SIMULATION OF NONLINEAR VISCO-ELASTICITY

CAE has been applied for the development of various industrial products in many kinds of fields. They are not only products made of metals but also products made of polymeric materials, such as tires, balls for various kinds of sports, press ink rolls, and so on. These materials, such as rubber and synthetic resin have viso-elastic properties. And most of them have nonlinear characteristics. In case of dealing with them, it is very important for accurate simulation to apply nonlinear visco-elasitc material models. Especially it is necessary in the field of Impact. Because impact is in the condition of large strain, or high-speed strain rate, performances as products depend on nonlinearity. Therefore it is not reasonable for the simulation of impact to input material properties measured by visco- elastic spectrometer well known as a typical visco-elastic measurement. They are in the condition of small strain on the order of few percent and low strain rate on the order of a few [/s]. It is necessary to measure them in large strain on the order of more than ten percent and high strain rate on the order of thousands [/s] same as practical condition. However there had not been any testers to measure viso-elastic material properties in the condition of large displacements and high deformation rates before. Recently, the split Hopkinson pressure bar, which is originally for evaluation of metals, has been improved for evaluation of polymeric materials. And material properties of some polymeric materials in that condition have been evaluated. In this study, a nonlinear visco-elastic material model is developed by using the measurement results from the improved split Hopkinson pressure bar. Further, the tests of the split Hopkinson pressure bar are simulated, and good correlation with the experiment is obtained. Finally the restitution tests of golf ball is simulated as an example of application. Agreement between the experiment and the simulation is confirmed.