LAUSR

Nowadays small scale resistance spot welding is used frequently because of the requirements of miniaturization in industries. It is known that contact resistance is the most essential factor in heat generation process. In this study a new equation is provided to calculate the electrical contact resistance that does not require the number of contact points, the size, shape and distribution of them. To perform a simulation of the process, resistance spot welding is considered as an electrical-thermal-mechanical process in the finite element model. The simulation is done using a three dimensional model in COMSOL Multiphysics. The results of the simulation work are validated through performing experimental validation on Hastelloy X sheets. A new set-up is designed and constructed to study the effects of parameters in small scale resistance spot welding. Also, the relationships between mechanical properties and weld nugget dimensions and process parameters such as electrode force, welding current and welding time is evaluated. A DOE analysis is carried out to verify the significance of input factors on the nugget diameter, maximum load and nugget height. It was concluded that the nugget diameter increases with increasing time of current passing and decreases with increasing force. Also, increasing the current increases the nugget diameter. The maximum strength is obtained by applying maximum force, maximum time and minimum up to moderate currents. Optical metallography results demonstrated primary carbides (M6C) at the base metal and widmanstatten platelets at the weld area. It was found out that the maximum hardness occurs in the weld area.