Comparing the dynamic response of bead-on-plate and butt-welded plates

Abstract

Some studies have been developed to demonstrate that welded plates have their natural frequencies reduced when comparing them to non-welded similar plates, which is caused by welding residual stress. This phenomenon can be used to develop a new welding residual stress detection method. This new method, analyzing the plate vibrational responses, would have the advantage of being nondestructive, when comparing to hole drilling, and simpler and cheaper than X-ray diffraction, ultrasound and neutron diffraction methods. Therefore, in the search of this new technique, more research is being developed and more progress is still required. Some experimental work in the field has used bead-on-plate weldments for data analysis. However, this work demonstrates that bead-on-plate weldments do not present the same vibrational responses due to welding residual stress than butt-welded plates. This experimental work compares the vibrational responses of two identical plates welded by two different manners: bead-on-plate and butt-welded. Two stainless steel AISI 316L plates, with 302 × 150.5 × 6.30 mm, were tested. First, the entire plates had their natural frequencies measured, using a laser vibrometer. Then, one plate was Gas Tungsten Arc welded bead-on-plate on its center. The other plate was wire Electrical Discharge Machining cut in its center and then butt-welded. There was no material addition, in order to avoid additional mass interference in the natural frequencies values. Finally, the natural frequencies were measured again and the variations were calculated for the first six vibrational modes. Even though it was employed the same heat inputs and welding parameters in both welds, it is shown that the butt weld had higher modal variations than the bead-on-plate. The higher modal variations in the butt-welded plate indicate that butt weld induced higher welding residual stresses in the plates than bead-on-plate. Therefore, this work demonstrates that researchers willing to advance in the studies about the new welding residual stress method using vibrational responses should be attentive to this disparity.