An Algorithm For Testing The Target's Precision Edge In Strain Measurement In Material Tensile Experiment

Strain is one of the important parameters in material measurement, so deformation measurement is a crucial link in solid mechanics and material science. One of the important subjects in material mechanics is to explore and predict the mechanical behavior of the material by building the constitutive relation (the stress-strain relation). Thus, obtaining the strain is crucial to build a correct and effective constitutive equation for the material. In experimental mechanics, the strain is not obtained directly, but through a calculation which is on the bases of the absolute measurement of the deformation, according to relative definition of the strain. Therefore, the accurate, fast and efficient measurement of the deformation is an important research topic in experimental mechanics.Normally, Load imposed on the specimen as well as measuring by mechanical extensometer Clamping on the Specimen in Practice. For rigid material,strain can be measured by using traditional mechanic clamp-type extensometer or thin-type Extensometer. But these equipments can not be used in the measurements on fiber,film,foam or soft plastic material. These material's weight and clamping method may effect the experiment results and the breakpoint. In many cases, the performance of the material with super strain range should be measured and obtained. Limited by the itinerary, mechanical extensometer should be removed before the fracture of the specimen. For the specimen under some specific circumstances ,such as the high temperature, the use of mechanical extensometer is limited. In order to reduce the measurement error, improve the measurement accuracy and improve the practical scope of application,We explore the forefront of the method of images measurement to carry out the research projects in this experiment.This paper tests the real-time strain in material extruding experiment by using the graphic measure method indirectly in the context of material extruding experiment of material mechanics. This belongs to the scope of the dynamic image measurement. Therefore, in the research, according to the characteristics of dynamic images, it is necessary to meet the test of measurement accuracy and ensure the measurement real-time performance. The paper makes depth study on precision edge detection algorithm of material extruding strain test experiment. Based on the mature wavelet transform theory, Expectations of sub-pixel wavelet transform algorithm has been applied to the paper successfully. This paper's main works are as follows:1.In the context of material extruding experiment, the video graphic strain measurement system based on the paper's research has the advantage of higher accuracy, lower cost, and non-touch test comparing with the traditional mechanical extensometer.2.Under the premise of the existing experimental apparatus, the key technology is how to improve the accuracy of video graphic strain measurement system by doing research on precision subpixel edge detection algorithm. The software design method decrease the hardware cost of experimental apparatus and meanwhile build a scientific and forehanded environment.3.Based on the perfect wavelet transfom theory, by using of the idea of wavelet transfom, sub-pixel wavelet transfom expectations location algorithm is proposed and used as sub-pixel new algorithm for developing video image strain measurement system. The first-order differential expectations of sub-pixel algorithm and one-dimensional sub-pixel gray-level moment algorithm are introduced too. This is the base of the step-experiment.4.According to the algorithm's math model, the experiment is carried out under the Windows XP operating system and software coded with Visual C++. Through analyzing the experiment results, it is proved that the wavelet transform expectations location algorithm has higher accuracy compared with other algorithms.5.By analyzing the results of different image collection frequency of wavelet transfom expectations location algorithm, we can obtain that the data error becomes bigger with the collection frequency becoming higher under the fixed illumination, distance and focus. If the frequency is 30 frame/second, the error can not be out of range. This shows that the wavelet transfom expectations location algorithm has met with the real-time performance requirements. 6.The experiment error has been systematically analyzed in this paper, such as illumination error,image measurement error and algorithm error. And some constructive ideas are proposed in order to decrease error number.Scientific development is endless. The science will develop towards the cross-cutting and diversification. This paper covers a number of areas of scientific knowledge. With the development of mathematics,electronics, mechanics, optics and computer technology, the topic researched by the paper will have tremendously development.Image measurement is a widely used precision measurement technology. And the paper applies this technology to the material extruding real-time strain experiment and I hope that the research on video image strain measurement precision edge detection algorithm can improve the development of the future image measurement technology.