## General Mechanical

#### Transient Structural analysis?

• Vanderbezi
Subscriber

Hello,

I have a problem as i am new to Ansys. I am doing an Analysis of a crankschaft to determine its torsional stiffness under different boundary conditions.

is the "Transient structural analysis" the right analysis if i want to simulate the crankshafts working conditions for a period of 720° with all the forces from the pistons? or are other analysis types like "dynamic analysis" more appropriate for this use?

regards,

Bezi

• peteroznewman
Subscriber

Hello Vanderbezi,

If you are new to ANSYS, I recommend you begin with a Static Structural analysis. You can apply the peak force from a piston onto the bearing face of the crankshaft at the correct angle, and repeat this for each piston. The end of the crankshaft that goes into the transmission would have a fixed rotation for the reaction torque to be developed.

Regards,
Peter

• Vanderbezi
Subscriber

Hello Peter,

thank you for your response. a few questions furthermore are:

1- Do you mean with "fixed rotation": DOF = 0 ?

2- If I allow only rotation on 1 axis for the main bearings(Journals) and set the other 5 dof to 0, would that be considered over-constraining the model for the stiffness analysis?

Regards,

Vanderbezi

• peteroznewman
Subscriber

Hello Vanderbezi,

You can use two Bearing Supports to hold the crankshaft at the bearing faces that connect it to the engine block. Two bearings spaced along the crankshaft take away 4 DOF.

If you create a Remote Displacement on the end of the crankshaft that connects to the gearbox, you can set the axial displacement to zero and the rotation about the axis to zero, so with those 2 DOF added to the 4 DOF from the bearings, you have an exactly constrained crankshaft.

Regards,
Peter

• Vanderbezi
Subscriber

Hello Peter,

in a transient analysis with a remote displacement at the gearbox end with the angle at given time steps. and with the loads on the crankschaft(right angle and force). is that then considered over-constraining the model?

regards,

Bezi

• peteroznewman
Subscriber

No, that is not overconstrained.