MECHANICAL BEHAVIOR OF SHAPE MEMORY ALLOY COMPOSITES UNDER DYNAMIC LOADING

Abstract

Shape memory alloy o ers pseudo-elastic behavior and shape memory e ect owing to their capability of undergoing reversible di usionless solid to solid phase transformation from austenite to martensite depending on temperature and state of stress. Due to its extraordinary mechanical behavior, a wide number of applications of SMA emerge across the various eld of engineering. Recently, porous SMAs, classical variants of these materials are capable of inheriting the properties from both bulk SMA and typical porous materials. Porous SMAs o er lightweight, high-energy absorption capability, good biocompatibility, good damping capacity and high permeability. Accordingly, new areas of application of porous SMA are still emerging. To exploit its potential for future applications, it is highly necessary to understand its structure-property relationship. Recently, some experiments have been carried out to investigate the e ect of porosity on the mechanical behavior of porous SMA. In parallel, micromechanical-based approaches and computational homogenization techniques have been also used to predict the role of porosity on its mechanical behavior. Although major studies focused on the quasi-static response of porous SMA, there is an impetus towards understanding its high strain rate behavior for its potential applications as energy absorbing materials. However, high strain rate behaviors of porous SMA remain unclear until the date. The mechanical behavior of porous SMA will be investigated in the present study for various strain rate regimes using a predictive numerical framework. A nonlinear nite element framework is adopted to solve the governing equations and an explicit time integration algorithm is employed. The porous SMA is idealized with the periodic or random distribution of pore/voids in a dense SMA matrix. Therefore, a typical nonlinear constitutive behavior of SMA is considered for the matrix. A forward Euler algorithm is adopted to solve the nonlinear constitutive behavior. A homogeneous strain rate is applied to the domain, a macroscopic stress-strain behavior and the energy dissipation characteristics are obtained. A parametric study is systematically performed by considering various shapes, sizes and distribution pores in the SMA matrix at di erent strain rates. The role of the geometric and loading parameter on the evolution of martensitic phase transformation and macroscopic stress-strain behavior is addressed. The present study will assist in designing of energy absorbing devices with desired mechanical properties (speci c strength and toughness) for dynamic loading conditions such as car crash, blast mitigation and armor for military applications.