Este trabalho foi desenvolvido como parte das atividades relacionadas ao projeto de cooperação internacional Brasil-Alemanha intitulado "Bulk metal formed parts for power plants" pertencente ao BRAGECRIM (Iniciativa Brasil-Alemanha para Pesquisa Colaborativa em Tecnologia de Manufatura), realizado em parceria entre o Laboratório de Transformação Mecânica (LdTM) da Universidade Federal do Rio Grande do Sul e o Instituto de Conformação Mecânica (IBF) da Universidade Técnica de Aachen (RWTH), Alemanha. Este projeto visa o desenvolvimento do processo de forjamento a quente em matriz aberta para a produção de um eixo vazado para aplicação em aerogeradores de energia, em substituição à eixos maciços usualmente obtidos por fundição, visando aumento de desempenho mecânico e redução de peso da estrutura. Neste trabalho buscou-se analisar, por meio de simulação numérica computacional empregando o método de elementos finitos, diferentes parâmetros de forjamento, de modo a indicar a configuração operacional que se mostra mais adequada para a produção de um eixo vazado para a aplicação pretendida. Para isto, foram realizados cinco experimentos numéricos, avaliando a influência de parâmetros de forjamento na qualidade do produto forjado. Alguns parâmetros analisados foram: a sequência operacional de forjamento, geometrias e combinações de matrizes utilizadas industrialmente, razão de mordida, etc. Para as simulações termomecânicas foi utilizado o software de Elementos Finitos PEP/Larstran acoplado ao módulo de simulação de microestrutura Strucsim. O material utilizado nas simulações foi o aço DIN 42CrMo4 (AISI 4140). Os resultados mostraram que, dentre as diferentes combinações e geometrias de matrizes analisadas, o emprego de um par de matrizes côncavas, aplicando a sequência operacional-A analisada, tende a propiciar um produto de mais alta qualidade, promovendo maior uniformidade de deformação e microestrutura mais homogênea. Também, a razão de mordida influencia diretamente na qualidade do produto, sendo que uma razão de mordida na ordem de 0,6 induz graus de deformação maiores e mais profundos na peça forjada, ao mesmo tempo em que exige maiores cargas de conformação. Comparativos entre resultados da simulação e resultados experimentais de ensaios de compressão a quente de corpos de prova cilíndricos foram realizados para validação do software de simulação numérica. Os resultados experimentais mostraram que o software de simulação numérica pode prever com boa aproximação o fluxo de material e a evolução microestrutural durante o forjamento a quente do aço DIN 42CrMo4. / This work was developed as a part of the activities related to the international cooperation project between Brazil and Germany titled "Bulk formed metal parts for power plants" belonging to BRAGECRIM (Brazil-Germany Initiative for Collaborative Research in Manufacturing Technology). This project is in partnership between the Metal Forming Laboratory (LdTM) from the Federal University of Rio Grande do Sul (UFRGS) and the Institute of Metal Forming (IBF), from Technical University of Aachen (RWTH), Germany. The project aims the development of an open die forging process to produce a hollow shaft for application in wind turbines, replacing the solid shafts usually obtained by casting, in order to increase the mechanical performance and providing weight reduction to wind turbines. The present work aimed to analyze different forging parameters, using Finite Element Method, in order to indicate most suitable forging configuration to the production of a hollow shaft. Five numerical experiments were performed, evaluating the influence of various forging parameters on the quality of the forged product, such as the forging sequence, tool geometries and tool combinations and bite ratio. For thermomechanical simulations the Finite Element software PEP/Larstran was used, coupled to the microstructure simulation module Strucsim. The material used for the numerical simulations was the DIN 42CrMo4 steel (AISI 4140). The results showed that, among the different parameters analyzed, the use of concave dies, applying the operational sequence-A, tends to provide a forged with higher quality, promoting uniform strain distribution and homogeneous microstructure. Also, results showed that a bite ratio around 0,6 provides higher and deeper strain degrees, but requires higher forming loads. Hot compression tests using cylindrical specimens were performed to validate the numerical simulation software, including microstructure evolution. Comparison between simulation and experimental results showed that the numerical simulation software can predict with good approximation the material flow and microstructure evolution during hot forging for DIN 42CrMo4 steel.

Drilled shafts are deep foundation elements created by excavating cylindrical shafts into the ground and filling them with concrete. Given the types of structures they support, failure to meet their performance criteria can jeopardize public safety and cause severe financial losses. Consequently, quality control measures are warranted to ensure these foundations meet design specifications, particularly with respect to their structural integrity and geotechnical capacity. Due to their inaccessibility, non-destructive testing (NDT) techniques have received much attention for drilled shaft quality control. However, there are limitations in the NDT tools currently used for structural integrity testing. Moreover, there is no current NDT tool to evaluate conditions underlying drilled shaft excavations and aid in verifying geotechnical capacity. The main objective of this research is to examine the development of new NDT methodologies to address some of the limitations in the inspection of drilled shaft structural integrity and geotechnical conditions underlying their excavations. The use of stress waves in large laboratory models is first examined to evaluate the performance of ray-based techniques for detecting anomalies. The study then continues to investigate the improvements offered by using a full waveform inversion (FWI) approach to analyze the stress wave data. A hybrid, multi-scale FWI workflow is recommended to increase the chance of the convergence of the inversion algorithms. Additionally, the benefits of a multi-parameter FWI are discussed. Since FWI is computationally expensive, a sequential optimal experimental design (SOED) analysis is proposed to determine the optimal hardware configurations for each application. The resulting benefit-cost curves from this analysis allow for designing an NDT survey that matches the available resources for the project. / Civil Engineering

