Research On Materials Test Technology Of Real Stress-Strain Based On Machine Vision

The plasticity and tenacity of materials play an important part in its parameters. True stress-strain curves explain the law of plasticity in the processing of tension, which are the important theory foundation defining the broking strength and ability anti-deformation. However, traditional methods of measurement have consistent limitations in test true stress-strain curves. Therefore, develop an up to date test method is valuable.Machine vision is a new detecting technology. Acquire images by using CCD, then obtain the parameters detected by image processing, this non-contact method is used all kinds of fields widely.This paper design a materials non-contact test system of true stress-strain based on machine vision. This system solved necking point snap accurately and minimum section area calculation through real time tracking tension process. The method of measurement directly and stress calculation is discovered, by which the true stress-strain curve can be obtained. This paper not only represent the design of hardware and software and but also make experiment analysis.First, this paper analyze the calculation method of true stress-strain,then design the whole structure of system according to machine vision and the principle of image processing. Secondly, the design of the hardware contains CCD camera, lens, image acquisition card and illumination system is specified. In this paper, the image processing method of the system is studied detailedly, such as median filter, thresholding, segmentation of the small hole, improvement of the binary image and edge detection. Meanwhile design the data acquisition system. Then compile the software program and generate the interface which can be operated and display. This system turn out to be true on the basis of typical metal specimens'experiment. Finally, the error of the whole system is analyzed and calculated so that the design will meet requirements.