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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Influence of material ductility and crack surface roughness on fracture instability
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Influence of material ductility and crack surface roughness on fracture instability

机译：材料的塑性和裂纹表面粗糙度对断裂不稳定性的影响

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This paper presents a stability analysis for fractal cracks. First, the Westergaard stress functions are proposed for semi-infinite and finite smooth cracks embedded in the stress fields associated with the corresponding self-affine fractal cracks. These new stress functions satisfy all the required boundary conditions and according to Wnuk and Yavari's (2003 Eng. Fract. Mech. 70 1659-74) embedded crack model they are used to derive the stress and displacement fields generated around a fractal crack. These results are then used in conjunction with the final stretch criterion to study the quasi-static stable crack extension, which in ductile materials precedes the global failure. The material resistance curves are determined by solving certain nonlinear differential equations and then employed in predicting the stress levels at the onset of stable crack growth and at the critical point, where a transition to the catastrophic failure occurs. It is shown that the incorporation of the fractal geometry into the crack model, i.e. accounting for the roughness of the crack surfaces, results in (1) higher threshold levels of the material resistance to crack propagation and (2) higher levels of the critical stresses associated with the onset of catastrophic fracture. While the process of quasi-static stable crack growth (SCG) is viewed as a sequence of local instability states, the terminal instability attained at the end of this process is identified with the global instability. The phenomenon of SCG can be used as an early warning sign in fracture detection and prevention.
机译：本文提出了分形裂纹的稳定性分析。首先，针对嵌入在与相应自仿射形裂纹相关的应力场中的半无限和有限光滑裂纹，提出了Westergaard应力函数。这些新的应力函数满足所有所需的边界条件，根据Wnuk和Yavari（2003 Eng。Fract。Mech。70 1659-74）嵌入式裂缝模型，它们可用于导出分形裂缝周围产生的应力和位移场。然后，将这些结果与最终拉伸准则一起用于研究准静态稳定裂纹扩展，该扩展在塑性材料中先于整体破坏。通过求解某些非线性微分方程来确定材料的阻力曲线，然后将其用于预测在稳定裂纹扩展开始时和在发生突变性破坏的临界点处的应力水平。结果表明，将分形几何形状并入裂纹模型（即考虑裂纹表面的粗糙度）会导致（1）较高的材料抗裂纹扩展阈值水平和（2）较高的临界应力水平与灾难性骨折的发作有关。虽然准静态稳定裂纹扩展（SCG）过程被视为一系列局部失稳状态，但在此过程结束时达到的最终失稳被认为是整体失稳。 SCG现象可作为骨折检测和预防的预警信号。

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