Dissertations / Theses on the topic 'Linear FEM analyse'
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VIALE, NICOLA. "A new flat jack test for evaluating shear properties on unreinforced masonry." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2846617.
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Lofink, Paul [Verfasser], Wolfgang H. [Akademischer Betreuer] Müller, Wolfgang H. [Gutachter] Müller, and Nikolai D. [Gutachter] Tutyshkin. "FEM-gestützte Analyse der linear-elastischen und hyperelastischen eigengravitierenden Erde unter dem Aspekt geometrischer und physikalischer Nichtlinearitäten / Paul Lofink ; Gutachter: Wolfgang H. Müller, Nikolai D. Tutyshkin ; Betreuer: Wolfgang H. Müller." Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1156276659/34.
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Jakel, Roland. "Lineare und nichtlineare Analyse hochdynamischer Einschlagvorgänge mit Creo Simulate und Abaqus/Explicit." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171812.
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Der Vortrag beschreibt wie sich mittels der unterschiedlichen Berechnungsverfahren zur Lösung dynamischer Strukturpobleme der Einschlag eines idealisierten Bruchstücks in eine Schutzwand berechnen lässt. Dies wird mittels zweier kommerzieller FEM-Programme beschrieben: a.) Creo Simulate nutzt zur Lösung die Methode der modalen Superposition, d.h., es können nur lineare dynamische Systeme mit rein modaler Dämpfung berechnet werden. Kontakt zwischen zwei Bauteilen lässt sich damit nicht erfassen. Die unbekannte Kraft-Zeit-Funktion des Einschlagvorganges muss also geeignet abgeschätzt und als äußere Last auf die Schutzwand aufgebracht werden. Je dynamischer der Einschlagvorgang, desto eher wird der Gültigkeitsbereich des zugrunde liegenden linearen Modells verlassen. b.) Abaqus/Explicit nutzt ein direktes Zeitintegrationsverfahren zur schrittweisen Lösung der zugrunde liegenden Differentialgleichung, die keine tangentiale Steifigkeitsmatrix benötigt. Damit können sowohl Materialnichtlinearitäten als auch Kontakt geeignet erfasst und damit die Kraft-Zeit-Funktion des Einschlages ermittelt werden. Auch bei extrem hochdynamischen Vorgängen liefert diese Methode ein gutes Ergebnis. Es müssen dafür jedoch weit mehr Werkstoffdaten bekannt sein, um das nichtlineare elasto-plastische Materialverhalten mit Schädigungseffekten korrekt zu beschreiben. Die Schwierigkeiten der Werkstoffdatenbestimmung werden in den Grundlagen erläutertThe presentation describes how to analyze the impact of an idealized fragment into a stell protective panel with different dynamic analysis methods. Two different commercial Finite Element codes are used for this: a.) Creo Simulate: This code uses the method of modal superposition for analyzing the dynamic response of linear dynamic systems. Therefore, only modal damping and no contact can be used. The unknown force-vs.-time curve of the impact event cannot be computed, but must be assumed and applied as external force to the steel protective panel. As more dynamic the impact, as sooner the range of validity of the underlying linear model is left. b.) Abaqus/Explicit: This code uses a direct integration method for an incremental (step by step) solution of the underlying differential equation, which does not need a tangential stiffness matrix. In this way, matieral nonlinearities as well as contact can be obtained as one result of the FEM analysis. Even for extremely high-dynamic impacts, good results can be obtained. But, the nonlinear elasto-plastic material behavior with damage initiation and damage evolution must be characterized with a lot of effort. The principal difficulties of the material characterization are described
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Teklemariam, Daniel Mekonnen, and Bennie Hamunzala. "Design of Thick Concrete Beams : Using Non-Linear FEM." Thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189141.
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The experimental studies performed on the behaviour of very thick concrete beams subjected to static loads have revealed that the shear mechanisms play an important role in the overall response and failure behaviour. The aim of this thesis is to recommend suitable design methods for thick concrete beams subjected to off-centre static concentrated load according Eurocode 2 by using non-linear finite element analysis (NLFEA). To achieve this task, Abaqus/Explicit has been used by employing constitutive material models to capture the material non-linearity and stiffness degradation of concrete. Concrete damaged plasticity model and perfect plasticity model has been used for concrete and steel respectively. Three dilation angles (30º, 38º and 45º) and fracture energy from FIB 1990 (76 N/m) and FIB 2010 (142 N/m) has been used to investigate their influence on the finite element model. The dilation angle of 38º and FIB 2010 fracture energy was adopted as the suitable choice that reasonably matched with the experimental results. In verifying and calibrating the finite element model, the experimental results of the thick reinforced concrete beam conducted by the American Concrete Institute have been used. Three design approaches in the ultimate and serviceability limit state according to Eurocode 2 recommendations have been used namely; the beam method, strut and tie method and shell element method. Using the reinforcement detailing of the hand calculations of beam method and strut and tie method and linear finite element analysis of shell element method, non-linear finite element models have been pre-processed and analysed in Abaqus/Explicit. During the post-processing, the results have been interpreted and compared between the three design methods. The results under consideration are hand-calculated load at 0.3 mm crack width, FE-load at 0.3 mm crack width, amount of reinforcement and FE-failure load. The comparison of the results between the three design approaches (beam method, strut and tie method and shell element method) indicates that strut and tie method is better design approach, because it is relatively economic with regards to the quantity of reinforcement bars, has the higher load capacity and has a higher load at crack width of 0.3 mm crack width.De experimentella studier som utförts på tjocka betongbalkar som utsätts för statisk last har visat att skjuvning spelar en viktig roll i brottmekanismen. Syftet med detta examensarbete är att rekommendera lämpliga dimensioneringsmetoder för tjock betongbalkar utsatt for statisk koncentrerad last enligt Eurokod 2 med hjälp av ickelinjära finita element metod. Abaqus/Explicit användes genom att utnyttja konstitutiva materialmodeller för att fånga materialens icke-linjäritet och minskad styvhet. Tre dilatationsvinklar (30°, 38° och 45°) och två brottenergi från FIB 1990 (76 N/m) och FIB 2010 (142 N/m) tillämpas för att kontrollera deras inverkan på FE-modellerna. Dilatationsvinkel med 38° och FIB 2010 med högre brottenergi valdes i de icke-linjära finita elementanalyserna. Kontroll av FE-modellerna är baserad på ”American Concret Institutes” experimentella resultat på de tjocka betongbalkarna. Handberäkningar av tjocka betongbalkar har utförts i brott- och bruksgränstillstånd med tre dimensioneringsmetoder i Eurokod 2 nämligen balk metoden, fackverksmetoden och linjära-FE skalelementmetoden. Jämförelse har gjorts för de olika dimensioneringsmetoderna, genom att använda de armeringsdetaljer av handberäkningar i de verifierade och kalibrerade icke linjära FE-modellerna i Abaqus/Explicit. Resultaten i fråga är last för 0.3 mm handberäknad sprikvidd, FE-last för 0.3 mm sprikvidd, armeringsmängd och FE-brottlast. Jämförelse av resultaten mellan de tre dimensioneringsmetoder (balkmetod, fackverksmetod och skalelementmetod) visar att fackverksmetod är bättre design metod, eftersom det är relativt ekonomiskt med avseende på armeringsmängd, har högre lastkapacitet och last på 0.3 mm sprickvidd.
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Dettmann, Aaron. "Loosely coupled, modular framework for linear static aeroelastic analyses." Thesis, KTH, Lättkonstruktioner, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262047.
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A computational framework for linear static aeroelastic analyses is presented. The overall aeroelasticity model is applicable to conceptual aircraft design studies and other low-fidelity aero-structural analyses. A partitioned approach is used, i. e. separate solvers for aerodynamics and structure analyses are coupled in a suitable way, together forming a model for aeroelastic simulations. Aerodynamics are modelled using the vortexlattice method (VLM), a simple computational fluid dynamics (CFD) model based on potential flow. The structure is represented by a three-dimensional (3D) Euler-Bernoulli beam model in a finite element method (FEM) formulation. A particular focus was put on the modularity and loose coupling of aforementioned models. The core of the aeroelastic framework was abstracted, such that it does not depend on any specific details of the underlying aerodynamics and structure modules. The final aeroelasticity model constitutes independent software tools for the VLM and the beam FEM, as well as a framework enabling the aeroelastic coupling. These different tools have been developed as part of this thesis work. A wind tunnel experiment with a simple wing model is presented as a validation test case. An aero-structural analysis of a fully elastic unmanned aerial vehicle (UAV) (OptiMale) is described and results are compared with an existing higherfidelity study.Rapporten beskriver en beräkningsmodell för linjära, statisk aeroelastiska analyser. Modellen kan användas för konceptuella designstudier av flygplan. En partitionerad metod används, d v s separata lösare för aerodynamik- och strukturanalyser kopplas på ett lämpligt sätt, och bildar tillsammans en modell för aeroelastiska simulationer. Aerodynamik modelleras med hjälp av en så kallad vortex-lattice method (VLM), en enkel modell för beräkningsströmningsdynamik (CFD) som är baserad på friktionsfri strömning. Strukturen representeras av en tredimensionell (3D) Euler-Bernoulli-balkmodell implementerad med hjälp av en finita elementmetod (FEM). Ovannämnda modeller har utvecklats med fokus på modularitet och lös koppling. Kärnan i den aeroelastiska modellen har abstraherats så att den inte beror på specifika detaljer i de underliggande aerodynamik- och strukturmodulerna. Aeroelasticitetsmodellen i sin helhet består av separata mjukvaruprogram för VLM och balk-FEM, såväl som ett ramverk som möjliggör den aeroelastiska kopplingen. Dessa olika program har utvecklats som en del av examensarbetet. Ett vindtunnelförsök med en enkel vingmodell presenteras som ett valideringstest. Dessutom beskrivs en analys av ett elastiskt obemannad flygplan (OptiMale) och resultaten jämförs med en befintlig studie som har genomförts med modeller av högre trovärdighet.
