Project - 2 - Meshing on the suspension Assembly

OBJECTIVE:

The main aim of this project is to perform meshing on the given Cad model of the suspension system as per the quality criteria shown below and to provide necessary connections.

QUALITY CRITERIA:

For Surface Meshing of Tyre and Rim (Element type: Tria) : 

For Surface Meshing of Non-Uniform thickness components other than Tyre and Rim (Element type: Tria) :

For Volume meshing of all Non-Uniform thickness components (Element type: Tetra Elements): 

For Mid surfacing of Uniform thickness part which has a thickness less than 5 mm (Element type: Mixed elements) :

PROCEDURE:

GEOMETRY CLEAN UP:

• Imported the given.IGS  file in the ANSA work page.
• Checked for the orientation i,e. the upper part of the model should be in gray color meaning positive and the lower part in yellow color meaning negative.
• The issues with orientation are cleared using the topo module-->faces-->topo.
• The resolution of the CONS is improved using Auxiliaries--> fine from topo module or perimeters-->length from mesh module. 
• The model is then subjected to a geometry checkup to check any free edges between the models, duplicate surface, irrelevant CONS using the option tools--> checks-->geometry.
• Some geometrical errors are cleared using the Auto fix option and some are manually done using options like release hot points, release cons, topo, faces cut, etc. from the Topo module.
• Normally, it is recommended to use 3D meshing for the casting components and also for the components that exceed the thickness of 5 mm.
• The model is then segregated by assigning an individual property for each part as shown below and is done by using set PID from topo module-->faces.
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MIDSURFACE EXTRACTION:

• It is recommended to use planar meshing for the components whose thickness is below 5 mm, by using the measure option from utilities, the below-shown components are decided for 2D meshing.
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• Since the thickness of the parts remains constant, extracted the mid surface using the topo module-->faces--> mid surface--> skin, while keeping the parent geometry not getting deleted.
• Geometry check-up is done and a property ID is created with their respective thickness.
• By default, ANSA creates a steel material ID, which is defined so that the material is assigned to the model.

• The surfaces are split accordingly to attain good mesh flow and to avoid element failures using mesh module--> macros-->cut option. 

PLANAR MESH GENERATION:

• The Quality criteria are applied to the model using utilities--> Quality criteria as shown below,
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• Mesh parameters are applied as shown below, using utilities--> mesh parameter.
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• The perimeter elemental length is applied to the model using the mesh module --> perimeter--> length option.
• The split surfaces are meshed one by one using mesh module--> mesh generation--> Best option.
• During meshing the opposite trias, back to back trias, tias present at the edges, rotational quads can be removed using shell mesh--> reconstruct option.
• Trias present at edges, fillet areas, pattern formation, opposite trias can be avoided using split, swap, reconstruct, edge2 perimeter, Num +/- options.
• The elements which fail for quality can be viewed by using the Draw mode toolbar --> hidden option and corrections are done for the elements which fail for quality.
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THICKNESS ASSIGNMENT:

• By measuring the varying thicknesses, property Ids are created with the thickness values and assigned to the model.
• The thickness assigned to the model can be viewed using utilities--> quality criteria--> presentation parameters --> Draw shell as solid.
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VOLUME MESH GENERATION:

• The surface of the solid model has meshed with tria elements and then it is converted into 3D elements.
• The Quality criteria are applied to the model using utilities--> Quality criteria as shown below,
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• Mesh parameters are applied as shown below, using utilities--> mesh parameter.
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• The perimeter elemental length of 4 mm and 6.5 mm is applied to the model using the mesh module --> perimeter--> length option.
• The split surfaces are meshed one by one using mesh module--> mesh generation--> Best and spot mesh option.
• Normal trias and ortho trias elements are used while meshing the surfaces.
• The curved surfaces and fillet regions have meshed with ortho tria elements for better feature capturing and Normal tria elements are used in the plane surfaces.
• The ortho tria elements alone can be used to mesh the model but the number of elements increases, so the computation time increases.
• During meshing the irregular mesh flow can be removed using shell mesh--> reconstruct option.
• The elements which fail for quality can be viewed by using the Draw mode toolbar --> hidden option and corrections are done for the elements which fail for quality.
• The smooth-->shell mesh option is used to attain good mesh flow.
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• After the shell mesh and checking for quality criteria, ensuring that the model is fully closed, it can be taken to generate tetra elements.