An investigation into the load-settlement behavior of two drilled shafts, founded in shale, is presented. The motivation for this research is to advance the understanding on how drilled shafts react under loading in stiff clays and shales. The objectives of the study are to measure the strengths within the subsurface material at the test site, estimate the unit side shear and unit end bearing of the shale-shaft interaction by running two axial load tests, and compare the results to the current design methods that are used to predict the axial capacity of drilled shafts. A comprehensive field investigation, performed by Fugro Consultants, provided strength profiles of the subsurface material at the test site. Through the cooperation of the Texas Department of Transportation (TxDOT), the Association of Drilled Shaft Contractors, and McKinney Drilling Company, two drilled shafts were installed at a highway construction site in Austin, Texas. The load tests were performed by Loadtest, Inc.; using the patented Osterberg-Cell™ loading technique to axially displace the shafts. Ensoft, Inc. installed strain gauges at multiple levels within the shafts, making it possible to analyze the shaft mobilization during loading. Ultimate end bearing values of about 100- and 120-ksf were measured for Test Shafts #1 and #2, respectively. The current methods for estimating unit end bearing, developed by TxDOT and the Federal Highway Administration, provide fairly accurate predictions when compared to the measured information. The ultimate side resistance obtained near the O-Cell™ in each test was about 20-ksf, however, the measured ultimate side resistance steadily decreased nearing the tip of the shaft. For the zones where the side resistance was believed to be fully mobilized, the TxDOT design method accurately predicts the side resistance. A limited amount of information is currently available for load tests performed in soils with TCP values harder than 2-in per 100 blows. Additional load test information should allow for a stronger correlation between TCP tests and unit resistances for very hard clay-shales, as well as, allowing for further evaluation of the shale-shaft interaction near the shaft tip. The results presented herein demonstrate the effectiveness of the current design methods for drilled shafts and the non-uniformity of side resistance within one- to two-diameters of the shaft tip. / text

This thesis deals with the conceptual design of a double clutch gearbox and the inspection of selected designed parts of this gearbox. The first part of the thesis is focused on the theory of automotive transmissions and analysis of already available double clutch gearboxes. The following is the conceptual design itself, which is based on the selected vehicle on which the transmission will be located and on driving resistances. Based on these default values, the gear graduation is selected, which affects the vehicle’s driving dynamics. With regard to the installation space, a conceptual arrangement of the gearbox is proposed. Furthermore, the thesis is focused on the basic design and calculations of individual functional components of the gearbox. The last part of the thesis is involved to the control of selected structural nodes using the finite element method in the ansys workbench software. The whole thesis describes the individual steps for the design of the basic concept of a double clutch gearbox and the design of their basic components.

No description available.

Dieser Vortrag beschreibt ein methodisches Vorgehen zur Auslegung von Bauteilen, die von mehreren Eingangsgrößen und mehren Zielgrößen bestimmt sind. Als Praxisbeispiel wird eine dünnwandige Mittnehmerwelle untersucht. Im Automotivbereich besteht auf Grund der Forderungen nach Leichtbau und höherem Leistungsgewicht verstärkt der Wunsch nach einer hohen Auslastung über das ganze Bauteil hinweg. Eine Gewichtsreduktion kann durch Materialeinsparungen an unkritischen Stellen, wie zum Beispiel im Wellenkern einer Zahnwelle, erreicht werden. Die Verwendung von dünnwandigen Rohren als Ausgangsmaterial, aus denen lastangepasste Zahnprofile umformend hergestellt werden, versprechen eine deutliche Steigerung der Drehmomentübertragbarkeit bezogen auf den Materialeinsatz. Dazu wird eine neue Verzahnungsgeometrie entwickelt. Das Profil wird über eine Vielzahl an Parametern definiert, welche die Form und damit die Drehmomentübertragbarkeit beeinflussen. Durch die Verwendung einer bidirektionalen Schnittstelle kann eine Zahn-Geometrie in einem CAD-Programm mit einem FEM-Programm gekoppelt werden. Es zeigt sich, dass sich einige Geometrieparameter bereits durch die Wahl des Ausgangsrohres ergeben oder vorab festgelegt werden können. Mit vorgegebenem Außendurchmesser und Wandstärke des Ausgangsrohres sowie der Zähnezahl verbleiben bei dieser Profilform nur weitere fünf Parameter, welche hinsichtlich der Drehmomentübertragbarkeit zu optimieren sind. Mit Hilfe von numerischen Variantenberechnungen, welche sich nach den Vorgaben eines statistischen Versuchsplanes / Design of Experiments durch Veränderung der Parameter ergeben, kann ein mathematisches Ersatzmodell gebildet werden. Dieses beschreibt die (Wechsel-)Wirkungen der Eingangsgrößen auf die Ausgangsgrößen, wie zum Beispiel der Einfluss des Fußkreisdurchmessers und des Eingriffswinkels auf die dynamische Beanspruchbarkeit. Mit Hilfe von Optimierungsalgorithmen kann ein Optimum der Parameter an Hand des Ersatzmodelles ohne erneute aufwändige FEM-Berechnung gefunden werden.

