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  1. rob768

    converting units in Femap

    Hi, i have made a forced frequency calculation over a range of frequencies, resulting in results at each frequency step. My results are vibrations speeds in m/s (model is in SI units). is it possible to convert the results of each step from m/s to mm/s?
  2. rob768

    Center of Pressure for a pressure distribution on a curved Surface

    True. I misread the part about the varying pressure distribution.
  3. rob768

    guyan reduction

    Thanks, Karachun, this was helpful.
  4. rob768

    guyan reduction

    Guys, i want to experiment a little with guyan reduction in a dynamic calculation. So far, I never found the need for it but as models are getting bigger and bigger I want to see if it is advantageous to use without losing accuracy or results. I have a model of a ship, and i want to do both a...
  5. rob768

    Center of Pressure for a pressure distribution on a curved Surface

    if the model is a single surface, and assuming the pressure is uniform, isn't the center of the pressure at the center point of the surface? which can be found using the section properties of the surface?
  6. rob768

    Hi guys, I need some help (yet agai

    Thanks, I'll give it a try.
  7. rob768

    Hi guys, I need some help (yet agai

    Hi guys, I need some help (yet again). i have an output set which contains the results of a forced frequency response calculation, spanning from 5 to 60 Hz, in 0,5 Hz steps. The calculation is performed in SI units, which results in vibration velocities in m/s. As the calculated values are low...
  8. rob768

    Hi all, I need some help. I have a

    Hello Justine, Thanks for the link. I tried this, but i think the different frequency ranges cause problems.
  9. rob768

    Hi all, I need some help. I have a

    Hello Justine, no, the other way around. I have 5 sets of results for individual sources (blade pressure excitation, unbalance, engine foundation forces etc). The are calculated for different frequency ranges, and i want to sum all those sets into a single output set. The easiest way is to...
  10. rob768

    Hi all, I need some help. I have a

    Hi all, I need some help. I have a ship's model and performed some calculation with known excitation sources. For each source, I used a different load case. the aim is to calculate responses at several locations as velocity. I want to combine all loads to a single output files. Can someone...
  11. rob768

    results coyping

    Hello all, i have question regarding a calculation i performed. I did a calculation on the bolted flange connection, using 1/16th of the complete geometry (the flange has 16 bolt holes). I used symmetry and so far, so good, but i want to present the results for a full flange. I can easily copy...
  12. rob768

    Bolt preload followed by pressure load

    The calculation is lineair. But i wanted it done in the right order. Preload first, with related lengthening of the bolt and compression of the structure, then pressure load. Apparantely NAstran does that automatically.
  13. rob768

    Bolt preload followed by pressure load

    I thought i needed a restart, because i wanted to add pressure AFTER applying preload. I now understand that, in a combined load case using bolt preload, The effect of preloading is calculated first, after which any other load is applied. So, i can simply use a single loadcase. Happy days.
  14. rob768

    Bolt preload followed by pressure load

    Bolt preload is a simple command in Femap, and the pressure load is a given design pressure. Working in the time domain isn't possible, because the combination non-linear and contact surfaces is not supported. I'm trying to figure out how the restart function might help me, but I can't get...
  15. rob768

    Bolt preload followed by pressure load

    Hi there, I'm stuck in a Femap model. I modelled a section of a connection of two flanges, connected to each other by a pre-loaded bolt. Symmetry is applied to simulate a full model. In the pre-loaded model, i want to apply an internal pressure load. I tried to do this with a restart command...
  16. rob768

    Question on gear failure

    Hello All, i'm examining a failed gear (pinion-wheel, straight teeth) in which the pinion lost a few tooth due to fatigue, starting from one side of the teeth. There is also a pattern screaming misalignment, but this pattern is present on both flanks, and in both cases on the side of the...
  17. rob768

    Frequency from diesel engine

    a four stroke diesel engine generates frequencies at 0.5x operating speed and multiples (1, 1½, 2, etc)
  18. rob768

    Natural frequency of two different materials in one system

    If i understand well, when they are moulded together, it is one stiffness, and one mass, it won't behave as two different systems.
  19. rob768

    Medium and large engine blocks and crank cases?

    The very few times such a failure occurs doesn't weigh up to the costs of a welded crankcase compared to a cast-iron one. Yes, from a perspective of having to replace a complete engine, for which often a hole has to be cut in the hull and much more, a repairable engine makes more sense. But...
  20. rob768

    new motor getting overheating

    Slipping caused by an UNLOADED bearing can be an issue to. Make sure the bearing carries sufficient load.

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