Abstract

This paper describes several recent advances in crack assessment technology that have been or will be incorporated into the API 579 fitness-for-service standard. Four technology areas are addressed herein:

Stress intensity factor solutions. The 2016 edition of API 579 contains an extensive library of stress intensity solutions inferred from 3D finite element analysis.

A new equation for fitting elastic-plastic J solutions. A parametric equation that captures the elastic, fully-plastic and contained-yielding regimes of deformation provides an alternative definition of reference stress in the failure assessment diagram (FAD) method.

An enhanced constraint adjustment. A future edition of API 579 will include an improved version of the Wallin methodology for shifting the Master Curve reference temperature to account for constraint effects.

A procedure to account for non-ideal crack profiles. Most crack assessment methods assume an idealized flaw shape such as semi-elliptical, but many real-world flaws have complex shapes.

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