A method has been developed for determining residual stress based on displacement fields near drilled holes analyzed using 3D digital image correlation. Finite element modeling was used to determine corrections for analytical equations describing displacement fields near the blind holes, which made it possible to determine the residual stress distribution over a wide range of hole depth-to-hole diameter ratios and various areas of displacement field measurements using inverse method iterative calculations. The proposed method eliminates many drawbacks of traditional procedure based on strain gauges as hole eccentricity sensitivity and requirement of the relatively large span between holes. The method and testing setup, build-up of generally available components, were used to determine the residual stress distribution for 316 LVM samples processed by two methods from the large deformation group: hydrostatic extrusion (HE) and high-pressure torsion (HPT), by drilling 1.75 and 0.58-mm-diameter blind holes, respectively. In the case of the measurements performed on the surface of a HE-processed 16 mm bar cut along its diameter, a gradual change was revealed—from a compressive to a tensile residual stress distribution (from ~ − 300 MPa in the center to 400 MPa in 4 mm distance from the edge) in the longitudinal direction, with near-zero values in the radial direction. Moreover, the method was also adapted to perform measurements on the outside surface of the bar, which gave results consistent with those taken along the radius profile (~ 600 MPa longitudinal stress). Measurements on the top surface of a cylinder 10 mm in diameter and 1 mm high processed by HPT showed a high compressive residual stress in the center and a dominant shear component for the holes drilled at different distances from the center.

中文翻译：

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HE和HPT处理的316 LVM钢的3D DIC辅助残余应力测量

已经开发出一种方法，用于基于使用3D数字图像相关性分析的钻孔附近的位移场来确定残余应力。有限元建模用于确定描述盲孔附近位移场的分析方程式的校正，这使得有可能确定在宽范围的孔深与直径比以及使用位移场测量的各个区域上的残余应力分布反方法迭代计算。所提出的方法消除了基于应变仪的传统方法的许多缺点，例如孔偏心率灵敏度和对孔之间较大跨距的要求。方法和测试设置，通用组件的构建，分别通过对1.75和0.58 mm直径的盲孔进行钻削，确定了通过大变形组中的两种方法处理的316个LVM样品的残余应力分布：静水挤压（HE）和高压扭转（HPT）。在沿其直径切割的经过HE处理的16 mm棒材的表面上进行测量的情况下，发现了逐渐的变化-从压缩残余应力分布到拉伸残余应力分布（从中心的〜-300 MPa到400 MPa在距边缘4mm的距离内）沿纵向方向，在径向方向上接近零值。此外，该方法还适用于在钢筋的外表面上执行测量，其结果与沿半径轮廓（约600 MPa的纵向应力）得出的结果一致。