Constitutive models play a significant role in understanding the deformation behavior of materials and in optimizing the manufacturing process. In order to improve the reliability of calculation results, the high temperature flow behavior of TA31 titanium alloy obtained from an annealed hot-rolled plate has been investigated by a Gleeble-3500 thermo-mechanical simulator. The isothermal hot compression tests are conducted in the temperature range of 850 to 1050 °C and the strain rate range from 0.001 to 10 s⁻¹ with a height reduction of 60%. The annealed TA31 shows a dynamic recovery characteristic during thermo-mechanical processing. The experimental data have been used to develop an Arrhenius-type constitutive model and a modified Johnson–Cook model under the consideration of coupling effect on strain, temperature, and strain rate, as well as the strain-softening phenomenon. The material parameters are determined by a global optimization method based on the initial values by means of a regression method. A comparation of the predicted results has been performed based on the modified Johnson–Cook model and those acquired from the Arrhenius-type model. The correlation coefficient and average absolute relative error of the modified Johnson–Cook model are 4.57% and 0.9945, respectively. However, when the optimization method has been applied, they are 15.77% and 0.9620 for the Arrhenius-type model, respectively. These results indicate that the modified Johnson–Cook model is more accurate and efficient in predicting the flow stress of annealed TA31 titanium alloy under a set of model material parameters. Furthermore, the simple mathematical expression of this model is helpful to incorporate it into the finite element software to obtain detailed and valuable information during the thermo-mechanical processing simulation for TA31 in further work.

The coupling effect of freeze‐thaw (F‐T) temperature and dynamic load on the dynamic mechanical properties and fracture mechanism of saturated yellow sandstone was experimentally investigated in this research. The dynamic compression tests on the specimen after different F‐T temperatures (i.e., −5°С, −10°С, −15°С, −20°С, −30°С, and 20°С) have been carried out with split‐Hopkinson pressure bar (SHPB) setup under eight F‐T cycle numbers. The density and P‐wave velocity of the specimens were obtained before and after the F‐T tests. After the F‐T tests, the specimen microstructures were examined via the scanning electron microscope (SEM). The dynamic fracture process was visualized by the high‐speed camera. The particle size distribution and fragment shapes of the specimens were analyzed using a classifying screen. In addition, the energy dissipation law of specimens during the impact test was also discussed. Experimental results show that the dynamic elastic modulus, strength of the specimen, and the average particle size decrease with decreasing F‐T temperature. SEM results reveal that low F‐T temperature leads to severer internal damage of the specimen by inducing freeze‐swell holes, interconnected cracks, and pore clusters. In addition, the fragmentation shapes of the failed specimens exhibit double‐cone failure, single‐side slope failure, double‐side slope failure, and split failure. The energy dissipation increases gradually with increasing F‐T temperature. This study helps to prevent geological disasters and optimize engineering design in cold regions.