@phdthesis{Sviridov2011, author = {Sviridov, Alexander}, title = {Leichtbau mit Aluminiumschaumsandwich : Prozessketten zur Herstellung von Bauteilen}, isbn = {978-3-86624-555-6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-23664}, school = {BTU Cottbus - Senftenberg}, year = {2011}, abstract = {Die Anforderungen an Blechhalbzeuge steigen st{\"a}ndig. Dabei sucht die blechbearbeitende Industrie nach neuen Werkstoffen mit multifunktionalen Eigenschaften, da die konventionellen Werkstoffe die gestellten Anforderungen nicht bzw. nur teilweise erf{\"u}llen k{\"o}nnen. Als innovativer Werkstoff zeigte dabei der Aluminiumschaum ein großes Potential bei der Verwendung als Komponente eines Verbundes. Dieser Verbund ist Aluminiumschaumsandwich (AFS), das aus Aluminiumblechen als Decklagen und Aluminiumschaum als Kernschicht besteht. In der vorliegenden Arbeit wurden umfassende Untersuchungen an Aluminiumschaumsandwichen durchgef{\"u}hrt und Fertigungsstrategie zur Herstellung vom praxisnahen Prototyp entwickelt. Dabei wurden neben den Umform- und Aufsch{\"a}umtechnologien auch die F{\"u}getechniken (u.a. Schweißen und Blindnieten) untersucht und erprobt. Welches Verfahren in einem einzelnen Fall besser geeignet ist, h{\"a}ngt stark von der Anwendung sowie von den gestellten Anforderungen ab. Die nachgewiesene Machbarkeit von hergestellten Bauteilen verdeutlicht das Einsatzpotential dieses innovativen Werkstoffes.}, subject = {Leichtbau; Schaumaluminium; Sandwichbauteil; Aluminiumschaum; Aluminiumschaumsandwich; AFS; Leichtbau; Prozesskette; Aluminium foam; Aluminium foam sandwich; AFS; Lightweight design; Process chain}, language = {de} } @phdthesis{Zhao2014, author = {Zhao, Dapeng}, title = {Metal Injection Moulding of Titanium-Niobium alloys for biomedical applications}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-30515}, school = {BTU Cottbus - Senftenberg}, year = {2014}, abstract = {The main subject of this work was the investigation of sintering behavior, microstructure, mechanical properties and biocompatibility of metal injection moulded (MIM) Ti-Nb alloys for biomedical applications. Commercially pure titanium (CP-Ti) samples were also fabricated by MIM as a reference. The sintering behavior of MIM Ti-Nb alloys was studied at first, in order to roughly determine the sintering parameters in the following investigations. Dilatometry was applied to investigate the linear shrinkage of MIM Ti-Nb samples from room temperature to 1500 °C at a heating rate of 3 °C/min under argon atmosphere. Various sintering parameters and Nb contents were used to investigate their influences on microstructure and mechanical properties of MIM Ti-Nb alloys by means of density measurements, optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical testing. Transmission electron microscopy (TEM) and high energy X-ray diffraction (HEXRD) measurement were applied to investigate the nature and precipitation of the unexpected titanium carbide precipitates in MIM Ti-Nb alloys. Initial cell adhesion and cell proliferation assays of human umbilical cord perivascular cells (HUCPV) on MIM Ti-Nb alloys were performed for biocompatibility characterization. The results of this work show that MIM Ti-Nb and MIM CP-Ti samples have been successfully fabricated and the as-sintered samples show good shape retention without distortion compared to the green sample. The sintering process of MIM Ti-Nb alloys consists of three main steps - Ti-diffusion step, Ti-Nb-diffusion step and Matrix-diffusion step. With increasing sintering temperatures and time, MIM Ti-Nb alloys exhibit lower porosity and higher Young's modulus. A higher Nb content in MIM Ti-Nb alloys leads to an increase of carbide area fraction and porosity. The three factors - Nb content, carbide area fraction and porosity - determine the mechanical properties of MIM Ti-Nb alloys. An increase of Nb content and amount of carbides as well as a lowered porosity lead to a higher tensile strength. A decrease of Young's modulus can be expected with higher Nb content and porosity. A high amount of titanium carbides can result in very poor ductility, but annealing and quenching process can significantly improve the elongation by dissolving the carbides. MIM Ti-Nb alloys exhibit good biocompatibility, indicating their potential for implant applications.