Dissertations / Theses on the topic 'Quasi-static analysis'
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Gotts, Anthony C. "Finite element analysis of dynamic linear viscoelastic materials." Thesis, Coventry University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246580.
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Gehin, Jess C. (Jess Charles). "A quasi-static polynomial nodal method for nuclear reactor analysis." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/17309.
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Joni, Jeffry Hartono. "Quasi-static force analysis of an automated live-bird transfer system." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16781.
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Prewitt, Thomas Joseph. "Quasi-static, Deformable-body Analysis of a Face Gear-Thrust Bearing System." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1344867144.
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Pandey, Vinayak. "Quasi-Static and Creep Behavior of Enhanced SIC/SIC Ceramic Matrix Composites." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33959.
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Continuous Fiber Reinforced Ceramic Composites (CFCC's) are being currently investigated as potential materials for high temperature applications such as combustor liners in stationary gas turbines. The creep behavior of woven Enhanced SiC/SiC composites was studied at temperatures from 600 to 1200 °C and at 140 to 220 MPa stress levels. Most researchers studying the creep behavior of ceramic matrix composites (CMCs) use the time hardening model and rate equations for expressing the dependence of creep strain on time, temperature and stress. Such laws, although simple and easy to use, are inadequate to represent the creep behavior over a range of stress levels and temperatures and cannot be used to quantify the pest phenomenon commonly observed in CMCs. Hence, these laws were modified to include the pest phenomenon and an empirical equation was developed that can be used to represent the creep behavior at various stresses and temperatures. The modified equation was used in the finite element analysis and the results were compared with the time and strain hardening models. Microscopic observations on the fractured surfaces revealed the pseudo-ductile behavior of the material at high temperatures. A quasi-static test was conducted at 1200 °C to determine the unloading response of the material. The stress-strain response of the composite demonstrates a hysterisis loop and a small amount of permanent strain, which are characteristic of the CMC's [3]. Finally, a test was
conducted at 1200 oC to investigate the recovery behavior of the material. The material exhibits a tendency to recover the accumulated creep strain as well as the small permanent strain upon unloading, if sufficient time is allowed for recovery.
The creep data were also modeled using the representations such as Monkmon-Grant and Larsen-Miller equations. A modified Monkman-Grant equation was used to model the stratification of the creep strain rate data with temperature. A finite element model based on the plasticity theory was developed to simulate the quasi-static cyclic behavior of the material. Though the loading behavior of CMCs can be modeled using the bilinear or multilinear kinematic hardening plasticity models, the unloading behavior as predicted by the models is entirely different from the experimentally observed behavior. Hence, these models were modified to correctly predict the stress-strain behavior. The model, which was input via a user defined subroutine into the ANSYS finite element program uses the concept of state or internal variables to define the unloading portion of the stress-strain curve. The results were compared with the test data and they show very good agreement. The model was then used to predict the stress-strain response of a plate with a notch. The results from the analysis were compared with the experimental data and they show good agreement if average values of strains are considered.
Master of Science
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Ghafoori, Roozbahany Ehsan. "Fracture testing and evaluation of asphalt pavement joints in quasi static tension mode." Thesis, KTH, Väg- och banteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96672.
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Asphalt joints are inevitable parts of every pavement. They are constructed for different reasons. Although much attention is dedicated to the construction joints (hot with hot pavement), a scientific approach for cold joints (cold with hot pavement) with respect to large patch constructions is still missing. This report tries to evaluate existing construction techniques and to suggest new testing methods of tests. Although, indirect tensile tests IDT and direct tension tests DTT are familiar in the field of asphalt pavement characterization, they have not been used for the assessment of joint quality so far. In this report, these two test types are evaluated and the results are analyzed using finite element software ABAQUS. The results of the comparison of joint compaction techniques on a laboratory scale suggest that joints with angles seem to show more promising behavior than vertical joints. Also, starting compaction from the hot side generally produces better results than compaction starting from cold side.
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Harris, John O. Spence Allan D. "Geometric and quasi-static thermal error compensation of a laser digitizer on a coordinate measuring machine." *McMaster only, 2004.
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Chai, K. W. "Unified non-quasi-static current modelling of the long-channel four-terminal MOSFET for large-signal analysis." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636220.
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Puigvert, Cobos Francesc. "Analysis of circular bond-type anchorages for prestressing composite rods under quasi-static, fatigue and time-dependent loads." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284216.
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En estructures pretesades sotmeses a ambients corrosius, s'està estudiant la possibilitat de substituir els tendons d’acer per tendons que no pateixin els efectes de la corrosió. En aquest sentit, els materials compostos Fibre Reinforced Polymer (FRP) són una opció duradora en el disseny d'estructures de formigó pretesat degut a les seves altes propietats mecàniques, pes lleuger i alta resistència a la corrosió. No obstant,
un dels reptes associats amb aquesta opció es troba en el desenvolupament d'un sistema d'ancoratge adequat
per als tendons de FRP .
Per això aquesta investigació ha estudiat la resposta mecànica d’ancoratges d’unió adhesiva per a tendons de FRP sota càrregues quasi-estàtiques, de fatiga i en funció del temps. Aquest objectiu s'ha aconseguit mitjançant la combinació d'una campanya experimental i un treball de modelatge amb el mètode dels elements finits.
En aquest sentit s’han dut a terme assaigs experimentals quasi-estàtics en els ancoratges d’unió adhesiva, observant que la ruptura del sistema es produïa en la unió adhesiva entre l’adhesiu i el tendó. En conseqüència, les principals variables estudiades van ser l’espessor de l'adhesiu i la longitud d’adhesió. A través d’una campanya de modelatge numèric amb diferents models, de complexitat creixent, del material adhesiu, es va investigar la resposta quasi-estàtica de l'ancoratge i el seu mecanisme de fallada. El model numèric va ser capaç de predir les dades enregistrades experimentalment quan el modelatge de l’adhesiu es va realitzar amb elements cohesius amb dany progressiu.
A més, s’ha desenvolupat una formulació analítica (i validat amb èxit) amb l'objectiu de proporcionar una distribució aproximada de les tensions de tall que es produeixen en la capa adhesiva per ancoratges amb adhesius que es comporten principalment elàstic lineal fins a ruptura. D’altra banda l'ancoratge d’unió adhesiva també es va investigar sota els fenòmens dependents del temps.
Per això es van dur a terme assaigs de fluència en unions simples Single Lap Joints ( SLJs ), per tal d'obtenir una llei experimental de fluència, i es van realitzar assaigs de relaxació de la tensió en els ancoratges per estudiar la pèrdua de càrrega en funció del temps. Durant aquests assaigs de relaxació es va estudiar la tècnica del retesat amb l’objectiu d’estudiar l’evolució de les pèrdues de tensió. Es va observar que la tècnica del retesat permet assolir càrregues de treball superiors amb una pèrdua de càrrega mínima.
A més a través d’un model visco-plàstic es va predir el temps de fallada a fluència de les SLJs i els ancoratges, basat en la llei de Bailey-Norton i calibrat amb les dades experimentals obtingudes en els assaigs de fluència de les SLJs. El dany de fluència es va modelar mitjançant la degradació de la tensió de fluència plàstica de l'adhesiu i el model numèric es va utilitzar per predir la pèrdua de càrrega dels ancoratges sota el fenomen de relaxació de la tensió. Els resultats enregistrats experimentalment van ser predits adequadament amb el model numèric proposat.
Finalment, es va investigar la resposta a la fatiga dels ancoratges d’unió adhesiva. Es van avaluar quatre configuracions d’ancoratge sota tres càrregues de fatiga d'amplitud constant. Els resultats experimentals van permetre l’obtenció d’una corba de vida a fatiga dels ancoratges en funció del nombre de cicles.
