Issue 49

Yu. Bayandin et alii, Frattura ed Integrità Strutturale, 49 (2019) 243-256; DOI: 10.3221/IGF-ESIS.49.24 250 Figure 4: Particle velocity profiles for vanadium sample. The solid line is stress amplitude value about 9.7 GPa (numerical calculation), the dashed line − 6.4 GPa (numerical calculation), ○ − 9.7 GPa (experiment), □ − 6.4 GPa (experiment) [33] Figure 5: Dependence of spall strength versus strain rate: ● − experiment [25], − model calculation, ▼ − experiment [24] The results of numerical simulation for the spall fracture are in accordance with the experiment and have established an increasing of spall stress with the increase of strain rate. That is the consequence of the pronounced damage localization with the avalanche kinetics of defect growth and weak sensitivity of the blow-up damage kinetics to the current value of stress amplitude. During the numerical simulation, the velocity profiles were reconstructed at different parts of the sample in order to study the connection between the structural relaxation laws due to nonlinear defect kinetics, elastic-plastic transitions and the formation of viscoplastic wave fronts. Fig. 6 shows the results of numerical simulation and experimental dependencies of the elastic precursor amplitude for different thickness of the sample. 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 Time,  s Particle velocity, m/s 10 4 10 5 10 6 10 7 10 8 0 1 2 3 4 5 6 7 8 Strain rate, s -1 Spall strength, GPa