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Naveen Raj

Radioss 140

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Hi all,

 

   How unit system is to be followed in Radioss 140. Density, Elastic modulus , force , time etc.,

 

 

I follwed Density in tonne/mm3, Elastic modulus in MPa, Force in  N & time in ms (milli second)

 

Output will be in MPa?

 

What if Density in kg/m3, Elastic modulus in Pa, Force in  N & time in s (second)

 

Kindly help us in solving this propblem

 

 

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Hi Naveen,

There is no fixed unit system in RADIOSS. User has to follow a unit consistency.

If you are following Tonnes and mm, time has to be in seconds. In that case stress output will be in MPa.

For kg,m and second, output will be in Pa.

Please find the normal unit consistency followed across industries with example values.

 

Hope this helps.

UNIT CONSISTENCY.png

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Hi johnson,

 

Thank you for your clarification. It will be very useful

Further adding to my query, How units to be followed for material selection in Radioss 140

Find the attached image for M42_OGDEN material where units were shown in kg/m3 ,pa & s

I followed tonn, mm & s for steel material definiton.

For M42_OGDEN Should I convert density in to tonn/mm3, M1,M2 etc., in MPa to follow unifrom unit system

Kindly clarify

units_to_be_followed.bmp

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Hi johnson,

 

  Thank you for the reply

  Tried following same units

  Tried with 2d elements, Getting error as "Error in input consistency"

"Quad are not compatible with N2D3D=0"

 

Kindly clarify

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Hi Johnson,

 

Tried with element type to quad4N. radioss file which i sent you is with quad4N element type

Error i am getting is

Error in input consistency"

"Quad are not compatible with N2D3D=0"

 

Kindly assist in solving this issue

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Hi johnson,

 

  Thanks for the clarification

  When giving pressure load in block 140 getting error as "rupture of shell element"

  How pressure load can be given in block 140 & how the error can be avoided?

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Hi Naveen,

Create a surface set or contact surface and apply the pressure load over the same with a Pressure v/s Time function.

Is there any rupture/failure criteria in the model?.If not, check the interface and also check for any penetrations.

Please use the recommended contact parameters as below for interface Type 7, if you have Type 7 interface in your model.

Istf=4

Igap=2

Fscale_Gap=0.8

INACTI=6

Gap_min=

Fric = 0.1

Iform=2

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Hi Mr.Johnson,

 

  I have not defined any interface. I created equivalence between nodes.

  Gave pressure by creating contact surface. Getting elenet rupture though sigma max is set @ 500 MPa.

  why this occurs? 

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Hi Mr.Johnson,

 

  Sure file has been shared.

  Control volume defined to introduce inflation pressure effect (Control volume created as "SURF")

  Pressure load given by creating contact surface

  Getting error as "Rupture of shell element"

 

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Hi Naveen,

Received the model. For /MONVOL/GAS the volume must be closed but starter gives a warning  EXTERNAL SURFACE IS NOT CLOSED. Please recheck the same.

The error is happening because of the extreme deformation happening in the model which leads to rupture of elements. Please check the material values for the tyre. I have just modified them and tried running. The same files has been sent to you.

 

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Hi Naveen,

From BCs Manager in Utility Menu you can apply the imposed load. A time vs displacement function has to provided.

Please go through https://altairuniversity.com/learning-library/7-guidelines-to-apply-quasi-static-load-in-explicit-simulation/ which provides the guidelines for applying the imposed loads in RADIOSS. 

Please go through Example 16 in our Help Menu which is a similar case and the same files are attached along for your reference.

Hope this helps.

SEAT_IMPL_DISP_0000.rad

SEAT_IMPL_DISP_0001.rad

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Hi Mr.Johnson,

 

   In the attached image, floor mass of 6ton is applied on the tire

   Spring properties were given for tire, stiffness value calculated from load vs displacement curve

   Imposed displacement of 212 mm applied to the floor

   Analysis is done for no inflation. Stress is not being transformed from tire to disc

   same done for tire inflated condition getting stress distribution from tire to rim (ex - 4barsi inflation pressure)

   Is any changed required in tire stiffness property?

   Floor to tyre contact is given type 7 contact

   Should any change to be done for floor - tyre contact stiffness

 

Regards,

Naveen

  

mesh_model.jpg

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Hi Naveen,

12 minutes ago, Naveen Raj said:

Spring properties were given for tire,

Did you assign spring property to the tyre?. Can you be more clear on this?.

Ensure there is proper connectivity between the tyre and the disc. Run for a bit longer time and review whether stresses are developing on the disc.

For contact, follow the recommended parameters.

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