Residual Stresses And Fatigue Of Surface Treated Welded Specimens

Author:  Bellow, Wahab, Faulkner
Source:  Adv. in Surf. Treat. Tech--Appl--Eff., Vol. 2
Doc ID:  1986043
Year of Publication:  1986
Abstract:  
An experimental program was undertaken to evaluate the effect of induced compressive stresses due to various peening and thermal treatments on the fatigue life of a butt welded medium strength steel (0.005Nb). Residual stresses were measured using X-ray diffraction and ther results were compared with hardness values taken at the surface and through the thickness of the specimens. It was found that of all post weld treatments studied the stress peened specimens gave the most improvement in fatigue strength over that of the as-welded condition and approached 82% of the fatigue strength of the base metal at a fatigue life of 2 x 10 exp 6 cycles. On the other hand annealing only showed an improvement of 14% over that of the as-welded condition. It was found that a good linear correlation existed between the induced residual stresses at the toe of the weld and the fatigue strength evaluated at 2 x 10 exp 6 cycles. However, for residual stresses of less than 130MPa very little improvement in fatigue strength was evident. Surface residual stresses were compared with Almen strip readings and the depth of work hardening. It was found that the Almen strip readings did not give as consistent an indication of work hardening as did measurement of the residual stresses. Descriptors: High strength low alloy steels-- Welding; Butt welds-- Mechanical properties; Residual stress-- Deformation effects; Fatigue strength-- Deformation effects; Surface hardening; Shot peening