Testing method for automatically measuring thickness thinning rate by adopting tensile testing machine

Abstract

The invention discloses a testing method for automatically measuring a thickness thinning rate by adopting a tensile testing machine. The tensile testing machine is a tensile testing machine with longitudinal and transverse extensometers; the testing method comprises the following steps: 1) testing an original initial thickness a0, an initial width b0 and an initial length L0 of a test sample; 2) clamping the test sample to be tested onto the tensile testing machine with the longitudinal and transverse extensometers and recording instant sizes L and b of the test sample to be tested in a length direction and a width direction in a whole tensile testing process; solving real-time longitudinal strain eL and transverse strain eb respectively; 3) calculating the instant thickness thinning rate of the tensile test sample; 4) setting a maximum force total elongation rate Agt and a maximum force plastic elongation rate Ag, and calculating to obtain a maximum force total thinning rate and a maximum force plastic thinning rate; 5) defining a thinning rate at a fractured minimum thickness part after testing as a fractured thinning rate etau; testing a minimum thickness au of a necking region of a fractured test sample through a point micrometer; calculating the fractured thinning rate etau. The testing method disclosed by the invention is convenient and rapid and is suitable for large-batch inspection.

Description

technical field [0001] The invention relates to the technical field of testing the mechanical properties of metal materials, in particular to a testing method for automatically measuring the thickness reduction rate by using a tensile testing machine. Background technique [0002] In the current standards related to tensile testing, neither the national standard GB / T 228.1-2010 nor foreign standards stipulate the test item or index of thinning rate. In fact, the thinning rate is very important not only for the forming and processing of thin-walled pipes and thin plates, but also for the fracture failure analysis of thick-walled pipes and thick plates. In theory, it can be used as the design control basis in the material manufacturing process and the criterion for structural failure analysis. In theory, it can also be used as a criterion for predicting the forming limit and fracture of materials. [0003] In addition, in the field of sheet metal strip forming processing, the...

AI Technical Summary

Problems solved by technology

These two methods are manual measurement methods. Method 1 has a complicated sample preparation process and low test efficiency; Method 2 has a simple test process and convenient operation, but there are too many manual measurement points, and the later data processing is also cumbersome, and manual measurement errors are relatively large. , affecting the test accuracy

[0005] The difficulty in testing the thickness reduction rate of metal sheets in tension lies in: 1) There is no ready-made test method record on the thickness reduction rate in various national or international standards for mechanical testing; 2) In the existing literature, metallographic mounting samples in The method of testing the thickness reduction rate under a microscope has complicated sample preparation process and low test efficiency, which is not suitable for large-scale production inspection and is only suitable for laboratory research; 3) the method of measuring the thickness reduction rate with a pointed micrometer in the existing literature The test process is simple and the operation is convenient, but there are too many manual measurement points, and the later data processing is also relatively cumbersome, and the manual measurement error is large, which affects the test accuracy

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