混合型应力强度因子的光弹性多参数测定

提高裂纹尖端应力强度因子值的计算精度,对于准确分析受力结构的起裂条件和破坏模式具有重要意义.本文采用3D打印技术获得了不含残余应力的平板模型,高精度打印预置裂纹避免了传统加工过程产生残余应力的缺点;综合考虑奇异场和非奇异场对裂纹尖端区域应力场的影响,引入远场边界控制的三个常数项应力,提出了光弹性多参数法;采用三点弯曲试验,运用最小二乘法计算了不同载荷下纯 Ⅰ 型和 Ⅰ-Ⅱ 混合型应力强度因子值,并与理论解对比分析.结果表明:对于纯Ⅰ 型应力强度因子,计算结果的平均误差为6.1%,对于 Ⅰ-Ⅱ 混合型应力强度因子,计算结果的平均误差分别为6.4%和5.5%,多参数法与理论解相比较小的计算误差验证了该方法的可靠性和准确性,可为精确计算应力强度因子的光弹性实验研究提供借鉴.

Multiple parameter measurement of mixed-mode stress intensity factors using the photoelastic method

Precise calculation of the stress intensity factors at crack tips is of great significance in accurate analysis of a structure' s crack initiation and fracture mode. In this research, a three-dimensional printing technique was adopted to manufacture a non-residu-al stress plate model, where high-precision printed pre-cracks avoid the occurrence of residual stress compared to traditional manufac-turing processes. By comprehensively considering the singular and non-singular stresses at the near-crack-tip region, three constant stresses controlled by the far field were adopted. Multiple parameters of the photoelastic method combined with the least-squares meth-od were applied to analyze the stress intensity factors of mode I and mixed modes in three-point bending tests under different loads, and a theoretical solution comparison was conducted. Results show that compared with the theoretical solution, the average calculation error for the mode Ⅰ stress intensity factor is 6. 1% and those for Ⅰ – Ⅱ mixed modes are 6. 4% and 5. 5% , respectively. This slight calcu-lation error verifies the reliability and accuracy of the multiple-parameter method and provides a reference for further precise calcula-tions of the stress intensity factors using the photoelastic method.