In many cases it is important to know whether a crack will propagate. Simulating this requires special techniques, especially for sharp cracks. In a perfectly sharp crack, loading is applied to a single point, causing a singularity with an infinitely large stress. In a simulation it is not possible to obtain an infinitely large stress. The loading will be localised in a single element and therefore the results will depend strongly on the mesh, which is unwanted. In the real world, perfectly sharp cracks do not exist; a crack will always have a finite thickness. Because this thickness is very small, it is difficult to measure and take into account numerically. Because the stress at a crack depends strongly on the mesh/thickness of the crack, looking at stress to determine whether a crack will propagate does not work well. Instead, other measures are used. One of these is the stress intensity factor (K), which describes how quickly the stress increases towards the crack, assuming a linear elastic material. Another is the J-integral, which describes how much strain energy is released per unit fracture surface area. Abaqus can calculate such outcomes for a crack, which can then be compared to critical values to determine whether or not a crack will propagate.
Hi Brian
Thanks to answer, But I want to see crack propagation, i do not want to use XFEM method, contour integral method just shows me opened seam and crack will not propagate! what methods can i use to show propagation of crack?
thank you
If you wnt to propagate the crack withoput XFEM, the options are
cohesive elements/surfaces or node release or element removal.
Node release requires that you know the prop. direction beforehand, but is probably simplest to implement. The manual has a section on this that should be helpful.
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