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Denimal, Enora. "Prédiction des instabilités de frottement par méta-modélisation et approches fréquentielles : Application au crissement de frein automobile." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC039/document.
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Le crissement de frein est une nuisance sonore qui représente des coûts importants pour l'industrie automobile. Il tire son origine dans des phénomènes complexes à l'interface frottante entre les plaquettes de frein et le disque. L'analyse de stabilité reste aujourd'hui la méthode privilégiée dans l'industrie pour prédire la stabilité d'un système de frein malgré ses aspects sur- et sous-prédictifs.Afin de construire un système de frein robuste, il est nécessaire de trouver la technologie qui permette de limiter les instabilités malgré certains paramètres incertains présents dans le système. Ainsi, l'un des objectifs de la thèse est de développer une méthode permettant de traiter et de propager l'incertitude et la variabilité de certains paramètres dans le modèle éléments finis de frein avec des coûts numériques abordables.Dans un premier temps, l'influence d'un premier groupe de paramètres correspondant à des contacts internes au système a été étudiée afin de mieux comprendre les phénomènes physiques mis en jeu et leurs impacts sur le phénomène de crissement. Une approche basée sur l'utilisation d'un algorithme génétique a été également mise en place afin d'identifier le jeu de paramètres le plus défavorable en terme de propension au crissement sur le système.Dans un second temps, différentes méthodes de méta-modélisation ont été proposées afin de prédire la stabilité du système de frein en fonction de différents paramètres qui peuvent être des paramètres de conception ou des paramètres incertains liés à l'environnement du système.Dans un troisième temps, une méthode d'analyse non-linéaire complémentaire de l'analyse de stabilité a été proposée et développée. Elle se base sur le suivi de la stabilité d'une solution vibratoire approchée et permet d'identifier les modes instables présents dans la réponse dynamique du système. Cette méthode a été appliquée sur un modèle simple avant d'illustrer sa faisabilité sur le modèle éléments finis de frein completBrake squeal is a noise nuisance that represents significant costs for the automotive industry. It originates from complex phenomena at the frictional interface between the brake pads and the disc. The stability analysis remains the preferred method in the industry today to predict the stability of a brake system despite its over- and under-predictive aspects.In order to build a robust brake system, it is necessary to find the technology that limits instabilities despite some uncertain parameters present in the system. Thus, one of the main objectives of the PhD thesis is to develop a method to treat and propagate the uncertainty and variability of some parameters in the finite element brake model with reasonable numerical costs.First, the influence of a first group of parameters corresponding to contacts within the system was studied in order to better understand the physical phenomena involved and their impacts on the squealing phenomenon. An approach based on the use of a genetic algorithm has also been implemented to identify the most unfavourable set of parameters in terms of squeal propensity on the brake system.In a second step, different meta-modelling methods were proposed to predict the stability of the brake system with respect to different parameters that may be design parameters or uncertain parameters related to the environment of the brake system.In a third step, a non-linear analysis method complementary to the stability analysis was proposed and developed. It is based on the tracking of the stability of an approximate vibrational solution and allows the identification of unstable modes present in the dynamic response of the system. This method was applied to a simple academic model before demonstrating its feasibility on the complete industrial brake finite element model under study
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Makhlouf, Heba. "Essais virtuels pour l'industrie du meuble." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1164.
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Le travail s’inscrit dans le cadre d’une collaboration entre le Pôle Ameublement FCBA et le Laboratoire MSME de l’UPEM. L’objectif était de mettre au point un outil de simulation permettant à FCBA de mener une étude de validation (tenue aux tests normalisés) avant la fabrication du meuble. Ce travail était supporté par les fonds collectifs de la profession ameublement. Il a donné lieu à des développements dans le domaine de l’identification du comportement anisotrope du bois par analyse d’images couplée à la méthode des éléments finis, d’une approche multi-échelle pour identifier le comportement des liens entre éléments de meuble et d’un programme éléments finis utilisant l’approche « poutres » pour réaliser une étude statistique du comportement du meuble prenant en compte la dispersion du comportement du bois. Chaque étape a été validée expérimentalement. La simulation par éléments finis s’est focalisée sur une application « lits superposées en bois massif » pour laquelle un code à base de poutres a été développé dans l’environnement Matlab afin de pouvoir y implanter :• une théorie élastique anisotrope via des poutres de Timoshenko pour prendre en compte l’effet des déformations dues aux faibles rigidités transversales du bois en regard de la rigidité longitudinale ;• des éléments de connexion ponctuels représentant la contribution des composants de quincaillerie (vis, écrou noyé, tourillon…) et les effets locaux 3D aux liaisons entre poutres ;• la possibilité de prendre en compte les incertitudes sur les paramètres matériau d’une poutre à l’autre en fonction de l’orientation des planches, de la densité du bois etc… via une simulation de Monte-CarloThe work joins within the framework of a collaboration between the Pole Furnishing FCBA and the Laboratory MSME of the UPEM. The objective was to finalize(to work out) a tool of simulation allowing FCBA to lead a study of validation (held the normalized(standardized) tests) before the manufacturing of the piece of furniture
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Pablos, Rabano Alejandro. "Modeling of a PMSynRel stator with concentrated windings using FEM and non-linear reluctance networks." Thesis, KTH, Elektrisk energiomvandling, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124543.
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Permanent magnets synchronous reluctance (PMSynRel) motors are attractive due to their high torque density and because a lower quantity of permanent magnets is necessary in comparison with other permanent magnet machines. This thesis deals with the analysis of PMSynRel machines using a finite element method (FEM) and reluctance networks. First, a PMSynRel machine model is built in order to carry out simulations using a finite element method package. The effect of different design parameters such as the combination of the number of poles and slots, the number of flux barriers or the number of magnets can be studied since the implementation provides the possibility to change those variables. Next, a reluctance networks model, aimed to enable lower computation times than corresponding finite element models, is implemented for analysing the flux density distributions along the air gap of the machine disregarding the magnetic influence of the rotor. Finally, the results are compared with FEM simulations. It is concluded that the agreement reached is satisfactory in most of the cases analysed.
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Alagbada, Adefemi Samuel. "Thermo-Mechanical Fatigue Assessment of Marine Boiler : Using linear Finite Element Analyses." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-95439.
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This thesis is on fatigue crack growth assessments of a thermomechanical loaded Marine Boiler- Sunrod CPDB12. The installation position of the marine boiler in the ship in relation to its fatigue life under mode 1 loading is investigated. Thermomechanical loading embodies pressures, temperatures, RAO, subjected to the rigid body dynamic of ship in the marine environment. Linear elastic fracture mechanics (LEFM) method was used is predicting the growth rates of the welding flaws at the joint based on stress range of the Paris law relationship. FEA Numerical simulation delivered better crack growth rate assessments and life predictions of the smallest detectable flaws in the boiler. The identified smallest detestable flaws at the welding joint diminishing the designed safe life of the boiler significantly. Also, installation position within the ship do affect the fatigue life of the boiler.
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Selli, Nicola. "Static and seismic analysis of a historic masonry building in San Pio delle Camere." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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In February 2021, in San Pio delle Camere, on the Navelli plateau south-east of L'Aquila, a masonry building collapsed suddenly, after repair work had just begun on the damage caused by the 2009 earthquake. The current study, after a detailed examination of all the design documentation and the comparison of the post-earthquake damage with the results of the analysis on the model, finding an excellent correspondence, went to research the possible causes of the structural collapse, which occurred in static conditions. The masonry texture was then analysed, consisting of unworked natural stones of medium-small size bound by poor quality mortar, parameterising the mechanical characteristics with in situ tests, the Masonry Quality Index and the values proposed in NTC 2018. Then, the analysis of the global model lead to the verification of the complexity of the aggregate induced greater pressures, and consequent deformations, precisely in the walls from which the collapse originated. With these assumptions, and from the evidence of the presence of a modest void in an internal facing, the study of the local mechanism was deepened, arriving at the presumption of the possible minimum dimensions of such a cavity and how this, even if minimal, could have been the cause if concomitant with the degradation of the bonding mortar induced by the absence of maintenance and the loss of even minimal resistance capacities.
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Polidori, Andrea. "Analisi numerica non lineare di un nodo trave colonna in conglomerato cementizio." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2623/.
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Amin, Handren. "A comparative study of 2 CAD-integrated FE-programs using the linear static analysis." Thesis, Halmstad University, School of Business and Engineering (SET), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-2355.
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This Master’s thesis is summery of a comparative study of 2 commercial CAD-integrated
FE-programs. These FE-programs were CATIA v5 and ABAQUS 6.3-7. The primary
objective of this study is to investigate the basic FEA capabilities of CATIA and
ABAQUS 6.7-3 in performing the linear static analysis and to identify whether there are
any differences and similarities between results the both Finite Element FE codes give.
The overall research question in the present thesis is: Do different FE programs, here
CATIA and ABAQUS, give the same results for FE analysis giving the same models if
subjected to the same boundary conditions? This research seeks to achieve its aims
through making a comparative qualitative study. Certain pre-selections were performed in
advance of conducting Finite element analysis and the comparison process to ensure that
results would reflect only the most relevant and meaningful differences and similarities
between the both FE-codes. Five different 3D solid models have been selected to perform
linear static Finite element analysis on. All these models (case studies) are created in
CATIA V5 and the linear static analysis conducted on using FE-codes CATIA v5 and
ABAQUS 6.7-3. Three static responses (results) of the linear static analysis have been
adopted as criteria for comparisons purposes. These criteria were: (1) displacements, (2)
Von Mises stress, and (3) principal stress. The results of comparisons showed that there is
a very good agreement in most cases and small gap between in a few cases. Results of
this study demonstrate that the both FE-programs CATIA v5 and ABAQUS 6.7-3 have
good capabilities to perform FE-analysis and they give very near results. Reason behind
differences is that each of them uses a different algorithm for solving problems. The final
answer for the research question is given with valuable recommendations for future work
in the scope of this research.
