Energy consumption of machine tools needs to be investigated and decomposed to determine areas for improvement. Motors are one key area of energy consumption, and the analysis of motors, including pump motors is useful for long term energy saving. The following paper describes the static and dynamic analysis of a machine tool stand and an energy analysis to compare manufacturing the stand against using the pump motor. The stand needed to be designed that would both withstand the static load of the machine and minimize vibrational excitation caused during grinding experiments. A review of life cycle inventories for induction motors was then undertaken to evaluate the manufacturing energy consumption of pump motors. A breakeven time was determined for the energy investment of replacing a coolant pump with a stand to conserve energy via gravity-fed coolant recirculation. The simulations were performed as worst-case scenarios and are not necessarily indicative of regular use. Results indicate that the stand as designed will not transmit any significant harmonic vibrations. Results of the energy comparison identify that fractional horsepower coolant pumps operating continuously can be replaced with a stand and the energy to produce the stand will break even within two to three years depending on operating schedule.

The use of a new material is a hopeful strategy for breaking through the barrier of improving the product performance and/or the lowering of the product manufacturing cost. However, if the definite decision making method for selection of materials has not been established, use of a new material may not result in enhancement of the product performance and / or reduction of the product manufacturing cost. This paper proposes a methodology for decision making of a material used in machine structures from the standpoint of structural dynamics. First, purposes for use of new materials and evaluative parameters for decision making of material choice are described, and fundamental knowledge and theorems for decision making are established. Then, general decision making procedures for material choice are constructed. Finally, for model cases of purposes for use of new materials, detailed decision procedures are explained using also some numerical examples.

Since interior noise has a strong effect on vehicle salability, it is particularly important to be able to estimate noise levels accurately by means of simulation at the design stage. The use of sensitivity analysis makes it easy to determine how the analytical model should be modified or the structure optimized for the purpose of reducting vibration and noise of the structural-acoustic systems. The present work focused on a structural-acoustic coupling problem. As the coefficient matrices of a coupled structural-acoustic system are not symmetrical, the conventional orthogonality conditions obtained in structural dynamics generally do not hold true for the coupled system. To overcome this problem, the orthogonality and normalization conditions of a coupled system were derived by us. In this paper, our sensitivity analysis methods are applied to an interior noise problem of a cabin model. It will be shown how a sensitivity analysis process is performed, and how vibration and noise can be reduced.

It is well known that a discrete analytical model cannot accurately represent the dynamics of a continuous physical system over the frequency range of the model. Methods have been presented with the intention of improving analytical models (finite element models in particular) by the use of either (a) measured modal data or (b) measured frequency responses. In this paper we consider in particular the selection of weighting terms and the physical significance of the estimates. In both cases the discussion is illustrated by means of example problems.

A new mode superposition method of structural dynamics is presented, which uses eigenmodes and modified static modes. The modified static modes matrix is obtained from the static modes and lowest eigenmodes by external loads in generalized coordinates. By using modified static modes, the load vectors corresponding to the highest modes can be set at zero. The proposed method and the conventional method with both a limited number of eigenmodes and all eigenmodes are applied to two numerical models, and the effectiveness of the proposed method is discussed.

This paper outlines a methodology for the automatic creation of finite element meshes used for calculating structural dynamic behaviour. Starting from the idealized geometry of the structure, the proposed Intelligent Meshing Tool determines a mesh density that a priori guarantees the resonant frequencies to be calculated within predetermined accuracy limits. Unlike most existing techniques for automatic meshing, this technique is not inherently adaptive, but does not exclude an extra adaptive mesh refinement step, either. Implementation of this methodology is discussed for structures composed of straight uniform, curved and tapered beam-like components. The feasibility of the meshing strategy is illustrated by means of an example.

In this paper an effective approach for the identification of stochastic structural systems from multiple-excitation multiple-response forced vibration data, is introduced. The proposed approach represents a novel extension of the method of Lee and Fassois (1990b), that enables it to: (a) Operate on either vibration displacement, velocity, or acceleration data records, and, (b) perform accurate analysis of the estimated structural model by using a currently introduced exact and physically meaningful Dispersion Analysis methodology. These new features, combined with its other important properties, make the proposed approach not only capable of overcoming the limitations of current techniques, but, also, a comprehensive procedure for multiple-excitation multiple-response stochastic structural dynamics identification. The excellent performance characteristics of the proposed approach are finally verified via numerical simulations with structural systems characterized by well-separated and closely-spaced modes, as well as data corrupted at various noise-to-signal ratios. Comparisons with the Eigensystem Realization Algorithm (ERA), through which the limitations of deterministic methods are illustrated, are also presented.

