Hi,
I would like to have a good approximation between a real Jeffcott rotor (Laval rotor) and one simulated in Ansys. I used SOLID185, COMBIN14 for the bearings and CONTAC52 for a crack. I have created a parametric macro to make changes very easy in which the variables are:
L=LENGTH OF THE SHAFT
D=DIAMETER OF THE SHAFT
LD=LENGTH OF THE DISK
DD=DIAMETER OF THE DISK
G1=OVERHANGING SHAFT LEFT
R1=WIDTH BEARING 1
G2=OVERHANGING SHAFT RIGHT
R2=WIDTH BEARING 2
LG=POSITION OF THE CRACK
PG=DEPTH OF THE CRACK (< D/2)
AG=GAP OF THE CRACK
TAMELE=ELEMENT SHAFT SIZE
GAP=BEARINGS GAP
RIG=SPRING BEARINGS STIFFNESS
VELANG=ANGULAR SPEED IN RPM
When I do a modal analysis in the real shaft I have the first and second natural frequencies and I would like have exactly the same in Ansys. My question is about this:
1) In a Jeffcott rotor we don’t consider the gyroscopic effect so in Ansys we don’t use Coriolis, is that true? Or in a real shaft is there this effect? I’m not be sure of this…
2) If I want to simulate the effect of a crack I do first a static analysis with contact element, then coupled the nodes in contact and then make a new static analysis with prestress on, and the modal analysis. Is necessary the second analysis? Or is the same a prestress modal?
3) How can I calculate the bearing stiffness in the real shaft? I put a general value in Ansys (1E5 N/mm).
3) I don'y used damping...is this OK?
Thanks a lot and sorry for my English.
I would like to have a good approximation between a real Jeffcott rotor (Laval rotor) and one simulated in Ansys. I used SOLID185, COMBIN14 for the bearings and CONTAC52 for a crack. I have created a parametric macro to make changes very easy in which the variables are:
L=LENGTH OF THE SHAFT
D=DIAMETER OF THE SHAFT
LD=LENGTH OF THE DISK
DD=DIAMETER OF THE DISK
G1=OVERHANGING SHAFT LEFT
R1=WIDTH BEARING 1
G2=OVERHANGING SHAFT RIGHT
R2=WIDTH BEARING 2
LG=POSITION OF THE CRACK
PG=DEPTH OF THE CRACK (< D/2)
AG=GAP OF THE CRACK
TAMELE=ELEMENT SHAFT SIZE
GAP=BEARINGS GAP
RIG=SPRING BEARINGS STIFFNESS
VELANG=ANGULAR SPEED IN RPM
When I do a modal analysis in the real shaft I have the first and second natural frequencies and I would like have exactly the same in Ansys. My question is about this:
1) In a Jeffcott rotor we don’t consider the gyroscopic effect so in Ansys we don’t use Coriolis, is that true? Or in a real shaft is there this effect? I’m not be sure of this…
2) If I want to simulate the effect of a crack I do first a static analysis with contact element, then coupled the nodes in contact and then make a new static analysis with prestress on, and the modal analysis. Is necessary the second analysis? Or is the same a prestress modal?
3) How can I calculate the bearing stiffness in the real shaft? I put a general value in Ansys (1E5 N/mm).
3) I don'y used damping...is this OK?
Thanks a lot and sorry for my English.
