Published: Jan 1992
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The deformation and fatigue behavior of a tubular component under repeated flexural bending and static internal pressure are investigated. The bending strains induced in the component result in gross cyclic plasticity and fatigue lives on the order of a few hundred cycles. Results from a case study are presented that describe considerations in measuring dynamic, high elongation strains using a variety of experimental techniques during full-scale component testing. Measured strains are used with an incremental plasticity model to compute corresponding tube stresses and utilized in an algorithm to predict tube fatigue behavior. A number of local strain-based multiaxial fatigue theories are investigated, including several critical plane approaches, an extension of Sines methodology, an approach which considers hydrostatic stress effect and plastic work. Several of the theories make reasonable life estimates for tests involving negligible internal pressure but do not reflect the damage imposed by higher values of internal pressure. Nonlinear damage summation may be required to correlate fatigue lives.
fatigue life, pressurized tubing, flexural bending, gross plasticity, cyclic plasticity, multiaxial plasticity, multiaxial fatigue, cumulative damage, nonlinear damage, crack initiation, critical plane, plastic work, hydrostatic stress
Assistant Professor, The University of Tulsa, Tulsa, OK
Development Scientist, Dowell Schlumberger Research Center, Tulsa, OK