A frequency domain identification technique applicable to damped distributed structural dynamic systems is presented. The technique is developed for beams whose behavior can be modeled using the Euler-Bernoulli beam theory. External damping of the system is included by means of a linear viscous damping model. Parameters to be identified, mass, stiffness and damping distributions are assumed to be continuous functions over the beam. The response at a discrete number of points along the length of the beam for a given forcing function is used as the data for identification. The identification scheme involves approximating the infinite dimensional response and parameter spaces by using quintic B-splines and cubic cardinal splines, respectively. A Galerkin type weighted residual procedure, in conjunction with the least squares technique, is employed to determine the unknown parameters. Numerically simulated response data for an applied impulse load are utilized to validate the developed technique. Estimated values for the mass, stiffness and damping distributions are discussed.

In the field of structural dynamics of large space structure (LSS), control/structure interaction technologies have been attracting much attention of researchers, and various types of control theory have beer, proposed. Meanwhile, it is important to develop actuators for the use of structural control. Piezoelectric device has some advantages characteristics such as compact size, high frequency response, low energy consumption over the other devices. With this background a uniquely designed piezoelectric actuator both for active dumping and shape adjustment has been preliminarily developed for experimental use. This paper describes the experimental results of the actuator for active dumping of planar truss and for statical or dynamical shape adjustment. And numerical simulations of planar truss with minimum numbers of pairs of collocated actuators and sensors show that a state observer can estimate truncated modes precisely and that the excited vibration can be dumped out rapidly.

This paper presents work in progress toward the development of a test and evaluation system for a new concept in experimental structural dynamics. Structural imaging is composed of both the static and dynamic image of the structure, resulting in the structure’s profile and dynamic response. Structural imaging is realized by interfacing a scanning laser velocimeter to an engineering workstation for data acquisition, signal processing, data modeling and scientific visualization. A software system is to be developed that will allow the investigation of the science and the rapid-prototyping and evaluation of new methods. The design goals for the system software are presented. The concepts defining the elements of the software architecture are also discussed. The event driven finite state machine is explored as the fundamental model of the system architecture. Run-time configuration of the software and virtual instruments provides a mechanism for the evolution of the system. The concepts of the project and test objects are introduced to support the testing of structures. Issues of systems integration and system objects for handling errors and files are also discussed.

The paper studies the global methods in monitoring structural health. The principle of global methods is based on the structural dynamic theorems. There are four theories available; namely, (1) the random decrement theory, (2) the modal frequency theory, (3) the transmissibility theory, and (4) the modal shape theory. This paper addresses specifically the modal frequency theory and the transmissibility theory, and their application to the location of fracture damages and the intensity of the damages. The reliability and health assessment depends on the accurate modeling of the damaged structure. With the damage assessment, the paper proposes a method to estimate the upper bound of reliability of the structure, during the hysteretic cycling of the loading.

Experimental spatial dynamics modeling involves using scanning lasers to sample surface shape and dynamic response of structures in order to verify structural dynamics design intent. Formation of accurate spatial models from laser-based measurements requires that laser position and orientation be registered relative to a fixed coordinate system. A three point direct registration procedure is defined for shape modeling using laser range and mirror deflection angles. Surface velocity measurements with a portable laser Doppler vibrometer (LDV) also require registration, but range information is unavailable. A multiple point indirect registration algorithm for the LDV is described that involves minimizing three nonlinear equations. A simulated laser rangefinder (LRF) was developed for demonstrating three point direct registration. The 3-D geometry of a compressor housing was modeled by combining range data from multiple laser positions. The multiple point indirect registration was applied to 3-D velocity response field reconstruction of a composite plate from velocity measurements scanned at three separate positions.

The space-time finite element method has emerged as a promising alternative numerical analysis technique for structural dynamics. This paper concentrates on hp-version triangular elements based on a variational statement of elasto-dynamics formed on Hamilton’s law of varying action. As such, forces and momenta are weak; and element boundaries may cut across space and time. This forms a natural framework for problems with both moving load and wave propagation. This paper presents applications of the method to such problems with numerical results and conclusions regarding proper mesh geometry.

