A modified Kolsky bar system for testing ultrasoft materials under intermediate strain rates

A 25 mm aluminum Kolsky bar is modified to test ultrasoft materials under intermediate strain rates (10-100 s(-1)). In this modified system, an ultralong loading pulse (5-50 ms) is generated using an 800 mm steel striker in combination with a pulse shaper made of 2.5 mm thick soft rubber. For such long loading pulses, the traditional data reduction scheme based on strain gauge measurements is not possible. We use a laser gap gauge to measure the deformation of the sample directly and monitor the low amplitude dynamic loading stresses on the sample with a pair of piezoelectric transducers that are embedded in the bars. A commercial foam rubber is tested to demonstrate the feasibility of our modified Kolsky bar system.