Abstract
Pure copper rectangular blocks are simply set in a multilayered manner without bonding and compressed up to 50% reduction in height per operation in the plane strain condition. When as-received copper (Cu-H) or precompressed dead-soft copper (Cu-O) is compressed, the interfaces of such multilayered blocks turn into extremely wavy surfaces, while those of virgin Cu-O blocks remain almost flat. This phenomenon may be a kind of diffuse-type instability depending on the work-hardening property (i. e., n-value) of the material. This phenomenon appears more markedly when an aluminum sheet is inserted between the interfaces. When the interface of the two layered blocks becomes saw-toothed, its waviness after compression is reduced to a comparable extent. Furthermore, when two blocks are designed in an hourglass or barrel-type, the interface remains a little wavy with no instability for both specimens with flat and saw-toothed interfaces. The saw-teeth of the interface surprisingly grow in height and width with compression particularly in the central portion of the interface of the barrel-type two-block specimen, inducing complete bonding of the blocks. Finally, when Cu-O severely precompressed up to 87. 5% (-2.1 in log strain) is tested as 8-layered blocks, the specimen fractures along a plane oblique to the compression axis before further deformation. This phenomenon may be a kind of localized (shear band) -type instability.
