Simulation of Shape Memory Alloy (SMA)-Bias Spring Actuation for Self-Shaping Architecture: Investigation of Parametric Sensitivity.

Hwang Yi

doi:10.3390/ma13112485

Abstract

Parametric complexity of the thermomechanical shape memory alloy (SMA) model is one of the major barriers to advanced application of the SMA actuation in adaptive architecture. This article seeks to provide architectural practitioners with decision-making information about SMA actuator design parameters. Simulation-based global sensitivity analysis of an SMA-bias spring actuation model reveals that the SMA spring index (a spring’s outer diameter divided by its wire diameter) and stiffness of the bias spring are significant factors in both displacement and force exertion. Among all parameters, maximum output stroke and force largely depend on the temperature range at which the SMA spring operates. These findings also indicate a trade-off between the spring diameter and wire thickness, demonstrating that the output stroke and force tend to counter one another. Appropriate preloading and choice of an optimal spring index should be considered for desirable SMA motion.

Highlights

Shape memory alloy (SMA) as a smart material has been the subject of intensive research in various areas, including robotics, micromechanical systems, the aerospace and automotive industries, civil structural engineering, and biomedical sciences [1,2,3,4]
Large index springs are advantageous to the output stroke if the actuator length is limited [28], implying that small spring diameters are likely prone to deflection, D is concealed in the parameter list
Note that the spring coefficient of the bias spring is critical to shape memory alloy (SMA) elongation

Summary

Introduction

Shape memory alloy (SMA) as a smart material has been the subject of intensive research in various areas, including robotics, micromechanical systems, the aerospace and automotive industries, civil structural engineering, and biomedical sciences [1,2,3,4]. Compared to conventional electromagnetic motor actuators, SMAs offer noiseless operation, design flexibility, and resistance to functional degradation from dust or humidity with compact system configurations. In recent years, such unique technical benefits of SMAs in actuation have attracted considerable attention regarding their utility in building design disciplines; for instance, self-shaping kinetic architecture or climate-adaptive building with automatic environmental responsiveness [7,8,9,10]. Many parameters related to sizing of SMA actuation are quite uncertain during the design stages of building projects, and a majority of existing SMA application approaches deal with SMA behaviors on smaller scales. It is necessary to provide building designers with concise information related to parametric choice in large-scale SMA actuator design so that they are better and more efficiently informed of the thermomechanical SMA properties and the potential performance of SMA-driven kinetic building

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