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In many engineering applications, the vibration analysis of a structure requires the set up of a large number of sensors. These studies are mostly performed in post processing and based on linear modal analysis. However, many studied devices highlight that modal parameters depend on the vibration level non linearities and are performed with sensors as accelerometers that modify the dynamics of the device. This work proposes a significant evolution of modal testing based on the real time identification of non linear parameters (natural frequencies and damping) tracked with a linear modal basis. This method, called Kinematic-SAMI (for multiSensors Assimilation Modal Identification) is assessed firstly on a numerical case with known non linearities and secondly in the framework of a classical cantilever beam with contactless measurement technique (high speed and high resolution cameras). Finally, the efficiency and the limits of the method are discussed. [ABSTRACT FROM AUTHOR]

This paper deals with the use of piezoelectric patches for nonlinear dynamic identification. The patches are glued on the structure to identify amplitude-dependent damping and natural frequency; their positions are defined in order to perform the excitation concentrated on the first bending mode. Their locations on the structure allow to perform “stop sines” tests, as, unlike electrodynamic shakers, piezos are embedded on structures and do not modify the studied structure after the excitation signal is switched off. Although, despite the piezo and the stop-sine , the signal is still modulated by other frequency components or polluted by random signals, a post processing with the extended Kalman Filter allows a very good determination of the modal damping and the natural frequency, especially when they depends on the free vibration amplitude. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is to investigate non linear dynamic behavior of viscoelastic components. The dynamic characteristics of viscoelastic components depend on frequency, amplitude, preload, and temperature. A Non Linear Generalized Maxwell Model (NLGMM), with only 4 independent parameters, is proposed. The NLGMM is based on the separation between the linear viscoelasticity and the non linear stiffness. This assumption is validated on a large range of experimental measures. The NLGMM can be used for different kinds of excitations in non linear dynamics: periodic, transient or random excitations. The non linear stiffness is represented by a simple polynomial function. Comparisons between measures and computed values have been carried on several viscoelastic samples. The NLGMM shows a good accordance with experimental results. [Copyright &y& Elsevier]

Abstract: This work describes an automatic method for removing modulated sinusoidal components in signals. The method consists in using the Optimized Spectral Kurtosis for initializing Series of Extended Kalman Filters. The first section is an introduction to vibration applications with Kalman Filters and modulated sinusoids. The detection process with OSK is described in the second section. The third section concerns the tracking algorithm with SEKF for amplitude and frequency modulated sinusoidal components. The last section deals with the complete process illustrated with an experimental application on a rotating machine. [Copyright &y& Elsevier]

Abstract: This paper deals with the damping caused by friction in joints. A new test bench is presented and justified by comparisons made with devices described in the literature. The purpose of this academic bench is to measure the damping induced by partial slip and friction in a planar joint. Moreover, allows uncoupling normal static and dynamic tangential forces. A new method for so-called stopped-sine excitation was developed. It allows more precise monitoring of the evolution of the vibration frequency and damping of non-linear modes. This method is associated with piezoelectric exciters for greater efficiency when stopping excitation. A large number of experimental results are presented and discussed. They are used to characterize the damping induced by micro-sliding in the bonds. [Copyright &y& Elsevier]

Abstract: This paper focuses on the generalized Maxwell model (GMM) identification. The formulation of the transfer function of the GMM is defined, as well as its asymptotes. To compare identification methods of the parameters of the GMM, a test transfer function and two quality indicators are defined. Then, three graphical methods are described, the enclosing curve method, the CRONE method and an original one. But the results of graphical methods are not good enough. Thus, two optimization recursive processes are described to improve the results of graphical methods. The first one is based on an unconstrained non-linear optimization algorithm and the second one is original and allows constraining identified parameters. This new process uses the asymptotes of the modulus and the phase of the transfer function of the GMM. The result of the graphical method optimized with the new process is very accurate and fast. [Copyright &y& Elsevier]

