Through-wall yield collapse pressure of casing based on unified strength theory

Abstract

The unified algorithm of through-wall yield collapse pressure for casing with due consideration of strength differential (SD), yield-to-tensile strength ratio, material hardening and intermediate principal stress, which is suitable to calculate collapse strength of all casing has been obtained based on unified strength theory, and four classical through-wall yield collapse formulas of casing have been presented based on the L. Von Mises, TRESCA, GM and twin yield strength criterion. The calculated value is maximum based on the twin yield strength criterion, which can be used as upper limit of through-wall yield collapse pressure, and the calculated value is minimum based on the TRESCA strength criterion, which can be used as lower limit of through-wall yield collapse pressure in the design process. Numerical and experimental comparisons show that the equation proposed by this paper is much closer to the collapse testing values than that of other equations. Key words: unified strength theory, casing collapse, through-wall yield, collapse pressure, strength differential, intermediate principal stress