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Research Papers

Stability of Viscoelastic Rings Under Radial Loads With Applications to Nuclear Technology

[+] Author and Article Information
Craig G. Merrett

Mem. ASME
Assistant Professor
Department of Mechanical
and Aerospace Engineering,
Carleton University,
Ottawa, ON K1S 5B6, Canada
e-mail: craig_merrett@carleton.ca

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received January 16, 2015; final manuscript received April 1, 2015; published online April 30, 2015. Assoc. Editor: Chad M. Landis.

J. Appl. Mech 82(6), 061002 (Jun 01, 2015) (7 pages) Paper No: JAM-15-1020; doi: 10.1115/1.4030309 History: Received January 16, 2015; Revised April 01, 2015; Online April 30, 2015

The mechanics of an elastic helical coil are well known; however, the replacement of the elastic material with a viscoelastic material introduces a time dependency that requires a re-examination of the mechanics. A new theory has been developed that allows the prediction of the time to instability as a function of load, viscosity, and relaxation time, and is applied to an exemplar polyvinyl chloride (PVC) ring. The PVC ring shows that twist buckling dominates the instability, and the maximum critical time is approximately 90% of the relaxation period of the material achieved at a viscosity of 50%. Some viscosity is desirable to utilize the energy dissipation ability of a viscoelastic material. The new theory has a practical application in the field of nuclear reactor component design because the metals within the reactor are exposed to elevated temperatures thus exhibiting viscoelastic behavior. The Canadian Deuterium (CANDU®) reactor uses garter springs as spacers within the calandria of the reactor, and these spacers have been observed to move. A better understanding of the mechanics of the spacers may lead to improved spacer design.

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References

Figures

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Fig. 1

Tight fitting spacer between pressure tube and calandria tube

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Fig. 2

Reference ring with parameters

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Fig. 3

Garter spring coil with opposing point loads

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Fig. 4

Critical time for in-plane buckling

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Fig. 5

Critical time for twist buckling

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Fig. 6

Critical time with all displacement modes

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Fig. 7

Comparison of the critical loads for an elastic ring

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