The behaviour of dynamical systems is modified by the use of viscoelastic materials. In order to lead realistic complex eigenvalues analysis on dynamical systems, one need to model the behaviour of viscoelastic materials. The experiments show that the stiffness and the damping of such materials are frequency dependent. A large number of models often used are not able to describe this dependence; this is why the generalised Maxwell's model has been chosen. This paper describes a method based on modulus and angle curves to identify the parameters of this model. Between all the different formulations of generalized Maxwell, the pole-zero formulation is the most suited to lead the identification. However, some formulas allow to find the parameters of others formulations like the Prony one. The identification method presented here is based on the asymptotic curves of generalised Maxwell's model. This identification is led in two step, first parameters are initialised and second they are optimised. This method is confronted to others ones. If several viscoelastic materials have to be modelled in the same dynamical system, the size of the finite element model grows as quick as the number of poles. A way to reduce this size consists in constraining the poles to be equal for all materials. The method presented in this paper allows to perform the identification by taking this new constraint into account. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops an experimental and numerical study of dynamic phenomena involving gear impacts with one loose gear (non-engaged gear pair) inside an automotive gearbox. A dedicated test bench was designed for this study. Signal processing tools, based on the Order Tracking Method, were specially developed in order to clarify the underlying phenomena. A particular attention was paid to the relationship between the drive shaft excitation and the energy and nature of impacts. A topological model of contact is being proposed, based on a geometric description of solids in contact. The contact between gear meshes is defined using a Single Degree of Freedom, non-linear, elastic and dissipative model. The chosen parameters of the model are not updated from measurements, but from the knowledge of the gear topology and tolerance class. Simulations, compared with experimental results, confirm the accuracy of the model proposed. Both model and experiments show, for particular excitation conditions, the emergence of repeated impacts on one side of the gear mesh. [Copyright &y& Elsevier]

Abstract: A new sonoreactor technology is presented here which should give a decisive impulse to sonochemistry in various areas of chemical processing. These exclusive systems use high power converging acoustic waves in a tube to produce a relatively large volume confined acoustic cavitation zone in flowing liquid reagents under pressure. It is well known that numerous chemical reactions are strongly accelerated when they take place inside such a zone. The new cylindrical sonoreactors do not contaminate the processed liquids with erosion products as most other devices do since the cavitation zone is maintained away from the wall of the tube. The processing conditions can be widely varied with pressure, power, temperature, and flow rate. The processing capacity of the largest models may be up to several tons per hour, depending on the required cavitation energy per unit volume to produce the desired process enhancement, using an electric power input of about 50kW. [Copyright &y& Elsevier]

Presents a study which examined the configuration of class D amplifiers or inverters with field effect transistors for piezoelectric transducers. Operating principles of the inverters; Results; Conclusion.

• Nonlinear filtering analysis. • Vibration comfort metric for embedded systems in articulated mechanism. • Kinematic solver based on generalised cross product. Ground vehicle architectures are designed to prevent the transmission of vibration, shock, and noise from the ground profile under operating conditions. The choice of a kinematic architecture strongly contributes to the filtering efficiency of the complete system and has to be considered before the efficiency of the suspension components. In order to highlight the filtering contribution of architectures, all flexible (and dissipative) behaviours are removed in studied models: all the components are assumed as rigid bodies. Thus, this paper focuses on the kinematic filtering performed by ground vehicle architectures, especially articulated suspension systems. The proposed methodology for studying the filtering efficiency of ground vehicle architectures is described and illustrated by the study of a single wheel to that of the rocker-bogie system used for the rover Curiosity, passing through the intermediate case of a bicycle. Firstly, an original and robust method is proposed in order to simulate this type of mechanism. For this purpose, the kinematics of the studied system is defined by algebraic equations transformed into a set of ordinary differential equations by using an adaptation of the generalized cross product. Secondly, the nonlinear filtering effect of the kinematic function of the system is studied and discussed. This paper provides a set of nonlinear analysis tools applied to kinematics of a ground vehicle, to characterize and analyse architectural designs. The two main contributions of this work are, first, a kinematic solver method based on generalised cross product, and secondly, dedicated vibration comfort metrics for embedded systems in articulated mechanism (based on nonlinear filtering analysis). [ABSTRACT FROM AUTHOR]

Presents a computation technique for one-dimensional piezoelectric transducers, resonators, or interferometers having an arbitrary number of layers and piezoelectric elements electrically in parallel. Theoretical analysis of the piezoelectric elements; Experimental confirmations of the computational results; Conclusions.

