# Search Results

Viewing 1 to 3 of 3
Technical Paper

### Critical Speed Vibrations Induced by Unstable Gyroscopic Moment

2005-05-16
2005-01-2534
Critical speed induced by imbalance forces is a well-known dynamic behavior of rotating shafts. Such problems are typically found in flexible shafts or rigid shafts with flexible supports when the frequency of rotation reaches the natural frequencies of the shaft. This simple critical speed problem is well understood and formulated in many engineering texts. However, not all critical speed phenomena are induced by imbalance. A perfectly balanced shaft with certain inertial properties also reaches a critical speed condition at a rotational speed that is not equal to the natural frequency of the shaft. Several variables of the dynamic system play a role on the critical speed condition, which is mainly induced by the unstable gyroscopic moment acting on the shaft. The unstable gyroscopic moment forces the shaft bearings to deflect causing precession about the undeflected geometric centerline of the shaft, but the rotation and precession speeds remain synchronized at low speeds.
Technical Paper

### Computing Transfer Functions from Mass Loaded Response of Structures

2004-03-08
2004-01-0780
This paper outlines a method for computing the transfer functions of structures using their mass loaded responses. According to the method, scaled transfer functions are computed from the response of a structure and without any knowledge of the input forces. The paper outlines the analytical approach, develops the necessary equations for the computation of transfer functions between a mass loading point and other points on a linear dynamic system. A numerical example to show the validity, advantages and limitations of the method is also provided. Currently, the method can be applied to the responses obtained from analytical simulations where it may be necessary to compute coupled response of a simulated dynamic system with other dynamic systems that are not (or cannot be) included in a simulation. It is not uncommon that many dynamic simulations exclude certain coupling effects between the main and the auxiliary systems.
Technical Paper

### Computing the Dynamic Forces and Moments Acting on the Crank-Flywheel Joint From Measurement Data

2003-05-05
2003-01-1639
This paper describes a technique to approximately compute the dynamic forces and moments acting on the crankshaft-flywheel joint as well as the crank nose using measurement data. The same technique can also be used on data generated by dynamic simulations. The method is based on rigid body dynamics where the measured accelerations and velocities are substituted into the equations of motion to compute the dynamic forces and moments. However, using the measured (or simulated data) in the equations of motion is not straightforward and requires special measurement techniques and data analysis procedures. This paper describes the special measurement techniques and apparatus, as well as the data analysis techniques necessary for proper computation of the dynamic forces and moments.