ON THE APPLICATION OF FINITE-ELEMENT TECHNIQUES IN THE DISPLACEMENT COMPATIBILITY METHOD

The displacement compatibility method was used by Poe, Swift and other s, to evaluate the stress intensity factor in stiffened panels with cr acks. In the displacement compatibility method as they used it, the de formations of both the skin and the stiffening elements have been defi ned with flexibility matrices. In this paper, the governing equations are modified such that the stiffener deformations are described with a stiffness matrix. For the stiffeners, it is more convenient to use a stiffness matrix than a flexibility matrix. The stiffness matrix can b e defined with finite element techniques, allowing a wider range of op tions to model the stiffeners. Such options include the modelling of t he finite width of stiffeners, plastic deformations and geometrically non-linear deformations. It is shown that the solution obtained with t he modified governing equations is identical to the solution of Poe an d Yeh for elastic panels, and comparable to the solution of Creager an d Liu for panels with perfectly plastic strips. The computer time requ ired to solve the modified equations is not increased significantly, c ompared to the original equations. As an example of an application of the modified equations, Creager and Liu's panels have been analysed us ing the net-section yield failure model of Gunther and Wozumi for rive ted stiffeners. In the present modified governing equations, the stiff eners might retain their complexity known from a full finite element a nalysis, without significantly increasing the computer time required f or a parametric study.