V posledních několika desetiletích se objevuje snaha o snížení firemních nákladů, stejně tak jako nákladů, které je nucen vynaložit zákazník, čímž se společnosti snaží získat výhodu vůči svým konkurentům na trhu. Spolu s tímto trendem jde i neustálá snaha snížit dopady na životní prostředí. Vývoj stávajících produktů se proto zdá být klíčovým prvkem. Tento dokument se zabývá vývojem pístového kompresoru na CO2 chladivo, který vyrábí společnost Emerson Climate Technologies. Cíl práce je zvýšit COP kompresoru při zachování stávající životnosti kompresoru. Diplomová práce je rozčleněna do několika kapitol, které se zabývají analýzou originálního designu kompresoru, návrhem a vyhodnocením designů nových. Nezbytné teoretické základy mohou být také shlédnuty v počátečních kapitolách. V poslední části dokumentu jsou sdělena možná další vylepšení a případné jiné konstrukce. Vývoj byl zaměřen na sestavu ventilové desky. Na základě několika předpokladů a výsledků analýzy původního designu kompresoru byly navrženy nové konstrukce, které byly dále testovány statickou strukturální analýzou. Pomoci modální analýzy byly také vypočteny vlastní frekvence a vlastní tvary sacího jazýčku. Mimo modální a statické strukturální analýzy byla provedena také CFD analýza. V posledním kroku byly testovány navržené prototypy a jejich výsledky byly porovnány s původním kompresorem. K správnému návrhu bylo zapotřebí programové podpory a to především v podobě MATLABu, ANSYSu WB a Microsoft Excelu. V práci jsou velmi často prezentovány obzvláště výsledky získané v programu ANSYS WB.

This dissertation thesis consists rotordynamics of modern turbocharger. First part begins with prediction of critical speed, prediction of onset instability of oil whirl and oil whip by XLTRC2 and comparison with measured data (Cascade diagram, shaft motion, FFT analysis). List of measurement method for the detection of the natural frequency of turbocharger (EMA). Create software for long term monitoring and recording and output data size reduction. Detection of critical speed by defined measurement methodology without using software simulation with measured data from the Cascade diagram, move the rotor shaft motion in the bearing, FFT analysis and results from measurements of natural frequencies. Comparison of predicted data (critical speed, prediction of onset instability) program XLTRC2 with the values measured by this approach measurement (waterfall diagram, shaft motion, FFT analysis)

Diploma thesis deals with static and dynamic analysis of a wooden arch footbridge. The computational model of the structure was created in ANSYS 15. Dynamic forces from wind and horses were applied to the model based on the modal analysis. The effects of these forces at resonance were evaluated by harmonic analysis.

The aim of this diploma thesis is to evaluate the potential of available methods for simplification and reduction of complex models of technical systems and their integration with experimental models. Finding methods, which would allow us to create models and run simulations in shorter periods of time, is key in design process of modern technical systems. In the beginning of this thesis, a theory necessary for understanding and application of presented methods is given. These methods can be separated into two groups, first as experiment related, second as simulation related. The first group contains methods for experimental evaluation of response and its use for dynamic system identification. The second group contains methods of finite element model creation, with the usage of standard structural elements as well as Component Mode Synthesis substructures, and these models are in the following step reduced into state space models. In the next step, all presented methods are applied on simple experimental structure. In conclusion, the results of simulations are the subject for comparison not only from quantitative point of view, but also, for the purpose of practical application, in terms of time, feasibility, versatility and accuracy. The system identification method along with state space method proved to be very suitable. The results presented in this thesis might help, by selecting the appropriate method, in simpler evaluation of dynamic properties of technical structures.

This diploma thesis aims to design a structure of pedestrian bridge over the Svratka river. To make a preliminary study of possible bridging, three different outlines were drafted. The cable-stayed variant was selected for further analysis. Two towers, inclined in both their longitudinal and transverse direction, support a cast-in-place post-tensioned concrete deck through stay cables anchored in the tower and the deck. After determining the desired initial state, a finite element analysis was carried out using the Ansys software. The capacity of all main load-bearing elements was checked so it meets the ULS and SLS design criteria in accordance with EN 1992 codes.

