Automatic measuring method for percentage elongation after single-shaft tensile fracture of metal round bar sample

Abstract

The invention discloses an automatic measuring method for percentage elongation after single-shaft tensile fracture of a metal round bar sample and belongs to the technical field of mechanical property test of metal materials. According to the method, on the premise that the elasticity modulus and the poisson ratio of a material are known, only gauge length elongation and a load value at the tensile fracture moment of the round bar sample need to be measured and recorded, meanwhile, an optical method is adopted to collect the outer contour curve of the round bar sample after fracture, and thepercentage elongation after single-shaft tensile fracture of the metal round bar sample is obtained through elastic deformation analysis and calculation. According to the method, the elastic part is accurately deducted, without the need of identifying the fracture position in the gauge length range, a shifting method is automatically implemented, so that the percentage elongation after fracture isaccurately obtained. Compared with the existing manual measurement technology, tedious measurement links such as scribing and fixing the fracture sample are omitted, the measurement precision is improved, and great significance is achieved for mechanical property test of the metal material.

Description

technical field [0001] The invention relates to the test of the mechanical properties of metal materials, in particular to a method for automatically measuring the elongation of a metal round bar 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...

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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