To investigate the weld growth mechanisms in resistance spot welding, a fully coupled numerical and experimental approach has been performed using the finite-element method. This numerical model dedicated to the resistance welding simulation is presented in the first part of this article. To take the contact conditions carefully into account, a finite-element formulation is detailed in the second part, where the experimental device used to measure the interface contact properties is also presented. An example is detailed to validate the approach presented in this article. The experimental shape evolution of the nugget is compared to numerical results.