Zero energy release rate obtained when crack open at right side

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  • Last Post 02 October 2018
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Sylvia posted this 28 September 2018

Hello,

I am trying to calculate J-integral and Energy release rate of an actual crack (not a crack growth model) by using ANSYS. Pre-Meshed cracked is the method I selected. However, for two same length crack, but just open in different direction, ANSYS gave me a total different result of G ( energy release rate).

Condition set: fixed support at bottom and 1 micrometer y direction displacement at top

1. Crack open at left side

Total deformation as following:

crack open at left deformation

And I got J-integral = 66.19 and G total = 64.233

2.  Crack open at right side

Total deformation as following:

crack open at right side deformation

And I got J-integral = - 66.188 and G total = 0

Why changing crack open direction will lead to a zero energy release rate result? Please help me if you met similar situation before and know how to solve it.

Thanks a lot!

Sylvia

crack energy-release-rate
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SandeepMedikonda posted this 29 September 2018

Hi Sylvia,

  How are you calculating the G (Should be completely from Mode 1, i.e., G1)? Are you using the Fracture Tool?

  See if you can replicate this for the Fracture Example given in the manual?

Regards,
Sandeep
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SandeepMedikonda posted this 02 October 2018

Hi Sylvia,

  I was looking at a similar problem, please check the crack orientation coordinate system.  Maybe the crack direction is defined incorrectly?

Regards,
Sandeep
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Sylvia posted this 02 October 2018

Hi Sandeep,

You are right. I have reviewed the example given in the manual, and then tried many tests. I find out that if crack open in the right side, to avoid zero G value, I cannot set coordinate system at crack tip. If crack open in the left side, I can set coordinate system at crack tip...I still don't understand why. But finally I fixed my problem. 

I do appropriate your help!

Regards,

Sylvia

SandeepMedikonda posted this 02 October 2018

Hi Sylvia,

  Have you tried transforming the co-ordinate system?

The x-direction has to be normal to the crack growth, so try making those changes and see?

Regards,
Sandeep
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Sylvia posted this 02 October 2018

Sandeep,

 

My problem is in 2D, so I correct my coordinate system as following:

Then I obtain J=64.502 and G total=64.538 for the right side opening crack. These results are reasonable.

 

Thanks,

Sylvia

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