The effect' of chamfer angle and size on the stress distributions and stress concentration faci'ors in thick walled cylinders with cross bores under internal pressure
John, M Kihiu
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The stress distributions in a closed ended thick walled cylinder with a chamfered cross bore under internal pressure were investigated. Attention was paid to the region forming the surface of the cross bore. The finite element method was used for this study. The cylinder structure was discretized according to the finite element method requirements and the various types of elements used were discussed. A computer prograrrme in FORTRAN 77 code was developed for this analysis. The stresses and the stress concentration factors evaluated around the cross bore were displayed in both graphical and tabular forms. The effect of changing the chamfer angle for a fixed chamfer size, on the stress distributions was investigated and discussed. Holding the chamfer angle constant and varying the chamfer length, the effect on the stress concentration factors was discussed. The optimum chamfer angle and chamfer length for any cylinder configuration was studied and established. To appreciate the effect of chamfering on cross bores, thick walled cylinders with plain cross bores were analyzed for stress distributions and stress concentration factors. The results were compared to those obtained from the case when the cross bore was chamfered. In order to confirm the accuracy of the finite element computer code, a thick walled cylinder without a cross bore was analyzed for hoop stress distributions and these results compared fairly well with the analytical values. All the results obtained in this study were compared against the previous research results by-various authors in the field of stress distributions and stress concentration factors in thick walled cylinders 'wi.t.hnozzles of various geometry. Design codes for pressure vessels with nozzles were studied and comparison was done with the results of the present work. The importance o~he knowledge and practice of the stress iii distributions in designing pressure vessels for reliability, safety and economy of cylinder material was discussed and emphasized. The study revealed that adding chamfers to cross bores causes a redistribution and reduction of the stresses attained in internally pressurized thick walled cylinders. For a thick cylinder of a given thickness ratio and cross bore diameter, it was observed that the stresses were a minimum at a specific chamfer angle and size. It was established that designing a thick walled cylinder with this optimum geometry effects savings in materials, labour and fabrication costs. In comparison with other researchers, the results of this study proved to be accurate enough and could even have been more accurate if further work was conducted by refining the geometrical mesh further.