Rozprawy doktorskie na temat „Cantilever beam experiment”

Design of the mechanical components greatly depends on their expected structural performances. In modern design applications these performances are quantified by computer-based analysis and occasionally confirmed by experimental measurements or theoretical calculations. The dependency of the mechanical product to the structural analysis process is more significant under the product’s multi-functionality aspect that requires analyses for a variety of Variable Input Parameters, to obtain various structural responses and against more than one failure or design criterion. Structural analysis is known as the expert field, which requires an upfront investment and facilitation to be implemented in commercial design environment. On the other hand, the product design process is a systematic and sequential activity that put the designer in the central role of decision making. Lack of mutual understanding between these two disciplines reduces the efficiency of the structural analysis for design. This research aims to develop an integrated methodology to embed the structural analysis in the design process. The proposed methodology in this research combines the benefits of state-of-the-art approaches, early simulation and Validation and Verification practice, towards the specified aim. Moreover the novelty of the proposed methodology is in creative implication of Quality Function Deployment method to include the product’s multi-functionality aspect. The QFD-Based Design Integrated Structural Analysis methodology produces a reliable platform to increase the efficiency of the structural analysis process for product design purpose. The application of this methodology is examined through an industrial case-study for the telescopic cantilever boom, as it appears in Access platforms, and Cranes products. Findings of the case-study create a reliable account for the structural performance in early stages of the design, and ensure the functionality of the proposed methodology.

The telescoping cantilever beam structure is applied in many different engineering sectors to achieve weight/space optimisation for structural integrity. There has been limited theory and analysis in the public domain of the stresses and deflections involved when applying a load to such a structure. This thesis proposes (a) The Tip Reaction Model, which adapts classical mechanics to predict deflection of a two and a three section steel telescoping cantilever beam; (b) An equation to determine the Critical buckling loads for a given configuration of the two section steel telescoping cantilever beam assembly derived from first principles, in particular the energy methods; and finally (c) the derivation of a design optimization methodology, to tackle localised buckling induced by shear, torsion and a combination of both, in the individual, constituent, hollow rectangular beam sections of the telescopic assembly. Bending stress and shear stress is numerically calculated for the same structure whilst subjected to inline and offset loading. An FEA model of the structure is solved to verify the previous deflection, stress and buckling predictions made numerically. Finally an experimental setup is conducted where deflections and stresses are measured whilst a two section assembly is subjected to various loading and boundary conditions. The results between the predicted theory, FEA and experimental setup are compared and discussed. The overall conclusion is that there is good correlation between the three sets of data.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 50-52.
by John M. Plump.
M.S.

Term of remote-lab is certain types of laboratories which practical experiments are directedfrom a separate area by remote controller devices. This study is part of developing andupgrading advanced vibration remote laboratory. In the new remote lab, users have theability to measure the dynamic characteristics of the test object similar to the current existingremote lab. But in addition to current existing remote lab, they are capable to modifydynamic properties of the test object remotely by attaching vibration test instruments; such asa block of mass, spring-mass or non-linear spring. Doing several accurate experimental testsremotely on the test object are the toughest issues we faced as designers. In creating anddeveloping of this remote-lab, number of different approaches was adopted for producingwell-defined tests. Also, instead of implementing routine devices and techniques for regularvibration laboratories, the new prototypes were designed by finite elements method (FEM)and LABVIEW. For instance, the desirable test object, the attachment mechanism, usefulapplications, and proper software for managing via internet were prepared.

