Estimation of Stresses at Knuckle of Variable Thickness in Torispherical Heads

摘要

This investigation is concerned with stress analysis of torispherical heads with variable knuckle thickness obtained by spline curve method. Stress analyses are carried out axisymmetric solid elements: (i) four-node quadrilateral (ii) four-node quadrilateral with incompatible mode and (iii) eight-node quadratic. Models were analysed for various combinations of geometric parameters: (i) ratio of dome to knuckle radius (β) and (ii) ratio of maximum knuckle thickness to cylinder thickness (γ ). The results are presented in three parts: (i) deformed configurations, (ii) meridional axial stresses (principal stress) and (iii) von Mises stresses. Three FE models are obtained by refining the element sizes through the thickness (i) one element (ii) two elements (iii) four elements across the thickness. A comparative study of three axisymmetric elements with three refinements has been presented through the use of von Mises stress index. The numerical results indicate that (i) the four-node quadrilateral element with incompatible mode and eight-node quadratic element exhibit more or less same performance, (ii) In view of the smaller size of the problem, the former is recommended, (iii) The use of variable thickness reduces the stress level leading to lower von Mises stress indices and (iv) the failure initiates always in the inner surfaces