Abstract
The test data of metals, brittle materials and polymers in high, medium and low strain-rate range were summarized. It was found that the dynamic strength or yield stress of these materials was not sensitive to strain-rate in the low and high strain-rate range (corresponding to weak sensitivity area and saturated zone). But in the medium strain-rate range (strong sensitivity area), the dynamic strength or yield stress of these materials was extremely sensitive to strain-rate. The strain-rate effect function in classic Johnson-Cook constitutive model could not describe these phenomena in the range of low to high strain-rate. Therefore, the strain-rate effect function in classic Johnson-Cook constitutive model has been modified to a strain-rate effect expression which is suitable for different materials. This new model can better describe the phenomena of the weak sensitivity area, strong sensitivity area and saturated zone. With this model, the fitted curves are in good agreement with the test data, and the parameters are different for different materials. Finally, the fitting parameters are given.
Highlights
The dynamic mechanical property of materials under impact loads is a hot research topic of the impact dynamics
It is observed that the relationship between dynamic increase factor (DIF) and the common logarithmic of strain-rate obtained from either split Hopkinson pressure bar (SHPB) compression tests or tensile tests exhibits the phenomenon of three regimes
It may be due to the difference of the strength or yield stress for various types of materials, viz. the deformation physical mechanisms of metals, brittle materials and polymers are different
Summary
The dynamic mechanical property of materials under impact loads is a hot research topic of the impact dynamics. The difference of the material behavior under impact loading and quasi-static loading is that the dynamic strength or yield stress increases as the strain-rate increases. In the lower strain-rate range, the material dynamic strength or yield stress increases slowly with increasing strain-rate (identified as Regime I, weak sensitivity area).
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