Creating the 2D and 3D meshing for the given models.

In this challenge, we will be creating the 2D and 3D meshing for the given models.

Objectives,

Check the material properties of the rail component and calculate the speed of sound in steel rail. Calculate the time taken for a stock wave to travel from one end of the rail to other end.

Edit the engine file, so that the stress wave can be monitored. Set the frequency of animation output to a time that will give 20 animation step.

And finally to 3D meshing Tetra mesh and Hex mesh on the given models. Target size is 5mm, Hex size is 10mm, Tet collapse is 0.15.

Introduction,
Time step is the time required for a shock wave to propagate across the smallest distance of the element.

The time step is directly dependent on the length of the element and inversely proportional to the speed of sound of material. The speed of sound of the material is dependent on both material modulus and density of the material. So, if the material is stiffer (higher modulus of elasticity), the speed of sound increases resulting in a lower solution time step.

3D meshing Tetra and Hex mesh,
Hyper mesh has several functions that require the definition of a volume, such as creating tetrahedral and hexahedral meshing. And 3D element shape is Tetra, Penta, Hexa, Pyramid.

Tetrahedral elements can fit better complex geometry. However, when you integrate the shape functions with points of Gauss it is less accurate than hexahedral elements. In addition, one of the factors that determines the quality of your mesh is the distortion of your elements. The reason for this lays on the mapping from real to natural space of integration.

Questions and Answer;

1. Check the material properties of the rail component and calculate the speed of sound in steel rail,

Ans, Young’s Modulus = E =210000 g/mm^2

Density = ρ = 0.0078 g/mm^3

C = √E/√ ρ

C = √210000/√0.0078

C = 5188.74 mm/sec.

2. The length of the rail is about 1000 mm. Calculate the time takes for a shock wave to travel from one end of the rail to the other.

Ans, Length = L = 1000mm,

Speed = C = 5188.74 mm/sec

Δte = L/C = 1000/5188.74,

Δte = 0.19272 sec.

3. Time for sound to travel length of rail is 0.1927 sec.

4. Edit the engine file so that the stress wave can be monitored, moving from one end of the rail to the other during impact -this will require a termination time equal to the time it takes for the sound to travel the length of the rail(set on/RUN card).

Ans,

5. Set the frequency of animation output to a time that will give 20 animation steps (/ANIM/DT).

Ans, Frequency of animation = f = 0.1927/20,
Frequency of animation = f = 0.009636 Hz.

6. Change /print -10.

Ans,

7. 3d meshing tetra mesh and hex mesh,

i) Repeat class examples and, maintain the quality.

ii) Target tet size=5mm, hex size=10mm, tet collapse=0.15.

Ans,

i) Arm Bracket;

First to import the given model in .hm format in the hyper mesh.

The given model had many separate parts, they were individually addressed for meshing. Considering the base for mesh first then hide the another parts and keep base as current component.

Base;

2D mesh < select the surface < element size 10mm < quads only < mesh.
Element offset < select solid layer < element to offset < select generate 2D mesh < geometry follow < select the surface and no of layers 5, total thick is 25 < offset.

Arm Curve;

Next meshing is Arm curve and make it current component. Keep base part visible.
Mask < element < configure < hex8 < select entities < mask.

Then creating a center point. Create node is 3 drag the mouse on the curve < circle center < return.

Then, Spin < select the spin elements < 90 degrees < 25 element in spin < Select center point < x axis as normal plan < plan.

Arm Straight;

Meshing the next part is arm straight and make it current component. Keep arm curve part visible.

Select the arm straight face, Tools < faces < arm curve < select < find face.
Create destination element for linear solid 3D mesh. Match element < Linear solid < select source element < destination element < select 3 nodes on element to align < select 3 nodes for destination element to align,

Deleting the create face for destination element, Tools < faces < delete faces.

Boss;

Meshing the next part is boss and make it current, and arm straight part is visible.
2D meshing face < match all the nodes on the element to good mesh< mesh.

Projected < surface < select node on curve straight to surface < select boss opposite surface project along vector.

Solid map < destination geometry < select unmeshed opposite surface of bass < element drag < elements on meshed side of boss along geometry < mixed < path < select nodes arm < lines < boss < midline < element size is 10mm < mesh.

Delete quad4 element, Delete element < config < quad4 select <delete.
Set current as boss < hide curve straight component < select all element and select all element on boss< move.

After meshing, 3D elements were checked for Tet collapse is 0.15. As we mentioned Tet collapse value is 0.15 while meshing the elements did not fail when checked using element check.

ii) Housing;

First to import the model in .hm format in the hyper mesh.

As given model had two separate parts, they were individually addressed for meshing.

This model has 2 parts hub and cover, 3D mesh can be generated on the model using this any three process, i) Tetra mesh using 2D mesh, ii) Direct 3D mesh, iii) 3D meshing using utility quick mesh.

Cover;

First to consider the cover for meshing, make it current component and hide the another parts.

First to create 2D mesh, 2D mesh < Auto mesh tria is 5mm < mesh.

Now converting 3D mesh by meshing by 3D mesh panel, 3D mesh < tetra mesh < select element < go to element parameter < min tetra size is 3mm < tet collapse is 0.115< mesh.

Masking the element to check 3D mesh created, Mask < select element using shift and mouse < mask.

Hub;

Next part is hub to meshing and make it current, another parts is hide.

2D mesh < auto mesh tria is 5mm < mesh. Now converting into 3D meshing by 3D mesh panel.

3D mesh < tetra mesh < select element < go to element parameter mini tetra size is 3mm < tet collapse is 0.15< mesh.

Masking the element to check 3D mesh created, Mask < select element using shift and mouse < mask.

After the meshing 3D element were checked for Tet Collapse is 0.15. As we mentioned tet collapse values of 0.15 while meshing the element did not fail when meshed using element check.

Conclusion;

Understood the concept of 3D meshing and command for Tetra and hex meshing of a component. Hexahedral mesh is less element faster solution time with better accuracy. And tetrahedral mesh is more complex geometry and mesh quality is easier and better.

And how to check the Check the material properties of the rail component and calculate the speed of sound in steel rail and calculate the time takes for a shock wave to travel from one end of the rail to the other.