aymanalsukhon liked a post in a topic by Hyperman in Bird Strike Simulation Divergence
There was an issue with gapmin. Please set /INTER/TYPE7 , GapMin= the 1/2 the pitch you used to generate the SPH particles + 1/2 the thickness of the walls. The pitch is the distance between the particles so 1/2 the pitch is the radius :
Simulation controls were defined and the plate was modified for computational efficiency. Finished model from birdstrike tutorial is also attached.
Hyperman liked a post in a topic by Rahul R in ERROR # 4965 & ERROR 5905
If the solver reports excessive mesh distortion, consider the following reasons:
Excessive or unrealistic loading Over-constrained FE model Inconsistent unit system between model, material and/or loading that lead to excessive deformation Reviewing the last non-converged iteration in HyperView will help
Please refer to attached model from OptiStruct example guide.
OS-E 0195 Compression of Helical Springs usingSelf-Contact.pdf mola_Self_contact_v2_SPCF.fem
Hyperman liked a post in a topic by ppraf in Output contact force
if you can describe the problem in more detail, people in the forum could be able to guide you with the most appropriate solution. To answer your questions,
1) You can also define "contact" by using an ActionReaction Force and using solver function IMPACT or BISTOP. You can mimic a point to point contact or to a certain degree point to curve contact using this approach. Any reason why you do not want to use 2D or 3D contact ?
2) When you define an output - force on body, MotionView creates a <Post_Request statement in MotionSolve xml for the connected joints|bushing|spring-damper|force entities to the body.
These forces can be plotted in Hypergraph. They should be available under the type "Marker Force" and request for each type of above connections would be listed. In HyperView, once you load a result H3D you can go to Vector Plot. Force/Moments should get listed under Result type and select the Body (Assembly in HyperView) and click Apply. Force Vectors should appear on the body selected.
Hope this helps.
Merula liked a post in a topic by Hyperman in Topology Optimization with Inertia Relief seems off ?!
Optimized solutions may seem counter-intuitive at first, but comparing baseline vs. optimized deformations, it can be seen the optimal topology does in fact minimize compliance. The solution does not get connected to "SPC" in the middle, because it is not a constraint (no reaction forces) but a reference point. Adding non-structural mass (see bellow) will provide properly connected solution.
I was expecting that optimizer will place material along regions of greatest strain energy (top left image). Adding concentrated mass in the middle produces expected topology (top right image, attached model). As you have already observed, 0.15 volume fraction is not enough material to connect load application points. I suspect stress singularity due to point loads is the reason why material is concentrated there. DUAL2 optimization algorithm produces better connected solution than DUAL. Eventhough DISCRETE=3 is not recommended for shells (upper bound is 2) it gives expected topology. TOPDISC+DISCRETE looks good, but it is infeasible design (volume fraction 0.43).
rea2 liked a post in a topic by Hyperman in rigid body simulation
If a model has only rigid bodies then Radioss will terminate on first cycle. Include a deformable element in your model (it will control the timestep) as a workaround.
Rigid bodies generally have timestep much higher than other finite elements so it is computationally efficient way to simulate components with negligible deformations.
aymanalsukhon liked a post in a topic by Hyperman in Rigid Walls During Tank Slosh
the reason for very low stress and strain values is because the element size is too big to capture local stress distribution. In the model you shared the shell elements of tank walls are 235mm, while 5-10mm element size is recommended in a typical crashworthiness analysis. Because the whole tank is too big to be solved with such a fine mesh, I recommend you to somehow isolate the area of high stress and solve it using smaller mesh size (found through mesh convergence study).
If you plan to do a convergence check, consider performing at least one refinement of the model after the first run. If neighboring elements display large differences in stress, the gradient was probably not captured in these areas, therefore some mesh refinement is recommended. In general, increasing the number of nodes improves the accuracy of the results. But at the same time, it increases the solution time and cost. Usual practice is to increase the number of elements and nodes in the areas of high stress (rather than reducing the global element size and remeshing the entire model) and continue until the difference between the two consecutive results is less than 5 to 10%.
