Shape Memory Alloy Film Damping for Smart Miniature Systems

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This project investigates, numerically describes and validates novel shape memory alloy (SMA) film damper devices using the dissipative mechanisms of either the superelastic effect (SE) or thermal shape memory effect (SME). This will enable a new generation of smart miniature damper systems for portable or mobile applications combining noise- and jerk-free operation as well as additional sensing functionality due to a strong coupling of thermal, mechanical and electrical properties. SMA materials and devices exhibit nonlinear stress-strain response and hysteresis due to a first order phase transformation allowing the engineering and control of dissipative processes at large stress and strain levels up to 500 MPa and 5%, respectively. Owing to the large surface-to-volume ratio of SMA films rapid heat transfer leads to time constants in the millisecond regime.Starting materials are TiNi-based films showing optimized SE or SME properties. The dissipative mechanisms during load cycling of corresponding test structures are described by time-resolved finite element simulations using a thermodynamics-based phase-field model that takes into account the evolution of phase transformation, strain changes and heat flows. Several generations of SMA film damper systems will be developed and evaluated making use of passive damping due to SE, active damping due to SME as well as combinations thereof. Strategies of model order reduction will be developed to reduce simulation complexity. Lumped element models will be generated for model integration at the system level. A miniature camera module will be developed as a demonstrator to investigate the effect of SMA film damping and of suitable control strategies on the overall system dynamics. Additional functionalities including intrinsic temperature and position sensing will be investigated.