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The aim of this master thesis is to develop a virtual shaker testing. It allows to predict coupling phenomena between a structure to be tested and the shaker.

The first objective is to model the shaker. To do so, a lumped parameter model is used. The shaker is modelled by three degrees of freedom: the vertical translations of the coil, the table and the body of the shaker. Taken from the literature, the equations of this model are written. They are then implemented in Simulink software. To simulate the dynamics of the shaker, the parameters of this model first need to be identified. A method is therefore developed to compute the mechanical and electrical model parameters. Simulations of shaker vibrations can finally be performed in Simulink. These simulations are validated by experimental vibration tests. 

The second objective of this work is to couple the model of a specimen to the model of the shaker in order to simulate a complete shaker test. In a first time, the specimen is numerically synthesised by a finite element model. An experimental modal analysis is performed to validate the model of the specimen. When this model is validated, a superelement is extracted and is introduced in the Simulink shaker model. A complete test of the shaker/specimen assembly can finally be simulated. The simulations are compared with an experimental test. It is shown that the method gives satisfying results for a small shaker (for example a 445-N shaker) but is less conclusive for a large shaker (such as a 120-kN shaker). The second method consists in building an experimental model of the specimen. To do so, the frequency-based substructuring theory is used to create an experimental superelement. As for the first method, it is introduced in the Simulink shaker model and a complete test is simulated. This method gives similar results to the first one.

Virtual shaker testing --- Electrodynamic shaker --- Lumped parameter model --- Parameter identification --- Model updating --- Testing prediction --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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Most metallic components and structures are subjected, in service, to random or variable amplitude loadings. There are many examples: vehicles subjected to loadings and vibrations caused by road irregularity and engine, structures exposed to wind, off-shore platforms undergoing wave-loadings, and so on. Just like constant amplitude loadings, random and variable amplitude loadings can make fatigue cracks initiate and propagate, even up to catastrophic failures. Engineers faced with the problem of estimating the structural integrity and the fatigue strength of metallic structures, or their propensity to fracture, usually make use of theoretical, numerical, or experimental approaches. This reprint collects a series of recent scientific contributions aimed at providing an up-to-date overview of approaches and case studies—theoretical, numerical or experimental—on several topics in the field of fracture, fatigue strength, and the structural integrity of metallic components subjected to random or variable amplitude loadings.

small cracks --- helicopter flight load spectra --- FALSTAFF flight load spectra --- fatigue crack growth --- surface topography --- optical profilometry --- height digital image correlation --- discontinuous displacements --- triaxial displacements --- fracture analysis --- welded joint --- repair welding thermal shock --- XFEM --- welding linear energy --- high-temperature fatigue --- nickel-based superalloy --- investment casting --- metallography --- turbine blade --- fatigue --- testing systems --- random loadings --- servo-hydraulic --- shaker table --- crack growth --- metallic materials --- plasticity --- crack closure --- spectrum loading --- random loading --- fatigue damage --- power spectral density (PSD) --- spectral methods --- lattice structures --- structural dynamic response --- vibration fatigue testing --- fatigue life prediction --- analytical framework --- fatigue crack --- residual strength --- retardation effect --- nonstationary random loadings --- run test --- short-time Fourier transform --- n/a

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Manufacturers of soft polymer products, as well as suppliers and processors of polymers, raw materials, and compounds or blends are compelled to use predictive and advanced laboratory testing in their search for high-performance soft polymer materials for future applications. The collection of 12 publications contained in this edition therefore presents different methods used to solve problems in the characterization of various phenomena in soft polymer materials, asks relevant questions and offers appropriate solutions.

Research & information: general --- Physics --- ultraviolet radiation --- thermoplastic elastomer --- high vinyl S-B-S --- photoinitiator --- mechanical properties --- rubber --- curing --- bismaleimide --- tensile strength --- Diels–Alder reaction --- effective electrical resistance --- elastomer sensors --- natural rubber --- local strain --- conductive filler --- digital image correlation --- strain sweep --- rheometer --- rubber process analyzer --- swelling --- absorption --- infrared spectroscopy --- mass spectrometry --- gas chromatography --- mechanical behavior --- synthetic aviation fuels --- 3D printed elastomers --- elastomer --- fast characterization --- energy stored and released --- heat source reconstruction --- intrinsic dissipation --- infrared thermography --- engine mount --- elastomer characterisation --- experimental testing --- resonance frequency --- dynamic stiffness --- parameter identification --- electrodynamic shaker --- test bench --- cogging torque --- synchronous machine --- carbon black --- tensile --- Mullins effect --- Payne effect --- dynamic strain --- hysteresis --- material testing --- rheology --- Poisson’s ratio --- viscoelasticity --- plasticizer --- polarity --- carbon black network --- simultaneous mechanical and dielectric analysis --- mechanical stability --- glass transition --- kinetics --- resin --- BDS --- FDSC --- nanocomposites --- carbon nanotubes --- atomic force microscopy --- dynamical mechanical analysis