Computational modeling of microstructure

Many materials such as martensitic or ferromagnetic crystals are observed to be in metastable states exhibiting a fine-scale, structured spatial oscillation called microstructure; and hysteresis is observed as the temperature, boundary forces, or external magnetic field changes. We have developed a numerical analysis of microstructure and used this theory to construct numerical methods that have been used to compute approximations to the deformation of crystals with microstructure

A Constrained Sequential-Lamination Algorithm for the Simulation of Sub-Grid Microstructure in Martensitic Materials

We present a practical algorithm for partially relaxing multiwell energy densities such as pertain to materials undergoing martensitic phase transitions. The algorithm is based on sequential lamination, but the evolution of the microstructure during a deformation process is required to satisfy a continuity constraint, in the sense that the new microstructure should be reachable from the preceding one by a combination of branching and pruning operations. All microstructures generated by the algorithm are in static and configurational equilibrium. Owing to the continuity constrained imposed upon the microstructural evolution, the predicted material behavior may be path-dependent and exhibit hysteresis. In cases in which there is a strict separation of micro and macrostructural lengthscales, the proposed relaxation algorithm may effectively be integrated into macroscopic finite-element calculations at the subgrid level. We demonstrate this aspect of the algorithm by means of a numerical example concerned with the indentation of an Cu-Al-Ni shape memory alloy by a spherical indenter.Comment: 27 pages with 9 figures. To appear in: Computer Methods in Applied Mechanics and Engineering. New version incorporates minor revisions from revie

Variational model of martensitic thin films and its numerical treatment

Following the derivation of the energy functional of martensitic thin films by Bhattacharya and James (1999) we propose a numerical approach to the relaxation theory of thin films. It is based on the approximation of the corresponding relaxed problem by a first-order laminate. Finally, computational experiments are shown

On the numerical modeling of deformations of pressurized martensitic thin films

We propose, analyze, and compare several numerical methods for the computation of the deformation of a pressurized martensitic thin film. Numerical results have been obtained for the hysteresis of the deformation as the film transforms reversibly from austenite to martensite

Computational Multiscale Methods

Computational Multiscale Methods play an important role in many modern computer simulations in material sciences with different time scales and different scales in space. Besides various computational challenges, the meeting brought together various applications from many disciplines and scientists from various scientific communities

Modelling of microstructure and its evolution in shape-memory-alloy single-crystals, in particular in CuAlNi

A continuum-mechanical description of the stored energy in shape-memory alloys is presented, with its multi-well character giving rise to a microstructure described, with a certain approximation, by special gradient Young measures. A rate-independent phenomenological dissipation is then considered to model a hysteretic response. Isothermal simulations with CuAlNi single crystal are presented