Abstract
A large area of X-ray irradiation causes some errors in measuring the residual stress of the curved surface by using sin2ψ method. To evaluate the true stress of the cylindrical surface, the relation between the errors of measured residual stress and sizes of X-ray irradiated areas was investigated experimentally and analytically. In the experiment masking tapes on the cylinder of tool steel were used to vary the size of the irradiated area. Bragg's X-ray diffractions in the irradiated regions of the cylinder were simulated in the analysis and the residual stresses were calculated according to sin2ψ method. These results show that (1) the magnitude of measured circumferential residual stress σ is smaller than true stress σω, (2) the ratio between two stresses σ/σω and the difference in those stresses ξ are represented by the following approximate relations σ/σω=Mcos{1.92(ζ/ρ)}, ξ=σ[M-1sec{1.92(ζ/ρ)}-1], where M≈1.81(t/ρ)+1, the X-ray irradiated area 2ζ, the diameter of the cylinder 2ρ, and the thickness of the masking tape t, and (3) the magnitude of the measured axial residual stress is hardly affected by the X-ray irradiated area or by the diameter of the cylinder.
