Shape memory alloy

We are looking for a highly motivated candidate for a PhD position between École des Ponts ParisTech and University of Pavia, starting October 2024. The position is part of the EU-funded project MISCEA, an ambitious multidisciplinary Doctoral Training Network under the Horizon-Europe Marie Skłodowska-Curie Actions COFUND.

A PhD position or a Post-Doc position, depending on the candidate skills are available in the Department of Sciences and Methods fo Engineering at the University of Modena and Reggio Emilia, Italy. The research project is in the smart composite materials design. The candidate will have to design and optimize a composite structure with embedded SMA for morphing application. Candidates should have possibly a strong background in mechanics, finite elements simulations and smart materials.

A 3D constitutive model is proposed and verified with experimental data. Tension-torsion coupling effect and tension-compression asymmetry effect is investigate for tube shape memory alloy.

In this paper, a phenomenological constitutive
model based on microplane model is used to simulate tension, torsion and proportional tension-torsion on NiTi thin-walled tube. Validation of the
microplane model against experimental results in different loading conditions demonstrates
the capability of this approach.
This publication will benefit the numerical and experimental study on SMAs.

Normal
0

false
false
false

EN-US
X-NONE
AR-SA

Dear all,

I' m trying to make a model in VUMAT for shape memory alloy based on Lagoudas 's thermomechanical constitutive model. It seems that It's necessary an iteration to evaluate the thermoelastic prediction.

My questions are : is it possible to use an iterative loop in the VUMAT or it's better to avoid it??Could someone suggest me a different way so that I can avoid the iterative loop?

Many thanks,

Cece

With the increasing use of shape memory alloys in recent years, it is important to investigate the effect of cracks. Theoretically, the stress field near the crack tip is unbounded. Hence, a stress-induced transformation occurs, and the martensite phase is expected to appear in the neighborhood of the crack tip, from the very first loading step. In that case, the crack tip region is not governed by the far field stress, but rather by the crack tip stress field. This behavior implies transformation toughening or softening.

Smart materials have received much attention in recent years, especially due to their various applications in smart structures, medical devices, actuators, space and aeronautics. Among these
materials, shape memory alloys exhibit extremely large, inelastic, recoverable strains (of the order of 10%), resulting from transformation between austenitic and martensitic phases. This
transformation may be induced by a change, either in the applied stress, the temperature, or both.

Xi Wang, Yves Bellouard, Joost J. Vlassak

Published in Acta Materialia 53 (2005) p4955-4961.

Abstract — We present the results of a crystallization study on NiTi shape memory thin films in which amorphous films are annealed by a scanning laser. This technique has the advantage that shape memory properties can be spatially distributed as required by the application. A kinetics study shows that nucleation of the crystalline phase occurs homogenously in the films. Consequently, the laser annealing process produces polycrystalline films with a random crystallographic texture. The crystallized films have a uniform microstructure across the annealed areas. The material in the crystalline regions transforms reversibly to martensite on cooling from elevated temperature and stress measurements show that a significant recovery stress is achieved in the films upon transformation.