Library and Archives Canada Bibliotheque et Archives Canada Published Heritage Branch 395 W ellington Street Ottawa ON K1A 0N4 CanadaY our file Votre referen ce ISBN: 9 7 8 -0 -4 9 4 -3 3 5 1 8 -5 O ur file N otre referen ce ISBN: 9 7 8 -0 -4 9 4 -3 3 5 1 8 -5 ABSTRACT This thesis presents the theoretical and finite element analyses o f crack-face closure behavior in shells and its effect on the stress intensity factor under a bending load condition. Various shell geometries, such as spherical shell, cylindrical shell containing an axial crack, cylindrical shell containing a circumferential crack and shell with double curvatures, are all studied. In addition, the influence o f material orthotropy on the crack closure effect in shells is also considered. The theoretical formulation is developed based on the shallow shell theory o f Delale and Erdogan, incorporating the effect o f crack-face closure at the compressive edges. The line-contact assumption, simulating the crack-face closure at the compressive edges, is employed so that the contact force at the closure edges is introduced, which can be translated to the mid-plane o f the shell, accompanied by an additional distributed bending moment. The unknown contact force is computed by solving a mixed-boundary value problem iteratively, that is, along the crack length, either the normal displacement o f the crack face at the compressive edges is equal to zero or the contact pressure is equal to zero. It is found that due to the curvature effects crack closure may not always occur on the entire length o f the crack, depending on the direction o f the bending load and the geometry o f the shell. The crack-face closure influences significantly the magnitude o f the stress intensity factors; it increases the membrane component but decreases the bending component. The maximum stress intensity factor is reduced by the crack-face closure. The significant influence o f geometry and material orthotropy on rack closure behavior in shells is also predicted based on the analytical solutions.iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.Three-dimensional FEA is performed to validate the theoretical solutions. It demonstrates that the crack face closure occurs actually over an area, not on a line, but the theoretical solutions o f the stress intensity factor and the FEA solutions are in good agreement, because the contact area is very small compared with the shell thickness.iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.