![]() ![]() The use of the cam plastometer with statistical methods provides an accurate means of investigating the effects of temperature and strain rate on the resistance of specimens to compression. The parameter B was found to be essentially independent of temperature, but a large increase of strain rate produced an increase in B. The parameters A and C more » were found te increase with decreasing temperature and with lange increases in strain rate. True stress versus true strain curves were calculated and found to fit an equation of the form sigma = A (1 - e/sup B epsilon /) + C epsilon, where sigma is the true stress, epsilon is the true strain, and A, B, and C are parameters. Repleted uranium specimens were tested at several strain rates and temperatures. Commercially pure aluminum specimens were tested at room temperature at three strain rates. « lessĪ cam plastometer was designed and built to test metal specimens in compression over a range of constant true strain rates and temperatures. ![]() The results predicted with the modified JC model agreed with the tensile experimental data reasonably well. The modified JC model was also used to describe the true stress–strain response during necking for A5 steels at various strain rates. Here, we modified the JC model with a power-law strain rate effect and an explicit form of strain- and strain-rate-dependent thermosoftening due to adiabatic temperature rise to describe the strain-rate-dependent tensile stress–strain response, prior to the onset of necking, for 304L stainless steel, A572, and 4140 steels. Yet, the TQ coefficient is difficult to determine since it may be strain and strain-rate dependent. The temperature rise can be calculated from plastic work with a predetermined Taylor-Quinney (TQ) coefficient. The standard expression of the JC model requires quantitative knowledge of temperature rise, but it can be challenging to obtain in situ temperature measurements, especially in dynamic experiments. In addition to strain rate effect, the Johnson–Cook (JC) model includes a term to describe more » the effect of either environmental or adiabatic temperature rise. Capturing the thermosoftening caused by adiabatic heating is critical in material model development to precisely predict the dynamic response of materials and structures at high rates of loading. Adiabatic heating in these materials during high-rate deformation is of great interest to analysts, experimentalists, and modelers due to a reduction in strength that is produced. Metallic alloys are extensively utilized in applications where extreme loading and environmental conditions occur and engineering reliability of components or structures made of such materials is a significant concern in applications.
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