Дисертації з теми "Experimental modal analysi"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Experimental modal analysi.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Experimental modal analysi".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
ZANOTTI, FRAGONARA LUCA. "Dynamic models for ancient heritage structures." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2502121.
Повний текст джерелаАнотація:
Risks to cultural heritage and the related losses should be mitigated before disasters such as earthquakes happen. Risks can be addressed by various means, from raising the cultural attention of authorities to documenting the artistic or historical value of an object. The main contribution of structural engineering to cultural heritage concerns the regular maintenance and monitoring for risk reduction.
Risk mitigation of historical buildings, as a part of the more general concept of conservation, involves different disciplines. Teams need to be multidisciplinary and information deriving from historical, metric, stylistic, structural, seismic, geotechnical and physical analysis may contribute to the achievement of an overall comprehension of cultural assets.
The synergic action of the characterization and monitoring techniques are essential factors to understand, on one hand the mechanisms and the consequences of degradation and, on the other hand, to provide reliable and well-grounded guidelines for the definition of technical interventions to prevent/ to stop the degradation phenomena, to restore the functionality and the use of the historical building/ artifact, or to predict, mitigate and even control the response to accidental events, including strong motions. In this field, an important role is played not only by the analytical aspects, but also by the development and validation of innovative materials and systems for conservation.
International deontological guidelines on conservation of cultural heritage define the structural rehabilitation of heritage structures as the cure of a sick person, hence “the heritage structures require anamnesis, diagnosis, therapy and controls, corresponding respectively to the searches for significant data and information, individuation of the causes of damage and decay, choice of the remedial measures and control of the efficiency of the interventions”. Moreover, the same codes state that: “the best therapy is preventive maintenance”, which can only be achieved via monitoring of the structure.
In this thesis work a few topical issues of the structural modelling, monitoring and assessment of historic masonry buildings were addressed, with particular emphasis on the dynamic testing and identification. The possible connections with other disciplines are analysed and discussed throughout the text. In this framework, the outline of the thesis includes an introductive first chapter in which the context established by the most recent codes and guidelines concerning the architectural heritage conservation is duly reviewed and analysed. The importance of attaining a knowledge of the structure is also discussed.
The second chapter sets up the scene, in which it introduces the principal issues of seismic risk and safety assessment of architectural heritage. Firstly, a brief overview is given of the seismic risk and of geological and geotechnical aspects as related to ancient heritage. Successively, the viability of performance-based approaches, for application to the seismic assessment of architectural heritage, is discussed also in the light of a few recent proposals. In this context, the fundamentals of structural health monitoring are also reported.
Chapter 3 is intended to stress the importance of modal testing as an effective tool for ancient structures characterisation, so it starts with a state-of-the-art on linear system identification methods with emphasis on output-only techniques. In particular, time domain and joint time-frequency domain identification techniques are introduced and deeply analysed. Model updating is then addressed and its connection with operational modal analysis is underlined. Finally, a few noteworthy examples of linear identification and model updating of architectural heritage structures are reported.
Chapter 4 is about the dynamic and seismic behaviour of domes. The coverage focuses on three ideal benchmarks on reconciling geometric survey with dynamic monitoring. The analyses concerned structures with oval shape domes, such as the Sanctuary of Vicoforte, S. Caterina in Casale Monferrato and S. Agostino in L’Aquila. The final products are virtual models which were enabled to predict the linear dynamic response under earthquake excitation.
Chapter 5 inspects modelling strategies suited for masonry under intense seismic excitations. The state-of-the-art covers both models for equivalent static analysis and models which operates in dynamics. A model allowing for stiffness degradation, pinching and hysteresis is then proposed, whose formulation admits extensions to multiple degree of freedom systems. The proposal originates from the well-known Bouc-Wen model.
Chapter 6 deals with non-linear identification methods. In perspective, also non-linear identification is expected to become a powerful tool in the context of structural and seismic reliability assessment, especially in the light of the increasing levels of knowledge and prediction capabilities which recent standards strive for. Unfortunately, non-linear identification is to date a specialized and challenging matter, and it has been seldom applied to full-scale structures. In this chapter, special emphasis is given to on-line implementations, with several numerical examples showing the potential of non-linear as well as hysteretic system identification.
The last chapter presents an experimental application of non-linear identification. A scaled model of a two-span masonry arch bridge has been artificially damaged and monitored at each damage step. A non-linear identification has been performed from shaker tests data. Results of the experimental campaign will be used to corroborate a non-linear and hysteretic model of the bridge endowed with prediction capabilities.
2
Potgieter, Brendon Ryan. "Experimental modal analysis and model validation of antenna structures." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5423.
Повний текст джерелаАнотація:
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Numerical design optimisation is a powerful tool that can be used by engi- neers during any stage of the design process. Structural design optimisation is a specialised usage of numerical design optimisation that has been adapted to cater speci cally for structural design problems. A speci c application of structural design optimisation that will be discussed in the following report is experimental data matching. Data obtained from tests on a physical structure will be matched with data from a numerical model of that same structure. The data of interest will be the dynamic characteristics of an antenna structure, focusing on the mode shapes and modal frequencies. The structure used was a scaled, simpli ed model of the Karoo Array Telescope-7 (KAT-7) antenna structure. Experimental data matching is traditionally a di cult and time-consuming task. This report illustrates how optimisation can assist an engineer in the process of correlating a nite element model with vibration test data.
AFRIKAANSE OPSOMMING: Numeriese ontwerp-optimisering is 'n kragtige ingenieurshulpmiddel wat ty- dens enige stadium in die ontwerpsproses ingespan kan word. Strukturele ontwerp-optimisering is 'n gespesialiseerde gebruik van numeriese ontwerp- optimisering wat aangepas is om spesi ek van diens te wees by die oplos van strukturele ontwerpsprobleme. 'n Spesi eke toepassing van strukturele ontwerp-optimisering wat in hierdie verslag bespreek sal word, is eksperi- mentele datakorrelasie. Data afkomstig van toetse op 'n siese struktuur sal gekorreleer word met data afkomstig van 'n numeriese model van die selfde struktuur. Die data van belang is die dinamiese eienskappe van 'n anten- nastruktuur, spesi ek die modusvorme en modale frekwensies. Die betrokke struktuur wat gebruik is, is 'n vereenvoudigde skaalmodel van die Karoo Array Telescope-7 (KAT-7) antennastruktuur. Eksperimentele datakorrelasie is, tradisioneel gesproke, 'n moeilike en tydro- wende taak. Hierdie verslag sal illustreer op watter wyse optimisering 'n inge- nieur van hulp kan wees in die proses om 'n eindige elementmodel met vibrasietoetsdata te korreleer.
3
Aluri, Srinivas. "Updating low-profile FRP deck FE model using experimental modal analysis." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4656.
Повний текст джерелаАнотація:
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains vi, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 60-61).
4
You, You, and Daxin Chen. "Modal Analysis on a MIMO System : For an asphalt roller CC1200." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-10998.
Повний текст джерелаАнотація:
Impact hammer is the current modal testing way in Dynapac testing department. Due to highly damped characteristic of big construction machines, there are a few weaknesses for modal testing when using hammer, such as short response time, limited frequency resolution, poor quality of frequency response functions. Therefore, a more advanced excitation equipment is needed to improve the measurement quality. The object for this study is to compare two different measuring methods. The thesis will show a comparison between the hammer testing and the shaker MIMO testing compared with analytical model in a highly damped system. It will also give a reference for further highly damped modal analysis and budgetary assessment to decide the budget expenditure. Result from shaker testing shows a little better correlation than hammer testing compared with FEM model. While the correlation between FEM model and measurement is bad due to many reasons, such as many local modes that can not excited, lack of excitation points, unexpected noise and error from the measurement. While considering the compared results obtained from this machine for now, a simpler structure experiment is suggested to be carried on in the future. Shorter length of stinger can be used to enable higher amplitude of force to excite the property on this machine.
5
Mejri, Seifeddine. "Identification et modélisation du comportement dynamique des robots d'usinage." Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22688/document.
Повний текст джерелаАнотація:
La robotisation des procédés d’usinage suscite l’intérêt des industriels en raison du grand espace de travail et le faible coût des robots par rapport aux machines-outils conventionnelles et la possibilité d’usiner des pièces de formes complexes. Cependant, la faible rigidité de la structure robotique favorise le déclenchement de phénomènes dynamiques liés à l’usinage sollicitant le robot en bout de l’outil qui dégradent la qualité de surface de la pièce usinée. L’objectif de ces travaux de thèse est de caractériser le comportement dynamique des robots en usinage. Ces travaux ont suivi une démarche en trois étapes : La modélisation d’un premier modèle considéré de référence où le robot est au repos. Ensuite l’identification du comportement dynamique du robot en service. Enfin, l’exploitation des modèles dynamiques du robot en vue de prédire la stabilité de coupe. L’originalité de ces travaux porte sur le développement des méthodes d’identification modale opérationnelles. Elles permettent d’intégrer les conditions réelles d’usinage et d’élaborer des modèles plus précis que le premier modèle de connaissance sans être biaisés par l’effet des harmoniques de rotation de l’outil. Enfin, des préconisations sur le choix de configurations du robot et sur la direction des forces d’excitation sont proposées pour assurer la stabilité de la coupe lors de l’usinage robotiséMachining robots have major advantages over cartesian machine tools because of their flexibility, their ability to reach inaccessible areas on a complex part, and their important workspace. However, their lack of rigidity and precision is still a limit for precision tasks. The stresses generated by the cutting forces and inertia are important and cause static and dynamic deformations of the structure which result in problems of workpiece surface. The aim of the thesis work is to characterize the dynamic behavior of robots during machining operation. This work followed a three-step approach : Modeling a first model considered as a reference where the robot is at rest. Then the identification of the dynamic behavior in service. Finally, the prediction of the cutting stability using the robot dynamic model. The originality of this work is the development of new operational modal identification methods. They integrate the machining conditions and result into a more accurate model than the first model of reference without being biased by harmonics. Finally, guidlines of robot’s configurations and excitation forces’ direction are proposed to ensure the robotic machining stability
6
Venkataraman, Siddharth. "Analytic, Simulation and Experimental Analysis of Fluid-Pipe Systems." Thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-249996.