This thesis is part of the on going work at BTH (Blekinge Technical University) to develop a remote lab for Sound and Vibration Experiments. The aim of this undertaking is to develop a Spectrum Analyzer that can simultaneously take inputs from 10 sensors and be able to measure the Power Spectral Density, Cross correlation, Frequency Response Functions (FRF) and coherence. The Interface and analysis algorithms are developed inLabview programming language. The thesis starts by introducing the overall aim of the project and its scope, the place of this particular thesis in the whole picture and the algorithms used for analysis are introduced. In the second part of the thesis the development of the software is explained and the main aim is to thoroughly document the software. This part of the thesis explains Labview programming concepts in detail to make it easier for other students who want to undertake theses to continue this work and who may not have experience of Labview programming.Two versions of the spectrum analyzer were developed. The third part explains theexperimental set up and results obtained and compares measurements to those obtained using other spectrum analyzers. An accurate Spectrum Analyzer Virtual Instrument has been developed and tested during this thesis project and it can be used as a component of the proposed Sound and vibration analysis laboratory and also for general Spectral Analysis tasks.
Good guide to learn Labview and sound and vibration analysis..
fkul08@gmail.com Is my email and i can be contacted via messenger usually at farooq_kifayat@hotmail.com And i can also be contacted via skype using farooqkifayat as my name. I move around a lot so i have no permanent address that stays longer than half a year .

L'etude demontre la faisabilite d'un micro commutateur opto-mecanique a commande electrostatique, destine a la commutation spatiale dans les reseaux de fibres optiques (longueur d'onde: 1,3 m et 1,55 m). Ce commutateur a ete realise en combinant les techniques de l'optique integree et du micro-usinage sur silicium. Une etude theorique du circuit optique est conduite pour determiner les pertes optiques, l'isolation inter-voies et la sensibilite a la polarisation. Puis la deviation electrostatique de la poutre mecanique est modelisee et les sensibilites du composant aux vibrations, aux accelerations et a la temperature sont evaluees. Les contraintes residuelles dans la silice, a l'origine des deformations parasites des structures mecaniques, sont etudiees. Les comportements mecaniques sont relies aux phenomenes physiques regissant les contraintes intrinseques. Les solutions technologiques developpees pour controler les deformations parasites sont decrites: traitement thermique, systeme de compensation mecanique et bilame thermique. La caracterisation des composants debute par l'etude experimentale de la deviation mecanique des poutres par la commande electrostatique. Puis le fonctionnement optique des micro commutateurs est caracterise, en terme de pertes optiques fibre a fibre, d'isolation optique des voies de sortie, de sensibilite a la polarisation, de tension de commande et de temps de reponse. Enfin, un micro commutateur mettant en uvre un peigne electrostatique et un fonctionnement tirant parti du phenomene d'instabilite electrostatique du systeme est presente. Il a permis d'atteindre une faible tension de commande tout en conservant de bonnes performances optiques. Les meilleures performances obtenues sont suivantes, a 1300 nm: pertes fibre a fibre: -2. 5 db, isolation: 40 db, tension de commande: 28 v, temps de reponse: 0,8 ms

碩士
中原大學
機械工程研究所
91
This study performs precision position control of the piezoelectric cantilever beam with consideration of nonlinearity. Two different dynamic models were obtained. The first one is derived in the forms of linear systems through application of basic physic laws of piezoelectric material, Hamilton’s principle and modeling technique of finite elements. The second one is established as in through experimentally-obtained frequency responses. With theoretical models in hand, the controllers aimed to perform precision positioning of the piezoelectric cantilever beam are next designed to work for a pickup actuator in optical disc drives, which ought to suppress the vibratory disturbance caused by the rotation of the disc. Two types of controllers, PI-and-lag-lead compensator and H∞ controller, are synthesized herein to perform the precision positioning due to the simple structure of the PI-and-lag-lead one and the robustness achieved by the H∞ one. Note that the H∞ controller designed herein would able to work against plant uncertainty, sensor noise and the extraneous disturbance caused by the eccentric rotation of the disk. Simulations are performed to validate the performance expected by previously-designed controllers. Finally, experiments are conducted to verify the effectiveness foreseen by simulations.

