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A magnetostrictive actuator with a hydraulic displacement amplification mechanism is designed to be used as a driver in active engine mounts. The dynamic response of the actuator is quantified in terms of the output displacement and the magnetostriction. Eddy current losses are modeled as a one-dimensional magnetic diffusion problem in cylindrical coordinates. The Jiles–Atherton model is used to describe the magnetization state of the material as a function of applied magnetic fields. Magnetostriction, which is modeled as a single-valued function of magnetization, provides an input to the mechanical model describing the system vibrations. Friction at the elastomeric seals is modeled using the LuGre (Lund–Grenoble) friction model for lubricated contacts. Results show that the model accurately describes the dynamic behavior of the actuator up to 500 Hz. An order analysis of the data and calculated responses shows that the model describes the fundamental and higher-order spectral components generated by the device.

P. EVANS and M.J. Dapino, “Efficient magnetic hysteresis model for field and stress application in magnetostrictive Galfenol,” Journal of Applied Physics, Vol. 107, 063906, 2010.

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Purpose – Ultrasonic additive manufacturing (UAM) is a rapid prototyping process through which multiple thin layers of material are sequentially ultrasonically welded together to form a finished part. While previous research into the peak temperatures experienced during UAM have been documented, a thorough examination of the heating and cooling curves has not been conducted to date.

Design/methodology/approach – For this study, UAM weldments made from aluminum 3003‐H18 tapes with embedded Type‐K thermocouples were examined. Finite element modeling was used to compare the theoretical thermal diffusion rates during heating to the observed heating patterns. A model was used to calculate the effective thermal diffusivity of the UAM build on cooling based on the observed cooling curves and curve fitting analysis.

Findings – Embedded thermocouple data revealed simultaneous temperature increases throughout all interfaces of the UAM build directly beneath the sonotrode. Modeling of the heating curves revealed a delay of at least 0.5 seconds should have existed if heating of lower interfaces was a result of thermal diffusion alone. As this is not the case, it was concluded that ultrasonic energy is absorbed and converted to heat at every interface beneath the sonotrode. The calculated thermal diffusivity of the build on cooling was less than 1 percent of the reported values of bulk aluminum, suggesting that voids and oxides along interfaces throughout the build may be inhibiting thermal diffusion through thermal contact resistance across the interface.

Originality/value – This work systematically analyzed the thermal profiles that develop during the UAM process. The simultaneous heating phenomenon presented here has not been documented by other research programs. The findings presented here will enable future researchers to develop more accurate models of the UAM process, potentially leading to improved UAM bond quality.

D.E. Schick, S.S. Babu, D. FOSTER, M.J. Dapino, M. Short, and J.C. Lippold, “Transient thermal response in ultrasonic additive manufacturing of aluminum 3003,” Rapid Prototyping Journal, Vol. 17, Issue 5, pp. 369-379, 2011.