Learning Forum

[Chipman]

I am trying to simulate pre meshed crack propagation of turbine disk I created using solid edge. Crack is a v notch along surface of disk surface but it's not growing, but geometry simply deforms..your help will be greatly appreciated

[peteroznewman]

Chipman,

You ask about crack propagation, but I wonder how much you know about fracture mechanics? Some students know nothing about this topic, and expect ANSYS to make a crack propagate through a part as the load is increased and are disappointed to learn that is not possible in 18.2. 

What version of ANSYS are you using? 

In versions 18.2 and older, a pre-meshed crack could be defined and the fracture tool could be used to calculate fracture mechanics results such as KSIF, the Stress Intensity Factor, for a given crack length and applied stress. The maximum value of KSIF could be compared with the material fracture toughness to determine if the crack was above or below the critical condition where transition to fast fracture occurs. Calculation of KSIF to predict fast fracture doesn’t cause the crack geometry to move.

In version 19.0, ANSYS gained the ability to propagate a crack.

If you have not yet evaluated the crack for its fracture mechanics values, you should start there. If you have already done that, please upload a Workbench Project Archive .wbpz file so we can see your model.

If you are a beginner in fracture mechanics, here is the second video in a series that I have found to be helpful explaining some basics you should know before you use any tools in ANSYS.

https://www.youtube.com/watch?v=jJMSvgcZaGA

 

Regards,
Peter

[Chipman]

Peter,

 

Thanks this information was very helpful. I am new to fracture mechanics. I am currently using Ansys v19 and have attached the wpbz zip file for you to analyze further. Thanks for your help in advance.

[peteroznewman]

I don't see your archive. Here is the ANSYS 19 new feature...

[Chipman]

I have been using a the smart crack feature but the geometry simply deforms without crack growing. Any ideas why that would happen. I have tried to reattach the files and a picture of the results am getting. Thanks once again

[peteroznewman]

I had a first look at your model. There may be more than one reason why your crack does not grow. The first reason I found was that your mesher has defeatured away your crack.

Change Mesh Defeaturing from Yes to No.

While you are there, change your Element Order to linear.

Here is a video that you might find helpful.

https://youtu.be/QIeg4Yj-pEs

[Chipman]

Thanks a lot. I will make necessary changes. Will get back to you if I face any other challenges

[Chipman]

Hello Peter..Am thankful for the information you have me but the crack still won't grow.
Do you have any ideas on what else I can do to solve this problem?

[peteroznewman]

There are three things that will bring the model closer to growing the crack:

1) Make a longer crack in the geometry,

2) Increase the load on the structure,

3) Lower the fracture toughness on the material.

The first two will increase the KSIF of the crack, the third will lower the threshold when the crack will grow.