ADAMS AutoFlex Torsion Problem

[Drkwing]

I want to verify (or validate) ADAMS' AutoFlex using a simple beam under torsion. Suppose a circular cross sectioned beam with a definite length (My example was Hollow Section with Outside Dia: 60mm; Inside Dia:40mm; Length:1.5m). One side of the beam is fixed. The other side is under a torque loading of 1900Nm. Also at the free side a inserted a cylindrical joint to get rid of unwanted displacements, except the twist displacement.

Using ADAMS autoflex with Replace Part option. I simulated the model and measured the twist angle. But the measured values are way higher than the values I calculated using standard strength formulas.

Anybody knows whats wrong with this simulation? By the way I fixed the beam at its section center. But when I use multi fix joints (1 center, 4 quadrants) and replace with flex; I get slightly better results but not very near to actual calculated value.

Any help is greatly appreciated.

Regards

 

[GregLocock]

What value did you get by hand? That's a pretty stiff torsion member, try again with a 1mm wall thickness.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Drkwing]

Thanks for your answer Gregg,

The problem has got nothing with the dimensions of the torsion member. The value I computed with hand calculation is simply correct. It was 2 degrees

I found out that the problem as the constraint type of the body in autoflex. I changed the left side attachment to surface. Then rerun the simulation. I got a twist angle of 2.02 degress which is pretty close to the computed value.

Regards