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Showing papers in "The Shock and Vibration Digest in 2003"


Journal ArticleDOI
TL;DR: In this article, Niezrecki et al. summarized the hardware and software issues of impedance-based structural health modi- toring based on piezoelectric materials.
Abstract: In this paper we summarize the hardware and software issues of impedance-based structural health moni- toring based on piezoelectric materials. The basic concept of the method is to use high-frequency structural excitations to monitor the local area of a structure for changes in structural impedance that would indicate imminent damage. A brief overview of research work on experimental and theoretical stud- ies on various structures is considered and several research papers on these topics are cited. This paper concludes with a discussion of future research areas and path forward. Piezoelectric materials acting in the "direct" manner pro- duce an electrical charge when stressed mechanically. Con- versely, a mechanical strain is produced when an electrical field is applied. The direct piezoelectric effect has often been used in sensors such as piezoelectric accelerometers. With the converse effect, piezoelectric materials apply local- ized strains and directly influence the dynamic response of the structural elements when either embedded or surface bonded into a structure. Piezoelectric materials have been widely used in structural dynamics applications because they are lightweight, robust, inexpensive, and come in a variety of forms ranging from thin rectangular patches to complex shapes being used in microelectromechanical systems (MEMS) fabrications. The applications of piezoelectric mate- rials in structural dynamics are too numerous to mention and are detailed in the literature (Niezrecki et al., 2001; Chopra, 2002). The purpose of this paper is to explore the importance and effectiveness of impedance-based structural health mon- itoring from both hardware and software standpoints. Imped- ance-based structural health monitoring techniques have been developed as a promising tool for real-time structural dam- age assessment, and are considered as a new non-destructive evaluation (NDE) method. A key aspect of impedance-based structural health monitoring is the use of piezoceramic (PZT) materials as collocated sensors and actuators. The basis of this active sensing technology is the energy transfer between the actuator and its host mechanical system. It has been shown that the electrical impedance of the PZT material can be directly related to the mechanical impedance of a host structural component where the PZT patch is attached. Uti- lizing the same material for both actuation and sensing not only reduces the number of sensors and actuators, but also reduces the electrical wiring and associated hardware. Fur- thermore, the size and weight of the PZT patch are negligible compared to those of the host structures so that its attach- ment to the structure introduces no impact on dynamic char- acteristics of the structure. A typical deployment of a PZT on a structure being monitored is shown in Figure 1. The first part of this paper (Sections 2 and 3) deals with the theoretical background and design considerations of the impedance-based structural health monitoring. The signal processing of the impedance method is outlined in Section 4. In Section 5, experimental studies using the impedance approaches are summarized and related previous works are listed. Section 6 presents a brief comparison of the imped- ance method with other NDE approaches and, finally, sev- eral future issues are outlined in Section 7. 2. Theoretical Background

1,048 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a generic procedure to the design process and give selective examples from the literature on relevant ma- terial, together with examples of their applications, such as structure modeling, model reduction, feedback control, feedforward control, con- trollability and observability, spillover, eigenstructure assign- ment (pole placement), coordinate coupling control, robust control, optimal control, state observers (estimators), intelli- gent structure and controller, adaptive control, time delay, actuator-structure interaction, and optimal placement of actuators
Abstract: In this paper we review essential aspects in- volved in the design of an active vibration control system. We present a generic procedure to the design process and give selective examples from the literature on relevant ma- terial. Together with examples of their applications, various topics are briefly introduced, such as structure modeling, model reduction, feedback control, feedforward control, con- trollability and observability, spillover, eigenstructure assign- ment (pole placement), coordinate coupling control, robust control, optimal control, state observers (estimators), intelli- gent structure and controller, adaptive control, active con- trol effects on the system, time delay, actuator-structure interaction, and optimal placement of actuators.

