Mechanical Testing Methods Applicable to the Helical Form of Annulus Spacer Components

Abstract

An improved method of testing annulus spacers is developed for both quasi-static and fatigue loading. The quasi-static the test approach compresses a section of the spring between flat platens such that the specimen responds as per the compression of a multitude of rings. An adaptation of this approach for single coil test specimens has also been developed and a single test system accomplishes both the multiple coil and single coil tests.

The fatigue test system applies a reversing torsional load with respect to the axis of the spring to achieve a nominally pure bending state of stress. Special grips were designed to effectively mitigate stress concentrations that might cause premature failure. The static and fatigue test methods are evaluated with specimens from pre-service components. The results are analysed and compared, and it is concluded that the test methods are effective in producing valid and useful data.