# Suspension Upper Arm Analysis. Static or Transient Structural ?

Member

Hi, I'm new on finite element analysis and I'm confused whether the attached simple suspension upper arm model should be analyzed as static structural or transient structural. When I analyse the real world situation it gives an insufficient bc error because of cylindrical support. How should I analyse it? Thank you.

• Member
edited November 2019

Please insert your images into the post as I have done below.  ANSYS staff are not permitted to open attachments.

There are insufficient BCs because two cylindrical supports leaves the arm with two DOF, axial freedom along the two cylindrical supports, and rotational freedom around the axis.

Change one of the Cylindrical Supports to Simply Supported to take out the axial freedom. Add a Remote Displacement on the spring Pad to fix at zero, the one displacement along the spring length. That will take away the rotational DOF.  Now the applied force can induce some stress into the part.

• Member
edited November 2019

Thanks for your reply.. I just didn't understand to change of the cylindrical support... I added cylindrical support as fixed on axial and radial directions.. isn't it same thing with simple support.. Besides you mean fixed support with simply support ?

Briefly I want to constrain XYZ translation on cylindrical support region and just make free axial rotation as it is in real world.. Which kind of support should I use?

• Member
edited November 2019

A cylindrical support fixed on Axial and Radial is like a Revolute joint and is as good as Simply Supported on one end to prevent an unsupported axial DOF.

You could have a spring on one side and a force on the other, but it is simpler to replace the spring with a Remote Displacement and just apply the force. The stress in the part will be the same unless the part rotates a large angle. If that happens, the force doesn't follow, so it depends on what is really happening.

• Member
edited November 2019

This is simple suspension upper arm. There are revolute joint (bushing) where placed remote dipslacement.. I added remote displacement on bushin places like at image. And added remote displacement on dumper face , it's only constrained on spring logitudinal axis.  Is this right modeling?

• Member
edited November 2019

Please include a coordinate triad in the image so I know which direction is x, y and z.

• Member
edited November 2019

• Member
edited November 2019

Looks good.

• Member
edited November 2019

Thank you so much Peter.

• Member
edited November 2019

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