This thesis deals with analysis of mechanical and thermal load of a diesel engine cylinder head with fatigue life prediction. In the first part common solution options are described. The second part contains stress, deformation and fatigue life prediction computation of the given diesel engine cylinder head.

Welding is a widely used method of connecting components because of its efficiency, great value and almost endless possibilities of join types. A great variability of geometrical configurations of welds is problematic due to the assessment of the weld joint. Depending on this topic this thesis was focused on the assessment of weld joints statically and cyclically. Work in the first part deals with the search of methods for evaluation of welds and depending on identified options is subsequently selected American standard AISC assessment of welded joints. The method is applied into FEA analysis and simple welded joints are evaluated. Using FEM are computed three examples on which a comparative analysis was performed. Comparisons were made with the analytical solution based on changes in the parameters of the computational model. The change is primarily related to material properties, mesh size and division of the weld on segments. On the basis of knowledge from analysis of simple joints, method was extended to more general welded joints with the possibility of determining the maximum loading force.

Knowledge about the dynamic behaviour is a basic condition for a secure operation of modern machine tools. Hence numerical methods predicting the dynamic properties are gaining in importance. Usually for complex and coupled structures, the results of dynamic property calculation are yet insufficient. Therefore Finite Element model updating is a tool to improve the hypothetical factor of the analysis. Within the present thesis Finite Element modelling is performed using the example of the “Scherenkinematik”, a machine tool based on hybrid-kinematics. Initially the results of an Experimental Modal Analysis are evaluated by identifying Modal parameters and deriving possible structural modifications. In the second part of the thesis, the machines Finite Element model is created using the FEA-Software ANSYS. Afterwards the Finite Element model updating is performed by coupling ANSYS and the CAE-Software FEMtools. Therefore two approaches are formulated and tracked. It turns out, that there is no improvement of the analytical and experimental models correlation, neighter with nor without a steady reduction of the search domain needed for mode coupling. It is reasoned, that the characteristics and the results of an Finite Element updating process are affected by the quality of the model at start time and the approach as well as the technique chosen for model updating and parameter modification. Therefore the CAE-Software FEMtools is suitable to only a limited extent for Finite Element updating of strongly coupled mechanical structures as a result of the sensitivity analysis used for parameter modification.

This thesis is on fatigue crack growth assessments of a thermomechanical loaded Marine Boiler- Sunrod CPDB12. The installation position of the marine boiler in the ship in relation to its fatigue life under mode 1 loading is investigated. Thermomechanical loading embodies pressures, temperatures, RAO, subjected to the rigid body dynamic of ship in the marine environment.   Linear elastic fracture mechanics (LEFM) method was used is predicting the growth rates of the welding flaws at the joint based on stress range of the Paris law relationship. FEA Numerical simulation delivered better crack growth rate assessments and life predictions of the smallest detectable flaws in the boiler.   The identified smallest detestable flaws at the welding joint diminishing the designed safe life of the boiler significantly.  Also, installation position within the ship do affect the fatigue life of the boiler.

Operationally, marine components and structures such as boiler in a Ship, are exposed to varying mechanically and thermally induced forces. High-frequency mechanical loading arises from the cyclic pressure, temperature transients, and six directional Rapid Amplitude Operator (RAOs). These types of loadings are mainly in the elastic region usually denoted as high cycle fatigue (HCF), most pronounced during the start-up, and the shut-down sequence of operation, which are responsible for an astronomically  reduction in Marine Boiler’s lifetime as compared to land boiler with same designed operating condition. Therefore, there is a need to determine the limitations of the engineering variables of the boiler with respect to Pressure, temperature, RAOs, and best locational point for the optimization of its designed lifetime during Operation. Detailed knowledge of this interaction between varying temperatures, RAOs and load cases is of considerable importance for precise lifetime calculations.  In order to understand and analyze the material behavior under contentious stress exposure, a general-purpose linear Finite Element (FE) code, LS-DYNA software is used as a pre-processor and solver during the simulation and data are post-processed using stress-based analysis method.

