I konstruktionsarbetet idag är användningen av beräkningsprogram självklart. Det finns en rad olika program som baseras på olika teorier. En typ av dessa program är FEM programmen som bygger på den finita element metoden som är en elasticitetsteoretisk metod. Eftersom att FEMprogrammen kan hantera komplicerade konstruktioner används dessa i stor utsträckning. Eftersom att FEM bygger på elasticitetsteori och handberäkningar på gränslastteori är det viktigt att vara medveten om skillnaderna som kan uppstå mellan de olika teorierna. Det som har påvisats tidigare är att FEM överarmerar betongplattor i flera fall jämfört med gränslastteori. Problematiken har till stor del att göra med stödmoment. I rapporten jämförs pelardäck som dimensioneras direkt med FEM-designs automatiska design funktion och med funktionen auto peak smoothing mot dimensionering med en framtagen metod som plockas från befintlig litteratur, jämförelsen inkluderar även ett Eurokod 2 dimensioneringsexempel för pelardäck. Genom det skapas en metod som ska effektivisera stödmomentsarmeringen i pelardäck. Men även skapa en förståelse för hur liknande problem i liknande konstruktioner kan lösas. Metoden hanterar hur moment ska omfördelas och under vilka områden omfördelning ska göras. För att verifiera metoden så görs jämförelsen av pelardäckskonstruktionen. Resultatet är tydligt och visar på en klar effektivisering mot programmets egen dimensioneringsfunktion. Den framtagna metoden visar sig även mer effektiv i jämförelse med Eurokods eget dimensioneringsexempel / In the design work today, the use of calculation programs is obvious. There are a variety of programs based on different theories. One type of these programs are the FEM programs based on the finite element method which is an elasticity theory method. Because the FEM programs can handle complicated constructions, they are widely used. FEM is based on the elasticity theory and regular calculations on plastic theory, it is important to be aware of the differences that may arise between the different theories. It has been demonstrated before that FEM designs more reinforcement in concrete slabs in several cases compared to plastic theory. The problem is largely due to point supports for example columns. The study compares flat slab that are designed directly with FEM designs automatic design function against dimensioning using a developed method picked from existing literature, the comparison also includes a Eurocode 2 flat slab example. This creates a method that will streamline the support momentum in flat slabs. But also create an understanding of how similar problems in similar constructions can be solved. The method manages how to redistribute torques and the areas in which it will be redistributed. To verify the method, the comparison of the flat slab construction is done. The result is clear and demonstrates a clear efficiency towards the program's own dimensioning function. The developed method also proves more effective compared to Eurocod's own dimensioning example. / <p>Betyg 170707, H14.</p>

This thesis investigates two a posteriori error estimators, based on gradient recovery, aiming to fill the gap of the error estimations for the Generalized FEM (GFEM) and, mainly, its modified versions called Corrected XFEM (C-XFEM) and Stable GFEM (SGFEM). In order to reach this purpose, firstly, brief reviews regarding the GFEM and its modified versions are presented, where the main advantages attributed to each numerical method are highlighted. Then, some important concepts related to the error study are presented. Furthermore, some contributions involving a posteriori error estimations for the GFEM are shortly described. Afterwards, the two error estimators hereby proposed are addressed focusing on linear elastic fracture mechanics problems. The first estimator was originally proposed for the C-XFEM and is hereby extended to the SGFEM framework. The second one is based on a splitting of the recovered stress field into two distinct parts: singular and smooth. The singular part is computed with the help of the J integral, whereas the smooth one is calculated from a combination between the Superconvergent Patch Recovery (SPR) and Singular Value Decomposition (SVD) techniques. Finally, various numerical examples are selected to assess the robustness of the error estimators considering different enrichment types, versions of the GFEM, solicitant modes and element types. Relevant aspects such as effectivity indexes, error distribution and convergence rates are used for describing the error estimators. The main contributions of this thesis are: the development of two efficient a posteriori error estimators for the GFEM and its modified versions; a comparison between the GFEM and its modified versions; the identification of the positive features of each error estimator and a detailed study concerning the blending element issues. / Esta tese investiga dois estimadores de erro a posteriori, baseados na recuperação do gradiente, visando preencher o hiato das estimativas de erro para o Generalized FEM (GFEM) e, sobretudo, suas versões modificadas denominadas Corrected XFEM (C-XFEM) e Stable GFEM (SGFEM). De modo a alcançar este objetivo, primeiramente, breves revisões a respeito do GFEM e suas versões modificadas são apresentadas, onde as principais vantagens atribuídas a cada método são destacadas. Em seguida, alguns importantes conceitos relacionados ao estudo do erro são apresentados. Além disso, algumas contribuições envolvendo estimativas de erro a posteriori para o GFEM são brevemente descritas. Posteriormente, os dois estimadores de erro propostos neste trabalho são abordados focando em problemas da mecânica da fratura elástico linear. O primeiro estimador foi originalmente proposto para o C-XFEM e por este meio é estendido para o âmbito do SGFEM. O segundo é baseado em uma divisão do campo de tensões recuperadas em duas partes distintas: singular e suave. A parte singular é calculada com o auxílio da integral J, enquanto que a suave é calculada a partir da combinação entre as técnicas Superconvergent Patch Recovery (SPR) e Singular Value Decomposition (SVD). Finalmente, vários exemplos numéricos são selecionados para avaliar a robustez dos estimadores de erro considerando diferentes tipos de enriquecimento, versões do GFEM, modos solicitantes e tipos de elemento. Aspectos relevantes tais como índices de efetividade, distribuição do erro e taxas de convergência são usados para descrever os estimadores de erro. As principais contribuições desta tese são: o desenvolvimento de dois eficientes estimadores de erro a posteriori para o GFEM e suas versões modificadas; uma comparação entre o GFEM e suas versões modificadas; a identificação das características positivas de cada estimador de erro e um estudo detalhado sobre a questão dos elementos de mistura.

