O. A. Jammal

Bio: O. A. Jammal is an academic researcher. The author has contributed to research in topics: Spot welding. The author has an hindex of 1, co-authored 1 publications receiving 89 citations.

Modeling of resistance spot weld nugget growth

Abstract: The weld nugget in resistance spot welding of Type 347 stainless steel was found, using f inite element methods, to initiate in a ring shape at a distance from the electrode center. The ring-like weld nugget expands inward and outward during the welding cycles. The welding current, electrode pressure and hold time affected the thermomechanical interactions of the welding process and changed the f inal nugget geometry. Also, when spot welding workpieces of unequal thicknesses, it was found that the weld nugget formed mostly in the thicker workpiece than in the thinner workpiece, and when spot welding dissimilar materials, the weld nugget formed more in the workpiece of lower thermal conductivity or higher electrical resistivity.

Numerical Simulation of Resistance Spot Welding Process

Abstract: This paper develops a model to predict the nugget development during resistance spot welding (RSW) of Al-alloys. The model employs a coupled thermal-electrical-mechanical analysis and accounts for phase change and convective transport in the weld pool. The contact area and the pressure distribution are determined from a coupled thermal ? mechanical model. The model calculates time varying interface pressure. The knowledge of interface pressure allows for accurate prediction of interfacial heat generation. Temperature-dependent thermal-electrical-mechanical properties are used. The predicted nugget shape and size agree well with experimental data. The proposed model can be applied to predict the effects of the welding parameters and the electrode shapes on the nugget development.

Analysis of aluminum resistance spot welding processes using coupled finite element procedures

Abstract: A comprehensive analysis procedure has been developed to perform the incrementally coupled thermal-electrical-mechanical analysis to simulate the resistance spot welding process of aluminum alloys. Because aluminum has high thermal conductivity, low melting temperature and low yield strength, deformation resulting from resistance spot welding is expected to be more severe than for steel. Compared with most of the published work in this area, this paper takes into account the incremental changes in sheet-deformed shape, contact area and current density profile as well as large deformation effects. The present analysis procedures consider electrical contact resistivities to be not only functions of contact temperature but also functions of pressure. Joule heating at the contact surfaces is computed using an equivalent surface heat generation concept. This new procedure is suitable for analyzing many important parameters such as contact area changes, electrode movement and dynamic resistance, as well as other factors that contribute to weld quality such as weld size, weld indentation, sheet separation and weld residual stresses. It can also be used to study nugget development and analyze the mechanisms of electrode wear and weld cracking.