Detection and characterization of surface cracking in sheet metal hemming using optical method

S. J. Swillo, G. Lin, S. J. Hu, K. Iyer, J. Yao, Muammer Koç, W. Cai

Research output: Contribution to journalArticle


A new method and optical system have been developed to detect crack initiation during bending and hemming, and to characterize the surface quality on the bent/hemmed region. To detect the initiation of cracking during hemming, the cumulative lengths of micro-cracks are plotted against the total numbers of micro-cracks. The maximum number of micro-cracks is used to detect the initiation of cracking as the micro-cracks merge to form macro-cracks. The average length of the micro-cracks from each captured image of the hemline surface is used as an index for surface quality evaluation. Experimental results on the hemmed surface of an AA6111-T4 sheet demonstrate the validity of the proposed method. Furthermore, the average lengths of micro-cracks corresponding to cracking are found to be nearly constant, regardless of hemming process conditions.

Original languageEnglish
Pages (from-to)49-55
Number of pages7
JournalTransactions of the North American Manufacturing Research Institute of SME
Publication statusPublished - 2005
Externally publishedYes



  • Average length
  • Cumulative length
  • Hemming
  • Image processing
  • Surface crack

ASJC Scopus subject areas

  • Engineering(all)

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