El Método de los Elementos Finitos (MEF) se ha afianzado durante las últimas décadas como una de las técnicas numéricas más utilizadas para resolver una gran variedad de problemas en diferentes áreas de la ingeniería, como por ejemplo, el análisis estructural, análisis térmicos, de fluidos, procesos de fabricación, etc. Una de las aplicaciones donde el método resulta de mayor interés es en el análisis de problemas propios de la Mecánica de la Fractura, facilitando el estudio y evaluación de la integridad estructural de componentes mecánicos, la fiabilidad, y la detección y control de grietas. Recientemente, el desarrollo de nuevas técnicas como el Método Extendido de los Elementos Finitos (XFEM) ha permitido aumentar aún más el potencial del MEF. Dichas técnicas mejoran la descripción de problemas con singularidades, con discontinuidades, etc., mediante la adición de funciones especiales que enriquecen el espacio de la aproximación convencional de elementos finitos. Sin embargo, siempre que se aproxima un problema mediante técnicas numéricas, la solución obtenida presenta discrepancias con respecto al sistema que representa. En las técnicas basadas en la representación discreta del dominio mediante elementos finitos (MEF, XFEM, ...) interesa controlar el denominado error de discretización. En la literatura se pueden encontrar numerosas referencias a técnicas que permiten cuantificar el error en formulaciones convencionales de elementos finitos. No obstante, por ser el XFEM un método relativamente reciente, aún no se han desarrollado suficientemente las técnicas de estimación del error para aproximaciones enriquecidas de elementos finitos. El objetivo de esta Tesis es cuantificar el error de discretización cuando se utilizan aproximaciones enriquecidas del tipo XFEM para representar problemas propios de la Mecánica de la Fractura Elástico Lineal (MFEL), como es el caso del modelado de una grieta. / González Estrada, OA. (2010). Estimación y acotación del error de discretización en el modelado de grietas mediante el método extendido de los elementos finitos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/7203

The characterization of the mechanical behavior of soft living tissues is a big challenge in Biomechanics. The difficulty arises from both the access to the tissues and the manipulation in order to know their physical properties. Currently, the biomechanical characterization of the organs is mainly performed by testing ex-vivo samples or by means of indentation tests. In the first case, the obtained behavior does not represent the real behavior of the organ. In the second case, it is only a representation of the mechanical response of the indented areas. The purpose of the research reported in this thesis is the development of a methodology to in-vivo characterize the biomechanical behavior of two different organs: the breast and the cornea. The proposed methodology avoids invasive measurements to obtain the mechanical response of the organs and is able to completely characterize of the biomechanical behavior of them. The research reported in this thesis describes a methodology to in-vivo characterize the biomechanical behavior of the breast and the cornea. The estimation of the elastic constants of the constitutive equations that define the mechanical behavior of these organs is performed using an iterative search algorithm which optimizes these parameters. The search is based on the iterative variation of the elastic constants of the model in order to increase the similarity between a simulated deformation of the organ and the real one. The similarity is measured by means of a volumetric similarity function which combines overlap-based coefficients and distance-based coefficients. Due to the number of parameters to be characterized as well as the non-convergences that the solution may present in some regions, genetic heuristics were chosen to drive the search algorithm. In the case of the breast, the elastic constants of an anisotropic hyperelastic neo-Hookean model proposed to simulate the compression of the breast during an MRI-guided biopsy were estimated. Results from this analysis showed that the proposed algorithm accurately found the elastic constants of the proposed model, providing an average relative error below 10%. The methodology