Sebastian Cravero

Experimental Evaluation of

This work presents an investigation of the ductile tearing properties for an API 5L X60 pipeline steel using experimentally measured crack growth resistance curves (J-R curves). Use of these materials are motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the Brazilian oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline steels employed side-grooved SE(T) specimen with varying crack size to determine the J-R curves based upon the unloading compliance method using a single specimen technique. Recent developed compliance functions and eta-factors applicable for SE(T) fracture specimens are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline steels using SE(T) specimens with varying geometries.Copyright

Evaluation of Crack Growth Resistance Curves for Pipeline Steels Using Constraint Designed Fracture Specimens

This work provides an estimation procedure to determine J-resistance curves for SE(T) fracture specimens using the unloading compliance technique and the eta-method. In the present study, attention is directed to pin-loaded SE(T) specimens with varying geometry and crack sizes but representative solutions are also included for clamped SE(T) specimens. A summary of the methodology upon which J and crack extension are derived sets the necessary framework to determine crack resistance data from the measured load vs. displacement curves. The extensive plane-strain analyses enable numerical estimates of the nondimensional compliance, μ, and parameters η and γ for a wide range of specimen geometries and material properties characteristic of structural and pipeline steels. Laboratory testing of an API 5L X60 steel at room temperature using pin-loaded SE(T) specimens with side-grooves provide the load-displacement data needed to validate the estimation procedure for measuring the crack growth resistance curve for the material. The results presented here produce a representative set of solutions which lend further support to develop standard test procedures for constraint-designed SE(T) specimens applicable in measurements of crack growth resistance for pipelines.© 2006 ASME

A Constraint-Based FAD Procedure for Defect Assessments of Pipelines

This study explores applications of the failure assessment diagram methodology to predict the failure pressure for high pressure pipelines with planar defects having different geometries (i.e., crack depth and crack length). One purpose of this investigation is to assess the capability of FAD procedures in integrity analyses of high pressure pipelines with varying crack configurations. Another is to address the effectiveness of constraint-corrected FADs to predict burst pressure of low-constraint cracked pipelines. The FAD curves are corrected for effects of constraint based on the Lr-Q trajectories for pin-loaded SE(T) specimens. Full scale burst testing of end-capped pipe specimens with axial surface flaws provides the data needed to compare the failure predictions derived from the FAD procedures. The analyses reveal that the degree of agreement between predicted pressures and experimentally measured values depends rather markedly on the crack size for the tested pipes. Moreover, the analyses also show a potential weak dependence of the predicted pressures on the constraint-based correction scheme. Overall, the results validate the use of FAD-based methodologies for defect assessments of axially cracked pipelines.Copyright

Numerical Correlation of Fracture Behavior in Axially Cracked Pipelines Using Constraint Designed Fracture Specimens

This work explores applications of constraint designed fracture specimens in defect assessments of pressurized pipelines and cylindrical vessels. The primary objective is to gain some understanding of the potential applicability of SE(T) specimens in defect assessments of pressurized pipelines and cylindrical vessels. The present study builds upon the J-Q approach using plane-strain solutions to characterize effects of constraint on cleavage fracture behavior for fracture specimens and cracked pipes. Under increased loading, each cracked configuration follows a characteristic J-Q trajectory which enables comparison of the corresponding crack-tip driving force. A key outcome of this investigation is that toughness data measured using SE(T) specimens appear more applicable for cleavage fracture predictions of pressurized pipelines and cylindrical vessels than standard, deep notch fracture specimens under bend loading. The results encourage further development of constraint-designed SE(T) specimens for fracture assessments of pressurized pipes and cylindrical vessels.Copyright

Defect Assessments of Pipelines Using Constraint Designed SE(T) Specimens

This work presents a numerical investigation of crack-tip constraint for SE(T) specimens and axially surface cracked pipes using plane-strain, nonlinear computations. The primary objective is to gain some understanding of the potential applicability of constraint designed fracture specimens in defect assessments of pressurized pipelines and cylindrical vessels. The present study builds upon the J-Q approach using plane-strain solutions to characterize effects of constraint on cleavage fracture behavior for fracture specimens and cracked pipes. Under increased loading, each cracked configuration follows a characteristic J-Q trajectory which enables comparison of the corresponding crack-tip driving force. The results provide a strong support to use constraint-designed SE(T) specimens in fracture assessments of pressurized pipes and cylindrical vessels.Copyright

Integrity Assessments of Pipelines Using SE(T) Specimens

This work presents a numerical investigation of crack-tip constraint for SE(T) specimens and axially surface cracked pipes using plane-strain, nonlinear computations. The primary objective is to gain some understanding of the potential applicability of constraint designed fracture specimens in defect assessments of pressurized pipelines and cylindrical vessels. The present study builds upon the J-Q approach using plane-strain solutions to characterize effects of constraint on cleavage fracture behavior for fracture specimens and cracked pipes. Under increased loading. each cracked configuration follows a characteristic J-Q trajectory which enables comparison of the corresponding crack-tip driving force. The results provide a strong support to use constraint-designed SE(T) specimens in fracture assessments of pressurized pipes and cylindrical vessels.Copyright