This thesis is a measurement evaluation type of project in which to perform a harmonic response analysis were the results will be compared to measurement data to verify if the ANSYS model is realistic in terms of dynamics. This includes proposing the different parameters that will affect the results of the comparison as well as how to improve further models. In 2014 Atlas Copco received a special customer order of a ST1530 loader with a Detroit engine instead of a Cummins engine which is commonly used in the ST1530. New dynamic analyses had to be performed by the Applied Mechanics Group, regarding harmonic response using data from a measurement of a ST1520 loader with a Detroit engine. A new design of the engine cradle was developed after several analysis iterations. In February 2015, new measurements were performed on the loader with the right Detroit engine and a new engine cradle. There are two different comparison tools/methods used in this thesis, one that consists of comparing the difference between the mean average value of both the ANSYS and the measurements results. The other tool/method is more accurate since it compares both the variation between the peaks and also the offset of the frequency. Results show that the measurement results in 800 rpm were very compatible with the analysis results in ANSYS, meanwhile at high speed the measurement results were only moderately compatible with the analysis results. The vibration in 800 rpm doesn’t exceed the Atlas Copco rule of thumb as opposed to the 2173 rpm. This is only considering the cradle, the cooler however consists of higher vibrations than the measurement data. Their rule of thumb is defined as a boundary for the maximum allowable vibration values. The model could’ve been a lot more accurate if the use of CAD models of both the engine and the cooler were implemented in the analysis. This is desirable but it does not work all the time as companies for these products can not issue a CAD model due to, e.g. Patents and such. / Denna avhandling är en mätutvärdering där man ska utföra en harmonisk responsanalys vars resultat kommer att jämföras med mätdata för att kontrollera om ANSYS modellen är realistisk i dynamiska termer. Detta inkluderar även att man ska föreslå de olika parametrar som kommer att påverka resultatet av jämförelsen samt hur man kan förbättra ytterligare modeller. Under 2014 erhöll Atlas Copco en speciell kundorder med en ST1530 lastare där man ville ha en Detroitmotor istället för en Cumminsmotor som ofta används i ST1530. Detta resulterar i att nya dynamiska analyser måste utföras av Applied Mechanics Group, angående harmonisk respons där man använde data ifrån en mätning av en ST1520 lastare med Detroit motor. En ny utformning av motorvaggan utvecklades efter flera iterationer. I februari 2015 så utfördes nya mätningar på lastaren med rätt Detroitmotor och den nya motorvaggan. Två olika jämförelseverktyg/metoder användes i denna avhandling. Det första verktyget/metoden testades, som består av att jämföra skillnaden mellan det genomsnittliga medelvärdet av både ANSYS och mätresultat. Det andra verktyget/metoden användes för att den är mer exakt eftersom den jämför både variationen mellan vibrationstopparna och även förskjutningen i frekvens. Resultaten visar att mätresultaten i låg hastighet (800 rpm) var mycket förenliga med analysresultaten i ANSYS, däremot vid hög hastighet (2173 rpm) var mätresultaten bara måttligt förenliga med analysresultaten. Vibrationerna i 800 rpm överstiger inte Atlas Copcos tumregel till skillnad från 2173 rpm, detta är bara med tanke på vaggan. Kylaren har däremot högre vibrationer än mätdata.Denna tumregel är definierad som en avgränsning för maximalt tillåtna vibrationsvärden. Modellen kunde varit mycket mer exakt om man hade implementerat CAD-modeller av både motorn och kylaren i analysen. Detta är önskvärt men funkar inte hela tiden då företagen för dessa produkter inte kan ge ut en CAD modell, pga. t.ex. patent eller liknande.

