1,721,165 research outputs found
Numerical Experiments for Thermally-induced Bending of Nematic Elastomers with Hybrid Alignment (HNEs)
No full textThe nematic elastomers with hybrid alignment (HNEs) exhibit large anisotropic and non homogeneous volume changes, which can in- duce noticeable changes in their configuration. Here, we deal with LCEs having hybrid align- ment (HNEs), that is, fabricated with a given non-homogeneous nematic orientation. For such a materials, permanent distortions induced by deswelling can be compensated by those resulting from cooling below TN ; it results the possibility of producing temperature-driven actuators
Characterization of the macroscopic response of magnetostrictive materials via microstructural analysis
No full textThis paper discusses recent progress on the prediction of magnetization and magnetostriction curves for magnetoelastic solids. Our approach hinges on the characterization of energetically optimal microscopic domain patterns based on the use of Young measures and H-measures
Hysteresis and imperfection sensitivity in small ferromagnetic particles
No full textThe classical results of Stoner and Wohlfarth for the prediction of hysteresis loops in small ferromagnetic particles are extended to specimens of non-ellipsoidal shape, and shown to be a consequence of micromagnetics. The insensitivity to surface roughness is proposed as a possible explanation of the high coercivity behavior of small particles
Coarse-grained models of materials with non-convex free-energies: two case studies
No full textBridging across length scales is one of the fundamental challenges in the computational modelling of material systems whose mechanical response is driven by rough energy landscapes. The typical feature of such systems is that of exhibiting fine scale microstructures. Two case studies, namely, nematic elastomers and ferromagnetic shape memory alloys, are presented to illustrate the use of modern techniques from (non-convex) calculus of variations in developing coarse-grained models of microstructure-driven material response
Magnetostrictive solids: macroscopic response and microstructure evolution under applied magnetic fields and loads
No full textThe macroscopic behavior of magnetostrictive materials results from domain evolutions occurring at a microscopic scale. We show how to compute virgin magnetization and magnetostriction curves by appraising the behavior of the underlying microstructures. Our method hinges on an averaging device (Young measures), which allows us to pass from the microscopic to the macroscopic scale. We take into account the kinematical constraints on the accommodation of elastic effects, and we highlight the role of material symmetry in the selection of energetically optimal microstructures. Finally, we analyze the influence of applied surface tractions on the magnetoelastic response of a magnetostrictive specimen
Energetics of fine domain structures
No full textIn the last two decades, numerous new mathematical tools have emerged in the literature on Calculus of Variations for the analysis of minimization problems involving non-convex free-energies. These advances have shed some new light on the behavior of a variety of physical systems exhibiting domain structures, and on their response to external actions (forces, electromagnetic fields, etc.). Examples range from ferroelastic solids, and, in particular, shape memory alloys, to ferromagnetic and ferroelectric materials, and, in particular, solids with strong electro- or magneto-elastic coupling. In this paper, some of these mathematical techniques are applied to analyze experimental and theoretical observations of striped domain patterns in liquid crystalline polymers
Magnetization and magnetostriction curves from micromagnetics
No full textThe macroscopic behavior of magnetostrictive materials results from domain evolutions, often occurring at a microscopic scale. It is shown how to compute magnetization and magnetostriction curves by appraising the behavior of the underlying microstructures. The method hinges on an averaging device (Young measures), which allows one to pass from the microscopic to the macroscopic scale. The kinematical constraints on the accommodation of elastic effects are taken into account, and the role of material symmetry in the selection of energetically optimal microstructures is highlighted. Moreover, the effect of magnetoelastic coupling on the computation of magnetization curves is discussed
- …
