Improvement of Drop-Hammer Compression Test for Rubber Material

Abstract

The drop-hammer compression testing method where the stroke is calculated by solving the equation of motions of the drop-hammer and anvil was improved in order to determine the strain-rate dependence of the elastic modulus of rubber material. An additional tool for interrupting the compression was embedded in the apparatus. The tool was a thick washer which informed the time when the prescribed compressive strain was achieved by the sharp increase of compression force. The oscillatory stress-time curve obtained by the load cell was appropriately smoothed employing the method of moving average. The effect of the friction at the interface between the rubber specimen and the tools was properly eliminated by the extrapolating method using the specimens with several variations in heights. The stress-strain relationship was obtained under the dynamic condition. The numerical simulation of impact compression disclosed that the effect of inertia on the deformation pattern was practically small under the experimental condition adopted. Conducting the low-speed compression tests, the dependence in elastic modulus of rubber material on the strain-rate was appropriately determined.