Kingstedt
High Strain-Rate Mechanics of Materials

High speed imaging is combined with high strain rate loading to probe the evolution of strain localization leading up to failure in Mg alloys. From this study pathways for deformation are identified which lead to undesired shear band formation and crack formation. Show below is a comparison of the strain localization that occurs at a machined defect for three different loading orientations. The left two strain maps demonstrate the ability of two loading orientations to accommodate deformation in regions away from the specimen through hole.  The strain map on the right shows strong localization near the machined defect which leads to the formation of undesirable cracking.

Using infra-red thermography and selected orientations, high strain rate loading is used to evaluate the conversion of plastic work to heat for specific deformation processes in magnesium alloy AZ31B. Mechanisms are approached through studying orientations that accommodate deformation through one of the following mechanisms to the greatest extent possible: 1) basal, 2) non-basal, and 3) deformation twinning.

As the microstructure of a material is refined from the micron scale to the nanoscale there is a significant increase in the interface density of the material. If the density of interfaces is high enough, the macroscopic deformation response can be influenced by the structure of the interface at the nanoscale.  Shown below is a comparison of two interface types, cube-on-cube and incoherent twin.  In the cube-on-cube interface structure the deformation systems are aligned across the interface as is indicated by the identical orientations of the Thomson tetrahedron on both sides of the bi-metallic interface. Alternatively the incoherent interface has a single aligned deformation plane as indicated. The mechanical response is shown for materials that consist predominantly of cube-on-cube and incoherent twin orientation illustrating the difference in material response that can be elicited based on interface structure.