Повний текст джерелаАнотація:
Inviscid fluid inside thin pipe system is first analytically solved for eigenfrequencies and eigenmodes using Modal Interaction Model method with fluid-structure interaction condition at boundary. Shear-diaphragm boundary condition is used for comparing and validating Analytic results with Simulation using COMSOL Multiphysics. Effect of viscosity is also compared using Newtonian fluid model. Experiment is performed using simple pipe geometry and fluid to measure transfer accelerance which is post-processed to extract cirumferential modes up to order 4; this is used to compare and validate Experiemental results with Simulation. Good correlation is obtained between Analytic, Experiment and Simulation results with n=0 breathing modes requiring modification of governing equations to incorporate compressibility effects due to changing pipe cross-section area.En analytisk lösning för egenfrekvenser och egenmoder för en icke-viskös fluid inuti ett tunt rörsystem är först framtagen med användning av en modbaserad modell för interaktion mellan fluid och struktur som randvillkor. Idealiserad randvillkor används för att jämföra och validera analytiska resultat med simulationer i COMSOL Multiphysics. Effekten av viskositet jämförs också med hjälp av en Newtonsk fluidmodell. Experiment genomförs med simpel rörgeometri samt fluid för att mäta acceleransen som är analyserad för till att få ut mo-der i omkretsled upp till fjärde ordningen; detta i sin tur används för att jämföra och validera de experimentella resultaten med simulering-ar. Det erhålls bra korrelation mellan de analytiska-, simulerade- samt experimentella resultaten. Undantaget för n=0 grundmoder då krävs modifikation av differentialekvationerna till att inkorporera kompressibilitetseffekter
7
Burkett, Jason Lee. "BENCHMARK STUDIES FOR STRUCTURAL HEALTH MONITORING USING ANALYTICAL AND EXPERIMENTAL MODELS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2660.
Повний текст джерелаАнотація:
The latest bridge inventory report for the United States indicates that 25% of the highway bridges are structurally deficient or functionally obsolete. With such a large number of bridges in this condition, safety and serviceability concerns become increasingly relevant along with the associated increase in user costs and delays. Biennial inspections have proven subjective and need to be coupled with standardized non-destructive testing methods to accurately assess a bridge's condition for decision making purposes. Structural health monitoring is typically used to track and evaluate performance, symptoms of operational incidents, anomalies due to deterioration and damage during regular operation as well as after an extreme event. Dynamic testing and analysis are concepts widely used for health monitoring of existing structures. Successful health monitoring applications on real structures can be achieved by integrating experimental, analytical and information technologies on real life, operating structures. Real-life investigations must be backed up by laboratory benchmark studies. In addition, laboratory benchmark studies are critical for validating theory, concepts, and new technologies as well as creating a collaborative environment between different researchers. To implement structural health monitoring methods and technologies, a physical bridge model was developed in the UCF structures laboratory as part of this thesis research. In this study, the development and testing of the bridge model are discussed after a literature review of physical models. Different aspects of model development, with respect to the physical bridge model are outlined in terms of design considerations, instrumentation, finite element modeling, and simulating damage scenarios. Examples of promising damage detection methods were evaluated for common damage scenarios simulated on the numerical and physical models. These promising damage indices were applied and directly compared for the same experimental and numerical tests. To assess the simulated damage, indices such as modal flexibility and curvature were applied using mechanics and structural dynamics theory. Damage indices based on modal flexibility were observed to be promising as one of the primary indicators of damage that can be monitored over the service life of a structure. Finally, this thesis study will serve an international effort that has been initiated to explore bridge health monitoring methodologies under the auspices of International Association for Bridge Maintenance and Safety (IABMAS). The data generated in this thesis research will be made available to researchers as well as practitioners in the broad field of structural health monitoring through several national and international societies, associations and committees such as American Society of Civil Engineers (ASCE) Dynamics Committee, and the newly formed ASCE Structural Health Monitoring and Control Committee.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
8
笹岡, 竜., Ryu SASAOKA, 秀幸 畔上, Hideyuki AZEGAMI, 紀明 川上 та Noriaki KAWAKAMI. "脊柱力学模型による特発性側彎症の成因解明". 日本機械学会, 2003. http://hdl.handle.net/2237/12189.
Повний текст джерела
9
Altunel, Fatih. "Model Updating Of A Helicopter Structure Using A Newly Developed Correlation Improvement Technique." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611300/index.pdf.
Повний текст джерелаАнотація:
Numerical model usage has substantially increased in many industries. It is the aerospace industry that numerical models play possibly the most important role for development of optimum design. However, numerical models need experimental verification. This experimental verification is used not only for validation, but also updating numerical model parameters. Verified and updated models are used to analyze a vast amount of cases that structure is anticipated to face in real life.
In this thesis, structural finite element model updating of a utility helicopter fuselage was performed as a case study. Initially, experimental modal analyses were performed using modal shakers. Modal analysis of test results was carried out using LMS Test.lab software. At the same time, finite element analysis of the helicopter fuselage was performed by MSC.Patran &Nastran software. v Initial updating was processed first for the whole helicopter fuselage then, tail of the helicopter was tried to be updated. Furthermore, a new method was proposed for the optimum node removal location for getting better Modal Assurance Criterion (MAC) matrix. This routine was tried on the helicopter case study and it showed better performance than the Coordinate Modal Assurance Criterion (coMAC) that is often used in such analyses.
10
Marudachalam, Kannan. "An attempt to quantify errors in the experimental modal analysis process." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08142009-040508/.
Повний текст джерела
11
Braunwart, Paul R. "Experimental and Analytical Examination of Golf Club Dynamics." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31506.
Повний текст джерелаАнотація:
To provide the average golfer with more consistent results, manufacturers have
continued to improve the available equipment. This has led to larger club-heads, with
larger ?sweet spots?, different shaft thickness for different swing styles, and the use of
advanced materials, such as graphite and titanium, for the construction.
The development of improved equipment, which utilizes advanced materials, has
spurred the need for advanced scientific analysis using a variety of techniques. Among
the most prevalent of these methods are finite element analysis and experimental modal
analysis, and use of these techniques in examining a golf club is the focus of this
research.
The primary goals of this work are the development and correlation of an
appropriate finite element model, the characterization of the hands-free boundary
condition and the examination of the club golf dynamic response. To accomplish these
objectives, the physical parameters of the golf club are determined to develop the finite
element model. The analysis of natural frequencies and mode shapes correlate well with
the results extracted from experimental modal analysis for the free-free and clamped-free
boundary conditions. With the correlation established, a third boundary condition, hands-free,
is tested experimentally to ascertain the effects of the golfer?s grip on the boundary
conditions. With the FEA model confirmed, a nonlinear dynamic response of the club
during the down-swing is investigated using the nonlinear solver in Algor, and the club-head
position relative to the shaft is predicted.Master of Science
12
Azoury, Chadi. "Analyse dynamique d’un vilebrequin nouvel élément fini filaire." Toulouse 3, 2007. http://www.theses.fr/2007TOU30023.
Повний текст джерелаАнотація:
Ce travail de thèse vise à analyser le comportement dynamique d'un vilebrequin afin d'aboutir à un modèle élément fini simple pouvant simuler ses comportements. Un modèle E. F utilisant un maillage volumique d'éléments tétraédriques est réalisé. Ce modèle fournit les valeurs des modes et fréquences propres de vibration du vilebrequin. Ensuite les résultats du modèle élément fini sont validés par la méthode d'analyse expérimentale. Le but de cette thèse est de remplacer le maillage volumique par un maillage filaire. Plusieurs nouveaux éléments de poutre ont été proposés et étudiés sur une structure de test en portique en analyse statique et dynamique. Finalement les résultats numériques obtenus montrent que l'élément fini filaire peut substituer aux éléments finis volumiquesThis work of research consists of analyzing the dynamical behavior of a crankshaft in order to get a simple linear finite element that can simulate its behaviors. A finite element model using tetrahedral volumetric elements is performed. This model produces the values of modes and frequencies of vibration of the crankshaft. Then the results of the finite element model are validated using the experimental modal analysis. The objective of this thesis is to replace the volumetric meshing with a simple linear meshing. Many new beam elements are proposed and studied on a test frame structure statically and dynamically. Finally the obtained numerical results show that the linear finite element can substitute volumetric finite elements
13
Matsuyama, Yukihiro, Ryu Sasaoka, Hideyuki Azegami, Shunji Murachi, Junzoh Kitoh, Yoshito Ishida, Noriaki Kawakami, and Mitsunori Makino. "Investigation of Buckling Phenomenon Induced by Growth of Vertebral Bodies Using a Mechanical Spine Model." 日本機械学会, 2003. http://hdl.handle.net/2237/7283.
Повний текст джерела
14
Rossetto, Gustavo Dalben. "Contribuição a teoria e pratica da analise modal acustica experimental." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265319.
