Mark A. Norris

Multidimensional mount effectiveness for vibration isolation

A method is presented for predicting the performance of multiple mount passive isolation systems. Performance is expressed in terms of a mount effectiveness matrix which relates the structure vibration in an isolated system to the structure vibration in an unisolated, or hard mounted system. Frequency response functions of the engine, isolator, and structure are used to construct the effectiveness matrix at each frequency of interest. Effectiveness matrix expresions are derived for a mounting system connected at multiple points by massless isolators. Isolator design guidelines are developed for the single and multiple isolator mounting systems

Implementation of Tuned Vibration Absorbers for Above Ground Pipeline Vibration Control

An overview of recent developments of tuned vibration absorbers (TVAs) for vibration suppression is presented. The paper summarizes some popular theory for analysis and optimal tuning of these devices, discusses various design configurations, and reviews the recent application of TVAs to control wind-induced oscillations of pipelines above the Arctic Circle. Although the wind-induced pipeline vibrations are relatively small, the accumulation of vibration cycles can cause fatigue at pipeline joints. The TVAs used in this application have reduced the RMS displacements of the pipeline by as much as a factor of seven. Additionally, the paper introduces a new overhead TVA installation on the pipeline for accommodating environmental considerations.

Theoretical and experimental studies of distributed piezoelectric actuators for interior noise control

A special design theory for distributed piezoelectric actuators is introduced, for reducing noise and vibration in structures. A uniform cylindrical shell is taken as an example of a host structure to illustrate the effectiveness of the design theory. The actuators are designed to reduce the shell structural vibration and interior noise in a wide range of frequencies, for cases where the input disturbance is tonal. Extensive computer simulations were completed to study various aspects of the design theory. In addition, experiments were conducted and the test results strongly supported the theoretical development.

Commercial active noise control solutions for aircraft—A variety of approaches

Today’s aerospace market is placing increasing emphasis on reducing noise and vibration to enhance passenger comfort. Lord offers high‐performance active solutions for aircraft noise problems with its NVX active systems. There are currently over 50 Lord NVXTM Active Systems flying on a variety of aircraft around the world. These systems include active isolations sytems for the Cessna Citation X business jet, a pylon active structural control system for DC9 aircraft, and speaker‐based active noise control systems for corporate turboprops. While the systems share many commonalties, they represent a variety of different approaches to the individual noise problems of these aircraft. Each of these problems requires a solution optimally designed for the application. During the presentation, the system components and general operation will be discussed. The benefits and limitations of these approaches will also be covered. How each system was optimized for its specific application will also be discussed. Numerou...