Testing Conditions in Kolsky Bar Experiments

In a material property characterization experiment, the specimen should deform uniformly under well-controlled testing conditions in order for the experimental results to be clearly documented and interpreted. In quasi-static experiments, testing conditions are monitored and adjusted in real time by closed-loop feedback control systems such that the specimen deforms under specified conditions throughout the test. In Kolsky-bar experiments, feedback control systems are not available. Furthermore, due to the relatively low stiffness of the bars, even under identical loading conditions, the testing conditions on the specimen depend on the specimen response. Therefore, it is challenging to subject the specimen to specified loading conditions in Kolsky-bar experiments. Both the loading processes in the specimen and their relations to the commonly defined testing conditions need to be carefully examined. In addition, the development of Kolsky bar and its data reduction scheme involves many idealized assumptions. However, in actual Kolsky-bar experiments, these assumptions are not satisfied automatically, which requires further efforts in experiment design. The valid testing conditions and necessary approaches to achieve specified conditions in the Kolsky-bar experiments are presented in this Chapter.