L'objectif de cette thèse est de simuler l'histoire temporelle de la réponse d'un bâtiment de grande hauteur sous sollicitation sismique et de proposer des méthodologies simplifiées qui reproduisent correctement une telle réponse. Initialement, un modèle tridimensionnel par éléments finis est produit afin de valider sa fiabilité pour simuler le comportement réel du bâtiment pendant les mouvements du sol, enregistrés à l'aide d'accéléromètres. Il est proposé d'améliorer la précision du modèle numérique en imposant de multiples excitations, compte-tenu des effets de basculement et de la variabilité spatiale sur la sollicitation d'entrée. L'utilisation de fonctions de Green empiriques est proposée pour simuler la réponse sismique directement à partir d'enregistrements d'événements passés, sans avoir besoin de dessins de construction ni d'étalonnage des paramètres mécaniques. Une méthode de sommation stochastique, déjà utilisée pour prédire les mouvements du sol, est adoptée pour générer des signaux synthétiques à des hauteurs différentes du bâtiment, par extension du chemin de propagation des ondes du sol à la structure. Une représentation simplifiée du bâtiment comme une poutre homogène Timoshenko est proposée pour simuler la réponse sismique directement à partir des enregistrements des vibrations ambiantes. Des paramètres mécaniques équivalents sont identifiés à l'aide de l'interférométrie par déconvolution en termes de dispersion des ondes, de fréquences naturelles et de rapport de vitesse des ondes de cisaillement et de compression dans le milieu / The aim of this thesis is to simulate the time history response of a high rise building under seismic excitation and provide simplified methodologies that properly reproduce such response. Firstly, a detailed three-dimensional finite element model is produced to validate its reliability to simulate the real behavior of the building during ground motions, recorded using accelerometers. It is proposed to improve the accuracy of the numerical model by imposing multiple excitations, considering rocking effect and spatial variability on the input motion. The use of empirical Green's functions is proposed to simulate the seismic response directly from past event records, without the need of construction drawings and mechanical parameters calibration. A stochastic summation scheme, already used to predict ground motions, is adopted to generate synthetic signals at different heights of the building, extending the wave propagation path from the ground to the structure. A simplified representation of the building as a homogeneous Timoshenko beam is proposed to simulate the seismic response directly from ambient vibration records. Equivalent mechanical parameters are identified using deconvolution interferometry in terms of wave dispersion, natural frequencies and shear to compressional wave

This paper presents a method of parameter identification for a finite-element model of the human middle ear. The parameter values are estimated using a characterization of the difference in natural frequencies and mode shapes of the tympanic membrane between the model and the specimens. Experimental results were obtained from temporal bone specimens under sound excitation (300–3,000 Hz). The first 3 modes of the tympanic membrane could be observed with a laser scanning vibrometer and were used to estimate the stiffness parameters for the orthotropic finite-element model of the eardrum. A further point of discussion is the parameter sensitivity and its implication for the identification process. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Der neu entwickelte Multiaxiale Räderprüfstand wurde für hoch dynamische Radkräfte konzipiert. Das Prüfstands-Konzept basiert auf einer Parallelkinematik im Hexapoden-Design. Die Auslegung der Kinematik und der Kräfte wurde mit Creo MDO/MDX durchgeführt. Die grundsätzliche Vorgehensweise wird anhand von Beispielen aufgezeigt. Aufgrund der hohen Dynamik ist es erforderlich das maschinendynamische Verhalten bei der Auslegung zu berücksichtigen. Dazu wurde ein Simulationsmodell des gesamten Prüfstandes in Creo Simulate erstellt und entsprechende Modal- und dynamische Frequenzanalysen durchgeführt. Der grundsätzliche Modellaufbau und Simulationsergebnisse werden vorgestellt. Auch auf die Verifizierung durch Messungen wird eingegangen. Letzter Punkt ist das Ableiten eines geeigneten Sub-Simulations-Modells, welches den Kraftfluss der Hexapoden-Architektur für weitere Untersuchungen richtig abbildet.

