Development of a Pneumatic High Speed Nakajima Testing Device

Abstract

Forming limit diagrams are an essential tool for describing the formability of sheet materials in the deep-drawing process. Here, the well known and frequently employed procedures are the Nakajima and the Marciniak-Tests. Whereas these procedures' standardisation is quite advanced in the quasi-static range, numerous different test procedures exist in the range of elevated forming speeds. In the first part of this work, an overview of the various procedures is given for generating forming limit diagrams in the high speed range. In the second part, a pneumatically operated testing device is introduced which was developed at the Institute for Material Science for performing Nakajima-Tests in the high speed range. Using this device, standard specimens can be dynamically formed according to the Nakajima-Test. The testing device is to be employed for scientifically exploring the deformation mechanisms operating at very high forming speeds. The testing device’s mode of functioning is demonstrated by means of forming discs of an EN AW-6082 aluminium alloy sheet. In doing this, the testing apparatus is mainly characterised by holding the testing conditions constant during the tests: This particularly concerns the velocity of the tool for forming the sheet discs.