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  1. DRDearth

    Abaqus and progressive failure analysis on composite material plate|

    Has anyone had any experience using Abaqus with the Embedded elements feature? When beams are Embedded into Solid mesh models, I belived the beams distributed loads are not propertly being distributed into the nodes of the adjacent solids. In a more conventional FEM I would have had the Beams...
  2. DRDearth

    Am I conservative?

    For your composite anaysis I would check the strains in your panels as a benchmark. As a general rule-of-thumb I would keep strains below 0.005 in/in for composites. David R. Dearth, P.E. Applied Analysis & Technology
  3. DRDearth

    linear vs. non - linear analysis

    My input would be that before you charge off into a non-linear analysis I would investigate your linear approach. For example, if you feel a non-linear model is necessary due to high localized stresses, then search around for the magnitude of stresse/strain components in the local region...
  4. DRDearth

    Sizing Fuselage Frames using FEA Results

    Thanks for the note.. the questions I posted are really for the purposes of making ROM santiy checks of FEMs. In the actual case FEM of aircraft structures will react loading more complex than the simple case I outlined. David R. Dearth, P.E. Applied Analysis & Technology
  5. DRDearth

    Bending Moment for Sizing Fuselage Frame

    Also as an aside comment... a ROM estimate for the moment in the frame can be estimated from the differences in cap loads (Rods Axial Loads)X the height of the frame. M = (delta rod load lbs) X d (Depth of frame). This moment is balanced by the shear in the panel between the rods (q lbs/in) as M...
  6. DRDearth

    Bending Moment for Sizing Fuselage Frame

    Thanks for the commments.. the approach I was outlining is from the "old school" of FEM models. The "rod & membrane" approach was about all that could be done back then. Today's contemporay FEA programs allow for more realistic approachs. But the questions I posted still come up from time to...
  7. DRDearth

    Bending Moment for Sizing Fuselage Frame

    I posted this same Question on the FEA Forum. I'll repeat it here to see if any Bites. I've run acoss a number of engineers questioning how to use results from FEA models to Size Fuselage frames for bending moment. I've always thought one typically takes Shear loading in the frame between...
  8. DRDearth

    Sizing Fuselage Frames using FEA Results

    To All.. Thanks for the commments. Aircraft Fuselage frames are typically circular maybe a "Z" section. Usually the frame section is idealized using the Frame web modeled as a Membrane and the frame inner & outer caps are idealized as Rod elements. The bending moment in the Frame can be...
  9. DRDearth

    Sizing Fuselage Frames using FEA Results

    I've run acoss a number of engineers questioning how to use results from FEA models to Size Fuselage frames for bending moment. I've always thought one typically takes Shear loading in the frame between longerons (q lbs/inch) X distance between longerons (inch)==> this gives total shear force (V...
  10. DRDearth

    modal analysis/beam with loads

    I'm going to visit this site more often.. I've written several artiles regarding Dynamic Reponse problems. One such article is in Machine Design magazine "FEA Upate" column. This article includes a sample problem with detailed hand calcuations and a FEA problem for download. Send me a note and...
  11. DRDearth

    Rectangular Plate, large deflections

    The problem geometry you describe isn't relatively thin it's THIN. I would guess bending will become membrane tension under small loading. You would need a comprehensive non-linear with large deflection capability to model your problem. But, there are cookbook solutions to simple geometries one...
  12. DRDearth

    Use of spring elements

    If you are connecting spring elements to other elements you might have DOF instability problems with the interface. A simple 1D spring acts like a Truss and your model might "fall down". Other spring element types provide for maintaining stability in the model for other DOF's. Check your FEA...
  13. DRDearth

    Moment release(s) define

    Your post is complicated... I would guess your problems are related to the Beam local coordinate systems. Beams have their own coordiate system. X, Y & Z, or i, j & k.. depending on how you want to call it.. experiment using a few sample problems to make sure you are not mixing up your...
  14. DRDearth

    Stress Concentration Factor

    I would suggest investigating a few sample SCF problems with known solutions. The question of where to pick the location to define Nominal stress is always tricky... David R. Dearth, P.E. Applied Analysis & Technology
  15. DRDearth

    Abaqus, ANSYS, Algor, Mechanica which is the best?

    Regarding the better code. I have current copies of every commercially available FEA code on today's market, Algor, Ansys, Cosmos, DesignStar, CosmosWorks, Mechanica (old Rasna)... They all work and will all give solutions sufficient accurate for one to make an engineering decision on where to...
  16. DRDearth

    bolt connection restraints

    To All.. you are in luck... Check Machine Design magazine "FEA Update Column" I have a 3 part series on finding reactions to Bolts and Fasteners. Part I just came out in the Dec 9, 2004 issue of MD. Parts II & III come out in February and March. With the next 2 installments in this series...
  17. DRDearth

    boundary conditions in a 3D HVAC model due to thermal loading

    There are several ways to model the Expansion joints. One is to use contact/surface gap elements. Another way is to model nonlinear deflection material models, i.e. for a defined amount of strain (deflection) no load resistance, then after the defined deflection is obtained, kick in the...
  18. DRDearth

    Spline Loading

    Depending upon your loading distribution you should be able to define a load distribution (function) along the length of the spline. The function can either be linear or nonlinear. If you are using Nastran the loading will be applied to your spline length when the preprocessor writes out the...
  19. DRDearth

    8 nodes 24 DOF brick element stiffness formulation

    Shakildor, You might try the Nastran web site and look over the Nastran processor manual. David R. Dearth, P.E. Applied Analysis & Technology E-mail "AppliedAT@aol.com"
  20. DRDearth

    Fatigue curves

    Cavic, Seach for MIL-HDBK-5 on the internet. Or search material supplier sites. David Dearth Applied Analysis & Technology David R. Dearth, P.E. Applied Analysis & Technology E-mail "AppliedAT@aol.com"

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