Issue 52

A. Drai et alii, Frattura ed Integrità Strutturale, 52 (2020) 181-196; DOI: 10.3221/IGF-ESIS.52.15

(a) (b) (c) Figure 11: Distribution of the equivalent plastic strain in the deformed sample with a compression of 1mm and a torsion angle of 15 ° for different temperatures: (a) 25°C, (b) 60°C and (c) 80°C. This slight influence of temperature can be confirmed by plotting the distribution of the equivalent plastic strain along the radial distance from the upper surface of the sample as shown in Fig. 12. A slight difference was found. In addition, the maximum value of equivalent plastic strain is approximately 2.36.

Figure 12: Distribution of the equivalent plastic strain as a function of the radial distance in the upper surface of the sample during the HPT process for different temperatures: 25°C, 60°C and 80°C. Evolution of applied load and torque Fig. 13 shows the simulation results for the evolution of the compression load applied by the upper anvil as a function of the time during HPT process at various temperatures. The load required for each temperature in the ascending order (25°C, 60°C and 80°C) is respectively 11800, 16200 and 36000 N. We can see that when the temperature increases, the load required for HPT process decreases. For example, for a temperature of 25°C, the required load is more than three times of that required at room temperature. Moreover, the load versus time evolution during the HPT process can be subdivided into four main stages. The first stage starts from the origin up to the end of compression phase. This stage corresponds to the elastic deformation of compression. The second stage corresponds to the increase of the load from the elastic limit of

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