The surface variational principle (SVP) has been developed as a method for gaining analytical-type results for radiation and scattering from submerged bodies whose shape does not suit classical techniques for analyzing the Helmholtz equation. The approach employs Ritz series expansions for surface pressure and velocity in the frequency domain. The relation between the series coefficients is obtained by extremizing the SVP functional. The present work extends the earlier developments to the case of an axisymmetric elastic shell that is subjected to an arbitrary excitation. The surface pressure and normal velocity are represented as a sequence of surface waves that are the trace of the waves in the surrounding fluid medium. SVP is used to determine the wavenumber spectrum of pressure amplitudes generated by a specific wave having unit velocity amplitude. The structural displacement field is represented by Ritz expansions, and equations governing the generalized coordinates associated with these series are obtained by invoking Hamilton’s principle. Difficulties in satisfying the continuity conditions at the apexes are circumvented by mapping the eigenmodes for a spherical shell into the variable representing position along the meridian of the shape generator. The structural dynamic equations are coupled to the SVP equations by matching the normal velocity in the fluid to the time derivative of the normal displacement, as well as using the series expansion for surface pressure to form the contribution of the pressure to the generalized forces. Results for a spherical shell subjected to a trans erse point force at the equator, which is a nonaxisymmetric representation of the excitation, are compared with analytic results. Predictions for a hemi-capped cylindrical shell are compared to those obtained from SARA-2D (Allik, 1991), which is a finite/infinite element program. In addition to providing validation of the SVP implementation, each set of results is used to illustrate the convergence and error measures provided by an SVP analysis.

This paper presents a wavelet transform-based method of extracting the impulse response characteristics from the measured disturbances and response histories of linear structural dynamic systems. The proposed method appears to have alleviated some of the most pronounced deleterious aspects of both the time-domain methods that suffer from the matrix ill-conditioning of the input signals and FFT-based methods that must cope with erraneous auto and cross-correlation functions, unless the input signals are rich enough in frequency content The method is found to be effective in capturing very low frequency response components and also far insensitive to output noises than existing methods. The present method has been applied to a variety of problems, which show significant improvements over existing impulse response function extraction methods, especially for limited harmonic excitations and input/output data contaminated with noises.

This paper addresses the use of discrete wavelet tranforms for the identification of structural dynamics models. First, the discrete temporal impulse response functions are obtained from vibration records by the discrete wavelet transforms (DWTs), which are then utilized for system realizations. From the realized state space models, structural modes, mode shapes and damping parameters are extracted. Attention has been focused on a careful comparison of the present DWT system identification approach to the FFT-based approach and a rational criterion for truncating realized singular values. Numerical examples demonstrate that the present DWT-based structural system identification procedure outperforms the FFT-based procedure.

This paper discusses about robust vibration control of a flexible structure that has transverse and torsional vibration modes. A design method of a controller taking account of the parameter variations and the residual dynamics is presented. The transverse-torsional coupling is translated into parameter variations, and other model errors of structural dynamics of the system are interpreted as frequency-shaped weighting functions. The H∞/μ control theory is applied to synthesize controller and these perturbations are formulated in the generalized plant. To examine the capability of the obtained controller, computer simulations and control experiments are carried out and the effectiveness of the presented method is verified.

A linear least-squares procedure for the determination of modal residues using time-domain system realization theory is presented. The present procedure is shown to be theoretically equivalent to residue determination in realization algorithms such as the Eigen-system Realization Algorithm (ERA) and Q-Markov COVER. However, isolating the optimal residue estimation problem from the general realization problem affords several advantages over standard realization algorithms for structural dynamics identification. Primary among these are the ability to identify data sets with large numbers of sensors using small numbers of reference point responses, and the inclusion of terms which accurately model the effects of residual flexibility. The accuracy and efficiency of the present realization theory-based procedure is demonstrated for both simulated and experimental data.

The paper deals with improvements of accuracy of structural dynamic calculations by using both the advantages of Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA). The basis for such improvements are reasonable mechanical and numerical models and accurate frequency response measurements (eigenfrequencies and mode shapes). The paper deals first with reasons for and estimations of errors in numerical and experimental analysis. It can be shown by theory and experiment that neither FEA nor EMA models are unique, due to inevitable incompleteness of the mode shapes and eigenfrequencies from a vibration test. Verification and updating of FE models by linking FEA with EMA are discussed in the paper and mainly focussed on FE models with a large number of degrees of freedom. Hence an update method has been introduced, which leads to an improved model in a relatively small quantity of computer time. It can be shown, that based on measured eigenfrequencies and calculated eigenvectors, an updating of FE-models for real engineering problems, by changing the mass matrix only, is a very efficient procedure with a surprisingly good quality updated model.

A new method for measurement and visualization of structural dynamic vibration characteristics is presented. Using digital shearography as an imaging tool combined with a stroboscopic phase shifting technique for quantitative fringe pattern interpretation, the fullfield modeshape amplitude and phase distribution is calculated. Theory together with experimental verification is discussed.