Abstract

Friction Stir Welding (FSW) process development is very costly, and it is still experimental. A predictive model would optimize the weld by changing parameters and obtaining results that reflect the physical process. Friction is the primary adjustable parameter in FSW modeling. Currently, friction model selection is not physic-based. It is based on what is available and contributes to the best fit between the model and experimental data. The research objective is to characterize the interface tool/base material by studying the effect of tool friction coefficient and thermal properties. This is accomplished by changing welding parameters such as force, rpm, and temperature and studying the effects on dependent variables that contribute to the shear stress produced by friction. The study's findings challenge traditional friction concepts by revealing how the rapid engagement of a tool with the base material significantly reduces the impact of sliding friction. Instead, the observed friction primarily depends on the resistance of the shear layer to the tool's motion. This resistance, in turn, is chiefly influenced by the interface temperature, a factor strongly impacted by the thermal diffusivity of the tool material. Remarkably, thermal diffusivity holds the most influence (49.3%) on interface temperature. The interface of the tool material is characterized by a shear stress equation integrating pressure, RPM, thermal diffusivity, and interface temperature. Additionally, the investigation highlights the critical role of heat extraction, where materials with higher thermal diffusivity exhibit distinct outcomes: heightened torque, reduced surface temperature, minimized layer volumes, and shorter operation times.

Degree

College and Department

Ira A. Fulton College of Engineering; Manufacturing Engineering

Rights

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