A method for measuring the true stress-strain curve of metal welded structures

Abstract

A measuring method for a real stress-strain curve of a metal welding structure comprises the steps: firstly, measuring a real stress-strain curve of a notch tensile test, wherein a real fracture strain at a maximum load is a strain hardening index of a metal of a to-be-measured position; calculating real stress-strain curves of notch tensile samples by finite element calculating software, to obtain the real stress-strain curves of the notch tensile samples with different notch sizes, fitting and establishing the relationship between the notch size and a geometric factor, and establishing a geometric factor expression containing the notch size and the real fracture strain at the maximum load and other influence factors; according to a load separation theory and the obtained relational expression and expression, the real stress-strain curve of the metal of the to-be-measured region of the metal welding structure is obtained. Through the small-size notch tensile test and a series of established relationships, the locality of the to-be-measured material region is accurately transmitted to a whole single-region material.

Description

technical field [0001] The invention belongs to the technical field of materials, and in particular relates to a method for measuring the true stress-strain curve of a metal welded structure. Background technique [0002] For welded structural parts, the material is heterogeneous in nature, and the mechanical properties of the base metal, weld, and heat-affected zone are different. The full true stress of each material area is required for fracture evaluation of welded structures. true strain curve. Due to the economy and convenience, the transverse tensile test of welded joints is widely used in the evaluation of weld quality. For example, the occurrence of fracture failure in the base metal represents good weld quality, while the occurrence of fracture failure in the weld metal or the heat-affected zone indicates that the weld Seam quality is poor. The transverse tensile test of welded joints can record the relationship between load and axial elongation. Obviously, this ...

AI Technical Summary

Problems solved by technology

But there are following defectives in this document: 1. the applicability of this method has been subjected to the limitation of this test method, such as sample size and local area size to be measured, the applicable sample thickness of this method is only 0.8-2.0mm, and width is 10mm

Taking steel pipe welded joints as an example, the thickness is often between 10mm-25mm, and the width of the heat-affected zone of the welded joint and the weld seam is about 2mm, which means that the geometric size factor has a great influence on the applicability of the method. limit

2. This method cannot reflect the tensile properties of the material after necking, that is, as mentioned in the conclusion of the literature itself, the mechanical properties beyond the strength limit have not been studied, that is to say, the true stress-strain curve obtained by this method is not complete

[0005] In the prior art, there is a problem of obtaining the true stress-strain curves of the heat-affected zone and the weld zone in the welded joint for the actual effect evaluation of the welded structure

Images