Örebro svets &amp; hydraulik AB tillverkar lastknektar till Suzuki Garphyttan. På lastknektarna transporteras sedan stora rullar av tråd i stål. Knektarna har visat sig kollapsa efter viss tids användning och behöver därför en förbättrad konstruktion. Höga laster, tuff hantering samt ovarsamma lyft kan vara orsaker till att knektarna kollapsar. Örebro svets är väl införstådda var skadorna uppstår i nuvarande konstruktion och vill därför förstärka denna del och konstruktionen i sin helhet. Kraven på den nya konstruktionen, förutom att vara mer hållbar, är att befintligt mått mellan benen ska följas och att knekten ska vara staplingsbar vid transport till galvanisering. Nuvarande knektar har modellerats i CAD-programmet Pro/ENGINEER för att sedan analyseras med Finita Elementmetoden i beräkningsprogrammet ANSYS för att visa var deformation och spänningar uppstår. Efter att ett lösningsförslag tagits fram så visade det sig att maxspänningarna teoretiskt minskat och att spänningarna i kritiska områden minskat betydligt. / Örebro svets&amp; hydraulik AB manufactures cargo jacks to Suzuki Garphyttan. The large rolls of wire in steel are then transported on the cargo jacks. The cargo jacks have been shown to collapse after some time of use, and therefore needs an improved design. High loads, rough handling and careless lifting may be reasons why the cargo jack collapses. Örebro svets is well aware where the damage occurs in the current design and would like to strengthen this aspect and the construction as a whole. The requirements for the new construction, in addition to being more sustainable, are that standardized measures should be followed and that the cargo jack should be stackable for transport to galvanizing. The cargo jacks have been modeled in CAD software Pro / ENGINEER and then analyzed with Finite Element Method in the FEM calculation software ANSYS to show the deformations and tensions. After a proposed solution has been developed so it turned out that maximum tension theoretically reduced and the tension in the critical areas decreased significantly.

Abstract Axially moving material problems are concerned with the dynamic response, vibration and stability of slender members which are in a state of translation. In Finland these are particularly important in the functioning of paper machines, in which out of plane vibration in the paper web, known as flutter, which from the point of view of mechanics is a phenomenon typical of an axially moving material, limits operation speeds and therefore the productivity of the machines. This subject links together a number of physical phenomena associated with aerodynamics, web movement, material behaviour and the geometry of the system. The aim of this research is to present a theoretical and numerical formulation of the nonlinear dynamic analysis of an axially moving web. The theoretical model is based on a mixed description of the continuum problem in the context of the dynamics of initially stressed solids. Membrane elasticity is included via a finite strain model, and the membrane transport speed through a kinematical study. Hamilton's principle provides nonlinear equations which describe the three-dimensional motion of the membrane. The incremental equations of Hamilton's principle are discretized by the finite element method. The formulation includes geometrically nonlinear effects: large displacements, variations in membrane tension and variations in transport velocity due to deformation. This novel numerical model was implemented by adding an axially moving membrane element to a FEM program which contains acoustic fluid elements and contact algorithms. This allowed analysis of problems including interaction with the surrounding air field and contact between supporting structures. The model was tested by comparing previous experiments and present nonlinear description of the dynamic behaviour of an axially moving web. The effects of contact between finite rolls and the membrane and interaction between the surrounding air and the membrane were included in the model. The results show that nonlinearities and coupling phenomena have a considerable effect on the dynamic behaviour of the system. The nonlinearities cause a noticeable stiffening of the membrane, and the vibration frequency of nonlinear system increases as the amplitude grows. At high values of transport velocity the first mode frequency passes over the second linear harmonic, and even the third. The results also show that the cylindrical supports have a distinct influence on the behaviour of an axially moving sheet. The boundary of the contact region clearly moves and weakens the nonlinear hardening phenomena that otherwise increase the fundamental frequency. This influence strengthens as the radius of the cylinders increases.

