STZTheory

=Shear Transformation Zone Theory of Non-crystalline Plasticity=



Shear Transformation Zone (STZ) Theory is a set of equations that build upon ideas developed by Ali Argon, who coined the term "shear transformation zone" to describe metallic glass deformation, and related ideas developed by Frans Spaepen who developed a free volume theory of deformation in metallic glass. The STZ theory begins with the following hypotheses:


 * Glasses contain localized defects, called STZs, that can undergo stress induced transformations which release elastic energy.
 * These defects have an orientation. The orientation is determined by the stress that is most likely to induce transformation of the STZ.
 * The STZs are inherently two-state systems. That is once an STZ transforms it cannot repeatedly undergo the same transformation, though it can undergo the reverse transformation.
 * STZ activity causes surrounding STZs to be annihilated and new STZs to be created in the surrounding material.

The following references give the development of the constitutive theory:


 * 1) M.L. Falk and J.S. Langer, "Dynamics of Viscoplastic Deformation in Amorphous Solids," Physical Review E, Vol. 57, pp.7192 (1998). [|link]
 * 2) L. Pechenik and J.S. Langer, "Dynamics of shear-transformation zones in amorphous plasticity: Energetic constraints in a minimal theory," Physical Review E, Vol. 68, pp.061507 (2003).[|link]
 * 3) J.S. Langer, "Dynamics of shear-transformation zones in amorphous plasticity: Formulation in terms of an effective disorder temperature," Physical Review E, Vol. 70, pp. 041502 (2004). [|link]

These papers provide applications and extensions of the theory:


 * 1) L. O. Eastgate, J. S. Langer, and L. Pechenik, "Dynamics of Large-Scale Plastic Deformation and the Necking Instability in Amorphous Solids," Physical Review Letters, Vol. 90, pp. 045506 (2003).[|link]
 * 2) M.L. Falk, J.S. Langer and L. Pechenik, “Thermal Effects in the Shear-Transformation-Zone Theory of Amorphous Plasticity: Comparison to Metallic Glass Data,” Physical Review E, Vol. 70, pp. 011507 (2004).[|link]
 * 3) J. S. Langer and Anaël Lemaître, " Dynamic Model of Super-Arrhenius Relaxation Rates in Glassy Materials," Physical Review Letters, Vol. 94, pp. 175701 (2005). [|link]

These papers are essential to the background of the STZ theory:


 * 1) F. Spaepen, "A microscopic mechanism for steady state inhomogeneous flow in metallic glasses," Acta Metallurgica, Vol. 25, pp. 407 (1977). [|link]
 * 2) A.S. Argon, "Plastic deformation in metallic glasses," Acta Metallurgica, Vol. 27, pp. 47 (1979). [|link]
 * 3) A.S. Argon and L.T. Shi, "Evelopment of viscoplastic deformation in metallic glasses," Acta Metallurgica, Vol. 31, pp. 499 (1983). [|link]
 * 4) A. Ruina, "Slip Instability and State Variable Friction Laws," J. Geophys. Res., Vol. 88, pp. 10359 (1983).
 * 5) J. H. Dieterich and B.D. Kilgore, "Direct Observation of Frictional Contacts: New Insights for State-dependent Properties," PAGEOPH, Vol. 143, pp. 283 (1994).