221 citations


Journal ArticleDOI
TL;DR: In this article, a review of the literature dealing with the effects of structural movement on human-induced dynamic forces is presented, and it is shown that human occupants can influence the dynamic properties (mass, stiffness, and damping) of the structures they occupy.
Abstract: In this paper we review more than 130 pieces of essential literature pertinent to the problem of human-structure dynamic interaction, applicable to the design of civil engineering structures. This interaction typically occurs in slender structures occupied and dynamically excited by humans through walking, running, jumping and similar activities. In this paper we first review the literature dealing with the effects of structural movement on human-induced dynamic forces. This is the first of two aspects of human-structure dynamic interaction. The literature dealing with this aspect is found to be quite limited, but conclusive in stating that structural movement can affect the human-induced dynamic forces, significantly in some cases. The second aspect considered is how human occupants influence the dynamic properties (mass, stiffness, and damping) of the structures they occupy. The body of literature dealing with this issue is found to be considerably larger. The published literature demonstrates beyond any doubt that humans present on structures should not be modeled just as additional mass, which is a common approach in contemporary civil engineering design. Instead, humans present on structures act as dynamic mass-spring-damper systems interacting with the structure they occupy. The level of this interaction is difficult to predict and depends on many factors, including the natural frequency of the empty structure, the posture and type of human activity, and, in the case of assembly structures, the relative size of the crowd compared with the size of the structure. One of the reasons for the existence of more papers in this area is the published biodynamical research into the mass-spring-damper properties of human bodies applicable to the mechanical and aerospace engineering disciplines. It should be stressed that results from this research are of limited value to civil engineering applications. This is because human bodies are, in principle, non-linear with amplitude-dependent dynamic properties. Levels of vibration utilized when experimentally determining mass-spring-damper properties of human bodies in biodynamical research are usually considerably higher than those experienced in civil engineering applications.

107 citations


Journal ArticleDOI
TL;DR: In this paper, the process of oil well rotary drilling is discussed from a vibrations perspective, along with a synopsis of the equipment used and of the procedures followed, and the performance modeling and monitoring are discussed, including data acquisition and utilization.
Abstract: The process of oil well rotary drilling is discussed from a vibrations perspective. Furthermore, a synopsis of the equipment used and of the procedures followed is included. Performance modeling and monitoring are discussed, along with data acquisition and utilization. Axial, torsional, and lateral vibrations are reviewed. Typical operational difficulties such as sticking, buckling, and fatiguing of strings are also reviewed. Finally, emerging techniques of analysis such as stochastic treatment, and optimization are discussed. To enhance the utility of the paper, references readily available in the form of books or archival journal publications are primarily cited. Furthermore, mathematical rigor and phenomenological completeness are sporadically moderated to conform with paper length limitations.

100 citations


Journal ArticleDOI
TL;DR: A review of the dynamic modeling of gear including defects is presented in this article, where the importance of defect models for a clear understanding of gear vibrations and also explore areas for introducing other defects in existing gear dynamic models.
Abstract: A large number of gear models for simulating the dynamic behavior of gears have appeared in the literature since 1920. In this paper we present a review of the dynamic modeling of spur gears including defects. We give the classification of gear dynamic models by different authors, and we explain various terms that are used in gear dynamic modeling. Gear dynamic models without any defects for single-, two-, and multi-degree-of-freedom systems have been discussed. The effects of various nonlinearities, such as variable mesh stiffness, mesh damping, gear errors, and backlash, on gear dynamic behavior have been discussed. Many researchers are actively developing advanced dynamic models of gear case vibration to ascertain the effect of different types of gear damage. Dynamic models including the effect of friction, wear and spalls on gear dynamic behavior have been considered in detail. The aim of this paper is to emphasize the importance of defect models for a clear understanding of gear vibrations and also to explore areas for introducing other defects in existing gear dynamic models.

76 citations


Journal ArticleDOI
TL;DR: This paper presents an overview of gossamer spacecraft technology, a brief overview of research work on experimental studies of tires, inflated tori, and other types of gOSSamer structures, and the future for ultra-flexible spacecraft technology.
Abstract: Gossamer structures, also known as inflatable or membrane structures, have been a subject of renewed interest in recent years for space applications such as communication antennas, solar thermal propulsion, space solar power, and other large spacecraft applications. The major advantages of using inflatable structures in space are their extremely low weight, on-orbit deployability, and minimal stowage volume for launching. In this paper, we present a literature survey on different aspects of inflatable structures. Analytical and experimental studies of an inflated torus-the main structural support system for several inflatables-have drawn a considerable amount of attention from the vibration and control community. The inflated torus will be the main focus of this survey. First, we present an overview of gossamer spacecraft technology. Thereafter, we consider analytical studies of inflated tori and arches, and we cite several research papers on these topics. Next, we present a brief overview of research work on experimental studies of tires, inflated tori, and other types of gossamer structures, and we outline the future for ultra-flexible spacecraft technology.

