The effect of heat input on residual stress distribution of steel welds measured by neutron diffraction

Purpose: of this paper is to investigate the effect of increase in the value of heat input due to change in the welding speed and its influence on residual stress distribution in steel weldments. Design/methodology/approach: The use of the neutron diffraction (ND) technique for residual stress measurements is described. Fully restrained, single-bead-on-plate specimens have been examined. Detailed measurements within a small gauge volume were taken 1.5 mm below the surface, across the sample. In addition, studies of macrostructure and hardness were conducted. Findings: Residual stresses in restrained welds and weld repairs are very complex. The heat input affects the value and distribution of residual stress in the specimen. This peak stress in all three samples occurred not at the toe, but in the middle of the weld bead, where the yield stress is higher. The transverse residual stresses of around half the maximum value of longitudinal stress have been observed. Research limitations/implications: Measurements of residual stress can be very expensive and time consuming. The ND technique is capable of non-destructive investigation in a relatively small gauge volume in depth of the material. However, a number of important issues still remain puzzling, including the uncertainties in the measurement, reliability and interpretation of the results, particularly in regards to the sampling volume and generally in the lack of an engineering standard procedure. The results may be used to calibrate finite element modelling of the welding process. Practical implications: The findings have important consequences with respect to design of welding procedures and fitness-for-purpose assessments. Originality/value: The authors have used ND assessment of residual stresses to follow in detail the changes due to heat input in a small gauge volume. This paper could be an interesting source of information for engineers and researchers who work with welded structures