Issue 49

Y. Saadallah et alii, Frattura ed Integrità Strutturale, 49 (2019) 666-675; DOI: 10.3221/IGF-ESIS.49.60 673 Figure 6: Dependence of viscoelastic parameters at the strain-rate Figure 7: Dependence of viscoplastic parameters at the strain-rate To define the functions that represent the mathematical relationship of the strain rate with the viscoelastic and viscoplastic parameters, a nonlinear regression technique is considered. As a result, a power law connects both the viscoelastic parameters and the viscoplastic parameters to the strain-rate. The curves that represent the sensitivity of the viscoelastic parameters to the strain-rate are illustrated in Fig. 6. The sensitivity of the viscoplastic parameters is illustrated in Fig. 7. With the exception of the elastic modulus E and the coefficient of hardening n which are independent of it, the functions obtained are shown in Tab. 3. K ve  e  . H . vp  0,21 58881   0,87 6, 6166    0,02 28, 059   0,12 222, 27   0,88 2, 3512    Table 3 : Relationship of the parameters with the strain-rate 0 5000 10000 15000 20000 25000 30000 35000 0 0,02 0,04 0,06 K (MPa) Strain-rate (1/min) 0 5000 10000 15000 20000 25000 30000 35000 0 0,02 0,04 0,06 µ_ve (MPa.min) Strain-rate (1/min) 0 20 40 60 80 100 120 140 160 180 0 0,02 0,04 0,06 H (MPa) Strain-rate (1/min) 0 2000 4000 6000 8000 10000 12000 0 0,02 0,04 0,06 µ_vp (MPa.min) Strain-rate (1/min)