<p>In order to achieve results that are reliable when using the finite element method one has to use an acceptable element mesh with respect to the shape and size of the elements. As a help to produce an acceptable mesh there are quality criteria that must be fulfilled in most pre-processors.</p><p>One objective with this thesis is to perform a sensitivity study that can be used as a basis for a Mesh guideline for chassis parts which is requested from engineers at Volvo 3P. The software used in the sensitivity study is ANSA as pre-processor, Nastran as solver and Metapost as post-processor.</p><p>In the first part of the sensitivity study three different models are used for studying quality criteria such as aspect ratio, skewness, mid point alignment, mid point deviation and element size. Solid elements of second order, which are used in the three models, can be generated in two ways, which constitutes another part of the sensitivity study. They may either be generated from the beginning or can be converted from first order elements. This means geometrically that if second order elements where generated from the beginning the element mesh would follow the shape of the component in a better way compared to the other method.</p><p>Recently a pre- and post-processing program called SimLab was introduced on the market. Since SimLab supports geometry import from several CAD-systems without loss of feature information, the automatic element mesh generation is supposed to be better as the mesh generator has access to more information concerning the geometry. An evaluation of SimLab is the second major objective of the thesis. More specifically, the evaluation concerns the possibility of using the software at Volvo 3P.</p><p>Results show a surprising insensitivity regarding the criteria and that the method of generating second order elements from the beginning is to be preferred. SimLab is a new program with big potential and the conclusion is that it is possible to use it at Volvo 3P.</p>

<p>Radio frequency ablation (RFA) is a commonly used minimally invasive method of treating liver cancer tumours which utilises RF current for heating tumour tissue up to a lethal temperature. RF current is generated by a power generator and applied to the tumour by an electrode which is inserted into the tumour either during percutaneous or open surgery. </p><p>RFA is a method that has great advantages compared to traditional surgical resection of tumours due to minimal invasiveness, it can be used for a greater number of patients and enables repeated treatments. Even though there are many advantages coupled to RFA there are still some problems and difficulties associated with the method. One of these problems is the cooling effect from large vessel blood flow within the liver, the so called heat sink effect.</p><p>The aim of this master thesis work has been to develop a theoretical finite element model of RFA within Comsol Multiphysics software. This theoretical model has been used to simulate blood perfusion effects on resulting ablation volume. The effects from different large vessel blood flow parameters has been investigated, these parameters are: blood flow velocity, blood vessel diameter and distance between blood vessel and RF electrode. A factorial design has been utilised to setup parameter levels for the different simulations. A linear- and a second degree regression model has been calculated based on simulation results. The parameter with largest impact on simulative ablation volume and the interaction effects between the parameters were determined from the regression model coefficients. In addition to this has two simulations been performed, modelling perfused- and unperfused liver tissue, in order to investigate the effects resulting from microvascular perfusion.</p><p>The result shows that the parameter with largest impact on simulative ablation volume are the distance, it was also shown that there are a small interactional effects between diameter and distance, where a small distance increases the effect from a varying diameter. Modelled microvascular perfusion was shown to give a decrease in simulative ablation volume. A shortage of this master thesis work is the lack of experimental verification of the developed model. </p>

<p>The purpose of this thesis work is to evaluate how the physical behaviour of a pipe bend is affected by the pipe bending procedure. Effects such as initial ovalization, thinning, thickening and plastic hardening from the bending procedure are examined and the mechanical properties of pipe bends containing these effects are investigated.</p><p>This has been evaluated by creating a detailed Finite Element model of a pipe that is being bent. Then the differences compared to a bent tube in a virgin state, so called Elbow elements and an analytical in-house program have been evaluated. The virgin state refers to a model of a pipe that is bent from the beginning, thus having a homogeneous thickness and not containing any plastic hardening. The Elbow element is a calculationally cheap element, specially developed for accurate calculations of pipe bends in an initially virgin state.</p><p>The goal with the thesis work is to get a better picture of what happens to a pipe as it is being bent, how this affects the mechanical properties and to evaluate the possibility to develop an easy method for taking these effects into account when using the Elbow element.</p><p>This report describes the layout of the work and how the detailed FE-model has been constructed. One step to being able to use the Elbow element with respect to changes in shape and plastic hardening from the manufacturing process has been presented, the differences are though considered being too big to be able to use the Elbow elements with enough confidence in the results. The problems that remain are presented and discussed and proposals for further work are presented.</p>

