2-D Pre-Meshed Crack in the middle, different values of J-Integral and G total for the crack

- November 20, 2018 at 9:00 pm
  
  Sylvia
  Subscriber
  
  Hello,
  
  I made a 2-D crack simulation for thermal barrier coating, but I didn't know the accuracy of my results. Could anyone help? I will list my major steps in the following. The crack is located in the middle of the model.
  
  There are many 2-D Pre-Meshed Crack tutorial online, but none of them sets the crack in the middle. So it's hard for me to check the accuracy of my simulation results, especially the G (Strain Energy Release Rate) value I obtained for the case is not similar to the J-Integral value.
  
  1. Following is the 2-D model. The crack and the coordinate system is set as shown in picture.
  
  2. Two ends of the crack are set as crack tips in "Pre-Meshed Crack"
  
  3. Then I obtained results of J-Integral and G total:
  
  G=10.158
  
  J=4932.8
  
  In the theory, these two values should be similar to each other. I made the simulation for side open crack also, which did have similar values of G and J. So I am so confused that why the crack in the middle will have such different results.
  
  If you did similar research, please help me! I will do appropriate it.
  
  Thanks,
  
  Sylvia
- November 20, 2018 at 11:07 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  Sylvia,
  
  How are you defining the crack tip? Are you picking just one end node of it or are you picking both the ends? Because if you are picking both the ends then I wouldn't expect it to give you correct results.
  
  Interior cracks are challenging, Try selecting the entire crack nodes and see if that might help?
  
  Also, can you specify which value is correct and which isn't?
  
  Regards,
  Sandeep
- November 26, 2018 at 1:32 pm
  
  Sylvia
  Subscriber
  
  Hi Sandeep,
  
  I picked both the ends. Why do you think it's hard to calculate interior cracks? Do you have any interior sample?
  
  thanks,
  
  Sylvia
- November 27, 2018 at 1:05 am
  
  Sandeep Medikonda
  Ansys Employee
  
  A crack is characterized by its shape, crack front/tip, crack discontinuity plane, crack normal, and crack direction. A crack front is represented by a crack tip in a two dimensional analyses. So when we specify 2 crack tips, I think this confuses the code.
  
  Regards,
  Sandeep
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