The aim of the project is to develop a model, which is going to be used for mass reduction of a standard profile of aluminium seat rails in Aircraft structure. Using nonlinear analysis including plasticity and material failure laws the effect of changes in geometry vs. ultimate load is analysed (ABAQUS 6.11). First, the non-linear model used is validated with experimental testing: Boundary conditions and material properties are adjusted based on load displacement curves, strain gauges information and failure patterns. Less than 1% deviation is achieved between simulation and testing. An inclusion of material imperfection led to a 5% improvement of the results. Using the validated algorithm, a mass reduction is performed via geometry variation. / Ziel der Studie ist es ein adäquates Simulationsmodell zu entwickeln, welches zur Gewichtsreduzierung einer Standardprofil Aluminium Sitzschiene im Flugzeug verwendet werden kann. In einer nichtlinearen Analyse unter Berücksichtigung der Plastizität des Materials und von Materialfehlern wird die Auswirkung der Geometrieänderungen auf die maximale Traglast analysiert (ABAQUS 6.11). Zunächst wird das nicht-lineare Modell mit experimentell ermittelten Daten überprüft: Randbedingungen und Materialeigenschaften werden basierend auf Lastverschiebungskurven, Informationen von Dehnungsmessstreifen und Versagensmustern angepasst. Dabei wurden weniger als 1% Abweichung zwischen Simulation und Test erzielt. Die Berücksichtigung von Materialfehlern führte zu einer 5%-igen Verbesserung der Ergebnisse. Mit dem validierten Modell wird abschließend eine Gewichtsreduzierung mittels Geometrievariation durchgeführt.

Die Finite Elemente Analyse hat sich in vielen industriellen Anwendungsgebieten zu einem elementaren Werkzeug für den Produktentwicklungsprozess entwickelt. Zu diesen Anwendungsbereichen zählen u. a. der Fahrzeugbau, die Medizintechnik und der Sondermaschinenbau. Neben Strömungssimulationen und der numerischen Berechnung von elastomechanischen Strukturen sind auch thermomechanische Analysen mithilfe der FEA durchführbar. Kleine und mittelständische Unternehmen können jedoch nicht immer auf einen wirtschaftlichen Einsatz von kommerziellen FEA-Tools zurückgreifen und sind folglich auf Freeware Programme wie Z88Aurora® angewiesen. Die häufig für den Entwickler interessierende stationäre Wärmeleitung und die aus dem Temperaturunterschied resultierende thermische Dehnung von Bauteilkomponenten gehören längst zum Tagesgeschäft. Für eine realitätsnahe Auslegung von beispielsweise Kühlkörpern oder Rippen muss zusätzlich die konvektive Wärmeübertragung berücksichtigt werden. Hierbei wird der Wärmetransport zwischen einer Bauteiloberfläche und dem Umgebungsmedium, wie z. B. Luft oder Kühlwasser, untersucht. Diese erweiterte Abbildung der Temperaturanalyse definiert als Randbedingung eine Wärmestromdichte auf einer Bauteiloberfläche, welche proportional zur Temperaturdifferenz beider Systemkomponenten ermittelt wird. Zudem gehen nichtlineare Einflüsse aus den Materialeigenschaften des Fluids und aus dem entstehenden Strömungsverhalten über den sog. Wärmeübergangskoeffizienten in die Simulation ein. Aufgrund dieser Komplexität kann über empirisch ermittelte Korrelationsgleichungen die Bestimmung des Wärmeübergangskoeffizienten erreicht werden. Diese Erweiterung des Thermomoduls wird in der neuen Version von Z88Aurora®V5 dem Anwender zur Produktentwicklung angeboten. Eine für den industriellen Einsatz essentielle Validierung der Berechnungsergebnisse wird über analytische Vergleichsrechnungen am Beispiel einer Kühlrippe nachgewiesen.

