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disla
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Right, as far as I have seen frequencies are fine.
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CONCLUSION : Nowadays, B31 element isn't reliable for modal analisys (2024). DETAILS in the ccx Forum.
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Files
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If you are using ccx, beams can also be offset. I would test extensively cause i'm not sure if that's safe to use and how it does affect deflections, stresses, and if it will make any effect. EDITED: Internal also has offset from ver.25.Beam offs…
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Only Mecway. Handmade. Start with very simple rectangles (10) and later custom refinement. Extrude only at the end.
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I put in the Y rotation constraint on the advice of the CCX manual after it was failing without it That's weird. I didn't notice that because I always use PARDISO MKL and it has been working fine for me. You are completely right. Adding rot y con…
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OH, That's new ¿isn't it?. I mean Rigid body definition through a set of nodes instead of surface. I'been doing this manually for a long time . I think y rotation should be free to be a hinge.
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I have worked a little on the mesh. I have meshed the section and later extrude it. With a good mesh is much faster.(3 min) The FEA model will be better driven imposing a rotation. Be sure to evaluate correctly the forces needed to achieve that rot…
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Give it a try to Straight. It should do the job. I have edit one of my previous posts: Straight allows the nodes on the line to stretch and change distances in between them while keeping them aligned.
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This is the fastest rolling set up I can imagine. Not what you first ask as nodes are not enforced to keep aligned but could be valid for small displacements.
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Hi, If you distribute the load over a certain surface below the plate you could use the rigid body as it is implemented (based on a surface and a REF node). Mecway have shortcuts for some elaborated BC but not all of them.
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You need custom cards to do that. Reducing all DOFS of an aligned set of nodes to two, requires a rigid body definition of those nodes. (Good moment to remind Victor about this possible improvement ) To keep them in an axis and all body free to r…
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Hi, ¿Do open radios also have eigen solver.? In that case, do you think it could be worth to use it know the actual limitations in Arpack.
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Hi, I find the system more predictable using Initial position and velocity as BC. Force seems unpredictable to me as one usually doesn't know the time duration and shape of the initial impulse. Exact solution can be found as a function of x(0) and…
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This are the You tube file and the simplified 3D Spaceframe file using the last refined set up. Its more work but the result is definitely worth it. Very accurate buckling loads compared to Euler. The buckling values obtained with LBA are those of …
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Your buckling analysis won’t be right. All the beam and truss elements only have two nodes so the buckling load will not be extracted correctly. I suggest you start with much simpler tutorials and models like the YouTube one. It has a known solution…
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Good news, Just comment that Victor has been working on this and found a much better and reliable approach than mine. It involves more work to set up the model but he is working to make it easier adding some internal coding. Results are consistent …
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Would you share one of those models that are giving you issues in NLG?. Light version if possible.
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I saw this yesterday. It immediately made me recall this post and the uncertainty of load distribution on a four rig scheme, especially close to the detachment point. I hope there were no casualties.
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Buckling can foresee global instabilities like lateral buckling on a lattice for example. That doesn't show up in the static analysis. It can also be used to extract buckling shapes to build the initial imperfections for the NLBA analysis. Or f…
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I would strongly recomend you to start with the simpler youtube model. A reduced and simpler 3D version of your problem took some hours of trial and error to set up, keep the truss nature and remove all spurious modes. I have only obtained some re…
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HI, I have built a buckling analysis file with trusses. The idea is to explore different work paths to see to which extent Mecway/ccx can solve a Buckling analysis of a structure involving this kind of elements. It’s simpler than yours, with less …
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Hi gscheffer, May I ask you which load would cause that displacement pattern? Are those strict displacement imposed for some theoretical validation?
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This is the expected result for Euler with my parameters
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Hi, @LHartley Main drawback with truss elements is that to work properly and do not become a mechanism they should only have two nodes. They may work fine for static, but two nodes are insufficient to give good result in buckling analysis. See fil…
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Gravity load shouldn't be inside the Buckle Step. I apply it in a previous step and then the Buckle is computed as a perturbation. That's because the self-weight doesn't scale, is always fixed no matter the external loads. I recall a buckling analy…
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Problem depends on how the contact is enforced in real world. BC must reflect that process. For example. If glass assembles on top of the mold in horizontal position, self-weight seems enough to make glass and mold to accommodate each other, and it …
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Nonlinear Dynamics with large rotations. Axis should keep aligned to the global axis after each rotation and it does. Angular momentum is nicely preserved. After some cycles numerical error acumulates and it starts to deviate but more than enough. …
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My bigest problem with my first small tests, is that the color coding of the bar stresses does not show up well on the screen. I experienced that too. Victor help me at this point. "On nodes shared by beams and solids, CCX averages the beam int…
