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Proceedings Paper

Computation of fracture toughness of giant magnetostrictive material
Author(s): Tamunoiyala S. Koko; Phil A. Rushton; Calvin V. Hyatt
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Paper Abstract

Magnetostrictive materials such as Terfenol-D are increasingly being considered for demanding applications such as active noise damping, sonar devices and reactive structures, due to their large strain capability. A limiting factor for the use of magnetostrictive material slies in their inherent susceptibility to brittle fracture. The present study applies finite element technology in support of experimental investigations to assess the mode II fracure toughness of magnetostrictive materials. In this exploratory effort, the fully coupled non-linear behavior of the material is not considered. Rather, a methodology for converting the applied magnetic field to an equivalent mechanical load, based on the material's magnetostrictive properties, is devised and applied. The DSA-VAST finite elemtn software is emlpoyed to model the cylindrical, pre-cracked test specimen using both conventional solid elements and enriched twenty-noded solid fracture elements. Two load cases are investigated, namely one in which a mechanical load is applied to the specimen in the absence of a magnetic field, and a second case in which both a magnetic field and a mechanical load are applied to the specimen. In the absence of an applied magnetic field, the mode II fracture toughenss is found to be approximately 4.497 MPa√m, a value comparable to that reported for ceramic-like materials. On the other hand, in the presence of an applied magnetic field (simulated by an equivalent compressive prestress), the mode II fracture toughness is reduced to 2.768 MPa√m, a significant reduction from the 'zero-field' value. FE results indicate significant specimen bending and an appreciable mode III component to the fracture behavior, both of which are consistent with observed crack growth patterns in laboratory specimens.

Paper Details

Date Published: 13 August 2003
PDF: 11 pages
Proc. SPIE 5053, Smart Structures and Materials 2003: Active Materials: Behavior and Mechanics, (13 August 2003); doi: 10.1117/12.484747
Show Author Affiliations
Tamunoiyala S. Koko, Martec Ltd. (Canada)
Phil A. Rushton, Martec Ltd. (Canada)
Calvin V. Hyatt, Defence Research and Development Canada (Canada)

Published in SPIE Proceedings Vol. 5053:
Smart Structures and Materials 2003: Active Materials: Behavior and Mechanics
Dimitris C. Lagoudas, Editor(s)

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