Identification of Model Parameter for the Simulation of SMA Structures Using Full Field Measurements

With the design of new devices with complex geometry and to take advantage of their large recoverable strains, shape memory alloys components (SMA) are increasingly subjected to multiaxial loadings. The development process of SMA devices requires the prediction of their thermomechanical response, where the calibration of the material parameters for the numerical model is an important step. In this work, the parameters of a phenomenological model are extracted from multiaxial and heterogeneous tests carried out on specimens with the same thermomechanical loading history. Finite element analysis enables the computation of numerical strain fields using a thermodynamical constitutive model for shape memory alloys previously implemented in a finite element code. The strain fields computed numerically are compared with experimental ones obtained by DIC to find the model parameters which best matches experimental measurements using a newly developed parallelized mixed genetic/gradient-based optimization algorithm. These numerical simulations are carried out in parallel in a supercomputer to reduce the time necessary to identify the set of identified parameters. The major features of this new algorithm is its ability to identify material parameters of the thermomechanical behavior of shape memory alloys from full-field measurements for various loading conditions (different temperatures, multiaxial behavior, heterogeneous test configurations). It is demonstrated that model parameters for the simulation of SMA structures are thus obtained based on a reduced number of heterogeneous tests at different temperatures.NSF International Institute of Multifunctional Materials for Energy Conversion (IIMEC), award #084108

Constitutive model for shape memory alloys including phase transformation, martensitic reorientation and twins accommodation

International audienceThis paper deals with the thermomechanical modeling of the macroscopic behavior of NiTi shape memory alloys (SMAs). A phenomenological 3D-model, based on thermodynamics of irreversible processes is presented. Three main physical mechanisms are considered: the martensitic transformation, the reorientation of martensite and the inelastic accommodation of twins in self-accommodated martensite. The description of such strain mechanisms allow an accurate analysis of SMA behavior under complex thermomechanical paths, especially when transformation occurs at low stress level. Moreover, some key characteristics such as tension–compression asymmetry and internal loops inside the major hysteresis loop are taken into account. Numerical simulations for various theromechanical loading paths are presented to illustrate the present model capability to capture the complex behavior of SMA

Numerical study of mean-field approach capabilities for shape memory alloys matrix composites description

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Numerical tool for Shape Memory Alloys structures simulations including twinning effects

According to the S3T-RoundRobin effort, this paper presents the main results obtained using the SMA model developed by Chemisky et al. [6], from the calibration to the prediction results. This model is based on thermodynamics of the irrevesible processes. Three internal variables are used to model the macroscopic behavior of SMAs. Parameters identification procedure requires only a limited set of experimental data. Comparison between modeling and experimental results are presented for the four data sets of this RoundRobin. Finite Element Analysis was performed to capture tension-torsion tests. Major discrepancies are related to strain localization effects and R-phase transformation which are not included in the present model

Roundrobin SMA modeling

This article reports on an ESF S3T EUROCORES sponsored networking activity called Roundrobin SMA modeling organized with the aim to compare capabilities of various thermomechanical models of shape memory alloys capable to simulate their functional responses for applications in smart engineering structures. Five sets of experimental data were measured in thermomechanical tests on thin NiTi filament in tension, torsion and combined tension/torsion. The data were provided to six teams developing advanced SMA models to perform appropriate simulations. Simulation results obtained by individual teams were compared with experimental results and presented on a dedicated Roundrobin SMA modeling website. The evaluation of the activity in terms of the assessment of the capability of individual models to deal with specific features of the experimentally measured SMA thermomechanical responses is provided in this article

Roundrobin SMA modeling

This article reports on an ESF S3T EUROCORES sponsored networking activity called Roundrobin SMA modeling organized with the aim to compare capabilities of various thermomechanical models of shape memory alloys capable to simulate their functional responses for applications in smart engineering structures. Five sets of experimental data were measured in thermomechanical tests on thin NiTi filament in tension, torsion and combined tension/torsion. The data were provided to six teams developing advanced SMA models to perform appropriate simulations. Simulation results obtained by individual teams were compared with experimental results and presented on a dedicated Roundrobin SMA modeling website. The evaluation of the activity in terms of the assessment of the capability of individual models to deal with specific features of the experimentally measured SMA thermomechanical responses is provided in this article