Повний текст джерелаАнотація:
Orientador: Jose Roberto de França ArrudaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-07-31T18:15:00Z (GMT). No. of bitstreams: 1 Rossetto_GustavoDalben_M.pdf: 4484828 bytes, checksum: b149e9723524115d4c39c2ea81d0c5bc (MD5) Previous issue date: 2001
Resumo: Neste trabalho uma geometria simples (cavidade retangular) é usada para o estudo da metodologia aplicada na análise modal acústica. Modelos analítico e numérico são desenvolvidos para a comparação com os resultados experimentais. Três tipos de dispositivos de excitação do sistema acústico foram construídos. Um baseado num pistão conectado a um shaker, e outros dois usando um alto-falante do tipo driver. O primeiro atuador usando o driver é similar ao modelo desenvolvido por um projeto europeu, onde um tubo flexível com uma terminação instrumentada com um microfone é usado para a condução da excitação acústica. O segundo atuador baseado no uso do driver também usa um tubo flexível, mas este é instrumentado com dois microfones em sua terminação. O comportamento destes dois últimos atuadores em termos de aceleração de volume (essencial para a análise modal acústica experimental) e de potência ativa (necessária para Análise Estatística de Energia Experimental) sendo injetados no meio são investigados. A análise modal experimental da cavidade retangular é realizada e um método que utiliza a transformada de Fourier espacial multidimensional do campo de pressão medido é proposto para-a construção do campo de deslocamento de partícula para a visualização do modo acústico
Abstract: In the present work, a simple geometry (rectangular shallow cavity) is used to investigate the acoustic modal analysis methodology. Analytical and numerical models are developed for the comparison with the experimental results. Three types of excitation devices were constructed. One based on a shaker-driven piston and the other two using a driver loudspeaker. The first actuator based on a driver loudspeaker is similar to a model developed by an EEC project, where a flexible tube with a socket, instrumented with one microphone, at its termination is used to conduct the sound excitation. The second actuator based on a driver loudspeaker alse uses a flexible tube, but it is instrumented with two microphones in its socket instead of one. The behavior of these last two actuators in terms of volume acceleration (essential in the acoustic modal analysis) and active power (necessary for the Experimental Statistical Energy Analysis) being injected into the medium are investigated. The experimental modal analysis of the rectangular cavity is performed and a method using multi-dimensional spatial Fourier transforms of the array of pressure measurements is proposed for the construction of the partic1e displacement field for acoustic mode shape visualization
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
15
Kaya, Huseyin. "Experimental Modal Analysis Of A Steel Grid Frame." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12604710/index.pdf.
Повний текст джерелаАнотація:
In this study, experimental modal analysis was studied. Experimental modal analysis includes modal testing, modal parameter estimation and calibration. For this purpose a 4 span skewed steel frame was constructed in Structural Mechanics Laboratory of Civil Engineering Department of METU. The model was transported to Vibration and Acoustic Laboratory of Mechanical Engineering Department of METU. The tests were conducted by cooperation with Vibration and Acoustics Laboratory. Due to lack of experimental modal analysis software in Structural Mechanics Laboratory, modal parameter estimation and finite element updating softwares were written in Matlab platform. The written softwares were executed on the data obtained from modal testing.
15 reasonable modes are extracted from the FRFs that are obtained from modal testing. 59.23 percent consistency is found for the nominal modal comparison. At the end of calibration process 76.14 percent consistency is achieved between the experimental results and analytical results.
16
Uwajambo, Pacifique, and Nisha Thakur. "Numerical and Experimental Modal Analysis of CNC Machine." Thesis, Blekinge Tekniska Högskola, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21652.
Повний текст джерелаАнотація:
Numerical and Experimental Modal Analysis of RAW CNC milling machine was performed in this project. The RAW CNC machine's lightweight, easy assembling, and operation features make it a good choice for hobbyists and professionals. As the machine is subjected to vibration during the milling process, the work is intended to study the machine's dynamic behaviour through Finite Element Method (FEM) in the first stage, followed by validating it with Experimental Modal Analysis (EMA). The simulation and experimentation are focused on X and Y-axis. In the first stage, the inventor model of the machine was created and then simulated in COMSOL Multi-physics and Nastran by extracting mode shapes and frequencies. In the second stage, experimentation was carried out in the laboratory for both axes separately. Through the EMA, the four resonance frequencies and their mode shape were determined and compared with the simulated FEM modal. The result showed the first lowest frequency for the x-axis in experimental modal had a bit more deviations than finite element simulation, which raised the need for estimation of possible causes of error. However, the deviation range between experimental and FEM simulation is below 16.68%, which was acceptable for all other modes. From the analysis, the Y-axis beams were the weakest part of the machine. Finally, methods for improving the model was recommended, which could be applied in future models to increase the stiffness of the machine.
17
Tufano, Anna Rita. "Vibroacoustic coupling phenomena on heavy vehicles.Medium frequency experimental analysis and numerical applications for design specifications." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC052.
Повний текст джерелаАнотація:
La prestation vibroacoustique est une question primordiale pour les constructeurs de véhicules, qui sont contraints par des lois ainsi que par des besoins commerciales: d'une part, un grand nombre de normes existe, visant à régler les niveaux vibratoires et acoustiques que les occupants d'un véhicule peuvent supporter, d'autre part le constructeur est intéressé à garantir un haut degré de confort pour que son produit soit compétitif. L'industrie du poids lourds comporte des spécificités par rapport à d'autres secteurs industriels, et surtout par rapport au marché des véhicules légers: non seulement l'architecture d'un véhicule industriel est unique, mais en plus ce qui caractérise les poids lourds par rapport à d'autres véhicules terrestres est la grande diversité des configurations disponibles. Une bonne connaissance des mécanismes de transmission des vibrations et du bruit, ainsi que du bilan de leurs sources, permette de fixer des règles de conception plus rigoureuses pour les composants. Par ailleurs, la connaissance des influences des paramètres architecturaux d'un camion sur les prestations vibroacoustiques donne une meilleure clé d'interprétation pour prédire les caractéristiques qu'un composant du véhicule doit avoir. Actuellement ces vérifications sont largement basées sur des essais, soit subjectifs (estimations par des techniciens experts) soit objectifs (acquisitions par microphones et accéléromètres). Cette pratique est très coûteuse car, pour prendre en compte la diversité des camions, il faut tester un grand nombre de véhicules. Pour franchir ces limitations, le prototypage virtuel - au lieu des essais physiques - doit être renforcé. Les méthodologies numériques sont déjà utilisées au sein du Groupe Volvo, mais les outils disponibles sont considérés en partie inappropriés pour les besoins de calcul des prestations NVH. Les activités de cette thèse ont été réalisées dans le cadre du service Noise and Driveline Vibration, qui est responsable de l'estimation du confort acoustique perçu par les occupants du camion, dans toutes ces conditions d'utilisation. Les travaux de thèse sont concentrés sur le comportement du châssis comme composant principale; le châssis est la principale voie de transfert des vibrations depuis le moteur vers la cabine. En outre, une attention particulière sera donnée à l'effet des accessoires sur le comportement dynamique du châssis, bien que peu d'intérêt sera porté sur la signature vibratoire des accessoires mêmesThe vibroacoustic performance is a matter of primary concern for modern vehicle manufacturers, that are constrained by health and safety legislation as well as by commercial needs: on the one hand, a number of norms exists regulating the level of vibration and noise that vehicle occupants can tolerate, but on the other hand a manufacturer is also interested in guaranteeing a high level of comfort in order to keep products competitive. The commercial vehicle industry presents some peculiarity with respect to other vehicle manufacturing businesses, and especially to the more known car industry: not only the architecture of a commercial vehicle is a class of its own, but what differentiates the most trucks from other ground vehicles are the configuration diversity and customization. A deep knowledge of the vibration and noise transmission mechanisms in trucks as well as source breakdown allows defining more rigorous and strict component specifications. Furthermore, the comprehension of the sensitivity of truck architecture parameters on vibroacoustic features provides even deeper means to assess the needed properties for a component to be installed on a vehicle. At present the verification is largely based on tests, both subjective (assessment by experimented test engineers) and objective (microphone and accelerometer acquisitions). This practice is extremely expensive, since, in order to take into account the large diversity of trucks, a large number of vehicles has to be tested. To overcome this limit, virtual testing - as opposed to physical testing - should be strengthened. Numerical methods are already largely used in the Volvo Group, but the available tools are considered partly unfit to the NVH demands and inappropriate with respect to their specific needs. The activities of the current thesis have been developed in the framework of the Interior Noise and Driveline Vibration group, which is responsible for the estimation of the acoustic comfort perceived by driver and passengers in all driving conditions and vehicle uses. This thesis will focus on the behaviour of the chassis as a primary component. The chassis is the main transfer path for engine-induced vibrations transmitted to the cabin. Besides, a peculiar attention will be given to the effect the chassis equipment components have on the chassis dynamics, even though limited interest will be put on the investigation of the dynamic signature of the equipment itself
18
Kleinknecht, Mathias, and Álvarez Alfredo Fernández. "Wind turbine blade modeling - setting out from experimental data." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-26054.
Повний текст джерелаАнотація:
Complex systems can be divided into simpler substructures. Determining the properties of each subcomponent by experimental procedures is practical and can serve to verify or calibrate finite element models. In this work, an existing model of a wind turbine blade was improved by use of experimental data. Such a blade is a subpart of a complete wind turbine. For calibration purpose, several material tests were made in order to determine the stiffness and mass properties. Later on, vibration tests of the blades were conducted and compared with simulation results of the improved model. Geometry variability within sets of blades was also studied. The blade twist angles and the center of gravity positions were found to vary moderately, which accounts for differences in blades’ dynamic behavior. Correlations between experimental data and analytical model results were very high for the first eight modeshapes. That is, according to the Model Assurance Criterion the calibrated model achieves a high-quality representation of reality. However, torsional modes in the computer model occur at a higher frequency than the experimental ones. Substructuring of the turbine allows the blades to be modeled and validated independently of the other substructures and can later be incorporated into a complete model of the turbine.
