Assignment 2-RADIOSS Engine File Editing & 3D Meshing Challenge

OBJECTIVE :

• To check the material properties of the rail component and calculate the speed of sound in steel rail.
• To calculate the time takes for a shock wave to travel from one end of the rail to the other given that the length of the rail is 1000 mm.
• To edit the engine file so that the stress wave can be monitored, moving from one end of the rail to the other during impact.
• To set the frequency of animation output to a time that will give 20 animation steps in the engine file.
• To perform 3D meshing on the given components with given quality parameters.

Importing and reading RADIOSS Starter file to answer the given Questions :

First, we have to check the material properties of the rail component. There are two multiple ways to check the material properties. One of the ways is to import the file in Radioss and check for the material properties. So after opening the Hypermesh, we will choose our user profile as RADIOSS. Then we will import the starter file in Radioss. In our case, the given file name is FIRST_RUN_0000.rad, we will import this file under Import Solver Deck browser as shown below,

Then we will click on Import command. After importing the component, we can see the Rail component in the Hypermesh Graphics area. Now to calculate the speed of sound in steel rail, we have the following formula,

c=√E/rho

Where, c is the speed of sound, E is Young’s Modulus, and ρ is density. So based on the formula, we will need the value of E and ρ of the rail component. We can find these values of the Rail component in the Material Properties of the model as shown below,

Calculations:

Thus the speed of sound in steel rail is 5188.7452 m/s or 5188.7452 mm/ms.

the time required for sound to travel length of rail is 0.1927 ms.

So, the animation has to be captured for every 0.009635 ms.

Now, we have to insert these values in the Engine file. We can do this by directly typing these values in the Engine file.

RADIOSS Engine File Editing in Notepad :

We will open FIRST_RUN_0001.rad file in Notepad. Here we have to identify and change the values of Termination time and Animation Frequency.

After identifying these values, we will edit them by inputting the values of Termination time and Animation Frequency which we got through calculations.

The values edited in the Engine file are in green box in the figure above. Then we will save this file to complete the editing of the Engine file.

3D MESHING :

1. Housing Model (Tetramesh) – The given model is as follows,

After importing the model in Hypermesh, we will look for surface defects in the model in order to perform Geometry cleanup. As there were no surface defects in the model, we will proceed for meshing. There are two components in the model which are hub and cover. So we will mesh them one by one. In general, there are three methods to generate tetra meshing as given below,

• Conversion of 2D tria to Tetrahedral Elements, by using Tetra Mesh panel.
• Using the Quick Tetra Mesh from Utility panel.
• Using Volume Tetramesh panel.

So for hub component, we will perform meshing by first method i.e. converting 2D tria to 3D tetra elements. We will make hub component as our current component and hide other components and then navigate to 2D Automesh panel by F12 shortcut key. Here we will select the displayed surfaces and enter the value of target element size as 5 mm. The important thing is we have to select the mesh type as trais only and click on mesh. After creating 2D tria elements on the hub, we have to convert it to 3D tetra elements. For this we will go to tetramesh panel in 3D page where we will select the 2D tria elements under Fixed trias/quads to tetra mesh option. Here, we have maintain tet collapse criteria as >0.15 which we will specify before meshing in Tetramesh parameters sub-panel.

Now we can mesh the elements in Tetramesh sub-panel. Thus the 3D tetra mesh will be created on the model. To verify the 3D mesh, we will mask some elements in mask panel and verify. In order to check for tet collapse criteria, we will navigate to check elems panel by F10 shortcut key and check for tet collapse in 3d sub-panel. Here, as we specified the tet collapse criteria to be greater than 0.15 in Tetramesh panel before meshing, we have zero elements failing in tet collapse. Thus the meshing result of hub component is shown below,

Now we will perform 3D meshing on cover component. We will make it as our current component and hide all other components. We will mesh this component by third method i.e. Volume Tetramesh. So we will navigate to Volume Tetra sub-panel under Tetramesh panel in 3D page. Here we will select the displayed surfaces, mention element size as 5 and then we will click on mesh. This feature will create 3D tetras in the enclosed volume of the component. Now we will again check for tet collapse criteria. As we specified the tet collapse criteria to be greater than 0.15 in Tetramesh panel before meshing, we have zero elements failing in tet collapse. Thus the meshing result of cover component is shown below,

At the end, we will delete the 2D tria elements which we created earlier on hub component. To do this we will navigate to delete panel by F2 shortcut key. Here we will select elements by config as tria3 and click on select entities which are displayed. This will select all the 2D tria elements. Then we can click on delete entity option to delete all the 2D trias and have only 3D tetras in our model.