was validated using breast software phantoms. Nevertheless, this methodology can be easily transferred into its use with real breasts. In the case of the cornea, the elastic constants of a hyperelastic second-order Ogden model were estimated for 24 corneas corresponding to 12 patients. The finite element method was applied in order to simulate the deformation of the human corneas due to non-contact tonometry. The iterative search was applied in order to estimate the elastic constants of the model which approximates the most the simulated deformation to the real one. Results showed that these constants can be estimated with an error of about 5%. After the results obtained for both organs, it can be concluded that the iterative search methodology presented in this thesis allows the \textit{in-vivo} estimation the patient-specific elastic constants of the constitutive biomechanical models that govern the biomechanical behavior of these two organs. / Lago Ángel, MÁ. (2014). A new approach for the in-vivo characterization of the biomechanical behavior of the breast and the cornea [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/44116

In fighter jets there are many different systems that make the plane fly, and one of these is the fuel system consisting of multiple parts including tanks and tubes. During flight, the pressure in these tubes can vary and occasionally pressure spikes can occur. Pressure spikes can be described as high increased pressure at a high rate and decreased pressure at an equally high rate during a limited time span. Depending on the peak pressure and duration of this pressure spike, damage or failure might occur in the tube structure. This is a problem that SAAB is analyzing and wants to find a less conservative approach of analyzing the effect of pressure spikes regarding the structural strength of tubes. In this master’s thesis this is explored. A method for applying pressure spikes to two different tube structures has been created. The pressure spike propagates through the liquid and applies the pressure spike to the tube through Mortar contact. The tube is modelled with shell elements and normal Lagrangian element formulation. The liquid is modelled with solidelements and Arbitrary Lagrangian Eulerian element formulation. The two different tube structures analyzed in this report have the same tube dimensions, a combination of the biggest radius and smallest wall thickness that occur in SAAB’s tubes. The difference between the two is that one structure is straight whilst the other is curved. A parametric study was carried out to analyze at what pressure peak different durations of the pressure spikes would result in a critical effective plastic strain. This critical effective plastic strain was chosen to be 0.08 for the aluminum tube. This is conservative since the fracture strain for the material is 0.12. Results froma static case was compared with the dynamic results from the described method to see how conservative this new method of pressure spike analysis is. The results from the comparison showed that the dynamic method allowed 65% higher pressure peak thanthe static solution. Using a pressure spike with 1ms duration and pressure peak at 19.5MP a in the straight tube compared with the internal pressure of 11.4MP a in the static method for the straight tube. For the curved tube, the dynamic method allowed 90% higher peak pressure for a pressure spike with 1ms duration and peak pressure of 18.5MP a. This pressure spike in the curved tube is compared with the static method for the curved tube which reached critical effective plastic strain at 9.4MP a. For pressure spikes with durations of 20ms in straight tubes, the dynamic and static results are similar. For pressure spikes with durations of 10ms in curved tubes, the dynamic and static results are similar. In these cases, it is reasonable to use the quicker static method instead of the new method of pressure spike analysis. The impulses in both the straight tube and the curved tube cases have a linear relationships with the duration of the pressure spike. For the longer durations the energy needed to reach critical deformation is higher since the affected area is larger. Shorter durations need less energy to reach critical deformation since the affected area is smaller.

