数字散斑相关方法用于圆盘表面热变形测量

为了克服压力应变片测量热变形的不足,采用DSCM(数字散斑相关方法)对静止空心圆盘仅承受外缘热载荷时的表面热变形进行实时测量.实验系统中,采用电磁感应加热方式实现圆盘热边界条件的加载,并通过红外热像仪采集圆盘的实时温度分布数据.同时,为提高DSCM的测量精度,从CCD(charge coupled device)相机视场范围的选取、中焦距微距镜头的使用以及光源的布置等方面来降低离面位移和散斑质量等误差因素的影响.盘面热变形 位移的实验结果与理论结果的对比显示,两者符合较好,但仍存在一定偏差,最大绝对偏差为6μm,最大相对偏差为31%;盘外缘绝对偏差较大而相对偏差较小,盘内缘反之.对比结果验证了DSCM用于圆盘表面热变形测量的可行性,从而为涡轮盘盘面热变形研究提供了一种有效的实验工具. 

Application of digital speckle correlation method to disk surface thermal deformation measurement

To overcome the limitations of thermal deformation measurement conducted by strain gages, the DSCM (digital speckle correlation method) was used to determine the real-time surface thermal deformation of a static hollow disk subjected to thermal load on the outer rim. In the experiment system, electromagnetic induction heating method was applied to simulate the heat boundary of the disk and the real-time temperature distribution of the disk was obtained by infrared thermometer. Meanwhile, for the purpose of improving accuracy of DSCM, measures were taken by considering the range of field of CCD (change coupled device) camera view, the usage of medium focal length micro lens and the arrangement of illumination to lessen the effects of error factors like off-plane displacement and speckle image quality. The comparison between the experimental and theoretical results of thermal deformations shows that a good agreement is achieved, although some deviations still exist, and the maximum absolute deviations and relative deviations are 6μm and 31%, respectively; the absolute deviations of the outer rim are larger while the relative deviations are smaller,and this case is contrary to the inner rim. The results validate that the feasibility of DSCM for disk surface thermal deformation measurement, thus providing an effective experimental tool on turbine thermal deformation investigations.