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  1. bongirs

    Failure criterion for crack development of metals?

    Hello, I have seen that in a lot of industries, the failure criterion is unsigned von Mises stress. Sometimes it may refer to yield stress, sometimes ultimate stress depending upon the scenario simulated. My research peer suggested another approach that I never heard before. Use signed von...
  2. bongirs

    Convergence analysis of finite element analysis?

    IceBreakerSours, do you really go into that level of precision in your analyses (1+2 not equal 2+1)? I always believe that FEA is good tool for giving you insight and not really anywhere close to reality. The Gauss point extrapolation is also why I never use stress/strain for convergence...
  3. bongirs

    How many nodes/elements/DOFs do you work with?

    I disagree with the argument that CAD software's should not have FEA modules. Although I am not an expert in FEA, in my previous role as Product Development Engineer, I have extensively used Creo Simulate (FEA module in Creo) to solve a variety of design related problems. As a designer, it is...
  4. bongirs

    Convergence analysis of finite element analysis?

    Now I understand.... So you can choose stress as a parameter if you are checking local convergence and displacement if you are concerned about the whole body. I can also deduct that in a local region if the stress converges then displacement also has to (in that local region only) ? This is...
  5. bongirs

    Convergence analysis of finite element analysis?

    Brian, I see what you are saying but I don't understand what better approach you would suggest? Your argument about the Kt is correct, but as I said previously, the geometric point for displacement convergence is taken in an area experiencing almost the max stress. So that way even for the Kt...
  6. bongirs

    Is RADIOSS a bad solver?

    Hello, I am performing explicit dynamic non-linear contact analysis (drop test) and the results are quite off from physical testing. If however, the same parameters are used for solving with Abaqus then it is quite closer to reality. So I am just checking whether my findings are in line with...
  7. bongirs

    Convergence analysis of finite element analysis?

    Hello, 1. I have always done convergence analysis by checking the maximum stress for a scenario and seeing if it converges towards a value upon mesh refinement. However, my professor recommended a better method. He told me to choose a geometric point (x,y,x) and always have a node at this point...
  8. bongirs

    What is implicit and explicit analysis in FEA?

    If you are talking about solving the final system of simutaneous equations, then I know that computationally methods like Gauss Jordan are better than finding the inverse of co-efficient matrix, which is the part where I agree with you. However, I read that it necessary to find inverse of mass...
  9. bongirs

    What is implicit and explicit analysis in FEA?

    I found an answer in a presentation. Basically, implicit solver considers a linear transformation of acceleration between two time steps. This requires inversion of stiffness matrix for each step. Explicit assumes a constant acceleration between two time steps. This requires inversion of mass...
  10. bongirs

    What is implicit and explicit analysis in FEA?

    I am using RADIOSS and the documentation is incompetent to say the least. I can check the Abaqus documentation as my university has licenses for all major FEA software's.
  11. bongirs

    What is implicit and explicit analysis in FEA?

    Thomas, I am a graduate student whose research project is a drop test simulation using RADIOSS. As I am seeking full time position, I was asked this question in an interview and I could not answer it.
  12. bongirs

    What is implicit and explicit analysis in FEA?

    Firstly, Thank you very much for such a descriptive reply! It surely helps resolve some of my doubts. However, it raises even more questions than it answers :). Anyway, I do not want to take a lot of your time, I guess you need to have a PhD to understand the complexity of FEM/numerical...
  13. bongirs

    What is implicit and explicit analysis in FEA?

    Thank you for your response btrueblood! Somehow Google never showed me that Wiki page. It explains the difference between these 2 methods with clear understanding. The given example also helps clear this distinction. But the distinction makes sense when you are solving a problem for which you...
  14. bongirs

    What is implicit and explicit analysis in FEA?

    Thank you for your elaborate explanation IceBreakerSours! I have a few follow up questions: 1. "Partial differential equations can be solved by different methods" - I studied the direct stiffness method in school and never came across any differential equations in it. So do all FEM have partial...
  15. bongirs

    What is implicit and explicit analysis in FEA?

    Hello, I am trying to understand what it means when a software says that it has an implicit solver as well as explicit solver. Often I find that people try explain the difference by using quasi-static vs time dependent analysis, but I know that that is not the correct answer. Additionally, how...
  16. bongirs

    FEA software developers guide/forum/book/community?

    Thank you, it is quite expensive though.
  17. bongirs

    FEA software developers guide/forum/book/community?

    Greg, it is always a pleasure to see your comments. Didn't quite get what you meant though. A tool is only as good as its user, if that's what you were suggesting. ;-) But jokes aside, can you give me any guidance?
  18. bongirs

    FEA software developers guide/forum/book/community?

    @aerostress82 Thank you for your valuable advice! I found the following 3 courses from University of Colorado at Boulder: 1. http://www.colorado.edu/engineering/CAS/courses.d/IFEM.d/Home.html 2. http://www.colorado.edu/engineering/cas/courses.d/NFEM.d/Home.html 3...
  19. bongirs

    FEA software developers guide/forum/book/community?

    Hello all, I am a Mechanical engineering graduate student with a couple of years of professional experience in FEA, as well as my research project is in FEA. It is my personal desire to develop a basic FEA software of my own. I have the software development skills, but do not know the...
  20. bongirs

    Element Stiffness Matrix Formulae for common elements?

    Thank you IDS! The index tells me that this is the book that I have been looking for.

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