The Integrated Test Analysis Process for Structural Dynamic Systems

Dynamical and structural systems are susceptible to sudden excitations and loadings such as wind gusts, blasts, earthquakes, and others which may cause destructive vibration amplitudes and lead to catastrophic impact on human lives and economy. Therefore, various vibration absorbers of linear and nonlinear coupling dynamics have been widely studied in plenty of publications where some have been applied in real-world practical applications. Firstly, the tuned-mass-damper (TMD), the first well-known linear vibration absorber that has been well-studied in the literature and applied with various structural and dynamical systems, is discussed. The linear vibration absorbers such as TMDs are widely used in real-life small- and large-scale structures due to their robust performance in vibration suppression of the low natural frequency structural modes. However, the TMD performs efficiently at narrowband frequency range where its performance is deteriorated by any changes in the frequency content in the structure and the TMD itself. Therefore, the targeted-energy-transfer mechanism which is found to be achieved by nonlinear energy sinks (NESs) has ignited the interest in passive nonlinear vibration suppression. Unlike TMDs, the NESs are dynamical vibration absorbers that achieve vibration suppression for wide range of frequency-energy levels. Given the very rapid growth in this field and the extensive research studies supporting the robustness of the NESs, this paper presents the different types of NESs and their applications with main emphasis on the rotary-based and impact-based NESs since they are of high impact in the literature due to their strong nonlinear dynamical behavior and robust targeted energy transfer.

Based on an analysis of a supersymmetric extension of the algebra of pseudodifferential operators on ℝ1 an infinite hierarchy of supersymmetric Lax-integrable nonlinear dynamical systems is constructed by means of the Yang-Baxter ℛ-equation method. The structure of these systems on reduced invariant submanifolds specified by a natural invariant Lax-type spectral problem is investigated.

3R12. Nonlinearity in Structural Dynamics: Detection, Identification and Modeling. - K Worden and GR Tomlinson (Univ of Sheffield, UK). Inst Phys Publ, Bristol, UK. 2001. 659 pp. ISBN 0-7503-0356-5. $130.00.Reviewed by K Yagasaki (Dept of Mech and Syst Eng, Gifu Univ, 1-1 Yanagido, Gifu, 501-1193, Japan).This book provides backgrounds in some techniques for analyzing nonlinear structural dynamical systems and is intended for engineers and scientists in the fields of structural dynamics and nonlinear systems. It is also suitable for postgraduate and senior undergraduate students in these disciplines as a textbook and for expert structural dynamicists as a survey. Many engineering examples are given. As for the mathematics of the reader, calculation of vectors and matrices, and basic knowledge of linear differential equations and Fourier analysis are almost sufficient. The most enthusiastic topics in modern nonlinear dynamics are chaos and bifurcation. There have also been remarkable advances in the field of nonlinear control. However, these subjects are not treated in this book at all. Instead, it explains useful techniques, which include the frequency response functions (FRFs) and Hilbert transformations, for detection of nonlinearity and system identification (ie, estimation of the governing equations) when the systems do not exhibit very different motions, like chaos, from ones of linear systems. The techniques are especially important from a point of view of structural engineering because really nonlinear behavior like chaos is thought to be rather uncommon in the problems of that field. The book begins by describing the relevant backgrounds including the frequency response functions (FRFs) in linear dynamics for discrete- and continuous-time systems in Chapter 1. The discussion is first given for single-degree-of-freedom (SDOF) systems and finally generalized to multi-degree-of-freedom (MDOF) systems with an outline of modal analysis. Chapter 2 gives fundamental results and classical approaches to nonlinear systems in structural dynamics. An idea of FRF distortion is also stated there. Chapter 3 discusses FRFs for nonlinear systems in detail and describes how they are used to obtain information about nonlinearity.In Chapters 4 and 5, the Hilbert transformation, which can not only detect nonlinearity but also solve system identification problems, is explained. A mathematical exposition of the method by complex analysis is also presented. In Chapters 6 and 7, several techniques of system identification for discrete- and continuous-time equations are discussed. In Chapter 8, the concept of FRFs is generalized to higher-order FRFs with the assistance of the Volterra series. The generalization presents a method of system identification for MDOF systems. Finally, three experimental examples of a built-in beam rig, automotive shock absorber, and bilinear beam rig (the last of which is motivated from constructing a system with localized damage in the benchmark of fault detection algorithms) are given, and the techniques of the earlier chapters are applied to demonstrate their effectiveness in Chapter 9. This chapter is especially interesting for the reader from a practical point of view. A substantial set of appendices is also valuable for not only the beginners, but also ordinary researchers in the field. In summary, this reviewer recommends Nonlinearity in Structural Dynamics: Detection, Identification and Modeling for students and researchers in structural dynamics who want to study techniques for detection of nonlinearity and system identification in realistic problems.

: Measurements in dynamical systems provide the important data which is used to assess the accuracy of theoretical models and their improvement if necessary, provide monitoring information for damage detection including system aging, etc. Acquiring data from structural systems has traditionally been accomplished using strain gages or conventional accelerometers. However, with the rapidly improving processing capabilities of digital systems, (non-contacting) optically-based transducers are becoming an increasingly popular means of extracting data from experimental systems. The funded grant was used to acquire a state-of-the-art Laser Doppler Vibrometer system to measure the dynamic response of structural and aeroelastic systems of interest to the Air Force. The research program has successfully assessed the robustness of the measurement system in a variety of situations, and provides a strong resource for education of PhD candidates in sophisticated experimental measurements. A further use of this system has been directed toward lightweight inflatable structures, again an area of strong relevance to the research mission of the Air Force for space applications.

