# Simon Križnik

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1. ## COMPOSITE BOX

The first anisotropic direction of material could be defined with angle ϕ and global vector (Vx ,Vy ,Vz ). It is also possible to use angle ϕ and skew. In this case, x-axis of skew replaced the global vector V. The orthotropy direction is set with Vx, Vy and Vz parameters in /STACK card (laminate). To override laminate direction set up ply with local skew and Def_orth=1. CarbonBox_edit_0000.rad
2. ## COMPOSITE BOX

Can you share the model?
3. ## COMPOSITE BOX

Hi, when assigning material orientation, make sure the direction is not perpendicular to shell elements. You have probably assigned material orientation in the height direction for the whole component, which is invalid for the elements on top (check material orientation of element 1600). The best practice is to assign material orientation for each surface one by one.
4. ## how to fix laminate so that i can representation in 3D elements

Welcome, refer to step 8: https://connect.altair.com/CP/SA/training/self_paced/aero_v13/PDF/chapter10_demonstration.pdf
5. ## Incorrect deformation behaviour

Upon looking into the model again I found the reason why the buckling initiates at the base of upper crashbox. Looking at the cross-section (deformation scaled 5x) it is revealed the clamping region at the base of upper crashbox slightly rotates inwards, which initiates the buckling. The reason for this behavior is the primary load paths are not aligned (crashbox diameters are different) which induces bending moment.
6. ## HEXA MESH

Hi, the geometry has to be properly partitioned before using automatic hexa mesher (one volume, multisolids). In case of complex shapes, it is challenging to properly partition the solid in order to be mappable in one or more directions- it is even more challenging to strategically plan how these mappable solids come together to produce a structured mesh. Unfortnately, there is no easy fix for hexa meshing as it is the most difficult type of meshing. Refer to the following for details: https://www.altairuniversity.com/wp-content/uploads/2012/04/HM_SolidMesh_Extract.pdf https://altairuniversity.com/wp-content/uploads/2012/03/Bracket_Geometry.pdf https://blog.altair.com/art-of-map-meshing/
7. ## Distribute mass modelling in radios

Hi, this is a strange issue. However, the issue is resolved in recent versions as /ADMAS no longer requires visualization node and the COG is computed correctly. Therefore I recommend updating the version you are using.
8. ## Incorrect deformation behaviour

Hi, there are modeling errors: -3 beam elements have collinear nodes (invalid orientation node). Use the 1D>beam>update panel to resolve this issue. -remove intersections and penetrations with tools>penetration check -the timestep imposed is a bit too high TP004_2_edit_0000.rad The deformation starts at the base of the upper crashbox due to random mesh flow lines that behave as a geometric imperfection. 2-D quad mesh should be systematic (ruled or mapped), avoid 2-D auto mesh: Flow lines should be maintained with minimum number of trias and diamond or rotating quads should be avoided. Use of the auto mesher on surfaces sometimes results in a zig-zag or random mesh which might lead to unexpected problems later. Better Mesh Flow: For crash or non-linear analysis, systematic mesh flow lines where all the elements satisfy the required quality parameters is very important. Using a mix-mode element type instead of pure quad element type helps to achieve better flow lines and convergence of solution. Refer to the page https://www.altairuniversity.com/wp-content/uploads/2014/02/2Dmeshing.pdf
9. ## apply a load to hollow part

Glad to help. You need to split the geometry into design & non-design components using geometry>solid edit>trim with nodes, lines or plane/surf. Solid_Edit_Panel.pdf
10. ## apply a load to hollow part

Hi, it is common practice to create a rigid (RBE2) spider and apply the load to the independent node. In general, it is best not to apply loads and displacements directly to design spaces, as this often leads to incorrect results. Instead, you should split the part into design and non-design spaces, and apply loads and displacements to the non-design spaces.
11. ## How to create a big displacement model for membranes

This error is due to non-convergence (check the out file for details). Increase the number of cutbacks allowed (NCUTS) in the load collector with NLADAPT card image and refer this load collector under NLADAPT subcase definition (loadstep). However, there is a limit when implicit methods become computationally inefficient (buckling, wrinkling, unconstrained rigid body motion, large deformation, rupture, contact with friction,...). These cases can be solved by the explicit method. 30Diametro-edit2.hm
12. ## Avi output error

