On Preconditioning and Stress Relaxation Behaviour of Fresh Swine Skin in Different Fibre Direction

This paper presents our recent research results on the preconditioning effects and stress relaxation behaviour in fresh swine skin. The experiments aimed to observe the viscoelastic properties of the tissue. Uniaxial cyclic tensile loading and stress relaxation tests were performed on the skin samples in two different directions to study the effects of fibre direction on mechanical properties. In relaxation tests, tissue 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 the stress relaxation tests. Fibre direction effects were demonstrated in results of cyclic preconditioning as well as stress relaxation tests. The reported strain-independent behaviour in stress relaxation only occurred at certain strain levels. The skin tissue had similar stress relaxation characteristics with strain of 5% and 10%. The stress relaxation phenomenon implies the strain-independency only appeared in samples below 15% strain. All samples exhibited greater stress decaying rate in the first 200 sec of the relaxation period, and began to approach steady decay after 200 sec. The modelling that applied quasi-linear viscoelastic theory and reduced relaxation function has adapted the experimental data sufficiently. This study is a significant step towards understanding the skin rheological behaviour and its multidiscipline properties in the future.