Method for measuring residual stress of composite material annular part based on cutting and bending method

Abstract

The invention discloses a method for measuring the residual stress of a composite material annular part based on a cutting and bending method. The method comprises the steps that the annular part is cut off in the radial direction, a strain gauge is used for cutting off the stress variation on the front surface, the rear surface, the inner surface and the outer surface, constant speed loading is conducted on the cut-off part to enable the cut-off part to be bent, meanwhile, the continuous stress variation on the inner surface and the outer surface in the loading process is recorded, and the annular and the radial residual stress of the part is obtained at last according to force and bending moment balanced boundary conditions. According to the method for measuring the residual stress, the defect that the material characteristic parameter of materials needs to be known in a traditional lossy measuring method is overcome, and the complex degree of the material parameter measuring process is obviously lowered particularly for the characteristics that the inside materials of the composite materials are not even and material parameters are not uniform.

Description

Technical field: [0001] The invention relates to a method for measuring the residual stress of a composite material annular part based on a cutting and bending method, which belongs to the method for measuring stress in the field of mechanical engineering. Background technique: [0002] The residual stress of composite materials usually refers to the stress remaining inside the material during preparation and processing. The existence of residual stress will have a huge impact on the performance of composite materials, such as causing various defects inside the material, changing the mechanical, physical and chemical properties of the material, reducing the dimensional stability of the material, etc., which will seriously affect the performance and performance of the material. service life. Therefore, the research and characterization of the residual stress of composite materials has always been an indispensable content in the research and application of materials. In the ...

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Problems solved by technology

[0005] Among the above non-destructive measurement methods, their suitable occasions are restricted to varying degrees.

For example, ordinary X-ray diffraction cannot penetrate deep into the material. Although neutron diffraction or synchrotron X-ray radiation has strong penetrating ability and powerful functions, such expensive technical equipment is very rare and difficult to be widely used. , laser Raman spectroscopy and magnetic strain method are all measurement methods for specific materials, and the synchrotron radiation method has too strict requirements on equipment, which limits its wide application

[0006] The equipment required by the destructive testing method is neither expensive nor harsh, and has high precision in most cases, but it requires specific parameters of the material of the tested part. For composite materials in the manufacturing process, the characteristics of the material are often It is not unique, and sometimes even the characteristics of each layer of material are different. In this case, it is difficult to measure the internal residual stress of the material with traditional destructive testing methods, and its accurate value cannot be measured

The traditional method removes part of the material, releases part or all of the residual stress and causes the corresponding displacement and strain, and then measures these displacements or strains in some parts, and calculates the original residual stress through mechanical analysis. This process requires the measurement of composite Some properties of materials, such as elastic modulus and Poisson's ratio, etc., and these properties of composite materials are often not unique. They are often affected by many factors during the manufacturing process, and it is impossible to guarantee that the material properties of the final part are unique. Sometimes Even the characteristics of each layer of material in the same part are different, so the inherent difficulties in the measurement of specific material parameters have caused the traditional method of residual stress measurement to be severely restricted

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