Hi ,
Version: Creo 2.0
perhaps this is a common problem in FEA models - I'm having trouble properly properly defining the rotational constraints in a model and I'm getting strange results because of it.
I would like to model a steel plate constrained with a pin joint on either side.
The plate should be loaded centrally with 5000N. (see pictures in Excel table).
What i expect to see is that the plate bends upwards in the middle and is free to rotate on either side until the plate comes into tension and holds the load.
The intention was to make a simple model to see if it behaves as intended and then i would use the same method on a more complicated assembly model.
I've ignored the stress levels at first and only looked at the displacements to see if the model is behaving as intended.
i've tried the following and none seem to give the right model behaviour:
- pin constraints - result doesn't look right - as if plate 'tied down' left/right
- ball constraints - result doesn't look right - as if plate 'tied down' left/right
- Cylindrical co-ord systems defined for each lug left/right to allowing rotation about the Theta axis left/right. Tried a number of variations of fixed/free/prescribed for R and Theta here. The resulting displacement varies depending on how much prescribed rotation is allowed. This is independent of the load applied - i reduced the load to just 100N and the deflections were still very large. I expected the plate tension to limit the deflection as some stage.
The problem i see is that the pin/ball constraints seem to fix the edges and don't allow free rotation aroung the selected cylinderical surface as intended.
I thought the Cylindrical coord. system might work but it seems like i can allow any amount of rotational freedom and the resulting deflection just keeps on increasing with no end in sight.
would be great if someone had some more insights here - it doesn't seem to make sense.
Thanks,
Dermot