Week 2 Challenge : Surface meshing on a Pressure valve

For the given model, check for the geometrical errors and perform Topology cleanup accordingly. Set three different target lengths as three different cases and mesh the model.

• Target length = 1mm, 3 mm and 5 mm (i.e. 3 cases)
• Element type = Tria

• To create a surface mesh on a pressure valve using ANSA with target length of 3mm ,1mm and 5 mm.
• Take the element type tria.
• Meshing is done to discretise the given model into finite number of elements
• Meshing is one of the most important steps in performing an accurate FEA simulation.
• A mesh consists of elements that contain nodes (coordinate locations in space that can vary by element type) that represent the shape of the geometry.
• When Mesh length is small, the number of nodes should be high.
• when Mesh length is small, the number of nodes should be low.
• Mesh length is the distance between two nodes.

• Types of 2D meshes :

  • Quad
  • Tria
  • Ortho Tria
  • Mixed (Quad and Tria)
• Among these types of 2D meshes, the three-dimensional mesh is highly preferred because the three-dimensional mesh has the shape of an equilateral triangle and its quality is relatively high.
• Steps-
• Import the CAD model
• Display settings
• Geometry check
• Creating a PID
• Defining the size or length of an element
• Meshing type selection
• Generating the Mesh.

• Different types of modules in ANSA:-

• TOPO - A set of tools for cleaning geometry and for setting PID.

• MESH - Tools for generating Surface Mesh or 2D Mesh.

• VOLUME MESH - To generate a solid or 3D mesh.

• DECKS - Tools based on various solvers like ABAQUS, RADIOSS, ANSYS, etc.

• MORPH - An advanced tool for capturing geometry more accurately when creating a mesh.

• CROSS - Tools for defining a cross section.

• Surface Meshing -An area mesh is a representation of a surface that consists of vertices, edges, and faces.

• A surface mesh consists of a set of polygonal surfaces, often triangles, which together form the surface covering of an object.

The first step we need to do is to import the given geometry and perform a geometry check to detect any errors that are present in the imported geometry.

As we can see we have many individual tapers and gaps/open faces in the geometry, ANSA counts them both as errors as shown above after doing the geometry check. So the first thing we need to do is to fix these errors.

To see all the mistakes/single negatives we can turn off the image shadow and turn off the double and triple negatives to see only the single negatives properly as shown below.

There are many ways to fix these errors such as; using the "New surface" option, using the "coons" option in surfaces, or using the "Fill holes" option under negatives. The option we will use is the "Fill Holes" option as it fills the holes in the surface without creating a new surface and therefore provides a better single surface instead of multiple surfaces.

After selecting the fill hole option, all we have to do is select any hole as shown in the image and click the middle mouse button. We can do this for all the holes and get clean geometry.

In this next step, we will split the single PID model into several different PIDs to link the model more accurately and easily.

To create a new PID, we open the PID manager, add a new PID by clicking the "NEW" option at the bottom of the options, and under the "NEW" option, select "Shell Parameters".

We will create 7 PIDs and to assign each PID to a component, just click on the PID and then click apply, after selecting the desired part to assign the selected PID and press the middle mouse button.

Now we switch to mesh mode from topo mode to mesh the given model.The first thing we need to do is open the mesh parameters (5mm for case 1) from the top options list and inpOnce we are done with setting the parameters, now all we have to do is select the PIDs one by one to mesh them.

We use the length option in the Perimeters option to assign a length to all edges (perimeters) and also to assign a mesh size on surfaces using the "Macros" option. We can cross-check the distance between nodes using a measuring tool.

We have finished setting all the required parameters and now we need to select the network algorithm present in ANSA.

The algorithm we will use is the “Spot Mesh” option. parameters we want to mesh this geometry.

If we see the arrangement on the spring and around the corners of the valve head, we can see that the arrangement is very bad and in the case of the spring, if we measure the diameter of the spring is about 3.4 mm, but the size of our element is 5 mm, and therefore it does not engage the spring properly. So we need to reduce our network size to have a good network.

As we can see by reducing the mesh size, we have improved the quality of the mesh, but we are still not able to properly capture the spring and valve head, so we need to reduce our mesh size even more.