1 (edited by radhikav0508 2018-11-05 03:56:05)

Topic: Stress intensity factor computation for mixed mode

I am modelling a simply supported beam with a crack at quarter span and load at mid span. I want to determine the stress intensity factors KI and KII and the strain energy release rate GI and GII seperately for mode I and mode II as the crack propagates. Is it possible to do this?

Re: Stress intensity factor computation for mixed mode

Dear radhikav0508,
please note ATENA does NOT use the linear fracture mechanics approach (with stress intensity factors) to represent crack initiation and development - see ATENA Theory, 2.1.4 Fracture Process, Crack Width and 2.2.3 Rankine-Fracturing Model for Concrete Cracking for more information). The main reason behind this decision is the scale difference in the fracture process zone size between metals and heterogeneous quasi-brittle materials like concrete.
If you for some reason (please explain?) wish to compare the 2 approaches and for that purpose need to find/invent some method of relating the material status variables of the 2 models, please let us know more about your planned targets (questions to be answered by such a comparison), and we can try to help you.

Regards.

Re: Stress intensity factor computation for mixed mode

Thank you for the immediate reply.

I am working on mixed mode fracture of concrete beams.  I need a method to separate the quantity of energy dissipated/ energy release rate in mode I and mode II so as to compare the contribution of flexure and shear in crack propagation. Is that possible? Is there any other parameter defined in ATENA that can be used to evaluate contribution of these two modes separately?

Regards,
Radhika

Re: Stress intensity factor computation for mixed mode

Dear radhikav0508,
the crack model in ATENA is governed by the crack opening (which more or less corresponds to Mode I), based on Tensile Stfrength and Fracture Energy. Simply said, all the current the properties, including shear stiffness and strength, are controlled by the Crack Opening (the current and the maximal during the loading history so far).
Considering the above, I am afraid I do not see how you could get anything for your Modes Comparison.

I can only recommend you to look at the output attributes available - see the ATENA Studio User's Manual, 4.4 Output Data Attributes for more information on Crack Width, Maximal Fract Strain, Crack Attributes, Cracking Moduli, or, if you work with the SBETA material model (only available for 2D Plane Stress), Sbeta State Variables.

Regards.

Re: Stress intensity factor computation for mixed mode

Thank you. I will see what I can do with the output attributes.

Regards.
Radhika