A method for ultrasonic measurement of surface stress tensor of rolled metal materials

Abstract

A method for ultrasound measurement of surface stress tension of a rolled metal material comprises the following steps of S1, calibrating a relation curve between an orientation angle x and zero stress sound moment t0; S2, calibrating a nominal sound elastic coefficient K<parallel> of a stretching sample parallel to a rolling direction and a nominal sound elastic coefficient K<perpendicular> of the stretching sample perpendicular to the rolling direction; S3, placing ultrasound probes on a surface of a to-be-detected workpiece per an orientation angle Delta Beta to obtain critical refraction wave propagation time t (j. Delta Beta) corresponding to [90 / Delta Beta] groups of orientation angle j. Delta Beta of the to-be-detected workpiece; S4, respectively recording two mutual-perpendicular main stress of surface stress tension of the to-be-detected workpiece as Sigma 1 and Sigma 2, and obtaining [(90 / Delta Beta)-1] non-linear ternary equation sets according to a relation formula, whereinan angle formed between the Sigma 1 and the rolling direction is Theta; and S5, solving the non-linear ternary equation sets in the step S4 to obtain a solution set [Sigma<1><>, Sigma<2><n> and Sigma<3><n>] of [(90 / Delta Beta)-1] elements, and calculating a solution set central point of the [(90 / Delta Beta)-1] elements to obtain surface stress tension [Sigma 1, Sigma 2, Theta] of the to-be-detected workpiece. The method is simple and convenient and is low in cost, and the shallow surface stress tension of the rolled metal workpiece is accurately measured.

Description

technical field [0001] The invention relates to a method for ultrasonically measuring the surface stress tensor of rolled metal materials, belonging to the technical field of ultrasonic nondestructive testing. Background technique [0002] Metal materials will inevitably produce plastic strain during the mechanical manufacturing process, resulting in residual stress. At the same time, during the service process of the workpiece, the interior of the workpiece is affected by aging or external loads, and the stress will change. Measuring the surface stress of the workpiece can not only provide data support for the safety evaluation of the structural service, but also improve the production process and component processing methods on this basis to further extend the service life of the workpiece and reduce production and operation costs. [0003] There are many kinds of stress detection techniques in objects, which can be subdivided into three categories according to whether the...

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Problems solved by technology

[0005] In the existing ultrasonic residual stress measurement technology, the measurement direction is assumed to be the main stress direction, but in actual engineering applications, the stress field distribution of workpieces with high stress control requirements is complicated, making it difficult to determine the main stress direction, such as pressure vessels, high-speed rail bogies , rail train body, etc.

In the field of reliability assessment of engineering structures, accurately obtaining the magnitude and direction of principal stress at dangerous locations is a prerequisite for calculating the service life and safety of engineering structures; For rolled metal materials, due to the rolling process, the grains in the rolling direction are elongated and the properties of the material change. Therefore, rolled metal materials are anisotropic materials, and the existing technology cannot measure their surface stress tensor. , so the rapid and non-destructive measurement of the stress tensor on the surface of rolled metal materials has great engineering application value

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