Rickhey Felix, Marimuthu Karuppasamy Pandian, Lee Hyungyil
Department of Mechanical Engineering, Sogang University, Seoul 04107, Korea.
Materials (Basel). 2017 Apr 12;10(4):404. doi: 10.3390/ma10040404.
Vickers indentation fracture can be used to estimate equibiaxial residual stresses (RS) in brittle materials. Previous, conceptually-equal, analytical models were established on the assumptions that (i) the crack be of a semi-circular shape and (ii) that the shape not be affected by RS. A generalized analytical model that accounts for the crack shape and its change is presented. To assess these analytical models and to gain detailed insight into the crack evolution, an extended finite element (XFE) model is established. XFE analysis results show that the crack shape is generally not semi-circular and affected by RS and that tensile and compressive RS have different effects on the crack evolution. Parameter studies are performed to calibrate the generalized analytical model. Comparison of the results calculated by the analytical models with XFE results reveals the inaccuracy inherent in the previous analytical models, namely the neglect of (the change of) the crack aspect-ratio, in particular for tensile RS. Previous models should therefore be treated with caution and, if at all, used only for compressive RS. The generalized model, on the other hand, gives a more accurate description of the RS, but requires the crack depth.
维氏压痕断裂可用于估算脆性材料中的等双轴残余应力（RS）。以往在概念上等效的分析模型是基于以下假设建立的：（i）裂纹为半圆形；（ii）其形状不受残余应力影响。本文提出了一个考虑裂纹形状及其变化的广义分析模型。为了评估这些分析模型并深入了解裂纹扩展过程，建立了一个扩展有限元（XFE）模型。XFE分析结果表明，裂纹形状通常不是半圆形，且受残余应力影响，拉伸和压缩残余应力对裂纹扩展有不同影响。进行了参数研究以校准广义分析模型。将分析模型计算结果与XFE结果进行比较，揭示了先前分析模型固有的不准确性，即忽略了裂纹纵横比（的变化），特别是对于拉伸残余应力。因此，对于先前的模型应谨慎对待，若要使用，也仅适用于压缩残余应力。另一方面，广义模型能更准确地描述残余应力，但需要知道裂纹深度。
