Project 2

AIM:

To create the volumetric mesh and two dimensional mesh for the given model of rear suspension with strut and lower arm assembly and to generate the appropriate connection inorder to make the entire model rigidized.

REAR SUSPENSION:

The rear suspension of a vehicle performs the same general function as front suspension, but the specific construction is typically quite different.The most basic purposes of a suspension system are to prevent the body of a vehicle from hitting the ground and to keep the tires in contact with the road.­The suspension of a car is actually part of the chassis, which comprises all of the imp­ortant systems located beneath the car's body.

COMPONENTS OR PARTS:

The four major components that are comprised together to form the rear suspension of a car are:

• Frame: Structural, load-carrying component that supports the car's engine and body, which are in turn supported by the suspension
• Suspension system: Setup that supports weight, absorbs and dampens shock and helps maintain tire contact
• Steering system: Mechanism that enables the driver to guide and direct the vehicle
• Tires and wheels: Components that make vehicle motion possible by way of grip and/or friction with the road

In this, suspension system consist of different assembly parts which are joined together to form the suspension system.The main parts are as follows:

• Steering Knuckle: Provides a spindle or bearing support for the wheel hub, bearings and wheel assembly. In the given model the knuckle is used to connect the strut,brake calliper, lower arm and the tie rod which is connected to the steering system.

• Lower Control arm: A movable lever that fastens the steering knuckle to the vehicle frame or body.There are lower and upper arm depending upon the type of suspension used.

• Ball joint: A swivel joint that allows the control arm and steering knuckle to move up and down, as well as side to side.

• Suspension or coil spring: This is the most common type of spring and is, in essence, a heavy-duty torsion bar coiled around an axis. Coil springs compress and expand to absorb the motion of the wheels.

• Sway bar: These are used along with shock absorbers or struts to give a moving automobile additional stability.It spans alongs teh entre xle and effectivily joins each side of suspension together.These are also called stabilizer bar or anti-roll bar.

• Shock absorbers: It is a device that controls unwanted spring motion through a process known as dampening. Shock absorbers slow down and reduce the magnitude of vibratory motions. The upper mount of the shock connects to the frame (i.e., the sprung weight), while the lower mount connects to the axle, near the wheel.

• Strut: it is basically a shock absorber mounted inside a coil spring. Struts perform two jobs: They provide a dampening function like shock absorbers, and they provide structural support for the vehicle suspension.

MacPherson Strut: This is the suspension that has been used in the cad model.This type of independent suspension is similar to the double wishbone except that the upper arm is rotated up and replaced with a long member called the “strut”. The strut incorporates the spring and shock in a concentric package and attaches to mounts high on the vehicle. This design adds more room for packaging front engine/transmission modules and adjoining drive shafts.

METHODOLOGY:

• Geometry check and error correction.
• PID seperation for all seperate parts.
• Surface meshing or two dimensional meshing as per the criteria.
• Creating volume or tetra meshing the three-d meshed components.
• Generating appropriate connections.

QUALITY CRITERIA:

Quality Criteria for Tria Elements (Tyre and Rim):

S.No	Quality Criteria	Value
1	Target/Average length	6.5
2	Minimum Length	5
3	Maximum Length	10
4	Skewness	45

Quality criteria for Mixed elements (For Midsurface only):

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

Quality criteria for Tria (For other components):

S.No	Quality Criteria	Value
1	Target/Average length	4
2	Minimum Length	2
3	Maximum Length	6
4	Skewness	45

Common Quality Criteria for Tetra elements are:

S.No	Quality Criteria	Value
1	Tet-collapse	0.2

PROCEDURE:

• The given cad model has to be converted from .igs to .ansa format by default or using the cad translator tool available along with the software.
• After understanding the model and given question properly, start to work on the model as per the criteria.
• First, start with the geometry check of the given model of rear suspension fro the checks manager.
• Note that before going for the geometry check the model, the suspension assembly parts have to be seperted with the help of PID region tool.This makes it helpful to check the later procedures easily.

• Check for errors in each and every parts and remove all errors in the puricular part and later mesh generation can also be done seperately.
• After removng all errors check or inspect the part dimension, as all parts above 5mm thickness has to be tetra meshed and volume should be created and parts with less tahn 5mm with uniform thickness has to be 2D meshed and mid surface has to be extracted.
• Note that the quality criteria are different for parts in the suspension system.Here tyre and wheels have seperate QC while suspension assembly have another QC.
• Start with the tyre and rim or vice-versa, defeaturing or reconstruction has to be done to avoid the minimum length error in the model.In those areas datch->divide faces tool can be used to create a centre line through curved fillets etc.
• Once de-featring is finished, after giving proper quality criteria, start the surface meshing using the ortho tria or tria element type.The meshing can be done manually or automatically with the batch mesh generation tool.or this. the required part which has to be meshed has to be updated in the model browser seperately.

• After that in the batch mesh new meshing scenario has to be created with the corresponsing quality criteria, click the run button. After the execution is complete the message is shown completed with an exclamation mark.This means quality errors have been formed in th model.
• If the batch mesh is done,check for the de-faturing of the macos as ansa devolops many abrupt cuts in the model which are not acceptable and rework on that regions.
• On two or three components the 2d meshing has to be generated.Using offset extract the mid surface and mesh the element with mixed and with the given Quality criteria and remove trias as much as possible.

• Remember that 2D and 3D meshing cannot be combined in a single part.
• For the parts which are surface meshed, volume has to be created inside the geometry.Note that the volume can be created only in a closed volume region.
• In the volume mesh, first define the volume by manual way.In the volume list we can see the volume undefined and unmeshed.The volume can be meshed with the help of tetra rapid or tetra fem method.

• The errors which may be formed can be checked using the checks manager.In the checks manager there is a templete called surface mesh checks cfd. All the penetrations and intersections can be solved with this option.

• After creating the volume PID has to be created in the PSOLID format by using the set pid option.Check for the tet-collapse error in quality criteria of solid section and remove all of them.

• After the volume being created to all surface meshed parts, set all of it into a single pid.

• Rbe-2 as well as cluster connection has to be given in model (bolt areas) wherever necessary inorder to make it rigidized.

LEARNING OUTCOME:

• Learned to surface mesh the casted elements without any quality errors formed
• Able to recognise the parts which has to be meshed either by 2-d or 3-d mesh to be used.
• Able to create a better surface mesh with the given quality criteria without any kinks or dents in the volume created.
• Able to finish the model within the constrained time.

CONCLUSION:

The combined geometry made with surface meshing as well as two dimensional meshing has been meshed with the given quality criteria and proper connections have been deployed in the bolt regions inorder to make it rigidized.