Automatic measurement method of percentage elongation after fracture of metal plate specimen during single-axis stretching

Abstract

The invention discloses an automatic measurement method of the percentage elongation after fracture of a metal plate specimen during single-axis stretching, and belongs to the field of mechanical properties of metal materials. According to the test method, under the premise of knowing the elasticity modulus and poisson ratio of a material, only the scale distance elongation and the load value of the plate specimen at the stretching fracture time need to be measured and recorded, meanwhile, distribution information of the outer contour of the plate specimen after fracture in the width and thickness directions is collected through an optical method, and the percentage elongation after fracture of the plate specimen during single-axis stretching is calculated through elastic deformation analysis. According to the automatic measurement method, an elastic part is accurately deducted, an automatically implemented shift method for identifying the fracture position within the scale distance range is not needed, and thus the percentage elongation after fracture is obtained accurately. Compared with an existing manual measurement technology, tedious measurement links such as line drawing andfixing of the specimen after fracture are omitted, the measurement precision is improved, and the automatic measurement method is of great significance to test the mechanical properties of the metalmaterials.

Description

technical field [0001] The invention relates to the test of mechanical properties of metal materials, in particular to a method for automatically measuring the elongation rate of a metal plate sample after uniaxial tension. Background technique [0002] Among the mechanical properties of metal materials, the elongation after fracture is an important index reflecting the plasticity of metal materials. The larger the value, the better the plasticity of metal materials. There are two main ways to measure the elongation after fracture: manual and automatic. GB / T228.1-2010 stipulates the determination method of elongation after fracture. The manual measurement method is: carefully match the fracture parts of the tensile specimens together, so that the axes are on the same straight line, and ensure that the fractured part of the specimen is Measure the gauge length after fracture of the specimen after proper exposure u , the gauge distance after breaking l u and the original ga...

AI Technical Summary

Problems solved by technology

The automatic measurement method is simple and feasible, but the extensometer cannot automatically identify the fracture position of the sample

However, in the actual test process, most of the sample fracture positions are not at the extensometer gauge length l e In this case, the automatic measurement cannot be corrected by the displacement method like the manual measurement, and the measured elongation Δl will be smaller than the manual measurement

At the same time, due to the serious necking of the sample when it breaks, if the elastic deformation is calculated according to the uniform deformation when deducting the elastic part, the deducted elastic part is inaccurate

In view of the above two reasons, although the current automatic measurement of the elongation after fracture is simple and feasible, it has a large error. In practical applications, manual measurement is still mostly used.

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