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Resolution requirements in time-dependent FLC testing

Presentation held at International Deep Drawing Research Group, IDDRG 2015; 31.Mai 2015-03.06.2015, Shanghai, China
Auflösungsanforderungen bei der zeitabhängigen Auswertung des FLC-Versuchs
: Müller, Roland; Riemer, Matthias; Weigel, Patricia; Petters, Romy; Feldmann, Peter; Schatz, Marko; Aswendt, Petra

Präsentation urn:nbn:de:0011-n-3434314 (1.1 MByte PDF)
MD5 Fingerprint: b7e2db6928ae5ffd6e8bdee1062d3df4
Erstellt am: 11.6.2015

2015, 14 Folien
International Deep Drawing Research Group (IDDRG Conference) <34, 2015, Shanghai>
Vortrag, Elektronische Publikation
Fraunhofer IWU ()
deep drawing; FLC test; formability; strain measurement

For evaluation of the formability of sheet metal parts the forming limit diagram (FLD) is a valuable and generally used tool. The formability of the given sheet metal material in the FLD is represented by the forming limit curve (FLC). Typically FLCs are determined experimentally by standardized Nakajima tests using optical strain analysis systems. Other studies detected a huge influence of virtual facet size by stochastic patterns on the determined FLC values in time-dependent evaluation of FLC tests. In this paper the influence of the grid size of square line grids evaluated with the time-dependent method using the strain analysis sys-tem AutoGrid® is studied and compared with results from the evaluation of stochastic pat-terns with high local resolution using the ARAMIS system. The algorithm for time-dependent evaluation of the GDDRG Working Group has been applied for automatic detection of material failure and determination of FLC values. These studies are made for steel as well as aluminum sheet metal materials typically used for car body applications. Different methods and local grid resolutions were investigated for each material and compared with each other. Additionally a comparison between the time-dependent and the section based evaluation of the Nakajima FLC test is carried out. Furthermore all results are double-checked by visual operator´s control concerning the beginning of visible local necking. The experimental results show no significant difference between evaluation of 1 mm and 2 mm square line grids. Furthermore the FLC results evaluated with the AutoGrid® system (1.0 mm as well as 2.0 mm grid size) fit to the results rated by ARAMIS system using approximately 0.5 mm virtual grid size.