In the 1970s, the tandem shaped charge was developed to overcome countermeasures like active armor and thicker armor. It uses a leading charge to clear a path for the main trailing charge, theoretically improving penetration. However, disturbances from shock waves can cause under-performance. To address this, the leading charge's shock waves must be minimized to protect the main charge. Designing a part with shock wave attenuating properties can help achieve this.There is limited information on grenade structures that reduce shock wave stresses from impact and detonation. Most studies on shock wave attenuation focus on protecting buildings and humans, with few addressing structures designed to withstand and then halt the transmission of shock waves. Here we report on simulations in IMPETUS Afea where an explicit FEM solver approach have been made to compare four different concepts to an original structure. Physical theories about attenuation of shock waves in solids has been applied. The first concept utilize a mass with different area increases in the propagation path of the shock wave. The second concept use the characteristics of interfaces between two different materials, with different shock wave impedance which will reflect and transmit the incoming wave. The third concept incorporate a brittle ceramic which should shatter when a shock wave propagates to it, if the brittle structure fracture, no more shock waves can be transmitted. The fourth concept utilize the properties of porous metals. All concepts shows shock wave attenuating effects, but only the third concept which totally disconnects the leading shaped charge to the main charge might be a full solution. The fourth concept compared to the third has other advantages, it attenuate the shock wave to more than 90%, not halt the transmission. Configuration of the porosity in the structural part can be made to have characteristics that can solve the problem. Concept three and four are the main recommendations for a feasibility study. / På 1970-talet utvecklades tandem-RSV laddningar för att övervinna motmedel som aktivt pansar och tjockare pansar. De använder en förladdning för att skapa en väg för den efterföljande huvudladdningen, vilket teoretiskt sett förbättrar prestandan. Störningar från tryckvågor från olika källor orsaka prestandaförluster. För att hantera detta måste islagets och förladdningens tryckvågor minimeras för att skydda huvudladdningen. Att designa en mellandel med egenskaper som dämpar tryckvågor kan hjälpa till att uppnå detta. Information om granatstrukturer som minskar tryckvågsbelastningar från islag och detonation är begränsad. De flesta studier om dämpning av tryckvågor fokuserar på att skydda byggnader och människor, med få som behandlar strukturer designade för att motstå och sedan stoppa överföringen av tryckvågor. Här rapporterar vi om simuleringar genomförda i IMPETUS Afea med en explicit FEM-lösare för att jämföra fyra olika koncept mot en originalstruktur. Fysiska teorier om dämpning av tryckvågor i fasta material har tillämpats. Det första konceptet utnyttjar en massa med olika areaökningar i tryckvågens propagationsväg. Det andra konceptet använder egenskaperna hos gränsytor mellan två olika material med olika tryckvågsimpedanser som kommer att reflektera och transmittera den inkommande tryckvågen. I det tredje konceptet appliceras en spröd keram som bör splittras när en tryckvåg fortplantas till den. Om den spröda strukturen spricker kan då inga fler tryckvågor överföras genom strukturen. Det fjärde konceptet utnyttjar egenskaperna hos porösa metaller. Alla koncept visar tryckvågsdämpande effekter. Men endast det tredje konceptet som helt kopplar bort förladdningen från huvudladdningen kan vara en fullständig lösning. Det fjärde konceptet jämfört med det tredje har andra fördelar; det dämpar tryckvågen till mer än 90%, men stoppar inte överföringen helt. Konfigurationen av porositeten i den strukturella delen kan utformas för att ha egenskaper som kan lösa problemet. Koncept tre och fyra är de huvudsakliga rekommendationerna för en genomförbarhetsstudie.

Since the construction industry has a significant impactful footprint on the climate, a transition to sustainable solutions is imperative. Concrete is the predominant material for load-bearing structures in multi-residential buildings and is usually used in more walls than necessary, resulting in unnecessary excess of carbon dioxide. This study aims to climate-optimize the intended load-bearing structure in a multi-residential building project by evaluating the possibility of an alternative load-bearing structure. Concrete party walls, those which are unnecessary for load-bearing purposes, are removed in the alternative load-bearing structure and replaced with stud walls that meet sound and fire requirements. The comparison is made between the alternative and intended load-bearing structures concerning structural performance and overall climate impact. To comprehend the subject, an extensive literature study was conducted. Subsequently, the load-bearing structures were modelled in FEM-design program to analyse and compare structural aspects. Using FEM-Climate, life-cycle analyses (LCAs) were performed for both load-bearing structures to assess the difference in the total amount of carbon dioxide equivalents ( ). The results indicate that utilization rates are optimized in the alternative load-bearing structure with the reduction of concrete walls. Furthermore, the results show that the deflection value in the alternative load-bearing structure increases relative to the intended, which is deemed acceptable according to the established requirements. Moreover, LCA results show that the total amount of carbon dioxide equivalents ( ) decreased by approximately 6.5% kg   per gross area in