19
Owolabi, Gbadebo Moses. "Crack identification procedures in beams using experimental modal analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/MQ62411.pdf.
Повний текст джерела
20
Maamar, Asia. "Identification modale opérationnelle des robots d'usinage en service." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC013/document.
Повний текст джерелаАнотація:
L’identification des paramètres modaux des machines-outils et des robots d’usinage, en service, constitue un levier d’optimisation des performances de coupe. En effet, la connaissance en continue du comportement dynamique d’une machine permet une prédiction fine des conditions de stabilité, bases d’un pilotage intelligent des paramètres du procédé. Cependant, la présence de fortes excitations harmoniques, dues à la rotation de la broche et de l’outil coupant, rend les techniques classiques d’Analyse Modale Opérationnelle (AMO) inapplicables. Le premier objectif de cette thèse consiste à déterminer une méthode d’AMO adéquate pour une application en présence des harmoniques. Une étude comparative des méthodes existantes est conduite, à savoir : la méthode de décomposition dans le domaine fréquentiel (EFDD), la méthode d’identification dans le sous-espace stochastique (SSI), la méthode PolyMAX et la méthode basée sur la fonction de transmissibilité (TFB). La méthode TFB est choisie afin de réaliser une identification modale opérationnelle des robots d’usinage. Cette technique est tout d’abord investiguée sur une machine-outil cartésienne. Cette étape est justifiée par le fait qu’une machine-outil est une structure plus rigide qui présente moins de variations des propriétés dynamiques par rapport à un robot d’usinage. Les résultats montrent la pertinence de la méthode TFB pour identifier les paramètres modaux de la machine-outil en usinage, même en présence des composantes harmoniques fortement dominantes. Ensuite, l’identification modale opérationnelle du robot d’usinage ABB IRB 6660, qui présente une structure moins rigide par rapport à une machine-outil, est menée sur une trajectoire d’usinage. Les résultats obtenus permettent d’établir une base modale du robot montrant l’évolution de son comportement modal en service. L’originalité des travaux présentés réside dans le développement d’une procédure robuste d’identification modale opérationnelle qui permet de suivre l’évolution du comportement modal du robot en cours d’usinage dans son espace de travailThe identification of the modal parameters of machining robots in service has a significant adverse influence on machining stability, which will, therefore, decrease the quality of the workpiece and reduce the tool life. However, in presence of strong harmonic excitation, the application of Operational Modal Analysis (OMA) is not straightforward. Firstly, the issue of choosing the most appropiate OMA method for an application in presence of harmonic components, is handled. For a comparison purpose, the modified Enhanced Frequency Domain Decomposition (EFDD) method, the Stochastic Subspace Identification (SSI) method, the PolyMAX method and the Transmissibility Function Based (TFB) method are investigated. The obtained results lead to the adoption of the Transmissibility Function Based (TFB) method for an OMA of machining robots. For an accurate modal identification procedure, the OMA of a machine tool is, initially, conducted. It is a preparation step in order to verify the performance of the chosen method under machining conditions as well as a machine tool is a rigid structure, thus, it has less variation in its dynamic behavior compared to a machining robot. Results demonstrate the efficiency of the TFB method to identify the machine tool modal parameters even in the presence of preponderant harmonic components. Finally, the OMA of the machining robot ABB IRB 6660, which has a flexible structure compared to a machine tool, is carried out for a machining trajectory. The obtained results allow the identification of a modal basis of the machining robot illustrating the evolution of its modal behavior, in service. The main novelty of this thesis lies in the development of a robust procedure for an operational modal identification of machining robots, in service, which makes it possible to continuously follow the variations in the modal parameters of machining robots
21
Baver, Brett C. "Property Identification of Viscoelastic Coatings Through Non-contact Experimental Modal Analysis." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1459438426.
Повний текст джерела
22
Afolayan, Fatai Olayemi. "Modal Analysis of Simple Structures: Comparison Between Analytical, Numerical, and Experimental Methods." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22486/.
Повний текст джерелаАнотація:
Better understanding of the dynamic behavior of structures is as important as using reliable methods to determine the dynamic behaviour. This study started by describing the importance of dynamic analysis in structures, and further exploring what is meant by “Modal Analysis” and the different methods used in obtaining the Modal properties of a simple structure. First, using “Mathematical Methods”, a “Simple Beam Element” was analyzed with Analytical analysis and Numerical modelling. In the Numerical model, the beam was modelled twice with different boundary conditions. The results of the mathematical methods were compared. Second, using “Experimental Methods”, the same simple beam element was analyzed using “Impact Testing” methods of experimental modal analysis. The results gotten with experimental methods were compared with both the analytical and numerical methods, and the comparison between these results shows that the errors are within reasonable range, and it will help future engineers to better design and develop engineering components.
23
Martin, Guillaume. "Méthode de corrélation calcul/essai pour l'analyse du crissement." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0012/document.
Повний текст джерелаАнотація:
Le crissement de frein est une nuisance sonore récurrente dans l’automobile qui, bien qu’il n’existe pas de solution robuste lors de la conception, se traduit souvent par des pénalités économiques envers les équipementiers. La simulation numérique et les caractérisations expérimentales sont les deux voies classiques pour analyser les phénomènes crissants. La simulation permet une analyse fine des comportements vibratoires et l’évaluation de l’impact de modifications de conception, mais les modèles sont imparfaits et leur domaine de validité doit être établi. La mesure garantit que tous les paramètres sont pris en compte, mais elle est souvent spatialement pauvre et peu adaptée à la prédiction de modifications. Dans ce contexte, les objectifs de la thèse sont de faire un bilan des méthodes d’exploitation des essais, de fournir des outils permettant une interaction facilitée entre les équipes d’essai et de simulation et de mettre en œuvre les développements dans une application métier.Après un rappel sur les hypothèses et les méthodes pour l’identification modale, une analyse critique des résultats d’identification aboutit à la caractérisation des biais et à l’introduction de critères détaillés permettant d’évaluer la qualité du résultat. La corrélation calcul/essai permet de qualifier les modèles et des outils sont intégrés pour faciliter sa mise en œuvre. Plusieurs critères sont définis pour mettre en évidence les sources de mauvaise corrélation venant de la mesure d’une part et du modèle d’autre part. Les sources de mauvaise corrélation sont également identifiées avec l’algorithme d’expansion MDRE, dont les limitations sont comparées à celles des expansions statiques et dynamiques.Le recalage des modèles est ensuite traité par une procédure systématique imbriquant les étapes de recalage de la géométrie, des propriétés matériau et des contacts entre composants. Une paramétrisation du contact est proposée avec une réduction multi-modèle permettant des temps de calculs compatibles avec le temps industriel. Elle permet également des études de sensibilités avec l’introduction de la notion de modes de composant dans un assemblage.Une analyse détaillée d’une campagne de mesure sur un système de frein en conditions crissantes est enfin réalisée. Un parallèle entre les évolutions du cycle limite et le degré de couplage des modes complexes est proposé. Dans le domaine temps-fréquence, la variabilité, la répétabilité, la reproductibilité et la possibilité d’agréger des mesures séquentielles sont évaluées. Le résultat obtenu est finalement étendu sur le modèle éléments finis, ce qui permet des interprétations utilesBrake squeal is a nuisance commonly encountered in the car industry which often results in financial penalties towards brake manufacturers, even if no robust solution exists for the conception. Numerical simulation and experimental characterizations are the classical two-track approaches to analyze squeal phenomena. Numerical simulation allows a fine analysis of vibration behaviors and the evaluation of conception modification impacts, but models are not perfect and their validity domain must be defined. Measurement guarantees that every parameter is taken into account, but it is often spatially poor and not really suited for modification prediction. In this context, the thesis objectives are to make an overview of test operating methods, to provide tools allowing an easier interaction between both test and simulation teams and to enforce the developments in a business application.After a review of the hypotheses and methods for modal identification, a critical analysis of the identification results leads to the characterization of biases and the introduction of detailed criteria to evaluate the quality of the result. Calculation/test correlation allows to qualify the models and tools are integrated to facilitate its implementation. Several criteria are defined to highlight the sources of bad correlation coming from the measure on the one hand and the model on the other hand. Sources of poor correlation are also identified with the MDRE expansion algorithm, whose limitations are compared with those of static and dynamic expansions.Model updating is then processed by a systematic procedure imbricating the steps of updating of geometry, material properties and contacts between components. A contact parametrization is proposed with a multi-model reduction allowing calculation times compatible with industrial time. It also allows sensitivity studies with the introduction of the notion of component modes in an assembly.Finally, a detailed analysis of a measurement campaign on a braking system under squeal conditions is carried out. A parallel between the changes of the limit cycle and the degree of coupling of the complex modes is proposed. In the time-frequency domain, variability, repeatability, reproducibility and the ability to aggregate sequential measurements are evaluated. The result is finally extended on the finite element model, which allows useful interpretations
24
Li, Xinzuo William. "A precision laser scanning system for experimental modal analysis : its test and calibration /." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040335/.
Повний текст джерела
25
Santos, Fabio Luis Marques dos. "Strain-based experimental modal analysis: advances in theory and practice." Instituto Tecnológico de Aeronáutica, 2015. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=3386.