33 citations


Journal ArticleDOI
TL;DR: In this paper, an active and passive control of floor vibration using a proof-mass actuator is presented. But the authors focus on the effect of the actuator on the floor vibration.
Abstract: This paper reviews research, conducted by the authors over the last decade, pertaining to the control of ex- cessive floor vibration using active and passive devices. The active device studied uses a proof-mass actuator to deliver the control force to the floor system. Effectiveness and stabil- ity characteristics for a single-input/single-output (SISO) con- trol scheme, using velocity feedback, are explored. The SISO system is shown to increase damping to 40% of critical on an experimental floor when amplitudes remain in the linear range. When implemented on two in-place floors, at least a 70% reduction in vibration amplitudes due to walking was ob- served. Next, the benefits of expanding to a practical single- input/multi-output (SIMO) control system are identified. Ad- ditionally, techniques to optimize the SIMO scheme are presented. Because of the stability characteristics of the controlled system, the improvement noted for the SIMO scheme is most dramatic for floors with fundamental frequen- cies near the natural frequency of the actuator. I na2H zfloor example, a SIMO control scheme provided seven times more reduction than that of the SISO system. The passive device research focuses on the experimental implementation of tuned mass dampers (TMDs) to control floor vibration. Two different configurations are explored. The uniqueness of the first device is that liquid filled bladders are used to provide an economical damping mechanism. When implemented on an office floor, a significant improvement of walking vibration lev- els was observed. Satisfaction with the repair was noted from the occupants. The second device utilizes a configuration that has great flexibility in the field, thus allowing for more eco- nomical mass production. Using two TMDs, a significant re- duction of response was noted for the 5 and 6 Hz modes. Research to improve these active and passive strategies continues and will be reported as significant results are achieved.

28 citations


Journal ArticleDOI
TL;DR: A pure bibliography is presented here to save time for readers looking for information dealing with the subjects described below, not having access to large databases or not willing to spend time on uncertain information retrieval.
Abstract: The output of scientific papers in general is fast growing and professionals are no longer able to be fully up-to-date with all the relevant information. The increasing specialization in various engineering fields has resulted in the proliferation of subject-oriented journals and conference proceedings directed to specialist audiences. The researchers have more channels for communicating the results of their research at their disposal, but on the other hand to find necessary information may be a time-consuming and difficult process. Another question is whether researchers/scientists are willing to spend time looking for information. It has been pointed out that in engineering, informal knowledge channels are the most frequently used means of obtaining information. Many professionals prefer to rely on personal judgment or on the wisdom of their colleagues whenever they have problems to solve. In almost the last four decades, the finite element method (FEM) has become the prevalent technique used for analyzing physical phenomena in the field of structural, solid, and fluid mechanics as well as for the solution of field problems. The FEM is a useful tool also in biomechanics and biomedicine because it can be used to discover facts or study the processes in a way that no other tool can accomplish. The emphasis in research has been on applications to various areas such as orthopaedic and dental mechanics, cardiovascular and soft tissue mechanics, biological flow analysis, impact injury, etc. It is difficult for a single author to summarize the wide topic of this paper in a form of the state-of-the-art review paper; therefore a pure bibliography is presented here. Hopefully, this bibliography will save time for readers looking for information dealing with the subjects described below, not having access to large databases or not willing to spend time on uncertain information retrieval.

19 citations


Journal ArticleDOI
TL;DR: In this article, an experimental facility for measuring the vibration of bladed disks, such as those used in turbomachinery, is presented. But this facility is not suitable for the measurement of complex bladed disk dynamics, including the effects of small variations in parameters.
Abstract: In this paper we present the design of an experimental facility for measuring the vibration of bladed disks, such as those used in turbomachinery. In particular, a method for simulating the effects of rotating a bladed disk past stationary sources of excitation is described, in which acoustic excitation sources in the vicinity of each blade receive harmonic signals with precise phase differences. Optical measurement techniques, including laser vibrometry and holographic interferometry, are used to observe the vibration, so that neither excitation sources nor measurement devices contact the test specimen physically. The result is a versatile test facility appropriate for the investigation of complex bladed disk dynamics, including the effects of small variations in parameters, such as blade mistuning.

12 citations