15.00 - 15.30 Final test
Abstract: It can be shown that crack initiation is a sudden phenomenon except possibly at the tip of a pre-exisiting crack. The crack jumps a given length, hence the name Finite Fracture Mechanics. This length together with the load at failure can be determined solving two inequalities: a stress based inequality ensuring the tensile stress to be larger than the tensile strength all along the expected crack path and an energy based condition that guarantees there is enough energy available to trigger the crack onset. Two approaches are proposed during this lecture to solve this system of inequalities: a full finite element calculation and an asymptotic expansions procedure. The domain of validity, the advantages and drawbacks of both approaches will be discussed.
Israel G. García, Universidad de Sevilla, Spain, “Practical application of the coupled criterion (CC) of FFM”
Abstract: The aim of this lecture is to present how the coupled criterion can be applied easily to predict crack initiation. The lecture will focus on presenting the different strategies and tools which can be used to solve problems of crack initiation using this criterion, from a practical perspective. After presenting the general strategy, some examples will be displayed.
Pietro Cornetti & Alberto Sapora, Politecnico di Torino, Italy, “FFM: from static to fatigue failure”
Abstract: The coupled criterion of Finite Fracture Mechanics (FFM) was introduced to investigate the crack initiation in brittle notched structures. The approach has been recently extended to assess the fatigue limit of metallic elements containing defects. Restricting the analysis to mode I loading conditions, and focusing on short cracks, circular holes, V- and U-notches, the talk underlines similitudes and differences between the FFM approaches to the static and fatigue frameworks.
Zohar Yosibash, Tel Aviv University, Israel, “Edge and vertex singularities in 3D elastic domains and computation of edge-stress-intensity-functions”
Abstract: The singular elastic solution in the vicinity of a straight and circular 3D crack will be presented, and shown to be different compared to the 2-D Williams’ expansion. Especially, the known J-integral and the standard contour-integral-method, for the computation of stress-intensity-factors, are shown to be path dependent if taken on a plane perpendicular to the crack front. We shall present the full singular solution for the edge and the vertex, and provide an alternative method, named Quasi-dual-function method (QDFM) that may compute the edge stress intensity functions along a 3D crack front.