Paulo M.S.T. de Castro

The elastic analysis of arbitrary thin shells having part-through cracks, using the integrated line spring and the semiloof shell elements

Abstract This work describes the Integrated Line Spring Element, which was specially designed to be associated to Semiloof shell elements for the simulation of the structural behaviour of the remaining ligament in a part-through crack in a thin shell. In its formulation, it follows the “line spring model” introduced by Rice and Levy (1972) for virtually infinite plates of small thickness. This element was used to determine the stress intensity factor for internal and external semielliptical cracks in arbitrary shells under mode I, mode II and mode III load conditions.

Fractographic analysis of fatigue crack growth in lightweight integral stiffened panels

Purpose – The purpose of this paper is to complement available macroscopic fatigue crack growth measurements in flat stiffened panels with scanning electron microscopy (SEM) measurements of striation spacing.Design/methodology/approach – The papers approach is fatigue testing of two‐stiffener flat panels manufactured using three different processes, with a central initial crack perpendicular to the stiffeners and load, in order to identify striation spacing during crack growth up to final fracture, using SEM.Findings – An increase of striation spacing as cracks grow was quantified. Although when cracks approach the stiffeners the stress intensity factor decreases, there is no clear decrease of striation spacing in that region. Striation spacing is roughly similar to macroscopic crack‐propagation rate da/dN measured in the panels testing. This observation is no longer valid once the stiffeners are reached; this stage is characterized by fast acceleration of the cracking process until final complete ruptur...