Staff members at Los Alamos National Laboratory (LANL) produced a summary of the structural health monitoring literature in 1995. This presentation will summarize the outcome of an updated review covering the years 1996 2001. The updated review follows the LANL statistical pattern recognition paradigm for SHM, which addresses four topics: 1. Operational Evaluation; 2. Data Acquisition and Cleansing; 3. Feature Extraction; and 4. Statistical Modeling for Feature Discrimination. The literature has been reviewed based on how a particular study addresses these four topics. A significant observation from this review is that although there are many more SHM studies being reported, the investigators, in general, have not yet fully embraced the well-developed tools from statistical pattern recognition. As such, the discrimination procedures employed are often lacking the appropriate rigor necessary for this technology to evolve beyond demonstration problems carried out in laboratory setting.

A review of structural health monitoring literature 1996-2001

A critical review of the intrinsic nature of vortex-induced vibrations

This article reviews the development of the original modal assurance criterion (MAC) together with other related assurance criteria that have been proposed over the last twenty years. Some of the other assurance criteria that will be discussed include the coordinate modal assurance criterion (COMAC), the frequency response assurance criterion (FRAC), coordinate orthogonality check (CORTHOG), frequency scaled modal assurance criterion (FMAC), partial modal assurance criterion (PMAC), scaled modal assurance criterion (SMAC), and modal assurance criterion using reciprocal modal vectors (MACRV). In particular, the thought process that relates the original MAC development to ordinary coherence and to orthogonality computations will be explained. Several uses of MAC that may not be obvious to the casual observer (modal parameter estimation consistency diagrams and model updating are two examples) will be identified. The common problems with the implementation and use of modal assurance criterion computations will also be identified. The development of the modal assurance criterion 1-2 over twenty years ago has led to a number of similar assurance criteria used in the area of experimental and analytical structural dynamics. It is important to recognize the mathematical similarity of these varied criteria in order to be certain that conclusions be correctly drawn from what is essentially a squared, linear regression correlation coefficient. The modal assurance criterion is a statistical indicator, just like ordinary coherence, which can be very powerful when used correctly but very misleading when used incorrectly. This article will first review the historical development of the modal assurance criterion. Other similar assurance criteria will then be identified although the list is not intended to be comprehensive. Typical uses of the modal assurance criterion will be discussed and finally, typical abuses will be identified.

The modal assurance criterion–twenty years of use and abuse

Past, present and future of nonlinear system identification in structural dynamics

Introduction. 1. Nonlinear theories of elasticity of plates and shells 2. Nonlinear theories of doubly curved shells for conventional and advanced materials 3. Introduction to nonlinear dynamics 4. Vibrations of rectangular plates 5. Vibrations of empty and fluid-filled circular cylindrical 6. Reduced order models: proper orthogonal decomposition and nonlinear normal modes 7. Comparison of different shell theories for nonlinear vibrations and stability of circular cylindrical shells 8. Effect of boundary conditions on a large-amplitude vibrations of circular cylindrical shells 9. Vibrations of circular cylindrical panels with different boundary conditions 10. Nonlinear vibrations and stability of doubly-curved shallow-shells: isotropic and laminated materials 11. Meshless discretization of plates and shells of complex shapes by using the R-functions 12. Vibrations of circular plates and rotating disks 13. Nonlinear stability of circular cylindrical shells under static and dynamic axial loads 14. Nonlinear stability and vibrations of circular shells conveying flow 15. Nonlinear supersonic flutter of circular cylindrical shells with imperfections.

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Nonlinear Vibrations and Stability of Shells and Plates

materials Vincent Lucas, Ling Wu, Maarten Arnst, Jean-Claude Golinval, Stephane Paquay, Ludovic Noels University of Liege (ULg), Department of Aerospace and Mechanical Engineering Chemin des Chevreuils 1, B-4000 Liege, Belgium emails: {Vincent.Lucas,L.Wu,Maarten.Arnst,JC.Golinval,L.Noels}@ulg.ac.be Open Engineering SA, Rue des Chasseurs-Ardennais 7, B-4031 Liege (Angleur), Belgium email: s.paquay@open-engineering.com

Prediction of meso-scale mechanical properties of poly-silicon materials

Because nonlinearity is a frequent occurrence in aerospace applications, there is a need for ecien t analysis procedures. In this context, nonlinear normal modes (NNMs) oer a solid mathematical tool for interpreting a wide class of nonlinear dynamical phenomena. The objective of this study is to highlight the usefulness of NNMs for modeling and testing of nonlinear aerospace structures. Both theoretical and experimental modal analysis are described and are illustrated.

Theoretical and Experimental Modal Analysis of Nonlinear Aerospace Structures

Stiction is a major failure mode of MEMS as microscopic structures tend to adhere to each other when their surfaces enter into contact. Although increasing the restoring forces of switch devices could overcome the stiction effect, this is not practical, as in turn, it also increases the actuation voltage. Therefore stiction prediction is important to be considered when designing micro- and nano- devices. In this paper, the numerical prediction of stiction for capacitive MEMS switches is considered. Toward this end, a micro-adhesive-contact law is derived from previous work and combined with a finite-element model.

Prediction of stiction in microswitch systems

In the field of turbomachinery, various assumptions are usually made to model bladed assemblies, in particular, (1) cyclic symmetry property of a single rotor stage and (2) isolated, dynamically independent rotor stages. The first assumption enables to reduce drastically the required computational resources by considering one sector instead of the entire assembly to model and analyse the dynamic behaviour of the structure. However, even if the bladed disks are designed to be cyclic symmetric, small random blade-toblade variations appear in practice due to manufacturing tolerances, irregularities in the material properties, wear during use, etc. These small variations, known as mistuning, disturb dramatically the dynamic behaviour of bladed disks (energy localization in only a few blades, amplification of the forced response). The second assumption requires the choice of boundary conditions in order to represent constraints normally imposed by adjacent stages, thus enabling the description of the ”global” dynamic behaviour of a single rotor stage in a multi-stage structure. However, this assumption may not accurately describe the disk flexibility locally at the interstage boundaries, leading to an inconsistent representation of the interaction between families of diskand blade-dominated modes. The mixture of blade and disk dominance (i.e., the disk-blade modal interaction) in veering regions is a critical factor to determine the sensitivity of a design to mistuning [1].

Towards a Nonparametric Modelling of Multi-stage Assemblies of Mistuned Bladed Disks

Modal analysis is extensively used for the analysis and design of structures. However, a major concern for structural dynamicists is that its validity is limited to systems showing a linear behaviour. New developments have thus been proposed in order to tackle nonlinear systems among which the theory based on the nonlinear normal modes is indubitably themost appealing. In this study, a different approach is adopted and the modes extracted from the proper orthogonal decomposition are considered for the characterization of nonlinear systems.

Jean-Claude Golinval

Papers

Prediction of meso-scale mechanical properties of poly-silicon materials

Theoretical and Experimental Modal Analysis of Nonlinear Aerospace Structures

Prediction of stiction in microswitch systems

Towards a Nonparametric Modelling of Multi-stage Assemblies of Mistuned Bladed Disks

Proper Orthogonal modes for the characterisation of nonlinear dynamic systems