General Mechanical

General Mechanical

Zero energy release rate obtained when crack open at right side

    • Sylvia
      Subscriber

      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

    • Sandeep Medikonda
      Ansys Employee

      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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    • Sandeep Medikonda
      Ansys Employee

      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
      Subscriber

      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

    • Sandeep Medikonda
      Ansys Employee

      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
      Subscriber

      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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