Learning Forum

[Zander Fut]

Hi,

I am new to Ansys and trying to simulate a fatigue crack growth of a semi-elliptical crack in the inside surface of the pipeline segment using the SMART Crack Growth tool. I have already conducted some analyses using static growth option but having some problems with fatigue option.

First of all, when trying to select material for the body in the SMART Crack Growth tool, it just stays yellow (see picture), indicating the material was not assigned. Is there a specific way I should select the body or is there something I’m missing here?

What about the load, should I be using tabular load since the pressure inside the pipe is fluctuating or how this is taken into account when using fatigue option?

Also, let's say I would like to incorporate a medium such as hydrogen into the simulation to see how it affects the fatigue crack growth rate, is the multiphysics simulation with Ansys Fluent the right way to proceed?

Any other tips related to fatigue crack analysis are also welcome.

Thank you.

 

[danielshaw]

If the material is probably highlighted in yellow because all the required material properties are not defined.  For example, if the Paris crack growth law is specified you need to define the coefficient and constant for Paris's law in Engineering Data.

The crack growth is based on the specified crack growth law (probably Paris).  See Section 3.1 in the MAPDL Fracture Guide.

I am not sure what you mean with the last question.  Do you want to link to a coupled-field solution to obtain the loading or the effect of the medium on the fracture behavior (e.g., SCC).  You can obtain the loading from coupled-filed solution.  To account for the effect of the medium on the crack growth behavior, you probably need to use an user defined tabular crack growth law (see Section 3.1.3.4 in the MAPDL Fracture Guide).

 

 

 

 

 

 

 

 

 

[Zander Fut]

Thank you for the answer, that actually answered my questions perfectly. I mistakenly thought that all the necessary material properties were defined for the predefined materials. Also references to the Fracture Guide were helpful, I think I'll be able to proceed with that.