Yoshida Sanichiro, Sasaki Tomohiro
Department of Chemistry and Physics, Southeastern Louisiana University, Hammond, LA 70402, USA.
Department of Mechanical Engineering, Niigata University, Niigata 9502181, Japan.
Materials (Basel). 2020 Mar 17;13(6):1363. doi: 10.3390/ma13061363.
A method to diagnose the deformation status of solid objects under loading is discussed. The present method is based on a recent field theory of deformation and fracture and optical interferometry known as the Electronic Speckle-Pattern Interferometry (ESPI). Using one of the most fundamental principles of physics referred to as symmetry in physics, this field theory formulates all stages of deformation and fracture on the same theoretical basis. In accordance with the formalism, the theory has defined the criteria for different stages of deformation (linear elastic, plastic and fracturing stages) expressed by certain spatiotemporal features of the differential displacement (the displacement occurring during a small time interval). The ESPI is used to visualize the differential displacement field of a specimen as two-dimensional, full-field interferometric fringe patterns. This paper reports experimental evidence that demonstrates the usefulness of the present method. A tensile load is applied to an aluminum-alloy plate specimen at a constant pulling rate and the resultant in-plane displacement field is visualized with a two-dimensional ESPI setup. The differential displacement field is obtained at each time step and the interferometric fringe patterns are interpreted based on the criterion for each stage of deformation. It has been found that the criteria of linear elastic deformation, plastic deformation and fracturing stage are clearly observed in the corresponding fringe patterns and that the observations are consistent with the loading characteristics.
本文讨论了一种诊断加载状态下固体物体变形状态的方法。该方法基于最近的变形与断裂场论以及一种名为电子散斑图案干涉术（ESPI）的光学干涉测量法。利用物理学中被称为对称性的最基本原理之一，该场论在同一理论基础上阐述了变形与断裂的各个阶段。根据这一形式体系，该理论定义了由微分位移（在小时间间隔内发生的位移）的某些时空特征所表示的不同变形阶段（线弹性、塑性和断裂阶段）的判据。ESPI用于将试样的微分位移场可视化为二维全场干涉条纹图案。本文报告了证明该方法有效性的实验证据。以恒定拉伸速率对铝合金板材试样施加拉伸载荷，并用二维ESPI装置对由此产生的面内位移场进行可视化。在每个时间步长获取微分位移场，并根据每个变形阶段的判据对干涉条纹图案进行解释。研究发现，在线弹性变形、塑性变形和断裂阶段的判据在相应的条纹图案中清晰可见，且这些观察结果与加载特性一致。
