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Friction stir welding (FSW) is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. The objective of this paper was to develop a numerical thermomechanical model for FSW of aluminum-copper alloy AA2219 and analyze heat generation during the welding process. The thermomechanical model has been developed utilizing ANSYS Ò APDL. The model was verified by comparing simulated temperature profile of three different weld schedules (i.e., different combinations of weld parameters in real weld situations) from simulation with experimental results. Furthermore, the verified model was used to analyze the effect of different weld parameters on heat generation. Among all the weld parameters, the effect of rotational speed on heat generation is the highest.

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The weight and the cost of a wind turbine are two important factors that make wind energy competitive with other energy sources. The weight of the rotor is typically 40–80% of the total weight of the system. Thus, lowering cost by reducing the weight of the blade is an important consideration. Another significant factor is the operational life of the machine. At present, a wind turbine’s life span is about 108 cycles or 20 years of continuous service. Innovative design solutions are needed in order to meet the criteria of improved stiffness, fatigue life, reliability, and efficiency. The directional property of an anisotropic composite material can be used to passively control wind turbine blade geometry in fluctuating wind speeds. Anisotropic materials show various levels of elastic coupling, based upon the ply angle in the layers. Structural behavior that exhibits both bending and twisting due to a pure bending load is known as twist-bend coupling. This type of behavior can be used for load reductions, particularly fatigue loads. The idea is to allow the blade to unload (reducing the speed) by allowing the wind induced bending moment to twist the blade. Increments in bending moment produce an increment in the twist that lowers the aerodynamically produced load. Higher blade stiffness can be achieved by full or partial replacement of glass fiber with carbon fiber. Carbon fibers are not used extensively on commercial wind turbine blades as they are more costly than glass fiber. The main objectives of this work are: (1) design a baseline model (made from glass fibers) of the wind turbine blade in accordance with published airfoil data; (2) conduct a finite element analysis of the blade and determine stresses, and strain within the blade; (3) develop a hybrid blade design by replacing the glass fibers with carbon fibers in the spar cap; and (4) validate the feasibility of implementing bend-twist coupling in the wind turbine blade by studying stresses, and strain behavior. By giving different orientation in the carbon fiber and changing the fiber layer, different designs are analyzed with regard to the above listed criteria.