hexagon logo
Register Sign in
  • State Not Answered
  • Replies 9 replies
  • Subscribers 11 subscribers
  • Views 95 views
  • Users 0 members are here
Options
Related

Adams acceleration magnitude

Josef K.
Hello,
 
I am simulating an experimental gearbox in Adams. When complaring the gearbox vibrations (accelerations) between the experimental measurements and the Adams requests, there is a huge difference in magnitudes. The units in Adams are in mm, but I always make sure to turn them into m so as to compare them to the experimental measurements. I am using the default Adams solver settings, except from the fact that I use multithreading as PREFERENCES/, NTHREADS = 4.
 
I have also read in the documentation that the I3 integrator (which is the default|) may not calculate the accelerations properly, but this great a difference in magnitude shouldn't be related to that.
 
Are there any other things I should look into that might help mitigate my problem?
 
P.S.
 
I am using flexible bodies (the gearbox included) in order to allow for some flexibility in the model.
 
Thanks,
 
Josef
Parents
  • 0
    There is a reason why SI2 takes so long time, it makes more accurate simulations.
    But back to I3 (or try HHT, particularly if there is contacts involved).
    1. Run a simulation with default values (in A/Car ERROR=0.01 and HMAX=output step).
    2. Decrease to ERROR = 0.001 (which is Adams default). Run with a new name.
    3. Plot some typical displacements: angle of a wheel or nodal displacement of you have flex parts.
    4. Continue decreasing ERROR until two consecutive runs have acceptable difference (here is where engineering judgement comes in). Then select the larger of those two values for error.
    5. Save that run (with the larger error), delete all other runs from the session (makes it easier to maintain.
    6. Set HMAX=output_step/10 and run a new run.
    7. Compare a typical acceleration between the two runs.
    8. Repeat until convergence.
    This is a procedure that we always used to teach new users back in the 90's (when I was responsible for trainings and support). But I guess this is not included in training material or documentation anymore.
     
Reply
  • 0
    There is a reason why SI2 takes so long time, it makes more accurate simulations.
    But back to I3 (or try HHT, particularly if there is contacts involved).
    1. Run a simulation with default values (in A/Car ERROR=0.01 and HMAX=output step).
    2. Decrease to ERROR = 0.001 (which is Adams default). Run with a new name.
    3. Plot some typical displacements: angle of a wheel or nodal displacement of you have flex parts.
    4. Continue decreasing ERROR until two consecutive runs have acceptable difference (here is where engineering judgement comes in). Then select the larger of those two values for error.
    5. Save that run (with the larger error), delete all other runs from the session (makes it easier to maintain.
    6. Set HMAX=output_step/10 and run a new run.
    7. Compare a typical acceleration between the two runs.
    8. Repeat until convergence.
    This is a procedure that we always used to teach new users back in the 90's (when I was responsible for trainings and support). But I guess this is not included in training material or documentation anymore.
     
Children
No Data
© 2025 Hexagon AB and/or its subsidiaries. Privacy Policy | Cloud Services Agreement