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Characterizing the Hemming Performance of Automotive Aluminum Alloys With High-Resolution Topographic Imaging

Published

Author(s)

Mark R. Stoudt, Joseph B. Hubbard, John E. Carsley, Susan E. Hartfield-W?nsch

Abstract

The hemming performances of two AA6xxx series aluminum automotive closure panel alloys were evaluated, with and without a 10 % tensile pre-strain, in a simulated three-point bend test that bent samples to a 180 ° angle. The apexes of the bent specimens were examined with scanning laser confocal microscopy (SLCM). High-resolution maps of the surface displacements were constructed from the topographic data and superimposed on the SLCM images to correlate the locations of the maximum surface displacements and the surface morphology. The surface maps were strikingly different even though the results of metallographic, tensile and micro-hardness analyses all indicated that the two alloys were relatively similar. The different morphologies were attributed to different constituent particle size distributions in the two alloys. That is, the alloy with the greater density and broader size distribution of constituent particles had a higher likelihood of particle decohesion. More importantly, the higher particle density increased the likelihood of coalescence of independent decohesion events leading to more concentrated surface displacements. While fracture was not observed in either alloy, the more concentrated surface displacements suggest that the higher particle density increased the propensity for cracking in the apex region.
Citation
Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science
Volume
136

Keywords

Hemming, Closure panels, Deformation-induced surface roughness, Aluminum alloys, Bending, Scanning laser confocal microscopy, Strain localization

Citation

Stoudt, M. , Hubbard, J. , Carsley, J. and Hartfield-W?nsch, S. (2014), Characterizing the Hemming Performance of Automotive Aluminum Alloys With High-Resolution Topographic Imaging, Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, [online], https://doi.org/10.1115/1.4027093 (Accessed July 3, 2022)
Created April 1, 2014, Updated September 25, 2019