Bien que les moyens numériques actuels évoluent très rapidement, la résolution de problèmes mécaniques reste confrontée à de nombreuses difficultés (complexité des formes géométriques et des comportements, taille des structures de plus en plus grandes...). Pour contourner ces contraintes, de nombreuses méthodes ont été développées. Deux voies complémentaires peuvent être empruntées : les approches s'appuyant sur des études multi-échelles et le calcul intensif.<br />Les travaux présentés utilisent ces deux voies de manière conjointe et comprennent trois parties: l'étude de problèmes d'homogénéisation périodique traités avec X-FEM, le développement d'une approche multi-échelle tirant profit des avantages de X-FEM et enfin le développement de l'approche X-FEM pour le calcul parallèle.<br />En premier lieu, les travaux portent sur le domaine de l'homogénéisation périodique qui s'est développée lors de l'apparition des matériaux composites. Cette méthode propose de définir des caractéristiques mécaniques généralisées d'une structure comprenant deux matériaux, ou plus, ayant des propriétés distinctes. La structure se décompose en volumes répétitifs appelés V.E.R. (volume élémentaire représentatif). La résolution du problème microscopique sur le V.E.R. nous permet de définir les caractéristiques de la structure entière. La méthode des éléments finis étendue (X-FEM), permettant la présence de discontinuités au sein des éléments du maillage, associée à la technique des fonctions de niveau (Level Set), apportant une alternative à la représentation de formes géométriques complexes ou aléatoires, est employée à cet effet. <br />La deuxième partie présente une analyse multi-échelle d'une structure comprenant un détail. Pour traiter ce type de problèmes, il a souvent été d'usage d'employer des méthodes telles que l'approche globale-locale ou encore des techniques capables de raffiner le maillage autour du détail, mais celles-ci sont coûteuses et parfois peu efficaces. Nous proposons une approche à deux échelles: microscopique (à l'échelle du détail) et macroscopique (à l'échelle de la structure). L'objectif est d'apporter une correction au problème de la structure, ne tenant pas compte explicitement du détail, déduite d'une analyse locale de celui-ci. L'approche X-FEM couplée à la technique des fonctions de niveau est utilisée à cet escient. <br />Enfin, le dernier développement traite de résolutions de problèmes multi-domaines sur une machine parallèle. Mises à part les études précédemment exposées, la difficulté peut ne porter que sur la taille du domaine sur lequel se base le problème. Il s'agit, dans ce cadre, d'augmenter la capacité de calcul pour la résolution de problèmes impliquant une somme de données à traiter très importante. L'étude menée dans cette partie permet la gestion de l'enrichissement entraînée par l'approche X-FEM sur plusieurs domaines

Im Rahmen der Arbeit in der damaligen DFG-Forschungsgruppe ¨Scientific Parallel Computing¨ wurde ein hierarchischer paralleler Netzgenerator fuer das Finite-Elemente- Programmpaket SPC-PM CFD unter dem Namen NETGEN69 entwickelt. Als Programmiersprache wurde seinerzeit - wie auch in den FEM-Programmen selbst - FORTRAN benutzt. Im Rahmen des Teilprojektes B2 im Sonderforschungsbereich 393 bestand nunmehr die Aufgabe, den Netzgenerator in ein objektorientiertes Layout zu fassen und in C++zu implementieren. Die Beschreibung von Ein- und Ausgabedaten kann in [3] nachgelesen werden. Die Form der Eingabedaten hat sich aus Kompatibilitaetsgruenden nicht geaendert und wird auch in Zukunft so beibehalten werden. Auch das der Assemblierung und FEM-Rechnung zuge- wandte Interface wurde vorerst nicht geaendert. Ein Wrapper, der fuer die Generierung der erwarteten Ausgabedaten aus den netzgeneratoreigenen Datenbestaenden sorgt, ist derzeit in Planung. Diese Lösung ist freilich nur voruebergehender Natur; sie ermoeglicht es uns, den Netzgenerator innerhalb der FEM-Bibliotheken zu testen.