Повний текст джерелаАнотація:
The most common and established way of performing experimental modal analysis is to use acceleration based transducers that lead to the calculation of the displacement mode shapes. However, the use of strain measurements for use in experimental modal analysis has gained a lot of popularity in the last couple of years. Not only there are applications where the use of strain measurements makes for a more attractive and interesting option, such as structural health monitoring methods, but there are also applications where sensor size and placement might be critical and therefore strain sensors are the most eligible candidate. This thesis has as the main focus of research the use of strain sensors for experimental modal analysis. In this sense, experimental methodologies and improvements on the current ways of carrying out strain modal analysis are presented, paying particular attention to the relationship between strain and displacement modes. This study of the strain displacement relationship led to the development of a scaling methodology for strain modes and is used to demonstrate the presence of reciprocity under certain conditions. Overall, there are many experimental cases presented in this work, with the main objective of not only validating the theoretical aspects presented in the thesis, but also to provide guidance through the many steps and difficulties associated with experimental strain modal analysis.
26
Clement, Simon. "Mise en oeuvre expérimentale et analyse vibratoire non-linéaire d'un dispositif à quatre maquettes d'assemblages combustibles sous écoulement axial." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4757/document.
Повний текст джерелаАнотація:
Cette thèse s'inscrit dans le cadre général de la tenue au séisme des coeurs de réacteurs nucléaires à eau pressurisée (REP). Plus précisément, l'objectif de cette thèse est l'étude expérimentale du couplage entre assemblages combustibles induit par un écoulement d'eau axial. Les phases de conception, réalisation et mise en service d'une nouvelle installation appelée ICARE EXPERIMENTAL sont présentées. ICARE EXPERIMENTAL a été conçue pour observer simultanément les vibrations de quatre maquettes d'assemblages combustibles (2x2) confinées sous écoulement ascendant. Une nouvelle méthode d'analyse de données combinant analyse temps-fréquence et décomposition sur modes propres orthogonaux (POD) est décrite. Cette méthode, appelée Sliding Window POD (SWPOD), permet l'analyse de signaux à plusieurs composantes dont la répartition spatiale de l'énergie et le contenu fréquentiel varient avec le temps. Dans le cas de systèmes mécaniques (linéaires et non-linéaires), le lien entre les modes propres orthogonaux obtenus par la SWPOD et les modes normaux (linéaires et non-linéaires) est étudié. Les mesures obtenues avec l'installation ICARE EXPERIMENTAL sont analysées avec la SWPOD. Les premiers résultats mettent en évidence des mouvements caractéristiques des assemblages non excités, au passage de leurs résonances. Ce couplage entre assemblages combustibles, induit par le fluide, est reproduit par les simulations réalisées à l'aide du code de calcul COEUR3D. Ce code est basé sur une approche milieu poreux pour simuler un réseau d'assemblages combustibles sous écoulementThe present study is in the scope of pressurized water reactors (PWR) core response to earthquakes. The goal of this thesis is to measure the coupling between fuel assemblies caused an axial water flow. The design, production and installation a new test facility named ICARE EXPERIMENTAL are presented. ICARE EXPERIMENTAL was built in order to measure simultaneously the vibrations of four fuel assemblies (2x2) under an axial flow. A new data analysis method combining time-frequency analysis and orthogonal mode decomposition (POD) is described. This method, named Sliding Window POD (SWPOD), allows analysing multicomponent data, of which spatial repartition of energy and frequency content are time dependent. In the case of mechanical systems (linear and nonlinear), the link between the proper orthogonal modes obtained through SWPOD and the normal modes (linear and nonlinear) is studied. The measures acquired with the ICARE EXPERIMENTAL installation are analysed using the SWPOD. The first results show characteristic behavior of the free fuel assemblies at their resonances. The coupling between fuel assemblies, induced by the fluid, is reproduced by simulations performed using the COEUR3D code. This code is based on a porous media model in order to simulate a fuel assemblies network under axial flow
27
Brien, Christopher J. "Factorial linear model analysis." Title page, table of contents and summary only, 1992. http://thesis.library.adelaide.edu.au/public/adt-SUA20010530.175833.
Повний текст джерелаАнотація:
"February 1992" Bibliography: leaf 323-344. Electronic publication; Full text available in PDF format; abstract in HTML format. Develops a general strategy for factorial linear model analysis for experimental and observational studies, an iterative, four-stage, model comparison procedure. The approach is applicable to studies characterized as being structure-balanced, multitiered and based on Tjur structures unless the structure involves variation factors when it must be a regular Tjur structure. It covers a wide range of experiments including multiple-error, change-over, two-phase, superimposed and unbalanced experiments. Electronic reproduction.[Australia] :Australian Digital Theses Program,2001.
28
Berg, Richard Hiram. "Application of sensors in an experimental investigation of mode dampings /." Online version of thesis, 1993. http://hdl.handle.net/1850/11046.
Повний текст джерела
29
Bouchner, Michal. "Určení NVH parametrů rovinné desky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378142.
Повний текст джерелаАнотація:
The aim of this thesis is examination and verification of numeric model for solving acoustics and vibration problems. Specifically, we are speaking about cast iron plate machined from gearbox. Main objectives of this work is set of experimental and numerical analysis at this simplified part with follow-up numerical model, where same analyses examining not only structure, but especially acoustic space around were performed. Due to this we were able to compare data between experimental and numerical analyses and to be able to prove or disprove functionality and limitation of numerical model.
30
Diaby, M'Paly. "Caracterisation des materiaux viscoelastiques par analyse modale experimentale." Le Mans, 1998. http://www.theses.fr/1998LEMA1010.
Повний текст джерелаАнотація:
Ce travail est consacre a l'identification modale des structures mecaniques du point de vue de leurs constantes elastiques et de leurs amortissements. La connaissance de ces constantes ainsi que la prise en compte des conditions aux limites sont essentielles dans la prediction du comportement dynamique des structures a l'aide des methodes d'elements finis. L'objectif fixe etait de mieux comprendre les modeles d'amortissement et de mesurer les caracteristiques associees par approche modale. Les etudes experimentales ont ete menees au laboratoire sur des poutres en polymetacrylate de methyle et en ertalon dans des configurations libre et encastree libre. Parmi les differentes procedures d'identification modale utilisees, une adaptation de la methode de gauss newton a permis d'ameliorer l'identification des parametres modaux. Cette procedure a ete egalement appliquee a la determination du module complexe avec prise en compte des conditions aux frontieres. Une application industrielle a ete conduite sur un demi arbre de transmission automobile a joints tripodes en collaboration avec renault s. A. Le mans, service ingenierie des joints de transmissions. L'objectif consistait a recaler un modele de frontieres entre la transmission et le vehicule. La comparaison entre les resultats experimentaux et la modelisation par elements finis s'est revelee satisfaisante et cette approche sera etendue a l'optimisation d'une transmission complete en configuration libre puis sur vehicule.
31
Deshpande, Shrirang. "Improving observability in experimental analysis of rotating systems." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1414750479.
Повний текст джерела
32
Sharma, Balaji R. "Feasibility of use of four-post road simulators for automotive modal applications." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277133229.
Повний текст джерела
33
Newton, Wesley E. "Data Analysis Using Experimental Design Model Factorial Analysis of Variance/Covariance (DMAOVC.BAS)." DigitalCommons@USU, 1985. https://digitalcommons.usu.edu/etd/6378.
Повний текст джерелаАнотація:
DMAOVC.BAS is a computer program written in the compiler version of microsoft basic which performs factorial analysis of variance/covariance with expected mean squares. The program accommodates factorial and other hierarchical experimental designs with balanced sets of data. The program is writ ten for use on most modest sized microprocessors, in which the compiler is available. The program is parameter file driven where the parameter file consists of the response variable structure, the experimental design model expressed in a similar structure as seen in most textbooks, information concerning the factors (i.e. fixed or random, and the number of levels), and necessary information to perform covariance analysis. The results of the analysis are written to separate files in a format that can be used for reporting purposes and further computations if needed.
34
Wagner, Benjamin. "Rotating Equipment Defect Detection Using the Algorithm of Mode Isolation." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16230.
Повний текст джерелаАнотація:
Findings from a project involving rotating equipment defect detection using the Algorithm
of Mode Isolation (AMI) are presented. The prototypical system evaluated is a
rotating shaft, supported by hydrodynamic bearings at both ends, with one disk mounted
to the shaft. Shaft cracks and bearing wear are the two equipment defects considered.
An existing model of the prototypical system from the literature, termed the simplified
model. is modified to simulate the presence of a transverse shaft crack at mid-span. This
modified model is termed the standard model. Ritz series analysis, in conjunction with a
previously published description of the compliance related to the presence of a transverse
shaft crack, is used to describe the decrease in shaft stiffness associated with the crack.
The directional frequency response function (dFRF) is shown in the literature to provide
benefits over the standard frequency response function (FRF) in both system identification
and shaft crack detection for rotating equipment. The existing version of AMI is modified
to process dFRFs and termed Two-Sided AMI. The performance of Two-Sided AMI is
verified through system identification work using both the simplified model and a rigid
rotor model from the literature. The results confirm the benefits of using the dFRF for
system identification of isotropic systems. AMI and Two-Sided AMI are experimental modal
analysis (EMA) routines, which estimate modal properties based on a frequency domain
expression of system response. Eigenvalues and associated modal residues are the modal
properties considered in the present work.
