Assignment No-2 - 2D 3D meshing of models and Radioss Engine File editing

##Comments by Grader##

Nice Work! Nice Report!

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Assignment No-2

Answers

Question No.1

Open the “FIRST_RUN_0000” file in notepad (see the fig 1)

You can check the properties in hypermesh model under materials (see the fig 2)

Here highlighted data in the first red box are the unit system “g mm ms” (gram, millimeter, millisecond)

and highlighted values in the second red box are material properties of Steel rail.

Material Properties for Steel are as below

Density (ρ) =0.0078 g/mm³

Young’s Modulus or Modulus of Elasticity (E) = 210000 g/mm ms²

Speed of sound in Steel rail

As we know the formula for the speed of sound (c) as

c = square root(E/ρ)

= square root (210000/0.0078)

= 5188.745 mm/ms

Speed of sound in steel rail is 5188.745 mm/ms

Question No. 2

Time duration for shock wave to travel from one end to other end of rail

Length of rail=1000mm

Time duration = Length of Rail / Speed of sound

= 1000/5188.745

Time for the shock wave to travel = 0.1927 ms

Question No. 3

Time for sound to travel the length of the rail

It is same as the time of shock wave to travel as per question no.2

It is equal to 0.1927 ms

Question No. 4, 5 and 6

Editing the engine file “FIRST_RUN_0001” can be done using two methods for question 4,5 and 6

• Open the file “FIRST_RUN_0000” in hypermesh and change the control card settings and run.

or

• Open the file “FIRST_RUN_0001” in notepad and edit the values

Question 4

Termination time should be equal to the travel of sound through the rail length

It is calculated above as 0.192724,

• change the value in Tstop from 60 to 0.1927 in “ENG_RUN” card

Or

• replace the value 000000000000000 by 0.192700000000000 in file “FIRST_RUN_0001”

Question 5

If we want 20-time steps then we should divide termination time by time steps.

Frequency = Termination time /Time steps

=0.1927/20

=0.009635

• change the value in Tfreq from 1 to 0.0.009635 in “ENG_ANIM_DT” card

Or

• replace the value 000000000000000 by 0.009635000000000 in file “FIRST_RUN_0001”

Question 6

• change the value in N_print to -10 in “ENG_PRINT” card

Or

• replace the value by -10 in file “FIRST_RUN_0001”

Question No. 7

Component 1) 3D Meshing of arm_bracket ( Hex Mesh)

Step-1 -Base Meshing

• Hide all the components except base, and mesh the top surface with 2D mesh of element size 10mm and with all QUAD elements.

• Then by element offset tab in the 3D, use the solid layers tab.
• Select all the 2D elements on the top surface
• Select along the surface as two side surfaces as shown
• Keep no of layers as 5 and the total thickness is 25 and

• Press offset +

Step-2 –Arm curve Meshing

• Make arm curve as current component
• Hide the 3D elements of base, keep only 2D elements

• Calculate center for arm curve by using F4 key and selecting three nodes

• Use spin> spin elements command for arm curve meshing
• Keep angle as 90 degree and on the spin as 25( no of elements)
• Select the L shape 2D elements only for spin
• Direction as the x-axis and base B as acenter of the curve

Step-3-Arm straight meshing

• Make arm straight as current component
• Use faces command in Tool tab to find faces of arm curve (those will be 2D elements for arm straight)

• Mesh another end of arm straight with same elements on arm curve end for linear solid meshing

• Use linear solid command in 3D tab
• Use from as arm curve face elements (red elements on face) and to as arm straight elements (blue elements)
• And respective alignment reference and density as 12

• Press Solids

Step-4-Boss Meshing

• Delete all the faces extracted
• Make Boss as current
• Mesh top surface

• By using Shift+F7 shift bottom node to bottom surface for reference, also remember to duplicate the node before shifting

• By using the solid map mesh the Boss

• Move solid map to boss elements
• Delete all the 2D elements

This will complete the meshing of arm_bracket

Component 2) 3D Meshing of Housing (Tetramesh)

Step -1-Hub Meshing

• Make Hub visible and hide all other components
• First we will mesh with tria 2D and converting it to Tetra 3D
• 2D meshing is carried out with an element size of 5mm with all tria elements

• Converting it to tetra mesh using 3D >tetramesh>Tetramesh
• Before converting make sure that the tetramesh parameters as min tet size=3mm and tet collapse=0.15

• Then convert by selecting 2D elements
• Then the 3D elements will be generated in vol001 components

• Check the elements by masking some elements

• Check for tet collapse by pressing F10>3D>Tetcollapse

Step -2-Cover Meshing

• Make Cover current
• In this we use direct 3D meshing for cover
• Select 3D>Volume tetra, keep all trias and element size as 5mm

• Check for tet by masking some elements

• Check for tet collapse as per hub

• Also we can use Quick tetra from Utility menu to mesh components

This is all done with the Tetra mesh of Hub and Cover

Results and Conclusion

• We can get the speed of sound and time step from the material properties
• We can easily edit engine file to get desired results
• We can get more good quality in 2D mesh
• It is good to mesh in 2D and convert to 3D elements wherever possible.

Thanks

Rahul Yadkikar