With flow forming – an incremental forming process – the final geometry of a component is achieved by a multitude of minor sequential forming steps. Due to this incremental characteristic associated with the variable application of the tools and kinematic shape forming, it is mainly suitable for small and medium quantities. For the extensive use of the process it is necessary to have appropriate simulation tools. While the Finite-Element-Analysis (FEA) is an acknowledged simulation tool for the modeling and optimization of forming technology, the use of FEA for the incremental forming processes is associated with very long computation times. For this reason a simulation method called FloSim, based on the upper bound method, was developed for cylindrical flow forming processes at the Chair of Virtual Production Engineering, which allows the simulation of the process within a few minutes. This method was improved by the work presented with the possibility of geometry computation during the process.

In this thesis singularly perturbed convection-diffusion equations in the unit square are considered. Due to the presence of a small perturbation parameter the solutions of those problems exhibit an exponential layer near the outflow boundary and two parabolic layers near the characteristic boundaries. Discretisation of such problems on standard meshes and with standard methods leads to numerical solutions with unphysical oscillations, unless the mesh size is of order of the perturbation parameter which is impracticable. Instead we aim at uniformly convergent methods using layer-adapted meshes combined with standard methods. The meshes considered here are S-type meshes--generalisations of the standard Shishkin mesh. The domain is dissected in a non-layer part and layer parts. Inside the layer parts, the mesh might be anisotropic and non-uniform, depending on a mesh-generating function. We show, that the unstabilised Galerkin finite element method with bilinear elements on an S-type mesh is uniformly convergent in the energy norm of order (almost) one. Moreover, the numerical solution shows a supercloseness property, i.e. the numerical solution is closer to the nodal bilinear interpolant than to the exact solution in the given norm. Unfortunately, the Galerkin method lacks stability resulting in linear systems that are hard to solve. To overcome this drawback, stabilisation methods are used. We analyse different stabilisation techniques with respect to the supercloseness property. For the residual-based methods Streamline Diffusion FEM and Galerkin Least Squares FEM, the choice of parameters is addressed additionally. The modern stabilisation technique Continuous Interior Penalty FEM--penalisation of jumps of derivatives--is considered too. All those methods are proved to possess convergence and supercloseness properties similar to the standard Galerkin FEM. With a suitable postprocessing operator, the supercloseness property can be used to enhance the accuracy of the numerical solution and superconvergence of order (almost) two can be proved. We compare different postprocessing methods and prove superconvergence of above numerical methods on S-type meshes. To recover the exact solution, we apply continuous biquadratic interpolation on a macro mesh, a discontinuous biquadratic projection on a macro mesh and two methods to recover the gradient of the exact solution. Special attentions is payed to the effects of non-uniformity due to the S-type meshes. Numerical simulations illustrate the theoretical results.

A new simple design approach will be described that utilizes test results from the Repeated Load Triaxial Apparatus to establish the risk level of permanent deformations in the unbound granular layers (UGL) in pavement constructions under consideration of the seasonal effects. From this data a serviceability limit line (plastic shakedown limit) stress boundary for the unbound granular materials (UGM) was defined for different moisture contents. Below this line the material will have stable behavior. The serviceability limit line was applied in a finite-element (FE)-program FENLAP to predict whether or not stable behavior occurs in the UGM. To calculate the stress in the UGL, a nonlinear elastic model (Dresden Model), which is described in the paper, was implemented into the FE-program. The effects of changing moisture content during Spring-thaw period and asphalt temperature on pavement structural response were investigated. Additionally, permanent deformation calculations for the UGL were performed taking the stress history into consideration. The results clearly demonstrate that, for pavement constructions with thick asphalt layers, there is no risk of rutting in the granular base, even at high number of load repetitions. The study showed that the proposed design approach is a very satisfactory simple method to assess the risk against rutting in the UGL, even without the calculation of the exact permanent deformation of the pavement construction.

