Load Cell Ringing in High Rate Compression Tests

Mechanical test machines play an important role in providing simulation data to underpin careful analysis of high rate processes. In many cases elements of the test frame or testpiece can vibrate when subjected to a high rate force. The transducers attached to the machine frequently register this vibration superimposed on the true signal and thus may mask the signal required for analysis [1-4]. At impact all the parts of the test machine oscillate at their natural frequency (dependent on stiffness and mass). Ringing in test machines is determined by the rate at which the testpiece is deformed, the elastic characteristics of test material and resonances in components of load train anvils in compression. In the current work high rate hot compression tests are being developed to underpin best practice measurement guides on test methods for studying the dependence of strength on deformation rate and temperature, [5-7]. At higher rates of deformation ringing is observed in the transducer signals for load and displacement and this measurement note summarises the results of systematic tests to investigate this issue. A purpose built software tool was developed for analysing the time dependence of the transducer signals.