The aim of this paper is to describe the development of a reduced order model for modal analysis in a design context. The design process of most industrial systems is based on the re-utilization of certain components. Here, we propose a reduction method involving component eigenmodes to recover the modal behaviour of an assembled structure. The contribution of this work is that it uses component eigenmodes to build an interface reduction basis. Lastly, the reduction methodology proposed is compared to the Craig and Bampton method by applying it to two case studies of which one is an industrial model of an open rotor blade. [ABSTRACT FROM AUTHOR]

This paper investigates the rocking behavior of rigid bodies seismically protected by means of lead rubber bearings and high damping rubber bearings, which are the most popular kinds of elastomeric isolators in the market. The complex nonlinear force–displacement relationship displayed by such devices is predicted by a phenomenological model based on a small set of parameters having a clear mechanical meaning. The algebraic nature of the proposed hysteretic model makes it suitable for a design procedure, using an energy‐based approach, that allows one to obtain the hysteretic model parameters on the basis of the mass and the isolation period. Overturning spectra are evaluated and discussed to illustrate the effect of the isolation devices on the rigid bodies' rocking behavior. Furthermore, nonlinear time history analyses associated with six real earthquakes are carried out on six of Michelangelo's sculptures, located in the Galleria dei Prigioni at the Accademia Gallery of Florence, in order to examine their actual behavior under real strong ground motions. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new method to measure the vibrations of a 3D mechanical structure. It requires only a video sequence taken by a single camera and a Finite Element model of the structure. First, the intrinsic and extrinsic parameters of the camera are identified. Then, a collection of numerical deflection shapes and normal modes are projected in the image frame of the camera. This is done thanks to a linearization of the perspective projection model. Comparing the motion of targets seen by the camera and the motion of Finite Element model at the same location gives the time evolution of modes amplitude. Finally the motion of the model is reconstructed in 2D in the image frame and in 3D in the world frame. By following this procedure, vibration amplitude can be magnified applying a scale factor on a modal basis covering a large frequency bandwidth. • New method for 3D vibrations reconstruction with only one camera. • 3D vibrations are identified by projection on the image frame of FE eigenmodes. • Projection is done thanks to a linearization of the perspective projection. • Vibration can be magnified thanks to the scale factor of the eigenmodes. • Extension to several cameras is possible without any overlapping field of view. [ABSTRACT FROM AUTHOR]

Industry 5.0 advocates for a sustainable industry, particularly in terms of energy. One of the most fundamental elements of comprehension is knowing when the systems are operated, as this is key to locating energy intensive subsystems and operations. Such knowledge is often lacking in practice. Activation statuses can be recovered from sensor data though. Some non-intrusive sensors (accelerometers, current sensors, etc.) acquire mixed signals containing information about multiple actuators at once. This paper considers different industrial settings in which the identification of binary sub-system activation sequences is sought. In this context, source signals are assumed to be quasi-stationary and they may be correlated. Existing methods either restrict these assumptions, e.g. , by imposing orthogonality or noise characteristics, or lift them using additional assumptions, typically using nonlinear transforms. This paper addresses these limitations, and introduces the unsupervised complex semi-binary matrix factorization (ℂ SBMF) as its main contribution. In particular, we show that the exact recovery of source activation sequences from non-intrusive sensor data is intrinsically tied to the presence of problematic phase shifts, the causes of which are detailed. A greedy algorithm is proposed, iteratively resynchronizing sources to converge towards the maximum decomposition of each operation despite these phase shifts. The ℂ SBMF is verified and compared to existing techniques on synthetic use cases, then validated on experimental data with signals of different nature. To that occasion, the CAFFEINE dataset for unsupervised time series multi-label classification is introduced. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical joints in assembled structures cause energy dissipation due to micro-slip in contact and softening effects that play an important role in the dynamic behavior of such structures. The contact non-linearity is governed by micro and meso-scale parameters (geometry, roughness, local pressure, etc.) and as a result cannot be included in a macro-size model of a whole structure because of the computational cost. The present paper investigates the idea of using the normal modes of the linearized structure as boundary conditions on a detailed model reduced to the joints only. Since contact non-linearities alter mode shapes, they are corrected as vibrational energy increases. The method relies on a corrected quasi-static formulation associated with the Masing hypothesis. These assumptions circumvent considerable numerical expense due to the non-linear dynamics. The formulation of the method is detailed and investigated on a lap-joint benchmark. [Copyright &y& Elsevier]

Abstract: The operating deflection shape of a pad during squeal noise is measured on a real brake system with three-axis accelerometers. A time-frequency analysis is performed that highlights the dependency of squeal on the hydraulic pressure of the system and shows that squeal occurs simultaneously with harmonic components. The operating deflection shape of this pad before and during squeal is then visualized using interpolation, showing the predominance of bending motion. Finally, the pad motions observed are compared to the real modal basis of a detailed Finite Element model. [Copyright &y& Elsevier]

Herein we develop a creep test method for characterizing nonlinear viscoelastic behaviour of an elastomer through weak deformation. This approach is based on an expanded Schapery model. Short term creep tests at various stress levels were performed upon specimens composed of a synthetic elastomer. A method to predict the long term creep behaviour using short term creep tests is presented. Experimental results and theoretical predictions are compared. [ABSTRACT FROM AUTHOR]

