Experimental study on the effect of misfit and mismatch of ship plating welds

Abstract

Misfits and mismatches in the welding of ship hull plating may affect survivability after explosions, accidents, or other extreme external forces. Experiments, Slip Line Theory (SLT), and Finite Element Analysis (FEA) help to explain the necking, deformation, and mechanisms of fracture of misfit welded plating. The effect of misfits or offsets on both overmatched and evenmatched welds under tension are studied. The tension creates a moment about the offset weld causing the weld to rotate and the material around the weld to thin down, but strain hardening reduces the thinning that occurs and shifts deformation elsewhere away from the weld. EH-36, a commercial medium strength steel now being used in Navy surface combatants, was tested. The overmatched EH-36 misfit welds experienced rotation, minor thinning near the weld, and deformation elsewhere as predicted. AL6XN, a new stainless steel with evenmatched welds, gave nearly the same results as the EH-36. There was a 3% reduction in maximum applied force per area for the 30% offset case, and an increase in the amount of thinning near the weld.