I recommend you to go through free ebook Practical Aspects of Finite Element Simulation (A Study Guide) which covers 9.12 Mesh Density And Solution Convergence.
Julian_St liked a post in a topic by Hyperman in Meshing Error - tetramesh
2 surfaces failed to mesh in your model. Unmeshed surfaces can be found in the automesh panel (F12)>unmeshed.
The mesh failed probably due to bad geometry. One option is to perform automatic geometry cleanup Geom>autocleanup, but this option can suppress necessary feature edges. Some edges have to be manually edited with Geom>edge edit>toggle or (un)suppress (also in quick geometry edit panel F11).
Wiz211 liked a post in a topic by Hyperman in I can't see the buttons on the HyperMesh User Interface
this is strange. Try view>panels
A similar query was already posted and got resolved by updating.
Hyperman liked a post in a topic by Chris Coker in stress analysis
Direct 3d contact onto flexbodies like you are attempting is currently not supported.
There is a complicated workaround for this, but in general this is not recommended. Essentially, you create many interface nodes over the surface of the flex body. Then create tiny rigid bodies at each one of these location, at attach them with fixed joints. Then, you would define contact for each one of the small rigid bodes that were created.
Julio liked a post in a topic by Hyperman in How to delete unknown entity
looks like symbols for connectors- yellow are unrealized and red are failed.
Open the Connectors browser by clicking View > Browsers > HyperMesh > Connector from the menu bar.
Right-click the connector in the connector entity browser and select delete>connectors.
Refer to tutorial HM-3400: Creating Connectors for more details.
Saravanan R liked a post in a topic by Hyperman in How to reduce number of trias in quads elements
@Curro Capi de Camas
try with: 2D>elem cleanup>reduce tria elems
When active, this option attempts to combine trias into quads. If you also enable elems failing QI check, the tria reduction will be tempered by the constraints on the resulting quads.
ahmad_syafiq liked a post in a topic by Hyperman in No restart file
There is a warning due to material properties:
There are many errors due to bad element quality:
I could remesh the model, but you would not learn how to do it yourself if I did it for you. I just corrected the worst elements so the model is able to run. You should remesh the model using the these tools:
Geom>autocleanup to clean up the geometry 2D>automesh>QI optimize (F12) to mesh using quality criteria 2D>elem cleanup 2D>qualityindex tool>check elems>2D (F10) to check elements
There are some great learning materials from Altair university- Practical Aspects of Finite Element Simulation is a good starting point.
Check the following Youtube channels:
Altair India Student Contest
ELEATION By Apoorv Bapat
test 2_edit.hm test 1_edit.hm
tinh liked a post in a topic by Hyperman in Stress Constraint at Topology Optimization
Stress constraint is not recommended in the design concept stage: topology, topography and free-size optimization.
The stress constraint definition in a topology optimization is a global constraint and does not target local stress concentrations. These areas can be addressed subsequently through size, shape, and free shape optimization or a combination thereof. Artificial stress concentrations are filtered out during topology optimization with stress constraints. These include regions around rigid connections, concentrations due to hard geometric features such as corners, etc.
Stress constraints for a partial domain of the structure are not allowed because they often create an ill-posed optimization problem since elimination of the partial domain would remove all stress constraints. Consequently, the global stress constraint applies to the entire model when active, including both design and non-design regions. Stress constraints may not work well in a model where there is a large differential in response values between design and non-design spaces. In these cases, it is recommended to modify the problem formulation to say, compliance based for example. It is not recommended to use the global stress constraint along with a mass/volume constraint. The constrained mass/volume may not allow the stress constraint to be satisfied.
DRESP1-card stress constraint is used in subsequent design fine-tuning stage such as size, shape and free shape optimization.