Volume 10, Issue 2 (March 1982)
Statistical Analysis of X-ray Residual Stress Measurement Using the Half-Width Method
X-ray stress measurement can be used to nondestructively measure the residual stress in small areas of metallic materials. The equation for calculating the standard deviation of the stress as a result of statistical counting errors σS which are a fundamental source of scatter in X-ray stress measurements, is derived for the half-width method using the preset time technique. This equation shows that σS is independent of the half-width of the diffraction line but is inversely proportional to the slope of the line side. Residual stresses in the three hardened steels, JIS S35C, S45C, and SK3, were determined by three methods, that is, the parabola and the Gaussian curve-fitting methods and the half-width method. The stress values determined by the three methods agreed well with each other. The standard deviation σS determined by the half-width method is smaller than that determined by the curve-fitting methods for most materials, but it becomes larger as the diffraction line broadens.