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Desai, D. A. "Comparative non-linear simulation of temperature profiles induced in an exhaust manifold during cold-starting." Journal for New Generation Sciences, Vol 8, Issue 1: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/549.
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Published ArticleThe simulation of an exhaust manifold's thermal behaviour is an important concern for various reasons. Amongst them is the need to minimise catalyst light-offtime as significant exhaust emissions are generated within this period. Modelling such behaviour is not simplistic as it is governed by complex interactions between exhaust gas flow and the manifold itself. Computational fluid dynamics (CFD) is a powerful tool for such simulations. However its applicability for transient simulations is limited by high central processing unit (CPU) demands. The present study proposes an alternative computational method to assess and rank the relative impact of the manifold's thermal properties on its exterior temperature. The results show that stainless steel manifolds potentially minimise heat loss from the exhaust gas when compared with their cast iron counterparts. This may result in an increase in thermal energy being available to heat the catalyst.
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Yan, Charlotte. "Vaildation of nonlinear FE-simulation for design improvement." Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-114592.
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The aim of the project is to develop a model, which is going to be used for mass reduction of a standard profile of aluminium seat rails in Aircraft structure. Using nonlinear analysis including plasticity and material failure laws the effect of changes in geometry vs. ultimate load is analysed (ABAQUS 6.11). First, the non-linear model used is validated with experimental testing: Boundary conditions and material properties are adjusted based on load displacement curves, strain gauges information and failure patterns. Less than 1% deviation is achieved between simulation and testing. An inclusion of material imperfection led to a 5% improvement of the results. Using the validated algorithm, a mass reduction is performed via geometry variationZiel der Studie ist es ein adäquates Simulationsmodell zu entwickeln, welches zur Gewichtsreduzierung einer Standardprofil Aluminium Sitzschiene im Flugzeug verwendet werden kann. In einer nichtlinearen Analyse unter Berücksichtigung der Plastizität des Materials und von Materialfehlern wird die Auswirkung der Geometrieänderungen auf die maximale Traglast analysiert (ABAQUS 6.11). Zunächst wird das nicht-lineare Modell mit experimentell ermittelten Daten überprüft: Randbedingungen und Materialeigenschaften werden basierend auf Lastverschiebungskurven, Informationen von Dehnungsmessstreifen und Versagensmustern angepasst. Dabei wurden weniger als 1% Abweichung zwischen Simulation und Test erzielt. Die Berücksichtigung von Materialfehlern führte zu einer 5%-igen Verbesserung der Ergebnisse. Mit dem validierten Modell wird abschließend eine Gewichtsreduzierung mittels Geometrievariation durchgeführt
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Jonsson, Karl. "Two Problems in non-linear PDE’s with Phase Transitions." Licentiate thesis, KTH, Matematik (Avd.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223562.
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This thesis is in the field of non-linear partial differential equations (PDE), focusing on problems which show some type of phase-transition. A single phase Hele-Shaw flow models a Newtoninan fluid which is being injected in the space between two narrowly separated parallel planes. The time evolution of the space that the fluid occupies can be modelled by a semi-linear PDE. This is a problem within the field of free boundary problems. In the multi-phase problem we consider the time-evolution of a system of phases which interact according to the principle that the joint boundary which emerges when two phases meet is fixed for all future times. The problem is handled by introducing a parameterized equation which is regularized and penalized. The penalization is non-local in time and tracks the history of the system, penalizing the joint support of two different phases in space-time. The main result in the first paper is the existence theory of a weak solution to the parameterized equations in a Bochner space using the implicit function theorem. The family of solutions to the parameterized problem is uniformly bounded allowing us to extract a weakly convergent subsequence for the case when the penalization tends to infinity. The second problem deals with a parameterized highly oscillatory quasi-linear elliptic equation in divergence form. As the regularization parameter tends to zero the equation gets a jump in the conductivity which occur at the level set of a locally periodic function, the obstacle. As the oscillations in the problem data increases the solution to the equation experiences high frequency jumps in the conductivity, resulting in the corresponding solutions showing an effective global behaviour. The global behavior is related to the so called homogenized solution. We show that the parameterized equation has a weak solution in a Sobolev space and derive bounds on the solutions used in the analysis for the case when the regularization is lost. Surprisingly, the limiting problem in this case includes an extra term describing the interaction between the solution and the obstacle, not appearing in the case when obstacle is the zero level-set. The oscillatory nature of the problem makes standard numerical algorithms computationally expensive, since the global domain needs to be resolved on the micro scale. We develop a multi scale method for this problem based on the heterogeneous multiscale method (HMM) framework and using a finite element (FE) approach to capture the macroscopic variations of the solutions at a significantly lower cost. We numerically investigate the effect of the obstacle on the homogenized solution, finding empirical proof that certain choices of obstacles make the limiting problem have a form structurally different from that of the parameterized problem.QC 20180222
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Di, Fabrizio Vincenzo. "Modellazione e analisi non lineare del degrado artificiale di un prototipo di edificio in muratura in scala reale." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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La tesi pone l’attenzione sulla modellazione di un edificio in muratura da sottoporre a prove di laboratorio. In particolare, sono state eseguite analisi modali e non lineari per determinare l’influenza sugli elementi in muratura di alcune forme di degrado imposte, quali sovraccarichi, grado di ammorsamento della muratura, assenza di tiranti e cedimento differenziale della fondazione. I risultati ottenuti attraverso le analisi modali mostrano una notevole riduzione della rigidezza del sistema. Il cedimento differenziale imposto porta ad una concentrazione dello stato tensionale nelle fasce di piano in prossimità delle aperture.
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Singh, Subrat, and Shreedhara Sreehari Veditherakal. "CAE modelling of cast aluminium in automotive structures." Thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-162190.
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In the automobile industry, there is a big push for the automotive car manufacturers to base engineering decisions on the results of Computer Aided Engineering (CAE) solutions, and to transform the prototyping and testing, from a costly iterative process to a final verification and validation step. The variability in components material properties and environmental conditions together with the lack of knowledge about the underlying physics of complex systems often make it impractical to make reliable predictions based on only deterministic CAE models. One such area is the CAE modelling of cast aluminium components. These cast aluminium components have gained a huge relevance in the automobile industries due to their commendable mechanical properties. The advantage of the cast aluminium alloys are being a well-established alloy system in manufacturing processes, their functional integrity and relatively low weight. However, the presence of pores and micro-voids obtained during the manufacturing process constitutes a specific material behaviour and establishes a challenge in modelling of the cast materials. Furthermore, the low ductility of the materialdemands for the advanced numerical model to predict the failure. The main focus of this master thesis work is to investigate modelling technique of a cast aluminium alloy component, a spring tower, for a drop tower test and validate the predicted behaviour with the physical test results. Volvo Car Corporation currently uses a material model provided by MATFEM for cast aluminium parts which are explored in this thesis work, to validate the material model for component level testing. The methodology used to achieve this objective was to develop a boundary condition to perform component level tests in the drop tower and to correlate these with the obtained results found by using various modelling techniques in the explicit solver LS-DYNA. Therefore, precise and realistic modelling of the drop tower is crucial because the simulation results can be influenced by major design changes. A detailed finite element model for the spring tower has been developed from the observations made during the physical testing. The refined model showed good agreement with the existing model for the spring tower and observations from physical tests.
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Ferrari, Rosalba (ORCID:0000-0002-3989-713X). "An elastoplastic finite element formulation for the structural analysis of Truss frames with application to ha historical iron arch bridge." Doctoral thesis, Università degli studi di Bergamo, 2013. http://hdl.handle.net/10446/28959.
Full textAbstract:
This doctoral thesis presents a structural analysis of the Paderno d’Adda Bridge, an impressive iron arch viaduct built in 1889 and located in Lombardia region (Italy).
The thesis falls in the context of a research activity started at University of Bergamo since 2005, that is still ongoing and aims to perform an evaluation of the present state of conservation of the bridge. In fact, the bridge is currently still in service and its important position in the context of transport network will soon lead to questions about its future destination, with particular attention to the evaluation of the residual performance capacity.
To this end, an inelastic structural analysis of the Paderno d’Adda bridge has been performed, up to failure. This analysis has been conducted through an autonomous computer code of a 3D frame structure that runs in the MATLAB environment and has been developed within the classical frame of Limit Analysis and Theory of Plasticity.
The algorithm has been developed applying the “exact” and stepwise holonomic step-by-step analysis method. It has shown very much able to track the limit structural behaviour of the bridge, by reaching convergence with smooth runs up to the true limit load and corresponding collapse displacements.
The main characteristic ingredients of its elastoplastic FEM formulation are: beam finite elements; perfectly plastic joints (as an extension of classical plastic hinges); piece-wise linear yield domains; “exact” time integration.
In the algorithm, the following original features have been implemented: treatment of mutual connections by static condensation and Gaussian elimination; determination of the tangent stiffness formulation through Gaussian elimination. These peculiar contributions are presented in detail in this thesis.
