Hello and welcome to the last part of our series on Rotor Dynamics! In today’s blog we’ll be concluding with torsional analysis, and the steps needed to perform this type of analysis. If you haven’t had a look at the other entries in this series, you can find them here:
- What is Rotor Dynamics? And Where is it Found?
- Why is Rotor Dynamics so Important?
- What API Standards Govern Rotor Dynamics Analysis?
- Basic Definitions and Fundamental Concepts of Rotating Equipment Vibrations
- The Purposes and Objectives of Rotor Dynamics Analyses
- The Importance of Accurately Modeling a Rotor-Bearing System
- Modeling Bearings and Support Structures in a Rotor Bearing System
- Introduction to Performing Lateral Rotor Dynamics Analysis
In an earlier blog, we covered the basic definitions of lateral and torsional analysis. Lateral analysis is concerned with the bending behavior of a rotor train. Torque is a measurement of force that causes an object to rotate on an axis such as when a component needs to be “torqued to spec” in a car’s engine, for example. Torsional analysis, meanwhile, looks at the twisting behavior of the rotor train.
In the context of rotor dynamics, torsional vibrations refer to the oscillatory torsional deformations encountered by the shafts in the rotor train.

If these torsional vibrations and excitations are left undamped and aren’t analyzed properly, breakages and catastrophic failures can occur similar to undamped lateral excitations. For more on that, you can read up on the importance of rotor dynamics analysis here.