>> “State-space constitutive model for magnetization and magnetostriction of Galfenol alloys” appeared in IEEE Transactions on Magnetics

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We present a thermodynamic model that quantifies the magnetization and magnetostriction of annealed or unannealed Galfenol alloys subjected to magnetic fields and mechanical stresses. The model requires a small number of parameters directly related to physical properties of the data, thus providing a useful tool for material characterization and design. Furthermore, the model is formulated in state-space form, which simplifies computations for design and control of Galfenol devices.

 

P.G. EVANS and M.J. Dapino, “State-space constitutive model for magnetization and magnetostriction of Galfenol alloys,” IEEE Transactions on Magnetics, Vol. 44, Issue 7, Part 1, pp. 1711-1720, July 2008.

>> “Homogenized strain model for Ni-Mn-Ga with collinear field and stress,” appeared in Journal of Intelligent Material Systems and Structures

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Prior experimental measurements by the authors demonstrated large reversible strains of ·0.41% along the [001] crystal direction of a cylindrical Ni 50Mn28.7Ga21.3 rod driven with a magnetic field along the same direction and no external restoring force. The origin of the reversibility is attributed to internal bias stresses generated by impurities absorbed during manufacture of the alloy. This article presents a macroscopic constitutive model for Ni—Mn—Ga strain in collinear field and stress configuration. The switching between two variant orientations in the presence of Zeeman energy and the pinning energy of the impurities is formulated through a Gibbs energy function for the crystal lattice. Inhomogeneous local interaction fields and impurity distributions are addressed through stochastic homogenization techniques. Attributes of the model are illustrated through comparison of model results with strain—field measurements collected at various compressive loads. Constrained optimization is used to determine the necessary parameters and an error analysis is performed to assess the accuracy of the model for various loading conditions. The collinear field and stress configuration can lead to solenoid transducers with enhanced energy density and bandwidth relative to standard electromagnet devices.

 

L.E. FAIDLEY, M.J. Dapino and G.N. Washington, “Homogenized strain model for Ni-Mn-Ga with collinear field and stress,” Journal of Intelligent Material Systems and Structures, Vol. 19, No. 6, pp. 681-694, June 2008.

>> SMSL research on adaptive seat belts featured in June 2008 issue of Machine Design magazine

Smart and small

Get ready for actuators that can fit into smaller spaces, react more quickly, and save weight thanks to smart materials.

Passenger comfort and safety are also behind Professor Marcelo Dapino’s efforts at the Ohio State University Smart Vehicle Concepts Center. Supported by a Honda Initiation grant, Dapino is seeking to incorporate piezoelectric devices into seat belts.

 

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