Application Of Digital Image Processing In Experiment Mechanics

Coincident with the rapid development of modern optical and computer technologies, especially in recent two decades, is a birth peak of new optical methods and techniques in the family of experimental mechanics. (Quite a few new optical methods and techniques in the field of experimental mechanics arise from the rapid development of modern optical and computer technologies, especially in recent two decades.) Meanwhile, digital image processing has been an indispensable part of the photomechanics today. It is more and more popular to acquire and process digital images by applying a portable mini-system controlled by a personal computer. This makes it significant to increase the computing speed, the automatic and intelligent degree as well, of the whole digital image processing system. In this thesis, the main concerned problems are, firstly, to deeply investigate the digital image processing technologies of both digital speckle correlation method (DSCM) and digital Moirémethod, and then to design a set of integrated software system for the experimental measurements through the two methods above.First of all, the pre-locating technique based on nonlinear transform, and its perspective application as well, is investigated in order to increase convergent speed and improve the precision widen applicable range of digital speckle correlation method. The algorithm of this technique may erase most of those unnecessary searching works, and directly educes both the rigid displacement and the approximate displacement arising from the deformation of each sample point in the reference image. The processing result shows that the pre-locating technique might improve the searching efficiency and identifying quality, and reduce the probability of miss-identification effectively at the same time. Moreover, it is successful applied in the measurement of displacement field with large turning angers. Furthermore, by integrating the algorithm above into the existing software version, and then adding some useful functions such as image pretreatment and result visualization, a multi-functional measurement software of digital image correlation, with a friendly and convenient operating interface, is developed.Digital Moiréis a non-contact and full-field photomechanical method. It is well developed and widely applied recently, owing to the great technologic progresses in the fields of photoelectricity, computer science and digital image processing. An integrated software is programmed in this work to increase the computing accuracy, processing speed and automatic degree of the experimental measurement by means of digital Moiré. This software can process the parallel/annular/radial gratings easily, efficiently and effectively, and calculate the displacement field and strain field, and then display them by visual figures.Besides, based on existing equipments of our laboratory, another set of software for acquiring image is finished, which is applicable for catching images in quasi-static condition. This software is quite friendly and convenient, and it may be much helpful for the experimental works of our research group.