X-ray diffraction characteristics of five materials for stress measurement

Abstract

This paper presents the laboratory X-ray diffraction characteristics of five materials: carbon steel (Q235), austenitic stainless steel (1Cr18Ni9Ti), martensitic stainless steel (A335P92), Al alloy (LY12), and Ti alloy (TA15) in X-ray diffraction stress measurement. The difficulty in accurately determining actual stress is illustrated by two diffraction peaks with low diffraction intensity that occur in laboratory X-ray diffraction stress measurement. Stress measurements by both laboratory X-ray diffraction and strain gauges methods were conducted by using uniform strength beams of the five materials. A comparison between measured results and analytical/theoretical results was made to examine laboratory X-ray diffraction characteristics of the five materials for stress measurement. The measurements show that austenitic stainless steel, Al alloy, and Ti alloy present two diffraction peaks in X-ray diffraction stress measurement. Although the CrKα diffraction peak of the {220} plane of austenitic stainless steel is apparent, the stress calculated from this peak does not represent the actual stress; however, the CrKβ diffraction peak of the {311} plane, in spite of the lower peak-back ratio, can be used to obtain the actual stress. For the Al alloy, only the CrKα peak of the {222} plane can represent the material's stress. Two diffraction peaks of the Ti alloy measured by CoK α radiation can be used to calculate its actual stress. Hence attention should be paid to which X-ray diffraction peaks can be used for actual stress determination.