@Article{CoLeRu23, author = {Conti, Sergio and Lenz, Martin and Rumpf, Martin and Verh\"ulsdonk, Jan and Zwicknagl, Barbara}, title = {Geometry of Needle-Like Microstructures in Shape-Memory Alloys}, journal = {Shap. Mem. Superelasticity}, year = {2023}, doi = {10.1007/s40830-023-00442-0}, abstract = {Needle-like microstructures are often observed in shape memory alloys near macro-interfaces that separate regions with different laminate orientation. We study their shape with a two-dimensional model based on nonlinear elasticity, that contains an explicit parametrization of the needle profiles. Energy minimization leads to specific predictions for the geometry of needle-like domains. Our simulations are based on shape optimization of the needle interfaces, using a polyconvex energy density with cubic symmetry for the elastic problem, and a numerical implementation via finite elements on a dynamically changing grid.} }