基于空间反射镜薄壁类轻量化新型结构残余应力测量关键问题研究

Precise manufacturing and inspection of mirrors in space science satellites are critical. Residual stresses measurement has always been a hotspot of research in and abroad. Although the drilling method to measure residual stress has been elaborated in theory and widely used in industry but not immediately applied to special structures such as thin-walled lightweight. In the present study, based on integration method which is the most basic and most important theory, several finite element models for calibration coefficients will be described and a comparative study will be made. By improving the model, the effect of thickness size on calibration coefficients of isotropic materials, orthotropic materials and composites in space mirrors are investigated. Calibration formulas are proposed to simplify and improve the traditional calibration matrices, and then the variable of thickness is introduced to obtain correction of calibration for thin-wall, sheet type member. Combined with high sensitivity moiré interferometry, calculating scheme will be designed to measure residual stress in depth for thin-wall composites. Finally, moiré pattern generated by a drilled hole on thin-wall components will be simulated by finite element analysis and Matlab software and a series of simulated drilling experiments will be carried on by moiré interferometry combined with drilling method. As a quantitative analysis method of measuring residual stress in depth, it is believed that this project is of great importance both in fundamental research and manufacturing.

空间科学卫星中反射镜的精确加工与检测至关重要且结构残余应力的测量及其状态评估一直是国内外研究的热点。尽管钻孔法测量残余应力在理论上有着详尽阐述并在工业上得到广泛应用但未能立即应用于薄壁轻量化等特殊结构。本项目采用最重要最基本的理论——积分法，阐述并对比研究钻孔法有限元标定的多种分析模型。改进有限元分析模型并在较大厚度范围内研究厚度尺寸对空间反射镜中各向同性材料、正交各向异性材料和复合材料应力标定系数的影响规律。提出标定系数公式以简化、改进传统的标定系数表；接着引入厚度参数校正得到适应薄壁、薄板类构件的标定。结合云纹干涉光学全场测量技术，针对薄壁复合材料改进沿深度分布残余应力计算方案。最后，利用有限元、Matlab模拟云纹干涉钻孔法通过干涉条纹研究厚度尺寸对薄壁构件内部应力释放的影响规律。本项目作为一种沿深度方向残余应力大小和分布的定量分析方法，无论对于基础研究还是生产制造都有很大的帮助。

薄壁试件厚度对钻孔积分法在残余应力沿深度分布测量应用中的计算结果有重要影响。如何引入这一因素作用，是目前实现高性能薄壁件残余应力精确测量的一项技术障碍。主要研究内容包括：厚度问题引起的测量偏差；厚度效应存在的尺寸范围；简化与改进传统标定系数矩阵；“均匀应力场”、“非均匀应力场”两类应力计算的标定系数公式拟合；材料厚度、铺设方向与标定系数的关系以及表面应变/位移测量误差对复合材料钻孔法残余应力计算的影响；优化正交各项异性、层压复合材料模拟钻孔法计算效率。本项目揭示了薄壁构件厚度尺寸对增量钻孔法标定系数的影响规律，等双轴应力场标定a和纯剪切应力场标定b随厚度减小而减小。通过分离变量法得到了简单实用的均匀应力场盲孔法标定公式，建立了均匀应力场、非均匀应力场增量钻孔法标定系数公式，标定矩阵公式化拟合优化指数达到99.9%；实现了云纹干涉钻孔法三方向条纹图像模拟；结合三方向云纹干涉全场测量技术，通过获取制约大型轻质反射镜加工精度的内部残余应力测试数据，可为高性能的反射镜材料设计和加工提供可靠的分析数据。