hi, i'm a student . I have a problem with my FEM model. I have already checked the properties and materials. I performed a modal analysis where the first frequencies correspond to those of a CANTILEVER BEAM to verify that there are no errors in the model. However as soon as I go to apply the loads I get absurd displacements. I applied two loads concentrated around the end of the blade, one simulating the lift equal to 7780 N (z axis) and one simulating the centrifugal force of 178876 N (along y). As a result I get a displacement z z 8 meters long when the whole model is about 5 meters long. What could be the problem?
thank you
I know you said that you checked the properties and materials, I'm assuming that this means your unit system. That would be the first thing that I would have suggested because you may just have a mismatch in your unit system and may not actually have 8 meters of displacement.
https://www.dynasupport.com/howtos/general/consistent-units
Is the screen clip that you are showing from a dynamic animation or is this the shape of the blade initially?
And just to be clear, you have rigidly constrained the blue end as the cantilever correct?
The model is in millimeters. I entered E and G in megapascals while the density in tonnes / mm ^ 3. The screen is the final step of dynamic animation . This is the model with the constrained. I check all dof in the faces as show in the figure.
Is the direction that you are applying the force correct? It looks like the y-force may be applied in the negative direction which would make sense that it would shoot upward +z.
I apologize if this seems rudimentary, I'm just going off what you've told me and what I can see.
@negativevolume , no problem but thank you for the interest.
The forces are applied in the right direction, or at least I think it is. I set along z and along y and looking at the graphic arrows are in the right direction. If you want I can load the model if you have the opportunity to view it
If you have the end constrained with *Boundary_spc_set using a node set then you can output the force from that by adding *Database_spc.
You can also define a cross_section load cell towards the base of the blade using *Database_cross_section_set and adding *Database_secforc.
Using either of these methods, you will be able to look at the forces and determine the directionality of the loads. If you are getting -y force then I would flip the direction of your load. You can also just try doing this from the start as a test to see if it addresses the issue.
@negativevolume
sorry but it is my first model on hypermesh (optistruct) and I have not understood what I should do in detail.
@negativevolume
I performed 2 analyzes inverting the force along y but I had almost no change in the displacement. now what do I do?
with the force along y axis i have 7,088 meter (displacement along z) ,instead with the force along -y i have 10,745 meter(displacement along z)