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Virgulto, Giorgio. "Valutazione delle potenzialità del BIM per analisi di loss assessment sismico." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Obiettivo del presente lavoro di Tesi sarà quello di integrare e semplificare la valutazione delle perdite sismiche in accordo con la normativa FEMA P-58 con la metodologia del Building Information Modeling. La FEMA P-58 è la normativa di riferimento per la valutazione delle perdite indotte su un edificio da un evento sismico (loss assessment) proponendo una metodologia in grado di quantificare le prestazioni dell’edificio in termini di vittime, costi di riparazione, tempi di riparazione e impatto ambientale. La metodologia BIM consente di generare un modello virtuale contenente le informazioni utili dell’edificio, relative all'intero ciclo di vita, dalla progettazione sino alla gestione. Dato che entrambe le tematiche sono recenti, il materiale presente in letteratura che affronta l’unione delle metodologie è scarso, ma ha fornito interessanti spunti per la scelta dei software e per integrare e completare tali studi. Per testare la fattibilità di integrazione tra la procedura BIM e la FEMA P-58, si è scelto come caso di studio un edificio in calcestruzzo armato. Il modello BIM è stato realizzato su Revit2019, quello strutturale su SAP2000 e quello prestazionale sismico su PACT. Per scambiare i dati tra i diversi software si è utilizzato un plugin che sfrutta i fogli di lavoro Excel. Sono descritti i parametri e i dati di input utilizzati per la modellazione. Inoltre, sono presentati i risultati forniti dal PACT e quelli implementati in Revit, in termini di stato di danno e di costi di riparazione. Nelle conclusioni sono evidenziati i vantaggi dell’impiego del BIM nelle fasi di modellazione, analisi prestazionale e visualizzazione dei risultati nella procedura di loss assessment. Infine, sono suggeriti possibili sviluppi futuri per migliorare ed integrare il presente lavoro di Tesi.
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Ptáček, Petr. "Termálně-strukturální analýza válce čtyřdobého spalovacího motoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254374.
Full textAbstract:
This diploma thesis is focused on creating a finite element method model of a four-stroke engine with a purpose to determine an impact on cylinder bore distortion caused by several types of loading. Introduction of this work covers research of possibilities in modelling thermal-structural analysis of cylinder liner and verifications of the analysis results. An Ansys model was further created and cylinder liner radial deformation caused by head bolts tightening and thermal loading coming from combustion was determined. Finally, a whole engine working cycle was simulated with a gas pressure loading and its final impact on the total cylinder liner radial deformation was defined.
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Lonzi, Giuditta. "La cupola del Duomo di Siena: ricerca storica, analisi costruttiva e modellazione strutturale tramite FEA finalizzate alla comprensione del comportamento statico." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16541/.
Full textAbstract:
Il centro storico di Siena, iscritto nella Lista Patrimonio Mondiale dell’UNESCO, è soggetto ad una forte contaminazione ambientale da cui deve essere necessariamente protetto e conservato in funzione del valore storico ed estetico che rappresenta. La vetustà del patrimonio architettonico comporta la necessità di uno studio approfondito del singolo edificio e la comprensione delle particolari tecniche costruttive antiche al fine di una corretta interpretazione del comportamento strutturale per l’elaborazione di efficaci strategie di prevenzione.
Questa tesi di laurea vuole approcciarsi nel suddetto modo per lo studio della cupola del Duomo di Siena, concentrandosi sulla calotta esterna in muratura, di più recente costruzione, ad opera dell’architetto Partini e risalente al 1892. Per cercare di individuare e interpretare un corretto comportamento della struttura si è proceduto iniziando dalla ricerca storica archivistica per poi passare all’analisi costruttiva dettagliata della calotta. Si è ritenuto maggiormente esaustivo affiancare all’analisi puramente logica del manufatto, una modellazione tridimensionale agli Elementi Finiti (FEM) tramite software, che hanno consentito di effettuare una esauriente analisi del comportamento statico dalla cupola e dell’interazione esistente fra le due calotte, interna ed esterna.
È indispensabile comprendere le vecchie tecniche costruttive, il modo di ragionare e agire sempre secondo criteri studiati, logici e motivati così è possibile dedurne un corretto comportamento e di conseguenza intervenire laddove siano state individuate le criticità con interventi di recupero e consolidamento.
La questione di fondamentale importanza a cui si vuole dare rilievo, consiste nello studiare e analizzare in maniera assolutamente obiettiva il passato senza lasciarsi vincolare dalle influenze del periodo moderno. È questa concezione moderna che spesso ci spinge ad assumere come certezze casi che in realtà nascondo significati ben più profondi.
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Pham, Anh Tu. "Détermination numérique des propriétés de résistance de roches argileuses." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1237/document.
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Les capacités de résistance de l'argilite Callovo-Oxfordian (COx), qui est une roche hôte potentielle pour le dépôt souterrain profond de déchets radioactifs de haute activité en France, sont étudiées. À une échelle microscopique, des micros pores peuvent être observés dans la matrice. Une première étape d'homogénéisation a été réalisée afin d'évaluer le critère de résistance de la matrice. L'analyse microstructurale de ce matériau à quelques centaines d'échelle, référencée échelle échelle mésoscopique, montre une matrice argileuse et une distribution aléatoire d'inclusions minérales (quartz et calcite).Dans le but de déterminer le domaine de résistance à l'argilite COx, un premier outil numérique a été développé dans le contexte du comportement élastoplastique de la matrice. Plusieurs modèles morphologiques du volume élémentaire représentatif ont été considérés, et soumis à un chargement incrémental dans des conditions périodiques jusqu'à la charge limite. A la suite de ce calcul élastoplastique, un point de la frontière du domaine de résistance est obtenu. Ce dernier est alors obtenu par des calculs élastoplastiques successifs.Une alternative aux simulations élastoplastique directes, des approches cinématiques et statiques du calcul à la rupture sont réalisées. Une méthode du type éléments finis basée sur la construction d'un champ de contrainte (dans l'approche statique) et d'un champ de vitesse (dans l'approche cinématique) est développé dans un outil numérique permettant de calculer une limite inférieure et une limite supérieure de domaine de résistanceThe strength capacities of Callovo-Oxfordian (COx) argillite which is a potential host rock for the deep underground repository of high-level radioactive waste in France are investigated. At a micro-scale, micro-pores can be observed in the matrix. A first strength homogenization step has been performed in order to evaluate the matrix strength criteria. The microstructure analysis of this material at some hundreds of micromet scale, referred at meso-scale, shows a clay matrix and a random distribution of mineral inclusions (quartz and calcite).Aiming to the determination of COx argillite strength domain, an FEM numerical tool has been developed in the context of the elastoplastic behavior of the matrix. Several morphological patterns of the representative elementary volume have been considered and subjected to an incremental loading in periodic conditions until collapse occurs. As a result of such elastoplastic calculation, one point of the boundary of the strength domain is obtained. The latter then could be reached by successive elastoplastic calculations.As an alternative to direct elastoplastic simulations, kinematic and static approaches of limit analysis are performed. The stress-based (static approach) and the velocity-based (kinematic approach) finite element method are used to develop a numerical tool able to derive a lower bound and upper bound of strength domain, respectively
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Jindra, Daniel. "Stanovení požární odolnosti konstrukcí." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392030.
Full textAbstract:
Possibilities of modeling non-linear behavior of concrete within standard room temperatures and increased fire-load values using FEM software ANSYS are studied. Temperature dependences of material models are considered. Fire resistance of reinforced concrete and concrete-steel composite construction is analyzed. Fire loads are defined in accordance with relevant standards. Non-linear structural transient analyses are calculated after temperatures were determined by transient thermal analyses. Results obtained from analyses of simple reinforced concrete structure are compared with approach of isotherm 500 °C method.
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Marchionni, Elianires. "Valutazione del rischio sismico di un edificio strategico destinato a sede della di.coma.c di Parma." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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Una delle principali prerogative nell’ambito della protezione civile è lo studio e l’analisi del rischio sismico. Non è possibile prevedere tali eventi né tanto meno evitare che si verifichino, tutto ciò che si può fare e garantire una sicurezza adeguata e ridurre considerevolmente il fattore di rischio.
La pianificazione dell’emergenza rappresenta una delle strategie principali per mitigare gli effetti di un evento sismico.
Il seguente lavoro svolge un analisi in ambito lineare dinamico e in ambito statico non lineare valutando le zone di criticità e gli indici di rischio sismico di un edificio intelaiato in c.a.
la modellazione dell'edificio ha previsto un analisi storico-critica dell'opera al fine di garantire un fattore di confidenza ed un livello di dettaglio tali da permettere un riscontro significativo sulle valutazioni desunte. L’edificio è stato progettato utilizzando come normativa di riferimento il Decreto del Ministro dei lavori Pubblici 16 gennaio 1996 “Norme tecniche per le costruzioni in zone sismiche”, assumendo come parametri di progetto un grado di sismicità S = 9 e un coefficiente di protezione sismica I = 1.4 (valido per le opere la cui resistenza al sisma è di importanza primaria per le necessità della protezione civile). Come precedentemente anticipato, l’edificio è già stato analizzato e sviluppato con un modello agli elementi finiti, la sua capacità sismica è stata valutata in ambito elastico lineare tramite un’analisi modale con spettro di risposta sia normativo proposto dalle NTC2008 che con spettro di risposta sismico locale realizzato ad hoc per l’edificio.
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Pavelka, Roman. "Hydraulické posunovače." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229740.
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This diploma thesis deals with the mechanical proposal of hydraulic puller. Furthermore, it includes the detail design solutions. The project also includes the calculation of the hydraulic puller parameters: maximum pushing force is 60 kN, speed of movement is 0.1 m s-1. This work also contains of stress analysis FEM with I-DEAS software. Following part deals with the design of hydraulic circuit for driving puller. At the end of work there are options for replacements of hydraulic puller by mechanical systems.
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Moro, Lorenzo. "Structure borne noise due to marine diesel engines: experimental study and numerical simulation for the prediction of the dynamic behaviour of resilient mounts." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11114.
