A Nonlinear Phase Transition Dynamic Model for Shape Memory Alloys Based Deep Sea Actuators

Abstract

A constitutive relation for shape memory alloys (SMAs) that is simple, accurate, and effective is the basis for deep-sea intelligent actuators used in marine engineering applications. The existing kinetic models of phase transition all have common drawbacks, such as sharp change at the turning point of the phase transition, constant phase transition rate, and many variable parameters. In this study, the one-dimensional thermodynamic constitutive equation for SMAs is extended based on the thermodynamic framework of the Boyd–Lagoudas constitutive model. In addition, the traditional phase transition function is replaced by an improved logistic nonlinear function in order to construct the relation for the macroscopic variable-speed phase transition that constitutes deep-sea actuator driving wires. The logistic model is compared to other models and verified by the numerical fitting results of the traditional constitutive model and the experimental data for two scenarios: (1) constant load and (2) constant temperature. The results show that the improved constitutive model has more advantages and better adaptability than the traditional models. Consequently, it can accurately describe the slow and gradual phase transitions in the initial and final regions of the phase transition with fewer variable parameters and has the ability to flexibly adjust the rate of change of the phase transition rate. These results provide important theoretical support for the design of SMA deep-sea actuators used in marine engineering applications.

Interface stress transfer model and modulus parameter equivalence method for composite materials embedded with tensile pre-strain shape memory alloy fibers

“…The macroscopic effective modulus of SMA composite materials depends on the fiber, matrix, and interfacial phase stress-strain relationship as well as the interfacial phase parameter properties in Eqs ( 14) and (15). Based on the homogenization equivalent method in this chapter and the stress expressions from Eqs (28) to (32), the macroscopic effective elastic modulus of SMAC can be obtained as follows:…”

“…In the past 30 years, scholars from various countries have constructed different types of intrinsic structure relationships for SMA materials from different perspectives, including fine-scale thermodynamic models, fine-scale mechanical models, and macroscopic image-only models [23][24][25][26]. Among them, the macroscopic image-only theoretical models based on thermodynamics and phase transition dynamics are more maturely studied [27][28][29]. Typical image-only intrinsic models include the Tanaka model, the Liang-Rogers model, and the Brinson model, among which the Tanaka and Liang-Rogers models cannot effectively describe the martensitic selective orientation process of SMAs [30].…”