© 2002 by the Regents of the University of Minnesota AEM Research on Solid Mechanics and Materials Science Richard James Department of Aerospace Engineering and Mechanics

© 2002 by the Regents of the University of Minnesota Solid Mechanics Faculty n Roger Fosdick: Thermodyamics and continuum mechanics, applied mathematics n Richard James: Phase transformations, active materials, micromagnetics n Perry Leo: Micromechanics of defects in solids, biological materials, composites n Tom Shield: Experimental solid mechanics, shape-memory and magnetostrictive materials, fracture n Lev Truskinovsky: Nonlinear continuum mechanics, thermodynamics, fracture, geophysical applications

© 2002 by the Regents of the University of Minnesota Shape memory effect T

© 2002 by the Regents of the University of Minnesota Ferromagnetic shape memory materials Three important temperatures: Curie temperature of austenite: Curie temperature of martensite Austenite-martensite transformation temperature: first order second order T Two ways to field-induce a shape change: 1) Field-induce the austenite-martensite transformation 2) Rearrange variants of martensite below transformation temperature. picture below drawn with measured lattice parameters of Ni 2 MnGa H

© 2002 by the Regents of the University of Minnesota Magneto-mechanical properties of Ni 2 MnGa) H (010) (100) 30 times the strain of giant magnetostrictive materials

© 2002 by the Regents of the University of Minnesota Ni 2 MnGa cantilever H(t) Energy stored is proportional to h (because of the micromagnetic term ) rather than h 3 picture drawn with measured lattice parameters of Ni 2 MnGa (Electromagnetic force on the cantilever is zero; it is driven by configurational force) Candler/James

© 2002 by the Regents of the University of Minnesota Engineering meets biology Bacteriophage T-4 attacking a bacterium: phage at the right is injecting its DNA 10 C o 70 C o 90 C o Thin film spontaneously forms a tent upon cooling

© 2002 by the Regents of the University of Minnesota Solid Mechanics at the Nanoscale austenite martensite GaAs Sc 0.3 Er 0.7 As Ni 2 MnGa Ga Mn Ni Sc,Er As Ga As Does the shape memory effect occur at extremely fine scales? How do we do engineering at extremely small scales?

© 2002 by the Regents of the University of Minnesota Magneto-mechanical testing machine n ~ 1T at 1 Hz n Field direction variable in-plane n Integrated loading machine n DIC microscope with video and high resolution video camera n Computer control/data acquisition

© 2002 by the Regents of the University of Minnesota Solid mechanics research leads to new materials a (FCT) c (FCT) a 0 (FCC)

© 2002 by the Regents of the University of Minnesota Solid mechanics research leads to new materials n Samples were skin cut from the crystal boule using EDM, and its composition variation was analyzed with Electron Probe Microanalyzer (EPMA).

© 2002 by the Regents of the University of Minnesota Dynamic biaxial magnet n Design in progress: ~ 1T at 1kHz n Single axis prototype built n Applicable to bulk specimens, films, sensors, actuators