In this work the possibility for using natural fiber-reinforced thermoplastics in highly loaded large surface structural elements is demonstrated. A production process to fabricate an inexpensive semi-finished material made of polypropylene and unidirectionally orientated natural fibers was developed. The feasibility of the process was proven for different fiber contents. In further examinations optimal parameters for processing the semi-finished material to produce composites by press forming were examined. With these optimal parameters composites have been fabricated that were tested for their static and dynamic properties. On the basis of the characteristic values of these examinations the field of application for natural fiber reinforced thermoplastics in use of large surface structural elements could be shown. As an example for such an element a rotor blade of a wind turbine with a length of 3,75 m was created. For a prediction of the behaviour of the loaded rotor blade the following load cases were simulated by means of the FEM: - 50-year gust, with a wind velocity of 50 m/s and standing rotor - Nominal load, with a wind velocity of 11 m/s and turning rotor. For an evaluation of the composite behaviour the Tsai Wu criterion was used, because of its capability to determine the failure condition under multi-axle stress. With these simulations it could be shown that it is theoretically possible to use natural fiber-reinforced thermoplastics as material for large surface structural elements. / In der vorliegenden Arbeit wurde eine Möglichkeit für die Verwendung von naturfaserverstärkten Thermoplasten in hochbelasteten großflächigen Strukturbauteilen aufgezeigt. Es wurde ein Verfahren entwickelt, welches die preiswerte Herstellung eines Halbzeuges aus Polypropylen und unidirektional ausgerichteten Naturfasern ermöglicht. Die Realisierbarkeit dieses Verfahrens konnte für verschiedene Naturfasergehalte nachgewiesen werden. In weiteren Untersuchungen wurden die optimalen Verarbeitungsparameter für die Herstellung von Faserverbunden aus diesem Halbzeug mittels der Presstechnik ermittelt. Mit diesen optimalen Parametern wurden Verbunde hergestellt und auf ihre statischen und dynamischen Eigenschaften geprüft. Auf Grundlage der in diesen Prüfungen ermittelten Kennwerte konnte die Einsatzmöglichkeit dieser naturfaserverstärkten Thermoplaste für ein großflächiges Strukturbauteil gezeigt werden. Als Beispiel für ein solches Bauteil wurde ein 3,75 m langes Rotorblatt einer Windkraftanlage entworfen. Um eine Aussage über das Verhalten des Rotorblattes unter Belastung treffen zu können, wurden folgende Lastfälle mit Hilfe der FEM simuliert: - 50-Jahres-Böe, mit Windgeschwindigkeit von 50 m/s und stehendem Rotor - Nennlast, mit Windgeschwindigkeit von 11 m/s und drehendem Rotor Für die Bewertung des Verbundverhaltens wurde das Tsai-Wu-Ausfallkriterium herangezogen, da es eine Aussage über das Bruchverhalten von Faserverbunden unter mehrachsiger Belastung erlaubt. Die Auswertung dieser Simulationen ergab, dass es theoretisch möglich ist, naturfaserverstärkte Thermoplaste als Werkstoff in großflächigen Strukturbauteilen einzusetzen.

