Welding is the primary joining process used in the construction and repair of railroad tank cars. Since recent federal regulations have emphasized the need for fatigue life analyses, and since most fatigue cracks and fractures in tank car structures are initiated in the vicinity of welds, there is a need to quantify the effect of tank car weld residual stresses on crack propagation and fracture. Thus, for the first time, the enclosed work reports neutron diffraction results for all six components of the three-dimensional residual stress field on a transverse weld cross section in a 5/8-in. (16.3-mm) thick, TC128-B steel widely used in the construction of pressurized railroad tank cars. Results for a nonheat- treated specimen indicate that (a) the residual effective stress ranges from 36 ksi (250 MPa) to 64 ksi (450 MPa) in the overmatched weld region, (b) the longitudinal residual stress approaches 120% of the uniaxial yield stress in the base material, and (c) the residual shear stresses are of the same order as the smaller principal residual stresses in the weld region.

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