A new method for measuring stress at local area of about 100μ in an diameter by the X-ray microbeam diffraction technique was proposed. The method can be regarded as an improvement of the single incident angle method and uses information on lattice strain along the whole Debye ring in order to determine the stress value. The accuracy of the stress value measured by this method was found to be nearly the same as that of the sin2ψ method. As an example of the application of the method to fatigue crack growth problems, the residual stress field near the fatigue crack tip was measured after the application of several cycles of overloads. The compressive residual stress became higher as the number of overload cycle increased. The higher compressive residual stress may be responsible for the greater amount of growth retardation of a fatigue crack due to increasing number of overload cycles.
