Abstract

The fountainhead objective of this research is to establish a well defined procedure for the design of free hydrofonning of thin and thick tubular components. Excessive applied internal pressure leads to tube thinning while excessive applied axial feed leads to tube wrinkling. The established procedure should output internal pressure versus axial stroke curves to be input to the hydraulic press machine in order to freely hydrofom1 tubes with minimum thinning and without wrinkling. In the present work, three tubes having thickness values of 3.00mm, 6.35mm, and 7.50mm are analyzed. An analytical procedure is used to generate axial stroke curves to be applied on the moving ram in order to feed material into the bulging part of the tube. It is assumed that the bulge contour takes the shape of a second order function during bulging. The circular-arc and parabola functions are used to, analytically, calculate the volume of the tube bulged part by revolving these functions 360° about the tube longitudinal axis. It is also assumed that the tube initial thickness is maintained constant throughout the whole bulge contour at all bulge heights. Using volume constancy, the stroke that should be applied on the tube end is calculated for every •, selected bulge height to generate the axial feed curve. The analysis consists of 2D (axisymmetric) models and a 3D model. The 3.00mm and the 6.35mm tubes are used in the 2D analysis while the 7.50mm tube is used in the 3D analysis. The 2D analysis includes unsymmetric and symmetric tubes. No geometrical symmetry exists about the bulging zone axis for the unsymmetric tubes. On the other hand, geometrical symmetry exists about the bulging zone axis for the symmetric tubes. The axial stroke curves generated from the circular-arc and parabola functions were very close. However, the axial stroke curves generated from the assumption of the parabola function were used throughout the study since bulging of the symmetric tubes takes more of a parabolic pattern than a circular-arc pattern. The finite element method is used, throughout the present work, to model and analyze bulging of the three tubes where four different loading conditions are applied.

The loading conditions include: (1) applying internal pressure only and fixing both tube ends (fix loading condition), (2) applying internal pressure only and allowing one tube end to be free in the unsynrn1etric tubes, and both tube ends to be free in the sy11U11etric tubes (free-end loading condition), (3) applying internal pressure and the axial stroke obtained from volume constancy (feed loading condition), and (4) applying internal pressure and axial stroke which is a linearization of the stroke curve obtained from volume constancy (shifted-stroke loading condition). The analysis showed that the bulge heights reached by the sy11U11etric tubes are higher than the bulge heights reached in the unsy11U11etric tubes. It was noticed that the most severe thinning occmTed in the fix loading condition in the 2D analysis. Thinning was noticeably reduced when axial stroke was applied (the feed and shifted­stoke loading conditions). The least thi1rning occurred in the shifted-stoke loading condition. However, skewing of the bulge contour from bulging zone axis exceeded the 3.00% preset skew limit in the unsymmetric tubes. The feed loading condition recorded the second noticeable thinning reduction and confom1ed to the 3.00% preset skew limit. No skewing occurred in all the symmetric tubes. Moreover, no skewing of the bulge contour occurred in the fix loading condition for the unsymmetric tubes. It was also noticed that the magnitudes of the reaction forces on the moving rams increase as the tube thickness increases. The 7.5011U11 tube recorded the highest reaction force magnitudes followed by the 6.35mm and 3.00mm tubes respectively. The magnitudes of the reaction forces on the moving rams in the unsy11U11etric tubes recorded higher magnitudes than those obtained in the symmetric tubes. Tube bursting in the fix loading condition could not be detected in the simulation because the forming limit diagrams of the materials currently used in tube hydroforming are under development.

School

School of Sciences and Engineering

Date of Award

2-1-2003

Online Submission Date

1-1-2002

First Advisor

Maher Y.A. Younan

Second Advisor

Mahmoud N.Shatla

Committee Member 1

Abdallah S. Wifi

Committee Member 2

Medhat A. Haroun

Committee Member 3

Ezzat Fahmy

Document Type

Thesis

Extent

166 leaves :

Library of Congress Subject Heading 1

Tubes.

Library of Congress Subject Heading 2

Finite element method.

Rights

The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.

Call Number

Thesis 2002/6

Location

mmbk

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