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This paper reports on the experimental study of carbide and polycrystalline diamond (PCD) drills used for drilling composite/titanium stacks. Materials systems used in this study were multi-directional carbon fiber in an epoxy matrix and titanium 6Al-4V. The drill materials included tungsten carbide (WC; 9%Co ultra fine grain) and polycrystalline diamond (PCD; bimodal grade). Torque and thrust force were measured during the drilling experiments. Tool wear of both drills was periodically examined during the drilling tests using various microscopic techniques such as optical and Scanning Electron Microscope (SEM). Effect of tool materials and process condition on hole quality parameters such as hole diameter, surface roughness, and titanium burrs, were examined. Dissimilar mechanical and thermal properties of the stacks affected the tool life and resulted in the decreased hole quality for both cutting tool materials, although to a differing degree.

In the automotive industry, resistance spot welding (RSW), or spot welding, has been and continues to be an important process in body structure assembly. The optimization of the number, location, and quality of spot welds is a major economic consideration. In order to improve fatigue strength of low carbon steel RSWs, a StressWave cold working process has been recently adapted to RSWs. The cold working process generates uniform and consistent large zones of compressive residual stresses in resistance spot-welded low carbon steel structures using a specially designed indentation device. The effect of the StressWave cold working process parameters on the fatigue properties of the RSWed specimens is investigated. Comparisons of the fatigue strength and fractography between the as-resistance spot-welded specimens and the StressWave cold worked resistance spot-weld specimens are made in this investigation.