Delaunay-Tessellation Based Elastic-Plastic Analysis by Body Force Method

The occurrence of small scale plasticity can be modeled physically by force doublets embedded in an elastic medium and therefore the plasticity problem can be treated by the superposition of elastic solutions. This idea for the treatment of an inelastic strain is reviewed and generalized to develop a versatile program for two-dimensional elastic-plastic problems based on Body Force Method. In the present study, a treatment of an elastic-perfect plastic body is discussed in detail. The increment of the density of force doublets, which has one to one correspondence to the increment of plastic strain, can be determined from Prandtl-Reuss equation. It was also found the Delaunay triangulation is useful and convenient for the automated elastic-plastic analysis.

High Temperature Nanoindentation for the Study of Flow Defects

ABSTRACTOur recent progress in elevated temperature nanoindentation is reviewed, with an emphasis on the study of discrete events (i.e., pop-in phenomena) observed during nanoindentation. For crystalline materials the incipient plasticity problem is associated with the nucleation of dislocations, an effect which we show to be significantly temperature dependent. For metallic glasses it is the operation of individual shear bands beneath the indenter that gives rise to pop-in events; here we also show this to be a temperature dependent phenomenon. Approaches to extract the activation volume and energy of defects involved in plastic flow beneath the indenter are also briefly described.