MESHING OF AN INTERIOR PLASTIC COMPONENT OF A SIDE DOOR IN A CAR BY USING ANSA

AIM:-

1. To Extract the mid-surface manually & mesh the geometry with quality.

2. To Extract mid-surface Automatically and mesh the geometry with quality.

3. Then Finally with the combination of both Extract auto mid-surface and manually mid-surface and then mesh the geometry with quality.

PROCEDURE:-

The following procedure will be followed :

GEOMETRY CLEAN-UP:-

• The imported model is checked for the geometry errors using the checks manager. If there are any errors, it should be corrected and the geometry is made clean.

EXTRACTING THE MID-SURFACE:-

• Then the mid-surface should be extracted.It can be extracted either manually or automatically using appropriate methods.
• It is based on the thickness variation and time constraints.
• In manual method the faces are selected and the offset value is given.
• In automatic method, the mid surface is extracted in a FE model straight form.
• For this the whole part is selected, maximum thickness value,target element size are given in prior.

ASSIGNING PID\'S & THICKNESS:-

• Now the regions with different thickness are assigned with different PID\'s and the thickness values are assigned accordingly.
• This process can also be done by three methods which are again Auto, Manual, & Combination of both the methods.

MESH GENERATION:-

• Then, if the mid surface is a CAD geometry, then the model is meshed with the target element size as Defined.
• Because in Auto method, the extracted mid-surface is already an FE model itself.

MEETING THE QUALITY CRITERIA:-

• Now the mesh elements are corrected to meet the quality criteria specified below:

ELEMENT TYPE : MIXED

TARGET ELEMENT SIZE FOR ALL THE MODELS : 4MM

GEOMETRY CLEAN-UP:-

• When the model is imported, it has a lot of topological errors.
• The model is checked for any errors by checks manager, Hence it is found that there are lot of single cons, triple cons, needle faces & cracks.
• All those errors are corrected systematically one by one.

WIREFRAME MODE

SHAWDOW MODE

PID MODE

AFTER CORRECTION:-

SHOWS AN ERROR FREE MODEL

MID-SURFACE EXTRACTION BY AUTO METHOD:-

• After correcting all the errors, the model is ready to be Mid-skinned, The options used are:

GO TO : TOPO > FACES > MID-SURFACE > CASTING.

• Then the whole model is selected and the target element size is given as 4mm and click ok, Then the middle surface of the whole model is extracted in the FE model as shown below :

• Now the middle surface is checked using the following algorithm

GO TO : TOPO > FACES > MID SURFACE > CHECK MIDDLE SURFACE.

• Now ANSA compares the Extracted mid-surface with the original model, if there is any deviation it will correct automatically.
• To automatically assign PID\'s & appropriate thickness:

GO TO : TOPO > FACES > MID-SURFACE > CALUCULATE THICKNESS.

• By using this algorithm ANSA will automatically detect the areas with the different thickness values and assign those values with separate PID\'s.

• As seen in the above picture, the FE middle surface is assigned with the PID\'s and the thickness values accordingly.

MEETING THE QUALITY CRITERIA:-

• As the mid-surface is alraedy in the form of FE model, now quality criteria is to be specified.
• After assigning, there will be a number of elements OFF since they do not meet the mesh quality specified as below.

• Each one of these should be corrected by using appropriate methods for each criteria. the most commonly used methods are :

• As seen in the above pictures, all the mesh elements are met with quality criteria specified by the user and no elements are OFF.
• This helps in obtaining the accurate results during analysis.

MID-SURFACE EXTRACTION BY MANUAL METHOD:-

• Unlike the auto method in which the whole model is mid-skinned at a go, But in a manual method each face is selected and it is been OFFSET depending upon its thickness by the user manually.

GO TO : TOPO > FACES > OFFSET.

• The mid-surface can be seen as follows:

• The red con which is seen in the middle of the surfaces are the mid surfaces which is OFFSET by the user.
• All these surfaces should be connected in order to form a single model.
• First the base surfaces should be OFFSET and are connected.
• Then the ribs and other projected surfaces are OFFSET and are extened to meet the original mid surface.

GO TO : TOPO > FACES > EXTEND

• The OFFSET ribs can be seen in the below snapshot,

• After OFFSETTING all the surfaces and connecting together, the whole mid-surface is formed as follows.

• After this each surface with different PID and the appropriate thickness values are given by checking the original surface thickness.The model with PID\'s assigned as follows:

MESH GENERATION:-

• Now the mesh is generated with target element size as 4mm using the below algorithm.

GO TO >MESH > MESH GENERATION > BEST > MIXED

• Once the mesh is generated, quality criteria is specified as mentioned earlier.
• Then the elements which are not meeting the quality criteria are corrected and in the end no elements should be OFF as shown below:

MID-SURFACE EXTRACTION BY COMBINATION OF AUTO & MANUAL METHOD:-

• In this method, a different approach is followed, first the whole model is mid skinned as did in the auto method.
• Some of the missing entities and deformed surfaces are OFFSET manually and are connected to previously extracted mid-surface.

GO TO : TOPO > FACES > MID-SURFACE > CASTING.

• Then the whole model is selected and the target element size is given as 4mm and click ok, Then the middle surface of the whole model is extracted in the FE model as shown below:

• As the extracted surface is in the form of FE model, it should be converted to a surface geometry for further processes, To do so, the algorithm used is

GO TO > MESH > ELEMENTS > TO SURFACE.

• Once it is converted to surface geometry, entities like the ribs are manually OFFSET by the user accordingly to the thickness values & then they are connected as shown in below.

• After this PID\'s are assigned properly and thickness values are also assigned.

MESH GENERATION:-

• Now the mesh is generated with target element size as 4mm.
• Then all the elements are corrected to meet the quality criteria as specified.

CONCLUSION:-

• Extracting the mid-surface by Auto method took less than 8 minutes for the whole model and it also saves a lot of time, But the accuracy of the surface captured is very poor.
• On the other hand, when doing it manually, the user can produce the mid surface with best finish and dimensional accuracy, But it takes a lot of time.
• Hence, using the combination of both would be the best choice for mid-surface extraction method Because it saves time & Generate nearly accurate results.

Google drive link:- https://drive.google.com/open?id=19TLTht2zT-rtN6Qn55Q39RnHJ1i2ZADL