# Pranav Hari

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8

## Reputation Activity

1.

I think by this way also we can find it out. Try this too
Click Card edit > Select rigids > edit

2. Julio liked a post in a topic by Pranav Hari in Composite mechanical properties
Hello Julio

Apart from the e-book "Practical Aspects of Finite Element Simulation"  please refer the composite e-book also which specializes on composite modelling https://altairuniversity.com/free-ebook-introduction-to-practical-aspects-of-composites/

3.
Hello Wiz211

Also try deleting the settings file and try again

4.
Hi Skill.Leo0

This is explained in the Radioss reference guide and user guide. Please have a look

You can provide Type 7 interface to contact setup between brake pads and brake disk. Refer the attached example also BRAKE2_0000.rad BRAKE2_0001.rad BRAKE2_0002.rad
5.
Dear Pranav
Thanks for giving me such a detailed insight on the queries I had put on ERR Percentage. Its great to know these things which can help me understand the outcome of analysis in much better way.

Thanks and regards
Pritish
6.
Hi Pritish Shubham

ERR signifies the Energy error percentage

It doesn't mean the deviation from the result. Negative Energy Error represents energy dissipated from the system and this can be from many sources including plastic deformation and Hourglass energy.
Please check the hourglass energy of the model.Keep Isolid=24 and try running the simulation.
If the components penetrate each other due to the loads applied the user need to define an interface/contact between them for achieving a realistic simulation. The master segment can be parts, elements, contact surface, node sets and similarly for slave the selection can be parts and node sets. Once these master slave sets are identified the algorithm will check these locations for potential penetration of a slave node through a master segment, and this check is done in every time step

Negative Energy Error represents energy dissipated from the system and positive energy error means energy absorbed in the system

4. What should be the ideal scenario of ERR  Values we should expect while running a solution?﻿﻿

You should check hourglass energy and contact energy in your model. ideally (Hour glass energy + contact energy)/Total energy < 15%

Check this forum post also

7. tinh liked a post in a topic by Pranav Hari in Element Birth and Death
Hi bhanutheja

It is possible by using /ACTIV card. It describes the deactivation/activation of element groups
Check Radioss reference guide for more details. In 2019 HM iform option was added to /ACTIV card where you can activate and deactivate the elements.

8.
Hi,
With LAW2, Iflag=1 the UTS and strain at UTS are engineering strain values.    But the output by Radioss is true stress and strain.  If you look in the Radioss starter you can see the Iflag=0, a, b, n values that are calculated using your input.

JOHNSON COOK MODEL : YIELD STRESS . . . . . . . . . . . . .= 355.0000000000 ULTIMATE STRESS (UTS) . . . . . . . . .= 470.0000000000 STRAIN AT UTS (Ag). . . . . . . . . . .= 9.0000000000000E-02 YIELD COEFFICIENT A . . . . . . . . . .= 355.0000000000 YIELD COEFFICIENT B . . . . . . . . . .= 312.9879880695 YIELD COEFFICIENT N . . . . . . . . . .= 0.2806664576242 EPS-MAX . . . . . . . . . . . . . . . .= 0.2100000000000 SIG-MAX . . . . . . . . . . . . . . . .= 1.0000000000000E+30 ISO-KINEMATIC HARDENING FACTOR. . . . .= 0.000000000000
You can input the a, b, n value into the equation in the comments of LAW2.    Note this equation is true stress as a function of plastic strain and I have left off the temperature and strain rate terms.

Or the pre-processor HyperCrash lets you plot a material when you use a, b, n in LAW2.

Note that this is a plot of True stress versus true strain (not plastic strain).

Please check if your output makes better sense using these stress strain plots.

It is good that you are thinking about the results with respect to your material input to see if they make sense.  Not everyone does this but they should!

Thanks,
Andy

9.
Hi JM Desrosiers

While importing it back to Hypermesh, uncheck the solver option as shown in the image below. It will be in the separate components then.

10.
Hi Santhosh Ravichandran

Refer tutorial OST: 1085, 1095 from OptiSruct help and check whether it helps.
11.
Hi Joao

you will get the result in the .h3D file. You can open it in HyperView and change the result type to strain energy

Also, check this pdf document about strain energy summation
Calculating The Part Total Strain Energy File.pdf
12. Tejas J liked a post in a topic by Pranav Hari in BATCHMESH
Hi Tejas J

Also, check the tutorial
HM-3140: Batch Meshing
13. yehoo liked a post in a topic by Pranav Hari in error 1253
Hi yehoo

I can see from the .OUT file, that the gravity has zero value. Please update it
Also, the shell elements are not assigned with PSHELL property. Check and ensure whether all the shell elements (quad4) are assigned with a PSHELL property.

If the error still persists, please share the model file.
You can use the secure transfer link if needed.
https://ftin.india.altair.com:8443/filedrop/~Ma3TaE

14. Subhu liked a post in a topic by Pranav Hari in Token for feature
Hi Subhu

If licensed under HyperWorks Units, each invocation of SimSolid will draw 30 HWU
15.
Hi manurico

Yes, it is possible.

16. Dragon_heart liked a post in a topic by Pranav Hari in Rubber component meshing
Hi Dragon_heart

You can check this video as well as the learning library for more documents on Hexa meshing.

https://altairuniversity.com/learning-library/

Thanks
17.

1. Right click on the model browser and click create a curve.

2.  click "new" and create a new curve. Change the option to /Table/1

.

