The UC-SDRL activity continues to lead the field of experimental modal analysis and structural dynamics. The Department of Mechanical Engineering originally developed a mobile vibrations laboratory as part of an Air Force contract (1965) to study the structural dynamics of machine tools. That mobile laboratory was equipped with state-of-the-art analog vibration analysis equipment, hydraulic and electrodynamic exciter systems (in order to provide external excitation of the structures), and a variety of transducers, cables, and other equipment necessary to conduct a complete survey of the structural dynamics of machine tools. At that time, this mobile laboratory was the only facility of this type in the world.
This early work concentrated on the measurement of the vibratory response of a structure due to a single sinusoidal force excitation in order to develop empirical estimates of the frequency response functions of the structure. One goal of such measurements was the solution of vibration problems, in military and commercial applications, in which structural dynamics affect the dynamic performance of the structural system. Another goal was the development of modeling techniques based upon modal representations of the structural characteristics. As a result of the knowledge learned from the Air Force contract, two small companies were formed to provide technical services to industry based upon the knowledge gained from the research at the University. Structural Dynamics Research Corporation (SDRC) and Zonic Corporation remain today as leaders in this field.
After the conclusion of the Air Force contract, the UC-SDRL activity continued related vibration research activity at the University. The mobile laboratory was used for University educational purposes, for industrial consulting, and for on-site training in industrial settings. As a result of the Air Force machinability work, many problems had been solved but many questions had been uncovered which would become the focus of research which continues to the present time. Additionally, the results of the application of experimental structural analysis methods to the machine tool area fostered far wider applications in the analysis of vibration, controls, and acoustic considerations in all areas involving structural systems. Applications of this technology to industrial problems led to exciting, new developments at the University including significant developments in the area of digital signal processing, applied Fourier analysis, vibrations, and structural dynamics. In this context, the members of the UC-SDRL developed expertise in the use of electronic compter-based instrumentation for the solution and evaluation of dynamics problems.
The increased involvment of computers and semiconductor electronics in the experimental analysis equipment started a second phase in the development of the capability of the UC-SDRL. The expertise in experimental analysis of structural dynamics and the capability of the computer based equipment led to new problems and new approaches in the area of experimental analysis of structural dynamics. Based upon this background, the UC-SDRL activity focussed a large effort in the area of modal parameter estimation algorithms. In the early 1970s, all of the initial experimental analysis of structural dynamics were based upon single degree of freedom algorithms which were severely limited in the analysis of frequency response functions acquired from common structural systems. The development of new multiple degree of freedom algorithms that used redundant characteristics in the frequency response function matrix was pioneered in a joint effort by members of the UC-SDRL activity and a similar group at the University of Leuven (Belgium). This joint working relationship continues, and has been expanded to several other universities in the United States, England, France, Japan, and China, in many areas of experimental analysis of structural dynamics.
The computer-based experimental analysis system provides great flexibility in the algorithms that are available for modal parameter estimation as well as in the presentation and storage of voluminous data in an accurate digital format. The computer-based systems also made possible the real time animation of modal vectors, developed by the UC-SDRL activity for the automotive industry, to provide a capability to interpret the physical meaning of the modal vector. Hardware and software, developed by the UC-SDRL activity, to improve frequency response function estimation, modal parameter estimation, and modal vector animation is now the basis for many commercially available experimental structural dynamics analysis systems. In 1978, the UC-SDRL activity first offered an intensive short course in the area of experimental modal analysis to provide an educational service to industry and to provide funding for the support of research and research personnel. This intensive short course has been given two to four times each year and has served as the basic education in this area for over 700 engineers. The funding generated from this educational activity together with generous corporate grants from Hewlett Packard have enabled the UC-SDRL activity to continue to maintain a lead position in terms of state-of-the-art equipment and ongoing research in the area of experimental analysis of the dynamics of structural systems.
An outline of some of the significant contributions made by the UC-SDRL activity, a short summary of the funded research that has been part of the UC-SDRL activity since 1975, and a partial list of publications generated by the UC-SDRL activity over the past years are listed in other UC-SDRL WWW pages.