Full textAbstract:
2013/2014Gli alti livelli di comfort che sono richiesti oggigiorno a bordo di navi da crociera e mega-yachts, portano i progettisti a concentrare la loro attenzione sul problema del rumore strutturale. I motori diesel quattro tempi che sono installati a bordo nave come motori principali o diesel generatori, sono tra le principali sorgenti di rumore strutturale. Per questa ragione, al fine di ridurre l’energia vibrazionale generata da queste sorgenti e trasmessa, tramite le strutture nave, ai locali alloggio, i motori diesel sono sospesi mediante elementi resilienti. Tali elementi resilienti disaccoppiano la sorgente di rumore e vibrazioni (motore diesel) dal mezzo di propagazione (le strutture nave) e isolano dunque la sorgente dalle strutture riceventi. I livelli di rumore strutturale misurati alle fondazioni del motore diesel dipendono dai livelli di velocità misurati sulla sorgente (cioè ai piedi del motore diesel), dai livelli di impedenza meccanica degli elementi resilienti e dai livelli di mobilità meccanica delle fondazioni del motore diesel. Il single-point approach è un approccio semplificato per la previsione dei livelli di rumore strutturale che trascura l’interazione tra elementi resilienti. Secondo tale teoria, al fine di ridurre il rumore strutturale trasmesso attraverso gli elementi resilienti alle strutture nave, si deve ridurre l’impedenza meccanica degli elementi resilienti così come la mobilità meccanica delle fondazioni del motore diesel. In altre parole, si devono aumentare la rigidezza dinamica degli elementi resilienti così come l’impedenza meccanica delle fondazioni del motore diesel. Ad oggi, l’impedenza meccanica degli elementi resilienti può essere ricavata solo mediante prove sperimentali in laboratorio, mentre la mobilità meccanica del motore diesel è solitamente misurata quando la nave è in costruzione. Dunque non vi è la possibilità di predire, in fase progettuale, il rumore strutturale dovuto ai motori diesel. In questa tesi, viene presentata una procedura per la simulazione del rumore strutturale dovuto a motori diesel marini. La procedura si basa su test sperimentali e simulazioni numeriche. Nella prima parte della tesi sono richiamate le basi teoriche necessarie per l’esecuzione delle procedure numeriche e delle prove sperimentali. Sono dunque presentati i risultati delle analisi numeriche per simulare la mobilità delle fondazioni dei motori diesel marini. I risultati delle analisi FEM sono stati validati mediante confronto dei risultati delle analisi numeriche con i dati ottenuti da una campagna di misure eseguite a bordo nave. Successivamente sono presentati i risultati di una serie di prove eseguite per collaudare una nuova macchina sperimentale per misurare l’impedenza meccanica degli elementi resilienti. Lo scopo del collaudo era definire una procedura per l’utilizzo della macchina e per l’esecuzione di prove sperimentali in accordo alla ISO 10846, che è considerata normativa di riferimento per questo tipo di prove. Si è dunque proceduto con l’esecuzione di prove sperimentali eseguite su un elemento resiliente per motori diesel marini. Le prove sono state eseguite a differenti carichi statici. I risultati di queste prove sperimentali sono stati utilizzati per settare un modello numerico che simuli il comportamento non-lineare del componente in gomma del resiliente. I risultati ottenuti sia dalle prove sperimentali sia dalle simulazioni numeriche sono stati utilizzati per predire il rumore strutturale generato dai motori diesel, in accordo al single-point approach. I risultati ottenuti dall’applicazione del metodo sono stati confrontati con misure eseguite a bordo e sono stati discussi per evidenziare vantaggi e svantaggi dell’applicazione del metodo. Le procedure numeriche per la simulazione del comportamento dinamico del resiliente e della fondazione costituiscono un primo passo per l’ottimizzazione del sistema di isolazione del motore diesel marino.
The high level of comfort that is required today on board cruise vessels and mega-yachts, leads the designers to focus their attention on structure-borne noise issues. Four-stroke diesel engines that are installed on board as main diesel engines for the propulsion system and as gen-sets, are usually the main sources of structure-borne noise. For this reason, the diesel engines are usually resiliently mounted in order to reduce the vibration energy generated by these sources and transmitted through the ship structures to the accommodation areas. These mounts decouple the noise and vibration source (diesel engine) from the means of wave propagation (ship structures) and so, they isolate the source from the receiving structures. The structure-borne noise levels measured at the diesel engine foundation depend on the velocity levels measured at the source (diesel engine feet), on the mechanical impedance levels of the resilient mounts and on the mechanical mobility levels of the diesel engine foundation. The simplified theory of the single-point approach neglects the interaction among the resilient mounts. According to this theory, to decrease the structure-borne noise transmitted through the resilient mounts towards the ship structures, the mechanical impedance of the resilient mounts as well as the mechanical mobility of the diesel engine foundation are to be lowered. In other words the dynamic stiffness of the resilient mounts has to be decreased and the mechanical impedance of the diesel engine foundation has to be increased. To date, the mechanical impedance of real resilient mounts can only be obtained by laboratory tests and the mechanical mobility of the diesel engine foundation is usually measured when the ship is under construction, so it is not available for predictive analyses. In the thesis, a procedure for simulating the structure-borne noise generated by marine diesel engine is discussed. The procedure is based on both experimental tests and numerical simulations. In the first part of the thesis, some notes on the theoretical background are presented. Then, the results of FE analyses for simulating the mechanical mobility of a diesel engine foundation are shown. The FE models have been validated by the results of a measurement campaign carried out on board a ship. Then, the results of a series of tests performed to tune a new test rig, designed and built up at the University of Trieste for measuring the mechanical impedance of resilient mounts, are discussed. The campaign for tuning the test rig has been carried out in order to set an experimental procedure that allows achieving results in compliance with the ISO 10846 Standard, which is a sound reference for this kind of tests. As a case study, a large resilient mount for marine diesel engines has been tested to achieve its mechanical impedance curve at different static pre-loads. The outcomes of the experimental tests have been used for tuning the best numerical model of the resilient mount that properly takes into account the nonlinear behaviour of the rubber core. The data of the experimental tests carried out on board ships as well as in laboratory and the outcomes of numerical simulations have been used to predict the structure-borne noise according to the single-point approach. The outcomes achieved by the application of the method have been compared with on board measurements and pros and cons of the method are widely discussed. Moreover, the numerical procedures for the simulation of the dynamic behaviour of the resilient mount and the diesel engine foundation, pave the way for the optimization of the decoupling system of marine diesel engines.
XXVII Ciclo
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Baldazzi, Michele. "Modello dinamico di un motore tubolare sincrono a magneti permanenti." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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L’attività di tesi ha riguardato la definizione di un modello dinamico per la rappresentazione del motore tubolare trifase sincrono a magneti permanenti che, in prima approssimazione, è solitamente considerato analogo a quello delle macchine rotanti.
Il suo ottenimento è stato raggiunto partendo da un modello matematico per un motore tubolare trifase a magneti permanenti generico. Successivamente, mediante l’utilizzo di FEMM, è stato possibile, con opportune simulazioni, caratterizzare il comportamento elettromagnetico di una macchina tubolare specifica e realistica, realizzata con opportuni script Lua.
Sono stati poi ricavati i dati e gli andamenti riguardanti i flussi concatenati e i coefficienti di auto e mutua induzione in funzione della posizione dello slider, che rappresentavano le nostre incognite all’interno del modello generale.
Una volta elaborati i dati con file Excel e opportune funzioni in Matlab si è potuto semplificare il modello matematico riadattandolo successivamente anche per il caso del controllo con tecnica ad orientamento di campo.
Inoltre è stata verificata la validità del modello anche per la macchina sincrona circolare trifase a magneti permanenti isotropa ed anisotropa.
Con quest’ultime è stato poi possibile effettuare un confronto mettendo in luce le differenze nella rappresentazione della macchina tubolare trifase sincrona a magneti permanenti con il nuovo modello specifico rispetto a quello per le macchine rotanti, mostrando la presenza di termini incrociati di disturbo.
In conclusione il modello ottenuto garantisce la possibilità di rappresentare in maniera precisa il nostro motore tubolare specifico garantendo notevoli vantaggi nel caso del controllo dell’azionamento dando la possibilità di compensare i termini di disturbo riscontrati rispetto all’utilizzo del modello per macchine rotanti.
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Pecorella, Daniele. "Methodology for the design and optimization of a morphing wing droop-nose structure for greener aircraft." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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Droop-Nose Leading Edge (DNLE) morphing wings are one of the most promising devices in order to achieve aerodynamic drag and noise reduction during take-off and landing phases. An accurate design of these structures could lead to the decrease of aircraft fuel consumption in the perspective of reaching a greener aviation, following the objectives indicated by Flightpath 2050 issued by the E.U. However, due to the challenges related to the realization of this technology and TRL reached, DNLE are more likely implemented in Unmanned Aerial Systems (UAS) for testing and evaluation purposes. In the present study, an optimization methodology for the DNLE composite laminate skin and morphing mechanism structure is proposed and applied to a study case represented by the UAS-S45 aircraft. The work starts from the morphing leading edge structure developed by the LARCASE laboratory at ETS Montreal. The results showed that by means of the optimization strategy adopted, the force required on the actuator mechanism is 88% lower than the original design. A significant improvement on the profile smoothness along its section and in the spanwise direction in morphing conditions has been obtained too. However, further investigations are still needed in order to achieve a more appropriate morphing shape. Despite this, it appears from the results obtained that the proposed methodology can be useful to tackle the DNLE design problem in an effective and efficient way. What developed in this work has been conceived to support the investigation of DNLE in the small leading edge profiles typical of the UAS. In this way, an easier procedure for the set up of the design flow, and a decrease in the computational effort for the optimization process can be obtained. An experimental validation of the results obtained is currently being performed at ETS, and future development regards the assessment of the errors of the numeric procedure herein presented respect to real data.