}, subject = {Metallpulver; Spritzgießen; Sintern; Titanlegierung; Nioblegierung; Ti-Nb Legierungen; Metallspritzgießen; Sintern; Titan-Karbid; Mechanische Eigenschaft; Ti-Nb alloys; Metal injection moulding; Sintering; Titanium carbide; Mechanical behaviour}, language = {en} } @phdthesis{Gammoul2012, author = {Gammoul, Abir}, title = {Entwicklung einer Umformtechnologie zur Herstellung endkonturnaher Slicermesser}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-27228}, school = {BTU Cottbus - Senftenberg}, year = {2012}, abstract = {Slicermesser sind kreisf{\"o}rmige Scheibenmesser zum Schneiden von Lebensmittelprodukten, insbesondere Wurst, Fleisch, K{\"a}se und dergleichen. Sie werden in Hochleistungsschneidemaschinen so genannten Slicern eingesetzt und mit hoher Drehzahl von 3450 bis 5600 min-1 angetrieben. Die hohen Drehzahlen und die auftretenden Schnittkr{\"a}fte erfordern eine sehr stabile Ausf{\"u}hrung des Slicermessers. Ausgehend davon, die Messer in aufw{\"a}ndigen spanenden Herstellungsverfahren gefertigt werden m{\"u}ssen und ein relativ hohes Gewicht von 5250 g aufweisen. Der Schl{\"u}ssel zur L{\"o}sung dieser Herausforderungen hinsichtlich Stabilit{\"a}t, Steifigkeit, Gewichtseinsparung, Werkstoffeinsatz und Fertigungsaufwand k{\"o}nnte in der endkonturnahen Fertigung durch Blechumformung liegen. In dieser Arbeit wurde ein werkstoffeffizientes, aus Stahlblech herstellbares Slicermesser entwickelt. Die Umformtechnologie zur Herstellung des Slicermessers wurde realisiert. Die Funktionsf{\"a}higkeit und die technische Zuverl{\"a}ssigkeit der hergestellten Slicermesser wurden experimentell {\"u}berpr{\"u}ft und mit dem herk{\"o}mmlichen Slicermesser verglichen.}, subject = {Messer; Blechumformen; Slicermesser; Blechbearbeitung; Biegesteifheit; Gewichtseinsparung; Slicer blades; Sheet metal forming; Rigidity; Weight saving}, language = {de} } @phdthesis{Deplanque2007, author = {D{\´e}planque, Sylvain}, title = {Lifetime prediction for solder die-attach in power applications by means of primary and secondary creep}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-4275}, school = {BTU Cottbus - Senftenberg}, year = {2007}, abstract = {The objective of this thesis was to accurately check and improve the models existing for eutectic solder alloys used in simulation tools. Creep deformation,which is the most important deformation mode of solders, of two solder alloys, the widely used eutectic SnPb and the environmentally friendly alternative solder alloy SnAgCu was tested. It was shown that it is necessary to model two different stages of this high temperature induced mechanism: To improve the current material definition, primary creep must be implemented in the FE-software in addition to the existing secondary creep models. This thesis shows how it is possible to test creep behaviour under cyclic loading conditions with a test specimen of novel design. So, primary creep was observed and reoccurs cyclically under such test conditions. Furthermore, steady state creep is also always observed. A Constitutive equation combining both primary and secondary creep was given and verified. This model was implemented in FE-code Ansys, and after performing different kinds of simulation, the necessity of simulating primary creep was demonstrated. In order to achieve reliability information by FE-simulation of solder die attach, the creep-fatigue behaviour with the mean of crack propagation must be modeled. Various kinds of chips on copper substrate (power-transistors) were thermally tested, and different methods were used to investigate crack propagation. These methods were scanning acoustic microscopy and microstructure analysis by optical microscopy. The influence of damage on thermal behaviour (i.e. the thermal resistance of the device) was also assessed. These results were compared with the simulation results in order to build a lifetime prediction model based on crack propagation analysis.