The strong strain-rate dependence, neck propagation and craze evolution characterize the large plastic deformation and fracture behavior of polymer. In the latest study, Kobayashi, Tomii and Shizawa suggested the elastoviscoplastic constitutive equation based on craze evolution and annihilation and then applied it to the plane strain issue of polymer. In the previous study, the author applied their suggested elastoviscoplastic constitutive equation with craze effect to the three dimensional shell issue and then showed that the load displacement history was in good agreement with the experimental result including only microscopic crack such as craze. For the future industrial applications, the macroscopic crack had to be taken into account. For instance, an airbag deployment simulation needed the macroscopic crack prediction. Thus, the main objective of this study was to propose the tensile softening equation and then add it to the elastoviscoplastic constitutive equation with craze effect so that the load displacement history could be roughly simulated during the macroscopic crack propagation. The tested material in this study was the elastomer blended polypropylene used in the interior and exterior of automobiles. First, the material properties were obtained based on the tensile test results at wide range of strain rates: 10−4 – 102 (1/sec). Next, the fast compact tension test was conducted and then the tensile softening parameters were fixed. Then, the fast bending test and the dart impact test were carried out in order to obtain the load displacement history and also observe the macroscopic crack propagation at high strain rate. Finally, the fracture behavior was simulated and then compared with the experimental results. It was shown that the predictions of the constitutive equation with the proposed tensile softening equation were in good agreement with the experimental results.

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