Dear colleagues, I´m working with smeared crack models for brittle materials.
The fracture energy is an input parameter for a nonlinear analysis by the finite element method. Nevertheless, I dont´know how I can get the fracture energy because the material constitutive equation has no softening curve post-peak.
I suppose in this case the value for the fracture energy is infinity, ie, too large. Could anyone help me on this?
you have no fracture energy if you don't include any nonlinear path in the constitutive model
Why infinity? Look at some test results. You have some limit "deformation or crack opening". Which software do you use? I have used smeared crack model in Ansys and the fracture energie was not a input.
thanks to answered the question Peter and Vincenzo. Sorry, I made a mistake. The fracture energy is infinity only for perfect elasto-plastic material. Indeed, if I have no nonlinear path post´peak the Fracture energy is zero. In this case, I will try a value very close zero because i don´t know What happens if I put zero as a input parameter on the software. I have used DIANA and there are some softening curves to fit the material constitutive model. the fracture energy for an exponencial curve is a necessary input on TNO DIANA.
Dear Marcelo. You can define a brittle material in DIANA with the pre-defined smeared crack BRITTL model (see https://support.tnodiana.com/manuals/d94/Diana.html). It has no tensile tail, so it does not require an input of the fracture energy, although depending on the problem, the convergence might be quite tricky.
The problem is that if you want to model a brittle material by the smeared crack model you must have a nonlinear path with fracture energy. On the contrary if you model the material up to the elastic peak you cannot reproduce the fragility, but only the elastic phase.
Thomas you are correct. I saw that. What happens is that I ´m working with an anisotropic model for mansory (rankine-hill). The fracture energy is an obligatory input in two directions X e Y. Maybe, it´s a good idea change the actual model to a smeared crack model with no tensile tail.
Yes Vincenzo. I cannot reproduce post-peak behavior but the material (masonry) that I´m analysing has no tensile tail. this way, as I wrote to thomas, I will try another constitutive model even I know the masonry anisotropic behavior.
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