In the design of a railway bridge that is meant for train speeds larger than 200 km/h, the Swedish Traffic Administration requires a dynamic analysis in addition to the conventional static design. The models used for static design may not always be suitable for dynamic analysis, which could lead to inaccurate estimations of the dynamic response. The reason for this is a limited knowledge of the actual structural dynamic behaviour of bridges, which is why a hydraulic bridge exciter has been developed. With this device, smaller bridges can be excited in a load- or displacement-controlled manner under variable frequency and load. By having known inputs, the bridges’ dynamic properties can be evaluated using experimental modal analysis. A finite element model of the double tracked railway bridge Pershagen was created in order to plan a pilot test of the bridge exciter. The influence of the load amplitude and sweep rate was evaluated. A theoretically optimal excitation position was also investigated in order to excite as many eigenmodes as possible from one position during the pilot test. Based on these results, a pilot test was performed on the Pershagen Bridge. The dynamic properties of the bridge were evaluated based on the results from the test. From the pilot test it could be concluded that the load amplitude had a direct influence on the dynamic properties of the bridge, hence the dynamic behaviour is non-linear. The 1st vertical bending mode and its dynamic properties could also be identified. / Då en järnvägsbro som är avsedd för tåghastigheter över 200 km/h ska dimensioneras ställs det krav av Trafikverket att en dynamisk analys av bron skall utföras, utöver konventionell statisk dimensionering. De bromodeller som används för statisk analys är dock inte alltid lämpliga för dynamisk analys, vilket kan leda till felaktiga skattningar gällande den dynamiska inverkan. Anledningen till detta är att kunskapen om broars dynamiska egenskaper är begränsade, och av denna anledning har en lastexciterare utvecklats. Med hjälp av denna anordning kan mindre broar exciteras med kontrollerad last eller förskjutning under variabel frekvens och last. Då dessa input-parametrar är kända kan broars dynamiska egenskaper utvärderas genom experimentell modal analys. En finit element-modell av den tvåspåriga järnvägsbron vid Pershagen har skapats för att kunna planera ett pilottest av lastexciteraren. Svephastigheten och lastamplituden har analyserats. En teoretiskt optimal exciteringsposition har utvärderats för att excitera största möjliga antal moder från en och samma position under pilottestet. Utifrån dessa resultat utfördes ett pilottest på bron vid Pershagen, där brons dynamiska egenskaper utvärderades utifrån resultaten. Från pilottestet kunde en slutsats dras om att lastamplituden hade en direkt inverkan på de dynamiska egenskaperna, vilket betyder att det dynamiska beteendet är olinjärt. Den första vertikala böjmoden och dess dynamiska egenskaper kunde också fastställas.

Design space exploration (DSE) is a tool used to evaluate and compare designs as part of the design selection process. While evaluating every possible design in a design space is infeasible, understanding design behavior and response throughout the design space may be accomplished by evaluating a subset of designs and interpolating between them using surrogate models. Surrogate modeling is a technique that uses low-cost calculations to approximate the outcome of more computationally expensive calculations or analyses, such as finite element analysis (FEA). While surrogates make quick predictions, accuracy is not guaranteed and must be considered. This research addressed the need to improve the accuracy of surrogate predictions in order to improve DSE of structural responses. This was accomplished by performing comparative analyses of linear and nonlinear dimensionality-reduction-based radial basis function (RBF) surrogate models for emulating various FEA nodal results. A total of four dimensionality reduction methods were investigated, namely principal component analysis (PCA), kernel principal component analysis (KPCA), isometric feature mapping (ISOMAP), and locally linear embedding (LLE). These methods were used in conjunction with surrogate modeling to predict nodal stresses and coordinates of a compressor blade. The research showed that using an ISOMAP-based dual-RBF surrogate model for predicting nodal stresses decreased the estimated mean error of the surrogate by 35.7% compared to PCA. Using nonlinear dimensionality-reduction-based surrogates did not reduce surrogate error for predicting nodal coordinates. A new metric, the manifold distance ratio (MDR), was introduced to measure the nonlinearity of the data manifolds. When applied to the stress and coordinate data, the stress space was found to be more nonlinear than the coordinate space for this application. The upfront training cost of the nonlinear dimensionality-reduction-based surrogates was larger than that of their linear counterparts but small enough to remain feasible. After training, all the dual-RBF surrogates were capable of making real-time predictions. This same process was repeated for a separate application involving the nodal displacements of mode shapes obtained from a FEA modal analysis. The modal assurance criterion (MAC) calculation was used to compare the predicted mode shapes, as well as their corresponding true mode shapes obtained from FEA, to a set of reference modes. The research showed that two nonlinear techniques, namely LLE and KPCA, resulted in lower surrogate error in the more complex design spaces. Using a RBF kernel, KPCA achieved the largest average reduction in error of 13.57%. The results also showed that surrogate error was greatly affected by mode shape reversal. Four different approaches of identifying reversed mode shapes were explored, all of which resulted in varying amounts of surrogate error. Together, the methods explored in this research were shown to decrease surrogate error when performing DSE of a turbomachine compressor blade. As surrogate accuracy increases, so does the ability to correctly make engineering decisions and judgements throughout the design process. Ultimately, this will help engineers design better turbomachines.