the alternative load-bearing structure. However, with the replacement of stud walls, the total amount of   increased by about 6% kg   per gross area. This resulted in the alternative load-bearing structure being a less favourable solution than the intended one, as no optimization had been achieved from a climate perspective according to the LCA calculations and   values. Since the construction industry has a significant impactful footprint on the climate, a transition to sustainable solutions is imperative. Concrete is the predominant material for load-bearing structures in multi-residential buildings and is usually used in more walls than necessary, resulting in unnecessary excess of carbon dioxide. This study aims to climate-optimize the intended load-bearing structure in a multi-residential building project by evaluating the possibility of an alternative load-bearing structure. Concrete party walls, those which are unnecessary for load-bearing purposes, are removed in the alternative load-bearing structure and replaced with stud walls that meet sound and fire requirements. The comparison is made between the alternative and intended load-bearing structures concerning structural performance and overall climate impact. To comprehend the subject, an extensive literature study was conducted. Subsequently, the load-bearing structures were modelled in FEM-design program to analyse and compare structural aspects. Using FEM-Climate, life-cycle analyses (LCAs) were performed for both load-bearing structures to assess the difference in the total amount of carbon dioxide equivalents ( ). The results indicate that utilization rates are optimized in the alternative load-bearing structure with the reduction of concrete walls. Furthermore, the results show that the deflection value in the alternative load-bearing structure increases relative to the intended, which is deemed acceptable according to the established requirements. Moreover, LCA results show that the total amount of carbon dioxide equivalents ( ) decreased by approximately 6.5% kg   per gross area in the alternative load-bearing structure. However, with the replacement of stud walls, the total amount of   increased by about 6% kg   per gross area. This resulted in the alternative load-bearing structure being a less favourable solution than the intended one, as no optimization had been achieved from a climate perspective according to the LCA calculations and   values.

The construction industry in Sweden face increasing demands for sustainability and reduced greenhouse gas emissions and with the introduction of climate declarations for new projects marking a significant development. There is a rising interest in sustainable materials like cross laminated timber (CLT). Analyzing CLT-joists and their complementary materials impact on projects economically, environmentally, and structural performance can enhance decision-making in the early stages of a project. This study conducted a structural-, climate impact-, and cost analysis along with a multicriteria assessment. The structural analysis, based on Eurocodes and using the software FEM-design showed that all joist types met structural requirements, with type 3 being more versatile due to its cooperation with concrete. It also showed that type 11 with its lighter weight made it easier for installations and a possible reduced transport emission. The climate impact analysis, done through an LCA in OneClick LCA, revealed that type 3 had the highest impact mainly due to its concrete layer, while type 9 had the lowest impact. In term of costs, a cost analysis was done with the use of BidCon. The results of the cost analysis showed that type 3 is the most expensive due to its longer installation time and material costs, while type 11 was the cheapest. CLT and concrete were identified as the costliest materials. The multicriteria assessment concluded that type 11 is preferred for its affordability, sustainability, and performance efficiency. However, if solely pursuing sustainability, type 9 could be considered despite its slightly higher costs.

Uppsatsen synliggör hur matematikböcker under de senaste 50 åren erbjuder elever i åk 5–6 ett algebraiskt tänkande utifrån Kierans aktiviteter och Blantons stora algebraiska idéer. Kierans aktiviteter är en modell inom algebra där uppgifter i matematikböcker kategoriseras utifrån tre aktiviteter: skapande, transformella- och globala meta-aktiviteterna. I de skapande aktiviteterna ska elever själva skapa eller skriva ett uttryck eller ekvation. I de transformella aktiviteterna ska elever lösa en ekvation eller förenkla ett uttryck och i de globala meta-aktiviteterna ska elever möta problemlösning, generalisera och se strukturer. Aktiviteterna hjälper oss att på ett djupare plan analysera om uppgifterna erbjuder ett algebraiskt tänkande eller inte. Uppsatsen analyserar även uppgifter genom Blantons fem stora idéer för att kategorisera algebrans delar och för att de, om de framförs på ett visst sätt, erbjuder ett algebraiskt tänkande. I uppsatsen används en kvalitativ och kvantitativ innehållsanalys av läromedel. Resultatet av de analyserade läromedlen visar att de äldre läromedlen erbjuder ett algebraiskt tänkande genom generaliserande uppgifter (GA) i kombination med globala meta-aktiviteter, samtidigt som de nyare läromedlen erbjuder ett algebraiskt tänkande genom algebraiska strukturer och variabler (EEEI + VAR) i skapande aktiviteter. Tidigare forskning förespråkar generaliserad aritmetik i uppgifter för att erbjuda ett algebraiskt tänkande, vilket enligt uppsatsens resultat inte syns i hög grad. Dessutom menar forskning att algebraiskt tänkande inte måste förutsättas genom vissa uppgifter av kombinationer av stora idéer eftersom de i vissa fall kan lösas med hjälp av aritmetiska procedurer.

