Combination of pressure and axial stress used in this Technical Report to simplify equations.
NOTE: Effective stress as used in this Technical Report does not introduce a distinct, physically defined stress quantity. Effective stress is a dependent quantity, which is determined as a combination of axial stress, internal pressure, external pressure and pipe dimensions, and provides a convenient grouping of these terms in some equations. The effective stress is sometimes called the Lubinski fictitious stress.
Source: API TR 5C3, Technical Report on Equations and Calculations for Casing, Tubing, and Line Pipe Used as Casing or Tubing; and Performance Properties Tables for Casing and Tubing, Upstream Segment, First Edition, December 2008. Global Standards