Three defect detection studies are fully described. In the first, the simplified model is
used to investigate bearing wear detection. Various damage metrics related to the eigenvalue
and the residue are evaluated. The results show that residue-based metrics are sensitive
to bearing wear. Next, the standard model is used in an in-depth investigation of shaft
crack detection. When a shaft crack is present, the standard model is time-varying in both
the fixed and moving coordinate systems. Therefore, this analysis is also used to evaluate
performing EMA on non-modal data. In addition to continuing the evaluation of various
xiv damage metrics, the shaft crack study also investigates the effects of noise and coordinate
system choice (fixed or moving) on shaft crack detection. Crack detection through EMA
processing of noisy, non-modal data is found to be feasible. The eigenvalue-based damage
metrics show promise. Finally, the standard model is used in a dual-defect study. The
system is configured with both a shaft crack and a worn bearing. One defect is held
constant while the magnitude of the other is increased. The results suggest that AMI is
usable for defect detection of rotating machinery in the presence of multiple system defects,
even though the response data is not that of a time-invariant system. The relative merits
of both input data types, the FRF and the dFRF, are evaluated in each study.
35
Bui, Tuan Anh. "Experimental and numerical uncertain vibration analysis of multilayered timber structures assembled using compressed wood dowels." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0202.
Повний текст джерелаАнотація:
Cette thèse présente une étude expérimentale et numérique sur les aptitudes en service en ce qui concerne le comportement vibratoire de planchers réalisés en bois d’ingénierie sans colle (AFEWP), à savoir les poutres en bois lamellé sans adhésif (AFLB) et les panneaux en bois lamellé-croisé sans adhésif (AFCLT), assemblés par des tourillons en bois densifié (CWD). Les analyses modales expérimentales ont été réalisées en conditions libres-libre à l'aide d'un marteau instrumenté. Les fréquences naturelles, les modes propres et les coefficients d'amortissement ont été évalués expérimentalement. De plus, des poutres en bois lamellé-collé similaires ont été fabriquées et testées à des fins de comparaison. Un modèle EF 3D a été développé et validé par comparaison avec des données expérimentales, puis utilisé pour prédire le comportement vibratoire d'un système de plancher à grande échelle réalisé avec un panneau AFCLT mesurant 4,5 m x 5,5 m. Une étude paramétrique a été réalisée en utilisant le modèle EF pour identifier les paramètres qui influent sur la rigidité et les fréquences propres du plancher. Les résultats obtenus ont été analysés au regard des critères de conception exigés par Eurocode 5 en ce qui concerne le confort vibratoire des planchers bois. Un modèle EF simplifié a ensuite été développé pour réduire les coûts de calcul. Le niveau de variabilité des résultats des AFEWP a été également étudié et discuté. La variabilité numérique des fréquences des AFEWP a été étudiée en utilisant la méthode MSP (Modal Stability Procedure). Les résultats de la méthode MSP ont d'abord été comparés aux résultats EF dans le cas nominal. Les résultats statistiques (valeur moyenne, écart type, coefficient de variation et distribution) obtenus par la méthode MSP ont été confrontés aux résultats de simulation directe de Monte Carlo ainsi qu’aux données expérimentales. Une estimation rapide des erreurs entre la méthode MSP et la simulation directe de Monte Carlo a été développée. Enfin, la variabilité (moyenne et écart-type des fréquences) du comportement vibratoire du système de plancher à grande échelle a été étudiée en utilisant la méthode MSPThis study presents an experimental and numerical investigation on the vibrational serviceability performance of novel adhesive free engineered wood products (AFEWPs), namely adhesive free laminated timber beams (AFLB) and adhesive free cross-laminated timber panels (AFCLT), assembled through thermo-mechanically compressed wood dowels (CWD). The experimental modal analyses were carried out under free-free conditions using a hammer impact. Natural frequencies, mode shapes, and damping ratio were assessed experimentally. In addition, similar glued timber beams (conventional glulam) were manufactured and tested for comparison purpose. A 3D FE model was developed and validated by comparison against experimental data and then used to predict the vibrational behavior of a realistic flooring system made with AFCLT panel measuring 4.5 m x 5.5 m. A parametric study was performed on the FE model to maximize the floor stiffness. The predicted FE results were discussed with regard to the Eurocode 5 vibrational serviceability design requirements showing acceptable vibrational performance. A simplified FE model was then developed to reduce computational cost. The variability level of the results for the AFEWPs was also studied and discussed. The numerical variability of frequencies of the AFEWPs was investigated based on the development of the Modal Stability Procedure (MSP). The MSP result was first compared with the FE result in the nominal case. Then, the statistic results (mean value, standard deviation, coefficient of variation and distribution) obtained from the MSP were compared with the results from the classical method (direct Monte Carlo simulation) and experimental results. A quick error estimation between the MSP and the direct Monte Carlo simulation was developed. Finally, the mean and standard deviation of the frequencies of the realistic AFCLT flooring system were predicted by the MSP
36
Poncet, Mélissa. "Effet de l'incorporation de systèmes hybrides sur les propriétés mécaniques de matériaux composites à matrice époxyvinylester et polyester insaturé." Thesis, Paris, ENMP, 2013. http://www.theses.fr/2013ENMP0025/document.
Повний текст джерелаАнотація:
Ce travail de thèse porte sur l'élaboration d'un matériau composite à matrice thermodurcissable incorporant des renforts nanométriques et/ou une phase élastomère, permettant d'améliorersa rigidité, son amortissement et sa résilience. Pour cela, nous avons réalisé des formulations baséessur des matrices époxyvinylester, renforcées ou non par une phase élastomère et chargées de montmorillonite ou de sépiolite. Nous avons étudié leurs propriétés visco-élastiques par analyse modaleexpérimentale et leurs propriétés à l'impact par des essais d'impact par chute de masse. Nous avonsdéterminé la microstructure des composites fabriqués en nous appuyant sur la diffraction des rayonsX et des observations en microscopie électronique. Des modèles d'homogénéisation, fondés sur lemodèle de H ALPIN -T SAI et adaptés aux matériaux composites étudiés, ont été développés afin dedisposer d'un outil permettant de relier explicitement la rigidité des composites à leur morphologie.Une analyse paramétrique approfondie a permis de déterminer les caractères morphologiques lesplus influents et d'évaluer la performance des procédés de mise en œuvre au regard des renforcements mécaniques obtenus. Expérimentalement, l'incorporation de montmorillonite ou de sépiolite a conduit à une augmentation significative du module élastique et la présence d'une phase élastomère dans la résine a permis de doubler l'amortissement et d'augmenter la résilience. Finalement, les formulations les plus performantes ont été retenues pour la fabrication de composites renforcés de fibres de verre. L'amélioration des propriétés mécaniques se retrouve, dans une moindre mesure, dans lesprototypes réalisés. La pertinence de l'utilisation de ces matériaux à l'échelle industrielle a été évaluéeThis thesis focuses on the development of a thermosetting matrix composite incorporating nanoscale reinforcements and/or an elatomeric phase to improve its stiffness, damping and resilience.To do so, we made formulations based on epoxy vinyl ester matrices, filled or not by an elastomeric phase, and reinforced with montmorillonite or sepiolite. Their viscoelastic properties were studied usingexperimental modal analysis and their impact properties were investigated using drop weight impacttesting. The microstructure of these composites was examined using X-ray diffraction and electronmicroscopy observations.Homogenization models based on H ALPIN -T SAI model and adapted to the studied composites were developed to provide a tool able to explicitly link the stiffness of the material to its morphology.A detailed parametric analysis allowed to determine the most influential morphological characteristics and to assess the efficiency of the process regarding the mechanical stiffening obtained.Experimentally, the incorporation of montmorillonite or sepiolite led to a significant increase in the elastic modulus and, with the presence of an elastomeric phase in the resin, the damping was doubled and the resilience was increased.Finally, the most efficient formulations were used to manufacture glass fibers reinforced composites.The improvement in mechanical properties was found, to a lesser extent, for the manufactured prototypes.The relevance of the use of these materials on an industrial scale was evaluated
37
Zhou, Lixing. "Dynamic generalized (multiple-set) structured canonical correlation analysis (dynamic GCANO): a structural equation model for simultaneous analysis of multiple-subject effective connectivity in functional neuroimaging studies." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123190.