Friction modeling is essential in a vast amount of engineering applications. In this paper Mindlin contact friction model, a Masing rule compliant model, is manipulated in order to find a correlation with Dahl dynamic friction model, a Masing rule not compliant model. The resulting equations are then numerically compared and the correlation demonstrated with several loading functions. The result is a modified Dahl model that captures the partial slip behavior following the contact theory. The Dahl model, classically used in control engineering as an empirical model due to its implementation facility, finds in this new formulation a physical meaning to its parameters and finally identified physical parameters (according from Mindlin model) for the Dahl model. [ABSTRACT FROM AUTHOR]

This paper describes a method for the identification and the tracking of poles of a weakly nonlinear structure from its free responses. This method is based on a model of multichannel damped sines whose parameters evolve over time. Their variations are approximated in discrete time by a nonlinear state space model. States are estimated by an iterative process which couples a two-pass Bayesian smoother with an Expectation-Maximization (EM) algorithm. The method is applied on numerical and experimental cases. As a result, accurate frequency and damping estimates are obtained as a function of amplitude. [ABSTRACT FROM AUTHOR]

In the context of brake system simulation, the highlight of phenomenon like squeal needs specific methods. We will focus on stability analysis by complex modal analysis. The use of damping system called shims for squeal noise reduction implies that simulations take into account the damping of materials. To do this, we use parametric viscoelastic models and particularly the generalised Maxwell model. Work consisted in tools choice and validation (viscoelastic models, finite elements formulations, ...) and in simulation method implementation. It was divided in several steps. In a first step, we have selected, among several mathematical models able to describe viscoelasticity, the best for damping modelisation in brake systems. We studied the complex modulus model, the Kelvin-Voigt model and the generalised Maxwell model. In a second step, we sought a formulation of the finite element problem adapted to the modal analysis. We then used a state space model formulation. A capital hypothesis on the equality of the pole of the generalised Maxwell model permits to reduce the size of the model and in the same time to simplify its formulation. Finally, the developed methods have been applied to simulate a pad and a full brake system. The influence of the number of modes used in model reduction and the order of the Maxwell model has been quantified in parametric studies. In the pad case, we performed a complex modal analysis with friction material considered as viscoelastic. The objective was to update the pad frequencies and damping according to FRF measures. In the brake case, we performed a complex modal analysis with the two friction materials and one shim considered as viscoelastic. This model has also been used to exhibit the link between the strain energy distribution in the brake and the damping level obtained by complex modal analysis. To conclude, we developed a simulation method using Abaqus® and Matlab® for the complex modal analysis with viscoelasticity effects and Python to make data exchange between Abaqus® and Matlab® possible. This method permits to perform stability analysis with several viscoelastic materials, on large models, without degradation of computation time. [ABSTRACT FROM AUTHOR]

• A novel model for non-ideal energy source rotors operating at non-constant speed and very high regime is proposed. • The finite element model with 6 dof per node superimposes the torsional deformation and the nominal intrinsic rotation in one variable. • A particular attention is paid to the coupling between the lateral and torsional behavior induced by the gyroscopic effect and the mass unbalance. • The better estimation of the vibratory behavior obtained by the fully coupled new model is exhibited through the comparison of the numerical results with other uncoupled models. • The model is particularly suitable for the study and the design of multi rotors connected by gears or flexible couplings and going through several critical speeds. In the automotive industry, high-speed elecrical engines will be used in a very large range of speeds, leading to non-stationary operating conditions. Thus more critical speeds may be crossed a very large number of times during the whole life-time of the engine. Therefore, estimating accurately the non-stationary loads and deformations during these transient regimes is of first importance for a correct design. In this paper, we propose a novel dynamic model for unbalanced high-speed rotors with less restrictive assumptions. The finite element model accounts for flexion, torsion and traction-compression leading to six degrees of freedom on each node. The non-ideal energy source is considered and the rotor is running under non-stationary operating conditions and crossing supercritical speeds. The angular displacement is defined in such a way that it combines simultaneously the intrinsic nominal rotation and the torsional deformation. The comparison of the proposed model with other models under different assumptions on the energy source and on the bending-torsion coupling shows that our model offers more accurate prediction for both lateral and torsional vibrations when crossing critical speeds. The ability of the proposed model to account for the mutual influence between lateral and torsional behavior is highlighted and is exhibited through time-frequency analyses. [ABSTRACT FROM AUTHOR]