Hi, looks like something is preventing the writing of the *.avi file: -if writing for the first time, make sure you have permission to write to the specified folder -if rewriting the existing (previously created) file, make sure it is not opened in other applications
13. ## Create marker refering two bodies

Hi, I would also like to know if this functionality (marker orientation tracking between two moving bodies) is available yet?
14. ## How to create a big displacement model for membranes

Glad to help. I suggest you go through free Altair e-books and start with Practical Aspects of Finite Element Simulation. You can also learn from learning and Certification program: https://certification.altairuniversity.com/ > (Learn Modeling and Visualisation)﻿ Check the following youtube channels: AltairUniversity Altair India Student Contest ELEATION By Apoorv Bapat﻿ If you are new to FEA I recommend Finite Element Analysis For Design Engineers by Paul M. Kurowski: https://www.sae.org/images/books/toc_pdfs/R449.pdf
15. ## How to create a big displacement model for membranes

Hi, 1. Use large displacement non-linear static (LGDISP NLSTAT) or transient analysis. Only explicit analysis (Radioss) can converge in case of wrinkling. 2. To get membrane behavior set MID2 and MID3 as BLANK. Membrane has no bending stiffness which can cause convergence difficulties. As a workaround, assign another material of negligible stiffness under MID2 & MID3. 3. Linear static cannot be used because of geometric non-linearity inherent to inflatable structures. 4. It is necessary to assign thickness in any type of analysis. 5. Material MATHE cannot be referenced by properties other than PSOLID/PLSOLID. Therefore it can not be used with shell elements. 6. For computational efficiency this model could employ quarter symmetry as load, BC and geometry are all symmetric. 30Diametro-edit.hm
16. ## Define oblong Cross Section in Optistruct

Hi, use 1D> HyperBeam> solid section to define custom beam section with lines, surfaces, elements or section cuts. Refer to step 5 of HM-4020: Assign Properties Using HyperBeam HM-4020__Assign_Properties_Using_HyperBeam.pdf

18. ## Optistruct Choosing Direct and Iterative Process Solving ?

Hi, SOLVTYP defines the solver type to be used for static and dynamic analysis. Load collector>SOLVTYP card image --> Load Step>SOLVTYPE (subcase option). SOLVTYP.pdf Solvers.pdf
19. ## Variable temperature in a BEAM

Yes, according to Learn Thermal Analysis with Altair OptiStruct ebook: Attached is an example from the ebook which I modified to include multiple heat sources (ambient & local). Note: The ambient temperature is applied with convection on the outer surface. The local temperature is imposed at one end of the tube. This approach is valid for 3D elements, but not for 1D beams. Pipe_One_Step_Transient_multiple.fem
20. ## Pretension Bolt Analysis

Hi, The following might be helpful: https://www.altair.com/resource/optistruct-section-force-output-from-pretension-bolt
21. ## Hyperstudy + Multiscale Designer

Hi, thanks for your response, but I have already found the command line for linear material export. The query is regarding non-linear (multiscale) material export. I hope the Multiscale Designer and Hyperstudy will be coupled similar to Multimech in the future versions.
22. ## Which theory is used to solve in Optistruct with PCOMPP

OptiStruct uses classical lamination theory to calculate effective stiffness and mass density of the composite shell. This is done automatically within the code using the properties of individual plies. The composite inter-laminar stress is calculated based on the first-order shear deformation laminated plate theory.
23. ## Which theory is used to solve in Optistruct with PCOMPP

Hi, according to Optistruct help (page 22): Elements.pdf
24. ## Variable temperature in a BEAM

Hi, this is a simple analysis: For more advanced thermal simulations please refer to FREE eBook: Learn Thermal Analysis with Altair OptiStruct thermal_beam.fem
25. ## Laminate and ply dimensions (surface)

Hi, to get the area of ply use tool>mass calc>elems>by ply (extended entity selection)
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