The purpose of this study was to determine elastic strength of a high pressure vessel with a radial circular cross bore, for various thickness ratios and cross bore sizes. Seven cross bored cylinders with thickness ratios between 1.4 and 3.0, having both small and large radial circular cross bore were studied. Three dimensional linear finite element analyses were used in this work. It was found that unlike in plain cylinders, the difference in the magnitude of working stresses between the Von Mises' and Tresca's theories in cylinders with radial circular cross bore was insignificant. Besides, the effects of cross bore size and thickness ratio on shearing and working stresses were observed to exhibit similar stress distribution patterns. The magnitude of the working stress in the cylinder increased with the cross bore size, reaching an overall stress factor range of 2.5 to 7.07.

A research to determine an optimal location of a circular cross bore in thick walled high pressure vessels was conducted. Cylinders of thickness ratios of 3.0 down to 1.4 with circular cross bore at varying offset position were studied. The effects of a small circular cross bore, having cross bore to main bore size ratio of 0.1 was studied at nine different offset locations. It was established that offsetting of circular shaped cross bores appropriately reduces the magnitude of Stress Concentration Factors (SCFs). Among the nine offset positions studied, the minimum SCF magnitudes occurred between offset location ratios of 0.685 and 0.9. Besides, the optimal location was found to be at 0.9 offset position at the thickness ratio of 1.4, with a SCF magnitude of 2.312. This SCF magnitude indicated a reduction of pressure carrying capacity of 56.7% in comparison to a similar plain cylinder without a cross bore.

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Finite Element Analysis (FEA) was performed on elastic pressurized thick walled cylinder to determine the optimal location for an elliptical shaped cross bore. Preliminary investigations were performed on a radial elliptical shaped cross bore to establish an optimum diameter ratio in a cylinder with thickness ratio of 2.0.The cross bore diameter with size ratio of 2.0 gave the lowest Stress Concentration Factor (SCF) at 1.89.Henceforth,only the optimal diameter size ratio was used for further optimal analyses. The optimization process was then done on cross bored cylinders of thickness ratios of 1.4 up to 3.0 at various offset locations along the radial X axis of the cylinder. The study covered offset locations between the radial position of the cylinder and the offset ratio of 0.9. The authors established that offsetting of an elliptically shaped cross bores increases the magnitude of SCFs. Overall, lowest SCF occurred at radial position when K=2.5 with a magnitude of 1.733. This lowest SCF magnitude indicated a reduction of pressure carrying capacity of 42.3% in comparison to a similar plain cylinder without a cross bore.

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