The application of digital image and volume correlation techniques to obtain displacement fields from images has become ubiquitous in experimental fracture mechanics. In this paper, a procedure to extract the J‐integral (J) from three‐dimensional displacement fields obtained using digital volume correlation is presented. The procedure has been specially adapted to allow for experimental noise and errors, such as poorly defined crack front displacements, smearing of the displacement field across the crack faces, and knowledge of the imprecise crack front location. The implementation is verified using analytical crack‐tip fields perturbed with synthetic image correlation errors to characterise the response of J. The method is then applied to experimental results using a Magnesium alloy WE43 loaded elastically in mixed mode. The steps outlined are intended as a guideline for the application of the volume integral from displacement fields to allow for accurate calculation of J along a crack front embedded within the volume.

中文翻译：

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根据数字体积相关位移数据准确计算J积分的过程

在图像断裂力学中，数字图像和体积相关技术从图像获得位移场的应用已经无处不在。本文提出了一种从使用数字体积相关性获得的三维位移场中提取J积分（J）的过程。该程序经过特殊调整，可以考虑到实验噪声和误差，例如定义不明确的裂纹前沿位移，跨裂纹面的位移场模糊不清以及对裂纹前沿位置的不精确了解。通过用合成图像相关误差干扰的分析裂纹尖端字段来验证J的响应，从而验证了该实现。然后使用以混合模式弹性加载的镁合金WE43将这种方法应用于实验结果。概述的步骤旨在作为应用位移场的体积积分的准则，以允许沿着嵌入体积内的裂纹前沿精确计算J。