A test method for uniaxial constitutive relation of ductile materials

Abstract

The invention discloses a method for measuring the large-deformation uniaxial constitutive relationship of a material based on the energy principle and the P-V curve obtained by stretching a central circular hole plate sample. The quasi-static tensile test was carried out on the central circular hole plate sample to obtain the continuous P-V curve, and the elastic stiffness S, characteristic load P* and displacement exponent m were determined through the curve, and then the large deformation uniaxial constitutive relationship of the material was obtained. The present invention is applicable to ductile materials with isotropic strengthening and whose constitutive relation conforms to the power law, wherein the structure of the central circular hole plate sample has particularity, that is, during the tensile test, the material unit at the center point of the circular hole edge of the sample It is in a uniaxial stress state before the necking occurs. Compared with the straight sample, the invention is easier to implement, and the obtained uniaxial stress-strain relationship has a wider range, which is of great significance to engineering structure design and safety assessment.

Description

technical field [0001] The invention relates to the testing of mechanical properties of materials, in particular to a method for testing the uniaxial constitutive relationship of ductile materials. Background technique [0002] The uniaxial constitutive relationship of ductile materials (i.e., the tensile stress-strain relationship) is the basic physical relationship for structural analysis and engineering design using the continuum mechanics method, and is also an important "link" linking materials and mechanics. and safety evaluation play a key role; in the traditional tensile test, the real cross-sectional area and gauge length of the straight section of the sample are constantly changing during the tensile test, after the sample appears necking, the necking position The material is no longer in plane deformation, and the engineering stress-strain curve of the gauge section shows a trend that the engineering stress decreases sharply with the increase of the test strain; i...

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Problems solved by technology

[0002] The uniaxial constitutive relationship of ductile materials (i.e., the tensile stress-strain relationship) is the basic physical relationship for structural analysis and engineering design using the continuum mechanics method, and is also an important "link" linking materials and mechanics. and safety evaluation play a key role; in the traditional tensile test, the real cross-sectional area and gauge length of the straight section of the sample are constantly changing during the tensile test, after the sample appears necking, the necking position The material is no longer in plane deformation, and the engineering stress-strain curve of the gauge section shows a trend that the engineering stress decreases sharply with the increase of the test strain; in fact, although the response load will decrease after the sample is necked, the material is However, it is still hardening during the process, and the real stress is constantly increasing. The center point of the cross-section of the necking area of ​​the sample is already in a triaxial stress state; The stress-strain relationship of

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