SOLID TETRA MESH OF HOUSING, 3D HEX ELEMENT MESH OF ARM BRACKET GEOMETRY AND EDITING ENGINE FILE USING HYPERMESH RADIOSS

OBJECTIVE

• To check the material properties of the rail and calcuate, the speed of sound in steel rail, time taken for the shockwave to travel the entire rail and time of sound to travel length of rail.
• To edit the engine file in radioss and set the frequency of animation output to a time that will give 20 animation steps and edit /print -10
• To perform 3D meshing of the geometry housing and arm bracket using tetra mesh and hex mesh with target tet size 5mm , hex size 10mm and maintain the mesh quality with tet collapse of 0.15
• To perform 2D meshing of the geometry and attaining the given mesh quality

CASE SETUP AND EXECUTION

1. Speed of the sound

Young’s Modulus (E) = 210000 N/mm²

Density (ρ) = 0.0078 g/mm³

Length of rail = 1000mm

Speed of sound (C) = √ E/ ρ

(C) = √ 210000/0.0078

Speed of sound = 5188.74 mm/sec.

2. Time taken for the shockwave to travel from one end of the rail to another

Elemental time step Δ t = L/C

Δ t = 1000/5188.74

Δ t = 0.1927sec.

Time taken to travel the shock wave from one end of the rail to another = 0.1927 sec.

3. Time for sound to travel the rail = 0.1927 sec
4. Engine file edit, to monitor the termination time i.e. the time for stress wave moving from one end of rail to another during impact.

FIG. TERMINATION TIME OF STRESS WAVE DURING IMPACT

5. Frequency of animation for 20 steps

Frequency of animation = 0.1927/ 20 = 0.009635 Hz.

Frequency of animation for 20 steps = 0.009635 Hz.

FIG. EDITING ENGINE FILE FREQUENCY 20 ANIMATION STEP

6. Change/print/ -10

FIG. EDIT ENGINE FILE CHANGE PRINT

3D TETRA MESHING ON THE GEOMETRY OF HOUSING

The geometry of housing is of two parts hub and the cover. We need to create 3D meshing on both of the parts.

FIG. HOUSING GEOMETRY

PROCEDURE FOR MESHING

• Importing the geometry of the housing to hypermesh

File>Import>Geometry

• Create 2D mesh with trias on the hub of the housing using F12 2D shell meshing and similarly for the cover of the housing.
• Now to create 3D mesh, click on 3D, select Tetramesh
• Select elements as fixed trias/quad
• Set the parameter for tetra mesh as the target tet size (min. tetra) = 5mm
• Maintain the quality of mesh by maintaining the tet collapse = 0.15
• 1 will be seen at the model tab as the 3D tetra mesh created.

FIG. 3D TETRA MESHING FOR THE PART HUB OF HOUSING

FIG. 3D TETRA MESHING FOR THE PART COVER OF HOUSING

FIG. 3D TETRA SOLID MESH FOR THE HOUSING WITH ZERO ELEMENTS FAILED UNDER THE QUALITY TET COLLAPSE

3D HEX MESHING ON THE GEOMETRY OF ARM BRACKET

In this model of ARM BRACKET , we need to perform solid meshing element type HEX and the set the target mesh length of 10mm. This model consist of 4 parts.

• BASE
• CURVE OF ARM
• ARM STRAIGHT
• BOSS

FIG. ARM BRACKET GEOMETRY

PART 1 BASE

• First we will create 2D mesh on the base, as to avoid Penta 6 elements we need to select quad element type with element size 10mm
• Check the thickness of the base using F4, which is 25mm
• Goto 3D and select element offset option
• select solid layer
• select the 2D elements created
• select the surface for the mesh to follow along the geometry
• mask the 3D elements (by config hex 8)

FIG. SOLID MESHING OF BASE USING ELEMENT OFFSET

PART 2 CURVE OF ARM

• Mask all 2D elements, and retain 2D mesh
• As the arm is curve geometry, so we will use Spin option
• Goto spin option and select spin elements
• Set the angle to 90 degrees and on spin 25
• For this we need a centre point of the circle, use F4 to create 3 nodes on the curve of the arm bracket and hit create circle centre
• A node will be shown which gives you centre of that circle curvature
• Goto spin elements option
• select x axis and B as the base (node), click on B and click on the centre created to select the centre and press spin
• It will create the solid mesh on the curved surface of the arm bracket.

FIG. HEX 8 3D SOLID MESH OF ARM CURVE USING SPIN ELEMENT

PART 3 ARM STRAIGHT

• As both the sides will be exactly same , only the cross section is decreasing in area, so we can use Linear solid
• Before that we need faces of these elements
• Goto tools and select faces, as now it will enable us to select the 2D elements of the plane for linear solid process.
• Goto 3D and select Linear solid, now select the 3 nodes alignment of first elements, and then select 3 nodes alignment of destination elements.
• Both the first and destination elements should be alligned properly to each other
• As the solid mesh is created now we can delete the 2D elements using Faces option.

NOTE

If before working on part, forget to make it as a current part then we can use shift F11 to organize it.

FIG. HEX 8 3D SOLID MESH OF ARM STRAIGHT USING LINEAR SOLID

PART 4 BOSS

• Initially, we will make this part as current and then will create 2D quad element mesh on the side(thickness surface) of the boss
• now we will project the nodes at the surface using F7 node to surface duplicate
• select the node of the straight arm and duplicate the node on the surface of the boss
• Now we will perform Solid map, select the source geometry as none
• Under elements to drag select elements, under along geometry select mixed
• Select element node path and line
• 3D solid mesh is created for the part4 boss of the arm bracket.

NOTE

DELETE ALL THE 2D ELEMENTS USING F2 SELECT THE ELEMENTS BY CONFIG. i.e. quad 4.

FIG. HEX 8 3D SOLID MESH OF PART BOSS USING SOLID MAP

FIG. HEX 8 3D SOLID MESH OF ARM BRACKET USING HYPERMESH

2D SHELL MESHING ON THE GIVEN GEOMETRY

In this we need to perform shell mesh on all the given three components and maintain the quality of the mesh under the given following conditions

Quality Criteria To Be Maintained

• max length = 7
• min length = 3.5
• Aspect ratio = 5
• Skew = 60
• Jacobian = 0.5
• Warpage = 15
• Tria angles = 20 to 120
• Quad angles = 40 to 140

FIG. ELEMENT QUALITY CHECK

FIG. QUALITY CHECK FOR THE GIVEN GEOMETRY PART

FIG. QUALITY CHECK FOR THE GIVEN GEOMETRY PART

FIG. QUALITY CHECK FOR THE GIVEN GEOMETRY PART

CONCLUSION

• The speed of sound, time step of shock wave and frequecy of animation is successfully calculated and the engine file of radioss is edited with these values .
• 3D tetra meshing of housing geometry and solid mesh of hex element for arm bracket are attained and quality of the mesh is maintained as zero elements failed under the quality tet collapse.
• 2D shell mesh is performed and the given quality criteria for the mesh elements are successfully maintained using hypermesh.