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The influence of dent imperfections on the elastic stress behavior of cylindrical shells
is explored . This problem is of central importance to the prediction of fatigue failure
due to dents in petroleum pipelines . Using an approximate technique called the
Equivalent Load Method , a semi -analytical model of two -dimensional dent stress
behavior is developed . In the three -dimensional situation , decreased dent localization ,
in particular dent length , and increased dent depth are confirmed to cause dent stress
concentration behavior to shift from having a single peak at the dent center to having
peaks at the dent periphery . It is demonstrated that the equivalent load method
does not predict this shift in stress behavior and cannot be relied upon to analyze
relatively small , deep imperfections . The two stress modes of dents are associated
with two modes of dent fatigue behavior that have significantly different fatigue lives .
A method for distinguishing longer lived Mode P dents from shorter lived Mode C
dents based on two measured features of dent geometry is developed and validated .
An approach for implementing this analysis in the evaluation of real dents is also
suggested . |
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