ブタ後ろ足軟組織層の変形挙動のモデル化に関する検討

抄録

External forces on the skin surface are known to cause a pressure ulcer. A compressive force has been studied widely, but a shear force has not been studied enough. The aim of this study is to model and simulate the shear deformation behavior of layered tissues, especially subcutaneous tissue because it deforms easily when it is subjected to the shear on the skin surface. At first, we formulated the kinematic relationships for a simple shear to simulate the deformation behavior of the subcutaneous tissue as a representative one among the layered soft tissues. Secondly, we obtained a shear component of the stress as a function of the strain components. Then we postulated a Mooney-Rivlin hyperelastic model to describe the stress-strain relationship of the shear component explicitly. We also formulated a linear viscoelastic model by assuming a Prony function for a stress relaxation function. Based on the experimental results for porcine soft tissue, which consists of skin, subcutaneous tissue, tendinous tissue and skeletal tissue, we identified parameters in the Prony series of stress relaxation function. Finally, we simulated the time history of stress in the subcutaneous tissue for the simple shear. Our model described a nonlinear time history of the shear stress. The insufficient nonlinearity may be attributed to discontinuous slides which occur simultaneously with the shear deformation in the subcutaneous tissue.