Intelligent Remote Sensing of Deformation and Strain Pattern of Flexible Structures

为了对穹顶结构或空间结构等变形结构进行评估，研制了一套变形应变分布测量系统。本研究开发的系统由材料检测部分和图像处理部分组成。在材料部分，构造了一种新型的试验机，其夹持件可以在两侧对称移动，从而使观察区域在加载时不会向一个方向移动。图形的变形由VCR摄像机记录下来，并在测试后传输到微型计算机。第一种方法是在试件表面印刷一个点阵图案，并利用基于神经网络的图像识别技术搜索交叉点。在实际的图像数据中，噪声的影响是无法消除的，因此需要进行人工处理来弥补图像识别的不足。应变分布的确定是通过应用有限元方法中使用的类似方法来执行的。在第二种方法中，在试件上打印一个随机的点图案，通过与变形前后的图像数据进行匹配来评价试件的诽谤程度，并应用该方法来研究塑料薄膜局部加热产生皱纹的机理。图像处理结果与有限元分析结果吻合较好。结果表明，主应力负值的大小可以作为预测起皱的一个合适的临界参数。

A measuring system of deformation and strain distribution has been developed in order to evaluate the deformable structures such as dome structure or space structure. The system which is developed in this study is composed of the material testing section and the image processing section. In the meterial section, a new type of testing machine has been constructed in which the chacking parts can move symmetrically on the both side, so that observation region does not move during loading in one direction. The deformation of the pattern is recorded by a VCR camera and is transmitted to the micro-computer afrer the tests.The two types of image processing methods have been considered. In the first method, a lattice pattern is printed on the specimen surface and a cross point is searched by the image recognition technique base on the neural network. In the actual image data, the influence of the noise can not be removed, so that a manual treatment is required to compensate the lack of the image recognition. Determination of the strain distribution is performed by applying a similar method used in the finite element method. In the second method, a random dot pattern is printed on the specimen, the defamation of the specimen is evaluated by the pattern matching the image data before and after deformation.The present method is applied to study the mechanism of wrinkle formation due to localized heating of thin plastic films. The good agreement is obtained between the results of the image processing and finite element analysis. It is found that the magnitude of the negative value of principal stress could be used as an appropriate critical parameter for predicting initiation of wrinkle.