建立了非接触光学测量实验系统, 对薄壁球壳受刚性平面压缩的连续变形及失稳行为进行了实验研究。实验以理想弹塑性材料制成的薄且壁厚均匀的乒乓球为压缩对象, 采用透明石英玻璃板作为刚性平面, 用相机透过玻璃板采集清晰的散斑图像。然后利用具有非接触、全场、高精度等优点的三维数字图像相关(3D-DIC)技术对与刚性平面接触的乒乓球表面的连续变形进行直接测量, 同时利用二维数字图像相关技术结合压力传感器得到对应的力-位移关系。实验研究表明, 基于3D-DIC方法测量三维表面变形场, 实现了对受刚性平面压缩的乒乓球表面从局部压平阶段到轴对称屈曲阶段, 进而演化到非轴对称屈曲阶段等力学行为的可视化。实验结果表明, 对乒乓球半径的测量精度可达0.5%, 利用Abaqus有限元方法得到的结果与实验结果非常吻合, 验证了所提方法的有效性。

An optical measurement experimental system was proposed to research the continuous deformation and crushing behavior of thin-walled spheres compressed by a rigid plate. In experiments, ping pong balls were selected as thin-walled spheres because of its ideal material properties and very thin but uniform wall thickness and the quartz glass plate was regarded as a rigid body to compress ping pong balls. Then, the speckle pattern was captured by cameras clearly. Furthermore, the three dimensional digital image correlation (3D-DIC) method with advantages of non-contact, full-field measurement, and high-accuracy was employed to measure the continuous compression deformation of the contact surface of the ping pong balls directly. The two dimensional digital image correlation method combined with a pressure sensor was used to obtain force-displacement curves simultaneously. Experimental results demonstrate that the 3D-DIC method is able to implement the visualization of mechanical behaviors of thin-walled spheres compressed by the rigid plate, including the local flattening, axisymmetric inward dimpling and the unsymmetric polygon formation. Experimental result indicates that the measurement precision of ping pong balls is up to 05%, and the numerical results obtained by using Abaqus is in agreement well with experimental results. The experimental and numerical results both demonstrate the validity of the proposed method.