Neutron Diffraction Mapping (NDM) for Residual Stresses in Resistance Spot Welding (RSW)

Florea, R. S., Hubbard, C. R., Cady, B., Cornwell, P., Bammann, D., Marin, E., & Asle Zaeem, M. (2011). Neutron Diffraction Mapping (NDM) for Residual Stresses in Resistance Spot Welding (RSW). ONSUM 2011. Oak Ridge, TN: Oak Ridge National Laboratory.

Abstract

This work presents the stress measurements for resistance spot welding joints of 2 mm aluminum sheets by neutron diffraction technique. Residual strains were measured in three different directions denoted as in-plane longitudinal, in-plane transversal and normal . The welding process parameters were established to meet or exceed MIL-W-6858D specifications: approximately 5.7 mm weld nugget and 3.8 kN failure load by performing quasi-static tensile testing. The measurements were taken at a series of points on weld centerline, along lines either 1 mm below the plate top and 1 mm above its bottom. Stresses were captured on fusion zone, heat affected zone and base metal of the resistance spot welded joint. Neutron diffraction results show residual stresses in the weld are approximately 40% lower than yield strength of the parent material. The maximum variation in residual stresses is in the vertical position because of the electrode clamping forces and the high heat input which gave a non-uniform solidification pattern to the weld nugget