Study of the deformation behaviour of homogeneous materials by impression tests

Abstract

An impression test method and analytical procedure have been used to generate the flow characteristics of aluminium, copper, nickel and mild steel. Unlike conventional tests, the flow curves of these materials can be obtained by precise measurements of the displacement of a flat-ended circular cylinder into a specimen at predetermined speeds, during which the indenter makes an impression on the surface of the specimen as a function of the applied load. The depth of penetration at an equivalent stress, speed being constant, is found to be linearly dependent on the diameter of the indenter, varying over a range up to 2 mm in a typical metallographic sample. Thus a simple normalization of displacement with diameter makes the stress-penetration relation independent of indenter size. These results are compared with those obtained from conventional tests and the merits of evaluating parameters by impression tests are discussed.