Elasto-plastic Collapse Strength Calculation of Casing under Pure External Pressure

In present, there are two main viewpoints about Elasto-plastic collapse calculation criteria of casing under pure external pressure, (1) Tresca´s yield criteria, (2) Mises´s yield criteria. The unified Limit external pressure expression of ideal casing is obtained on twin shear unified strength theory with considering the actual manufacture flaw to correct it. The above different viewpoint is compared with physical test data, which proves elasto-plastic collapse calculation criteria of casing being more consistent with Tresca´s yield criteria and the new model in paper to estimate collapse strength of actual casing in more accurate. In theory, the effect in tension and compression as well as initial geometric flaw with different magnitude of quantity for influence of collapse strength is firstly discussed in this paper, which provides important basis for casing manufacture. It has great practical significance.