Mitjançant el mètode d’elements finits, també es va investigar el comportament a fatiga. La llei cohesiva obtinguda en l'anàlisi quasi-estàtic es va utilitzar en el model de la fatiga, on el dany per fatiga s’ha basat en la degradació de les propietats dels elements cohesius. El model numèric va predir amb èxit l'evolució dany per fatiga i la vida per fatiga observada experimentalment .
A partir del treball experimental i numèric realitzat en aquesta recerca, es proposen les recomanacions més pertinents per a un possible ús dels ancoratges d’unió adhesiva per tendons FRP en aplicacions de pretensat.In prestressed structures subjected to corrosive environments, consideration is being given to replacing the steels tendons with non-corrosive tendons. In this respect, Fibre Reinforced Polymer (FRP) materials are a durable option in the design of prestressed concrete structures for use in corrosive environments due to their high mechanical properties, light weight and high resistance to corrosion. However, one of the challenges associated with this option lies in developing a suitable anchorage system for FRP tendons. In the present work, the mechanical response of circular adhesively bonded anchorages for FRP tendons has been investigated under quasi-static, time-dependent and fatigue loading. This has been achieved through a combination of an experimental campaign and finite element modelling work. Experimental quasi-static tests of adhesively bonded anchorages were undertaken with failure occurring in the adhesive-tendon interface. The main variables assessed were the adhesive thickness and the bonded length. In order to investigate the quasi-static response of the bonded anchorage and its failure mechanism, a campaign of numerical modelling was carried out with different material models of increasing complexity for the adhesive layer. A cohesive zone model with progressive damage in the bonded joint was found to be in reasonable agreement with the experimentally recorded data. Additionally, an analytical formulation was developed (and validated against experimental data) with the aim to provide an approximate shear stress distribution in the bonded joint for circular anchors with adhesives which mainly behave linearly elastic up to failure. The adhesively bonded anchor for FRP tendons was also investigated under the time-dependent phenomena. Creep tests on Single Lap Joints (SLJs) were conducted in order to obtain an experimental creep law whereas stress relaxation tests were conducted on adhesively bonded anchorages to study the load loss in time. Furthermore, the restressing technique was assessed during the stress relaxation tests by restressing the specimens, to the original tensioning load, when the load loss was stabilised and constant. It was found that the restressing technique allows for the working load of the composite tendon to be reached with a minimum load loss. A visco-plastic material model, based on the Bailey-Norton law, was calibrated with the experimental data obtained from the creep tests and utilised to predict the creep time to failure of SLJs and anchorages. The creep damage was modelled by degrading the plastic yield stress of the adhesive. The viscoelastic model was also used to predict the load loss of the anchors under the stress relaxation phenomenon. The predicted load loss results were found to be in good agreement with the experimental results recorded. Finally, the fatigue response of the bonded anchorages was investigated. Anchorages with four different adhesive thicknesses were evaluated under three constant amplitude fatigue loadings. The experimental fatigue response of adhesively bonded anchorages was discussed and an experimental load-life average curve was obtained for all the anchorages. The fatigue behaviour was also predicted using Finite Element Analysis. A multi-linear traction-separation cohesive zone model was implemented at the adhesive-tendon interface. The cohesive law obtained in the quasi-static analysis was utilised in the fatigue model. The fatigue damage model utilised in this research was based on the degradation of the cohesive elements taking into account the fatigue damage evolution. The damage model was able to successfully predict the fatigue damage evolution and failure life experimentally observed. From the experimental and numerical work conducted in this investigation, the most relevant recommendations are proposed for a potential use of adhesively bonded anchorages for CFRP tendons in prestressing applications.
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Vasudevan, Satish. "AN INVESTIGATION OF QUASI-STATIC BEHAVIOR, HIGH CYCLE FATIGUE AND FINAL FRACTURE BEHAVIOR OFALUMINUM ALLOY 2024 AND ALUMINUM ALLOY 2219." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1193668130.
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Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2007."December, 2007." Title from electronic thesis title page (viewed 02/23/2008) Advisor, T. S. Srivatsan; Faculty readers, Craig Menzemer, Amit Prakash; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Wang, Peng. "Solid–shell finite elements for quasi-static and dynamic analysis of 3D thin structures : application to sheet metal forming processes." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0010/document.
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La simulation numérique par la méthode des éléments finis (MEF) fournit de nos jours une grande aide pour les ingénieurs dans les processus de conception d’optimisation des produits. Malgré le développement croissant des ressources de calcul, la fiabilité et l’efficacité des simulations numériques par la MEF restent à améliorer. Ce travail de thèse consiste à développer une famille d’éléments solide-coque (SHB) pour la modélisation tridimensionnelle des structures minces. Cette famille d’éléments SHB est basée sur une formulation tridimensionnelle en grands déplacements et rotations. La technique dite “d’intégration réduite dans le plan”, en utilisant un nombre arbitraire de points d’intégration dans la direction de l’épaisseur, permet la modélisation des structures minces avec une seule couche d'éléments. Dans ce travail de thèse, deux éléments linéaires SHB prismatique et hexaédrique, ainsi que leurs contreparties quadratiques, ont été implantés dans le code par éléments finis ABAQUS pour l’analyse quasi-statique et dynamique des structures minces. La performance de ces éléments a été validée à travers une série de cas tests académiques, ainsi que sur des problèmes complexes de type impact/crash et des procédés de mise en forme de tôles minces. L'ensemble des résultats numériques obtenus révèle que les éléments SHB représentent une alternative intéressante aux éléments coques et solides traditionnels pour la modélisation tridimensionnelle des structures mincesNowadays, the finite element (FE) simulation provides great assistance to engineers in the design of products and optimization of manufacturing processes. Despite the growing development of computational resources, reliability and efficiency of the FE simulations remain the most important features. The current work contributes to the development of a family of assumed strain based solid-shell elements (SHB), for the modeling of 3D thin structures. Based on reduced integration and special treatments to eliminate locking effects and to control spurious zero-energy modes, the SHB solid‒shell elements are capable of modeling most thin 3D structural problems with only a single element layer, while describing accurately the various through-thickness phenomena. In the current contribution, a family of prismatic and hexahedral SHB elements with their linear and quadratic versions have been implemented into ABAQUS using both standard/quasi-static and explicit/dynamic solvers. The performance of the SHB elements is evaluated via a series of popular benchmarks as well as with impact/crash and sheet metal forming processes. All numerical results reveal that the SHB elements represent an interesting alternative to traditional shell and solid elements for the 3D modeling of thin structural problems
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Radeva, Zheni Verfasser], and Evangelos [Gutachter] [Tsotsas. "Analysis and simulation of the deformation behavior at quasi-static compressive stressing of bonded model pellets / Zheni Radeva ; Gutachter: Evangelos Tsotsas." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2019. http://d-nb.info/1219965871/34.
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López, Claudio David. "Shortening time-series power flow simulations for cost-benefit analysis of LV network operation with PV feed-in." Thesis, Uppsala universitet, Elektricitetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-242099.
