Rafael G. Savioli

J and CTOD Estimation Formulas for C(T) Fracture Specimens Including Effects of Weld Strength Overmatch

This work focuses on an evaluation procedure to determine the elastic–plastic J-integral and Crack Tip Opening Displacement (CTOD) fracture toughness based upon the η-method for C(T) fracture specimens made of homogeneous and welded steels. The primary objective of this investigation is to enlarge on previous developments of J and CTOD estimation procedures for this crack configuration while, at the same time, addressing effects of strength mismatch on the plastic η-factors. The present analyses enable the introduction of a larger set of factors η for a wide range of crack sizes (as measured by the a/W-ratio) and material properties, including different levels of weld strength mismatch, applicable to pipeline and pressure vessel steels. Very detailed non-linear finite element analyses for plane-strain and 3-D models of C(T) fracture specimens with centerline-cracked welds provide the evolution of load with increased load-line and crack mouth opening displacement required for the estimation procedure. Overall, the present study, when taken together with previous investigations, provides a fairly extensive body of results to determine parameters J and CTOD for different materials using C(T) specimens with varying overmatch conditions.

Improved J and CTOD Estimation Formulas for C(T) Fracture Specimens Including Overmatched Weldments

This work focuses on the evaluation procedure to determine the elastic-plastic J-integral and CTOD fracture toughness based upon the η-method for C(T) fracture specimens made of homogeneous and welded steels. The primary objective of this investigation is to enlarge on previous developments of J and CTOD estimation procedures for this crack configuration while, at the same time, addressing effects of strength mismatch on the plastic η-factors. The present analyses enable the introduction of a larger set of factor η for a wide range of crack sizes (as measured by the a/W-ratio) and material properties, including different levels of weld strength mismatch, applicable to structural, pipeline and pressure vessel steels. Very detailed non-linear finite element analyses for plane-strain models of square groove, center cracked C(T) fracture specimens provide the evolution of load with increased crack mouth opening displacement required for the estimation procedure. Overall, the present study, when taken together with previous investigations, provides a fairly extensive body of results to determine parameters J and CTOD for different materials using C(T) specimens with varying overmatch conditions.Copyright

A Micromechanics Approach for Assessing the Applicability of Precracked Charpy Specimens to Determine the T0 Reference Temperature

This work describes an application of a micromechanics model for cleavage fracture to determine the reference temperature for pressure vessel steels from precracked Charpy (PCVN) specimens. A central objective is evaluate the effectiveness of the Weibull stress (σw) model to correct effects of constraint loss in PCVN specimens which serve to determine the indexing temperature T0 based on the Master Curve methodology. Fracture toughness testing conducted on an A285 Grade C pressure vessel steel provides the cleavage fracture resistance data needed to estimate T0. Very detailed non-linear finite element analyses for 3-D models of plane-sided SE(B) and PCVN specimens provide the evolution of near-tip stress field with increased macroscopic load (in terms of the J-integral) to define the relationship between σw and J from which the variation of fracture toughness across different crack configurations is predicted. For the tested material, the Weibull stress methodology yields estimates for the reference temperature, T0, from small fracture specimens which are in good agreement with the corresponding estimates derived from testing of much larger crack configurations.Copyright

Effects of Plastic Deformation on Fatigue Life of Superduplex Steel Tube Umbilical

This work presents an experimental investigation of the effects of plastic strain on the fatigue behavior of superduplex steel tubes. Fatigue tests using conventional axial loading and a resonant bending setup conducted on 15mm OD tubes made of SAF2507 superduplex steel provides S × N data upon which effects of different levels of plastic strain can be assessed. Despite the inherent scatter in the measured fatigue data, the experiments reveal consistent trends and relatively small effects of plastic strain on fatigue behavior of superduplex steel tubes.© 2012 ASME