Project 1

AIM:

To check the geometrical errors in the IP Substrate model and convert the given component from three dimensional model to two dimensional by extracting mid surface from the parent geometry and therafter meshing the model with the given quality criteria and thereby devoloping a better mesh flow.

QUALITY CRITERIA:

The Quality criterias used in this model are aspect ratio, warping, skewness, jacobian, minimum length, maximum length,minimum and maximum of quad and tria anglesand tria percentage.

It is the measure of how far element deviates from the original or ideal shape.The shapes are equilateral triangle and square(in mixed format).

• Warping : It simply means out of plane angle.It is the angle between the normal of two planes formed by splitting the quad elements along the diogonal.The acceptable values are 0-15.
• Aspect ratio : It is the ratio of maximum element edge length by min element edge length.Acceptabe values are in the range of less than 5.
• Skewness : 90 degree minus the minimum angle between the lines joining through the oppposite mid sides of the element. (for quad element) and 90 degree minus the minimum angle between the lines of one node and opposite mid side and between the two adjacent mid side of each ode of element.
• Jacobian : It is a scale factor which is used to check the effectiveness of transformation from the global to local co-ordinates.It is acceptable in the range between 0.6-1
• Tria percentage has to be maintained below 5 percent for better mesh flow.

S.No	Quality Criteria	Value
1	Target/Average length	4
2	Minimum Length	2
3	Maximum Length	6
4	Aspect	3
5	Warpage	15
6	Skewness	45
7	Jacobian	0.7
8	Minimum Quad Angle	45
9	Maximum Quad Angle	135
10	Minimum Tria Angle	30
11	Maximum Tria Angle	120
10	Tria Percentage	15

PROCEDURE:

• Convert the .igs file to.ansa file automatically or using the cad translator which can be done manually.
• Change the length of perimeter and macos to unit length to capture the features and planes properly, so that it will be in a refined manner.
• Check for geometrical errors in the model like unchecked faces, needle and junk faces, triple cons formed in the geometry and fix it either manually or automatically.

• After removing all errors, three dimensional model has to be converted into two dimensional by extracting mid surface from the parent geometry.In Ansa, we have the opton of creating it manually or automatically.Mid surface(skin and casting) are the automatic ways of creating the mid in one shot.In areas where features are lot higher the manual mesh is much more suitable which can be achieved using the offset tool in topo module.Note that for using skin and casting, the model should be of closed volume.

• The IP substrate is one of the complex component manufactured in the automobile sector since it has a lot of small features and fillets.The locators are one those part which has to be take of higher care as the mid created should be passing exactly through the middle of it.

• It would be much easier if the mid is taken by cutting the geometry into several parts for convienience using the plane cut tool.After the extraction of mid is complete entire mid generated has to be cross checked with the parent geometry by enabling the parent geometry in transperancy mode and changing from ent to pid mode.

• After ctreating the mid, de-featuring or re-construction of macos has to be done properly to achieve a better mesh flow, avoid trias and rotating quads during the time of meshing.
• The meshing has to be started from the one side and should be meshed in a flow rather than in a random way.First the features or fillets has to be meshed in that purticular area to avoid maximum trias in the surface.
• The meshing is mostly done with the Best tool in mesh module which will maintain the best mesh quality.Spot weld is also used in macro regions where weld points are attached to the surface.

• Reconstruct and smooth option are available in mesh generation and shell mesh options inorder to reconstruct and re-align the model respectivily to get the ideal shape.Reconstruct has to be done only if necessary as it can change the flow of the mesh.
• After meshing all the macros, bringing the unmeshed regions to zero, delete all user cut defeatured lines and again check for opposie trias and rotating quads.Remove as much quality errors as possible and in critical areas like end of locators, the minimum length quality errors have to be kept as such.
• Assign different PID's for parts having varying thickness so that in PID mode it can be identified easily in different colours.Note that when assigning pid the thickness have to be mentioned properly in the pshell table.

• Check for the tria percentage in the geometry,if it is more than five percent, re-work on the model, since 5 percent is the acceptable standard range in industries.
• After finishing the entire model with the above procedures, the last step is to release the model so that the geometry has to be converted into FE model.

LEARNING OUTCOME:

• Learned to extract the mid surface and generate the mesh with better mesh flow in all possible ways.
• Able to handle most of the complex parts in automobile sector.
• Became more handier with most of the different tools in topo and mesh module and able to use more properly wherever necessary.
• Time period to finish the geometry has been reduced much more than in the initial stages.
• Able to reduce the quality errors in the geometry by understanding the concepts behind each of them, thereby knowing what should be done inorder to remove that purticular error.

CONCLUSION:

From the given model of IP Substrate, mid surface has been extracted properly and mesh is generated with better mes flow, with a tria percentage of 3.5 and quality errors formed only in the locators and ribs that are unavoidable.