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Time-series power flow simulations are consecutive power flow calculations on each time step of a set of load and generation profiles that represent the time horizon under which a network needs to be analyzed. These simulations are one of the fundamental tools to carry out cost-benefit analyses of grid planing and operation strategies in the presence of distributed energy resources, unfortunately, their execution time is quite substantial. In the specific case of cost-benefit analyses the execution time of time-series power flow simulations can easily become excessive, as typical time horizons are in the order of a year and different scenarios need to be compared, which results in time-series simulations that require a rather large number of individual power flow calculations. It is often the case that only a set of aggregated simulation outputs is required for assessing grid operation costs, examples of which are total network losses, power exchange through MV/LV substation transformers, and total power provision from PV generators. Exploring alternatives to running time-series power flow simulations with complete input data that can produce approximations of the required results with a level of accuracy that is suitable for cost-benefit analyses but that require less time to compute can thus be beneficial. This thesis explores and compares different methods for shortening time-series power flow simulations based on reducing the amount of input data and thus the required number of individual power flow calculations, and focuses its attention on two of them: one consists in reducing the time resolution of the input profiles through downsampling while the other consists in finding similar time steps in the input profiles through vector quantization and simulating them only once. The results show that considerable execution time reductions and sufficiently accurate results can be obtained with both methods, but vector quantization requires much less data to produce the same level of accuracy as downsampling. Vector quantization delivers a far superior trade-off between data reduction, time savings, and accuracy when the simulations consider voltage control or when more than one simulation with the same input data is required, as in such cases the data reduction process can be carried out only once. One disadvantage of this method is that it does not reproduce peak values in the result profiles with accuracy, which is due to the way downsampling disregards certain time steps in the input profiles and to the averaging effect vector quantization has on the them. This disadvantage makes the simulations shortened through these methods less precise, for example, for detecting voltage violations.
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Habte, Haileleoul Sahle. "Modélisation par éléments finis de structures tubulaires métalliques comme composites écrasées axialement sous des régimes de charge quasi-statiques et dynamiques utilisées comme systèmes d’absorption d'énergie." Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1022.
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Actuellement, nous pouvons trouver beaucoup de moyens de transport de différentes formes et quantités pour satisfaire la forte demande de mobilité humaine et de transport de marchandises. Et, ce moyen de transport peut être considéré comme l'un des piliers de l'efficacité de l'homme dans l'accomplissement de ses tâches. Ces produits d'ingénierie, pendant la période de service, peuvent rencontrer une collision inattendue avec des objets non identifié ou l'un à l'autre. Chacun de ces événements causerait des dommages catastrophiques au produit et aux humains. En tant que tels, ces produits doivent intégrer des composants en tant qu'outils de sécurité, et l'application des systèmes de dissipation d'énergie vient à cet égard.Ce travail s'est concentré sur une modélisation numérique de systèmes innovants de dissipation d'énergie non conventionnels développés et testés expérimentalement dans (Abdul-Latif et al, 2017) pour améliorer leur capacité d'absorption d'énergie. Le concept de base utilisait le flambement plastique axial de l'acier doux circulaire droit comme les tubes composites avec divers motifs cémentés. Un tel traitement thermique a été appliqué sur 15% de la surface extérieure avec une profondeur de 0,5 mm. Dans ce travail, une modélisation non linéaire par éléments finis a été réalisée décrivant la réponse de ces tubes en ciblant particulièrement leur comportement le long de l'épaisseur du tube.Le logiciel de simulation ABAQUS 6.14 a été utilisé pour l'analyse du flambement plastique des tubes en raison de la charge quasi statique et dynamique. D'où l'objectif de développer une plate-forme de conception commune. L'analyse non linéaire par éléments finis a d'abord été effectuée sur le tube conventionnel, puis sur les tubes non conventionnels. Les tubes non conventionnels, quatre modèles cémentés de 2, 3, 4 et 5 anneaux et deux autres modèles de 2 et 3 bandes verticales ont été modélisés et simulés.Pour l'élément de coque représentant un tube mince, un élément de coque S4R de 1 mm de diamètre a été utilisé afin d'obtenir une convergence de maille précise. Outre le matériau "tel que reçu" utilisé pour les tubes conventionnels, les comportements des matériaux durs et mous ont été modélisés pour les tubes non conventionnels. Pour la modélisation des matériaux, on a opté pour des matières plastiques élastiques avec trempe sous contrainte et effet de vitesse de déformation en fonction des différentes conditions de charge.Les résultats de simulation de tubes conventionnels et non conventionnels sur les processus de déformation et la courbe de déplacement de la charge ont été examinés et comparés aux résultats expérimentaux. Les résultats ont été assez semblables. De plus, les résultats de la charge moyenne d'affaissement, de l'absorption d'énergie et de l'efficacité de la charge d'écrasement ont été examinés. Une erreur maximale de 11,2 centiles a été enregistrée par 4R sous flambement dynamique dans toutes les études.En outre, une plate-forme de conception numérique avec plusieurs nouveaux modèles cémentés a été proposée. Ces propositions se composent d'une famille de nouvelles zones de 6R et 4V, d'une mixte de zones 3R3V, 3R4V et 4R4V , et d'une matrice de zones 9R_WH,12R_HW, 12R_HW,12C et 9C. Parmi ces derniers, les modèles 3R3V ont montré de meilleures capacités d'absorption d'énergie, en simulation de flambement quasi statique et dynamique, que les autres, même pour ceux observés expérimentalement. En face, le gain d'absorption d'énergie pour 3R3V a été enregistré à 42% par des simulations quasi-statiques et à 18,7% par des simulations dynamiques. Outre l'adoption d'une longueur de course d'essai différente de 50 mm et 40 mm pour la simulation quasi statique et dynamique, respectivement, un grand écart en percentile peut être augmenté en raison de la nécessité d'utiliser une équation constitutive complexe pour le comportement dur et mou en fonction du taux de déformationCurrently, we can find many of transportation means of different forms and quantity to satisfy the high demand of human’s mobility and goods transportation. And, this transportation means can be considered as one of the pillars for human to do their tasks efficiently, and by large an important development tool for a country. These engineered products, during the service period, may encounter unexpected crush/collusion with foreign object or one to another. Each of these events would make catastrophic damage to product and harm to human. As such these products need to integrate components as safety tool, and application of energy dissipating systems comes to this front.This work focused on a numerical modeling of innovative non-conventional energy dissipating systems developed and tested experimentally in (Abdul-Latif et al, 2017) to enhance their energy absorption capacity. The basic concept utilized the axial plastic buckling of right-circular mild steel like composite tubes with various case-hardened patterns. Such a heat treatment has been applied on 15% of the outer surface with a depth of 0.5 mm. In this work, a nonlinear finite element modeling was conducted describing the response of such tubes targeting particularly their behavior along the tube thickness.Simulation software ABAQUS 6.14 was used the analysis the tubes plastic buckling due quasi-static and dynamic load. Parameters used in the non-linear finite element analysis were kept identical. Hence, a target of developing a common design platform (numerical simulation procedures) attained.The nonlinear finite element analysis was done first on the conventional tube and followed by non-conventional tubes. The non-conventional tubes, four case-hardened patterns of 2, 3, 4 and 5 rings and two other patterns of 2 and 3 vertical strips were modeled and simulated.For shell element representing a thin-tube, S4R shell element of 1 mm size was used looking for an accurate mesh convergence. Apart from the “as-received” material used for conventional tube, material behaviors for hard and soft were modeled for non-conventional tube. Elastic-plastic with strain hardening and strain-rate effect were adopted for material modeling respect to the different loading rate conditions. A surface interaction with normal pressure and a dry friction was highlighted by the contact between the tube surface-to-surface and the tube-to-rigid bodies. Initial geometry imperfection was integrated to initially trigger and mitigate the deformations.Simulation results of conventional and non-conventional tubes on deformation processes and load-displacement curve were examined and compared to experimental findings. Results were fairly matched. More, results of mean collapse load, energy absorption and crush load efficiency were reviewed. A maximum of 11.2 percentile error was recorded by 4R under dynamic buckling among all studies.Moreover, a numerical design platform with several new case-hardened patterns was proposed. These proposals compose a family of new ring and vertical strip case-hardened zones (6R, 4V), a mixed ring and vertical strip case-hardened zones (3R3V, 3R4V, 4R4V), and a matrix of rectangular or circular case-harden zones (9R_WH, 12R_HW, 12R_WH, 12C, 9C). Among the latter, patterns 3R3V showed better energy absorption capacities, in both quasi-static and dynamic buckling simulation, than the others even for those observed experimentally. In face the energy absorption gain for 3R3V was recorded 42% by quasi-static and 18.7% for dynamic simulations. Apart from adopting different test stroke length of 50mm and 40mm for quasi-static and dynamic simulation, respectively, a big percentile gap may be raised due to a need for using complex constitutive equation for hard and soft with strain rate dependent behavior
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Bastos, Camila Bianka Silva. "Estudo dos impactos de um sistema fotovoltaico conectado à rede elétrica utilizando análises QSTS." Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/2081.
