Burst-Strength Analysis of Finite-Length, Specially Orthotropic Cylinders With Different End Closures

Abstract

An analysis is presented for predicting burst strengths of specially orthotropic, thin-walled cylinders of finite length with different end closures, including (a) rigid ends, (b) hemispherical domes, and (c) a practical case of torispherical domes. Hill’s theory of orthotropic plasticity is used, for materials possessing either power-law or linear strain-hardening characteristic. Numerical results are presented for burst strength of pressure vessels made of a wide range of isotropic materials and having various geometric parameters. Fair agreement was obtained with available test results. The burst strengths of the specially orthotropic cylinders, with anisotropic strength parameter ν > 1, are predicted to be higher than the isotropic cylinders, which is in good agreement with experimental results for texture-hardening titanium-alloy vessels. A finite-length cylinder with rigid ends is the strongest and that with the hemispherical domes is the weakest. The results show that the torispherical domes fall between the rigid ends and the hemispherical domes, as would be expected. Also, the effect of finite length is small for length/diameter (l) > 3, and the effect of different end closures is negligible for l > 2. However, for l < 2, this effect cannot be neglected and becomes more pronounced as l decreases. The results are compared with the allowable values given in the ASME code for unfired pressure vessels for cylinders with hemispherical and with torispherical domes.