Design of a Morphing Skin with Shape Memory Alloy Based on Equivalent Thermal Stress Approach

Abstract

Shape memory alloy (SMA) is one of the potential driving devices for morphing aircraft due to its advantages of pseudoelasticity, superelasticity, and shape memory effect. Precise and fast analysis of SMA has simultaneously become a key requirement for industrial applications. In this study, a user-defined material subroutine (UMAT) was implemented and successfully applied in a three-dimensional numerical simulation in ABAQUS based on the extended Boyd–Lagoudas model. In addition to the conventional detwinned martensite (Md) and austenite (A), twinned martensite (Mt) was also considered to model the practical transformation accurately. Then, the equivalent thermal strain approach was adopted to simplify the simulation complexity with UMAT. By resetting the thermal expansion coefficient, the thermal strain equivalent to the original phase transformation strain was generated. The approach was validated in two cases, showing consistent results with the extended Boyd–Lagoudas model and reduction in time consumption by 89.1%. Lastly, an active morphing skin integrating the single-range SMA and a stainless-steel plate was designed to realize two-way morphing. The calculated arc height variation of the skin was 3.74 mm with a relative error of 1.84% compared to the experimental result of 3.81 mm. The coupled use of UMAT and the equivalent thermal stress approach helped to reduce the challenge in modeling SMA.

Editorial for the Special Issue on Structural Analyses and Designs for Flexible/Stretchable Electronics

“…Twelve articles are by authors from China and one paper each was contributed by authors from Germany, Italy, Poland, and Russia. A comprehensive range of aspects related to the structural analyses, designs, and fabrication of flexible/stretchable devices and smart materials are covered, including mechanical analyses of flexible/stretchable devices [ 1 , 2 , 3 , 4 ], thermal analyses of flexible heaters [ 5 , 6 , 7 , 8 , 9 ], mechanical–conductive analyses of island-type structures in flexible/stretchable devices [ 10 ], thermo-mechanical analyses and designs of morphing aircraft structures [ 11 ], adhesive bonding technology for flexible substrates [ 12 ], electrohydrodynamic jet printing technology for flexible substrates [ 13 ], process parameters’ influence on the resistance of 3D-printed electrically conductive structures [ 14 ], and recent advances in flexible radio frequency microelectromechanical systems (RE MEMS) [ 15 ] and triboelectric nanogenerators (TENGs) [ 16 ].…”

“…In addition to structural analyses of flexible/stretchable electronics, several design theories and fabrication technologies are also reported in this Special Issue. Zhang et al [ 11 ] implemented the UMAT in ABAQUS to realize the novel design of a morphing skin with a shape memory alloy based on an equivalent thermal stress approach and investigated the corresponding experiments, with consistent counterpart results. Saleh et al [ 12 ] studied the isotropic conductive adhesive and the solder and lifetime characterization of an assembly of surface-mounted devices on flexible substrates and summarized the better adhesive surfaces for future structural designs.…”