}, subject = {Legierung; L{\"o}ten; Kriechen; Kriechen; L{\"o}tstelle; Rissfortschritt; Lebensdauer; Leistungselektronik; Creep; Solder joint; Crack propagation; Lifetime; Power electronic}, language = {en} } @phdthesis{Soyama2014, author = {Soyama, Juliano}, title = {Development of creep resistant titanium aluminide alloys for the Metal Injection Moulding process}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-31610}, school = {BTU Cottbus - Senftenberg}, year = {2014}, abstract = {Titanium aluminides show great technological potential due to their light weight and excellent creep resistance. Their utilisation thus offers a potential to decrease fuel consumption and simultaneously improve the performance of components subjected to stress at high temperatures. However, shaping of titanium aluminides is still a very challenging and costly task considering their brittleness and the sensitivity on chemical composition. Therefore powder metallurgy near-net shape manufacturing techniques are very attractive to decrease material waste and reduce overall processing costs. This research work was focused on the preparation, characterisation and optimisation of creep resistant titanium aluminides for the Metal Injection Moulding (MIM) process. Considering the little information available regarding processing of titanium aluminides by MIM, this work had firstly the goal of assessing the creep behaviour of a reference titanium aluminide alloy. Secondly, alloy variations with compositions based on the reference material were designed with the objective of improving the creep resistance, especially concerning primary creep. The basic strengthening mechanisms applied involved the addition of slow diffusing elements and elements that cause precipitation of hard particles. The specimens were prepared by using pre-alloyed powder and mixtures of a master alloy (pre-alloyed) and elemental powders. Consequently, a great deal of effort was spent in the characterisation of the sintering behaviour in order to achieve reliable test pieces. Even though both methods can deliver sound specimens, the pre-alloyed powder approach led to the best results in terms of residual porosity and microstructural homogeneity. The mechanical testing results indicate that processing of titanium aluminides by MIM is feasible and acceptable creep properties can be achieved with the proper sintering parameters. Even though the ductility at room temperature was considerably limited due to the residual porosity and high amounts of impurities intrinsic to the MIM process, alloys developed within this study showed improved primary creep resistance in the high stress - high temperature regime. In particular alloy variations containing additions of Mo, Si and Gd led to a considerable improvement of the primary creep resistance in comparison to the reference material at 800°C - 350 MPa loading.}, subject = {Titanium Aluminides; Creep; Metal Injection Moulding; Metallpulverspritzguss; Kriechen; Titanaluminide; Titanaluminide; Kriechen; Metallpulver; Spritzgießen}, language = {en} } @phdthesis{Simon1999, author = {Simon, Sylvio}, title = {M{\"o}glichkeiten der Materialflußoptimierung an Betonmischanlagen}, isbn = {3-933342-50-3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-1515}, school = {BTU Cottbus - Senftenberg}, year = {1999}, abstract = {Station{\"a}re Betonmischanlagen sind h{\"o}chstens zu 50 \% ausgelastet. Mit zunehmender Anlagengr{\"o}ße sinkt dies Auslastung weiter, da die Zeitanteile f{\"u}r Dosieren, F{\"u}llen und Entleeren zunehmen, die Mischzeit aber konstant bleibt. Die vorliegende Arbeit beschreibt und diskutiert verschiedene M{\"o}glichkeiten, die Auslastung der Betonmischanlagen deutlich zu steigern. Je nach Anforderungen sind durch den Zweik{\"u}belaufzug, den Mischernachbeh{\"a}lter als auch durch einen neuen Mischer die gr{\"o}ßten Steigerungen m{\"o}glich. Die vorgestellten L{\"o}sungen sind sowohl f{\"u}r neue Anlagen als auch zur Rekonstruktion von Altanlagen geeignet. Als positiver Nebeneffekt kann jede Betonmischanlage nun auch effektiv als Trockenf{\"u}llstation f{\"u}r Betonmischfahrzeuge fungieren. Alle L{\"o}sungen beeinflussen nicht die in Normen, z.B. DIN 1045 festgelegte Mindestmischzeit von 30 Sekunden.}, subject = {Betonmischer; Beschicken; Dosieren; Prozessoptimierung}, language = {de} }