Inverse problems are very challenging as these problems involve, finding the cause by analyzing the effects. In structural dynamics problems, the effects are normally measured in terms of dynamic responses in structures. These responses which are used to find the cause generally have partial data, embedded with measurement noise, and are truncated. Due to these problems, inverse problems are generally ill-posed in most cases as against forward problems. In this dissertation, we solve five different types of inverse problems involving high-frequency transient loads. All these problems are solved using the time-domain spectral element method (TSFEM) along with experimental or numerically simulated responses. The dissertation starts with the formulation of the forward problem, which is obtaining the responses from known input forces. The general formulation of TSFEM of composite Timoshenko beam is derived. The isotropic beam formulation is shown as a special case in this formulation. Five different inverse problems solved in the thesis are: 1. Force identification problem: A new algorithm is developed using a 1-D waveguide, involving an eight noded spectral finite element. The force identification is carried out, using a few measured responses on the structure, and using TSFEM we reconstruct the input force. This is followed by a portal frame example to demonstrate the wave reflection complexities. New procedures are developed to use various types of response data like displacement, velocity, acceleration, and strain to identify the force. 2. Material identification problem: A new procedure making use of the developed TSFEM, few responses, and nonlinear least square techniques are used to determine the material properties. Also, we show the case, in which we derive the material properties without force input consideration. 3. Crack location detection problem: A new procedure is developed using TSFEM and mechanics of crack. Three methods are described, in which the first method uses only responses and wave speeds to determine the location of the crack. In the second method, force reconstruction using the measured responses is carried out and this, in turn, is used to determine the location of the crack. The third method uses the residues of the actual force and the reconstructed forces using the healthy beam matrices and cracked beam responses. A new procedure to identify the crack location using a general force input pulse having many frequency components is also developed. 4. Material defect identification: Material defects like voids or density changes are identified using TSFEM. Location and magnitude of defect are identified using response computation and using the method of residues. 5. Porous location and identification in a composite material: TSFEM is used to construct a porous element and this is used along with a healthy beam to generate the responses. A force reconstruction algorithm is used to identify the location of the porous element. The Force residue method to identify the location of the defect is also demonstrated. Further, we make use of the material identification algorithm with a few modifications to evaluate all the parameters for the porous element.

Beam is an inclined or horizontal structural member casing a distance among one or additional supports, and carrying vertical loads across (transverse to) its longitudinal axis, as a purlin, girder or rafter. In Euler – Bernoulli beam theory, shear deformations and rotation effects are neglected, and plane sections remain plane and normal to the longitudinal axis. In the Timoshenko beam theory, plane sections still remain plane but are no longer normal to the longitudinal axis. In this paper, we will be formulating the equations of motion of a free cantilever beam. The natural frequency of continuous beam system will be found out at different variables of beam using ANSYS 14.0. The results will be compared further using experimentation by free vibration of a cantilever beam. Using those results, we will be able to compare the parameters in Euler-Bernoulli and Timoshenko beam. Free vibration takes place when a system oscillates under the action of forces integral in the system itself due to initial deflection, and under the absence of externally applied forces. The system will vibrate at one or more of its natural frequencies, which are properties of the system dynamics, established by its stiffness and mass distribution. The comparative displacement alignment of the vibrating system for a particular natural frequency is known as the Eigen function in continuous system. The mode shape of the lowest natural frequency (i.e. the fundamental natural frequency) is termed as the fundamental (or the first) mode frequency. The displacements at some points may be zero which are called the nodal points. Generally nth mode has (n-1) nodes excluding the end points. The mode shape varies for different boundary conditions of a beam.

