Title page for ETD etd-02232001-114006


Type of Document Dissertation
Author Ionita, Axinte
Author's Email Address ionita@vt.edu
URN etd-02232001-114006
Title Finite Element Analysis of the Deformation of a Rubber Diaphragm
Degree PhD
Department Engineering Science and Mechanics
Advisory Committee
Advisor Name Title
Gao, David Y. Committee Chair
Henneke, Edmund G. II Committee Member
Librescu, Liviu Committee Member
Ragab, Saad A. Committee Member
Reifsnider, Kenneth L. Committee Member
Keywords
  • Finite Element
  • Diaphragm
  • Rubber
  • Eversion
  • Buckling
Date of Defense 2001-02-05
Availability unrestricted
Abstract
Several rubber diaphragms, of the same type used inside an hydraulic accumulator, failed a short time after they were mounted. While there is nothing special with these failures the cost, in some cases can be high. A closer look, at the damaged diaphragms reveal an interesting nonsymmetric radial deformation accompanied in some cases by cracks. Most of the analyses regarding the failures of rubber diaphragms off er explanations only from a chemical or material science point of view.

We propose in this thesis a new perspective from a mechanical-structural engineering view. Therefore the main goal of the thesis is to investigate the deformation of a diaphragm and based on this analysis to propose an explanation for formation of the cracks. It is shown that the analysis of the diaphragm problem leads to a pseudo-nonconservative system and involves a buckling, a post buckling (dynamic snap-through), an eversion, and a load response analysis. The problem is approached numerically using the nite element method. The character of pseudo-nonconservativeness of the system requires, in this case, an update of the tangent sti ffness matrix with a certain sti ffness correction. This new correction is proposed also. The result is valid not only for this particular problem but for the entire class of problems to which the diaphragm belongs. This correction is implemented in an existing nite element program (NIKE3D) and used to analyze the diaphragm deformation. The results indicate that under the typical load condition for a diaphragm a certain deformation pattern occurs, and this can lead to the formation of cracks. This deformation matches extremely well with the actual deformed shape of a typical failed diaphragm. It is shown that the deformation pattern depends on the structural properties of the diaphragm rather than on the magnitude of the applied load. The nonsymmetry in the diaphragm deformation and the difference in the crack development is explained also.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  chapter1.pdf 2.74 Mb 00:12:42 00:06:31 00:05:42 00:02:51 00:00:14
  chapter2.pdf 181.17 Kb 00:00:50 00:00:25 00:00:22 00:00:11 < 00:00:01
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  chapter5.pdf 56.04 Mb 04:19:26 02:13:25 01:56:44 00:58:22 00:04:58
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  dyn3dc1.avi 2.55 Mb 00:11:46 00:06:03 00:05:18 00:02:39 00:00:13
  dyn3dc2.avi 3.42 Mb 00:15:50 00:08:08 00:07:07 00:03:33 00:00:18
  dyn3dc3.avi 2.92 Mb 00:13:31 00:06:57 00:06:05 00:03:02 00:00:15
  dyn3df1.avi 1.25 Mb 00:05:46 00:02:58 00:02:35 00:01:17 00:00:06
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  nik3d1.avi 6.67 Mb 00:30:52 00:15:52 00:13:53 00:06:56 00:00:35
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  nik3d5.avi 2.81 Mb 00:13:01 00:06:41 00:05:51 00:02:55 00:00:14
  nik3d6.avi 5.53 Mb 00:25:36 00:13:09 00:11:31 00:05:45 00:00:29
  nik3d7.avi 7.62 Mb 00:35:17 00:18:09 00:15:53 00:07:56 00:00:40

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