En kåpa till en bärplanssurfbräda konstruerades av glasfiber. Med målsättningen att skydda elektronik som möjliggör autonom drift, togs specifikation och kravspecifikation fram. Olika koncept togs fram i samarbete med kravställaren och en specifik modell valdes. En modell skapades sedan i CAD, varpå den analyserades och tjockleken optimiserades i Ansys. Tillverkningen började därefter med att en noskon skapades, som ett gränssnitt mellan kåpan och surfbrädan. Noskonen tillverkades med vakuuminfusion direkt på surfbrädan. Därefter tillverkades kåpan med vakuuminfusion på en gjutform. Gjutformen var i sin tur skapad med glasfiberkomposit genom handuppläggning på en beskuren plugg av extruderad polystyren. Total vikt uppgick till cirka 3,7 kg.

<p>Detta examensarbete har utförts på Fläktwoods AB i Växjö, som producerar stora axialfläktar för olika industriapplikationer. Syftet är att öka kunskapen om fettsmorda axiella kullager genom FE analyser.</p><p>Projektet har genomförts i fem delsteg för att avgöra påverkan av en eller några få parametrar i taget. De studerade parametrarna är: elementstorlek, kontaktstyvhet, last, lagergeometri (dvs. oskulation), ickelinjär geometri och ickelinjära materialegenskaper (dvs. plasticitet).</p><p>Slutsatsen är att elementstorleken bör väljas fint nog för att ge ett jämnt resultat men grovt nog för att beräkningstiden skal vara rimlig. Kontaktstyvheten har inte stor, men tydlig, inverkan på kontakttrycket och penetrationen. Förändringar av oskulationen leder till förändringar i kontaktellipsens form medan olika laster inte påverkar formen på ellipsen, utan snarare storleken. När det handlar om plasticitet är sträckgränsen den viktigaste faktorn att beakta.</p> / <p>This thesis project was carried out at Fläktwoods AB in Växjö who produces large axial fans for different industry applications. The purpose is to increase the knowledge of grease lubricated axial ball bearings through FE analyses.</p><p>The project was executed into five sub steps to determine the influence of one or few parameters at a time. The studied parameters are: mesh density, contact stiffness, load, bearing geometry (i.e. osculation), geometrical nonlinearity and material nonlinearity (i.e. plasticity).</p><p>It is concluded that the mesh density should be selected fine enough to give a smooth result but course enough to give a reasonable calculation time. The contact stiffness has not a major, but a clear, impact on the contact pressure and penetration. Changes of the osculation lead to changes of the contact ellipse shape and applying different load level does not affect the shape of the ellipse but rather the size. When dealing with plasticity the yield strength is the most important factor to take in consideration.</p>

Detta examensarbete har utförts åt Ålö, som är en tillverkare av frontlastare och redskap till dessa. Ett av deras redskap, vars syfte är snöröjning, är utrustat med hydrauliskt justerbara sidoklaffar som kan fällas bakåt och nyttjas som plogblad. De fyller dock inte denna uppgift tillfredsställande då snö tenderar falla tillbaka bakom dem. Det bildas även en triangulär spalt mellan klaffarna och underlaget vid plogning, detta lämnar kvar en sträng av snö, utöver det som faller ner bakom klaffarna. Målet i detta projekt var att utveckla en plogklaff som löser tidigare nämnda problem genom att ersätta den högra sidoklaffen till skopan. Utvecklingen har initierats med en studie av rapporter, existerande plogar, kontakt med brukare och fastställande av de begränsningar som råder. Detta har sedan utgjort grunden för en rad koncept, av vilka de mest lovande sammanfogades till en prototyp. Kraftberäkningar utifrån det lastfall som uppstår vid plogning har sedan använts för att bl.a. dimensionera skruvförband och skapa randvillkoren för en finita element-analys. Finita