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This dissertation presents a study of the operation of two different three-phase grid-connected test-grids with the connection of a 1MWp photovoltaic system. Two analysis methods are used to evaluate the impacts of this photovoltaic systeM, these methods being conventional static analysis and the analysis known as Quasi-Static Time-Series Analysis. Despite the fact that all grids have unique characteristics, it is important to use test-grids, which simulate the real grid characteristics, to analyze the kinds of problems that can occur and then look for alternatives, if necessary. The impacts evaluated are related to the system losses, minimized with the allocation study of the generation on the grid, voltage profile and tap position curve, when automatic load tap changers are used. It was verified that the photovoltaic system interconnection point is the most influenced one after its connection to the grid. The Quasi-Static Time-Series Analysis allow the correct evaluation of the load-generation interaction, running the time series power flow through estimated data for the load and irradiance curves during 168 hours. The conventional static analysis only considers critical operation conditions, like minimum and maximum load, and no generation or maximum generation, and does not evaluate different case scenarios that occur in reality. The photovoltaic systems can bring many advantages to the electric systems, like the improvement on the final consumer voltage profile, line losses reduction, and also environmental impacts reduction. However, with the increase of distributed photovoltaic generation on the electrical grid, it s necessary to be aware of the impacts that this may cause by performing interconnection studies.
Esta dissertação apresenta um estudo da operação de uma rede teste trifásica de média tensão com a interligação de um sistema fotovoltaico de 1,0 MWp. Dois métodos de análise são utilizados para avaliar os impactos deste sistema fotovoltaico, sendo estes métodos as análises estáticas convencionais eas análises conhecidas como Quasi-Static Time-Series Analysis. Apesar de cada rede elétrica apresentar características únicas, é importante a utilização de sistemas testes, que simulam as características de sistemas reais, para analisar que tipos problemas podem surgir e então buscar alternativas, se necessário. Os impactos avaliados se referem às perdas no sistema, minimizadas com a correta alocação da geração, perfil de tensão e curva de posição do tap, no caso de transformador com comutação automática de tap. Contata-se que o ponto de conexão do sistema fotovoltaico é o mais influenciado pela sua conexão à rede. As análises QSTS possibilitam avaliar corretamente a iteração entre carga e geração, efetuando o fluxo de potência consecutivo através de dados estimados para as curvas de carga e de irradiância solar ao longo de 168 horas. Já as análises convencionais consideram apenas condições críticas de operação, como por exemplo, carga leve ou nominal e geração nula ou máxima, não avaliando então diferentes cenários de operação que ocorrem na prática. Os sistemas fotovoltaicos podem trazer muitos benefícios aos sistemas elétricos, como melhoria do perfil de tensão de atendimento ao consumidor, redução de perdas nas linhas, além da redução nos impactos ambientais. Entretanto, com o aumento de geração fotovoltaica distribuída na rede, é necessário estar atento aos impactos que isto pode causar através de estudos de interconexão.
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Lora, Ruben, and Jayesh Namjoshi. "Simulation of Residual Stresses in Castings." Thesis, Jönköping University, JTH, Mechanical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-1587.
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This work presents a study and implementation of the simulation of residual stresses in castings. The objects of study are a cast iron truck Hub part (provided by the company Volvo 3P) and an optimized version of the Hub resulting from the application of a topology optimization process. The models are solved through an uncoupled thermo-mechanical solidification analysis, performed both in the FE commercial software Abaqus and the FD commercial software Magmasoft and the results are compared. First, a thermal analysis is carried out where the casting is cooled down from a super-heated temperature to room temperature. The thermal history obtained, is then used as an external force to calculate the residual stresses by means of a quasi-static mechanical analysis, using a J2-plasticity model. The simulation procedures are explained through a simplified model of the Hub and then applied to the geometries of interest. A results comparison between the original Hub and its optimized version is also presented. The theoretical base is given in this work as well as detailed implementation procedures. The results shows that the part subjected to the topology optimization process develop less residual stresses than its original version.
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Lorong, Philippe. "Sur une approche parallèle pour le calcul des structures : comportement sur calculateurs parallèles." Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0015.
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Cette thèse a pour support une méthode de décomposition de domaine ayant pour cadre le calcul des structures en quasi statique, les matériaux ayant éventuellement un comportement non linéaire. Cette méthode comporte une double originalité. Elle présente le problème à étudier comme étant un assemblage d'entités, toutes mécaniques, les sous-structures et les interfaces, et elle utilise une approche à grand incrément de temps pour construire un algorithme itératif de résolution. Les développements réalisés, dans cette thèse, portent sur une première mise en œuvre numérique et informatique dans le cadre de l'élasticité. Le premier chapitre commence par présenter l'approche dans un cadre général. Le comportement des sous-structures et des interfaces y est détaillé. L'application à l'élasticité est ensuite aborde; des éléments de convergence sont donnes dans ce cadre. Le second chapitre, outre la présentation des choix effectues lors de la mise en œuvre numérique (mise en œuvre basée sur une approche éléments finis), propose une étude du comportement itératif de la méthode en fonction de divers paramètres présents. Une comparaison, en nombre d'opérations sur des réels avec une méthode de type Crout y est donnée. Enfin, le troisième chapitre détaille l'adaptabilité informatique de l'approche sur différentes classes de calculateurs parallèles existants: des calculateurs mimd (alliant fx8 et alliant 2800, ipsc d'Intel, ncube) et un calculateur simd (connection machine cm2)
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Ramli, Khairun N. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods. Development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.
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The main objective of this research is to model and analyse complex electromagnetic problems
by means of a new hybridised computational technique combining the frequency domain
Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded
Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the
ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric
materials irradiated by geometrically intricate sources. The Method of Moments modelling
employed a two-dimensional electric surface patch integral formulation solved by independent
linear basis function methods in the circumferential and axial directions of the antenna wires. A
similar orthogonal basis function is used on the end surface and appropriate attachments with
the wire surface are employed to satisfy the requirements of current continuity. The surface
current distributions on structures which may include closely spaced parallel wires, such as
dipoles, loops and helical antennas are computed. The results are found to be stable and showed
good agreement with less comprehensive earlier work by others.
The work also investigated the interaction between overhead high voltage transmission lines and
underground utility pipelines using the FDTD technique for the whole structure, combined with
a subgridding method at points of interest, particularly the pipeline. The induced fields above
the pipeline are investigated and analysed.
FDTD is based on the solution of Maxwell¿s equations in differential form. It is very useful for
modelling complex, inhomogeneous structures. Problems arise when open-region geometries
are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to
circumvent this difficulty. The establishment of edge elements has greatly improved the
performance of this method and the computational burden due to huge numbers of time steps, in
the order of tens of millions, has been eased to tens of thousands by employing quasi-static
methods.
This thesis also illustrates the principle of the equivalent surface boundary employed close to
the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid
techniques due to their ability to analyse a system of multiple discrete regions by employing the
principle of equivalent sources to excite the coupling surfaces. The method has been applied for
modelling human body interaction with a short range RFID antenna to investigate and analyse
the near field and far field radiation pattern for which the cumulative distribution function of
antenna radiation efficiency is presented. The field distributions of the simulated structures
show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of
the phenomena in the interaction between electromagnetic fields and human tissues.Ministry of Higher Education Malaysia and Universiti Tun Hussein Onn Malaysia (UTHM)
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Ramli, Khairun Nidzam. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods : development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.
