week-11 Joint creation and Demonstration

Translational Joint:

A Translational joint provides a linear sliding movement between two bodies. This is a cylindrical joint with the third pair of off-centerline nodes which restrict rotation. Aside from translation along the centerline, the two rigid bodies are stuck together.

Procedure:

The different types of joints are created between two rigid bodies in LS-DYNA using the keyword *CONSTRAINED_EXTRA_NODES and between two deformable bodies using *CONSTRAINED_NODAL_RIGID_BODY

• Joints between Two Rigid Bodies:

 Spherical Joint:

•  Open LS-PrePost, using options under Element and Mesh->Shape Mesher-> Entity->Sphere Shell, create two parts as shown in the below figure. The elements of the outer sphere shell are deleted using option Element editing to get the necessary shape.

•  The material and section are assigned to the parts. For material, the *MAT_RIGID card is used.

•  A pair of nodes is created using the option under Element Tools->Node Editing->Create, i.e node 305 and 306. Node 305 is constrained to part 1 and node 306 to part 2 using *CONSTRAINED_EXTRA_NODES card as shown in the below images.

• The spherical joint is created using *CONSTRAINED_JOINT_SPHERICAL card with one node pair i.e node N1 is 305 for part 1 and Node N2 is 306 for part 2.

The initial velocity of 20 mm/ms is assigned to the moving part in the rotational X, Y, Z-axis.

• The *CONTROL_TIMESTEP Card is activated with the value of the Initial time step size (DTINIT) is set as 0.01 ms.

• The *CONTROL_TERMINATION is given with termination time is set as 5 ms.

• The keyword file is saved using the suitable name with the ‘.k’ extension and made to run in LS-DYNA run.

Revolute Joint:

•  Open LS-PrePost, using options under Element and Mesh->Shape Mesher-> Entity->4N Shell, create two parts as shown in the below image.

• The material and section properties assigned to the parts are the same as that of the spherical joint.
• Two pairs of nodes are created using the option under Element Tools->Node Editing->Create, i.e node 101-102 and 103-104. The nodes 101 and 103 are constrained to part 1 and nodes 102 and 104 to part 2 using *CONSTRAINED_EXTRA_NODES card as shown in the below image.

•  The revolute joint is created using *CONSTRAINED_JOINT_REVOLUTE card with nodes N1 and N3 of part 1 and nodes N2 and N4 of part 2.

• The nodes of part 1 as shown in the below image are constrained in all degrees of freedom.

• The *BOUNDARY_PRESCRIBED_MOTION_NODE card is given at the node on part 2 as shown in the image given below. Also, the LCID or curve ID is given.

• The control timestep is defined using the LCTM curve as shown below image.

• The termination time is set to 10 ms. The keyword file is saved using the suitable name with the ‘.k’ extension and made to run in LS-DYNA run.

 Cylindrical Joint:

• Open LS-PrePost, using options under Element and Mesh->Shape Mesher-> Entity->Cylinder Shell, create two parts as shown in the image given below.

•  The material and section properties assigned to the parts are the same as that of the spherical joint.
• Two pairs of nodes are created using the option under Element Tools->Node Editing->Create, i.e node 321-322 and 323-324. Nodes 321 and 323 are constrained to part 1 and nodes 322 and 324 to part 2 using the *CONSTRAINED_EXTRA_NODES card.

The cylindrical joint is created using *CONSTRAINED_JOINT_CYLINDRICAL card with nodes N1 and N3 of part 1 and nodes N2 and N4 of part 2.

• The initial velocity of 10 mm/ms is assigned to part 1 in the X-axis.

• The value of the Initial time step size (DTINIT) is set as 0.01 ms which is the same as the spherical joint. The termination time is set as 5 ms. Finally, the keyword file is saved using a suitable name with the ‘.k’ extension and made to run in the LS-DYNA run.

Translational Joint:

• Open LS-PrePost, using options under Element and Mesh->Shape Mesher-> Entity->Box Shell, create two parts as shown in the image given below.

• The material and section properties assigned to the parts are the same as that of the spherical joint.
•  To define the Translational joint three pairs of nodes are created. Using the option under Element Tools->Node Editing->Create, two pairs of nodes are created 1001-1002 and 1003-1004 which is coincident and collinear. The third pair 1005-1006 is coincident and slightly away from the axis of the other two pairs but in-between the two pairs. The nodes 1001, 1003, and 1005 are constrained to part 1 and nodes 1002, 1004, and 1006 to part 2 using *CONSTRAINED_EXTRA_NODES card.

• The translational joint is created using *CONSTRAINED_JOINT_TRANSLATIONAL card with nodes N1, N3 and N5 of part 1 and nodes N2, N4, and N6 of part 2.

•  The initial velocity of 10 mm/ms is assigned to part 1 in the X-axis same as the cylindrical joint.
• The value of the Initial time step size (DTINIT) is set as 0.01 ms which is the same as the spherical joint. The termination time is set as 5 ms. Finally, the keyword file is saved using a suitable name with the ‘.k’ extension and made to run in the LS-DYNA run.

 Joints Between Two Deformable Bodies:

The steps required to create a joint between two deformable bodies are the same as that of rigid bodies except few changes i.e,

• *MAT_ELASTIC material card is used instead of *MAT_RIGID card.
•  Instead of using *CONSTRAINED_EXTRA_NODES card *CONSTRAINED_NODAL_RIGID_BODY (CNRB) is used to constrain the nodes to the necessary part.
•  The initial velocity is assigned using *INITIAL_VELOCITY card instead of *INITIAL_VELOCITY_RIGID_BODY card.