The durability of a polymer trileaflet valve is dependent on leaflet stress concentrations, so valve designs that reduce stress can, hypothetically, increase durability. Design aspects that are believed to contribute to reduced leaflet stress include stent flexibility, parabolic coaptation curvature, and leaflet anisotropy. With this in mind, the purpose of this investigation was to elucidate what specific combinations of these parameters promote optimal acute and long-term valve function. A combination of four stent designs, seven leaflet reinforcement materials, and three coaptation geometries were evaluated through a combination of experimentation and modeling. Static tensile and Poisson’s ratio tests and dynamic tensile fatigue testing were used to evaluate the individual leaflet components; and hydrodynamic testing and accelerated valve fatigue was used to assess complete valve prototypes. The two most successful designs included a 0.40 mm thick knit-reinforced valve with a fatigue life of 10.35 years, and a 0.20 mm thick knit-reinforced valve with a 28.9 mmHg decrease in pressure drop over the former. A finite element model was incorporated to verify the impact of the above-mentioned parameters on leaflet stress concentrations. Leaflet anisotropy had a large impact on stress concentrations, and matching the circumferential modulus to that of the natural valve showed the greatest benefit. Varying the radial modulus had minimal impact. Varying coaptation geometry had no impact, but stent flexibility did have a marked effect on the stress at the top of the commissure, where a completely rigid stent resulted in a higher peak stress than a flexible stent (E = 385 MPa). In conclusion, stent flexibility and leaflet anisotropy do effect stress concentrations in the SIBS trileaflet valve, but coaptation geometry does not. Regions of high stress concentrations were linked to failure locations in vitro, so a fatigue prediction model was developed from the S/N curves generated during dynamic tensile testing of the 0.20 mm knit-reinforced leaflets. Failure was predicted at approximately 400 million cycles (10 years) at the top of the commissure. In vitro fatigue of this valve showed failure initiation after approximately 167 million cycles (4.18 years), but it was related to a design defect that is subsequently being changed.

Interactive dissection simulation is an important research topic in the virtual reality (VR) community. There are many efforts on this topic; however, most of them focus on building a realistic simulation system regardless of the cost, and they often require expensive workstations and specialized haptic devices which prevent broader adoption. We show how to build a realistic dissection simulation at an affordable cost, which opens up applications in elementary education for virtual dissections which are currently not feasible. In this thesis, we present a fast and robust haptic system for interactive dissection simulations of finite elements based deformable objects which supports two type of haptic interactions: point contacts and cuts. We design a semi-progressive virtual dissection scheme of deformable objects in a real-time application. The quality and performance of visual/haptic feedback is demonstrated on a low-end commercial desktop PC with a haptic device.

This thesis presents the results of an experimental, numerical and analytical study to develop a design method to calculate shear resistance of flanged ferrocement beams with vertical mesh reinforcements in the web. Two groups of full-scale testing were conducted comprising of three I beams and four U beams. The I beams had the same geometry and reinforcement arrangements, but differed in the matrix strength or shear span to depth ratio. The U beams differed in web and flange thickness, reinforcement arrangements, matrix strength and shear span to depth ratio. The experimental data were used for validation of finite element models which had been developed using the ABAQUS software. The validated models were subsequently employed to conduct a comprehensive parametric study to investigate the effects of a number of design parameters, including the effect of matrix strength, shear span to depth ratio, cross sectional area, length of clear span, volume fraction of meshes and amount of rebar. The main conclusion from the experiments and parametric studies were: shear failure may occur only when the shear span to depth ratio is smaller than 1.5; the shear strength may increase by increasing the matrix strength, volume fraction of meshes, cross sectional area and amount of rebar. The main type of shear failure for I beams was diagonal splitting while for U beams it was shear flexural. Based on the results from the experimental and numerical studies, a shear design guide for ferrocement beams was developed. A set of empirical equations for the two different failure types and an improved strut-and-tie were proposed. By comparison with the procedures currently in practice, it is demonstrated that the methodology proposed in this thesis is likely to give much better predictions for shear capacity of flanged ferrocement beams.

In this work, the load-bearing structure of a wood kiln is analyzed with the finite element method (FEM). The analysis is done with the program Inventor Nastran and consist of a linear stress and buckling analysis. The dimensions of the kiln can vary, therefore reference values are used where it is 32 m long, 12 m high and 10.5 m wide. The kiln consists of different zones that are identical to each other, these zones are separated with load-bearing structures. This structure is made up of stainless steel sheet metal with a thickness of 2-3 mm. To stabilize the kiln against wind forces, a support structure is attached on the side of the load-bearing structure.  The requirements for the strength calculations have increased in the industry. The goal is to provide a FEM model that can perform and get a realistic result. This would also lead to get a better picture of whether there are any critical areas or parts and how important the support structure is for the stability of the kiln.  A large model requires simplifications to reduce the size of the model and enable it to carry out the analysis. This means the elimination of non-structure components, symmetry by a plane, define contact surfaces, and mesh convergence. The loads acting on the kiln consisting of wind and snow are according to the Eurocode.  It is proved possible to develop a model that could perform a realistic analysis using these simplifications. A large model consisting of many parts can create uncertainty in the analysis. Therefore, some parts need to be examined more carefully and some improvements in the FEM model is required.  The weakest components in the model could be located where some reinforcement may be needed to secure the structural strength. The importance of the support structure function to strengthen the load-bearing structure of the kiln could be proven.

This diploma thesis is concerned with design and proposal of parameters of drop hammer Davon for crushing of steel reinforced concrete panels with weight of the ram 5 t. The main topic is an emergency condition when there is no crushed material between ram and anvil. The design is established by simulation of an impact by finite element analysis with respect to required ground bearing capacity.