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The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell's equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues.
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Kyrre, Anette Wester. "Quasi-static Analyses of Slender Structures with Complex Cross-Sections using Explicit FEM Codes." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23661.
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It has previously been done analyses to find global stiffness values of an umbilical cable, with mixed results or no results at all when subjected to bending. There have also been difficulties in finding a distinct stick-slip point during bending. In this thesis, several models have been examined to get a step closer to resolve these particular issues. To begin with, a very simple flexible cable has been tested to see if the program ANSYS LS-Dyna can provide good global stiffness values, then of course with the use of an explicit scheme. When this first analysis gave good results, it was possible to conclude that the program could handle analyzing long slender structures with good accuracy. Further it was also developed a model with the aim of predicting the stick-slip phenomenon during bending. Results from this model could imply that there existed a stick-slip point, only a short time after the bending started. Finally, a last model was developed, including two armour layers wound around a cover of polyethylene. Other analyses have had problems with the behavior of the tendons during bending, that is they have been spreading, and not been following a loxodromic curve. Different cable lengths were tested, showing relative good results for the axial- and bending stiffness, but not so good results for the torsional stiffness. In addition to be able to develop models that could give realistic global stiffness values, focus have been on reducing the CPU time as much as possible. Therefore, much time has been spent on modeling the models right, and choosing the right path and length of loading.
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Tataie, Laila. "Méthodes simplifiées basées sur une approche quasi-statique pour l’évaluation de la vulnérabilité des ouvrages soumis à des excitations sismiques." Thesis, Lyon, INSA, 2011. http://www.theses.fr/2011ISAL0123/document.
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Dans le cadre de la protection du bâti face au risque sismique, les techniques d’analyse simplifiées, basées sur des calculs quasi-statiques en poussée progressive, se sont fortement développées au cours des deux dernières décennies. Le travail de thèse a pour objectif d’optimiser une stratégie d’analyse simplifiée proposée par Chopra et al. (2001) et adoptée par les normes américaines FEMA 273. Il s’agit d’une analyse modale non linéaire découplée, dénommée par les auteurs UMRHA qui se caractérisent principalement par : des calculs de type pushover selon les modes de vibration dominants de la structure, la création de modèles à un degré de liberté non linéaire à partir des courbes de pushover, puis le calcul de la réponse temporelle de la structure en recombinant les réponses temporelles associées à chaque mode de vibration. Dans ce travail, la méthode UMRHA a été améliorée en investiguant les points suivants. Tout d’abord, plusieurs modèles à un degré de liberté non linéaire déduits des courbes de pushover modal sont proposés afin d’enrichir la méthode UMRHA originelle qui emploie un simple modèle élasto-plastique : autres modèles élasto-plastiques avec des courbes enveloppes différentes, le modèle de Takeda prenant en compte un comportement hystérétique propre aux structures sous séismes, et enfin, un modèle simplifié basé sur la dégradation de fréquence en fonction d’un indicateur de dommage. Ce dernier modèle à un degré de liberté privilégie la vision de la chute de fréquence au cours du processus d’endommagement de la structure par rapport à une description réaliste des boucles d’hystérésis. La réponse totale de la structure est obtenue en sommant les contributions non linéaires des modes dominants aux contributions linéaires des modes non dominants. Enfin, la dégradation des déformées modales, due à l’endommagement subi par la structure au cours de la sollicitation sismique, est prise en compte dans la méthode M-UMRHA proposée dans ce travail, en généralisant le concept précédent de dégradation des fréquences modales en fonction d’un indicateur de dommage : la déformée modale devient elle-aussi dépendante d’un indicateur de dommage, le déplacement maximum en tête de l’ouvrage ; l’évolution de la déformée modale en fonction de cet indicateur est directement identifiée à partir des calculs de pushover modal. La pertinence de la nouvelle méthode M-UMRHA est investiguée pour plusieurs types de structures, en adoptant des modélisations éprouvées dans le cadre de la simulation des structures sous séismes : portique en béton armé modélisé par des éléments multifibres pour le béton et les armatures, remplissage en maçonnerie avec des éléments barres diagonales résistant uniquement en compression, bâti existant contreventé (Hôtel de Ville de Grenoble) avec des approches coques multicouches. Les résultats obtenus par la méthode simplifiée proposée sont comparés aux résultats de référence issus de l'analyse temporelle non linéaire dynamiqueIn the context of building’s protection against seismic risk, simplified analysis techniques, based on quasi-static analysis of pushover, have strongly developed over the past two decades. The thesis aims to optimize a simplified method proposed by Chopra and Goel in 2001 and adopted by American standards FEMA 273. This method is a nonlinear decoupled modal analysis, called by the authors UMRHA (Uncoupled Modal for Response History Analysis) which is mainly characterized by: pushover modal analysis according to the dominant modes of vibration of the structure, setting up nonlinear single degree of freedom systems drawn from modal pushover curves, then determining the history response of the structure by combining of the temporal responses associated with each mode of vibration. The decoupling of nonlinear history responses associated with each mode is the strong assumption of the method UMRHA. In this study, the UMRHA method has been improved by investigating the following points. First of all, several nonlinear single degree of freedom systems drawn from modal pushover curves are proposed to enrich the original UMRHA method, in which a simple elastic-plastic model is used, other elastic-plastic models with different envelope curves, Takeda model taking into account an hysteretic behavior characteristic of structures under earthquakes, and finally, a simplified model based on the frequency degradation as a function of a damage index. The latter nonlinear single degree of freedom model privileges the view of the frequency degradation during the structure damage process relative to a realistic description of hysteresis loops. The total response of the structure is obtained by summing the contributions of the non linear dominant modes to those of linear non dominant modes. Finally, the degradation of the modal shapes due to the structure damage during the seismic loading is taken into account in the new simplified method M-UMRHA (Modified UMRHA) proposed in this study. By generalizing the previous model of frequency degradation as a function of a damage index: the modal shape becomes itself also dependent on a damage index, the maximum displacement at the top of the structure; the evolution of the modal shape as a function of this index is directly obtained from the modal pushover analysis. The pertinence of the new method M-UMRHA is investigated for several types of structures, by adopting tested models of structures simulation under earthquakes: reinforced concrete frame modeled by multifibre elements with uniaxial laws under cyclic loading for concrete and steel, infill masonry wall with diagonal bars elements resistant only in compression, existing building (Grenoble City Hall) with multilayer shell elements and nonlinear biaxial laws based on the concept of smeared and fixed cracks. The obtained results by the proposed simplified method are compared to the reference results derived from the nonlinear response history analysis
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Jamil, A. "Structural response of novel PU structures under quasi-static, impact and blast loading : experimental and numerical analyses." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3018626/.
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Lagresle, Charly. "Analyse du processus d’usure abrasive et optimisation d’engrenage aéronautique." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI113.