The purpose of this thesis is to investigate the fatigue life of two components in different hydraulic quick couplings. The crack which initiates the fatigue failure usually occurs in the bottom of one of the threads. Thus, the threads in the coupling are carefully investigated. A few different approaches for determining the fatigue life are studied for each component. CAD (Computer Aided Design) models for both components are created and analyzed with FEM (Finite Element Method). By analyzing these components with FEM the stresses and the strains are calculated. These values for stress and strain are used to determine the fatigue life for the different components. The first component is suffering from high cycle fatigue. Four different approaches for high cycle fatigue are investigated. These four are Wöhler-curve, Haigh-diagram, von Mises fatigue criterion and Mises-Sines fatigue criterion. It was found that all of them but the von Mises fatigue criterion give a good approximation of the fatigue life. von Mises fatigue criterion does not consider the midstress, which can be a reason for this. The three other approaches indicate that the component will be suffering from fatigue, but will be relatively close to infinite life. The Wöhler-curve indicates that the component will withstand about 470 000 loading cycles. Compared to the experimental tests where the component withstands about 700 000 loading cycles, it can be said that the approach is a good estimation of the fatigue life. Approximated material data are used. For further work it is essential to obtain experimental material data for better approximation of the fatigue life. The second component is suffering from low cycle fatigue, which means that different approaches are needed. The approaches are originally from Coffin-Manson and Morrow. A total of four low cycle fatigue criterion have been studied. The first one is made by CoffinManson and takes the plastic strain in to account, the second is made by Morrow and takes both the elastic and the plastic strain in to account.  The third is a modification of Morrow’s criterion, and will consider the midstresses as well. The fourth is a simplification of Morrow’s criterion where more common material parameters are used. These four have been compared and it can be seen that the CoffinManson criterion gives the best approximation of the reality. The Coffin-Manson criterion gives an approximation of 50 000 loading cycles to fatigue failure which, compared to that the experimental tests suffered from fatigue failure after about 40 000 loading cycles, is a good estimation of the fatigue life.

In dieser Arbeit wurde das elektrochemische Korrosionsverhalten von zwei Nietverbindungen in Hybridbauweise untersucht. Auf der Grundlage von elektrochemischen Polarisationsversuchen der Nietkomponenten sowie durch Simulation mit der Methode der Finiten Elemente konnte das Korrosionsverhalten für den gefügten Zustand abgeleitet werden. Das Korrosionsverhalten für den gefügten Zustand wurde aus der grafischen Analyse der erhaltenen Stromdichte-Potential-Kurven abgeleitet. Zudem wurde in der Simulation ein kritischer Abstand für galvanisch induzierte Lochkorrosion auf der Aluminiumlegierung berechnet. Das grafisch abgeleitete sowie das berechnete Korrosionsverhalten wurden für beide Nietverbindungen im Experiment bestätigt. Weiterhin wurde ein systemspezifischer Werkstoffparameter mit einer neuentwickelten Analysemethode extrahiert und dessen Abhängigkeit von der Expositionszeit der Nietverbindungen in dem Klimawechseltest nach VDA 621-415 und dem VDA 621-414 Freibewitterungstest untersucht.

In dem Vortrag wird die Entwicklung einer Finiten-Elemente-App für Android dargelegt, sowie die Vorteile im Postprozessing von einfachen Strukturen bei der Verwendung der Gestensteuerung erörtert.

This thesis investigates the numerical simulation of three-dimensional, mechanical deformation problems in the context of large deformations. The main focus lies on the prediction of non-linearly elastic, incompressible material. Based on the equilibrium of forces, we present the weak formulation of the large deformation problem. The discrete version can be derived by using linearisation techniques and an adaptive mixed finite element method. This problem turns out to be a saddle point problem that can, among other methods, be solved via the Bramble-Pasciak conjugate gradient method or the minimal residual algorithm. With some modifications the resulting simulation can be improved but we also address remaining limitations. Some numerical examples show the capability of the final FEM software. In addition, we briefly discuss the special case of linear elasticity with small deformations. Here we directly derive a linear weak formulation with a saddle point structure and apply the adaptive mixed finite element method. It is shown that the presented findings can also be used to treat the nearly incompressible case.

In this essay, Enid Blyton’s book Five Fall into Adventure is analyzed with a focus on behavior patterns, stereotypes and power division. Intersectionality is used as an approach and a close reading of passages is used as a method. I argue that the novel could work as a good starting point for raising important questions in the classroom, despite the criticism which has been directed towards Blyton’s works. Although the way in which Blyton portrays gender stereotypes is often more acknowledged by critics, this book could be an especially useful tool when touching upon the questions of class and ethnicity. The essay also demonstrates that the criticized aspects of the books, such as them being considered sexist, should be further analyzed, emphasized and discussed, rather than suppressed, because they could serve as a good starting point for dealing with questions which are important to touch upon in teaching situations. Inequality, sexism and xenophobia are examples of such questions. / I denna uppsats analyseras Enid Blytons bok Fem går i fällan med fokus på beteendemönster, stereotyper och maktskillnader. Analysen utförs utifrån ett intersektionellt perspektiv och närläsning av avsnitt används som metod. Jag framhåller att boken skulle kunna fungera som en bra utgångspunkt för att beröra viktiga frågor i klassrummet, trots att kritik har riktats mot Blytons verk. Det är ofta Blytons sätt att skildra genusstereotyper som uppmärksammas mest av kritiker, men jag belyser att boken skulle kunna vara ett särskilt användbart verktyg för att beröra frågor rörande klass och etnicitet. Uppsatsen visar även att de kritiserade aspekterna av böckerna, exempelvis att de kan anses vara sexistiska, borde vidare analyseras, betonas och diskuteras, istället för att undvikas. Anledningen till det är att de kan användas som en väldigt bra utgångspunkt för att ta upp frågor som är viktiga att vidröra i undervisningen. Ojämlikhet, sexism och främlingsfientlighet är exempel på sådana frågor.

