Behavior Evaluation of Deformation, Damage and Fracture of Biological Soft Tissue by Using Indentation Test

In this study, two types of indentation tests were used for the observation of deformation behavior of biological soft tissue, because indentation testing is an easy method to manage observation and control of the condition of complex tissue specimens. First, a fundamental indentation test was used to evaluate quasi-static deformation behavior of soft tissue. In the evaluation of the quasi-static behavior, elasticity, damage, and fracture of the tissue were analyzed from the profile of reaction force during the indentation. Ball-impact testing with subsonic indentation velocity was used for the evaluation of dynamic behaviors of soft tissue. In the impact test, the viscoelastic characteristics of specimens were evaluated by analyzing stress response, using extended Hertzian contact theory and wave equations, at the moment when a simple ball bullet shot from an airsoft gun strikes the specimen. In the experimental results of the test, an obvious relationship between quasi-static and impact responses of the specimen were observed subjectively. The results are evaluated to analyze the damage and the fracture of the soft tissue for the objective formulation of tissue mechanics. The plateau behavior of reaction force in relation to stress response was also reviewed, in order to quantify the beginning of tissue fracture.