Issue 49

Yu. Bayandin et alii, Frattura ed Integrità Strutturale, 49 (2019) 243-256; DOI: 10.3221/IGF-ESIS.49.24 251 Figure 6: Dependence of the dynamic elastic limit on the thickness of the vanadium sample. Marker ● is the minimum value (experiment) [25], ○ − maximum value (experiment) [25], ▼ − minimum value (experiment [24]), ∇ − maximum value (experiment [ 25]), − numerical calculation, solid line – approximation. Figure 7: Free surface velocity profiles for silicon carbide samples in normalized time coordinates: ○ − experiment [15], lines − numerical simulation for different target thicknesses (8.32 mm, 3.81 mm, 2.15 mm) [22]. The model describes the elastic precursor decay under the path of the elastoplastic wave in the sample (Fig. 6) that is in the agreement with the experimental data. The results of the simulation were approximated (solid line) by an exponential dependence in the form     3.349exp 1.707exp 0.036 0.962 HEL h h      , where h is the thickness of the sample. Numerical simulation shows that the relaxation mechanisms of the elastic precursor can be associated with the effects of energy absorption due to the defects as a new “phase” of the material. This is based on the nonlinear kinetics of 0 2 4 6 8 10 1 10 Thickness, mm Elastic precursor limit, GPa 50 70 90 110 130 0 200 600 1000 1400 Time/Thickness, ns/mm Free surface velocity, m/s