Issue 49

Y. Saadallah et alii, Frattura ed Integrità Strutturale, 49 (2019) 666-675; DOI: 10.3221/IGF-ESIS.49.60 671 As for the viscoplastic parameters, the coefficient of work hardening is constant whatever the strain-rate, or the other viscoplastic parameters are a function of the strain-rate. The higher the strain-rate, the greater the elastic limit e  and the modulus H, and the lower the viscoplasticity coefficient vp  . Strain-rate   1 min  .   E GPa .   K GPa   . ve GPa min  0.0000646 2.9765 7.3122 23.8816 000625 2.9765 12.2063 5.0066 0.00612 2.9765 18.6363 0.7380 0.0556 2.9765 32.3085 0.0640 Table 1 : Viscoelastic parameters Strain-rate   1 min    e MPa  .   H MPa n .   . vp MPa min  . 0.0000646 22.0151 69.8468 0.3072 6962.33 0.000625 20202 94.9441 0.3072 3044.22 0.00612 24.8992 122.883 0.3072 210.346 0.0556 26 155.818 0.3072 23.11376 Table 2 : Viscoplastic parameters Figure 3 : Comparison test-model of the stress–strain curves of Polyamide 6 at various strain-rates