Shape Memory Alloy Cellular Solids.

Shape Memory Alloy;Honeycomb;Instability;Bloch Wave;Finite Element Analysis;Energy Absorption;Aerospace Engineering;Engineering;Aerospace Engineering

Michailidis, Petros A.Grummon, David S. ;

University of Michigan

关键词: Shape Memory Alloy;    Honeycomb;    Instability;    Bloch Wave;    Finite Element Analysis;    Energy Absorption;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/64596/pamich_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Nitinol (NiTi) shape memory alloy honeycombs, fabricated in low densities using a newbrazing method, recently demonstrated enhanced shape memory and superelastic propertiesby exploiting kinematic amplification of thin-walled deformations. The realization of suchadaptive, light-weight cellular structures opens interesting possibilities for design and novelapplications. This dissertation addresses the consequent need for design and simulationtools for engineers to make effective use of such structures.The focus of the initial portion of the work is the analysis of the response and stabilityof superelastic honeycombs with a hexagonal unit cell. A hysteretic, rate-independentpseudoelastic material model is implemented in a research finite element code (FEAP),along with a small strain - large rotation beam element. The Bloch wave representationtheory is used to efficiently predict the onset of instability during compression of an infinitehoneycomb. A parameter study is performed to investigate the influence of differentmaterial laws on the behavior of an infinite and finite honeycomb. It is demonstrated thatthe response and stability of the infinite case gives insight to the behavior of a finite perfectand finite imperfect honeycomb.Subsequently, employing a generalized hexagonal unit cell, the exact dimensions of which are varied, and adopting the methods developed in the earlier part of this work, the kinematic amplification of the thin walled structure is exploited in the design of reusable kinetic energy absorbers. Contour plots are provided, that allow to obtain the highest absorbed energy to honeycomb weight ratio for a given maximum allowable reaction force of the compressed honeycomb. Finally, a constitutive model that demonstrates both superelasticity and shape memory effect (SME), still focusing on the rate-independent case, is described and implemented. It is determined that simulated honeycombs credibly capture the essential characteristics of the SME, while they exhibit bifurcated paths during both low and high temperature compressive cycles.