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A numerical model combining the methods of enthalpy, effective-viscosity and volume-of-fluid is developed to simulate the metal transfer process in gas metal arc welding. The model describes not only the influence on droplet profile and transfer frequency of electromagnetic force, surface tension, and gravity, but it can also model the nonisothermal phenomena such as heat transfer and phase change. The model has been used to study the shape of the melting interface on the welding wire, the droplet oscillation at wire tip, the characteristics of relevant physical variables and their roles in metal transfer. We find that the taper formation in spray transfer is closely related to the heat input on the unmelted portion of the welding wire, and the taper formation affects the globular-spray transition by decelerating the transfer process. The formation of satellite drops during the metal transfer process is also considered. High-speed photography, laser-shadow imaging, and metallographic analysis validate the numerical model, and recommendations are made on the topics that require further consideration for a more accurate metal transfer model.

SUMMARYA worst-case vehicle evaluation methodology is presented in this paper. This evaluation method identifies worst-case excitation signals so that the vehicle performance under extreme conditions can be assessed. Two case study examples are presented to illustrate the design procedure and potential benefits of this method: the rollover and jackknifing of an articulated truck, and the evaluation of an active yaw control system. In both cases, the worst-case method was able to produce unstable results at very modest steering/braking levels.

This paper studies an intentional force increase during the process of resistance spot welding (RSW). Known for decades, the forging force as a way of influencing weld quality has rarely been applied in the automotive industry. There has been little research in this area. In this paper, the effects of varying forging force are investigated using both experimental and analytical approaches. Through the analysis of dynamic electrical resistance, the mechanism of the forging effects is explored. This study achieves a better understanding of forging force application and shows the benefits of the forging force on weld quality.

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