Cold-rolled sheet residual stress prediction and measurement method

Abstract

The invention discloses a cold-rolled sheet residual stress prediction and measurement method, and belongs to the technical field of steel material stress-strain detection methods. According to the technical scheme, the method comprises the following steps: selecting two groups of cubic samples X with certain sizes of length * width * length from a cold-rolled sheet before forming by utilizing a linear cutting method; attaching a strain gauge or a strain rosette to the geometric center of the material in each group of samples along the rolling direction and the transverse direction respectively, and measuring the initial strain of each group of samples in the state; obtaining the relationship between the bending moment and the size change of the sample by using bending equipment and contour scanning equipment; detecting the curvature of the sample by using a contour scanner; obtaining the relationship between the surface strain and the curvature radius of the sample; and calculating the residual stress through a calculation formula. According to the method, the residual stress distribution in the thickness direction of the plate can be effectively predicted through a pure bending method, accurate data can be provided for subsequent cold rolling plate residual stress control, and therefore reliable technical support is provided for improving the product quality.

Description

technical field [0001] The invention relates to a simple and efficient residual strain and stress detection method, and belongs to the technical field of stress and strain detection methods for iron and steel materials. Background technique [0002] Modern industry requires iron and steel products to have high mechanical properties and shape accuracy requirements. Therefore, in the process of strip production and rolling, large reductions, complex roll surface curves and rolling process control are required, which will lead to existing problems after strip rolling. High residual stress and uneven distribution will affect the shape of the plate and the quality of subsequent deep-processing products. Excessive residual stress will lead to warpage due to insufficient flatness of the steel plate, which will affect the springback of the parts during forming and the stability of the welding process. Therefore, accurately predicting and measuring the residual stress in the steel p...

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Problems solved by technology

[0006] X-ray methods are very poorly penetrating and can only reach the surface of the material

Only suitable for small samples, there are radioactive safety issues, only the surface of the sample can be detected, the equipment is expensive, and it is not suitable for industrial applications

[0007] Neutron detection is considered to be the most accurate means of residual stress detection, it can detect the residual stress distribution along the thickness direction, and the measured strain accuracy can be as high as 10 -4 to 10 -5 . However, this method requires high investment costs, and the detection time is usually very long. At present, there are very limited civilian neutron detection equipment in the world, mainly concentrated in the United States, Europe, Japan, Australia and other developed countries

This method, like the X-ray method, is only suitable for small samples, has radiological safety issues, expensive equipment, and is not suitable for industrial applications

[0008] Ultrasonic testing method is not intuitive for the display of sample defects, the technical operation is difficult, the subjective and objective factors are greatly affected, the results are inconvenient to save, and the working surface is required to be smooth, which is mainly suitable for large samples

[0009] Therefore, several detection methods commonly used at present have great limitations, and cannot meet the prediction and measurement of residual stress in steel in the production of steel industry. How to quickly predict and measure residual stress in steel, especially the development and adaptation The detection method of industrial production has become a problem that plagues enterprises and technicians. So far, there is no effective solution, and technical personnel are urgently needed to carry out innovative research

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