| Small punch (SP) test method is a new type of small specimen testing technical which is used to evaluate the conventional mechanical properties, ductile to brittle transition temperature, fracture toughness.etc of material. Because the small specimen can be directly obtained from equipment at service which has nearly no influence to structure integrity, it will have a good engineering application prospect.In this paper, finite element method (FEM) and ductility material damage theory is employed to simulate the whole experiment procedure. By repeatedly adjust material damage parameter till the load-displacement curve obtained from experiment and simulation is identical, at which time the damage parameters can be treated as true ones. Simulation of necking in conventional tension is also carried to identify the damage parameters. In addition, a three dimensional annular crack J integral of three different material is calculated and compared with each other, which can offer a basis to determine fracture toughness. Finally, simulation of material containing defects by using above material damage parameter is carried out, considering the influence of defect’s position and volume.Ideal material simulation shows that the maximum equivalent plastic strain and local damage appears in a certain distance from the specimen’s central axis, which is consistent with the fracture surface in experiment. The J integral value is high in high yield strength steel under the same displacement load and the plastic zone is relatively small. The simulation of material contains defects shows that damage in local defect zone is more severe, and this zone will be the original of fracture. The defect lies in high strain zone lead to early local failure. The simulated load-displacement curve is almost the same in the initial stage, which varies when the local damage develops to certain extent, besides, the limited load and corresponding displacement is also different. |
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