超塑性非球面自由胀形的测量

超塑性胀形是成形薄壁壳形件的重要技术, 已经在航空技术领域占有重要地位. 由于超塑性自由胀形是建立超塑胀形力学解析理论的重要依据, 又是超塑胀形成形的必经阶段,而超塑自由胀形的轮廓曲面为轴对称旋转曲面, 本文针对精确测量轴对称旋转曲面的几何参数尚存在的一些问题, 提出了测量方法及基本原理, 介绍了基于单目成像的图像采集系统及摄像机参数的标定方法, 并对旋转体试件的成像测量进行分析, 给出了误差补偿公式; 对于实验中极点高度测量和实验后轮廓测量采用不同算法, 以保证系统的实时性; 为提高测量精度, 采用亚像素算法, 同时分析了误差产生的原因.

MEASUREMENT OF THE NON-SPHERE SUPERPLASTIC FREE BULGING

Superplastic bulging is important technology for forming thin walled workpieces with shell shape. Especially, the compound technology of superplastic bulging and diffusion bonding, by which scores of parts or even more than one hundred parts could be combined to become a assembly, would reduce the weight of the assembly, raise its rigidity and make its structure more reasonable. So, superplastic bulging forming technology plays an important role in the field of aviation manufacturing application. Superplastic free bulging test provides important foundation for establishing mechanical theory of superplastic bulging and it also is a necessary process for superplastic bulging forming due to no die and no effect of friction. Aimed at the problems  coming from precisely measuring the geometry parameters of the axisymmetric surface of revolution which is the real shape of free bulging during the experiment, a vision measure way and its principle are brought forward to detect the edge of sample in the paper. The components of monocular vision system and the method of the camera calibration are introduced. The error compensation equation was deduced through analysis on the vision measure process of the revolution surface. In order to ensure the system in real--time, the algorithm of digital image processing adopted during the experiment is different with that after the experiment, which used sub--pixel arithmetic to improve the measure precision. And then the causes of the error are investigated.