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本文用三点弯曲和四点弯曲试样,在K_Ⅱ/K_Ⅰ=0—14的范围内,对GC-4超高强度钢、30Cr2MoV中强度转子钢和稀土球墨铸铁进行了线弹性平面应变复合型脆断试验。结果表明:复合型裂纹的脆断开裂方向与现有的三种复合型理论符合较好;但是,复合型裂纹扩展阻力随K_Ⅱ/K_Ⅰ比值增加而增大,与现有复合型理论差别较大。本文从塑性区的形状、大小和裂纹顶端在开裂方向的应力状态等方面对此问题进行了分析并指出,现有理论关于复合型裂纹扩展阻力与变形特征无关的假设,对于具有一定塑性变形能力的金属材料,是不合适的。文章还对简单且偏于安全的处理复合型问题的工程分析方法作了讨论。
In this paper, three-point bending and four-point bending specimens were used to conduct the linear elastic plane strain composite of GC-4 ultra-high strength steel, 30Cr2MoV medium strength rotor steel and rare earth nodular cast iron in the range of K_Ⅱ / K_I = 0-14. Brittle breaking test. The results show that the direction of brittle fracture of composite crack is in good agreement with the existing three complex theory. However, the crack propagation resistance of composite crack increases with the increase of K_Ⅱ / K_Ⅰ ratio, which is different from the existing composite theory Big. In this paper, the plastic zone shape, size and crack tip in the cracking direction of the stress state and other aspects of the problem is analyzed and pointed out that the existing theory of composite crack propagation resistance and deformation characteristics unrelated assumptions for a certain plastic deformation capacity The metal material is not suitable. The article also discusses the simple and unsafe engineering approach to complex problems.