abstract: Uranium Dioxide (UO2) is a significant nuclear fission fuel, which is widely used in nuclear reactors. Understanding the influence of microstructure on thermo-mechanical behavior of UO2 is extremely important to predict its performance. In particular, evaluating mechanical properties, such as elasticity, plasticity and creep at sub-grain length scales is key to developing this understanding as well as building multi-scale models of fuel behavior with predicting capabilities. In this work, modeling techniques were developed to study effects of microstructure on Young’s modulus, which was selected as a key representative property that affects overall mechanical behavior, using experimental data obtained from micro-cantilever bending testing as benchmarks. Beam theory was firstly introduced to calculate Young's modulus of UO2 from the experimental data and then three-dimensional finite element models of the micro-cantilever beams were constructed to simulate bending tests in UO2 at room temperature. The influence of the pore distribution was studied to explain the discrepancy between predicted values and experimental results. Results indicate that results of tests are significantly affected by porosity given that both pore size and spacing in the samples are of the order of the micro-beam dimensions. Microstructure reconstruction was conducted with images collected from three-dimensional serial sectioning using focused ion beam (FIB) and electron backscattering diffraction (EBSD) and pore clusters were placed at different locations along the length of the beam. Results indicate that the presence of pore clusters close to the substrate, i.e., the clamp of the micro-cantilever beam, has the strongest effect on load-deflection behavior, leading to a reduction of stiffness that is the largest for any location of the pore cluster. Furthermore, it was also found from both numerical and i analytical models that pore clusters located towards the middle of the span and close to the end of the beam only have a very small effect on the load-deflection behavior, and it is concluded that better estimates of Young's modulus can be obtained from micro- cantilever experiments by using microstructurally explicit models that account for porosity in about one half of the beam length close to the clamp. This, in turn, provides an avenue to simplify micro-scale experiments and their analysis.
Dissertation/Thesis
Masters Thesis Mechanical Engineering 2015

碩士
中原大學
機械工程研究所
92
This study is devoted to model vibrations of the piezoelectric cantilever beam via the finite element method (FEM), which are compared with the experimental results. To this end, the kinetic energy and the potential energy of the system are first derived from the basic physic laws of piezoelectric ceramics, the constitutive equations of the piezoelectric material, in terms of degrees of freedom of nodes. The governing equation of system is established by the uses of FEM technique and Lagrange’s equation for formulation. The case of a bimorph piezoelectric cantilever beam is considered to verify the validness of the modeling technique proposed. Numerical simulations and experimental study are next conducted and compared to ensure the effectiveness of the modeling method. In experiment, the displacement of the piezoelectric cantilever beam is measured by a laser displacement sensor, and then the sensor signal is feedbacked to a spectrum analyzer which is capable of showing the frequency response of the real system. The differences between the numerical simulations and those of experiments are small and non-critical, which confirm the efficacy of the proposed modeling technique.

碩士
國立虎尾科技大學
機械與機電工程研究所
98
The vibration of a highly flexible cantilever beam is investigated. The order three equations of motion, developed by Crespo da Silva and Glyn (1978), for the nonlinear flexural-flexural-torsional vibration of inextensional beams, are used to investigate the time response of the beam subjected to harmonic excitation at the base. The equation for the planar flexural vibration of the beam is solved using the finite element method. The finite element model developed in this work employs Galerkin''s weighted residuals method, combined with the Newmark technique, and an iterative process. We further apply 0.3g, 1g, 2.5g, 2.97g accelerations in our experimental work and observe the FFT variations. The results show reasonable agreement between theoretical and experimental data at resonant frequencies. The computations are also extended to study the impacts on FFT resulting from material properties, damping, geometries of the excited beam. Keywords：Nonlinear Vibration、Cantilever Beam、FEM、FFT

碩士
華梵大學
機電工程研究所
87
In this investigation, the effect of attached masses and stiffness on the dynamics properties of cantilever beams is examined. By using the Euler-Beam wave equation, the theoretical solution associated with both geometric and natural boundary conditions at two ends can be obtained in the closed form using the method of the separation of variables. The roots of the frequency equation associated with the mass ratio and stiffness ratio can be determined numerically and the orthogonality relationships of the related mode shapes are identified. The expressions for the kinetic and strain energies are derived in terms of the modal mass and stiffness coefficients, respectively and the conservation of energy for the system are also verified. The frequency response functions between the impact hammer (actuator) and the accelerometer (sensor) are experimental measured. By the operation of a series of frequency response functions, the system natural frequencies and corresponding mode shapes can be obtained. The solution of the numerical analysis is also obtained using the finite element method and is compared with the solutions obtained using theoretical and experimental methods. The results show that those approaches agree very well.