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Baldanza, Chiara. "Modellazione di dettaglio di un sistema innovativo di rinforzo esterno per il miglioramento sismico degli edifici senza interruzione d’uso." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20722/.
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Lo scopo della tesi è quello di ideare e validare un sistema innovativo di rinforzo esterno dei fabbricati basato sull’utilizzo di casseforme coibentanti in polistirene con armature metalliche integrate, getti di calcestruzzo e relativi sistemi di collegamento alle strutture portanti dell’edificio esistente.
Il vantaggio nell’utilizzo di queste tecnologie risiede principalmente nella possibilità di messa in opera del rinforzo per fasi successive senza una significativa interruzione d’uso della costruzione e con tempi di messa in opera relativamente ridotti.
In particolare, il tema della tesi riguarda la modellazione numerica di dettaglio a supporto della fase di sviluppo della tecnologia. Nell’elaborato si approfondisce il comportamento di un singolo modulo rappresentativo del rinforzo in modo tale da prevedere i possibili esiti delle sperimentazioni in laboratorio.
Lo studio del modulo comprende delle analisi statiche lineari, atte a individuare la geometria più efficiente, gli elementi strutturalmente rilevanti e la rigidezza del modulo in campo elastico. I risultati ottenuti servono inoltre da supporto e da controllo per le analisi statiche non lineari per materiale svolte successivamente che hanno lo scopo di individuare i meccanismi resistenti che si generano in campo plastico e le conseguenti riserve di resistenza del modulo. Infine, vengono effettuate delle analisi lineari di buckling tramite le quali si vuole valutare se il modulo può risentire di effetti del secondo ordine in campo elastico e come questi si possono manifestare.
Il sistema di miglioramento sismico Timesafe si presenta quindi come una soluzione molto versatile sia costruttivamente, in quanto applicabile indistintamente a strutture in muratura e in calcestruzzo armato, sia strutturalmente. Essa infatti, può essere concepita come una struttura di rinforzo puramente a telaio o come una struttura più complessa in cui considerare anche il contributo irrigidente della parete di completamento.
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Mussoni, Giacomo. "Progettazione di un sistema innovativo di rinforzo esterno per il miglioramento sismico degli edifici senza interruzione d’uso." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20757/.
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Il presente elaborato di tesi rientra nel progetto regionale TimeSafe,il quale prevede lo sviluppo di tecnologie integrate ed innovative a limitato impatto ed invasività per il miglioramento sismico di edifici senza interruzione d’uso.
In particolare, lo scopo dell’elaborato di tesi è quello di studiare l’interazione fra una struttura esistente e un sistema innovativo di rinforzo esterno basato sull'utilizzo di casseforme coibentanti in polistirene con armature metalliche integrate, elementi in calcestruzzo gettato e proiettato e relativi sistemi di collegamento.
Si vuole inoltre capire se è possibile progettare il sistema di rinforzo TimeSafe considerando come elementi sismo-resistenti nei confronti degli Stati Limite Ultimi (SLV e SLC) solamente traversi e pilastri o se è necessario modellare anche il contributo della parete di completamento per raggiungere il livello di sicurezza richiesto.
Pertanto, si studia in tal senso dapprima la vulnerabilità della struttura esistente nei confronti dell’azione sismica, quindi si valuta il miglioramento ottenibile applicando la tecnologia di rinforzo TimeSafe. In questa fase si effettuano diverse prove finalizzate a trovare la migliore soluzione di rinforzo dal punto di vista strutturale e costruttivo.
Parallelamente si intende definire un criterio di progetto fruibile anche in campo professionale attraverso cui effettuare il dimensionamento delle armature del sistema di rinforzo e le relative verifiche, in funzione sia della vulnerabilità sismica dell’edificio esistente sia del livello di sicurezza che si vuole raggiungere.
Lo studio comprende analisi in campo lineare della struttura pre e post-intervento, le quali permettono di valutare la vulnerabilità e fungono anche da supporto e controllo per le analisi successive svolte in campo non lineare. Queste ultime consentono di valutare sia come si modifica il meccanismo di collasso della struttura una volta inserito il rinforzo, sia come cambia la sua vulnerabilità.
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Suárez, Sergio Andrés Pardo. "Análise numérica de barras gerais 3D sob efeitos mecânicos de explosões e ondas de choque." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-07032017-103309/.
Full textAbstract:
O presente trabalho consiste no uso do Método dos Elementos Finitos (MEF) para a análise de interação fluido-estruturas de barras com foco em problemas transientes envolvendo explosões ou outras ações com propagação de ondas de choque. Para isso é necessário o estudo de três diferentes aspectos: a dinâmica das estruturas computacional, a dinâmica dos fluidos computacional e o problema do acoplamento. No caso da dinâmica das estruturas computacional deve-se identificar em função da cinemática de deformações, quais são os requisitos para que um elemento seja adequado para analisar tais problemas, tendo em vista que a formulação deve admitir grandes deslocamentos. Para evitar problemas relacionados com aproximações de rotações finitas, opta-se por empregar uma formulação descrita em termos de posições e que leva em consideração os efeitos de empenamento da seção transversal. No caso da dinâmica dos fluidos computacional, busca-se uma formulação para escoamentos compressíveis que seja estável e ao mesmo tempo sensível ao movimento da estrutura, sendo empregado um algoritmo de integração temporal explícito baseado em características com as equações governantes descritas na forma Lagrangeana-Euleriana Arbitrária (ALE). No que se refere ao acoplamento, busca-se modularidade e versatilidade, empregando-se um modelo particionado fraco (explícito) de acoplamento e técnicas de transferência das condições de contorno (Dirichlet-Neummann), sendo estudados os efeitos de utilizar transferência bidirecional ou unidirecional dessas condições de contorno.This work consists in the use of the Finite Element Method (FEM) for numerical analysis of fluid-bar structures, focusing on transient problems involving explosions or other actions with shock waves propagation. For this purpose, one needs to study three different aspects: the computational structural dynamics, the computational fluid dynamics and the coupling problem. Regarding computational structural dynamics, one need firstly to identify the requirements for an element to be adequate to analyze such problems, taking into account the fact that such element should admit large displacements. In order to avoid problems related to finite rotation approximations and to give a realist representation of a 3D bar structure, we chose a formulation defined in terms of positions and that considers the cross-section warping effects. Regarding computational fluid dynamics, we seek for a stable formulation for compressible flows, and at same time, sensitive to the movement of the structure, leading to an explicit time integration algorithm based on characteristics with governing equations described in the Arbitrary Lagrangian-Eulerian (ALE) form. Regarding to coupling, we chose to use a weak (explicit) partitioning coupling model in order to ensure modularity and versatility. The developed coupling scheme is bases on boundary conditions transfer techniques (Dirichlet-Neummann), and we study the effects of using bidirectional or unidirectional boundary conditions transfers.
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Bringmann, Philipp. "Adaptive least-squares finite element method with optimal convergence rates." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22350.
Full textAbstract:
Die Least-Squares Finite-Elemente-Methoden (LSFEMn) basieren auf der Minimierung des Least-Squares-Funktionals, das aus quadrierten Normen der Residuen eines Systems von partiellen Differentialgleichungen erster Ordnung besteht. Dieses Funktional liefert einen a posteriori Fehlerschätzer und ermöglicht die adaptive Verfeinerung des zugrundeliegenden Netzes. Aus zwei Gründen versagen die gängigen Methoden zum Beweis optimaler Konvergenzraten, wie sie in Carstensen, Feischl, Page und Praetorius (Comp. Math. Appl., 67(6), 2014) zusammengefasst werden. Erstens scheinen fehlende Vorfaktoren proportional zur Netzweite den Beweis einer schrittweisen Reduktion der Least-Squares-Schätzerterme zu verhindern. Zweitens kontrolliert das Least-Squares-Funktional den Fehler der Fluss- beziehungsweise Spannungsvariablen in der H(div)-Norm, wodurch ein Datenapproximationsfehler der rechten Seite f auftritt. Diese Schwierigkeiten führten zu einem zweifachen Paradigmenwechsel in der Konvergenzanalyse adaptiver LSFEMn in Carstensen und Park (SIAM J. Numer. Anal., 53(1), 2015) für das 2D-Poisson-Modellproblem mit Diskretisierung niedrigster Ordnung und homogenen Dirichlet-Randdaten. Ein neuartiger expliziter residuenbasierter Fehlerschätzer ermöglicht den Beweis der Reduktionseigenschaft. Durch separiertes Markieren im adaptiven Algorithmus wird zudem der Datenapproximationsfehler reduziert.