element-analysen har sedan nyttjats för att göra en uppskattning av antalet cykler med momentan maximal belastning plogklaffen klarar innan utmattningsbrott sker. Kraftberäkningarna visade att hydraulcylinderns tryckbegränsare öppnar redan innan maximal belastning uppnås. Finita element-analys och kraftberäkningar till skruvförband förutsätter likväl att maximal belastning kan erhållas momentant i syfte att ge konservativa resultat. Under denna förutsättning skiljer belastningen i skruvförbanden endast ca 7-10 % mellan finita element-analys och handberäkningar. Samtliga beräkningar är inom spannen för skruvförbandens hållfasthet. Utmattningsberäkningarna visade att antalet cykler plogklaffen klarar vid maximal belastning uppgår till ca 346 000. Detta avser områden av intresse och inkluderar således ej delar vilka redan utvärderats i originalklaffen. Svetsförband, som i regel är dimensionerande i situationer som dessa, har ej sett någon utmattningsmässig utvärdering utan kommer istället behandlas vid tester av prototypen. Prototypen uppfyller de utsatta målen och tillverkningsunderlag i form av 3D-CAD modeller och 2D-ritningar (inklusive svetsritningar) har levererats. En fysisk prototyp är även beställd och kommer tillverkas av Vännäs Verkstads AB, planerat leveransdatum är 2017-06-08. Den kommer utvärderas under vintern 2017/2018. / This thesis work has been carried out for Ålö, a manufacturer of front loaders and implements for these. One of their implements, whose purpose is snow clearing, is equipped with hydraulically adjustable flaps that can be folded backwards and used as plows. However, they do not fill this task satisfactorily as snow tends to fall down behind them. A triangular gap between the flaps and the ground is also formed during plowing. This leaves a string of snow behind, aside from the snowmass already falling down behind the flaps. The goal for this project was to develop a plow that solves the aforementioned problems by replacing the right side flap on the bucket. The development was initiated with a study of reports, existing plows, contact with users and determining existing constraints. This has since provided the basis for a series of concepts, of which the most promising ones were joined to a prototype. Force calculations based on the load scenario that occurs during plowing have been used to find appropriate fasteners and create boundary conditions for a finite element analysis. The finite element analysis has then been used to estimate the number of cycles with maximum load the plow can be subjected to before it succumbs to fatigue failure. Force calculations showed that the pressure limiter for the hydraulic cylinder opens even before maximum load is reached. Despite this, finite element analysis and force calculations for fasteners were still based on the condition that maximum load is achieved momentarily to produce convervative results. Under this condition, the load on fasteners differs only ca 7-10 % between finite element analysis and calculations made by hand. All calculations are within the span for the fasteners proof strength. Fatigue calculations showed that the number of cycles the plow can handle with maximum load amounts to approximately 346 000. This refers to areas of interest and thus does not include parts already evaluated in the original flap. Welds, which usually dictate minimum strength in situations like these, have not seen any fatigue evaluations, but will instead be addressed while testing the prototype. The prototype meets the set goals and production documentation in the form of 3D-CAD models and 2D drawings (including weldment drawings) have been delivered. A physical prototype is also ordered and will be manufactured by Vännäs Verkstads AB, scheduled delivery date is 2017-06-08. It will be evaluated during the winter of 2017/2018.