Enforced Displacement

Hi,

Due to time step drop the simulation was taking more to run. From the starter out file we can see that the model is having very low time step.

This can be due to an element, a node or an interface.

•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.

•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.

Once this is cleared you can run the simulation without time step being dropped.

In this case, it is due to an element, which can be monitored from the engine out (_0001.out) file.

I have imposed a time step in this model in order to control the time step and the run has completed. The mass error generated in this case is also very less.

Please watch this webinar which explains about time step control: http://www.altairuniversity.com/learning-library/considerations-about-time-step/

The model file is attached along.

Hi George P Jhonson.

Thank you very much for your fast reply and sharing the file. You guys are really helpful. Thank for the useful information which you shared.

Hi George

When I'm trying to run the analysis for a similar kind of set up with slight design changes, the analysis is not running till the end it throws up some error as I attached below.

I tried to increase the Gap-min but still the error exists any suggestion or any changes. I have also attached the new design file for your reference.

Thanks in advance

Hi,

Please try with the attached model. 

Hi George

Thanks for the help It is working just fine..

Is it possible to calculate the pulling force in Z-direction with this results by creating output block reaction force like REACX REACY REACZ?

Thanks in advance

Hi,

You can create an output block for the rigid body node and can plot the reaction forces in the required direction.

Hi George

It worked thanks again.

I have attached the deck with the hyper graph

For the calculation of removal force I know that I  have to choose a peak value close to the release. I also need to look at animation H3D file as well to get the corresponding time of exact removal  to get the value.

My question is about the unit systems can you please refer to my file and let me know my removal force with units if possible and can you also tell me that my analysis is correct or not?

Unable to find an attachment - read this blog

Hi Vijay,

The simulation looks fine and all the parameters are fine.

For a better plot, that is in order to reduce the dynamic effect in the plot, you can reduce the time history (/TFILE) plot frequency (like 1e-3).  For the release force of the rod you can create an output block for the rigid body and can plot the time history for the resultant force (TF). We cannot assess the release force for a single point in this simulation, instead the plot is enough.

I think the unit system followed is kg, m, second. Please find the attached consistent unit system followed so that you can find the units for every output.

<?xml version="1.0" encoding="UTF-8"?>

Hi George

Finally done with the clip

I have attached a running board linear static analysis.

I’m getting a deflection of about 0.0053mm deflection. But in real scenario they are experiencing 1 to 5mm deflection.

Instead of applying load on REB3 if I applied load as a point load (single point in the middle of 200 x 80 mm) I’m getting deflection of 3mm.

So what should I do here? Should I use REB3 or point load for a cross section of 200 X 80 mm

Hi Vijay,

This query has been moved to OptiStruct forum and our OptiStruct expert will guide you to solve this. You can follow up the query from : http://forum.altairhyperworks.com/index.php?/topic/20152-linear-static-analysis/

PS:As this is a public forum I recommend you not to attach any confidential model files here. You can send us the model files through the secure dropbox link. 

Hi George

I'm experiencing the same kind of problem in another analysis in which the rubber is not moving with respect to the imposed displacement axis. I have attached the out file. Please let me know if I have to do some changes.

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Hi Vijay,

The load seems to act in the intended direction, as the imposed displacement is defined with a local skew.

Moreover, in the boundary condition applied (ref node bc) it sees like an incompatible kinematic condition as the Y direction is locked. Please recheck the same

<?xml version="1.0" encoding="UTF-8"?>

Hi George

I changed boundary condition in ref node bc, still the problem continues. I want to bring down all the 3 components as shown in the picture, but for some reason only partial RUBBER is coming down. Can you give me some solutions. Thanks in advance.

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PIC 1

<?xml version="1.0" encoding="UTF-8"?>

<?xml version="1.0" encoding="UTF-8"?>

Hi Vijay,

While applying imposed displacement select all the nodes of these three components, including rigid body master node and try running the analysis.

Hi George

I did the way you told be. It's working but the rubber is passing smoothly (overlapping) the bottom sheet metal. Any suggestion thanks in advance... I also attached the radioss deck for your reference...

<?xml version="1.0" encoding="UTF-8"?>

<?xml version="1.0" encoding="UTF-8"?>

Unable to find an attachment - read this blog

Hi VIjay,

Please redefine this interface (interface id-1)..Instead of contact surface for master select components and select sheet metal 2 as master and node set of rubber as slave, with a Gapmin of .0025, Istf=4, and run the analysis. And I think between rubber and tape components Type 2 interface may be better. Please try with the same.

Hi George

I followed the instructions but for some reason the rubber is not stretching. I have attached the deck for your reference. 

Thanks 

<?xml version="1.0" encoding="UTF-8"?>

Unable to find an attachment - read this blog

Hi Vijay,

Please recheck the unit system followed in your model. I think the unit consistency is wrong.

Please modify the units accordingly with this consistency shown. 

Regarding the contact issue, for the sheet metal part constrain only the end nodes of the component instead of constraining all the nodes and try running. 

<?xml version="1.0" encoding="UTF-8"?>

<?xml version="1.0" encoding="UTF-8"?>

Hi George.

I have completely done what ever you mention I'm still facing some problems.The main problem in this analysis is the contact. I have shared the deck and output file for your reference. Thanks in advance please do give me some suggestions. Thanks 

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Hi Vijay,

Which unit system you are following for this model?. Is it like grams,metre,second?

Hi George

Yes model is in meter and modulus is in pascal

Hi Vijay,

The unit consistency is wrong. If it's grams, the length to be followed is either mm or cm. If you want to follow the length in meter, then mass should be kg. Please scale the model accordingly and modify the material parameters. 

Hi john,

Hope you  doing well,

I running one analysis on rubber material just to get the curve ( as shown in below image) Its Force vs displacement curve. Do you have any example model similar to this Or please tell me the what are the request can select for output parameters its in Radioss solver only.

<?xml version="1.0" encoding="UTF-8"?>

Hi,

Unfortunately no tutorials/examples are available on the same.

Create output block for the components and you can use cross plot for Force vs Displacement curve. The below post shows creating cross plot in HyperGraph.