Tensile Testing with Vessel for Pressure Dependency Evaluation of Viscoelasticity of Biological Soft Tissue

Abstract

The mechanical behaviors of solid-liquid two-phase materials are affected by environmental conditions because of the moist structure of the materials. Therefore, material tests to investigate the solid-liquid interactions in these materials should be conducted by considering various conditions such as multiaxial stress, temperature, and fluid concentration. Here, the deformation of biological soft tissues having high liquid content is also dependent on multiaxial conditions including hydrostatic stress. However, it is difficult to evaluate the condition dependency of tissues because no equipment has been developed to realize low-load sensing under hydrostatic stress conditions. In this study, a pressure vessel for a tensile testing system is developed to evaluate the pressure dependence of biological soft tissues. This vessel can be attached to the tensile testing system that can be used to evaluate the viscoelasticity of tissues. A non-friction sealing system with a film on the vessel wall is adopted to measure the load; this load is verified by carrying out a tensile test with a linear spring under pressure conditions. In particular, the error caused by the opened/closed condition of the vessel is calibrated by the verification results, and the load applied to the specimen is precisely measured by using the tensile system with the pressure vessel. After the calibration, a tensile test for biological soft tissue is carried out under varying pressure conditions. The experimental results indicate that the stress-time curves for each condition exhibit good agreement and the tensile system with the pressure vessel has good applicability to evaluate the pressure dependency of viscoelastic behavior.