Viscoelastic Evaluation of Soft Materials at Subsonic Level by Ball Impact Test

Abstract

Mechanical evaluation of soft material is required in the precise design fields of machines concerning car accident, airplane bird strike, and so on because the inaccuracy of mechanical design causes economic loss. In the design field of crash problems on the soft material, precise analysis of the material at subsonic level is required for practical realization of accurate numerical simulation. Then a shock impact test method for the material at the subsonic level using an airsoft gun is developed to identify the mechanical behavior of the soft material. In the impact test, the viscoelastic characteristics of specimens are evaluated by analyzing the stress response using the extended Hertzian contact theory and wave equation at the moment when a simple ball bullet is shot at the specimen using the airsoft gun. An obvious relationship between quasi-static and impact responses of the specimen is observed subjectively in the experimental results of the test. The deformation resistance modules of impact test method for the specimens at the subsonic level are higher than that of quasi-static examination in all materials. The evaluated viscoelastic relationship is applied to crash simulations of soft material by using the fundamental viscoelastic constitutive equation and the material parameters derived from the impact test, and the simulation is computed using the identified parameters. In the simulated results of impact test using the viscoelastic model applied material behavior of soft material, the deformation behavior of the soft materials can be evaluated for the applicable form to numerical simulation.