Experimental and Theoretical Studies of Spatio-Temporal Instabilities in Novel Materials

摘要

Progress has been made on fundamentals and applications of gradient theory to unresolved problems in mechanics and materials at all scales of observations: from nano and micro scales to meso and macro scales. After a general overview of gradient theory is provided and state of the art background, five specific areas of accomplishments are discussed. (1) Fundamental aspects of gradient theory including the origin of gradient terms and form of gradient coefficients; (2) The use of gradient elasticity to study cracks and dislocations, and, in particular, to eliminate the strain singularities at the crack tip and dislocation core as well as the use of gradient theory to discuss the problem of elastic and inelastic interfaces. (3) The use of gradient- dependent dislocation dynamics and gradient plasticity to understand the ladder like dislocation structure of persistent slip bands and their spatial arrangement; (4) The use of gradient theory to understand size effects on mechanical properties; (5) Experimental and modeling studies on nanostructured metals. These are delivered in two parts (a) deformation and fracture mechanisms at the nanoscale for thin films. (b) massive shear band formation at the nanoscale for bulk materials. A list of 50 refereed publications which appeared during the last years included.