Pseudo Stress Response in Kolsky Tension Bar Experiments

An abnormal stress peak was measured in the specimen response in a Kolsky tension bar experiment. Efforts in changing specimen gage length and applying Teflon tape on the threads of both the specimen and the adapters have been conducted to address this stress peak which was found to be pseudo. The pseudo stress peak was caused by the interfacial impact of the threads on the specimen and the bar ends and must be removed from the intrinsic stress response of the specimen material. Higher impact speeds result in higher amplitudes in the peak stress. The peak stress can be significantly reduced by applying Teflon tape on the threads. At a certain strain rate, it becomes more efficient to minimize the peak stress by simultaneously using a specimen with a shorter gage length and applying Teflon tape on the threads.