Influencing Factors on Measuring Surface Residual Stress of Steel Bars by X-ray Diffraction Method

The surface residual stress of mechanical parts and large mechanical components has an important influence on their fatigue strength, stress corrosion resistance and service life. X-ray diffraction method is used to measure the surface residual stress of steel bars and the influence of factors such as testing methods, testing equipment status and sample status on testing results is discussed in this paper. The results show that the testing parameters such as the target material, filter, diffraction angle and the minimum step shall be selected according to the material type and crystal structure under the premise of stable operation of the equipment in testing process. After that, the data treatment is under consideration. The peak determination is a very important part of data processing. The cross-correlation method is widely used because it uses all the original test data for the calculation, and the accuracy of the peak determination is high in this test. It also shows that the sampling process and specimen protection can also affect the testing results of the residual stress. The structure state of materials will have a great impact on testing results. For example, the texture will cause excessive errors of the testing results. It is recommended to understand the material properties in detail before testing so as to ensure sufficient margin when sampling, to apply the strict protection for the test surface of the sample, and to add a swing angle appropriately when the material is with texture.