Method for testing residual stress of thick plate by neutron diffraction technology

Abstract

The invention provides a method for testing residual stress of a thick plate by a neutron diffraction technology. According to the method, in allusion to crystal structures and elemental components ofdifferent test materials, corresponding relationships among the Bragg edges, the total neutron absorption cross sections and the wavelengths of the test materials are calculated; through calculationof the corresponding relationships among the Bragg edges, the total neutron absorption cross sections and the wavelengths, several wavelength values which can increase the penetration depth of neutrons in a thick plate sample are determined; the texture of the sample is tested, a preliminary test wavelength according to a test result of the texture is selected, and corresponding optimal wavelengths of the test sample in a transmissive mode and a reflective mode are selected according to a peak height / background value, a strain error value, a total neutron count and the actual neutron penetration path length; through change of the wavelengths, the penetration depth of the neutrons in the thick plate sample is increased, the test time is shortened, a test error is reduced, and the residual stress of the thick plate is accurately tested. In a way of changing the wavelengths, the penetration ability of the neutrons in the thick plate sample is improved, the efficiency of testing the residual stress of the thick plate through neutron diffraction is improved, the test time is shortened and the test error is reduced.

Description

technical field [0001] The invention relates to the technical field of neutron diffraction testing of residual stress, in particular to a method for testing the residual stress of a thick plate using neutron diffraction technology. Background technique [0002] With the development of industrial equipment in the direction of high efficiency and large scale, the demand for thick plate structures in petrochemical, nuclear power, shipbuilding, aerospace, construction and other industries continues to increase. The thick plate structure may be subjected to processes such as welding, solid solution, quenching, and aging treatment. Due to multiple thermal cycles, large welding constraints, or large gradient temperatures, the internal stress distribution is complicated and changes drastically, forming a large residual tensile stress. The existence of residual tensile stress will cause process defects such as hot cracks, cold cracks, and brittle fractures. Under certain conditions,...

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Problems solved by technology

However, the maximum size of the specification volume is limited by the resolution required by the test, and the test time cannot be effectively increased due to the limitation of the opening time

And the neutron intensity decays exponentially with the length of the neutron penetration path, increasing the gauge volume and test time plays a very limited role

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