Anforderungen an Verbindungen, Verbindungstechnik, Fügen, Modellierungspraxis, Beispiel Verschraubung, Beispiel Klebverbindung, Beispiel Schweißung, Thesen zu Simulationen in der Verbindungstechnik

För att möjliggöra demonstration av knivbyten i en flishugg behöver en visningsjigg för ändamålet konstrueras. Eftersom visningsjiggen endast kommer att tillverkas i ett exemplar inriktades arbetet mot produktutveckling för enstycksproduktion. Växande konkurrens mellan produktutvecklande företag, i kombination med att hela utvecklingskostnaden kommer bäras av endast en produkt, leder till höga krav på minskade utvecklingstider. Under arbetet utvecklades därför en arbetsmodell för att effektivisera konstruktionsarbetet. Arbetsmodellen tillämpades sedan i arbetet med att utveckla visningsjiggen. Arbetsmodellens utformning och innehåll baserades på relevant forskningslitteratur och är definierad i flera steg inom faserna; förstudie, konstruktionsfas och avslut. Kundens krav och önskemål behandlades med metoden kvalitetshuset, vilket framställde mätbara kriterier som sedan styrde konstruktionsarbetet. Genom att upprätthålla en kundkontakt under hela arbetet, med bland annat presentation av två konceptmodeller, erhölls en flexibilitet i arbetet för att hantera otydliga eller tidigare okända kundkrav och kundönskemål. Utifrån arbetsmodellen delades konceptet upp i en hierarkisk struktur med moduler för att skapa en bättre överblick och underlätta arbetsfördelningen. Genom tillämpning av mekanik- och hållfasthetsteori i konstruktionsarbetet har de ingående delarna i visningsjiggen dimensionerats för att möta de uppställda kraven på stabilitet och säkerhet. Med hjälp av finita elementmetoden har sedan konstruktionen analyserats och konstruktionens knivficka optimerats med hänseende på vikt och spänningar i materialet. Examensarbetet har resulterat i en portabel visningsjigg innehållende alla de funktioner som krävs för att demonstrera ett knivbyte. Utböjningen i stommen och knivfickan ligger väl under de krav som finns på visningsjiggens stabilitet. Knivfickan kunde viktreduceras med 29 procent jämfört med ursprungskonceptet, vilket ledde till att mindre kraft krävs att rotera knivfickan i olika arbetspositioner. Vad som kunde observeras angående arbetsmodellen är att de olika modulerna påverkade varandra, vilket inte togs med i beräkningen vid utvecklingen av arbetsmodellen. En analys av hur moduler kan påverka varandra bör därför utföras tidigt under modulindelningsfasen. Utöver detta är slutsatsen att modellen visat sig fungera väl för att hantera de osäkerheter som utveckling av enstycksprodukter för med sig. / To enable demonstration of knife changes in a wood chipper, a demonstration device for this purpose is needed. The demonstration device will only be made in one copy, therefore this work was focused on product development for one piece production. Growing competition among product development companies, along with the fact that the whole development cost will be carried by only one product leads to high demands for reduced development lead times. To meet these requirements a work model was developed to improve the efficiency at the design stage. The model was then applied in the process of developing the demonstration device. The design and content of the work model is based on relevant research literature and is defined in several steps as the feasibility study phase, design phase and finishing phase. Customer requirements were treated with the method house of quality, which produced measurable criteria to be used in the design phase. By maintaining a customer contact throughout the whole design process, for instance presentation of a concept model, a flexibility to handle previously unknown or vague demands and requirements was obtained. Based on the work model the concept was divided into a hierarchical structure with modules to create a better overview and to simplify the design process. Through the application of mechanical and strength theory in the design while designing the parts of the demonstration device, the prescribed requirements for stability and security was met. By performing finite element analysis the concept's structural elements was analyzed and the chipper disc was optimized with regard to weight and material stress. The work has resulted in a portable demonstration device which contains all the functions required to demonstrate knife changes. The deflection of the frame and chipper disc is well below the defined values for stability. The chipper disc weight was reduced by 29 percent compared to the original concept, which means less force is required to rotate the chipper disc between different positions. What could be observed regarding the work model is that the individual modules affected each other, this was not taken into account during the development of the model. An analysis of how the modules can affect each other should therefore be performed early in the modularization phase. The conclusion, in addition to this, is that the work model is proven to work well to deal with the implied uncertainties of one piece product development.