2. Arm Bracket (Hexamesh) – The given model is as follows,

After importing the model in Hypermesh, we will look for surface defects in the model in order to perform Geometry cleanup. As there were no surface defects in the model, we will proceed for meshing. There are four components in the model which are base, arm curve, arm straight and boss. So we will mesh them one by one. At first, we will mesh base component as it can then be useful to mesh the other three components. We will make it as our current component and hide all other components. For base component, we will create 2D mesh on its top surface by selecting the mesh type as mixed. So basically we will create all 2D quad elements on the surface. To convert it to 3D hexa elements, we will offset these elements. So we will go to elem offset panel in 3D page. Here, under solid layers panel, we will select the 2D elements to offset, mention the number of layers as 5 and total thickness which is measured as 25 and then click on offset command. This will create 3D hexa elements by offsetting the 2D elements in 5 layers to a thickness of 25.

Now, we will mesh the component connecting the base which is arm_curve as the base component has the imprint topology of arm_curve component. We will make it as our current component and hide all other components. The geometry for this component is like a partial Torus. So we can spin the elements to obtain 3D hexa mesh. So we will navigate to spin panel in 3D page. Here under spin elems sub-panel, we will select the 2D elements from the imprint area, enter angle as 90, on spin as 25 and select x-axis as our rotation axis. For base point, we will navigate to distance panel by F4 shortcut key and create a center node with the help of three nodes option. This center node will be used as the base point and then we will use spin option to spin the elements. Thus the 3D hexa elements will be created along the geometry profile in 25 layers.

Now, we will mesh the component connecting the arm_curve which is arm_straight. As this component has tapered geometry, we will perform linear solid command to obtain 3D mesh. We will need 2D elements or faces to create linear solid. So we will create faces from the 3D hexa elements of arm_curve component. We will navigate to faces panel in Tool page, where we will select the elements of arm_curve and then click on find faces. This will create faces on the arm_curve elements. On the other tapered surface of the arm_straight component, we will create 2D mesh in such a way that the nodes and elements are exactly corresponding to the opposite face as shown below,

Then we will go to linear solid panel in 3D page. Here, we will select from elements as the face elements present on the joining surface of both the components which are in red and to elements as the tapered surface elements which are in blue. We have to make sure that there is proper node alignment, we will set the density to 12 and then we will click on solids. This will create 12 layers of solid hexa elements connecting both the mesh. Now we will delete the faces created earlier and get the final result as follows,

Now we will perform meshing on Boss component. We can mesh this component using general solid map since we also have to connect the mesh to the elements of arm_straight component. At first, we will project an outermost node to one of the plane surfaces of the component using project command. Then we will create 2D mesh on the other plane surface. Then we will navigate to general sub-panel under solid map panel in 3D page. Here, we will specify source geom to none, dest geom to be the opposite surface, elems to drag will be the 2D created elements, along geom to be the node path and then click on mesh. This will create 3D hexa elements connecting the elements of arm_straight component. These elements will be stored in a new component named solidmap. We will move these elements to boss component using organize command. Thus the mesh is as follows,

At the end, we will delete all the 2D shell elements present in the model. To do this we will navigate to delete panel by F2 shortcut key. Here we will select elements by config as quad4 and click on select entities which are displayed. This will select all the 2D quad elements. Then we can click on delete entity option to delete all the 2D quads and have only 3D hexa in our model.

Final Result –

CONCLUSION :

The speed of the sound in steel and the time taken by the sound wave to travel through the length of the steel rail has been successfully calculated. These calculated values are given as the termination time and the frequency of the animation output in the engine input file by editing the .rad file directly. Then the two components (housing and arm bracket) are meshed using the 3D solid elements (tetra and hexa) with the required quality and mesh flow.