week-11 Joint creation and Demonstration

AIM:

To create various joints such as revolute, spherical, translational, rotational, locking, cylindrical between two rigid and deformable bodies and simulate their relative motion between the bodies.

Procedure:

Spherical Joint between two rigid bodies:

1. A ball and socket model has been created using ANSA and it is imported to ls dyna.
2. The unit system used in kg/mm/ms
3. The socket is a sheet metal part with 2mm thickness and the ball is a solid part which is model as outer mesh with 1mm thickness and section card is created accordingly.
4. 
5. Mat_20 rigid card has been created and assigned for both the parts.
6. 
7. To create a node at the cetre use Element tool>node editing>Create and select the avg centre option to create a node at the centre and similarly for another part.
8. 
9. Note the node id and go to Constrained>extra nodes>enter the node id and select the pid element and apply similarly for the another part.
10. 
11. Now go to Constrained>joint spherical>select n1 and n2 (which is the constrained extra nodes that we have created respectively for two parts)>accept and ok.
12. 
13. Now to apply velocity for socket go to initial>velocity_rigid_body>Select the pid>Enter the initial rotational velocity in x,y and z directions.
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15. Now Database>binary d3_plot for recording the animation.
16. 
17. Define control termination to specify the end time of the simulation.
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19. Define control time step card to give initial time step size and TSSFAC as 0.9 so that if any fluctuation, model will converge.
20. 
21. Now run the model using ls run and open the d3 plot file.
22. 

Spherical joint between two deformable bodies:

• Since the bodies are deformable, elastic material is used.
• So to create a joints, we need rigid bodies and we are going to create a Constrained Nodal Rigid bodies on ball and socket part.
• Go to create entities>Constrained>Nodal rigid body>Check on CreatePNode option(will create node at the centre)>similarly for the other part.
• 
• 
• Now that both the centers of the CNRB should be concident. Now go to Create entities>constrained>spherical>Selent the n1 and n2 as the centre of two CNRBs and apply>done.
• 
• Since it is a deformable body, We need to fix either the ball or socket end. Go to create entities>boundary>spc>select the nodes>apply.
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• To give velocity to the socket create node set and go to Control>velocity generation>To select part set id enter 1 in STYP column and give OMEGA as 1 and give velocity in x and y direction.
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• The Remaining cards such as Control>termination,Time step, Database>binary d3plot, are similar to the rigid body model. You can open it in notepad++ and copy and paste and reload the model.
• Result:
• 

Revolute joint:

• A two sheet metal plate has been created using ansa and it is imported to ls dyna. Both are deformable bodies so a CNRB has been created using Create entities>Constrained>nodal_rigid bodies.
• 
• Use modify option to create a branch from Both CNRBs to their COG point. So that node pair (1,2) are coincident and (3,4) are coincident. Node 1 and 3 belongs to part A and Node 2 and 4 belongs to part B.
• Now go to create entities>constrained>joints>Revolute>select the four nodes in order as explained above and apply, done.
• 
• Now one of the plate is fixed in all direction and the other is fixed in y direction so that it won't go out of plane x_z.
• Go to Create entities>boundary>spc>Select the plate a and fix all and other plate in x and z directions.
• 
• 
• The Remaining cards such as Control>termination,Time step, Database>binary d3plot, are similar to the Spherical model. You can open it in notepad++ and copy and paste and reload the model.
• Simulation of Revolute joint:
• 
• Similarly for revolute joint between two rigid bodies, create rigid material and assign and create CONSTRAINED EXTRA NODE pairs respectively and create join as explained above.

CYLINDRICAL JOINT:

1. A solid and a hollow cylinder has been modelled and imported to ls prepost.
2. To define a Cylindrical joint between a rigid and deformable part, here solid part is considered as a rigid part and the hollow cylinder is considered as a deformable part.
3. Section card has been created accordingly for shell and solids.
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5. 
6. 
7. Create Entities> CNRB for the hollow cylinder and Constrained_extra_nodes for the solid cylinder.
8. The node pair 1,2 and 3,4 are on the center line similar to revolute joint. Node 1 and 3 belongs to solid part and node 2 and 4 belongs to hollow cylinder.
9. 
10. Now the Hollow cylinder is fixed in all the direction using create entities>Boundary>spc>all_fix>select nodes>apply>done.
11. 
12. Now the solid part is applies with 10mm/ms in y direction using velocity creation card.
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14. The Remaining cards such as Control>termination,Time step, Database>binary d3plot, are similar to the Spherical model. You can open it in notepad++ and copy and paste and reload the model.
15. Similation of Cylindrical model:
16. 

Translational Joint:

1. A solid cuboid and a hollow cube has been modelled and imported to ls prepost.
2. Now a constrained rigid body has been created using Create entities>Constrained>nodal_rigid_body.
3. The CNRBs of two bodies are branched in a way that node pair 1,2 and 3,4 forms a centre line and 5,6 should be branched which should not be in the centre line. node 1,3 and 5 belongs to part a, nodes 2,4,6 belongs to part b.
4. 
5. Now the translational joint has been created using create entities>joints>select 6 nodes in oder as explained above.
6. 
7. Now the hollow cube is constrained in all the direction using create entities>Boundary>spc>all fix>apply>done.
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9. Now the velocity has been given to solid cuboid part using Initial>velocity_generation>select the part id>give velocity in x and z direciton.
10. 
11. The Remaining cards such as Control>termination,Time step, Database>binary d3plot, are similar to the Spherical model. You can open it in notepad++ and copy and paste and reload the model.
12. Simulation of Translational joint:
13. 

CONCLUSION:

Thus various bodies has been developed defined as elastic and deformable bodies and joints such as spherical, relative, translational, revolute had been created and simulated successfully.