28 March 2012 Stress-induced tuning of ultrasonic additive manufacturing Al-NiTi composites
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This paper addresses the development of active metal-matrix composites manufactured by Ultrasonic Additive Manufacturing (UAM), an emerging manufacturing process that allows the embedding of materials into seemingly solid metal components. In the UAM process, successive layers of metal tapes are ultrasonically bonded together at low temperatures to form a metal-matrix. Being a low-temperature process, UAM offers unprecedented opportunities to create metal components with embedded thermally-sensitive materials, such as shape memory alloys. In this study UAM is used to create composites with aluminum matrices and embedded NiTi ribbons. These composites exhibit tunability of both the coefficient of thermal expansion and natural frequencies. These effects are due to the phase-dependent modulus and transformation stresses developed by the prestrained NiTi phase. Since the embedded NiTi ribbons are constrained by the matrix, thermally-induced transformation from detwinned martensite to austenite will be accompanied by the generation of transformation stresses. The effect of transformation stress and changing phase of NiTi on thermally-induced strain is observed and modeled by combining strain matching algorithms with thermodynamic-based constitutive models. The composite model accurately describes effects due to changing NiTi modulus and strain recovery due to initial stress-induced martensitic volume fractions including a 200 με contraction with increasing temperature. The observed dynamic behaviors include up to a 16.6% increase in natural frequency at 100°C as compared to room temperature tests. No substantial increase in damping ratio was observed relative to solid aluminum.
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Ryan Hahnlen, Ryan Hahnlen, Marcelo J. Dapino, Marcelo J. Dapino, } "Stress-induced tuning of ultrasonic additive manufacturing Al-NiTi composites", Proc. SPIE 8342, Behavior and Mechanics of Multifunctional Materials and Composites 2012, 83421J (28 March 2012); doi: 10.1117/12.915582; https://doi.org/10.1117/12.915582

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