The goal of the current study was to develop a computational framework for modelling the coupled fluid-structure interaction problem of squeeze films often encountered in MEMS devices. Vibratory MEMS devices such as gyroscopes, RF switches, and 2D resonators often have a thin plate like structure vibrating transversely to a Fixed substrate, and are generally not perfectly vacuum packed. This results in a thin air film being trapped between the vibrating plate and the fixed substrate which behaves like a squeeze film offering both stiffness and damping to the vibrating plate. For accurate modelling of the squeeze film effect, one must account for the coupled fluid-structure interaction. The majority of prior works attempting to address the coupled problem either approximate the mode shape of the vibrating plate or resort to cumbersome iterative solution strategies to address the problem in an indirect way. In the current work, we discuss the development of a fully coupled finite element based numerical scheme to solve the 2D Reynolds equation coupled with the 3D plate elasticity equation in a single step. The squeeze film solver so developed has been implemented into a commercial FEA package NISA as part of its Micro-Systems module. Further, extending on a prior analytical work, the effect of variable ow boundaries for an all sides clamped plate on squeeze film parameters has been thoroughly investigated. The developed FEM based numerical scheme has been used to validate the results of the prior analytical study. The developed numerical scheme models the 2D Reynolds equation thus limiting the model to account for the effects of the fluid volume strictly confined between the structure and the substrate. To study the effect of surrounding fluid volume ANSYS FLOTRAN simulations have been performed by numerically solving the full 3D Navier Stokes equation in the extended fluid domain for the different flow boundary scenarios. Cut-off frequencies are established beyond which one can consider a 2D fluid domain without considerable loss of accuracy. First, a displacement based finite element formulation is presented for the 2D Reynolds equation coupled with the 3D elasticity equation. Both lower order 8 node and higher order 27 node 3D elements are developed. Only a single type of 3D element is used for modelling along with a 2D fluid layer represented by the \wet" face of the 3D structural domain. The results from our numerical model are compared with experimental data from literature for a MEMS cantilever. The results from the 27 node displacement based elements show good agreement with published experimental data. The results from the lower order 8 node displacement based elements however show huge errors even for relatively fine meshes due to locking issues in modelling high aspect ratio structures. This limits the implementation of the displacement based solver in commercial FE packages where the available mesh generators are generally restricted to lower order 3D elements. In order to overcome the limitations faced by lower order elements (primarily locking issues) in modelling high aspect ratio MEMS geometries, a coupled hybrid formulation is developed next. A thorough performance study is presented considering both the hybrid and displacement based elements for lower order 8 node and higher order 27 node ele- ments. The optimal element choice for modelling squeeze film geometries is determined based on the comparative studies. The effect of element aspect ratio for hybrid and displacement based elements are studied and the superiority of hybrid formulation over displacement based formulations is established for lower order 8 node elements. The coupled hybrid nite element formulation developed for lower order elements is implemented in the commercial FEA package NISA. The implementation scheme to integrate the developed coupled hybrid 8 node squeeze film solver into the commercial FEA package is discussed. The pre-integration analysis and subsequent requirement gaps are first investigated. Based on the gap analysis, certain GUI modifications are undertaken and parser programs are developed to re-format data according to NISA input requirements. Certain special features are included in the package to aid in post processing data analysis by MEMS designers such as \frequency sweep" and \node of interest" selection. As a case study for validation, we also present the modelling of a MEMS cantilever and show that the simulation results from our software are in good agreement with experimental data reported in the literature. Finally as a case study, an extension of a prior analytical work, which studies the effect of varying flow boundaries on squeeze film parameters, is discussed. Explanations are provided for the findings reported in the prior analytical work. The concept of using variation in flow boundaries as a frequency tuning tool is introduced. The analytical results are validated with the coupled numerical scheme discussed before, by considering imposed mode shape for an all sides clamped plate as prescribed displacement to the fluid domain. The simulated results are used to study the intricacies in squeeze film damping and stiffness variations with respect to spatial changes in the fluid flow boundary conditions. In particular, it has been shown that the boundary venting conditions can be used effectively to tune the dynamic response of a micromechanical structure over a fairly large range of frequencies and somewhat smaller range of squeeze film damping. Next, the effect of the surrounding fluid volume for various venting conditions is studied. ANSYS FLOTRAN is used to solve for the full 3D Navier Stokes equation over the extended fluid domain. Results from the extended domain study are used to determine cut-off frequencies beyond which one need not resort to an extended mesh study, and yet be within 5% accuracy of the full extended mesh model.