Die vorliegende Arbeit verallgemeinert diese Techniken auf die drei linearen Modellprobleme das Poisson-Problem, die Stokes-Gleichungen und das lineare Elastizitätsproblem. Die Axiome der Adaptivität mit separiertem Markieren nach Carstensen und Rabus (SIAM J. Numer. Anal., 55(6), 2017) werden in drei Raumdimensionen nachgewiesen. Die Analysis umfasst Diskretisierungen mit beliebigem Polynomgrad sowie inhomogene Dirichlet- und Neumann-Randbedingungen. Abschließend bestätigen numerische Experimente mit dem h-adaptiven Algorithmus die theoretisch bewiesenen optimalen Konvergenzraten.The least-squares finite element methods (LSFEMs) base on the minimisation of the least-squares functional consisting of the squared norms of the residuals of first-order systems of partial differential equations. This functional provides a reliable and efficient built-in a posteriori error estimator and allows for adaptive mesh-refinement. The established convergence analysis with rates for adaptive algorithms, as summarised in the axiomatic framework by Carstensen, Feischl, Page, and Praetorius (Comp. Math. Appl., 67(6), 2014), fails for two reasons. First, the least-squares estimator lacks prefactors in terms of the mesh-size, what seemingly prevents a reduction under mesh-refinement. Second, the first-order divergence LSFEMs measure the flux or stress errors in the H(div) norm and, thus, involve a data resolution error of the right-hand side f. These difficulties led to a twofold paradigm shift in the convergence analysis with rates for adaptive LSFEMs in Carstensen and Park (SIAM J. Numer. Anal., 53(1), 2015) for the lowest-order discretisation of the 2D Poisson model problem with homogeneous Dirichlet boundary conditions. Accordingly, some novel explicit residual-based a posteriori error estimator accomplishes the reduction property. Furthermore, a separate marking strategy in the adaptive algorithm ensures the sufficient data resolution. This thesis presents the generalisation of these techniques to three linear model problems, namely, the Poisson problem, the Stokes equations, and the linear elasticity problem. It verifies the axioms of adaptivity with separate marking by Carstensen and Rabus (SIAM J. Numer. Anal., 55(6), 2017) in three spatial dimensions. The analysis covers discretisations with arbitrary polynomial degree and inhomogeneous Dirichlet and Neumann boundary conditions. Numerical experiments confirm the theoretically proven optimal convergence rates of the h-adaptive algorithm.
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Larisch, Lukas. "Three-dimensional Modeling and Simulation of a Tuning Fork." Thesis, 2018. http://hdl.handle.net/10754/628716.
Full textAbstract:
The mathematical characterization of the sound of a musical instrument still follows Schumann’s laws [1]. According to this theory, the resonances of the instrument body, “the formants”, filter the oscillations of the sound generator (e.g., strings) and produce the characteristic “timbre” of an instrument. This is a strong simplification of the actual situation. It applies to a point source and does not distinguish between a loudspeaker and a three-dimensional instrument.
In this work we investigate Finite-Element-based numerical simulations of eigenfrequencies and eigenmodes of a tuning fork in order to capture the oscillation behavior of its eigenfrequencies. We model the tuning fork as an elastic solid body and solve an eigenvalue equation derived from a system of coupled equations from linear elasticity theory on an unstructured three-dimensional grid. The eigenvalue problem is solved using the preconditioned inverse iteration (PINVIT) method with an efficient geometric multigrid (GMG) preconditioner. The latter allows us to resolve the tuning fork with a high resolution grid, which is required to capture fine modes of the simulated eigenfrequencies. To verify our results, we compare them with measurement data obtained from an experimental modal analyses of a real reference tuning fork.
It turns out that our model is sufficient to capture the first eight eigenmodes of a reference tuning fork, whose identification and reproduction by simulation is novel to the knowledge of the author.
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Dediyagala, Nithila. "Optical Fibre Bragg Grating Analysis Through FEA and its Application to Pressure Sensing." Thesis, 2019. https://vuir.vu.edu.au/39484/.
Full textAbstract:
The focus of this thesis is developing optical fibre Bragg grating (FBG) pressure sensors with enhanced sensitivity for use in a low (gauge) pressure range (0 - 50 kPa) together with understanding observed non-linear behaviour. To appreciate the behaviour of FBG sensor spectra, it is necessary to understand geometrical and material properties of FBGs. The thesis is an in-depth investigation of the behaviour of FBGs including their manufacturing and fabrication process details. A new computational approach has been introduced to simulate FBG structures based on how the FBG fabrication process produces changes in refractive index.
There are various numerical analysis methods existing for analysing fibre Bragg grating structures and their spectral properties. Although computation design and simulations are used extensively in engineering problems, current computational approaches do not combine FBGs formation and their resultant spectra. In this study, this has been addressed by developing a simple Finite Element Analysis (2-D) model using the Wave Optics module in COMSOL Multiphysics simulation software. The 2-D model was developed considering the phase mask method commonly used to fabricate FBGs. It simulates a complex grating structure which is useful for manufacturers and researchers. The 2-D model then creates a unit cell of a grating structure which is able to be implemented within an optical fibre. The model allows users to decide the length of the grating by selecting the number of unit cells required. By changing the geometrical parameter of a unit cell of the 2-D phase mask structure, it was possible to demonstrate formation of complex grating structures. There have been many studies reported for ideal gratings; however, much less attention and research has been given to the spectra produced by these complex FBG structures. Therefore, this study specially focuses on complex grating structures and their spectral behaviour. The developed 2-D model successfully reproduced observed complex grating structures arising with the use of multiple phase masks orders, with theoretically acceptable results for the spectrum produced. Furthermore, the 2-D model of the phase-mask method was also able to produce tilted gratings by changing the incident angle of light on the phase mask. Therefore, this FEA approach provides insight into not only complex FBG structures but also tilted FBGs using a simple computational tool which will be useful in further research to understand the behaviour of a variety of FBG structures. For this study, material properties of standard single mode fibre (SMF-28) was considered. However, the model is able to simulate any optical fibre used in FBG fabrication by changing the material properties.
The thesis also considers the understanding of FBG pressure sensors and observed non-linear behaviour. Therefore, a thorough literature review was carried out to find the influence of structural and material properties of optical fibres and FBGs which is believed to be the cause of non-linear behaviour. It investigates in depth the birefringence effect on fibres due to point load and distributed load on FBGs using the Structural Mechanics and Wave Optics module in COMSOL software. Many research studies have employed a plane strain assumption for structural mechanics problems; however, they do not clearly explain the true nature of FBGs under stress generalized strain. This study overcomes that problem by introducing proper mathematical equations to develop 3-D behaviour in a 2-D computational model. The behaviour of a distributed load on FBGs was discussed in detail with the help of the computational model. It provides new information about an asymmetric peak produced as a result of birefringence effects.
The research proposes a new FBG uniform pressure sensor using a 2-D computational model. It was designed in simulation by adding a polymer material to the cladding of an SMF-28 by reducing the cladding diameter. In this study, polymers of PDMS and PTFE were chosen to further investigate the pressure enhancement in the suggested pressure range. The results show similar pressure sensitivity for both materials. Both materials are highly capable of enhancing pressure sensitivity in the range of 0 – 50 kPa. The suggested pressure range is most suitable for biomedical application. The positive results of the current study lend credibility for using the envisaged sensor for commercial use.
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Uplekar, Amruta Shrikant. "Structural characterization and analysis of the Castle of Arbeteta, Spain." Master's thesis, 2019. http://hdl.handle.net/1822/62322.
Full textAbstract:
Dissertação de mestrado em Structural Analysis of Monuments and Historical ConstructionThe Castle of Arbeteta, Guadalajara (Spain) is strategically located on top of the cliff rocks with a drawbridge as its only entrance. The castle has undergone various changes in over the time of centuries. It was once a two storey structure, of which only the ruins of the external walls exist. The castle is in a continuous state of degradation due to abandonment. Currently, there is an ongoing intervention project where a new use is going to be given to the castle. This will inevitably alter the current state of the existing structure. Preliminary inspection works and a detailed archaeological survey was carried out which specified the phases of construction of different sections of the castle. However, there is still need of a better characterization of the stone masonry walls and their structural behaviour. The main research question of the present thesis deals with the possible influence of the construction evolution of the castle on its structural behaviour. The thesis thus try to link two commonly separated and hermetic fields from the conservation projects: archaeological survey and structural analysis. For that matter, a non-destructive campaign consisting of indirect sonic tests and dynamic identification, which aimed at a thorough characterization of all the structural elements was planned. The campaign was carefully planned according to an archaeological research previously carried out. Secondly, a numerical model was made to analyse the structural behaviour of the castle, based upon photogrammetry model and the same archaeological survey. The experimental data collected through indirect sonic tests and dynamic identification was used to calibrate the model.. The results of the thesis show that indeed taking into account the archaeological findings improved our knowledge on the structural behaviour of the castle and has to be taken into account before carrying out a rigorous structural analysis.
O castelo de Arbeteta, em Guadalajara (Espanha) está estratégicamente situado no topo de um penhasco rocoso que tem uma ponte levadiça como unico acesso. O castelo tem sido submetido a muitos cambios e alterações estruturais durante estes séculos. Num momento da sua história, o castelo era uma estrutura de dois andares, dos que agora só as ruinas das paredes de alvenaria de pedra exteriores ainda existem. O castelo está agora num processo de degradação continuo devido ao seu abandono. No momento, existe um projeto de intervenção no castelo e um novo uso vai ser proposto no castelo. Esto vai alterar inevitavelmente o estado atual da estrutura existente. Inspeções preliminares do castelo e um levantamento arqueologico detalhado foram realizados e ajudaram a identificar as diferentes fases de construção nas diferentes partes do castelo. Contudo, uma melhor caracterização das paredes de alvenaria de pedras é necessária, para ajudar a compreender melhor o seu comportamento estrutural. Esta investigação estuda principalmente a possível influência da evolução estrutural do castelo no seu comportamento estrutural. A tese portanto trata de ligar dois campos necessários nos projetos de conservação que estão normalmente separados e muito compartimentados: o levantamento arqueologico e a análise estrutural. Com este objetivo, uma campaha de ensaios experimentais não destrutivos que incluiu ensaios sónicos indireitos e ensaios de identificação dinâmica foi planejada e destinada a caracterizar em detalhe todos os elementos estruturais do castelo. A campanha foi planejada cuidadosamente de acordo à investigação arqueologica previamente realizada. Numa segunda parte do trabalho, um modelo numerico foi preparado para analisar o comportamento estrutural do castelo, baseado no modelo fotogrametrico e no levantamento arqueologico. Os resultados experimentais recoletados dos ensaios sonicos e dinamicos foram usados para calibrar o modelo numérico. A tese mostra que, de fato, a consideração das descobertas arqueologicas melhoraram o entendimento do comportamento estrutural do castelo e tem de ser tidos em conta antes de realizar um análise estrutural rigoroso.
