Constitutive modeling of superelastic shape memory alloy damping considering dynamic effects

Kaup, Andreas; Klinkel, Sven (Thesis advisor); Krommer, Michael (Thesis advisor); Altay, Okyay (Thesis advisor)

Aachen : RWTH Aachen University (2022, 2023)
Book, Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022


Increasing economical and technical requirements make the design of earthquake resistant civil engineering structures with traditional construction materials highly challenging. Shape memory alloys (SMA) are metallic smart materials with unique characteristics. Without any residual elongation, SMAs can recover their original shape after mechanical stress induced large deformations with even over 7~\% strain. This so-called superelastic behavior make SMAs an attractive alternative to the existing conventional damping devices, which show significant technical limitations. Conventional anti-seismic devices such as metallic steel dampers, which need to be replaced after each strong seismic excitation because of the non-recoverable plastic deformation, are representative examples. A broader application of the SMA based dampers require further research both on the numerical and experimental part. Until now, researchers identified inconsistent and partly different results regarding the strain rate and strain amplitude dependent hysteretic behavior and the resulting energy dissipation capacity of dynamically excited SMAs. The interaction of both the frequency effects and the strain amplitude together with the unique transient character of the earthquake loading are supposed to be the reasons for the inaccuracy of the existing macroscopic models. Shaking table tests are ideal to investigate the strain-rate and strain amplitude dependent material behavior. Furthermore, to investigate both the functionality and efficiency of superelastic SMA dampers incorporated in frame structures, real-time hybrid simulations are the method of choice for research. Thus, in this thesis, the seismic behavior of SMA dampers using RTHS is analyzed. Therefore the structure is partitioned into physical and numerical substructures. RTHS provides a full-scale experimental solution by simulating controlled structures numerically while testing dampers experimentally. As for RTHS numerically highly efficient material models are necessary to simulate the material behavior in real-time. Besides RTHS, also other real-time application in structural engineering, such as real-time data acquisition for structural health monitoring and control require computationally high efficient constitutive models. Semi-active vibration control SMA devices and digital twins are structural control and monitoring applications with a promising future, based on real-time problems. However, existing macroscopic material models struggle to simulate the strain-rate and strain amplitude dependent material behavior of superelastic SMA wires for dynamic excitations. In fact, in this thesis, existing constitutive models with the potential to perform in real-time are improved, by proposing modeling approaches to cover the experimentally observed material behavior under repeated loading conditions and transient earthquake loading effects regarding the stochastic nature of seismic loading.


  • Chair and Institute of Structural Analysis and Dynamics [311810]