Ansys troubleshooting

[John Lankes]

I am currently working on adding the suspension and associated components onto our Ansys frame model, and I am running into a few problems that I have been unable to resolve. The base model of the frame consists of beam 188, and I would like to add A-arms using Spar8 elements, and eventually the rocker joint with the Combin7.

The main problem is when I run the model with the A-arms as Spar8 elements, the displacement in the arms reaches the maximum for Ansys and stops the model. When the A-arms are modeled as Beam 188 elements, the model runs fine, but as soon as they are switched to trusses the model messes up.

Truss stiffness is turned up to 1e9, and the pushrod is still modeled as a beam element with high stiffness as well, to constrain the wheel movement. The rear frame is constrained in all DOF, and I have a pair of opposing 500lbs forces applied at the front wheel to simulate a 1000-lb couple force. I have checked the 3-d display and element lists to make sure the correct sizes, and real constant sets are applied to the correct elements.

Any help would be greatly appreciated.

[John Lankes]

I am currently working on adding the suspension and associated components onto our Ansys frame model, and I am running into a few problems that I have been unable to resolve. The base model of the frame consists of beam 188, and I would like to add A-arms using Spar8 elements, and eventually the rocker joint with the Combin7.

The main problem is when I run the model with the A-arms as Spar8 elements, the displacement in the arms reaches the maximum for Ansys and stops the model. When the A-arms are modeled as Beam 188 elements, the model runs fine, but as soon as they are switched to trusses the model messes up.

Truss stiffness is turned up to 1e9, and the pushrod is still modeled as a beam element with high stiffness as well, to constrain the wheel movement. The rear frame is constrained in all DOF, and I have a pair of opposing 500lbs forces applied at the front wheel to simulate a 1000-lb couple force. I have checked the 3-d display and element lists to make sure the correct sizes, and real constant sets are applied to the correct elements.

Any help would be greatly appreciated.

[Will Steed]

I would not use a Spar8 element or Combin7. You need to keep the model as simple as possible. Plus it sounds like you are not all that familiar with Ansys. How do you have the a-arm joints modeled? What kind of contraints are you using? It sounds like the a-arms are flying off into space.. This would be a constraint issue. Is it only flying off in one direction? My email is steedwt@email.uc.edu if you want faster responses. You should be able to figure it out if you can get Ansys to spit out a bad results file (99999)... Personally I would start off by modeling the a-arms as a 2-d beam. Here is a thought. Run a small test case on just the a-arm..

[John Lankes]

To answer your questions, the A-arm joints are not modeled, the idea is that the Link8 (not Spar8-my mistake) only transmits axial forces, and does not trasmit bending forces making it possible to avoid the spherical. The frame is held at 4 points in all DOF at the rearmost box, alternatively I have held it at the rear of the front box to check if there was a problem deflecting through the frame.

I do not think the Arms are completely seperating from the frame, as the
node that violates the max displacement is halfway down the A-arm. Although I will check this in the model again.

I am starting with just the one corner of the suspension, and trying to get the Link8 element
to work before integrating the Combin7 on the rocker, and the remaining 3 corners of the car. I will try the 2-D beam and see if that works.