Patent ID: 7505885
Filing Date: 2009-03-17
Classification: G06F,Y10T

Abstract:
1. A method for predicting initiation and propagation of a crack along a first direction along a potential crack plane in a structure using a finite element computer model, the method comprising: defining a plurality of at least partially overlapping interface elements at an interface between adjacent first and second layers of the structure, each interface element comprising a plurality of node pairs spaced apart in the first direction, each node pair comprising a first node located at the first layer at the interface and a second node located at the second layer at the interface and coincident in position with said first node when there is no crack opening between said first and second layers at said node pair, the node pairs comprising a middle bound node pair and at least two additional side node pairs spaced on opposite sides of the bound node pair, wherein defining the plurality of at least partially overlapping interface elements comprises defining a succession of said interface elements spaced along the first direction such that one side node pair of one interface element is positioned at the middle bound node pair of an adjacent interface element; establishing a crack between the layers such that a front of the crack is located at the bound node pair of a respective interface element and there is a finite non-zero displacement between the nodes of one of the side node pairs of the respective interface element, the nodes of the bound node pair having input stiffnesses therebetween of effectively infinite magnitudes and the nodes of each side node pair, including both the side node pair having the finite non-zero displacement and another side node pair having a pair of coincident nodes, having effectively zero stiffnesses therebetween; inputting to the finite element computer model having a non-linear solver a mixed mode fracture criterion governing initiation and propagation of the crack; incrementally increases an external loading on the structure using the model and, at each incremented external loading: calculates at least one interlaminar force between the nodes of the bound node pair; calculating associated energy release rate components at the middle bound node pair based on the calculated interlaminar forces between the nodes of the bound node pair and the displacements between the nodes of said side node pair of having the finite non-zero displacement therebetween; and initiating release of the bound node pair if the calculated energy release rate components cause the mixed mode fracture criterion to predict crack initiation and propagation; and incrementally propagating the crack over the plurality of at least partially overlapping interface elements within a single run of the finite element computer model by repeatedly and incrementally increasing the external loading on the structure using the model and initiating release of the bound node pair of each successive interface element.