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Allahvirdizadeh, Reza. "Modelling of the seismic behaviour of TRM-strengthened rammed earth walls." Master's thesis, 2017. http://hdl.handle.net/1822/54582.
Full textAbstract:
Dissertação de mestrado em Structural Analysis of Monuments and Historical ConstructionsEarthen constructions constitute a considerable part of the existing heritage and a large percentage of the World population is still living or working in buildings built with this structural system. Like other types of masonry structures, rammed earth constructions are acceptably stable under gravity loads, although they are significantly vulnerable to earthquakes. Therefore, a precise understanding of their behavior in case of being subjected to ground motions and the proposing of effective strengthening techniques achieved a great interest both in research and practice. Strengthening methods should be not only to enhance capacity and ductility of the building, but also to satisfy a variety of criteria such as being compatible with the substrate, economical and reversible. Considering all, the low-cost textile reinforced mortar (LC-TRM) strengthening is introduced, and its efficiency on rammed earth walls is studied numerically in the present thesis. In the current study, the seismic performance of both unstrengthened and strengthened rammed earth structural components is investigated. In this regard, in-plane and out-of-plane behaviors are studied by means of different constructed nonlinear finite element models. At first, pushover analysis by massbased lateral load pattern is conducted on unstrengthened walls to evaluate their capacity and understand possible failure mechanisms. Furthermore, the outcomes of these analyses are employed to select the most proper modeling approach from shell or solid elements and the walls with appropriate geometrical dimensions. In the following, pushover analyses are conducted on strengthened walls to choose between different strengthening materials and assess the effectiveness of the adopted strengthening technique. Furthermore, the frequency change of the walls with the damage states (lateral displacement levels) is studied to represent the initiation and propagation of damage in unstrengthened walls and to evaluate the effectiveness of TRM strengthening method. Finally, an artificially generated ground motion record was applied to both unstrengthened and strengthened walls to perform nonlinear time-history analyses. The outcomes were used to compare the dynamic behavior of the walls against the results of the pushover analyses.
As construções de terra constituem uma parte considerável do património construído e uma grande parte da população mundial ainda vive ou trabalha em edifícios construídos com este sistema estrutural. Como outros tipos de estruturas de alvenaria, as construções de terra são estáveis face a cargas gravíticas, embora sejam significativamente vulneráveis a sismos. Portanto, a compreensão do seu comportamento perante a ocorrência de movimentos do solo e a proposta de técnicas efetivas de reforço despertam um grande interesse, tanto a nível da investigação como na prática. Os métodos de reforço devem ser adequados não só para aumentar a capacidade e a ductilidade da construção, mas também para satisfazer uma variedade de critérios, como a compatibilidade com o substrato, custo económico e reversibilidade. Considerando todos estes aspetos, apresenta-se uma técnica baseada em argamassa reforçada com malhas têxteis de baixo custo (LC-TRM), cuja eficiência em paredes de terra é estudada na presente tese do ponto de vista numérico. No presente trabalho, investiga-se o desempenho sísmico de componentes estruturais de taipa não reforçados e reforçados. A este respeito, estudam-se os comportamentos no plano e fora do plano, por meio de diferentes modelos de elementos finitos não lineares. Em primeiro lugar, realiza-se a análise pushover proporcional à massa em paredes não reforçadas para avaliar sua capacidade e compreender possíveis mecanismos de colapso. Adicionalmente, estes resultados são utilizados para selecionar a técnica de modelação mais apropriada (elementos de casca ou sólidos) e as dimensões geométricas mais apropriadas. De seguida, realiza-se a análise pushover em paredes reforçadas para escolher de entre diferentes materiais de reforço e avaliar a eficácia da técnica de reforço adotada. Além disso, a variação das frequências das paredes com os estados de dano (níveis de deslocamento lateral) é estudada para identificar o início e a propagação de dano em paredes não reforçadas e avaliar a estabilidade do método de reforço baseado na técnica TRM. Finalmente, selecionou-se um registro sísmico artificial para realizar análises temporais não lineares de paredes simples e reforçadas. Os resultados são utilizados para comparar o comportamento dinâmico das paredes com os resultados da análise pushover.
This present work was developed within the framework of SAHC Erasmus Mundus Master Course (www.msc-sahc.org) and the project of POCI-01-0145-FEDER-016737 (PTDC/ECM-EST/2777/2014), financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology. They are both kindly acknowledged.
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Azil, chima. "Essai d’élaboration d’une démarche méthodologique de diagnostic sur les coupoles du Souf en Algérie." Doctoral thesis, 2022. http://hdl.handle.net/2158/1256035.
Full textAbstract:
Nelle oasi della regione di Souf in Algeria si è sviluppata nel corso dei secoli una tecnica costruttiva molto particolare e quasi sconosciuta, che ha consentito la crescita di architetture vernacolari uniche poste nella "Lista tentativi dell'UNESCO", come patrimonio diffuso prezioso. L'architettura di questa zona desertica si basa sull'uso di un materiale da costruzione insolito, la pietra Rosa del deserto, ed è caratterizzato da coperture a cupola, che descrivono un paesaggio urbano unico e sorprendente che merita protezione e valorizzazione. Attualmente, i centri urbani di questa zona sono notevolmente degradati essendoci molti edifici interessati da danni di gravità variabile, dallo stato di rudere all’erosione superficiale dell’intonaco. Oltre ai tanti lavori di restauro incoerenti e alla perdita di conoscenze tradizionali, c'è un continuo processo di demolizione e abbandono di edifici che minaccia fortemente questo patrimonio culturale.
La ricerca mira a sviluppare un processo diagnostico metodologico per architetture vernacolari realizzate in pietra Rosa del deserto e per perseguire strategie di salvaguardia coerenti. In particolare, il centro storico di Guemar è stato scelto come area di studio perché ha subito poche modifiche, conservando il suo carattere originario.
Un approccio interdisciplinare a più scale di indagine è stato svolto con l’obiettivo primario di conoscere la tecnica costruttiva impiegata nella realizzazione delle architetture vernacolari di Guemar. In particolare, lo studio storico, urbano e architettonico di Guemar è stato accoppiato a rilievi geometrici e materici, compiendo anche interviste a costruttori locali. Le indagini in situ hanno consentito di effettuare una diagnosi preliminare dei danni ricorrenti, di classificando le patologie osservate e proponendo una interpretazione delle cause. In particolare, è stata effettuata una valutazione di vulnerabilità delle costruzioni e sono stati effettuati campionamenti dei materiali per effettuare test fisici, mineralogici, petrografici e meccanici in laboratorio. Indagini meccaniche indirette sono state svolte anche in situ tramite penetrometro e sclerometro, oltre ad a investigazioni con la termocamera per indagare sia la tessitura muraria nascosta dietro l’intonaco che la risalita di umidità. Nel complesso sono state determinate sia le caratteristiche tecnologiche della tessitura muratoria e dei particolari costruttivi che la composizione chimica e il comportamento meccanico dei costituenti la muratura, blocchi in pietra Rosa del Deserto e malta, e della muratura nel suo complesso. Inoltre, sono state impiegate diverse strategie per valutare il comportamento strutturale della cupola, considerata sia indipendente dalle murature sottostanti che insieme all’intero edificio. La cupola, infatti, costituisce l'elemento più vulnerabile del sistema strutturale. Innanzitutto, è stata applicata l'analisi limite in approccio statico, tramite l’utilizzazione dei poligoni funicolari, che ha fornito un’interpretazione dei tipici schemi di fessurazione osservati. Inoltre, i risultati dei test meccanici sono stati sfruttati per costruire modelli agli elementi finiti, basati sul rilievo 3D (modello HBIM). Analisi statiche sia lineari che non lineari sono state eseguite tramite un software commerciale, che ha permesso una buona simulazione del comportamento altamente non lineare delle costruzioni osservate.
Lo studio multidisciplinare, dal territorio al laboratorio, ha fornito, da un lato, una solida interpretazione dei danni osservati e una base fondamentale su cui imperniare specifiche strategie di conservazione, oltre a costituire una preziosa road map per indagini simili in futuro.
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(7847843), Rahul Deshmukh. "Influence of geometry and placement configuration on side forces in compression springs." Thesis, 2019.
Find full textAbstract:
A leading cause of premature failure and excessive wear and tear in mechanical components that rely on compression springs for their operation is the development of unwanted side forces when the spring is compressed.
These side forces are usually around 10% - 20% of the magnitude of the axial load and point in different directions in the plane perpendicular to the axis of the spring.
The magnitude and direction of the resultant of side forces varies very non-linearly and unpredictably even though the axial force behavior of the spring is very consistent and predictable.
Since these side forces have to be resisted by the housing components that hold the spring in place, it is difficult to design these components for optimal operation.
The hypothesis of this study is that side forces are highly sensitive to small changes in spring geometry and its placement configuration in the housing.
Several experiments are conducted to measure the axial and side forces in barrel springs and two different types of finite element models are developed and calibrated to model the spring behavior.
Spring geometry and placement are parameterized using several control variables and an approach based on design of experiments is used to identify the critical parameters that control the behavior of side-forces.
The models resulted in deeper insight into the development of side forces as the spring is progressively loaded and how its contact interactions with the housing lead to changes in the side force.
It was found that side-forces are indeed sensitive to variations in spring geometry and placement.
These sensitivities are quantified to enable designers to and manufacturers of such springs to gain more control of side force variations between different spring specimens.