Повний текст джерелаАнотація:
Effective connectivity in functional neuroimaging studies is defined as the time dependent causal influence that a certain brain region of interest (ROI) exerts on another. Structural equation modeling (SEM) is regularly employed to analyze effective connectivity. In recent years, various SEM methods have been proposed to model effective connectivity. However, there has been little attempt to develop SEM methods for analyzing common patterns of effective connectivity across subjects despite the prevalence of multiple-subject research in effective connectivity. This dissertation proposes a method that fills this gap. This method is called dynamic generalized (multiple-set) structured canonical correlation analysis (dynamic GCANO). It combines generalized (multiple-set) canonical correlation analysis (GCANO) with a multivariate autoregressive time series model in a unified framework. This dissertation begins with a brief review of existing SEM techniques, and points out their limitations in analyzing multiple-subject effective connectivity data, which serves as a motivation to develop dynamic GCANO. The technical underpinnings of the proposed method are then stated, including specifications of a modeling framework and an optimization criterion for parameter estimation, which is minimized by an alternating least squares algorithm. The effectiveness of dynamic GCANO is demonstrated by analyzing both synthetic and real data sets. The former reveals reasonably good parameter recoveries by the proposed method, while the latter shows the usefulness of the method in empirical research. Several features of dynamic GCANO are highlighted through these examples. The dissertation concludes with possible extensions of the proposed method.Suivant les méthodes d'imagerie fonctionnelle cérébrale, une connectivité efficace est définie comme influence dépendant de causalité temporelle qu'une certaine région d'intérêt du cerveau (ROI) exerce sur une autre. La modélisation par équation structurelle (SEM) est régulièrement utilisée pour analyser la connectivité efficace. Ces dernières années, diverses méthodes de SEM ont été proposées pour la modélisation de la connectivité efficace. Cependant, il y a eu peu de tentative pour développer des méthodes de SEM pour analyser les modèles communs de connectivité efficace sur-sujets, malgré la prédominance de recherche sur des sujets multiples pour analyser la connectivité efficace. Cette thèse propose une méthode qui comble cette lacune. Cette méthode est appelée dynamique généralisée (multiples ensemble) structuré l'analyse de corrélation canonique (dynamique GCANO). Elle combine généralisée (multiples ensemble) structuré l'analyse de corrélation canonique (GCANO) avec multivariée des séries chronologiques autorégressif dans un cadre unifié. Cette thèse commence par un bref sommaire sur les techniques existantes de SEM et souligne leurs limites pour analyser les données de plusieurs sous réserve pour la connectivité efficace, ce qui a mené à développer la dynamique GCANO. Les techniques de base de la méthode proposée sont ensuite énumérées, y compris les spécifications du cadre de modélisation et un critère d'optimisation pour l'estimation de paramètres, qui est réduit par alternant algorithme des moindres carrés. L'efficacité du dynamique GCANO est démontrée par l'analyse des ensembles de données synthétiques et réels. Les données synthétiques montrent une récupération raisonnable de paramètre par la méthode proposée, alors que les données réelles montrent l'utilité de la méthode dans les recherches empiriques. Plusieurs fonctionnalités du dynamique sont mises en évidence par le biais de ces exemples. En conclusion, la thèse propose des extensions possibles de la méthode proposée.
38
Morone, Daniel Justin Reese. "Progressive Collapse: Simplified Analysis Using Experimental Data." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354602937.
Повний текст джерела
39
Libardi, Ana Lúcia. "Técnicas de cancelamento de massa em análise modal experimental." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-11072018-120016/.
Повний текст джерелаАнотація:
Esta dissertação tem como objetivo principal o estudo das técnicas de cancelamento de massa, bem como suas aplicações em análise modal experimental. Estas técnicas são utilizadas na redução de determinados erros nos dados de resposta em frequência da estrutura sob estudo. Estes erros são por sua vez causados por fontes adicionais de inércia, tais como acelerômetros e transdutores de força, que são frequentemente utilizados nos ensaios para o levantamento das características dinâmicas da estrutura. As técnicas de cancelamento de massa estudadas neste trabalho são desenvolvidas a partir de uma modelagem das relações de entrada e saída no domínio da frequência, utilizando-se para tanto as Funções de Resposta em Frequência (FRF), bem como conceitos de subestruturação. Os modelos analíticos utilizados no problema de cancelamento de massa são também aplicados na geração de FRFs desconhecidas para a estrutura sob estudo, a partir de um subconjunto de FRFs medidas com massas adicionais acopladas à estrutura. Os métodos estudados são aplicados a dados obtidos através de simulações numéricas em sistemas discretos, bem como a dados experimentais provenientes de ensaios em estruturas simples. Resultados satisfatórios foram obtidos tanto a partir das simulações numéricas quanto na análise experimental para o problema de cancelamento de massa. Na obtenção de FRFs desconhecidas, verificou-se que os modelos teóricos conduzem a resultados satisfatórios em determinadas situações, e que o ruído encontrado em dados experimentais representa um fator detrimental na utilização das técnicas de cancelamento de massa para o propósito de gerar-se FRF desconhecidas a partir de FRF efetivamente medidas na estrutura sob estudo.The goal of this dissertation is to develop a study on mass cancellation techniques and their applications in experimental modal analysis. These techniques are commonly employed in the reduction of experimental errors on the structure\'s measured frequency response data. Such errors are in turn caused by extra masses such as accelerometer and force transducers, that are utilized on the measurement of the system\'s Frequency Response Functions (FRF). The mass cancellation techniques studied here are developed through frequency domain input and output relationships as well as substructuring concepts. The analytical models employed in the mass cancellation problem are also applied in obtaining unknown FRF from a subset of measured FRF that are measured with extra masses attached to the structure. The methods studied are applied to numerically simulated data from discrete systems, as well as to experimental data coming from modal tests performed on simple structures. Reasonably good results are obtained in either the numerical and experimental analysis for the mass cancellation problem. In obtaining unknown FRF data, it was verified that the models generated reasonable results in some circumstances, and that experimental noise is a major source of error in using these mass cancellation techniques for the purpose of obtaining unmeasured data from a subset of measured FRF.
40
Han, Man-Cheol. "Improved approaches to the indirect force determination problems via experimental modal analysis." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39412.
Повний текст джерелаАнотація:
Solving the inverse problem, finding the applied forces knowing the system characteristics and the response, has been a difficult problem in structural dynamics. Insufficient accuracy in the system identification and uncorrelated content in the response exacerbate the ill-conditioned nature of the indirect-force-determination problem. Numerical techniques for performing the force determination are exploited and compared. The characteristics of the force determination problems are investigated through least squares solution procedures and numerical examples. The credibility of the estimated forces are studied in the numerical examples using the correlations of the matrix condition number and the mode contribution factor with the resulting error.
The focus of this research is the improved estimation of the applied forces. The two important factors in reducing the force determination error are accurate system identification and improved conditioning of the system matrix. A variety of techniques are examined to reduce the system identification error and control the response measurement uncertainty. The use of rotational or curvature degrees of freedom as an alternative to the translational degrees of freedom for the response measurements and for the structural dynamics model yields a quite differently conditioned system matrix. The choice of a particular degrees of freedom is shown to depend on the frequency contents of the applied forces.Ph. D.
41
Koricherla, Manindra Varma. "An experimental modal analysis of an Lithium-ion Battery using Dynamic Excitation." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1502476407014686.
Повний текст джерела
42
Oliveira, Junior Adelmo Fernandes de [UNESP]. "Estudo das características modais de um modelo de aeronave em alumínio." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/148651.
Повний текст джерелаАнотація:
Submitted by Adelmo Fernandes de Oliveira Junior null (ligley@gmail.com) on 2017-01-27T18:02:21Z
No. of bitstreams: 1
Dissertação Adelmo - 26-01-2017.pdf: 2029608 bytes, checksum: 09e6922ea4afa079b64bac18ef6882ba (MD5)Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-01-31T16:02:22Z (GMT) No. of bitstreams: 1 oliveirajunior_af_me_guara.pdf: 2029608 bytes, checksum: 09e6922ea4afa079b64bac18ef6882ba (MD5)
Made available in DSpace on 2017-01-31T16:02:22Z (GMT). No. of bitstreams: 1 oliveirajunior_af_me_guara.pdf: 2029608 bytes, checksum: 09e6922ea4afa079b64bac18ef6882ba (MD5) Previous issue date: 2016-12-02
A análise modal experimental é uma das técnicas mais importantes na caracterização dinâmica de estruturas. No setor aeroespacial a analise modal experimental é conhecida como Ground Vibration Test (GVT). Na Força Aérea Brasileira, o órgão responsável para executar o GVT é o Laboratório de Ensaios de Vibração (LEVI) da Divisão de Integração e Ensaio (AIE) do Instituto de Aeronáutica e Espaço (IAE). Esta pesquisa foi realizada neste laboratório que possui as facilidades para a execução de GVT. O objetivo principal deste estudo foi aprimorar a metodologia de ensaio de análise modal aplicada a um modelo de aeronave em alumínio do tipo GARTEUR SM-AG-19. O estudo desenvolvido possibilita que em ensaios futuros os resultados sejam replicados, no intuito de avaliar a integridade do sistema de medição, levando em consideração aspectos da influência do torque na junta aparafusada entre a asa e a fuselagem. Para validar a metodologia os resultados obtidos neste estudo foram comparados com os resultados de dois estudos desenvolvidos no Brasil. A contribuição principal desta pesquisa é relacionada ao estudo do efeito da variação do torque na junta aparafusada entre a asa e a fuselagem sobre os parâmetros modais da estrutura.
The experimental modal analysis is one of the most important techniques in the dynamic characterization of structures. In the aerospace industry, the experimental modal analysis is known as Ground Vibration Test (GVT). In the Brazilian Air Force, the institution responsible for executing the GVT is the Laboratory of Vibration Testing (LEVI) of the Integration and Testing Division (AIE) of the Institute of Aeronautics and Space (IAE). This research was carried out on this laboratory that has the facilities to perform the GVT. The main objective of this study was to improve the modal analysis test methodology applied to an aluminium aircraft model named GARTEUR SM-AG-19. This study allows the results to be replicated in future tests in order to evaluate the integrity of the measurement system, taking into account aspects of the influence of the torque on the bolted joint between wing and fuselage. In order to validate the methodology the results obtained in this study were compared to the results of two studies developed in Brazil. The main contribution of this research is the study of the torque variation effect on the bolted joint between wing and fuselage on the modal parameters of the structure.
43
Jardim, Maurício Ferreira [UNESP]. "Análise teórica e experimental vibro-acústica utilizando a técnica de matrizes compactas." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/94549.
