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  1. Ionut Cosmin

    How to determine the environmental loads for a CubeSat based on the launcher?

    Hi everyone, I am trying to understand how to properly evaluate the environmental loads (accelerations, lateral and axial frequency limit, sine vibration profile, random vibration profile, shock, etc) that will need to be used in the structural analysis and validation of a CubeSat based on a...
  2. Ionut Cosmin

    How to derive the first natural frequency requirement of a subassembly?

    Hello all, I am trying to determine what should be the first eigen mode frequency for a subassembly if the requirement is known for the assembly. For example, let' say I have a robotic arm which has a requirement that the first natural freq should be higher than 70 Hz. On this arm I have an...
  3. Ionut Cosmin

    Venting analysis on satellite payload/electronic box

    The pressure profile in the payload compartment/fairing is the one from Ariane 6 launcher [https://www.arianespace.com/wp-content/uploads/2021/03/Mua-6_Issue-2_Revision-0_March-2021.pdf] chapter 3.2.8. I tried to find a previous analysis report but I could not find anything. I think I will do...
  4. Ionut Cosmin

    Venting analysis on satellite payload/electronic box

    Yeah, I don't really worry about the overpressure in the box, I'm sure that it is pretty "leaky" and it will dump the air pretty quick; but I still need to do a venting analysis to include it in the report as a requirement from the client.
  5. Ionut Cosmin

    Venting analysis on satellite payload/electronic box

    Hello everyone, I have to do a venting analysis on an electronic box that will go into space. My question is if anyone has ever performed such an analysis and can give me some guidelines? I am wondering if there are any formulas that I can use and check the dimensions of the venting holes. I...
  6. Ionut Cosmin

    Strain gauge position based on FEM?

    Hi all, I am trying to determine the best position for strain gauges on a milled aluminum aviation part that will be tested. I am checking the max principal strains in the FE model and I am wondering if there are any rules, guidelines, or best practices when looking over the FEA and determining...
  7. Ionut Cosmin

    Optimize spring damper stiffness and damping coefficient

    I have tried what you have mentioned @newbie_user. My only problem is that the optimization [abs (SPRING_1_MEA) -10] is not reaching 0 when minimizing the results, sometimes it reaches negative values. Overall the values are close to 0, something like 2.35 or -1.5, but I want to find the values...
  8. Ionut Cosmin

    Can you specify spring stiffness and damping as a curve instead of a single value ?

    Yes, now it works, I could not understand the independent variables at first but I have managed to sort it out. I created a measuring function with the following syntax: AKISPL(ABS( .damper_simplu.SPRING_1.deformation),.damper_simplu.SPRING_1.force ,SplineForce, 0) and now the simulation works...
  9. Ionut Cosmin

    Can you specify spring stiffness and damping as a curve instead of a single value ?

    Hi Greg, Yes, I am using View. I have tried using what you have mentioned, although I used AKIMA_SPLINE (because I cannot find AKISPLINE in the options, I am using MSC ADAMS 2014), but I get the following error: I don't think the K coefficient accepts multiple values. Thanks, Cosmin
  10. Ionut Cosmin

    Can you specify spring stiffness and damping as a curve instead of a single value ?

    I am wondering if it is possible to specify the stiffness and damping coefficients as curves ? I have a gas damper in real life on which the compression force depends on the velocity of the piston rod, so my values for stiffness and damping are variable. Can I model this with a translational...
  11. Ionut Cosmin

    Optimize spring damper stiffness and damping coefficient

    Hello, I am trying to simulate an impact between a spring damper attached to a body and the ground. I have attached an image to better understand . As you can see, a spring damper is attached with 2 bodies, one with a bigger mass and one with null mass (used only for contact purpose). As you...
  12. Ionut Cosmin

    PARAM, INREL, -2 with RIGID=LAGRAN problem ?

    Hi all, I am trying to run an analysis of a satellite which involves a thermal load (temp on each node). The model contains multiple RBE2 and CONM2 to simulate the connection of equipment mass to the structure. I am using a CTE for each RBE2 and also RIGID=LAGRAN, as stated in the nastran docs...
  13. Ionut Cosmin

    Problem with .dat output with Dytran preference ?

    Ok, so I figured it out. I moved my db in the bin location of my Patran installation path, where the p3dytran executable (that does the conversion to dat file) exists and it seems to give me the correct dat output file. It seems to be a problem with the Environmental Variables (form what I have...
  14. Ionut Cosmin

    Problem with .dat output with Dytran preference ?

    Hi all, I am having some problems with Patran. I have loaded the Dytran Analysis preference with the load_mscdytran() command, I have created the model and when I want to run an Analysis (with Translate option, not a Full Run), to create the .dat file, I don't get anything. The db closes for a...
  15. Ionut Cosmin

    Structural analysis of a rocket ?

    WKTaylor Thank you for the references, I already found some that were useful.
  16. Ionut Cosmin

    Structural analysis of a rocket ?

    3DDave thanks for the suggestion, I will look into it. SparWeb Great insight, thank you ! Yes, SpaceX is really changing the game, it would be nice to investigate those "post-launch" loads but I guess you have to work there to have access to it :) tbuelna Wow, first of all, awesome job man ! I...
  17. Ionut Cosmin

    Structural analysis of a rocket ?

    Hello everyone, I am curious to know if anyone knows what are the steps performed in the structural analysis of a rocket ? What are the most important parts and what type of analysis are performed on them ? If anyone has worked on building rockets for NASA or other space agency, maybe they...
  18. Ionut Cosmin

    Questions about a finite element modeling situation ?

    NRP99 Yes, if I reduce my E by 84% I will get the same results in frequency. Is it correct to reduce it so much ?
  19. Ionut Cosmin

    Questions about a finite element modeling situation ?

    Okay guys I have run some simulations on a single beam modeled with solid elements, shell elements on outer layer and shell elements on mid-plane. The models can be seen here. The beams are blocked in translation at one end and a mass (CONM2 property) was tied using RBE2 at the other end. I...
  20. Ionut Cosmin

    Questions about a finite element modeling situation ?

    rb1957 Yes the red is the zone with the overlap. Yes the elements are finely meshed on the corners

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