Assessment of the Fracture Toughness of Elastoplastic Materials Based on the Structure State at the Crack Tip

IF 0.7 4区 材料科学 Q4 MATERIALS SCIENCE, CHARACTERIZATION & TESTING
M. R. Muzyka
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Abstract

The methodological foundations of assessing the fracture toughness of elastic-plastic materials are considered. A methodology is proposed based on the results of assessing the fracture toughness of a material based on the structure state in the region of the crack tip. It is shown that the state of the material structure in the fracture zone of a uniaxially loaded specimen under the action of a stress close to the material’s ultimate strength is adequate to the structure state in the region of the crack tip before crack initiation and is a structural characteristic of this material. Based on the above correlation of material states, a structural parameter is proposed for assessing the fracture toughness of elastic-plastic materials with a crack. A statistical parameter, determined by the LM-hardness method from the Weibull homogeneity coefficient m, which characterizes the degree of scattering of hardness characteristics obtained by indenting the test portion of the loaded specimen, was taken as the fracture toughness index. This characteristic is invariant to the type of stress state and the loading method, i.e., the state of the material structure in the region of the crack tip does not depend on the loading method, which affects only the rate of reaching the ultimate structural damage in the region of the crack tip and the direction of crack propagation. It has been experimentally proved that the structural criterion of fracture toughness can be the same material characteristic as the force or strain characteristic of material fracture toughness. The difference between materials in their ability to resist crack initiation and propagation is determined by their initial structure. It depends only on the value of the thermal and force load parameters at which the material reaches a level of damage (loosening) of the structure at the crack tip sufficient for crack initiation. For comparison, we consider possible options for assessing the fracture toughness of elastic-plastic materials about the damageability of the structure: based on the scattering of the hardness values of the material of the specimen with a crack, on the state of the material structure in the test portion after the failure of the loaded specimen or after its reloading, as well as based on the state of the material structure of the specimen under loading to the ultimate strength of the material.

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根据裂纹尖端的结构状态评估弹塑性材料的断裂韧性
本文探讨了评估弹塑性材料断裂韧性的方法论基础。根据裂纹尖端区域的结构状态评估材料断裂韧性的结果,提出了一种方法。结果表明,在接近材料极限强度的应力作用下,单轴加载试样断裂区的材料结构状态与裂纹萌发前裂纹尖端区域的结构状态相适应,是该材料的结构特征。根据上述材料状态的相关性,提出了一种结构参数,用于评估带有裂纹的弹塑性材料的断裂韧性。用 LM 硬度法根据 Weibull 均匀系数 m 确定的统计参数被用作断裂韧性指数,该参数表征了通过压入加载试样的测试部分获得的硬度特征的分散程度。这一特性与应力状态类型和加载方法无关,也就是说,裂纹尖端区域的材料结构状态与加载方法无关,加载方法只影响裂纹尖端区域达到最终结构破坏的速度和裂纹扩展的方向。实验证明,断裂韧性的结构标准可以是与材料断裂韧性的力或应变特征相同的材料特征。材料之间抗裂纹萌发和扩展能力的差异是由其初始结构决定的。它只取决于材料在裂纹尖端结构达到足以产生裂纹的破坏(松动)程度时的热荷载和力荷载参数值。为了进行比较,我们考虑了评估弹塑性材料断裂韧性与结构可破坏性的可能方案:基于带裂纹试样材料硬度值的散射、加载试样失效后或重新加载后测试部分材料结构的状态,以及加载至材料极限强度时试样材料结构的状态。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Strength of Materials
Strength of Materials MATERIALS SCIENCE, CHARACTERIZATION & TESTING-
CiteScore
1.20
自引率
14.30%
发文量
89
审稿时长
6-12 weeks
期刊介绍: Strength of Materials focuses on the strength of materials and structural components subjected to different types of force and thermal loadings, the limiting strength criteria of structures, and the theory of strength of structures. Consideration is given to actual operating conditions, problems of crack resistance and theories of failure, the theory of oscillations of real mechanical systems, and calculations of the stress-strain state of structural components.
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