Estimation of the Rotational Terms of the Dynamic Response Matrix

Abstract

The dynamic response of a structure can be described by both its translational and rotational receptances. The latter ones are frequently not considered because of the difficulties in applying a pure moment excitation or in measuring rotations. However, in general, this implies a reduction up to 75% of the complete model. On the other hand, if a modification includes a rotational inertia, the rotational receptances of the unmodified system are needed. In one method, more commonly found in the literature, a so called T-block is attached to the structure. Then, a force, applied to an arm of the T-block, generates a moment together with a force at the connection point. The T-block also allows for angular displacement measurements. Nevertheless, the results are often not quite satisfactory. In this work, an alternative method based upon coupling techniques is developed, in which rotational receptances are estimated without the need of applying a moment excitation. This is accomplished by introducing a rotational inertia modification when rotating the T-block. The force is then applied in its centroid. Several numerical and experimental examples are discussed so that the methodology can be clearly described. The advantages and limitations are identified within the practical application of the method.

Mechatronics

“…It should be noted that equation (27) is not valid for complex waveforms and can only be used with harmonic sine waves. If the RMS of a non-harmonic time signal is being determined, either one of equations (25) or (26) should be used in place of (27).…”

Operational transfer path analysis

“…For real structures it will sometimes be necessary to take into account the moments that result from the links and act on the subsystem of interest. Sometimes it even can be interesting to identify the transfer path between an applied moment and a displacement [14]. One can conclude that for real 2D structures one needs two reference signals for each link: one signal that is correlated with the force and one that is correlated with the moment.…”

Dry Friction Contribution to Damage‐Caused Increase of Damping in Fiber‐Reinforced Polymer‐Based Composites

“…[1] As a consequence, early and reliable detection of such failureinitiating events during the entire operational lifetime is considered as a key function that should be implemented into future generations of smart structures. [3] In recent years, vibration-based structural health monitoring (SHM) methods were elaborated with the intention to overcome the aforementioned disadvantages. [3] In recent years, vibration-based structural health monitoring (SHM) methods were elaborated with the intention to overcome the aforementioned disadvantages.…”

“…[2] Currently, the presence of impact damage is determined in various schedule-based, stationary, non-destructive tests, e.g., X-ray inspections or ultrasonic examinations which are cost, time, and labor intensive and often cause operational breaks of fully functional machinery. [3] However, the state-of the-art implementations still reveal a potential for improvement of their application scope. [3] However, the state-of the-art implementations still reveal a potential for improvement of their application scope.…”