Analysis of driving forces of 3D knitted shape memory textile actuators using scale-up finite element method

Abstract

The shape memory textile actuator uses a shape memory alloy that changes its crystal structure according to temperature and then returns to its initial shape, which is suitable for wearable applications that value wearing and portability. The shape memory effect of returning to the initial shape and the complex fabric structure influence each other, and accordingly, various drives have been measured in many studies. Therefore, in this study, the driving force, which is the most important physical property of the shape memory textile actuator, was analyzed through a scale-up finite element analysis. In the wire scale, a shape memory alloy wire was obtained for an analysis of the mechanical and thermal properties through tensile tests and DSC, and in the unit cell scale, a 3D knit structure was modeled using the Texgen and Weftknit programs. Finally, a supercell of size 5 × 5 was subjected to external deformation by displacement and heating conditions using disposition through the ANSYS program. The driving force was measured through microanalysis. Subsequently, the driving force of the manufactured shape memory textile actuator was compared and analyzed to determine the suitability of this method. Furthermore, the direction of subsequent studies was mapped based on the analysis presented on the differences in the maximum driving force and error rate.

Mapping actuating performance of knitted shape memory alloys and proposing design guidelines for assistive wearable applications

“…In previous studies, various actuation characteristics of knitted SMA modules have been analyzed. 6,12,17,20 However, we present the possibility of developing wearable products with high usability by analyzing the actuation performance of the knitted SMA for application to the human body using a multidimensional method, which differs from previously adopted approaches. The human body encompasses a diverse range of joints, enabling multiple movements such as bending, unfolding, abduction, adduction, and rotation.…”

“…15,16 Additionally, the actuation force of the knitted SMA was simulated through finite element analysis, proposing a high predictive power for the force compared with that of manufactured SMA knitted modules. 17 As such, the knitted SMA can be applied to wearable products because it has a contraction force of at least 40%, high energy density, and improved mechanical performance compared to the original (non-knitted) SMA wire, while exhibiting the unique flexible characteristics of the knitted fabric. 6,18…”

“…15,16 Additionally, the actuation force of the knitted SMA was simulated through finite element analysis, proposing a high predictive power for the force compared with that of manufactured SMA knitted modules. 17 As such, the knitted SMA can be applied to wearable products because it has a contraction force of at least 40%, high energy density, and improved mechanical performance compared to the original (non-knitted) SMA wire, while exhibiting the unique flexible characteristics of the knitted fabric. 6,18 While the above-mentioned studies have mostly contributed to the functional improvement of knitted SMA actuators themselves, some have tried to understand humandevice interactions with a consideration of the actuators' mechanical behaviors as well as the wearer's anthropometric information.…”

Research on elasticity behavior of Ni-Ti shape memory alloys using the reproducing kernel particle method

“…Sattari et al 20 considered the thermodynamic behavior of the SMAs in sliding wear and completed wear analysis of the SMAs under different temperatures and loads. Kim and Kim 21 analyzed the driving force of the physical properties of shape memory textile actuator by utilizing a scaled-up FEM. Zamani Alavije and Botshekanan Dehkordi 22 used the FEM to study the superelastic bending problem of the SMAs beams under the coupling effect of material nonlinearity and geometric nonlinearity.…”

Shape Memory Materials and its Use in the Textile Industry

“…The study shows that this method achieves higher temperatures with less power and improves heating stability, making SMAs more viable for wearable actuators. [8].…”