 Spherical Joint:

•  The parts for spherical joint are created and assigned with section and material properties similar to the spherical rigid joints, but the *MAT_ELASTIC card is used instead of the rigid one.

• Using Create Entity>>Constrained>>Nodal Rigid Body (CNRB) option the nodes generated are linked between two deformable parts for creating a spherical joint.
•  The spherical joint is created using *CONSTRAINED_JOINT_SPHERICAL card with one node pair i.e node N1 is 305 for part 1 and Node N2 is 306 for part 2.

•  The initial velocity of 20 mm/ms is assigned to the moving part in the rotational X, Y, Z-axis same as spherical rigid joints.
•  The value of the Initial time step size (DTINIT) is set as 0.01 ms which is the same as the spherical joint. The termination time is set as 5 ms. Finally, the keyword file is saved using a suitable name with the ‘.k’ extension and made to run in the LS-DYNA run.

 Revolute Joint:

•  The parts for the revolute joint are created and assigned with section and material properties, but the *MAT_ELASTIC card is used instead of the rigid one.
•  Two pairs of nodes are created using the option under Element Tools>>Node Editing>>Create, i.e node 101-102 and 103-104. The nodes 101 and 103 is constrained to part 1 and nodes 102 and 104 to part 2 using *CONSTRAINED_NODAL_RIGID_BODY under the create Entity option.
•  The revolute joint is created using *CONSTRAINED_JOINT_REVOLUTE card with nodes N1 and N3 of part 1 and nodes N2 and N4 of part 2. The nodes of part 1 are constrained in all degrees of freedom using boundary SPC set and boundary prescribed motion is assigned to node 173 similar to revolute rigid joints.

• The control timestep is defined using the LCTM curve same as the rigid revolute joints and the termination time is set as 10 ms.
•  Finally, the keyword file is saved using a suitable name with the ‘.k’ extension and made to run in the LS-DYNA run.

 Cylindrical Joint:

•   The parts for the cylindrical joint are created and assigned with section and material properties, but the *MAT_ELASTIC card is used instead of the rigid one.
• Two pairs of nodes are created using the option under Element Tools>>Node Editing>>Create, i.e node 321-322 and 323-324. The nodes 321 and 323 are constrained to part 1 and nodes 322 and 324 to part 2 using *CONSTRAINED_NODAL_RIGID_BODY under the create Entity option.
•  The cylindrical joint is created using *CONSTRAINED_JOINT_CYLINDRICAL card with nodes N1 and N3 of part 1 and nodes N2 and N4 of part 2.

• The initial velocity of 10 mm/ms is assigned to part 1 in the X-axis same as the rigid cylindrical joint.
•  The value of the Initial time step size (DTINIT) is set as 0.01 ms which is the same as the spherical joint. The termination time is set as 5 ms. Finally, the keyword file is saved using a suitable name with the ‘.k’ extension and made to run in the LS-DYNA run.

 Translational Joint:

• The parts for the translational joint are created and assigned with section and material properties, but the *MAT_ELASTIC card is used instead of the rigid one.
• To define the Translational joint three pairs of nodes are created. Using the option under Element Tools>>Node Editing>>Create, two pairs of nodes are created 1001-1002 and 1003-1004 which is coincident and collinear. The third pair 1005-1006 is coincident and slightly away from the axis of the other two pairs but in-between the two pairs. The nodes 1001, 1003, and 1005 are constrained to part 1 and nodes 1002, 1004, and 1006 to part 2 using *CONSTRAINED_NODAL_RIGID_BODY under the create Entity option.
• The translational joint is created using *CONSTRAINED_JOINT_TRANSLATIONAL card with nodes N1, N3, and N5 of part 1 and nodes N2, N4,   and N6 of part 2.

• The initial velocity of 10 mm/ms is assigned to part 1 in the X-axis same as the rigid translational joint.

• The value of the Initial time step size (DTINIT) is set as 0.01 ms which is the same as the spherical joint. The termination time is set as 5 ms. Finally, the keyword file is saved using a suitable name with the ‘.k’ extension and made to run in the LS-DYNA run.

JOINTS BETWEEN TWO DEFORMATION BODIES:

CYLINDRICAL DEFORMABLE:

REVOLUTE DEFORMABLE:

SPHERICAL DEFORMABLE:

TRANSLATIONAL DEFORMABLE:

JOINTS BETWEEN TWO RIGID BODIES:

CYLINDRICAL RIGID:

REVOLUTE RIGID:

SPHERICAL RIGID:

TRANSLATIONAL RIGID:

CONCLUSION:

• The keyword files necessary to demonstrate spherical, revolute, cylindrical, and translational joints between two rigid bodies using the *CONSTRAINED_EXTRA_NODES card in LS Pre-Post.
• Also, the keyword files necessary to demonstrate spherical, revolute, cylindrical, and translational joints between two deformable bodies are created in LS Pre-Post using the *CONSTRAINED_NODAL_RIGID_BODY card.
• Finally, we have simulated all joints for two rigid bodies and two deformable bodies using the LS-Run. We also obtained the animations for all the joints for both rigid bodies and deformable bodies.