This dissertation focuses on the design, modeling, characterization and experimental verification of a class of nonlinear energy sink, based on a cantilever beam vibrating laterally between two specially shaped surfaces that limit the vibration amplitude, thus providing a variable beam length throughout its deflection, therefore producing a smooth nonlinear restoring force. First, a methodology to evaluate and visualize the energy interactions between the nonlinear energy sink and its host structure is developed. Then, an semi-analytical dynamic model for simulating the device under actual working conditions is proposed, and finally, an experimental verification step is conducted where the numerical results are compared and correlated to the experimental results.

L'inquinamento ambientale è, al giorno d'oggi, uno dei più grandi problemi mondiali da risolvere ed è strettamente collegato ad altre importanti problematiche, quali, ad esempio, l'aumento del numero di pazienti affetti da malattie ad esso correlate. Malgrado ciò, la percentuale di impiego di fonti di energia notoriamente inquinanti è ancora molto elevata rispetto alla percentuale riservata alle energie 'pulite' e rinnovabili, il che ha indotto i ricercatori a condurre numerosi studi sulle energie alternative. L'obiettivo di questi studi si concilia bene con la filosofia di una scienza che studia la conversione dell'energia sprecata nell'ambiente in forme di energia diverse e più utili: questa scienza si chiama Energy Harvesting (EH). E' possibile recuperare energia da fonti ambientali naturali quali il sole, il vento e le vibrazioni naturali. L'energia prodotta da alcune di queste fonti alternative può essere convertita in energia elettrica attraverso processi non inquinanti che utilizzano opportuni dispositivi, chiamati energy harvester; essi funzionano da veri e propri generatori quando sono sottoposti all'effetto delle vibrazioni. Il processo di conversione dell'energia ambientale in energia elettrica comporta spesso l'utilizzo di smart materials quali, ad esempio, i materiali piezoelettrici. Questi materiali hanno la proprietà di sviluppare cariche elettriche nel momento in cui sono sottoposti a sollecitazioni meccaniche (effetto piezoelettrico diretto): le cariche prodotte possono essere immagazzinate e conservate utilizzando un circuito elettrico. Una vasta gamma di dispositivi realizzati con materiali piezoelettrici è stata sviluppata nel campo dell'EH. In particolare, stanno suscitando notevole interesse i trasduttori piezoelettrici sollecitati da vibrazioni naturali, come quelle indotte dalla pioggia o dal vento. La presente tesi ha lo scopo di fornire un contributo alla produzione di energia pulita ed 'economica', utilizzando piccoli dispositivi piezoelettrici: sollecitando gli harvester piezoelettrici con opportune vibrazioni naturali è possibile alimentare dispositivi a bassa potenza. L'obiettivo principale della tesi è quello di capire come possa reagire un cantilever beam piezoelettrico sotto l'effetto di opportune vibrazioni, quali, ad esempio, quelle indotte dal passaggio di un fluido (aria o acqua), o da un movimento meccanico quale quello provocato dal passaggio di un vagone ferroviario sulle rotaie. L'analisi vibrazionale è stata effettuata utilizzando sia un opportuno apparato sperimentale che un ambiente di simulazione, al fine di validare le simulazioni con i dati sperimentali. Tale validazione conferisce affidabilità al processo di simulazione che può quindi essere esteso per analizzare situazioni non facilmente riproducibili in laboratorio. Inoltre, l'ambiente di simulazione offre la possibilità di ottimizzare i vari elementi costitutivi (forme, spessori e materiali costituenti) dei cantilever beam, permettendo così la progettazione di un cantilever beam piezoelettrico 'ottimale', specifico per la situazione considerata. Il potenziale elettrico sviluppato da tali dispositivi può essere conservato e riutilizzato, secondo i principi dell'EH. Inoltre, i dispositivi così progettati possono essere utilizzati anche come sensori nel campo della diagnostica non distruttiva. La modellizzazione, la simulazione, l'ottimizzazione e la validazione sperimentale del comportamento dei cantilever beam piezoelettrici sono state realizzate in svariati casi di studio, la cui descrizione propone il dispositivo utilizzato in situazioni diverse, aventi un crescente grado di difficoltà. Per ogni caso di studio è stata descritto un adeguato modello matematico. Sono state fornite anche opportune informazioni in merito alla struttura delle matrici costitutive di ogni materiale piezoelettrico considerato. Tutte le simulazioni presentate nella tesi sono stati realizzate utilizzando COMSOL Multiphysics, un software che