Effect of tool speed on FLC curve position for DX56D

Abstract

Experimentally determined forming limit curves (FLC) are often used to evaluate formability in sheet metal forming. These curves represent the limits of the formability of the material. The most widely used procedure for the experimental determination of the breaking point of sheet metal is formulated in EN ISO 12004-2. The FLC curve was measured for material DX56D + Z100-M-C-O using the Nakajima test on a BUP 600 universal test machine. The test setup and sample shape correspond to EN ISO 12004-2 except for the punching speed, which was increased from 2 mm/s to 10, 14, and 17 mm/s against the conditions defined in the standard. A non-contact optical system ARAMIS from GOM was used to measure the deformation. A stochastic pattern was applied to the samples to ensure the quality of the measurements, and the Erichsen adhesion test was performed. To determine other properties of the material, the microstructure of the material in the fracture area was observed in the metallographically prepared samples. During analysis, the microstructure was monitored with regard to the state of deformation (deep drawing, plane deformation, and more axial stress). Observations were made on samples with an etched structure using an optical microscope and an electron microscope, where, among other things, the distribution of particles, their size, and chemical composition were observed.