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Les organes de transmission de puissance par engrenages sont couramment utilisés dans de nombreux domaines, parmi lesquels celui de l'aéronautique. Le système étudié dans ces travaux de thèse est un réducteur d'hélicoptère. Son rôle est de transmettre la puissance générée par le turbomoteur à la boîte de transmission principale, tout en adaptant la vitesse de rotation au besoin de cette dernière. Pour maximiser la puissance massique des systèmes, les engrenages aéronautiques peuvent être dotés de voiles minces, réduisant la masse de l'ensemble, mais favorisant aussi leurs flexibilités. Très sollicités en termes de nombre de rotations et de conditions de fonctionnement, ces engrenages à voile mince du réducteur présentent un risque d’apparition de surpressions locales et sont d'autant plus susceptibles d’être soumis à un certain nombre d'avaries, telles que l'usure abrasive, le grippage ou encore le micro-écaillage. Le premier objectif de ces travaux de thèse est la compréhension et la simulation du processus d'usure abrasive sur les engrenages. Ce processus d'arrachement de matière sur le flanc des dentures est simulé par l'intermédiaire de la loi d'Archard adaptée aux contacts lubrifiés. Lors des différentes phases de vol (décollage, atterrissage, etc.), les conditions de fonctionnement évoluent et modifient les paramètres quasi-statiques de l’engrènement, la lubrification du système et par conséquent la quantité de matière arrachée. Afin de prendre en considération les évolutions des conditions de fonctionnement dans le processus d'usure, une méthodologie de cumul de l'usure a été adoptée et adaptée aux besoins de la simulation. Il est alors possible d'étudier la cinétique et l'intensité de l'usure sur les différentes phases de vol afin d'en déterminer les plus sévères. Le second objectif fait écho au premier. Après avoir cerné la problématique de l'usure, l'optimisation des paramètres quasi-statiques de l'engrenage à voile mince est mise en place. Cette optimisation, basée sur la recherche d'une micro-géométrie idéale, a pour vocation de réduire les causes potentielles de ces avaries, notamment les surpressions de contact ou le facteur de grippage d'Almen. Le problème étant qualifié de complexe, un algorithme MO-TRIBES d'optimisation multivariables et multicritères est déployé. De nombreux exemples d'optimisation sont proposés afin d'améliorer le comportement de cet engrenage à voile mince : réduction des fluctuations des signaux d'erreur de transmission sous-charge, des pressions maximales de contact, des facteurs de grippage, en simple et en multi-objectifs. Le choix des corrections de denture et de leur forme est aussi abordé. Finalement, grâce à ce module d'optimisation, il est possible de réduire l'arrachement de matière afin d'allonger la durée de vie de l'engrenagePowers transmissions are commonly used in many areas, including aeronautics. The studied system in this thesis is a helicopter gearbox. Its purpose is to transmit the power generated by the turbine engine to the main gearbox and to adapt the rotational speed of the input shaft. Aeronautical gears are light weight in order to maximize the power to weight ratio of the system. With thin rims, the mass of the system is reduced but its flexibility is increased. These types of gears, subjected to large number of revolutions and severe operating conditions, are more likely to be exposed to failures such as abrasive wear, scoring or micro-pitting. The first objective of this PhD thesis is the understanding and the simulation of the abrasive wear process for spur and helical gears. The material removal calculation is based on the well-known Archard equation, adapted to lubricated contacts. During the different phases of flight (take-off, landing, hover flight), the specific working conditions change. Consequently, the quasi-static gearing behaviour, the lubrication and therefore the quantity of wear need to be adapted. To this end, a new methodology is proposed to accumulate wear depths over several and different working conditions. This methodology makes it possible to analyze the kinetics and the intensity of the abrasive wear process and deduce the most severe phases of flight. The second goal echoes the first one. Following the identification of the problem of abrasive wear, a multi-objective optimization of the quasi-static behaviour of the thin rimmed gear is proposed. The goal of this optimization, based on the search of optimal tooth modifications, is to reduce potential sources of gear failures, in particular localized overpressures on tooth flanks or the Almen factor governing scuffing. Due to the complexity of the problem, a meta-heuristic multi-variable optimization algorithm (MO-TRIBES) is introduced. Multiple mono- and multi-objective gear optimization examples are provided in order to improve the quasi-static behaviour of the aeronautical gear : minimization of fluctuations of the transmission error under load, reduction of the maximal contact pressures, decrease of the scuffing risk factors. The ideal type of tooth modifications is discussed. Finally, by using the optimization module, the amount of wear is significantly reduced and a comfortable lifetime extension for the studied gear is provided
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Vieux-Champagne, Florent. "Analyse de la vulnérabilité sismique des structures à ossature en bois avec remplissage : essais expérimentaux - modélisation numérique - calculs parasismiques." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI085/document.
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Les séismes constituent une source d’aléas importante pour l’étude de la vulnérabilité d’unbâtiment. Le comportement parasismique des bâtiments à ossatures en bois est particulièrementintéressant. Deux familles de structure à ossature en bois peuvent être distinguées : les ossaturesutilisant les produits industriels que sont les panneaux en bois reconstitué servant à contreventerla structure et les connecteurs métalliques, et les ossatures traditionnelles avec remplissage reposantsur des techniques de construction anciennes et dépendantes du contexte local. L’efficacitédu comportement parasismique des bâtiments à ossature en bois traditionnels avec remplissagereste encore peu reconnue en raison du manque de résultats issus des travaux de recherche.Les travaux présentés dans cette thèse visent ainsi à améliorer les connaissances sur le comportementparasismique de cette typologie constructive. Partant de l’hypothèse selon laquellece comportement est gouverné par la réponse des assemblages par connecteurs métalliques, uneapproche multi-échelles, couplant études expérimentales et études numériques est développée.Elle détaille l’analyse à l’échelle 1 de la connexion, en passant par l’échelle 2 des cellules élémentaires,constitutives des murs, par l’échelle 3 des murs de contreventement pour se finaliserà l’échelle 4 du bâtiment dans son ensemble.Sur le plan expérimental, cette approche permet d’une part, de réaliser des études paramétriqueset ainsi d’appréhender l’influence de la réponse de chaque élément (bois, clous, feuillard,remplissage, contreventement, ouvertures) sur le comportement local (échelles 1 et 2) et global(échelles 3 et 4) de la structure. D’autre part, elle permet de fournir une base de données pourla validation des modélisations numériques aux différentes échelles.Sur le plan de la modélisation numérique, cette approche multi-échelles est fondée sur la priseen compte du comportement non-linéaire hystérétique des assemblages à l’échelle supérieure, parl’intermédiaire d’un macro-élément, développé dans la cadre de la méthode des éléments finis.Ainsi, grâce à une modélisation simplifiée (assemblage des macro-éléments), le calcul est rapide,aussi bien à l’échelle du mur qu’à celle du bâtiment, et intègre les phénomènes non-linéaire locaux.Le modèle peut ainsi prédire de manière relativement précise le comportement dynamique de lastructure complète à l’échelle 4, testée sur table vibrante.L’étude présentée dans ce manuscrit fait partie des travaux précurseurs relatifs à l’analysede la vulnérabilité sismique des ossatures bois avec remplissage. Cette étude débouche sur denombreuses perspectives pour l’analyse de cette typologie constructive. Elle confirme que les bâtimentsà ossatures en bois avec remplissage ont un comportement parasismique très performantThe seismic vulnerabilty is an important issue in the design of a building. The seismicresistant behavior of timber-framed structures is particularly relevant. Two types of timberframedstructures can be distinguished : the timber-framed structures using industrial products,such as wood-products panels used to brace the structure or metal fasteners, and traditionaltimber-framed structures included infill made of natuarl materials (earth or stones masonry).The seismic resistant behavior efficiency of traditional structures remains poorly recognizedbecause of the lack of research results on this kind of construction.Therefore, the thesis aims at improving the seismic behavior knowledge of timber-framedmasonry. Based on the assumption that their behavior is driven by the response of the metalfasteners connections, a multi-scale approach is proposed. It couples experimental and numericalstudies. At the scale 1 of the connection, at the scale 2 of the elementary constitutive cell ofwalls, at the scale 3 of structural elements such as shear walls and finally at the scale 4 of theentire building.In regards to the experimental work, this method allows, on the one hand, to perform parametricstudies and to analyze the influence of each element (wood member, nails, steel strip,infill, bracing, openings) on the local behavior (scales 1 and 2) and on the global behavior(scales 3 and 4) of the structure. On the other hand, it allows to provide a database to validatethe numerical modeling at each scale.In regards to the numerical work, this multi-scale approach allows to take into account thehysteretic behavior of joints in the development of a macro-element at the scale 2. Thus, thanksto a simplified finite element modeling (macro-element assembly), the computational cost islimited and it allows to take into account the local phenomena. The model is able to predictrelatively accurately the dynamic behavior at the scale 4 of the building, tested on a shakingtable.The study, presented herein, is one of the pioneer work that deals with the analysis of theseismic vulnerability of timber-framed structures with infill panels. This study provides outlookfor the analysis of this type of buildings. It confirms that the timbered masonry structures havea relevant seismic resistant behavior
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Do, Ngoc Anh. "Numerical analyses of segmental tunnel lining under static and dynamic loads." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0042/document.
