Tube diameter effect on formability of tube hydroforming was investigated for a vehicle bumper rail section. Four types of loading path were considered and, with changing tube diameter, paths for reducing thinning were identified. By slightly changing diameter only by about 10% (from 90 to 100mm), remarkable reduction to about one-third in thinning rate and more uniform thickness distribution were predicted whichever loading path was applied to the prediction. Also, for tube with smaller diameter than 100 mm (PR = 87.3) feeding was much more influential on suppressing excessive thinning than pre-pressure before tool closed. The benefit from pre-pressure became more distinct as tube diameter become large over 100 up to 110 mm (PR = 96.1) so that, for the 110 mm diameter tube, the pre-pressure was far more effective than feeding for formability including the thinning. The tube with diameter over the limit, which cannot be manufactured by a conventional tool with horizontal split planes, could be successfully hydroformed by utilizing tool with slant split planes and applying only internal pressure without both feeding and pre-pressure. Consequently, for ensuring high formability in tube hydroforming, it is of great importance to select a starting tube with as large diameter as possible through precise examination on tube crushing behavior during tool closing. And, for the selected tube size, a promising loading path should be determined. Also, application of a tool with slant split planes could be an efficient hardware method to improve formability, and it requires further systematic study.
Tube size effect on hydroforming formability
Journal of Materials Processing Technology ; 160 , 1 ; 24-33
2005
10 Seiten, 16 Bilder, 4 Tabellen, 14 Quellen
Article (Journal)
English
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