Tetra elements generation:

• The generation of solid elements can be done with the volume mesh deck.
• The model is defined as a volume with Volume mesh--> volumes -->Define option, so that  ANSA considers the model as a volume to generate solid elements.
• The model has four volumes are defined as shown below, this can be viewed with the volumes-->list option.
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• The solid elements are generated using the unstructured-->mesh--> Tetra rapid or Tetra FEM option.
• Difference between Tetra rapid and Tetra FEM option: 
  • Tetra rapid option meshes the volume with Tetra elements.
  • Tetra FEM option creates a Tetrahedral mesh inside selected Volumes, initially with pyramid elements if the starting surface mesh contains quad elements. It is to be used mainly for structural applications.
  • In Tetra FEM, the generation of tetra elements is greater than with the tetra rapid option. so, the computation time increases with the Tetra FEM option.
• After the generation of the solid elements, the quality parameter Tetcollapse is checked for mesh quality.
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• The elements which fail for Tetcollapse can be resolved using improve-->fix quality option unless there are dents or peaks formation.
• Tetcollapse can be manually resolved using mesh-->grides-->move free option.
• Once it is completed, the solid model can be viewed using the Visibility toolbar --> volume option.
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• All the volume meshed components are shown below,
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1D MESHING:

• In this model suspension system, the 1d meshing is carried out to the suspension spring element.
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• firstly, a curve is created in the middle of the spring cross-section by using the curves--> middle in the topo module.
• A 3d point is created at the COG of the spring by using the points--> ON COG.
• In the NASTRAN deck, using elements--> CBAR option and by feeding the element size of 3 mm and radius of 5mm, the solid representation of the spring can be created.
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• The solid representation can be viewed by enabling line elements cross-section with as solids turned ON.
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CONNECTION:

• In order to connect the model with appropriate connections, here the bolt and seam weld connections are used.

Manual Bolt connection:

• The bolts can be represented as rigids, it can be modeled with RBE2 elements.
• Bolt connections are provided to the holes, where the parts are to be connected with bolts.
• That can be identified when the part holes are located next to each other.
• It is recommended that the bolt representation to the holes can be captured using a washer split of one layer.
• Generally, bolts can be represented as cluster RBE2 as well as two-node RBE2 connecting the master nodes of spider RBE2s.
• Generally, these bolt representations are done manually using Nastran deck>elements>RBE2.
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Seam connection:

• Seam weld is used to connect the parts in a continuous seam line.
• It provides more structural rigidity to the system.
• To generate seam weld, the seam data has to be obtained and then a curve is created along the length to represent the seam length.
• Then the curve has to convert into a seam line using the assembly toolbar convert>curves> seam line.
• Then the seam line can be realized using connection manager from assembly toolbar and inputs are provided as shown below,
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•                                              Control Manager for Seam Weld Connection-y-joint 
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•                                           Control Manager for Seam Weld Connection-Overlap joint
• The seam weld representation as follows,
• Basically, if the parts are parallel to each other, then the FE rep type has to chosen as an overlap shell.
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• Finally, The elements are mirrored and saved the model.

RESULT:

Hence,

• The given suspension system has meshed with the appropriate mesh elements as per the quality criteria.
• Thickness is assigned to the 2d shell elements.
• Appropriate connections are provided between the components.

MODEL:

LINK TO VIEW THE MODEL:

SUSPENSION ASSEMBLY