The Preconditioning and Stress Relaxation of Skin Tissue

This paper reports our recent study on the preconditioning effects and stress relaxation behaviour of fresh swine skin. Uniaxial cyclic tensile loading and stress relaxation tests were performed with swine skin samples in two different directions to study the effects of fibre direction on mechanical properties. With stress relaxation tests, skin samples were loaded to different strains to observe its effects on stress relaxing over time. Mathematical modelling was performed to compare the data obtained from stress relaxation tests. Fibre direction effects were demonstrated in results of cyclic preconditioning as well as stress relaxation tests. The stress relaxation experimental results indicated that strain and time independency only appears at certain strain levels. The skin tissue has stress relaxation characteristics at strain of 15% and below. Under such strain amplitudes, the samples exhibited greater stress decaying rate in the first 200 seconds of the relaxation period, and began to approach steady decay after 200 seconds. With quasi-linear viscoelastic theory and reduced relaxation function, the modelling has adapted the experimental data sufficiently. This study is a significant step towards understanding skin tissue rheological behaviour and its multidiscipline properties.