Method for the prediction of rupture in corroded transmission pipes subjected to combined loads
First Claim
1. A method of determining an internal pressure required for rupturing a selected portion of a pipeline, said pipeline being made of a material having a limit strain value, said method comprising:
- (a) obtaining a radius of curvature of the selected portion of the pipeline;
(b) obtaining a thickness of the selected portion of the pipeline;
(c) defining a failure criterion for the material in terms of a hoop stress and an axial bending stress;
(d) determining the effect on a stress-strain relation of the selected portion of the pipeline from a preloading; and
(e) determining a remaining hoop strain capacity from steps (a)-(d) needed for the material to shed an axial stress, said remaining hoop strain capacity being used in determining the internal pressure needed for rupturing.
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Abstract
A method of predicting rupture failure for corroded transmission pipelines uses a model that accounts for the effects of residual and thermal stresses, and settlement of the pipe following installation. The pressure required for failure under a fixed bending moment is different from the pressure required wherein the same bending moment is produced by the settlement of the pipe because the bending compliance increases with plastic straining. The failure criterion depends upon whether or not the hoop strain exceeds the difference between the ultimate hoop strain limit of the material and the remaining hoop strain capacity needed for the material to shed the axial stresses due to bending.
34 Citations
9 Claims
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1. A method of determining an internal pressure required for rupturing a selected portion of a pipeline, said pipeline being made of a material having a limit strain value, said method comprising:
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(a) obtaining a radius of curvature of the selected portion of the pipeline; (b) obtaining a thickness of the selected portion of the pipeline; (c) defining a failure criterion for the material in terms of a hoop stress and an axial bending stress; (d) determining the effect on a stress-strain relation of the selected portion of the pipeline from a preloading; and (e) determining a remaining hoop strain capacity from steps (a)-(d) needed for the material to shed an axial stress, said remaining hoop strain capacity being used in determining the internal pressure needed for rupturing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification