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31Si2MnCrMoVE钢是为符合固体火箭发动机壳体设计需要而专门研制的超高强度钢。随着冶炼技术的进步,31Si2MnCrMoVE钢断裂韧度不断提高,构件采用的板厚也越来越薄。由于较高的断裂韧度和较小的板厚,给钢板表面裂纹断裂韧度测试带来困难,韧带尺寸偏小,难以满足有效性判据。这种情况下,不应该用线弹性断裂力学方法评价材料的断裂韧度,而应采用弹塑性断裂力学测试材料的延性断裂韧度J_(IC)。基于以上原因,在条件断裂韧度不满足有效性判据的情况下,采用试验与有限元分析相结合的方法,通过试验测出裂纹启裂时的条件载荷,用有限元法计算出在条件载荷作用下的延性断裂韧度J_(IC),再用断裂力学理论转换成表面裂纹断裂韧度K_(Ie)。用J_(IC)作为断裂参量,就必须分析J积分的有效性,因此讨论超高强度钢表面裂纹前缘的J守恒和J主导的有效性,从而为固体火箭发动机设计提供依据。
31Si2MnCrMoVE steel is specially developed for the solid rocket motor housing design needs of ultra-high strength steel. With the improvement of smelting technology, the fracture toughness of 31Si2MnCrMoVE steel is continuously improved, and the thickness of the plate used by the components is getting thinner and thinner. Due to the higher fracture toughness and smaller plate thickness, it is difficult to test the fracture toughness of the steel plate surface. The ligament size is too small to meet the validity criterion. In this case, the fracture toughness of the material should not be evaluated by the method of linear elastic fracture mechanics, but the ductility fracture toughness J IC of the material should be tested by elasto-plastic fracture mechanics. Based on the above reasons, under the condition that the conditional fracture toughness does not satisfy the validity criterion, the method of combining test and finite element analysis is used to test the condition load during crack initiation by finite element method The ductile fracture toughness J_ (IC) under load is converted to the fracture toughness K_ (Ie) by surface fracture mechanics theory. Therefore, the validity of J-integral must be analyzed by using J_ (IC) as the fracture parameter. Therefore, the J-conservation and J-dominance effectiveness of the crack front surface of UHV steels are discussed, which provides the basis for the design of solid rocket motors.