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Cette thèse vise à étudier le comportement de revêtement articulé du tunnel en développant une nouvelle approche numérique à la Méthode de Réaction Hyperstatique (HRM) et la production des modèles numériques en deux dimensions et trois dimensions à l'aide de la méthode des différences finies (FDM). L'étude a été traitée d'abord sous charges statiques, puis effectuée sous charges dynamiques. Tout d'abord, une étude bibliographique a été effectuée. Une nouvelle approche numérique appliquée à la méthode HRM a ensuite été développée. En même temps, un modèle numérique en deux dimensions est programmé sur les conditions de charge statique dans le but d'évaluer l'influence des joints, en termes de la distribution et des caractéristiques des joints, sur le comportement du revêtement articulé de tunnel. Après cela, des modèles complets en trois dimensions d'un seul tunnel, de deux tunnels horizontaux et de deux tunnels empilés, dans lesquels le système des joints est simulé, ont été développés. Ces modèles en trois dimensions permettent d'étudier le comportement non seulement du revêtement du tunnel, mais encore le déplacement du sol entourant le tunnel lors de l’excavation. Un modèle numérique en trois dimensions simplifié a ensuite été réalisé afin de valider la nouvelle approche numérique appliquée à la méthode HRM.Dans la dernière partie de ce mémoire, la performance du revêtement articulé du tunnel sous chargements dynamiques est prise en compte par l’analyse quasi-statique et dynamique complète en utilisant le modèle numérique en deux dimensions (FDM). Un modèle HRM a également été développé prenant en compte des charges quasi-statiques. Les différences de comportement de tunnel sous chargements statiques et sismiques sont mises en évidence et expliquéesThis PhD thesis has the aim to study the behaviour of segmental tunnel lining by developing a new numerical approach to the Hyperstatic Reaction Method (HRM) and producing two-dimensional (2D) and three-dimensional (3D) numerical models using the finite difference method (FDM). The study first deals with under static loads, and then performs under dynamic loads. Firstly, a literature review has been conducted. A new numerical approach applied to the HRM has then been developed. At the same time, a 2D numerical model is programmed regarding static loading conditions in order to evaluate the influence of the segmental joints, in terms of both joint distribution and joint stiffness characteristics, on the tunnel lining behaviour. After that, full 3D models of a single tunnel, twin horizontal tunnels and twin tunnels stacked over each other, excavated in close proximity in which the joint pattern is simulated, have been developed. These 3D models allow one to investigate the behaviour of not only the tunnel lining but also the displacement of the ground surrounding the tunnel during the tunnel excavation. A simplified 3D numerical model has then been produced in order to validate the new numerical approach applied to the HRM. In the last part of the manuscript, the performance of the segmental tunnel lining exposed to dynamic loading is taken into consideration through quasi-static and full dynamic analyses using 2D numerical models (FDM). A new HRM model has also been developed considering quasi-static loads. The differences of the tunnel behaviour under static and seismic loadings are highlighted
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WENG, YU-GING, and 翁餘慶. "Quasi-static analysis of planar wave-guides." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/24755540558034872371.
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Yeh, Yu-chi, and 葉育祺. "Quasi-static Analysis of Non-uniform Transmission Lines." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/55578028375281781834.
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邱建文. "Quasi-static analysis of coplanar waveguide passive structures." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/59400902378636444429.
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"Quasi-static Acoustic Tweezing for Small Volume Blood Coagulation Analysis." Tulane University, 2019.
Find full textAbstract:
archives@tulane.eduThe activation of the coagulation cascade at artificial surfaces of container walls leads to inherent variability and unreliability in predicting bleeding or thrombosis risks. Large number of false results and a lack of standardization have caused concern in the medical community about the usefulness of photo-optical plasma coagulation tests such as PT/aPTT as well as whole blood viscoelastic methods. We have developed an integrated photo-optical / viscoelastic method for noncontact blood coagulation analysis. In this approach, referred to as “integrated quasi-static acoustic tweezing thromboelastometry” (i-QATT), temporal changes in blood elasticity and turbidity during coagulation are assessed from a single drop of blood levitating in air. i-QATT provides comprehensive information about blood coagulation including reaction time, kinetics of fibrin formation and cross-linking, clot firmness, fibrinolysis, and functional level of coagulation factors. This work demonstrates the ability of this method to rapidly and reliably measure the coagulation factor deficiency, functional levels of fibrinogen and factor XIII, platelet function, heparin dose response as well as identify bleeding / thrombotic risks in human subjects. i-QATT has been successfully used to detect the hypercoagulable state in smoking subjects.
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Daishen Luo
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Wei-GengPeng and 彭唯耕. "Quasi-static Analysis and Dynamic Analysis for a Single Nut Ball Screw." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/zr66fx.
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Chiang, Ming-Yuan, and 江名芫. "Modelling and Analysis of Quasi-Static Multiphysics Simulation for CMOS-MEMS." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/cc5qtt.
Full textAbstract:
碩士國立彰化師範大學
機電工程學系
106
In the study, we take the active thermal sensor chip in vacuum environment as the research object, and establish a quasi-static multiphysics simulation model. We report a newly hybrid simulation to find out the characteristic length based on heat transfer theory. This quasi-static multiphysics simulation model is used as building blocks to numerically simulate the behavior of various types of MEMS sensors. Experiments are presented as a verification program to examine the simulation accuracy. The results corrected by the trend equation show that the error between simulation and experiment is not more than 5%, and this result proves that this method has good accuracy and reliability. Through the simplified model and CAE software, the numerical values of each physical parameter in the model are calculated. Discrete mathematical methods are used to solve various practical problems, avoid complex simulation and data analysis. CAE tools will be used to initially analyze the feasibility of the design and solve the problems encountered in component design, development, and improvement.
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Juang, Shueen-Hong, and 莊舜弘. "Three-Dimensional Quasi-Static Finite Element Analysis of a Normal Foot." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/62227769999304787946.
Full textAbstract:
碩士中原大學
醫學工程研究所
89
The purpose of this study was to develop a three-dimensional finite element model of a normal left foot which comprising most joints of the foot. The validity of this model was verified by comparing analysis results with experimentally measured joint contact pressures, plantar normal pressures and plantar shear stresses. The geometry of the left foot was acquired from a 24 year male without any foot pathology by computed tomography scan. The outer contours of the bone and soft tissue were determined by an automatic contouring program, and used to generate the solid models by a CAD program (SolidWorks 99). The 4-node tetrahedral models were created and analyzed using a CAE program (Mentat 2000 and MARC 2000). The material properties were assumed to be linear elastic. A quasi-static loading scheme was employed. All nodes on the upper cross-sectional area of the shank were constrained, and a rigid plane under the foot or footwear was moving towards the foot by using 12 displacement increment control from 0 to 12 mm at 1 mm interval. The reaction forces on the constrained nodes were recovered at each increment. The joint contact pressures obtained from the finite element analysis were found to be much lower than the experimentally measured results. This is due to the fact that the larger contact areas assumed in the finite element model. The plantar normal pressures and plantar shear stresses were compared with experimentally measured results from literature and similar trends and pressure ranges were found. When wearing flat insole or total contact insole, the plantar pressure at the heel region can be reduced 61.39% and 90.71%, respectively. The current study proposed a validated three-dimensional foot model which can be modified to simulate other foot conditions in the future. This foot model can be useful in observing stress distributions inside the foot, and in designing footwear, and the investigation of other biomechanical behavior of the foot subjected to different ambulatory movements.
