Design Against Ductile Failure of Casings and Pressure Vessels

Abstract

The extended Gurson model parameters characterizing damage – the initial void volume fraction and the shear damage coefficient - are calibrated for six grades of steel. The former damage parameter of the model is calibrated using data for tensile tests of round notched bars, and the latter damage parameter is determined using data for tensile tests of flat notched specimens. Shear tests are conducted to validate the calibrated parameters, and the model reduplicates the full range of the experimental results adequately, hence demonstrating its capability. The reproduced results support the notion that the failure strain of steels does not solely depend on the stress triaxiality. A relationship between the shear damage coefficient and the material strength is established to delineate the varying dependence of the ductile failure of steels on the Lode parameter. A Lode sensitivity parameter is developed, and the results have manifested that the ductile failure of steel grades with ultimate strengths larger than 400 MPa are sensitive to the Lode parameter, and that the sensitivity increases with the ultimate strength of the steel grade.

Date of Award	12 Dec 2023
Original language	American English
Supervisor	Imad Barsoum (Supervisor)