Newly developed dynamic testing methods and dynamic strength of some structural materials

To improve safety during car crushing and to develop a high-speed plastic working and practical constitutive equation for computer codes, it is important to accurately obtain the entire tensile stress-strain curves for a variety of materials that cover a wide range of strain rates and strain. Based on numerical simulations and experiments, it is confirmed that the non-coaxial Hopkinson bar method, developed by Tanimura and Kuriu (1994), is effective at obtaining the stress-strain curve at high strain rates ranging from 10(2)similar to10(4) s(-1) with accuracy and independent of flexural waves. The principles of the newly developed dynamic testing method based on a sensing block, developed by Tanimura, Mimura and Takada (1998), and these features are introduced and summarized. Some of the experimental results obtained by using this method are presented. It is demonstrated that the new system of the testing method is substantially useful for obtaining the entire stress-strain curves of many kinds of materials, and covering a wide range of strain rates from quasi-static strain rates to high strain rates on the order of 10(3) s(-1), with good accuracy, such as that for a conventional quasi-static testing machine. Through numerical simulation using computer codes, the upper limits of the gauge length of specimens are presented. These limits are adaptable to dynamic testing for a wide range of strain rates.