Повний текст джерелаАнотація:
Made available in DSpace on 2014-06-11T19:27:14Z (GMT). No. of bitstreams: 0
Previous issue date: 2008-12-22Bitstream added on 2014-06-13T19:14:29Z : No. of bitstreams: 1
jardim_mf_me_ilha.pdf: 2211660 bytes, checksum: 2278321e3f739e77b4a47c1e179ff125 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Em muitos problemas do nosso cotidiano ocorre acoplamento entre a resposta acústica no interior de uma cavidade e a excitação estrutural em um de seus contornos flexíveis, bem como a resposta estrutural nestes contornos também está relacionada à fonte acústica da cavidade. Interior de automóveis, cabine de caminhões e fuselagem de aviões são apenas alguns exemplos práticos destes tipos de sistemas. Acoplamento implica que o comportamento dos sistemas acústico e estrutural não são independentes um do outro, e ambos devem ser considerados como um único sistema global. O propósito deste trabalho é avaliar a técnica de matrizes compactas na solução de problema de acoplamento vibroacústico em cavidades de geometria regular e irregular. Preliminarmente, a análise do acoplamento vibro-acústico é baseado no método dos elementos finitos e o conjunto de equações não simétricas que modela o movimento é discutida. A aproximação vibro-acústica por matrizes compactas é feita utilizando conceitos de impedância e mobilidade. No modelo de matrizes compactas, o acoplamento é obtido através da avaliação dos modos acústicos e estruturais desacoplados da cavidade e da estrutura flexível, respectivamente. Simulações numéricas utilizando o método dos elementos finitos e a técnica de matrizes compactas são apresentadas para modelos vibro-acústicos de geometria regular e irregular. Testes experimentais são realizados em uma cavidade irregular feita de PVC e aço. A metodologia de análise dos resultados é baseada nas FRF(s) definidas pelas relações entre a resposta em pressão acústica da cavidade e a força estrutural e entre a resposta em velocidade e a força estrutural aplicada sobre a superfície flexível. A comparação dos modelos numéricos e experimentais mostra o potencial da técnica de matrizes compactas.
In many systems of day-life occurs the coupling between the acoustical response in a cavity and a structural excitation on a flexible boundary, whereas the structural response in this same boundary is also related to acoustical excitation source. Car interiors, cabs of trucks and aircraft fuselage are a just a few practical examples of this sort of systems. Coupling implies that the acoustical and structural system behavior is not independent from each other, and therefore they must be considered as a global system behavior. The aim of this work is to evaluate a compact matrix formulation to solve vibro-acoustic problems in regular and irregular shape cavity. Preliminary, the vibro-acoustic coupling analysis is based on finite element method and the set of non-symmetric equation that represents the movement is discussed. The compact matrix formulation approaches have been done using impedance and mobility concepts. In compact matrix model, the coupling is obtained by evaluating the uncoupled acoustic modes and structural modes of the cavity and flexible structure, respectively. Numerical simulation using the finite element method and the compact matrix formulation are shown for regular and irregular shape cavity model. Experimental tests are evaluated in an irregular rigid cavity made of PVC and steel. The results analysis methodology is based on FRF(s) defined by the relationship between the pressure acoustic response in the cavity and structural force and between the velocity response and structural force applied on the flexible boundary. The comparison of numerical and experimental models shows the potential of the compact matrix formulation.
44
Karim, Ali Abdul Jabbar, Johan Lessner, and Mehrdad Moridnejad. "Model calibration of a wooden building block." Thesis, Linnéuniversitetet, Institutionen för bygg- och energiteknik (BE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-26271.
Повний текст джерелаАнотація:
Constructing multi floor buildings by light weight material have increased recently. There are many advantages of using light weight material, such as wood, for the environment. However, one of the deficiencies of lightweight material is the acoustic performance. Transmission of sound and vibration through floors in multi floor buildings in wood is a drawback to be considered. There are many studies that have addressed this issue. It is most common to make a finite element models well as experiments in laboratory. In these studies the material properties in the FE model are probably often adjusted to correlate to the laboratory experiments, since there is a large spread in material properties found in literature. This thesis however tries to elaborate on the actual material properties of the included wooden elements. Dynamic testing is done to determine the spread (here spread means gap between material properties) in material properties of wooden elements. The materials tested are chipboards and two types of wooden beams. The examined beams are both normal wooden beams and laminated veneer lumber beams. When the dynamic behaviour is known for the wooden parts, they are assembled to two small floor systems. The floor systems consist of four beams and one wooden board. The assembly is dynamically tested in laboratory and in FE software. The FE model used the known material properties for each individual building part. The results from the FE model correlate well with the laboratory tests. This shows that when material properties are known a FE model can predict the real behaviour. However, the examined material properties show a large spread from beam to beam, etc and a better knowledge about the material properties of used wooden parts is needed.Att bygga flervåningshus med lätta byggmaterial har blivit allt vanligare. Det finns många fördelar med att använda lätta material, såsom trä. En av fördelarna är att det är skonsamt för miljön. Emellertid är en av bristerna i lättviktsmaterial den akustiska prestandan. Överföring av ljud och vibrationer genom golv i flervåningshus i trä är en nackdel att överväga. Det finns flera studier som har behandlat denna fråga. Ofta görs finita element modeller samt tester i laboratorium. I dessa studier justerar man materialegenskaperna i FE-modellen för att korrelera mot laboratorieexperiment. Detta eftersom det finns en stor spridning i materialegenskaperna för trä i litteraturen. Med detta examensarbete, undersöks de faktiska materialegenskaperna hos träelementen genom försök. Dynamiska tester utförs för att bestämma spridningen i materialegenskaper. De testade materialen är spånskivor och två typer av träbalkar. De undersökta balkarna är både normala träreglar och laminerade faner balkar. När det dynamiska beteendet är känt för trädelarna, monteras de ihop till två små golvsystem. Golvsystemen består av fyra balkar och en träskiva. Den assemblerade modellen testas både dynamiskt i ett praktiskt försök och i ett FE program. I FEmodellen används de tidigare framtagna faktiska materialegenskaper för varje ingående enskild byggnadsdel. Resultaten från FE-modellen korrelerar väl med de praktiska experimenten. Med detta examensarbete visas att när materialegenskaperna är kända kan FE-modellen förutsäga det verkliga beteendet. De undersökta materialegenskaperna visar dock en stor spridning från balk till balk, etc. och mer kunskap om materialegenskaper hos trädelar behövs.
45
Nunes, Alexandre. "Analise modal teorica e experimental acustica de cavidades com absorção sonora." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265183.
Повний текст джерелаАнотація:
Orientador : Renato PavanelloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-07-31T21:52:13Z (GMT). No. of bitstreams: 1 Nunes_Alexandre_M.pdf: 10234250 bytes, checksum: b23f996b5cfd8fd277d5617e0bb9956c (MD5) Previous issue date: 2001
Mestrado
46
Estep, Robert Noah. "Examination of the application and limitations of structural mode extraction via force apportionment." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-02132009-172353/.
Повний текст джерела
47
Rose, John A. "The experimental characterization of the dynamics of a reciprocating freon compressor system." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12302008-063244/.
Повний текст джерела
48
Baldassarre, Alessandro. "FEM and experimental analysis of a wind turbine blade." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8533/.
Повний текст джерелаАнотація:
This paperwork compares the a numerical validation of the finite element model (FEM) with respect the experimental tests of a new generation wind turbine blade designed by TPI Composites Inc. called BSDS (Blade System Design Study). The research is focused on the analysis by finite element (FE) of the BSDS blade and its comparison with respect the experimental data from static and dynamic investigations. The goal of the research is to create a general procedure which is based on a finite element model and will be used to create an accurate digital copy for any kind of blade. The blade prototype was created in SolidWorks and the blade of Sandia National Laboratories Blade System Design Study was accurately reproduced. At a later stage the SolidWorks model was imported in Ansys Mechanical APDL where the shell geometry was created and modal, static and fatigue analysis were carried out. The outcomes of the FEM analysis were compared with the real test on the BSDS blade at Clarkson University laboratory carried out by a new procedures called Blade Test Facility that includes different methods for both the static and dynamic test of the wind turbine blade. The outcomes from the FEM analysis reproduce the real behavior of the blade subjected to static loads in a very satisfying way. A most detailed study about the material properties could improve the accuracy of the analysis.
49
Saha, Reema. "Investigation of a continuum damage model using experimental and numerical techniques." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12542.
Повний текст джерела
50
Nilsson, Oscar. "Experimental Procedures for Operational Modal Analysis of a Power Pack on a Drill Rig." Thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-143046.
Повний текст джерелаАнотація:
All structures have modal properties such as natural frequencies and damping. In engineeringit is often of interest to estimate these modal properties for certain structures, to be used whenmodelling for example fatigue. This is done by computing them from finite element models, by using experimental measurements or both. In the case of doing both, a finite elementmodel is usually established first and adjusted to fit measurements from experiments. Atlas Copco Rock Drills AB is the company where this thesis has been performed and the subject is experimental procedures related to estimating modal properties of the so calledpower pack, which essentially is a modularised engine and hydraulic power source of an Atlas Copco drill rig. Their current method for estimating these properties is a classical procedure which makes use of an impact hammer that an operator strikes the power pack with to induce excitation. Due to concealment of behind other parts the power pack when mounted inside the drill rig, the number of places where the operator is able to strike the power pack in is limited. Another problem with the current procedure is that it can be difficult to strike the power pack with a strong enough impulse to generate reliable results. In this thesis a new experimental procedure for Atlas Copco to use is suggested. It is based on operational modal analysis (OMA), which uses the machinery's excitation from its operational conditions to compute modal estimates. A comparison between different experimental procedures have been done and the suggested procedure is the following: excitation by engine sweep; modal identifcation by the PolyMAX method and mode shape scaling by the harmonic scaling method. An experiment was performed to compare two OMA procedures.The suggested procedure is the one that generated the better results of the two.