General Mechanical

General Mechanical

Finding reliability or Probability of Failure using Ansys Design Xplorer

    • glfakatkar
      Subscriber

      As per paper at link below, we can use ansys design xplorer for finding reliability.


      https://www.sciencedirect.com/science/article/pii/S0167473005000159


      Iam not able to find reliabilty after getting response surface.


      Also the paper say that we can apply various distribution type to random input variable. However when I did some tutorial, there was only option to mention either continuous or discrete distribution and the upper bound and lower bound. There was no provision to mention distribution type. How can we give the type of distribution to random input variable.


       

    • peteroznewman
      Subscriber

      You have to define Failure, before you can calculate the Probability of Failure, Pf, and hence the reliability R = 1 - Pf.
      Say the requirement is the Deformation < 0.25 mm.  When the Deformation is > 0.25 mm that is a failure. Maybe nothing has broken when the deformation exceeds 0.25 mm, but if that was the definition of failure, then it counts as a failure. If you want to define failure as the fatigue life is < 100,000 cycles, then you can use that result. The point is that you have to define failure, ANSYS can't do that for you.


      I added a Six Sigma Analysis (SSA) to a Static Structural model that has four geometric input parameters.
      I see there is a full range of distributions to select from to apply to the input parameters.



      After I assigned a Uniform Distribution to four input parameters, SSA created a 25 run DOE to calculate the variation in the Total Deformation. Below is the results of that run in a CFD plot.



      This shows that 36% of the runs failed, with a Total Deformation > 0.25 mm so the reliability is 64%.


      Regards,


      Peter


       

    • glfakatkar
      Subscriber

      Thanks a lot sir for your reply. 


      Instead of SSA, I was trying to give input in response surface optimization. Option of probability distribution is available in SSA. With this, I am able to find the Reliability as well as probability of failure.



      But if I want to do response surface optimization, I don't have option to give type of distribution. Can you please explain this. 


       


      Regards,


      Ganesh

    • hquoc87
      Subscriber

      Hi Peter, 


      Thank you for your information. As you mentioned above that we can set the failure criteria for deformation (in your example, it was 0.25mm). Can you tell me more about where and how can I set up that criteria for deformation to run SSA? I'm really new to Ansys and learning it by myself so it's still a little bit hard to follow. Any information helps. Thank you so much!


      Regards,


      Hung.

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