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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

A high-resolution quantitative surface analysis technique was used to evaluate the surface characteristics of two AA6xxx series aluminum automotive closure panel alloys that were bent to a 180 ° angle in a simulated hemming test. Topographic data were acquired with scanning laser confocal microscopy at the bend apexes of both alloys with and without a 10 % tensile pre-strain. Maps of the local displacements normal to the sheet were superimposed on the topographic data to correlate the locations of the maximum surface displacements and the surface morphology. The two alloys had similar metallographic and mechanical properties; however, quantitative analyses of the height data yielded considerable differences in the surface morphologies. The constituent particle size distributions were identified as a possible source for the differences. That is, the alloy with the greater density and broader size distribution of constituent particles had a higher likelihood for particle decohesion. Moreover, the higher particle density increased the likelihood of coalescence of decohesion events leading to larger surface displacements that were not directly correlated with the underlying microstructure. While splitting was not observed in either alloy, the uncorrelated surface displacements suggest that the higher particle density promoted the development of short surface cracks at the apex.
Citation
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

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 1, 2022)
Created April 1, 2014, Updated November 10, 2018