Med strängare krav på miljöpåverkan och en konstant efterfrågan på högre prestanda är optimering en essentiell del av vår vardag. Genom korrekt arbetsmetodik och optimering kan den växande efterfrågan på både prestanda och minskad miljöpåverkan överträffas. Att utveckla ett optimalt koncept av en länkarm hos en prestandabil är ett konkurrenskraftigt steg med stor betydelse. Genom att i ett tidigt skede i produktutvecklingsprocessen kunna skapa en optimal design minskar risken för stora kostnader på grund av ändringar i de senare faserna och bidrar således till en ökad lönsamhet. Att utnyttja Finita Elementmetoden som en del av en CAE driven produktutvecklingsprocess är således en utmärkt väg att gå och bidrar starkt till ändamålet genom att lösa avancerade problem med en simpel och adaptiv metodik. Bilindustrin präglas av innovativa och effektiva lösningar där både FEM och RE är välkända metoder. Projektet ska upplysa innebörden av en strukturerad arbetsmetodik vid optimering genom implementering av ett flertal produktutvecklingsfilosofier kombinerat med FEM/FEA. Genom att optimera en länkarm från en Audi R8 Coupé V10 quattro tillämpas och utvecklas välfungerade och starkt begrundade metoder. Produktutvecklingsfilosofier såsom Reverse Engineering och ett iterativt arbetssätt resulterade i en förbättrad länkarm med lägre vikt såväl som minskade spänningar och deformation. En viktminskning på 22%, en spänningsminskning på 47% och en minskad teoretisk elastisk deformation på 33% uppnåddes. Utöver dessa förbättringar ökade även robustheten med 25%. / With harsher regulations of environmental impact combined with a consistent demand on increased performance, optimization becomes an essential part of our everyday lives. Through a well-developed methodology and optimization process, the tougher demands of both performance and environmental impact could be exceeded. Developing an optimal concept of a control arm in a high-performance vehicle application is a competitive step of great importance. By creating an optimal design in early development stages of the product development process, the economic impact could be minimized. This therefore leads to an increase in profitability. Involving the Finite Element Method as a part of the product development process is therefore an excellent path toward solving advanced problems through a simple and adaptive work methodology. The automotive industry is characterized by innovative solutions where both the Finite Element Method and Reverse Engineering are well-known methods. The project has a foundation that strongly represents the meaning of a systematical optimization methodology through various product development philosophies combined with FEM/FEA. Through optimization of a control arm from an Audi R8 Coupé V10 quattro proved and well-grounded methods are applied and further developed. Product development philosophies such as Reverse Engineering and an iterative work process resulted in an improved control arm with lower weight as well as decreased stresses and deformation. A weight loss of 22%, stress reduction of 47% and a reduced theoretical elastic deformation of 33% was achieved. Beyond these improvements an increased robustness of 25% was achieved.

Composite sandwich structures are being used in the automotive and aerospace industries at an increasing rate due to their high strength and stiffness per unit weight.  Many teams in the world’s largest engineering competition for students, Formula Student, have embraced these types of structures and are using them in their chassis with the intent of increasing the torsional stiffness per unit weight.   The Formula Student team at Karlstad University, Clear River Racing, has since 2017 successfully built three carbon fiber based sandwich structure chassis. A big challenge when designing this type of chassis is the lack of strategy regarding torsional stiffness simulations. Thus, the goal of this thesis project was to provide the organization with a set of accurate yet relatively simple methods of modelling and simulating the torsional stiffness of the chassis.   The first step in achieving the goal of the thesis was the implementation of simplifications to the material model. These simplifications were mainly targeted towards the aluminum honeycomb core. In order to cut computational times and reduce complexity, a continuum model with orthotropic material properties was used instead of the intricate cellular structure of the core. To validate the accuracy of this simplification, the in-plane elastic modulus of the core was simulated in the finite element software Abaqus. The stiffness obtained through simulations was 0.44 % larger than the theoretical value. The conclusion was therefore made that the orthotropic continuum model was an accurate and effective representation of the core.   Furthermore, simplifications regarding the adhesive film in the core-carbon fiber interfaces were made by using constraints in Abaqus instead of modelling the adhesive films as individual parts. To validate this simplification and the overall material model for the sandwich structure, a three-point bend test was simulated in Abaqus and conducted physically. The stiffness for the sandwich panel obtained through physical testing was 2.4 % larger than the simulated stiffness. The conclusion was made that the simplifications in the material modelling did not affect the accuracy in a significant way.   Finally, the torsional stiffness of the 2020 CFRP chassis was found to be 12409.75 Nm/degree.   In addition to evaluating previously mentioned simplifications, this thesis also serves as a comprehensive guide on how the modelling of the chassis and how the three-point bend test can take place in regards to boundary conditions, coordinate system assignments and layup definitions.

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