Thanks for the thoughts. I will think on it. The penetrating plate elements (2nd example from top) seem to do an ok job of showing ballpark stresses. Perhaps we can use the results of FEMs built like this to point us to locations where we need to perform classical calculations.
I'm sorry, let me upload better pictures. The cantilevered beams are made of plates, the foundation cubes are solids. I had toggled "view thickness" in FEMAP, which makes the plates look like solids. Note that I have removed 3 solid elements from the second example (penetrating skins) to show...
The tet example on the bottom of image 1 is using tet10s. The other examples use hexes (8 node bricks) for the foundation cube, because connecting plates to hexes is what I'm most interested in.
I'm not sure which glowing points you're referring to. The only nodes constrained are the "wall" at...
My specific question pertained to "skinning" solid elements, a common method of connecting shells and solids to constrain all 6 DOFs (solids do not constrain moments/rotations). Skinning is performed by creating plates on top of solids to "skin" them, thereby using the plate that shares nodes on...
I am somewhat new to using skin elements to account for moments at the junction between plates and solids, but I believe I'm doing it correctly. Yet the stress distributions I see have stark discontinuities and are nothing like what I would expect in the real world. My intuition is confirmed...
Hi all, thanks for your comments, I've spent time reading up on your pointers. Very useful.
@SWComposites, you say that modal testing tells you nothing about strength, can you explain that a bit? My thinking is that if you've got the stiffness correct, as exhibited by matching the first 5...
Our current outsourced FEMs are sufficiently accurate. They vary by approx. +/- 7-10% for first modes. I'd like to produce in-house models that nail all the primary and most of the secondary modes to within just a few percent.
We don't have the capital for our own vibration testing lab at this...
Hi All,
I lead a mechanical team at a growing aerospace company building small satellites up to 500 kg. I've been tasked with bringing structural analysis in-house to rely less on outside contractors. I intend to accomplish this through a mix of training and hiring, but I am concerned about...
Yeah it seems to be a bit of a nightmare! Unfortunately I've built a FEM in US common so have to stick with it to see the last step of the analysis campaign (thermal stresses) through.
The conductivity checks out as BTU/in-sec-F. The specific heat only checks out as BTU/lb-F if I multiply by...
Hi All,
When I load materials from the built-in FEMAP database "mat_eng_in-lbf-psi-degF-BTU.esp" for a thermal analysis, the conductivity and specific heat values don't make sense to me. I must be missing conversion units somewhere but for the life of me can't figure it out. I am using...
Great perspectives, all. Rputvin's comments made me think die-cut cardboard may be better packaging for our product all around (cheaper, less waste).
For the stuff that absolutely requires foam I'll look into local waterjet outfits.
Again, thank you all for your input.
Thanks for the suggestion! Unfortunately appearance is pretty important. I'll need to deliver with this level of quality: https://www.innerspacecases.com/
I run a small business on the side that sells motorized astrophotography mounts. Cutting our product's packaging foam by hand is a pain (and quality is inconsistent between techs), but ordering custom cut foam is too expensive. I'm a mechanical engineer by day and have broad (albeit mostly...
Thanks tugboat for the tip on the spring clamps, I have to admit that was a blind spot.
Thank you all for your responses, there is a wealth of useful information here. I should really come here more often.
SS and copper are in the design space, but we need a flexible connection to the detector. That would require a bellows of some kind, which introduces a break in the line and additional connectors that work against the requirement to minimize leak risk. Furthermore such bellows are ~$100/each...
Ah rb, I wish it stopped at impossible performance and budget demands. Did I mention they want it yesterday? Oh well, this is our lot.
Thank you tugboat for the perspective on buna-N and the EPDM recommendation. I'll look into EPDM options. This is for a 1/4" ID.
Happy to get into the details - 10 years, no leaks, no service are the requirements handed to me for the coolant assembly. Yes that's manager speak, in terms of probability at least 3 sigma odds of no leak across 10 years and 24 cameras (48 total lines for the cameras plus 16 more for cooling...
Hi all, I'm a mechanical engineer at a research institution building an array of spectrographs. I'm currently designing the coolant assembly and attempting to specify the coolant lines for a minimum of 10 yrs operation with no line maintenance. The other constraints and requirements are listed...
Does anyone know if it's possible to apply stress factors to only specific groups of elements in post?
I have an analysis of a structure that requires different stress factors to be applied to different regions of the structure. Each analysis run has 160+ load cases that all need these factors...
I agree, with both of you. Having the ability to do quick stress/deformation/thermal/frequency analyses of simple parts integrated into a CAD package is great to have. The problem comes when people mistake SW for a full-up analysis tool and attempt to predict the response of assemblies with...