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Yung-Chang, Sze, and 施永昌. "Quasi-Static Analysis of Asymmetric Coupled Transmission Lines by Boundary Element Method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/70484110720701154274.
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碩士大同工學院
電機工程研究所
81
A modified boundary element method in the application of quasi- TEM analysis of microstrip coupled lines is The analytic results are then used to design the forward and backward directional coupler. Applying the coupled-mode lation of microstrip coupled lines, the directional coupler be treated as a four port network and the circuit parameters can easily be obtained. In this thesis, investigation is mainly made on the asymmetric coupled microstrip lines. The mutual inductance capacitance coupling coefficients are the two main parameters which determine the directivity of the coupler. Through our study, a new structure is presented with an aim to provide directivity. The structure is referred to an enclosed one, height of the enclosure is equal to twice the dielectric ness. It is investigated that this structure can compose an backward- coupling directional coupler so long as all four are well matched (characteristically terminated).
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Lu-TingYu and 余律廷. "RMVT-based Finite Annular Prism Methods for the Quasi-3D Static Analysis of Two-directional Functionally Graded Circular Plates." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/sn68yq.
Full textAbstract:
碩士國立成功大學
土木工程學系
107
A weak-form formulation of finite annular prism methods (FAPM) based on the Reissner’s mixed variational theorem (RMVT), is developed for the quasi three-dimensional (3D) static analysis of two-directional functionally graded (FG) circular plates. The material properties of the circular plate are assumed to obey either a two-directional power-law distribution of the volume fractions of the constituents through the radial-thickness surface or an exponential function distribution varying doubly exponentially through it. These FAPM solutions of FG circular plates are in excellent agreement with the solutions obtained available in the literature.
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Lam, Hon-Fai, and 林漢輝. "The analysis of microstructure characteristics and mechanical properties of 35NCD16 alloy steel under quasi-static and dynamic compression loading conditions." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/20307735199540287489.
Full textAbstract:
碩士國立成功大學
機械工程研究所
81
The purpose of this thesis is to investigate the misro- structure characteristics and mechanical properties of (NF) 35NCD16 high strength alloy steel under quasi-static and dynamic compression loading conditions. At the same time, deformation constitutive equation is used to descibe the plastic deformation behaviour of material properties. Quasi- static mechanical tests adopt the SAGINOMIYA 100 tons forging machine for testing material at low strain rate from 10^-2 to 1 s^-1, and the strainrange from 10% to 80%. Fro dymanic tests, one dimensional elastic wave theory as analysis a basis and the Hopkinson bar tester device are used to invesgate the impact properties of present material at high strain rate from 10^2 to 5*10^3 s^-1 and a low defor- mation from 5% to 25%.Form the result of mechanical tests analysis, it is found that the flow stress increases with the rise of strain rate. The strain rate sensitivity and the activation volume are changed with the incresing of strain rate and strain. Therefore, the different strain rate regions for deformation mechanism can be distinguished. The material deformation is maniniy controlled by thermally activated mech- anism as the strain rate regions for deformation is mainly controlled by thermally activated mechanism as the strain rate less than 10^3 s^-1. If the strain rate is larger than 10^3 s^ -1, the thermally activated meshanism will transform to a dis- location drag mechanism. Microstructural evaluation are made by (OM) AND (SEM) for observing the metallographic structer and the fracture behaviour.Furthermore, with (STEM), microstructure of this material, such as dislocation desity and dislocation cells is analysed and observed.
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Hannawald, Frank [Verfasser]. "Zur physikalisch nichtlinearen Analyse von Verbund-Stabtragwerken unter quasi-statischer Langzeitbeanspruchung = On the physically nonlinear analysis of composite structures under quasi static long term loading / vorgelegt von Frank Hannawald." 2006. http://d-nb.info/980095859/34.
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Wilbert, Adrien. "On the crushing of honeycomb under axial compression." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2080.
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This thesis presents a comprehensive study of the compressive response of hexagonal honeycomb panels from the initial elastic regime to a fully crushed state. Expanded aluminum alloy honeycomb panels with a cell size of 0.375 in (9.53 mm), a relative density of 0.026, and a height of 0.625 in (15.9 mm) are laterally compressed quasi statically between rigid platens under displacement control. The cells buckle elastically and collapse at a higher stress due to inelastic action. Deformation then first localizes at mid-height and the cells crush by progressive formation of folds; associated with each fold family is a stress undulation. The response densifies when the whole panel height is consumed by folds. The buckling, collapse, and crushing events are simulated numerically using finite element models involving periodic domains of a single or several characteristic cells. The models idealize the microstructure as hexagonal, with double walls in one direction. The nonlinear behavior is initiated by elastic buckling while inelastic collapse that leads to the localization observed in the experiments occurs at a significantly higher load. The collapse stress is found to be mildly sensitive to various problem imperfections. For the particular honeycomb studied, the collapse stress is 67% higher than the buckling stress. It was also shown that all aspects of the compressive behavior can be reproduced numerically using periodic domains with a fine mesh capable of capturing the complexity of the folds. The calculated buckling stress is reduced when considering periodic square domains as the compatibility of the buckles between neighboring cells tends to make the structure more compliant. The mode consisting of three half waves is observed in every simulation but its amplitude is seen to be accented at the center of the domains. The calculated crushing response is shown to better resemble measured ones when a 4x4 cell domain is used, which is smoother and reproduces decays in the amplitude of load peaks. However, the average crushing stress can be captured with engineering accuracy even from a single cell domain.text
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GWO-SHYANG, HWANG, and 黃國祥. "QUASI-STATIC AND DYNAMIC ANALYSES OF RACKING DEFORMATION OF TUNNELS." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/22631448132281683530.
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(9226604), Amin Joodaky. "MECHANICS AND DESIGN OF POLYMERIC METAMATERIAL STRUCTURES FOR SHOCK ABSORPTION APPLICATIONS." Thesis, 2020.
Find full textAbstract:
This body of work examines analytical and numerical models to simulate the response of structures in shock absorption applications. Specifically, the work examines the prediction of cushion curves of polymer foams, and a topological examination of a $\chi$ shape unit cell found in architected mechanical elastomeric metamaterials. The $\chi$ unit cell exhibits the same effective stress-strain relationship as a closed cell polymer foam. Polymer foams are commonly used in the protective packaging of fragile products. Cushion curves are used within the packaging industry to characterize a foam's impact performance. These curves are two-dimensional representations of the deceleration of an impacting mass versus static stress. The main drawback with cushion curves is that they are currently generated from an exhaustive set of experimental test data. This work examines modeling the shock response using a continuous rod approximation with a given impact velocity in order to generate cushion curves without the need of extensive testing. In examining the $\chi$ unit cell, this work focuses on the effects of topological changes on constitutive behavior and shock absorbing performance. Particular emphasis is placed on developing models to predict the onset of regions of quasi-zero-modulus (QZM), the length of the QZM region and the cushion curve produced by impacting the unit cell. The unit cell's topology is reduced to examining a characteristic angle, defining the internal geometry with the cell, and examining the effects of changing this angle.
However, the characteristic angle cannot be increased without tradeoffs; the cell's effective constitutive behavior evolves from long regions to shortened regions of quasi-zero modulus. Finally, this work shows that the basic $\chi$ unit cell can be tessellated to produce a nearly equivalent force deflection relationship in two directions. The analysis and results in this work can be viewed as new framework in analyzing programmable elastomeric metamaterials that exhibit this type of nonlinear behavior for shock absorption.