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Highlight Lecture

Modeling of dissipative processes during dynamic loading of shape memory alloys

Wednesday (26.09.2018)
11:45 - 12:00 S1/01 - A4
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Shape memory alloys (SMAs) are used as efficient vibration dampers in structural applications due to the large deformation and dissipation capabilities. On the microstructural level the damping capacity relies either on the highly reversible motion of twin boundaries or on a first order martensitic transition (MT), similar to deformation twinning, associated with a stress-strain hysteresis and softening of the material.

We develop an effective model at the micrometer scale that combines a statistical mechanics approach for the MT kinetics with a phase-field approach including the effect of (coarse grained) martensite-austenite interfaces. The model captures local strain effects and thermomechanical coupling in polycrystalline thin film samples. The strongly non-linear response on stress as a driving force of the MT and the nucleation of Lüders bands under elastodynamic conditions is well described. For the parametrization a data-driven approach is applied that includes an analysis of macro scale experiments of stationary and transient mechanical response. Also, data on material heterogeneity is incorporated, which can be related to the grain scale.

Simulations of oscillating mass-SMA systems are conducted for conditions of impact and harmonic forcing, and are compared to experiments with NiTiCu-based SMA samples and micro-damping devices. The possible damping performance of the material under optimized operation conditions is assessed for the cases of pseudoelasticity (passive recentering motion) and quasiplastic deformation (actively controlled shape memory effect).

Speaker:
Dr. Frank Wendler
Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Additional Authors:
  • Shahabeddin Ahmadi
    Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
  • Kiran Jacob
    Karlsruhe Institute of Technology (KIT)
  • Prof. Dr. Manfred Kohl
    Karlsruhe Institute of Technology (KIT)