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

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• Last Post 27 November 2018
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Sylvia posted this 20 November 2018

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

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SandeepMedikonda posted this 20 November 2018

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

Sylvia posted this 26 November 2018

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

SandeepMedikonda posted this 27 November 2018

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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