Cylindrical shell pressure vessel profile variation footprint in strain comparison of test data with numerical analysis

The strain comparison of a pressure vessel made of HSLA 15CDV6 in a cylindrical shell membrane region in a pressure test is discussed in this paper. Non-linear finite element analysis (FEA) of thin-walled cylindrical pressure vessels has been carried out using ANSYS. Hoop strain obtained from FEA is not compared well with the pressure test data at the membrane location of the cylindrical shell where the strain gauge is mounted. So to explain the reasons for the difference in strains at the membrane region, the profile of the cylindrical shell at strain gauge region has been measured. The 3D FEA of the cylindrical region with the measured profile is performed. It is found that with measured profile the FEA is giving the strain close to measured strain in the hoop direction. This leads to the increase in strain and stress as having been demonstrated through mathematical modeling in the deviated profiles variations of cylindrical shells. Therefore, the stresses in the deviated region are greater than those that would exist in an undeviated cylindrical shell, which reduces the margin of safety with respect to the yield strength of the material and causes stress concentration. The details of the stress analysis carried out including the effect of measured 3D profile variation are discussed in this paper.