Konstruktörer i dagens läge kommer in i projekten väldigt sent samtidigt som dom får allt färre timmar att projektera med. Detta har resulterat i att programvaror rörande beräkningar och konstruktion har fått ett allt större fokus och en högre efterfrågan, samtidigt som kunskapen rörande användningen av dessa program är fortsatt förhållandevis låg.Konstruktionsavdelningen på Strängbetong i Örebro använder idag en kombination av MathCAD, Excel och handberäkning för sina projekt. Reflektion har gjort angående om hur det går att använda program som StruSofts FEM-Design vilket nyttjar finita elementmetoden till sina beräkningar. Avdelningen är dock skeptiskt mot programmets komplexitet och dess resultat från tidigare projekt.Arbetets syfte är analysera stomstabiliteten av ett flerfamiljehus bestående av prefabricerade element utifrån fyra olika metoder med hjälp av FEM-Design. Tre av metoderna är statiska sätt att se på en byggnad medans den fjärde metoden är en förenkling som görs vid traditionell handberäkning. Frågan som undersöks är hur stora skillnaderna blir mellan dessa fyra olika metoder och varför detta inträffar. Stabiliteten analyseras globalt med enbart fokus på jämvikt mot stjälpning.Byggnaden modelleras upp i FEM-Design och analyseras utifrån fyra olika metoder: elasticitetsteori med hänsyn till första ordningens moment, elasticitetsteori med hänsyn till andra ordningens moment, plasticitetsteori och utifrån utredda förenklingar som görs vid en beräkning för hand. För att erhålla ett så realistiskt resultat som möjligt deltog författarna i en två dagars kurs i FEM-Design. Författarna har även spenderat en stor del av tiden i att undersöka hur programmet reagerar på inställningar och laster, för att säkerställa realism och ett korrekt utförande.Resultatet som erhålls är att det förekommer allt från markanta till mindre skillnader mellan metoderna beroende på fall av belastning. Inget generellt ”värsta fall” förekommer utan analyserna innebär att olika kritiska punkter uppstår. Utifrån detta bör samtliga analyser utföras och byggnad ska klara att vara stabil under respektive analys. Del av resultatet är även metoden som tydligt presenteras av hur en stabilitetsanalys i FEM-Design bör utföras på en stomme som består utav prefabricerade element. / Structural engineers nowadays enter projects in the late stages while also receiving fewer hours to do the project planning with. This has led to a shift of focus onto software development and an increase in demand of structural design and calculation software. As this is developing there is still a lack of knowledge regarding how they should be used.The structural division at Strängbetong Örebro are today using a combination of MathCAD, Excel and hand calculation for their precast projects. They have also explored the possibilities of using StruSofts finite element software FEM-Design for their calculations. The structural division remains sceptical due to the complex nature of the program and experiences from previous projects using the software.The purpose of this study is to build an apartment building composed of prefabricated elements and analyse the structural stability of the building using four different methods aided by the software FEM-Design. The program itself relies on the finite element method to solve its calculations. Three of the methods are static ways to view a building while the fourth method is a simplification used for hand calculation the traditional way. The focus of the stability analysis is the overturning of said building. The questions to be answered by this study is how big the difference is between these four methods and why it exists.The building is modelled in FEM-Design and analysed using four different methods: first order elasticity theory, second order elasticity theory, limit load theory and simplifications made using traditional hand calculation. To obtain a reliable result the authors attended a two day course about structural design in FEM-Design. The authors also spent a great amount of time experimenting with the program with a purpose to obtain knowledge of how it works and reacts to a combination of different loads and conditions.The obtained result showcased everything from a minor to a significant difference in results between the methods depending on load case in question. No obvious “worst case scenario” is presented as every analysis results in its own critical scenarios. The conclusion is that each of the methods has its place and should be done to secure the stability of building in question. Additionally, part of the result is the instruction presented of how a stability analysis on a prefabricated framework should be performed with FEM-Design.