Development of Compact Marchiniak Testing Apparatus for In-situ Microscopic Observation of Surface Roughening

In the fields of medicine, electronics and information, the demand for micro -scale parts has increased significantly. In the metal forming using foil materials, it is known that different deformation behavior from sheet material can be observed. To investigate the surface roughening and plastic strain distribution for metal foils under various biaxial tensile states, a compact Marciniak testing apparatus is newly developed. The developed apparatus is installed on an automatic XY stage of the laser confocal microscope and the deformed specimen can be observed in real time. To confirm the possibility of in-situ observation of surface roughening and plastic strain distribution, the tests such as measurement of strain paths, observation of fracture points and surface roughening is conducted for pure copper foils. As a result, the plastic strain distribution and local necking behavior of the copper foil under various biaxial tensile states including equi-biaxial and uniaxial tensile states can be observed. Moreover, in-situ observation of surface roughening behavior on three proportional loading paths could be conducted. Therefore, an effectivity of the developed apparatus for investigation of surface roughening and plastic strain distribution is found. (C) 2017 The Authors. Published by Elsevier Ltd.