MES Analysis on a complex femur
MES Analysis on a complex femur
(OP)
Hi everyone,
I'm attempting to peform analysis upon the head of the femur by simulating impact on a hard surface. I am using an IGES model of the femur and a skin model that I created around the femur head. I attempted to pin the femur (at a node) in an upright position at the knee end, and apply a force near the top so that it falls in the direction of the fixed surface below. I set up surfaces for contact (the outside of the flesh and the floor), all of the parts meshed successfully, gravity was enabled, and all of the material properties were defined. When I ran the analysis, it didnt even make it to step 1 before it stopped. I tried a few other analyses including attempts with the inside surfaces of the skin and the outside surfaces of the bone set as contact surfaces, but had the same problems. Either way, the bone would not fall towards the floor. Are there any other settings that need to be adjusted so that the femur will fall and make contact with the floor?
If anyone has any ideas, or experience with impact analysis, that would be a great help.
Thanks a lot,
Jesse
I'm attempting to peform analysis upon the head of the femur by simulating impact on a hard surface. I am using an IGES model of the femur and a skin model that I created around the femur head. I attempted to pin the femur (at a node) in an upright position at the knee end, and apply a force near the top so that it falls in the direction of the fixed surface below. I set up surfaces for contact (the outside of the flesh and the floor), all of the parts meshed successfully, gravity was enabled, and all of the material properties were defined. When I ran the analysis, it didnt even make it to step 1 before it stopped. I tried a few other analyses including attempts with the inside surfaces of the skin and the outside surfaces of the bone set as contact surfaces, but had the same problems. Either way, the bone would not fall towards the floor. Are there any other settings that need to be adjusted so that the femur will fall and make contact with the floor?
If anyone has any ideas, or experience with impact analysis, that would be a great help.
Thanks a lot,
Jesse





RE: MES Analysis on a complex femur
RE: MES Analysis on a complex femur
-Jesse
RE: MES Analysis on a complex femur
I done quite a bit of impact analysis. Yours really doesn't sound too difficult. Let me know any of this doesn't make sense.
Garland
Garland E. Borowski, PE
RE: MES Analysis on a complex femur
I'm not sure what you mean by constraining the two translational directions perpendicular to the impact plane. There is only one direction (x) perpendicular to the impact plane that I set up on the surface of the floor.
RE: MES Analysis on a complex femur
Thanks,
Jesse
RE: MES Analysis on a complex femur
Two possible solutions: plates form a hinge with brick elements, so you can model a fictitious, infinitely stiff plate, attach it your bricks at the knee and fix the opposite edge of the plate (doing this will cause the bricks that make up your femur and skin to rotate about the edge of your fictitious plate) OR, you can connect every node of your knee area to a common node some distance away, define the lines drawn from the end nodes to the common node as beams, give the beams infinite stiffness (modulus of elasticity of 1e9psi, area of 1, moment of inertia of 1e6, etc.), and then pin the single node to which your model is connected.
You may also want to restrict the node to which you applied your force so that it stays in the plane of rotation. For instance, you mentioned that the x direction is the only one perpendicular to your impact plane. to keep the femur rotating in the x-y plane, do not allow your load application point to move in the z-direction. This should speed things up a little.
Feel free to call me at 251-232-3723 with questions. I'm in the central time zone in the US.
Garland
Garland E. Borowski, PE