Universal SCFs and optimal chamfering in cross-bored cylinders

A three-dimensional finite element computer program was developed to establish the stress distributions and stress concentration factors (SCFs) in chamfered cross-bored cylinders under internal pressure. The displacement formulation using eight noded brick and four noded tetrahedron isoparametric elements was used. The Frontal solution technique was used due to limited computing facilities. For several thickness ratios and cross bore to main bore radius ratios, the variation of SCF with chamfer angle for various chamfer length (clr) ratios was investigated. In each case, a universal SCF value corresponding to a unique value of chamfer angle was established. For most clr and chamfer angle combinations, the SCF was higher than that of a plain cross-bored cylinder. However, for some combinations, the SCF curve had an optimum value lower than that of a plain cross-bored cylinder. In optimal chamfered cylinders with thickness ratio between 2.25 and 3, the SCF was found to increase with decrease of thickness ratio. Where thickness ratio was between 1.25 and 2, a cross bore to main bore radius ratio of 0.075 was found to be a geometrical constant with a corresponding SCF of 2.65. Thick cylinders were found to be more suited to chamfering than thin cylinders. The resulting data in this work provides a useful and quick design tool.