True Stress-True Strain Testing System Optimization And Experimental Research

Using visual technology and image analysis methods to develop the non-contact measurement technique applied in the mechanical properties testing is the target of this object, the main work of this topic is to consummate and improve the corresponding performance on the basis of the preliminary testing work, in order to improve the system's reliability and stability.Along with the continuous development and improvement of relative hardware and software, machine vision technology has been increasingly involved in various fields. In the field of non-contact measurement, visual technology has great potential and superiority. For the limitations of contact measurement, in the mechanical properties and structural testing areas, direct measurement of too many performance parameters are difficult to carry on, for the urgent need of non-contact measurement, true stress-strain test which is both traditional and practical is just one of such problems. The research of this project based on the measurement system using visual technology and image analysis methods can perfectly solve this problem, realize the true meaning of true stress-strain direct measurement.In this paper, creatively using the micro-element analysis theory of the largest plastic deformation, using the technique of optic and the method of imaging analysis, designed the new measurement and analysis of true stress-strain method. Preliminary work for major projects completed based on the basic development of hardware and software, confirmed the feasibility of such method. This paper focuses on improving and adjusting the software, through median filtering, threshold and morphology, and on the basis of rough edge location, I tried to use sub-pixel processing algorithms on the collected images, through precision positioning applications to enhance the image edge detection accuracy and reliability, acquired an accuracy of sub-pixel level of the measurement, and met the minimum diameter accurate measurement of the practical application requirements; According to practical application of measurement, configuring the hardware properly, the size of resolution of system can reach 0.1~0.001mm so that satisfying different tested specimen whose minimum diameter can be precisely measured; using multi-thread mode of information transmitting to replace the former one's parallel processing method using a shared RTSI bus signals to trigger the multi modules, make the smallest diameter and the output load are synchronous collected and processed in measurement process at arbitrary moment, thereby improve the measurement system stability and reliability; systematically studied the setup of the practical application of light, using different light cast and shade, optimized a light source layout that can effectively prevent a large quantity of central reflection and marginal blooming phenomenon. Resolved the problem of the environment's adverse effects during measuring, provided a guarantee for an accuracy of practical measurement; Finally, using the results of this research, carried a test on Q235 steel sample and the 5083 aluminum alloy sample and obtained the desired results, by comparing with the results derived from the engineering stress-strain and traditional true stress-strain analysis, come to a conclusion of the true stress-strain can be accurately measured by our system.