School of Mechanical Engineering Ehud Ingram
School of Mechanical Engineering Seminar
Wednesday, Novemer 21, 2018 at 14.00
Wolfson Building of Mechanical Engineering, Room 206
THE EFFECT OF VIBRATION DURING WELDING ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STRUCTURAL STEEL WELDS
Ehud Ingram
M.Sc. student of Prof. Noam Eliaz
Co-guidance of Dr. Oz Golan from Afeka - Tel-Aviv Academic College of Engineering
Improving the mechanical properties of weldments and reducing weld-induced residual stress has always been a desired goal for the industry. Vibratory welding, in which the part/structure is vibrated during welding, is one of the methods explored for achieving these goals. In industrial applications, for large structures of tens or hundreds of kilograms, fixing an eccentric motor to the structure and inducing excitation near resonant frequencies is the only feasible way to produce significant vibrational translations of the weld joints. Although the subject of vibratory welding has been explored by several researchers, results are inconclusive, and a “recipe” for producing a favorable weld does not yet exist.
In this study, the complexities of structural vibration on the welded joint as part of a vibrating structure were addressed. Local Vibrational Effects (LVE), i.e. rigid body motion of the weld, and Global Vibrational Effects (GVE), namely strains induced on the weld area by adjacent vibrating structure-members, were evaluated. Sample plates of EN10025 S235 mild steel and ASTM A516 Gr.70 pressure vessel steel were welded using Manual Gas Metal Arc Welding (GMAW) in an experimental setup that ensures only LVE. Welding was performed in a single pass, thus eliminating thermal effects of multi-pass welds. Welding was performed at three frequency/amplitude combinations: 12.8 Hz / 0.3 mm, 58.4 Hz / 0.25 mm, and 60 Hz /0.8 mm. The direction of vibration was normal-to-plate (up/down). After welding, mechanical and microstructural/metallurgical characterization was performed on the weld-pool and heat-affected zone (HAZ) using Vickers microhardness tests, tensile tests combined with digital image correlation (DIC), optical microscopy, and Scanning Electron Microscope (SEM). The results were then compared to those of the non-vibrated samples.
It was found that LVE does not promote any distinct difference in weld properties, at least within the vibrational regimes studied. Yet, in industrial applications vibratory welding can promote residual stress relief due to GVE of structural response in the process.
