Yes, there are formulas for estimating thermal contact conductance based on clamp pressure, joint member material(s), and surface roughness. A few different methodologies exist, but they largely come to the same values. There is some empirical backing for specific joint types which are more...
@rb - Currently no. I requested we put some sort of material at the interfaces which could fill that purpose, just to make the joint performance easier to predict if nothing else. This was shot down due to "assembly complexity concerns"... I have not given up on that route though.
@SW -...
Having an interstitial fluid (or gas) to "fill in" the microscopic imperfections helps aid the conduction. We're not talking about a gap between plates here where convection would take place, but conduction through the fluid. I can assure you that relative to NO fluid (i.e. in a perfect vacuum)...
Conduction across an interface is highly dependent on the clamping pressure. Particularly in a vacuum where there is no interstitial fluid between the clamped plates to aid conduction. Estimating the contact pressure and area is relatively straight forward with a bolted joint since you can...
I'm trying to work through a thought experiment with a colleague about how to estimate the heat transfer across a riveted joint. The application will be in a vacuum, so there's no interstitial fluid between the joined members to help with conduction. Thus you are highly reliant on surface finish...
I'm trying to work through a thought experiment with a colleague about how to estimate the heat transfer across a riveted joint. The application will be in a vacuum, so there's no interstitial fluid between the joined members to help with conduction. Thus you are highly reliant on surface finish...
I have been looking at a high-performance thermal pad to use on the heatsinks for several high power dissipation components. The thermal pad is relatively stiff and requires a certain level of compression in order to achieve good levels of thermal conductivity though. I'm concerned that the...
For starting I context, I have a FEM with 2 primary submodels that are broken out into separate include files. Each of the two parts runs without issue on their own (free-free modes, fixed modes, and random vibe cases). When running together the two parts are connected by a ring of CBEAMS...
I was overthinking it. It really just boils down to F = m*a since you want the CG's response. So use a CBUSH to recover the input force, and divide that by the total mass to get your net acceleration.
The issue with doing the RBE3 route is you would need to make sure each independent node's...
I am creating some vibration test specifications for a customer and using the methodology described on https://femci.gsfc.nasa.gov/random/randomtestspec.html. I’ve been using the FEMCI “book” as a resource for my work in the aerospace industry for years, and found that many consider it in itself...
I don't need a concentrated mass because all the mass is accounted for in the FEM itself. I just want to track the response of the spacecraft CG for notching/force limiting purposes for vibration testing predictions. There are design load factors we do not want to exceed on the overall...
I want to track the accelerations for the CG of my spacecraft from frequency response analysis runs. This is is obviously not a physical point in the FEM though. I'm thinking an MPC of some sort is the approach to use, but unsure of the most accurate way to implement it. The simplest (as far as...
I have encountered an odd issue while doing geometry prep using some of the cleanup and editing features in the meshing toolbox. Part way through creating my model I suddenly cannot select anything when using options from the Feature Removal or Geometry Editing sections. For example I want to...
For an SNP environment, is parallel processing used by default if multiple cores are available? If 'yes', what is the default maximum number of cores used?
If 'no', is it appropriate to put the parallel=p execution keyword in your config file if you have a typical number of cores you would...
thread561-357474
This was a very useful discussion, but unfortunately (as is the nature of all things centered around computing technology) I think most if not all of the conclusions are now out of date. For example I believe the ILP-64 solver is now the default in newer versions of Nastran...
I have a model which has a significant number of high frequency modes >300Hz. For example between 300Hz and 500Hz there are almost 160 modes alone. My excitation environments run out to 2000Hz, however. The runs are taking an inordinate amount of time as a result unless I only include a subset...
My config file has "buffpool = 20.0X" (similar for smem). What does that result in relative to my physical memory or max memory allocation? And what is your rule of thumb for "reasonable" here? Was 4GB a general recommendation, or based on the previous user's total memory? FYI I'm running NX...
I'm trying to run a dynamic reduction within FEMAP, but am having issues getting it to produce the expected output files. My goal is to get mass, stiffness, and damping matrices as well as data recovery matrices (ATM and LTM) all in OP4 format. When I run the analysis within FEMAP it completes...
Thanks for the quick replies.
@davefitz
Agreed 100% that some EDU will need to be built, and significant testing done at both proto-type and flight model level. At this stage my goal is primarily to determine if the approach we are pursuing is even feasible/realistic. At which point we will...
