| With the miniaturization development of engineering components, thin plates and thin-walled tubes are widely applied in the industries of aerospace, nuclear power, chemical equipment and instrumentation. The estimation of fracture toughness by using small size specimens is of great importance. But the current test method for the fracture properties of materials with small specimen is far from demands. In this thesis, some systematic researches on the test method for fracture property by small size specimen have been carried out. The results are listed as follows.(1) A kind of C-shape specimens with small size and its corresponding loading fixture are designed. With refined finite element analysis, the expressions to get crack length by compliance, stress intensity factor K and plastic factor are given.(2) The non-dimensional load separation method to estimate J resistance curves of ductile materials for C-shape specimen is proposed. The J-resistance curves test for26NiCrMoV11-5and A508-Ⅲ are carried out by use of C-shape specimens and CT specimens, respectively. The results show that, the specimen thickness and initial crack size have limited influence on fracture toughness of ductile materials obtained by C-shape specimens. Due to the higher level of constraint near the crack tip of C-shape specimen, a visible lower J-resistance curves can be observed in comparison with CT specimen.(3) Many C-shape specimens and compact tension specimens were employed to investigate the fatigue crack growth behavior of26NiCrMoV11-5rotor steel. The steady fatigue crack growth rule for each material resulted from the two different types of specimen are consistent with each other. It is concluded that the C-shape specimen is feasible for representing fatigue crack growth behavior of metallic materials.(4) Based on refined finite element analysis, a revised expression of relative secant slope AS used to determine critical load Po of the plane strain fracture toughness KIC has been developed. |
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