The objective of this work is to develop an appropriate strain-rate- and temperature-dependent material constitutive model to simulate plastic deformation behavior of SA516Gr.70 steel in the sub-zero temperature regime (− 128 to 25 °C). For this purpose, tests have been conducted at three different strain rates covering an order of 6 in the rates, i.e., from 0.001 to 1400/s. Tests at high strain rates have been conducted using a modified split Hopkinson pressure bar test setup. The tensile tests have been designed in such a way that the strain rate remains almost constant during the test. A critical comparison of results of both tension and compression high strain-rate tests has been carried out, and the suitability of tensile experiments has been highlighted. A modified Ramberg–Osgood model, with temperature- and strain-rate-dependent parameters, has been presented. The parameters of the new model have been evaluated from a large set of experimental data. It was observed that the yield stress and ultimate tensile strength of the material increase monotonically with decreasing temperature and increasing strain rates. The ductility at fracture and extent of uniform elongation of the specimen decrease for the intermediate strain rate of 0.925 s⁻¹, when compared to the corresponding values at quasistatic rate of loading. At very high rate of loading, ductility increases due to the increased resistance of the material to growth and coalescence of voids. From the comparison of results of model and experiment, it has been observed that the modified material model is able to predict the true stress–strain curve of the material satisfactorily in the sub-zero temperature regime over a wide range of strain rates. The nature of variation of mechanical properties with temperature and strain rate has been explained from the point of view of dislocation-based micromechanism of the plastic deformation process.

这项工作的目的是建立一个合适的应变速率和温度相关的材料本构模型，以模拟SA516Gr.70钢在低于零温度范围（-128至25°C）下的塑性变形行为。为此，已经在三种不同的应变速率下进行了测试，覆盖速率的6数量级，即0.001至1400 / s。使用改进的分体式霍普金森压力棒测试装置进行了高应变率测试。拉伸测试的设计方式使得应变率在测试过程中几乎保持恒定。对拉伸和压缩高应变率测试结果进行了严格的比较，并强调了拉伸实验的适用性。修正的Ramberg–Osgood模型，具有与温度和应变率有关的参数，已经提出。新模型的参数已从大量实验数据中进行了评估。观察到，材料的屈服应力和极限拉伸强度随温度降低和应变速率增加而单调增加。在0.925 s的中间应变速率下，断裂时的延展性和试样的均匀伸长程度降低。^-1，当与准静态加载速率下的相应值相比时。在很高的加载速率下，由于材料对空隙的生长和聚结的抵抗力增强，延展性增加。通过模型和实验结果的比较，可以看出，改进的材料模型能够在零应变范围内的零应变温度范围内令人满意地预测材料的真实应力-应变曲线。从塑性变形过程中基于位错的微观机制的角度解释了机械性能随温度和应变率变化的性质。