Test method for uniaxial constitutive relation of ductile material

Abstract

The invention discloses a method for determining the large deformation uniaxial constitutive relation of a material based on the energy principle and a P-V curve obtained by stretching a central circular hole plate specimen. The method comprises the following steps: performing quasi-static tensile test on a central circular hole plate specimen to obtain a continuous P-V curve, and determining the elastic stiffness S, the feature load P* and the displacement index m by the curve so as to obtain the large deformation uniaxial constitutive relation of the material. The method disclosed by the invention is applicable to a ductile material with an isotropic strengthening and constitutive relation according with the power law, wherein the structure of the central circular hole plate specimen is special, namely during the tensile test, the circular hole edge center point material unit of the specimen is under uniaxial stress state before the occurrence of necking; compared with an equidistant specimen, the method disclosed by the invention is easier to implement, and the obtained uniaxial stress-strain relation is wider in range; the method has great significance on the engineering structure design and safety assessment work.

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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