Intelligent Remote Sensing of Deformation and Strain Pattern of Flexible Structures

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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.