schopenhauer
Marine/Ocean
- Mar 17, 2018
- 12
Hello everyone,
I have been assigned the task of designing a propeller shaft for a truck, one of the requirements is to avoid the phenomenon of whirling. This is a new topic for me, so I will summarise what I believe I know until now:
- At certain critical speeds, the elastic deflection of the shaft gets very large
- To avoid this problem, the critical speed of the shaft must be above its maximum operating speed
- For some reason, these critical speeds coincide with the natural frequencies of the system
Based on this, I implemented some analytical equations in Excel and built a FEM of the shaft to extract the natural frequencies of the system. The numbers agree very well, but I have a few questions:
- Is there a way to simulate the rotating speed of the shaft in Abaqus to obtain the real displacements at the whirling speed?
- How can I study the influence of torque and twisted geometry on the critical speed of the shaft? I’ve read that the impact can be significant.
- What does it mean in real life for a propeller shaft simply supported and fixed conditions? The boundary conditions have a deep impact on the critical speed of the tube, the only information I’ve read until now is that short bearings act as SS supports while long bearings as fixed supports. Why?
Thanks in advance for any help, please let me know if I can clarify anything.
I have been assigned the task of designing a propeller shaft for a truck, one of the requirements is to avoid the phenomenon of whirling. This is a new topic for me, so I will summarise what I believe I know until now:
- At certain critical speeds, the elastic deflection of the shaft gets very large
- To avoid this problem, the critical speed of the shaft must be above its maximum operating speed
- For some reason, these critical speeds coincide with the natural frequencies of the system
Based on this, I implemented some analytical equations in Excel and built a FEM of the shaft to extract the natural frequencies of the system. The numbers agree very well, but I have a few questions:
- Is there a way to simulate the rotating speed of the shaft in Abaqus to obtain the real displacements at the whirling speed?
- How can I study the influence of torque and twisted geometry on the critical speed of the shaft? I’ve read that the impact can be significant.
- What does it mean in real life for a propeller shaft simply supported and fixed conditions? The boundary conditions have a deep impact on the critical speed of the tube, the only information I’ve read until now is that short bearings act as SS supports while long bearings as fixed supports. Why?
Thanks in advance for any help, please let me know if I can clarify anything.