utilizza il metodo agli elementi finiti (FEM) per risolvere modelli matematici. Il FEM è uno dei metodi numerici più utilizzati per calcolare soluzioni approssimate di problemi descritti matematicamente da equazioni alle derivate parziali (PDE). E' spesso utilizzato per ‘semplificare’ problemi reali che coinvolgono interazioni di non semplici fenomeni fisici, realizzate utilizzando oggetti aventi geometrie e condizioni al contorno di non semplice analisi. La presente tesi si conclude con lo studio di fattibilità di un'applicazione reale, in cui un sistema autoalimentato, basato su un dispositivo piezoelettrico, può continuamente monitorare lo stato di salute della boccola di una carrozza ferroviaria, e quindi contribuire alla sicurezza dei passeggeri ferroviari.
Environmental pollution is one of the biggest world problems nowadays and is closely connected to other important problems. The percentage of employment of polluting sources of energy is still high compared with that referred to clean ones. In recent years, several studies into alternative energies have been developed. The aim of renewable energies fits well with the philosophy of a science that studies the conversion of energy wasted in the environment into different and more useful forms: this science is called Energy Harvesting (EH). It is possible to harvest energy capturing it from environmental sources such as solar, thermal, wind-kinetic energy and natural vibrations. The energy produced by some of these alternative sources of energy, such as wind and vibrational energy, is converted into electrical energy through non-polluting processes and are used directly by energy harvesters devices that work as generators under the effect of vibrations. The conversion process of environmental energy into electrical power often involves smart materials such as piezoelectric materials, which develop electrical charge when subject to mechanical stress (direct piezoelectric effect): this charge can be stored by means of an electrical circuit. A wide range of devices made of piezoelectric materials has been developed in the EH field, for various large and small-scale applications. Great interest has been directed to piezoelectric transducers stressed by natural vibrations, such as those induced by rain or wind. This dissertation is aimed at contributing to the production of clean and inexpensive energy, using small piezoelectric devices stressed by natural vibrations and useful to provide energy to low-power devices. The objective is to understand how a piezoelectric cantilever beam reacts under the effect of vibrations that could be induced by a flowing fluid, such as air or water, or by mechanical movement, such as that of a train on the rails. The vibrational analysis was carried out both using experimental apparatus and in a simulation environment, in order to validate the simulations with experimental data. This validation lends reliability to the simulation process that can be extended to analyse situations not easily testable in the laboratory. Furthermore, the simulation environment offers the opportunity of looking for the optimization of several constitutive elements of cantilever beams, such as their shapes, thicknesses and materials they are made of, so allowing the design of an ‘optimal’ cantilever beam, specific for the situation considered. The electrical potential developed by such devices can be stored and reused following the principles of EH. Moreover, these so designed devices can be used as sensors in the field of Non-destructive testing. The modelling, simulation, optimization and experimental validation of the behaviour of the piezoelectric cantilever beam are carried out with some different case studies, describing the harvester device in situations with an increasing degree of difficulty. An appropriate mathematical model was described for each case study. Useful information is provided about the structure of the constitutive matrices of each piezoelectric material considered. All the simulations presented in the dissertation were realised using Comsol Multiphysics, software that uses the Finite Element Method (FEM) to solve mathematical models. The FEM is one of the most popular numerical methods used to calculate approximated solutions for problems described mathematically by Partial Differential Equations (PDEs). It is often used to ‘simplify’ real-world problems that involve complicated physics, geometry and boundary conditions. Finally, this dissertation presents a feasibility study for a real application, in which a self-powered system based on a piezoelectric device can constantly monitor the state of health of the axle-box of a railway carriage and hence contribute to the safety of rail passengers.