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Analysis of a hydraulic port, plug, and flow through fitting subjected to medium pressure shock pulses / by Jeffrey L. Bitant.

by Bitant, Jeffrey L.

Sealing (Technology)

Hydraulic machinery

Fluid power technology

Shock (Mechanics)

Structural analysis (Engineering)

Video recordings

118 leaves : ill. ; 29 cm. + 1 videocassette (kept in AV center) + 1 CD-ROM (in back of book).

Advisor: Thomas Labus.

Introduction and background -- Literature review -- Methodology and materials used in the investigation -- Results and discussion -- Conclusion and recommendations -- References -- Bibliography -- Appendix A) Calculations B) 3-dimension detail drawings of components C) Finite element models D) Pictures from impulse/fatigue testing E) Material from ALGOR® tutorial F) Sections from SAE standards G) Sections from NFPA standard.

The purpose of this project was to analyze a hydraulic connection under the influence of medium pressure shock pulses. In hydraulic circuits, fittings with o-rings are used to connect hoses and tubing at junctions as well as to hydraulic components. The fittings use straight threads and are designed with an elastomeric seal, called an o-ring, which is used as the primary fluid sealing mechanism. The shape of the o-ring is toroidal, and to form an effective seal, the ring is compressed from 10-40% in a static application. From this author's experience working in a test lab and in field service, many hydraulic leaks encountered in circuits are attributed to the failure of the o-ring. This project will examine the damage to fittings when subjected to cyclic test pressures between 3,000 and 8,000 psi. The failure strength of the fitting's thread and o-ring will be determined both experimentally as well as empirically. The major goal of this project is to determine the failure mechanism of a standard straight thread style fittings with o-rings used as the primary sealing mechanism. Results from calculations, modeling and testing concluded that o-rings do show effects from pressure pulses. Threads, ports and fittings showed no adverse effects in pressure ranges tested. Fatigue/impulse testing was performed on three sizes of fittings: SAE sizes -4,-6, and -8, and two different o-ring hardness values of 90 and 70 durometer. Impulse testing of the softer o-rings showed more damage and a permanent set. The harder (90 durometer) showed a set pattern but to a smaller degree. The movement of the o-ring under low pressure pulses predicted by finite element analysis were verified by using a high-speed video camera to view an assembly subjected to pressure pulses. The findings show the o-ring being forced up and conforming to the shape of the cavity when subjected to the pressure pulse.

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