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J. Eng. Mater. Technol.. 2015;137(4):041001-041001-11. doi:10.1115/1.4030480.

Friction stir welding (FSW) technique has been successfully applied to butt joining of aluminum alloy 6061-T6 to one type of advanced high strength steel (AHSS), transformation induced plasticity (TRIP) 780/800 with the highest weld strength reaching 85% of the base aluminum alloy. Mechanical welding forces and temperature were measured under various sets of process parameters and their relationships were investigated, which also helped explain the observed macrostructure of the weld cross section. Compared with FSW of similar aluminum alloys, only one peak of axial force occurred during the plunge stage. Three failure modes were identified during tensile tests of weld specimens, which were further analyzed based on the microstructure of joint cross sections. Intermetallic compound (IMC) layer with appropriate thickness and morphology was shown to be beneficial for enhancing the strength of Al–Fe interface.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol.. 2015;137(4):041002-041002-8. doi:10.1115/1.4030481.

Fiber-reinforced polymer (FRP) composites used in the construction of composite-based civil and military marine crafts are often exposed to aggressive elements that include ultraviolet radiation, moisture, and cyclic loadings. With time, these elements can individually and more so cooperatively degrade the mechanical properties and structural integrity of FRP composites. To assist in increasing the long-term reliability of composite marine crafts, this work experimentally investigates the cooperative damaging effects of ultraviolet (UV), moisture, and cyclic loading on the structural integrity of carbon fiber reinforced vinyl-ester marine composite. Results demonstrate that UV and moisture can synergistically interact with fatigue damage mechanisms and accelerate fatigue damage accumulation. For the considered composite, damage and S–N curve models with minimal fitting constants are proposed. The new models are derived by adapting well-known cumulative fatigue damage models to account for the ability of UV and moisture to accelerate fatigue damaging effects.

Commentary by Dr. Valentin Fuster

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