers at different strain and relaxation times can be predicted. With stress-relaxation measurement of cattlehide shoe upper leathers and a suitable curve fitting, the three-dimensional stress-relaxation diagram of cattlehide shoe upper leathers is built up. This method can also be applied to other solid viscoelastic materials with a suitable curve fitting equation.