3D meshing & editing the engine file.

Objective:-

To solve the following questions and perform 3D meshing for Housing with tetra elements(target element size =5mm, tet collapse =0.15mm) and hex mesh (target element size 10mm) for arm bracket.

1. Check the material properties of the rail component and calculate the speed of sound in steel rail=_______
2. The length of the rail is about 1000 mm.calculate the time it takes for a shock wave to travel from one end of the rail to the other.

3.Time for sound to travel length of rail=______

4.Edit the engine file so that the stress wave can be monitored, moving from one end of the rail to the other during an 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)

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

6.Change /print -10.

Solution:-

Before starting with the question let's take an overview of Radioss,

Radioss is a multidisciplinary FEA solver used to solve both linear and nonlinear problems.Radioss is mostly used in structural analysis with high nonlinearity and dynamic loading.

Radioss majorly consists of two files namely:-

1. Starter File

File Name	File Type	Description	Role
runname_0000.rad	ASCII	Starter input deck file	Contains model information such as mesh,boundary conditions,interfaces, load cases, etc.
runname_0000.out	ASCII	Output File	Contains information about all the things specified in the starter file for e.g material.
runname_0000.rst	Binary	Result File	Can be used to restart simulation in the place where it dropped due to errors.

1. Engine File

File Name	File Type	Description	Role
runname_0001.rad	ASCII	Engine Input file	Contains information regarding the time steps,animation time etc.
runname_0001.out	ASCII	Engine Output file	Contains information regarding time elapsed, time remaining etc.
runnameA01...Ann	Binary	Animation files	Contains every information regarding animation.
runnameT01	Binary	Time history files	Contains information about time steps.
runname_0001.rst	Binary	Restart files	Can be used to perform new simulations by varying the boundary conditions.

Solution for question 1:-

The material properties of the given file can be checked either by opening the .rad file in notepad or opening the solver deck and checking the material card.

The material properties are :-

• Density ()= 0.0078 Kg/m^3

• Young's Modulus (E) = 210N/m^2

Speed of sound = E/ = 5188.74 m/s.

Solution for question 2 & 3:-

The time required for the shockwave to travel 1000mm (0.1m),

We know that Speed = Distance/Time, therefore Time = Distance/Speed = (0.1/5188.74) =0.00001927s =0.01927 ms.

Solution for question 4:-

To set termination time equal to the time it takes for the sound to travel the length of the rail (Cards<ENG_RUN).

Solution for question 5:-

Desired number of animation steps =20

Termination Time= 0.01927ms

Therefore t =Termination time/Desired no of animation steps =0.01927/20=0.0009635.

Solution for question 6:-

Open the ENG_Print and change N print to -10.

3D Meshing:-

• Tetra meshing

Step 1:- Import the model into HyperWorks.

Step 2:- Check for topological errors by switching the model to BY TOPO mode.

Step 3:- Meshing

Tetra Meshing can be carried out it two ways:-

• The first 2D mesh then converts the 2D mesh into tetra mesh.

1. For meshing with 2D elements [2D<automesh<surfs(select surfs)< element size(5mm)< mesh].

Note:- While meshing with 2D elements avoid quads by selecting trias only option to avoid penta6 elements.

1. Once 2D mesh is created convert it to tetra elements [3D<tetramesh
2. trias/quads to tetramesh(select elements)<mesh].

• Direct 3D mesh using Volume tetra option [3D<tetramesh].

Note:- While tetra meshing always input the tetra mesh parameters first for e.g tet collapse.

• If the tetra element fails for tet collapse quality parameter it can be fixed by following two ways

1. Remeshing the failed elements by tetra remesh option.
2. Using the translate option (shift+F4) to translate the node to get the desired tet collapse value.

• Hexa Meshing

Step 1:- Import the model in HyperWorks.

Step 2:-Check for topological errors by switching the model to BY TOPO mode,

Step 3:- Meshing-In this given model we have three parts (Base, Arm Curve,Arm Straight, boss).

1. Meshing Base:- For base, the surface is meshed with 2 elements (2D<automesh<surface).After meshing with 2D elements, for hexa elements we can offset [3D]the elements to get brick elements.
2. Meshing Arm Curve:-For meshing Arm Curve we need to create a base node at circle centre(F4) and then use spin[3D<spin<elements(select 2D base elements )].
3. Meshing Arm Straight:- For meshing this part we need to extract face[Tool<faces<components(select arm curve)3D] because the part is a taper.
4. Meshing Boss:- First mesh one side of the boss with 2D elements, for the mesh to follow the path of the arm straight project a node[Shift+F7] on the unmeshed side.Then use solid map(3D). Once the solids are created the elements are transferred to boss (Tool< organize ).

Note:- While using linear solid make sure the elemental count matches both sides. Avoid trias in 2D mesh to prevent penta6 elements.

• 3D elements can be checked by masking(f5) few elements

Result & Conclusion

1. The speed of sound in steel rail is 5188.74m/s.
2. The time required for sound to travel is 0.01927ms.
3. Tstop=0.01927ms
4. The frequency for 20 animation files is 0.0009635.
5. The hub and cover have successfully meshed with tetra elements with no elemental failure for 0.15 tet collapse.
6. The arm bracket has successfully meshed with hex elements with target element size 10mm