Wellen und Achsen im Bereich der Antriebstechnik erfahren in den überwiegenden Anwendungen zyklische Beanspruchungen. Folglich ist für die Festigkeitsberechnung im Nennspannungskonzept eine möglichst exakte Kenntnis der Bauteilwöhlerlinie von zentraler Bedeutung. Halbzeug-Größe, Spannungsformzahl und die statischen Maximallasten beeinflussen neben weiteren Faktoren die Charakteristik der Wöhlerlinie bzw. die Dauerfestigkeit. Im Zusammenhang mit der Weiterentwicklung der Norm DIN 743 gilt diesen Größen der Fokus. Die vorliegende Arbeit betrachtet die Abschätzung der Zug-Druck-Wechselfestigkeit basierend auf dem technologischen Größeneinflussfaktor sowie der Makrohärte und deren Übertragbarkeit auf große Bauteildimensionen. In dem Zusammenhang wird der technologische Größeneinflussfaktor für Durchmesser bis 700 mm anhand einer numerisch-analytischen Simulation ermittelt und zudem mit Härtemessungen validiert. Ferner wird auf Grundlage von Treppenstufenversuchen die Abschätzung der Zug-Druck-Wechselfestigkeit aus der Härte für große Halbzeugdimensionen betrachtet. Neben dem technologischen Größeneinflussfaktor abhängig von der Härtbarkeit liegen als Ergebnisse Zusammenhänge zur Abschätzung der Zug-Druck-Wechselfestigkeit aus der Härte für große Halbzeuge vor. Darüber hinaus wird mit experimentellen Untersuchungen die Wöhlerlinie im Zeitfestigkeitsbereich analysiert. Basierend darauf werden der Wöhlerexponent sowie die Knick-Schwingspielzahl zur Dauerdauerfestigkeit in Abhängigkeit von der Formzahl abgeleitet. Abschließend widmet sich die Arbeit den Auswirkungen von statischen Maximallasten auf die Dauerfestigkeit. Dazu werden die lokalen elastisch-plastischen Beanspruchungen infolge von Maximallasten mit dem Örtlichen Konzept erfasst und in Treppenstufenversuchen die Dauerfestigkeit mit zusätzlicher Maximallast betrachtet. Ausgehend davon wird ein Konzept zur Abschätzung der lokalen Beanspruchungen sowie der lokalen Dauerfestigkeit bei Berücksichtigung des Einflusses der Maximallasten vorgestellt. / Shafts and axles of drive systems are stressed by cyclic loads in most applications. Therefore, an accurate calculation of the S-N-curve is fundamental for the system’s strength assessment based on nominal stresses. Component size, the stress concentration factor, and static loads influence the behavior of the S-N-curve and the fatigue strength, among others. In the context of a further development of the standard DIN 743, the scope is these values. This thesis focuses on the estimation of the fatigue strength for tension/compression based on the technological size factor as well as the macro hardness and their transferability to larger component sizes. In this context the technological size factor is determined by a numeric-analytical simulation for diameters up to 700 mm and is also validated with hardness measurements. Furthermore, the estimation of the fatigue strength for larger component sizes based on the hardness is supported by fatigue tests. In addition to the technological size factor depending on the hardenability, the results are obtained by an estimation approach for large components between the fatigue strength for tension/compression and the hardness. In the next step, the S-N-curve is analyzed with experimental investigations for the finite life area. Based on this, the slope of the S-N-curve (“Woehler slope”) and the knee point for the endurance limit depending on the stress concentration factor are determined. Finally, the thesis deals with the impact of static loads on fatigue strength. For this purpose, the local elastic-plastic stress-strain behavior due to static loads is calculated with the strain life assessment (local concept) and the fatigue strength influenced by static loads is analyzed as well. Based on this, an approach for the estimation of local stress-strain behavior and for the fatigue strength considering the static loads are proposed.

No / Despite being widely utilized in the production of cultural objects, keratinous hard tissues, such as horn, baleen, and tortoiseshell, rarely survive in archaeological contexts unless factors combine to inhibit biodeterioration. Even when these materials do survive, working, use, and diagenetic changes combine to make identification difficult. This paper reviews the chemistry and deterioration of keratin and past approaches to the identification of keratinous archaeological remains. It describes the formation of horn, hoof, baleen, and tortoiseshell and demonstrates how identification can be achieved by combining visual observation under low-power magnification with an understanding of the structure and characteristic deterioration of these materials. It also demonstrates how peptide mass fingerprinting of the keratin can be used to identify keratinous tissues, often to species, even when recognizable structural information has not survived.