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  1. irq

    Polycarbonate simulation properties

    Hi, You will need at least the nonlinear stress-strain material data from the test. It is dependend on the application & loading scenario, whether you will need more data. I am quite sure that the typical values E & Poisson's Ratio are not sufficient to have the approximately correct results. irq
  2. irq

    Substructuring/Superelement and nonlinear analysis

    Hi, I recently had a discussion about FE static nonlinear model reduction and I would like to ask you for the state of the art methods concerning this matter. It is well known that the use of substructuring or sometimes called superelements can significantly save the development and...
  3. irq

    Interface Loads Analysis - % Error

    Hello group! today a question regarding interface loads deviation between different models & techniques, global & local models, hand calculation etc. It is well known if the different techniques and model discretizations will be used (especially the very coarse meshes, remember complete...
  4. irq

    25.603 in application for secondary structure

    Hello, The interpretation of the paragraph § 25.603 Materials regarding primary structure was discussed here: thread2-45169. What about secondary structure like interior: baggage compartments, wall panels, lining panels? Is there 25.603 especially point c) applicable? It says "take into account...
  5. irq

    Acoustic freeware software

    do you know any freeware or low-cost software for acoustic calculations? The field of interior acoustic and simulation of transmission loss are the main fields of our interest. Thank you for any tips.
  6. irq

    Quick replacement for CWELD element type

    If you can not use a CWELD I recommend to try a stiff element: RBE2 instead. At the moment I have the similar issue - I want to replace RBE2 and I am thinking about CWELD. The reason is that I see advantages in CWELD to connect two disimilar meshes without moving of the nodes to make proper...
  7. irq

    Material Variability Factor for Composites

    The joint is critical in proximity of the metalic fasteners and the connection fails obviously in composite plate, which confirms our prediction from a coupon tests (see above post). The joint is representative, original fitting & fasteners as installed in the component, identical production...
  8. irq

    Material Variability Factor for Composites

    Hi, After a long absence on this forum I want to continue this thread16-154238 There was a disscussion about taking into account a "material correction factor" to the ultimate test load value according to 25.307(d). This paragraph implies, that no additional correction factor must be included...
  9. irq

    MPC Explicit vs RBE2

    What is the difference between MPC Explicit constrained in DOF:1 (dependent); DOF:1 (independent) and rigid element RBE2 constrained in DOF:1 (dependent). RBE2's have 6DOF for independent node by default. Are both elements (=equations) interchangeable? [irq]
    • irq
    • Thread
    • Replies: 1
    • Forum: Nastran
  10. irq

    Sandwich skin - shear properties

    mmhaynes: ASTM C273 is the standard for determination of sandwich core shear properties. The "picture-frame" test is correct one for my application and determination of in-plane shear of skin properties, unfortunately not standardized until now. I am particularly interested how much the values...
  11. irq

    Eccentrically loaded joints

    Hello, Assume the fasteners subjected to eccentric load, where by theory the force on each fastener is proportional to it's distance from the centroid of the fastener group. For the joints, which carry no moment it is generally assumed that each fastener is equally loaded. In case of eccentric...
  12. irq

    Sandwich skin - shear properties

    How can I get this draft standard? Not much detail information is available regarding this test. Can I replace this test by another one e.g: 4-point bending test of the sandwich with facesheets positioned under 45 ̊, than estimate the failure stress on compression side and later on shear stress?
  13. irq

    Sandwich skin - shear properties

    The aim is to obtain the in-plane shear allowable of the thin sandwich skin. Please write me a short message (odzew [at] poczta [dot] fm) - I will provide you more details, as there is only way I can share more. Thanks.
  14. irq

    Sandwich skin - shear properties

    Do you know any standard, where I can find the determination of the material shear properties of the prepreg skin build in thin sandwich construction? The standard bone shaped shear tensile specimen seems to be not appropriate in this case.
  15. irq

    Sandwich Repair

    1) the "glue" used to bond the two parts of filled core may not restore the required core shear strength --- the adhesive strength which bond both cores is higher then the shear strength of the core = ok 2) you cannot "guess" that one additional ply is sufficient to restore strength with a...
  16. irq

    Sandwich Repair

    Thanks to all of you for very informative suggestions regarding option (1). All difficulties with expansion of foaming adhesive and appropriate support of the skin can be avoided by more simple cold repair method (2), which was very little commented (most likely due to lack of more detailed...
  17. irq

    Sandwich Repair

    Hello, Please see attachment - there is a sandwich panel. Let's imagine it is loaded by pressure acting on the top, so that the skins are loaded in tension/compression. The aim is to design the part joining two separate sandwich parts. In many repair instructions we can see the method (1)...
  18. irq

    Von mises for plastics

    von Mises to evaluate fibre reinforced plastics? I think this is not a good idea, since this criterion is mostly applicable to ductile materials and your plastic is more brittle. Max. normal stress seems in this case to be more appropriate. A good approach is to use higher stress of both...
  19. irq

    Comparison of coupon tests, mean or B-Value?

    I need your advice in coupon or connections testing to produce material design values in composite field. I am comparing the new prepreg material to the existing one. The set of samples shows a high percentage difference between standard deviation and mean value of the new material and leads to...
  20. irq

    Meaning of the signature

    I am interested what is the definition of the signature in different organizations? What responsibility you take if you prepare, check or approve the technical documents (you can give some example tasks e.g. for stress reports)? What in case of a new document issue? Are you responsible for a...

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