Learning Forum

[1617836513]

In the simulation of bolt preload, a torque is applied to the bolt, so how to set up to find the pretention force of the bolted joint.

[Kaushal Vadnere]

Hi Ji Shiyu!

You can calculate the pretension force of the bolt using this formula:

T = K*F*d

Where,
T = Torque in Nm
K = Constant which is usually taken as 0.2 for normal dry conditions,
F = Axial bolt force or pretension force in N
d = Nominal diameter of the bolt in m.

To apply bolt pretension in Ansys Mechanical, you can use bolt pretension object.
Refer to this free Ansys Innovation Course to learn how to setup bolt pretension: Modeling the Bolt and Preload | Ansys Innovation Courses

[1617836513]

Can it only be calculated by a formula? The value calculated by the formula is the theoretical value, can't I get the simulation experimental value in Ansys？I want to do a comparison of the simulation value of the pretention force with the theoretical value. Assuming that instead of applying torque during tightening, I apply a certain angle using remote displacement to tighten the bolt, how should I output the bolt pretention force?

[Kaushal Vadnere]

In that case, you can get bolt pretension force using Force Reaction object.
1. Right click on solution > Insert > Probe > Force Reaction. 
2. In the details of force reaction, Select remote displacement in the boundary condition. See screenshot below
3. Look for Force Reaction in the direction aligned to the axis of bolt, or create a new coordinate system scoping it to the bolt shank and select the new coordinate system in the orientation.

Alternate method,
Drag and drop remote displacement on solution and this will automatically create a Force Reaction object.

[1617836513]

Thank you. What you are saying is that the bolt pretention is the reaction force corresponding to the boundary condition. So if I apply a moment to a surface of a bolt, is the reaction force in the axial direction on that surface the preload force corresponding to that torque?

[Kaushal Vadnere]

 

Well, Force Reaction is force equivalent of displacement, i.e. how much force is required to obtained the defined displacement. This works on similar principal as spring force, F = K*x, where F is the force, K is stiffness and x is displacement. if you know stiffness K & displacement x, you can calculate force F.

Force Reaction does not support moment boundary condition. The moment itself means force applied at distance so, force reaction for moment does not make sense. 
Similar to Force Reaction object, you can also use moment reaction object to obtain moment for applied remote displacement.

Refer to this article in Ansys help for more details on force & moment reactions and which boundary conditions are supported: 19.5.19.3. Reactions: Forces and Moments (ansys.com).