A Mathematical Formalism For Flexural Diaphragm Fatigue Life And Reliability Evaluation.

Abstract

A mathematical formalism is presented for flexural diaphragm fatigue life and reliability evaluation. The use of this formalism enables the diaphragm designer to match a customer's requirements for life and reliability, to the performance characteristics of a diaphragm's geometry. The application requirements for a coupling determine, in conjunction with the geometrical configuration of a diaphragm being evaluated, the stress level that the application loads will induce in the diaphragm profile and ancillary structures. However, as important as a precise knowledge of the induced stress might be, the determination of a design's performance capability is not complete until the induced stresses (including the effects of any stress concentration factors that will be introduced during fabrication) are compared in a physically and mathematically relevant manner to the strength of the material of which the diaphragm is manufactured. The analysis routine presented herein is an effective and accurate methodology for making this comparison. These considerations apply to diaphragms which are operated normally within the limits of their normal load ratings. It must also be mentioned that the analysis above applies only to diaphragms that have not sustained incidental damage in the field. A discussion of the life of a diaphragm which has been subjected to incidental damage is also given.