3. Close all other windows and select the curve you just created from the model browser. change the options as in the image below. click on data:Ifunc and enter the values in the popup dialogue box

4. There will be 3 fields to define. Ifunc, Strain rate (Ai) and Temp (Bi).
HM lists this as Ifunc, V(0), V(1).

5. Now you can assign this curve from the material data: Table_ID

Hope it is clear...

18. rabi liked a post in a topic by Pranav Hari in the is mesh not enclosed
Hi rabi

Try adjusting the tolerance in the equivalence panel. Please note that adjusting tolerance should not affect the remaining mesh at any points
Or try 2D> replace and replace the nodes manually to give connectivity

19.
Hi,

in explicit method the timestep is affected by characteristic element length, stiffness and density. Please go through the timestep chapter in Free eBook: Crash Analysis With RADIOSS – A Study Guide. Also recommended is 2017 Radioss user guide starting from page 30.

Review what is causing very low time step in the engine out file:
•For an element, check the related material (especially ﻿its Young modulus and density in case of an elastic-plastic material; and its viscosity in case of a visco-elastic material). There must not be an error in the units system that this data is given in. ﻿
Check the size of the element, sin﻿ce elemental length is proportional to time step. If some elements are distorting ﻿badly during simulation it will lead to very low time step and the run will terminate﻿. In this case use small strain formulation (in the property card).
•For a node, check the characteristics of connected elements. If the node is on the master side or the slave side of an interface, this interface must be verified.
•For an interface, the gap of the interface mu﻿st be verified if some failure happens on ﻿the ﻿master or the slave side of the interface. Check the interfaces defined in the model for any penetrations﻿.﻿﻿

https://altair-2.wistia.com/medias/osd349gz4k

To reduce solving time use mass scaling (DT/NODA) or advanced mass scaling (AMS). Any targeted model for AMS application should run first in /DT/NODA/CST with a reasonable energy error (ERROR < +2%) and acceptable added mass (MAS.ER < 0.02) along its simulation time. A model unable to run with /DT/NODA/CST will not run with AMS either. Output the number of AMS iterations per cycle via /DT/AMS/Iflag - Iflag =2 may help to monitor convergence quality at no extra CPU cost.
Maximum allowed iterations before the divergence stops is 1000. 75 to 100 iteration per cycle is a sign of a poor convergence 50 still may provide some speedup
30 iterations or less is considered a good convergence.There should be only a few cycles where INTER is controlling the timestep.

Use Multi-Domain Technique if your model has different subdomains characterized by different mesh sizes and consequently very different minimal time step.

Additionally, you can use single precision (Radioss panel options: -sp) to speed up computation.
Run time remaining can increase during the run even if the timestep does not drop. This happens when available CPU power is used during the run for other tasks (use Windows task manager to check how much CPU is utilized).

Negative Energy Error represents energ﻿y dissipated from the system and this can be from many sources including plastic deformation and Hourglass energy.
If you have included coefficient of friction then the energy error is due to coefficient of friction which is justified. If this amount of energy error is there when no coefficient of friction is defined, then it may be a ca﻿se of penetration which is problematic.﻿ The combined energy error (contact + hourglass) should be less than 15% of the total energy.

Energy error.pdf﻿

The following contact settings are recommended for type 7:
Istf=4
Igap=2
Fscale_Gap=0.8
INACTI=6
Gap_min=1
Fric = 0.1
Iform=2﻿

You can try increasing the Gapmin in your TYPE7 interface which will allow the contact to work sooner and prevent deep penetration. It is also possible to use  /DT/INTER/DEL in the engine file to release slave nodes from the interface when time step drops below the value given in this option /DT/INTER/DEL- however, if there are many nodes released during the run the results can be questionable.
20. Rahul R liked a post in a topic by Pranav Hari in warning
Hi JIAYU SUN

This is because the GeForce series of Nvidia is not officially recommended by HyperWorks. However, this warninig message only appear once. You can proceed further and you may experience some graphical issues in the future.
HyperWorks_2017_Hardware_Recommendations_and_Certifications.pdf
21. Laura27 liked a post in a topic by Pranav Hari in Installation Student Edition 2017
Hi Laura27

When you click on this link, HyperWorks student edition package will be downloaded which has the above-mentioned features.

When the download is finished, install the software and use the altair_lic.dat file attached with the mail.
Set the license file by creating an environment variable as described in the mail.
22.
Hi forestis

HyperWorks do support Nvidia graphics cards, but not the Geforce series. Nvidia Quadro series is officially recommended. The Quadro series is more geared towards CAD and graphics designs, while the GeForce line leans towards gaming.
However, you can still work with the GeForce series. The thing is, you may face some graphical issues.
Check the GPU recommendation of HyperWorks (pdf)

Also, check this to see the difference between Geforce and Quadro series of Nvidia. You can understand which series is best suited for software/simulation/design application.

hyperworks_2018_hardware_recommendations_and_certifications (1).pdf
23.
Contact surfaces can also be used.
24. MEIYARASU19 liked a post in a topic by Pranav Hari in Listing Loads
Hi karth

In HyperView use the vector option, where you can view the magnitude and direction of displacement for selected nodes.

25. Guy01 liked a post in a topic by Pranav Hari in Surface Edge Thickness
Hi Aerokid

Press "O" from Hypermesh or go to preference and select graphics.
Tick the option for thick 1D elements as shown below

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