Evaluation of ductile fracture models in high velocity impact problems Ying Li1,*, Xiaobin Li1, Xiangshao Kong1, Xing-xing Wu1 1. School of Transportation, Wuhan University of Technology, Wuhan, 430063 * Corresponding author: liying198842@126.com Abstract: As resourceful stress states, high strain rates, and large plastic deformation were involved, the Taylor test can be used to identify the most suitable fracture criterions for high velocity impact problems. A systematic evaluation is carried out for the maximum principal stress, the maximum principal strain, equivalent plastic strain and Johnson–Cook fracture models by numerical simulations. The applicability of the ductile fracture models are discussed, finally. Keywords: Taylor impact, Ductile fracture, Johnson–Cook fracture model 1. Introduction Considering high temperature and high strain rates, strength models and fracture criterions are needed in impact response calculation of metal material. There are J-C, ZA, MTS strength models and the maximum principal stress, the maximum principal strain, equivalent plastic strain and Johnson–Cook fracture models to chose from. It is necessary to evaluate these fracture models. The Taylor test can get high strain rate (104~106), in which a deformable flat-nosed cylinder is fired against a fixed, rigid wall and was originally proposed to determine dynamic yield stresses of materials [1]. Taylor test results are used to validate or to estimate coefficients for phenomenological strength models needed for simulating dynamic loading processes using inverse identification procedures[2-4]. When Taylor bar runs fast, cracks and fragmentation phenomenon are very common. Couque (1998)[5] observed several spiral cracks which formed on the lateral surface of the cylinder in symmetric Taylor tests on swaged tungsten alloys. Material mechanics performance test of Q235 was taken to calculate parameters of fracture criterions. The display dynamic analysis software AUTODYN was used to forecast failure modes of Taylor tests. The differences and limitations of the ductile fracture models are discussed, finally. 2. Mechanical property testing of Q235 To get parameters of the fracture criterions, cold quasi static single axis tensile test was done on MTS. Specimens were processed according to <GB/T228-2002>, whose diameter was 10mm, length of test part was 100mm (see Fig.1). Loading rate of this test was 0.6mm/min (strain rate was 2×10-4/s).
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