数字散斑相关测量方法研究

发布时间：2018-04-21 21:58

本文选题：数字散斑相关 + 十字搜索法　；参考：《天津工业大学》2017年硕士论文

【摘要】：数字散斑相关测量技术(Digital Speckle Correlation Method,DSCM)是上世纪八十年代发展起来的一种新型光测技术,它的基本原理是通过比较试件变形前后表面散斑图像的变化,获得物体表面的位移和应变场。经过三十多年的发展,该方法以其全场、非接触性、高精度、测量敏感、范围大等优点已受到广泛重视,并已应用在航空航天、无损检测、微尺度变形测量、高温环境下的变形测量、电子封装等众多领域。数字散斑相关方法的首要问题是进行整像素搜索,本文首先利用十字搜索法对整像素位移进行搜索,由于十字搜索法确定主峰区的过程比较复杂,计算量较大,根据位移的连续性,本文对主峰区的选取方式做了改进,将主峰区的初值赋值为相邻点的相关计算结果,这样大大减少了计算量,提高了计算效率。亚像素搜索是数字散斑相关技术中的关键问题,在进行亚像素相关搜索时,本文将基于灰度变化函数的改进的梯度法与曲面拟合法相结合,灰度变化函数的引入减弱了光强变化对测量精度的影响,该方法提高了亚像素位移的测量精度,算法的稳定性也有所提高。在应变求解中,本文选取了计算精度较高、计算量小的最小二乘拟合法来根据位移计算物体的应变量。另外,本文分析了计算子区大小、插值放大倍数、噪声三个因素对数字散斑相关方法求解精度的影响。为了验证本文方法的性能,设计了刚体位移实验、铝片拉伸实验、单孔试件拉伸实验三个力学应用实验,通过对比理论值和实验值进一步验证了本文数字散斑相关测量方法的有效性和实用性。
[Abstract]:Digital Speckle Correlation method (DSCM) is a new type of optical measurement technique developed in 1980s. Its basic principle is to obtain the displacement and strain field of object surface by comparing the changes of speckle images before and after deformation. After more than 30 years' development, the method has been widely used in aerospace, non-destructive testing, micro-scale deformation measurement because of its advantages of full field, non-contact, high precision, sensitive measurement and wide range. Deformation measurement in high temperature environment, electronic packaging and many other fields. The primary problem of the digital speckle correlation method is to search the whole pixel. In this paper, the cross search method is used to search the displacement of the whole pixel. Because of the complexity of the process of determining the main peak area by the cross search method, the calculation amount is large. According to the continuity of displacement, this paper improves the selection method of the main peak region, assigns the initial value of the main peak region to the related calculation result of adjacent points, which greatly reduces the calculation amount and improves the calculation efficiency. Subpixel search is a key problem in digital speckle correlation technology. In this paper, the improved gradient method based on gray level change function is combined with the surface fitting method in sub-pixel correlation search. The introduction of gray change function weakens the influence of light intensity change on the measurement accuracy. The method improves the accuracy of subpixel displacement measurement and the stability of the algorithm is also improved. In this paper, the least square fitting method, which has high precision and little calculation, is chosen to calculate the strain of the object according to the displacement. In addition, the effects of three factors, such as the size of the subregion, the interpolation magnification and the noise, on the accuracy of the digital speckle correlation method are analyzed. In order to verify the performance of this method, three mechanical application experiments were designed, including rigid body displacement test, aluminum sheet tensile test and single hole tensile test. The validity and practicability of the digital speckle correlation measurement method are further verified by comparing the theoretical and experimental values.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP391.41

【参考文献】