一种新的宏、细观变形全场测量方法

基于光学干涉和衍射理论,提出了一种新的用于宏、细观面内变形测量的光学方法。利用三束准直相干光之间的干涉,分别得到面内位移U V和U-V的两幅耦合条纹图。借助于FFT相移技术,直接计算出全场的U和V分布。本实验系统中包含有长距离显微镜,三光束系统,数字图像采集和处理系统等。它具有光路简单,避开条纹级次的确定,直接计算得到U、V场等优点。将它用于热塑性复合材料 56层板AS4/PEEK[0/±45/90]7S三点弯曲梁位移场的宏、细观测量。得到了层间的变形规律。本文还利用三维各向异性弹性有限元法对AS4/PEEK[0/±45/90]7S三点弯曲梁进行了数值计算,得到了自由表面的位移场和应变场的数值解。定量分析了层间的变形传递规律,有助于进一步分析AS4/PEEK[0/±45/90]7S层合板宏、细观变形。

A New Optical Method for Macro and Micro-zone Strain Measurements

Based on the principles of the optical diffraction and interence,a new optical method for strain measurements in macro or micro-zone.is presented.A cross grating of the frequency of 1200 Vmm is replicated on the specimen surface. Three coherent laser beams are used to obtain the U + V and U - V fringe patterns.U and V are calcualted with the high displacement precision. A new experimentalimage processing system and the software. compared to the traditional moire interferometry, this meth-od has some advantages, such as simple optical arrangement,direct calculation of U and V fields with higher precision and so on. An rxample of this method is performed. The displacement and strain fields on the free-edge of the thermo-plastic composite laminates AS4/PEEK[0°/±45°/90°]7S(56-ply)under three-point bending have been measured. It concerns the strain distribution in the zone of interface of two layers and the damage mechanism between the two plies of AS4/PEEK[0°/45°/90°]7S composite laminates. The corresponding numerical sumulation has been carried out using therr-dimensional orthotropic elastic finite elemient model. It is believed that this method would be a powerfultool for characterizing the mechanical properties of materials.