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  • Users: hootrpootr
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  1. hootrpootr

    Using INCLUDE files to run two model configurations in one

    I'm fairly inexperienced with Nastran INCLUDE files, but I'm hoping I can use them for an analysis I'm running. Basically I have an assembly with various panels, brackets, fasteners, etc and I'm trying to set up my model so that it contains two configurations. Both configs will be set up in...
  2. hootrpootr

    Fastener joint modeling using single RBE2 instead of CBUSH w/ "spider" RBE2

    Hello, I have a question I was hoping you all could answer. A coworker sent me an FE model that he created, where he modeled a bolted joint using just an RBE2 element (with DOFs in 123) to connect the matching holes in 2 plates. I would never do this; my preferred modeling method would be to...
  3. hootrpootr

    Patran Results: Shell Force, Force Resultant - von Mises quantity vs. force magnitude?

    Hello, If the title is confusing, let me explain. I'm trying to extract loads from a Patran shell model in the x and y directions. I could just separately extract the x and y components of the shell forces, but I noticed there is a quantity called "von Mises". I know that von Mises stress is a...
  4. hootrpootr

    Help with sizing of lug attachment flange

    Hello, Apologies for the crude drawing attached, but here goes. Given Fx, Fy, and Fz loads applied at the lug hole, I've distributed the loading into each of the 6 fasteners to size them. I've also sized the lug itself using the airforce lug sizing method. But now I'm trying to size the...
  5. hootrpootr

    Ansys Norton creep power law constants?

    Hello, I’m trying to learn creep analysis in Ansys, and am currently working on deriving creep constants, specifically C1, C2, and C3 for the Norton Power Law. I understand that the equation is usually shown in 2 ways: epsdot = A * (sigma^n) * (t^m) or epsdot = A * (sigma^n) * exp(-Q/RT)...
  6. hootrpootr

    High cycle fatigue analysis: Performed fully in FEM or partly in FEM and partly in Excel?

    I’m trying to wrap my head around different ways of analyzing a components high cycle fatigue life, since I’m now just learning that FEM software is (supposedly) able to perform fatigue analyses, given I set up the model correctly. At my company, the method I was taught was to run two static...
  7. hootrpootr

    3D Bolt Load Distribution Spread Sheet

    Hello all, I'm creating a 3D bolt load distribution spreadsheet that accepts loads in 3 directions and distributes them into a 3 dimensional pattern of bolts (so the pattern does not have to be on a single plane). I'm honestly lost as to why the spreadsheet isn't working. I found this windows...
  8. hootrpootr

    Stress Concentration: Hole in infinite thin plate loaded in biaxial tension vs biaxial compression

    Hello, Is there a difference in the stress concentration of a hole in an infinite thin plate loaded in biaxial tension vs biaxial compression? I ask because in numerous books (one of them in the screenshot below), there is a calculation that determines the Kt in biaxial tension. I've also...
  9. hootrpootr

    Import Nastran .pch file that contains DMIG information (stiffness matrix?)?

    First of all, I’d like to apologize for any misleading information or confusion I may cause, as this is a topic I’m very unfamiliar with. Basically, a customer provided me with a set of files with which to create and run a model using Patran with Nastran. All of the files except one make...
  10. hootrpootr

    Is AUTOSPC the same as “Automatic constraints”?

    The title seems pretty self explanatory, but the automatic constraints check box is located in “solution type” —> “solution parameters”. And if I wanted to enable AUTOSPC through the .bdf, would that just be going to the PARAM section and adding a line for “PARAM AUTOSPC YES”? I can’t seem to...
  11. hootrpootr

    Moment/stress caused by the bending of bushing flange

    Hello, I'm checking the bending of a bushing flange, where a high axial force (along axis of bushing) is essentially pulling the bushing through a hole and causing the flange to "kick up". How would I determine the moment and stress caused by the load? I'm thinking, what if I convert the...
  12. hootrpootr

    Single shear bolt shear and moment diagrams

    Hello, I’m trying to determine what the shear and moment diagrams of a bolt in single shear look like. Before anyone says it, I know that it’s rare that a bolt will ever fail first in bending, and this is something that typically isn’t even checked for. Anyway, I’ve assumed that the bolt is...
  13. hootrpootr

    Is my understanding of “load case consistent” correct?

    I’m a (mostly junior) stress engineer and have been tasked with sizing a lug. Various loadcases have been run through FEM and loads have been distributed into the lug bolt for each. In other words, each loadcase has its own set of x, y, and z loads at the bolt. An initial analysis...
  14. hootrpootr

    Determine compressive modulus from compressive test?

    Hello, Is it possible to determine the compressive modulus of a polyethylene foam using the following spec sheet? https://www.sekisuivoltek.com/wp-content/uploads/2016/03/Minicel_ProductSheet_Type_M_Data.pdf It doesn’t contain any information regarding the compressive modulus, but does have...
  15. hootrpootr

    Can a block or thick plate be idealized as an axial spring?

    Hello, I want to drop a heavy mass onto a "pad", or thick plate (potentially even a block if the thickness is great enough). I am trying to determine an effective axial stiffness with which to apply to the pad. I know that for a rod for example, the stiffness could be worked out to be k = EA/L...
  16. hootrpootr

    “G’s” subjected to spring-mass system when dropped

    Hello, I have an interesting spring energy problem that I’m trying to solve. I have a spring (known k) attached to a releasable hook at the top and a mass (known m) attaches to the bottom. This is a drop test, so when the releasable hook detaches, the spring and mass fall together a set...
  17. hootrpootr

    RBE2 to Solid Hex Element Rotational transfer (Patran/Nastran)

    Hello, Any help is appreciated with this analysis of mine. I’m trying to model a lap shear joint test, where two plates are bonded together with an adhesive and sheared apart with an in plane load. I’ve modeled the plates as solid elements (Hex8). The bond has been modeled following the...

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