Problems using LOAD/PBLAST

Bennet Reiner

Hello together,

i am traying to simulate the Load of an explosion on a steeldoor within a Frame of concrete. Unfortunately the Solver shwos the error "**ERROR : TIME STEP LESS OR EQUAL ZERO", but i cant find the Problem in the Model. Does somebody already used the load PBLAST and can tell me what i did wrong?

Thank you for any kind of help.

 

Best reggards 

Bennet

Rogerio Nakano_21179

Hi

Could you share also the *_0001.out file?

It seems that the equivalent mass of explosive in  /LOAD/PBLAST is 0.0

 

 

Regards

Bennet Reiner

Rogerio Nakano_21179 said:

Hi

Could you share also the *_0001.out file?

It seems that the equivalent mass of explosive in  /LOAD/PBLAST is 0.0

 

 

Regards

Hi Rogerio,

thank you very much for help. I hope you can tell me whats wrong with my model. It is the first time i use this Loadcase.

 

Best regards

Bennet

Rogerio Nakano_21179

Bennet Reiner said:

Hi Rogerio,

thank you very much for help. I hope you can tell me whats wrong with my model. It is the first time i use this Loadcase.

 

Best regards

Bennet

Thank you.

What is the consistent unit system you are using?

if it is not {g,cm,microsecond}, that is the system that explosive material is based, you need to use /UNIT and associate to the /LOAD/PBLAST. Please refer to the help docummentation /LOAD/PBLAST, comment 3.

Also , as /PBLAST is not supported currently in the preprocessor, I can see that you set it as unsupported card.

Please double check /PBLAST data in the deck after exporting, as the values on /PBLAST are exported offset to the left. Be sure that the values are located as defined in the Keyword documentation.

 

Hope this is helpful.

Regards

 

 

Rogerio Nakano_21179

Rogerio Nakano_21179 said:

Thank you.

What is the consistent unit system you are using?

if it is not {g,cm,microsecond}, that is the system that explosive material is based, you need to use /UNIT and associate to the /LOAD/PBLAST. Please refer to the help docummentation /LOAD/PBLAST, comment 3.

Also , as /PBLAST is not supported currently in the preprocessor, I can see that you set it as unsupported card.

Please double check /PBLAST data in the deck after exporting, as the values on /PBLAST are exported offset to the left. Be sure that the values are located as defined in the Keyword documentation.

 

Hope this is helpful.

Regards

 

 

Attached a modified model.

I was not sure of units, but can can correct/scale in this deck and you can add the output you need.

Also noticed that you are using linear elastic material. if you expect that structure would not yield,  it is fine. Otherwise, an elasto plastic material model would be needed to capture plastification on the material.

Regards

Bennet Reiner

Rogerio Nakano_21179 said:

Attached a modified model.

I was not sure of units, but can can correct/scale in this deck and you can add the output you need.

Also noticed that you are using linear elastic material. if you expect that structure would not yield,  it is fine. Otherwise, an elasto plastic material model would be needed to capture plastification on the material.

Regards

Hi Rogerio,

now the Error is gone, thank you very much. I used the linear elastic Material, because i just wanted to show how to use the load case, but there is still no Pressure on the surface. Can you tell me if i did something wrong with the definition of the surface? I used GRBrick to define the elements that are affected of the Loadcase. Is it psooible that he cant find the surface?

Thank you very much.

 

Best Regards

 

Rogerio Nakano_21179

Bennet Reiner said:

Hi Rogerio,

now the Error is gone, thank you very much. I used the linear elastic Material, because i just wanted to show how to use the load case, but there is still no Pressure on the surface. Can you tell me if i did something wrong with the definition of the surface? I used GRBrick to define the elements that are affected of the Loadcase. Is it psooible that he cant find the surface?

Thank you very much.

 

Best Regards

 

Hi

Currently there is no option to output the pressure contour due to the PBLAST load.

An alternative option is to request external force with /ANIM/VECT/FEXT. As the external force is contoured you will be able to indirectly observe the incident pressure .

For clarification: The output 'pressure' you have on HyperView as requested by /ANIM/BRICK/P, it is hydrostatic pressure in the element.

 

Regards

Bennet Reiner

Rogerio Nakano_21179 said:

Hi

Currently there is no option to output the pressure contour due to the PBLAST load.

