Development of Finite Element Models for Predicting the Mechanical Behavior of the Cracked Pipe

Abstract

In this paper, two theoretical models, micro and macro model, are presented to investigate the effect of circumferential cracks on the structural characteristics of a pipe. In the micro model, the equivalent bending stiffness is obtained based on the energy method and fracture mechanics. Because of the high change of strain energy near the crack location, the variation is represented by reduction in the bending stiffness along the length of the pipe. The development of the macro model is based on a simplified procedure, i.e., the pipe is separated into two segments without any change in the cross section property. Two separated pieces are connected by a rotational massless spring of the infinitesimal length inserted at the crack location. Moreover, it is shown that in the macro model so smaller number of elements are required than the micro model to provide a sufficient accuracy. Finally, the experimental measurements are utilized to validate the proposed models. The deflections and frequencies obtained for several cases through the displacement and vibration method, using the proposed models agree reasonably well with the experimental measurement data.