Load relaxation of helical extension springs in transient thermal environments |
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Authors: | R C Dykhuizen C V Robino |
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Affiliation: | (1) Sandia National Laboratories, 87185 Albuquerque, NM |
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Abstract: | The load relaxation behavior of small Elgiloy helical extension springs has been evaluated by a combined experimental and
modeling approach. Isothermal, continuous heating, and interrupted heating relaxation tests of a specific spring design were
conducted. Spring constants also were measured and compared with predictions using common spring formulas. For the constant
heating rate relaxation tests, it was found that the springs retained their strength to higher temperatures at higher heating
rates. A model, which describes the relaxation behavior, was developed and calibrated with the isothermal load relaxation
tests. The model incorporates both time-independent deformation mechanisms, such as thermal expansion and shear modulus changes,
as well as time-dependent mechanisms such as primary and steady state creep. The model was shown to accurately predict the
load relaxation behavior for the continuous heating tests, as well as for a complex stepwise heating thermal cycle. The model
can be used to determine the relaxation behavior for any arbitrary thermal cycle. An extension of the model to other spring
designs is discussed. |
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Keywords: | heating relaxation helical extension springs isothermal heating |
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