An alternative option is to request external force with /ANIM/VECT/FEXT. As the external force is contoured you will be able to indirectly observe the incident pressure .

For clarification: The output 'pressure' you have on HyperView as requested by /ANIM/BRICK/P, it is hydrostatic pressure in the element.

 

Regards

Hi Rogerio,

 

okay thank you very much. You are a big help for me. Unfortunately there is still no force on my structure and i dont see what i did wrong. Could you please have another look on it? I really appreciate your help.

 

Best reggards

Bennet

Rogerio Nakano_21179

Bennet Reiner said:

Hi Rogerio,

 

okay thank you very much. You are a big help for me. Unfortunately there is still no force on my structure and i dont see what i did wrong. Could you please have another look on it? I really appreciate your help.

 

Best reggards

Bennet

Hi
Did you run the model deck i sent you ?

In this new *.hm file from yours, the charge of 20,000. grams is still positioned in location that is not near the wall nor in location that blast pressure would load it directly.

And 10microseconds is not long enough to the pressure reach the wall from that distance.

And What is missing on your engine deck is the /ANIM/DT to record the results you want.

In the attached model deck, please read it and run, i repositioned the charge.
and increased the scenario runtime to 1010microseconds.

Attached is the stress on the wall.

Regards

Bennet Reiner

Rogerio Nakano_21179 said:

Hi
Did you run the model deck i sent you ?

In this new *.hm file from yours, the charge of 20,000. grams is still positioned in location that is not near the wall nor in location that blast pressure would load it directly.

And 10microseconds is not long enough to the pressure reach the wall from that distance.

And What is missing on your engine deck is the /ANIM/DT to record the results you want.

In the attached model deck, please read it and run, i repositioned the charge.
and increased the scenario runtime to 1010microseconds.

Attached is the stress on the wall.

Regards

Hi Rigerio,

thank you so much for your help. Your model deck is working. But i dont really understand on what indicators the Loadcase works. I thought the load is computed from the sclaed distance of the entered koordinates.

I wanted to simulate a 20 Kg TNT load at distance of 4 m from the structure. Can you tell me what i have to consider at his coordinates?

Best reggards

Bennet

Rogerio Nakano_21179

Bennet Reiner said:

Hi Rigerio,

thank you so much for your help. Your model deck is working. But i dont really understand on what indicators the Loadcase works. I thought the load is computed from the sclaed distance of the entered koordinates.

I wanted to simulate a 20 Kg TNT load at distance of 4 m from the structure. Can you tell me what i have to consider at his coordinates?

Best reggards

Bennet

Hi

If you are considering cm as length dimension.
The center of the wall is located at about (x,y,z)=(1500,796,900)cm. then your change would be located about (xc,yc,zc,) = (1500,396,900)cm, so that it is 400cm away.
And this is the location coordinates you need to use. There is not scaling happening to these values ( it would happen if you use /UNIT)

Also your consistent time unit is microseconds.
if think about just sound speed, for instance, the sound would take about 11500.00microseconds to travel 400cm.

So you are not running long enough if the charge is 400cm away from the wall.

In attached image, I positioned the charge 400cm away from the wall.
And ran long enough, so that the stressing on the wall seems to happen after about 3000microseconds.

Regards

Bennet Reiner

Rogerio Nakano_21179 said:

Hi

If you are considering cm as length dimension.
The center of the wall is located at about (x,y,z)=(1500,796,900)cm. then your change would be located about (xc,yc,zc,) = (1500,396,900)cm, so that it is 400cm away.
And this is the location coordinates you need to use. There is not scaling happening to these values ( it would happen if you use /UNIT)

Also your consistent time unit is microseconds.
if think about just sound speed, for instance, the sound would take about 11500.00microseconds to travel 400cm.

So you are not running long enough if the charge is 400cm away from the wall.

In attached image, I positioned the charge 400cm away from the wall.
And ran long enough, so that the stressing on the wall seems to happen after about 3000microseconds.

Regards

Hi Rigerio,

is Radioss also converting the dimensions of my structure to the Begin units? The center of the structure is originally at (x,y,z) = (1500, 796, 900)mm

Thank you very much for your help!!!

 

Best reggards 

Bennet