Numerical and experimental characterization of a rubber damping tool component

Abstract

As computer technology develops, one can simulate more complex systems by using CAE-software. Sandvik Teeness, a world leading manufacturer of damped machining tools, wants to investigate the possibility of utilizing CAE tools in their product development process. As part of initiating this long term goal, a feasibility study investigating how to describe the intrinsic parameters in an EPDM Shore A 70 rubber has been conducted. The main objective of this thesis was to obtain material parameters from a few chosen experimental tests and evaluate their applicability in FEA simulations, both for low and high strain-rate load cases. A combination of both standardized tests and new test procedures for rubber evaluation have been attempted to obtain suitable parameters for numerical simulations. The low strain-rate material parameter's change with increased vulcanization times has been evaluated and commented on, in addition to recording the shrinkage rates for the various curing times. The performed dynamic test has been reproduced using both axis-symmetric and solid modeling, and the models were simulated using direct-integration implicit dynamics and linear perturbation methods respectively. Material stiffness has been described using both hyper-elastic material models and constant values for both the dynamic and static E-modulus. Combined with stiffness-proportional or structural damping mechanisms the models have been attempted fitted for numerical simulations, and its respective stiffness/damping combination's applicability has been evaluated. Test procedures have been evaluated and improvements have been suggested to reach a higher degree of accuracy.

Results presented in this thesis show that for small fixed vibrations where both excitation and response amplitudes are known, both stiffness proportional and linear damping mechanisms can be used to simulate the rubber's magnitude of response where low accuracy is needed. Results however show that the non-linear viscous strain-rate dependency must be derived to sufficiently describe the behavior of rubber subjected to vibrations of various magnitude and frequency. The intrinsic parameters changes considerably when vulcanized, and the preferred curing time is stated as three hours at 165 degrees Celsius for these types of specimens.