A one-sided, unsymmetric block Lanczos algorithm is proposed for the model reduction of structural dynamics systems with unsymmetric damping and/or stiffness matrices. The algorithm is a three-term iteration scheme, which transforms the system matrix into an almost skew-symmetric, block-tridiagonal form. The Lanczos reduced-order model is guaranteed to be stable if the full-order system is stable. For unstable systems, a shifting method is available. Also, the algorithm offers flexibility in the choice of starting vectors and thus can yield more accurate reduced-order models. A linear system example and a plane truss structure example are used to show the efficacy of the proposed method.

Equilibrium point damage prognosis models for structural health monitoring

Sparse structural system identification method for nonlinear dynamic systems with hysteresis/inelastic behavior

Efficient Spectral-Chaos Methods for Uncertainty Quantification in Long-Time Response of Stochastic Dynamical Systems

Efficient reliability assessment of structural dynamic systems with unequal weighted quasi-Monte Carlo Simulation

XII International Conference on Structural Dynamics, EURODYN 2023 EURODYN 2023 was the Twelfth International Conference on Structural Dynamics. It was organised by the European Association for Structural Dynamics (EASD) together with Delft University of Technology (Faculty of Civil Engineering and Geosciences), and it took place from July 2nd to 5th in Delft, The Netherlands. EURODYN 2023 followed earlier successful conferences (years and chairs are indicated as well): Bochum (1990 - W. Kratzig) Trondheim (1993 - T. Moan) Florence (1996 - G. August) Prague (1999 - J. Náprstek) Munich (2002 - H. Grundmann) Paris (2005 - C. Soize) Southampton (2008 - M.J. Brennan) Leuven (2011 - G. De Roeck, G. Degrande and G. Lombaert) Porto (2014 - Á. Cunha) Rome (2017 - F. Vestroni, V. Gattulli and F. Romeo) Athens (2020 - M. Papadrakakis, M. Fragiadakis and C. Papadimitriou) The EURODYN conference has developed into one of the key conferences in Structural Dynamics. EURODYN 2023 was devoted to theoretical, computational and experimental developments in structural dynamics and their applications to all types of structures and dynamical systems, mostly related to Civil Engineering. The conference reflected the state of the art in structural dynamics and dynamical systems in science and engineering practice, and it was a great opportunity to exchange scientific, technical and experimental ideas. EURODYN 2023 covered all major aspects of structural dynamics through Plenary or Semi-Plenary Lectures and numerous Mini-Symposia. The latter are listed in the table below, including the corresponding organisers.

This paper presents a dynamic variable structure system and its controller design conditions. The dynamic variable structure system, which is a class of hybrid dynamic systems, consists of plural subsystems which are switched by switching conditions. A key feature of the dynamic variable structure system is that each subsystem can have different degrees of freedom. In this paper, we employ switching fuzzy models to represent the nonlinear subsystem's dynamics, switching conditions and conservation laws with respect to states, momentum and/or energy of the system. We derive controller design conditions for dynamic variable structure systems.

Progress is reported in these areas: supersymmetry and conformal invariance and new structures in two dimensional critical phenomena; spinor fields and new applications and techniques for studying Ising model correlation factors; superstring compactification and high energy physics applications for novel two dimensional critical points; ordered and disordered spatial structure in dynamical systems; and fermion-boson mass relations in BCS type theories. Research is proposed in covariant formulation of the superstring, topics in superconformal field theory and new structures in two dimensional critical phenomena, ordered and disordered spatial structure in dynamical systems, and field theory over Galois fields. 48 refs. (LEW)

Parameter identification of linear structural dynamic systems

As an alternative to operational modal analysis and classical experimental modal analysis (EMA), a novel method was introduced previously, namely impact-synchronous modal analysis (ISMA). The effectiveness ISMA on rotor and structural dynamic systems has been proven in previous literature. More recently, an automated impact device (AID) was introduced which utilized tachometer pulse as initiation signal and its effectiveness on ISMA was proven. An attempt to further enhance this device in term of equipment and cost is then proposed by replacing the tachometer with the in-use tri-axial accelerometer through utilizing the filtered response of cyclic load component as an initiation signal to control the impact device, which is also the primary aim for this study. Prior to modal testing, accuracy of this device is illustrated at desired phase angles of 0 deg, 90 deg, 180 deg, and 270 deg. Subsequently, frequency response function (FRF) estimations obtained for ISMA using enhanced AID has demonstrated the suppression capabilities of this device on disturbances, i.e., reduction of 93.58% at 30 Hz and 57.78% at 60 Hz, resulting in a high correlation for signature assurance criterion (SAC) and cross signature assurance criterion (CSAC). Modal parameters extracted from the EMA and ISMA using impact device are presented and compared, for the first three natural modes of the test rig. It is found that natural frequencies are deviating by less than 6%, whereas modal assurance criterion (MAC) values between the mode shapes of the two tests are found to be above 0.9.

This study presents an efficient Monte Carlo simulation method to solve multivariate uncertainty problems in structural dynamic systems. The full model is obtained by the adaptive time-step material point method, and the multivariate surrogate model is built and analyzed for uncertainty by the adaptive sparse polynomial chaos expansion. The cubic spline interpolation method serves as a bridge between the original full model and the multivariate surrogate model, which improves the sampling efficiency of Monte Carlo simulation. Numerical results show that the proposed algorithm can significantly improve the efficiency and accuracy of uncertainty analysis.