In this thesis, the Mechanical properties of polypropylene yarn of outer protection layer on Submarine High Voltage Cable, twisted around submarine cable,is determined on various conditions at ABB Company. In the first step, tensile tests are done with polypropylene yarn specimens with and without Bitumen at Room temperature. In the second step,tensile tests are done with polypropylene yarn specimens with and without Bitumen and with knotted polypropylene yarn namely: the Fishermen’s knot, the Weaver’s knot, the Square knot and the Overhand knot at Warm Condition (60˚c) and Cold Condition(-5˚c). In the final step,it is proposed to obtain numerical solution using FEM analysis with ABAQUS Software to obtain the hoop stress , the yarn stresses from twisting cable and analyzing of the cylindrical buckling in the buckling torsion and buckling bending on the outer layer of submarine cable with polypropylene material that is mixed with Bitumen.

The construction equipment industry is developing at a fast pace, increasing the expectation on the next-generation machines. Wheel loaders and backhoe loaders are part of this evolution and all subsystems in those machines need to be developed to meet the high demands in energy eciency and productivity. One of the most important parts of the wheel loader is the loading unit. This is traditionally designed using highly experienced engineers and CAD software. To simplify the early stages of this process was an optimization tool developed to generate a design outlay. The optimization will minimize the mass of the linkage since unnecessary weight will lower the eciency. The minimum can be found by moving the joints and adjusting the shape of the device. The optimization will also include constraints to assure the correct performance of the linkage. Since there are a high number of design variables, a gradient-based optimization method was used. A finite element solver was also implemented to calculate the forces and stresses in the linkage. The linkages studied in this report are one from a typical wheel loader and one from a backhoe loader. Since these machines are extremely versatile, and used formany diferent tasks, two sets of constraints are compiled. One of the constraint sets yields a linkage suitable for machines only equipped with bucket, while the other results in an all-round linkage suitable for most tools and applications. The optimized linkages are compared to existing devices. The results show that there are some improvements possible and that the software could be used to help designers. However, the optimization problem is hard to solve due to non-smooth constraints functions and numerical instabilities. This issue could be overcome by diferent means, like using automatic diferentiation, a non-gradient based optimization method, decreasing the number of constraints or decreasing the number of design variables. / Utvecklingen av anlaggningsmaskiner sker i snabb takt och detta ökar förväntningarna på framtidens maskiner. En stor andel av alla anläggningsmaskiner är hjullastare och traktorgrävare och alla delsystem på dessa maskiner måste följa med i utvecklingen. En av de viktigaste delarna pa en hjullastare ar lastaggregatet. Det designas traditionellt med hjälp av CAD mjukvara och mycket erfarna konstruktörer. För att underlätta denna process har en optimeringsrutin utvecklats, som generarar ett designförslag. Optimeringen minskar länkagets massa genom att fytta lagringspositioner och ändra delarnas dimensioner. Detta ökar efektiviteten hos maskinen eftersom den slipper köra runt på onödig vikt. Optimeringen innehåller även villkor för att säkerställa god prestanda hos det optimerade aggregatet. Eftersom det ingår väldigt många designvariabler i optimeringen används en gradientbaserad metod. En finita element approximation används for att beräkna krafter och spänningar i länkaget. De länkage som undersöks i detta projekt är ett typsikt hjullastaraggregat och ett typiskt traktorgrävaraggregat. Eftersom dessa maskiner ar väldigt mångsidiga sammanställdes två olika uppsättningar av villkor. Den ena uppsättningen används för att optimera ett aggregat som endast ska användas med skopa, medan den andra uppsättningen används för att ta fram ett mer mångsidigt aggregat avsätt for att kunna klara av de flesta situationer och verktyg. De optimerade lastaggregaten är jämförda med produktionsaggregat och det visar sig att vissa förbättringar är möjliga. Slutsattsen är att optimeringsrutinen kan bli ett bra hjälpmedel for konstruktörer men att den behöver lite mer veriering. Villkorsfunktionen som optimeringen måste lösa är inte helt slät vilket är ett problem för en gradientbaserade metod och dessutom finns vissa numeriska instabiliteter. Dessa svårigheter kan undkommas pa olika sätt, t.ex. genom att använda automatisk derivering,byta optimeringsalgoritm, minska antalet villkor eller minska antalet variabler.