Mechanical Engineering Faculty Research


In-plane Bulk Material Displacement and Deformation Measurements using Digital Image Correlation of Ultrasonic C-scan Images

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The extension of digital image correlation method to ultrasonic C-scan acoustical speckle images of the bulk is presented in this paper. The approach discussed in this paper is ideally suited to composite materials such as particulate composites, fiber-reinforced plastics, and laminated composites. It can also be effectively employed for critical surfaces that are not within view, such as interfaces and back surfaces. Images taken prior to and after deformation are analyzed to estimate a deformation profile from changes in the image. The aim of the method is to find the displacements and strains of small subsets from the second image relative to the first one. This is accomplished by comparing the intensity levels of the subsets in the images. The speed and accuracy of the system is enhanced by the genetic algorithms(GAs) which are used to optimize correlation of images. An ultrasonic C-scan system was used to obtain the intensity images of the front or back surface of an isotropic or composite material. Three experimental tests were conducted to illustrate the application of Ultrasonic C-scan digital image correlation method. These tests include: 1) uniform translation, 2) small angle rotation, and 3) uniform deformation. A laminated carbon/epoxy composite panel (305×305×8 mm) was used for uniform translation and small angle rotation tests. A rubber specimen was used to perform the uniform axial deformation test. The results of correlated displacements (angles) are compared to the actual displacements (angles). The accuracy and applied limitation of the three experiments are also illustrated in this paper.

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Structural Engineering and Mechanics





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