Untersuchung verschiedener Schweißverfahren für die Nickel-Basislegierung NiMo 16 Cr 16 Ti

Investigation of Different Welding Processes with Nickel-Alloy NiMo 16 Cr 16 TI The overall favourable corrosion resistance of the nickel-chromium-molybdenum alloy NiMo 16Cr 16 Ti against attack by powerful oxidizing acids ensures a wide field of applications for this material. The alloy is readily processable using encased rod electrodes and shielded are welding. However, shielded arc welding should be given preference, as there are considerable differences in the analytical results between smelted welded material from encased rod electrodes and bright rods and wires. The different welded materials influence the corrosion resistance and the possibilities of forging welded constructions.     

Messung schneller Druckänderungen im Grobvakuumbereich

Measurement of fast pressure changes in the rough vacuum range Using commercially available vacuum gauges, pressure jumps executed in the millisecond range between 1000 and just below 1 mbar were measured in a specially developed system. Of the investigated vacuum gauges, the piezoresistive devices had the shortest response times. They reacted within 1 – 5 ms and achieved a valid measured value after approximately 20 ms. The capacitive manometers responded after 5 – 20 ms and reached a valid measured value after 50 – 100 ms. Lower‐priced Pirani gauges reacted with a response time of 50 – 100 ms and a valid measured value after 200 – 500 ms, which is based on the measuring principle. Besides, a pressure measurement opposed to the actual pressure tendency can be problematic with Piranis.     

Fügeverfahren im Vergleich: Löten,Kleben, Mechanisches Fügen von Magnesium

Comparison of Joining Techniques: Soldering, Adhesive Bonding, Mechanical Joining of Magnesium Due to their light weight construction potential magnesium sheets are of increasing interest during recent years. During the production process appropriated joining technologies are necessary for sheets to obtain various knot, profile, and sheet structures. Thus studies to develop appropriated joining technologies are of high importance.     

Qualitätssicherung an tribologischen Schichten – Eigenschaften und Meßverfahren

Quality management of tribological coatings – properties and testing methods This paper presents several methods which can be used for determining mechanical properties of thin films. Partly they are also suitable for quality management purposes. The theoretical understanding of the results of mechanical tests on thin films is insufficient up to now. Therefore it is substantial to closely keep to defined testing parameters in order to get meaningful results, may it be for comparison between different testers and coating systems, may it be for testing of the suitability of a coating substrate system for a certain appliance, may it be just as a tool of quality management. The most important parameters influencing the tests and the state of standardisation and norms are discussed here at the example of several testing methods.     

Baubetriebliche Untersuchung von Robotersystemen im Mauerwerksbau

Investigation of robot systems in masonry construction The relevance of robot systems in building construction will increase in the future. This can be seen, among other things, in the number of press releases about successful construction projects and the increasing number of presented systems. This article examines the specific strengths and weaknesses of different robot systems. The University of Duisburg‐Essen is researching the use of cable robots in brickwork construction. This article presents the first results of a series of tests on this cable robot. It is based on the obtained knowledge, the review of existing literature and the analysis of video material. One result is that each robot system has specific strengths and weaknesses and the cable robot can be applied in masonry construction. It has been shown that the combination and parallel production with different robot systems can compensate for the weaknesses of other systems in the long term.     

Untersuchung zur Stabilität von Gefügen einkristalliner Nickelbasis‐Superlegierungen

Investigation of Microstructural Stability of Single Crystal Nickel Based Super Alloys The present study investigates the kinetics of the widening of γ‐channels in the single crystal superalloy CMSX‐4 during high temperature and low stress creep. Shear creep specimens subjected to high resolution shear creep testing were investigated using scanning and transmission electron microscopy (SEM and TEM) in combination with quantitative image analysis. {011} 〈011¯〉‐shear creep tests were performed at a shear stress τ = 50 MPa and a temperature of 1080°C. For the macroscopic crystallographic shear system {011} 〈011¯〉 it was found that γ′‐rafts form in an angle of 45 ° to the macroscopic shear direction. The kinetics of γ‐channel widening can be described by a parabolic rate law. Therefore it is concluded that the diffusion of atoms through the γ‐channels of γ/γ′‐microstructures is the rate controlling process for rafting.     

Schallemissionsuntersuchungen an polymeren Verbundwerkstoffen. Teil I: Das Schallemissionsmeßverfahren als quasi-zerstörungsfreie Werkstoffprüfung

Acoustic Emission Monitoring of Polymeric Composite Materials. Part I: The Technique of Acoustic Emission Monitoring The importance of nondestructive testing methods increases in material and structure production control techniques as well as in the practical, calculated usage of faulty structures. The technique of acoustic emission is a useful aid in monitoring complex structures in real time mode. In Part I the fundamental measuring technique of this testing method is discussed.     

Rißauffangvermögen von Baustählen

Crack Arrest Behaviour of Structural Steels. Medium scale tests are described by which it is possible to estimate the crack arrest behaviour, usually characterized by the Robertson-Test or Double Tension Test. Tests on 16 steels show that the critical temperature for an instable fracture during the sharp-notch slow bend test corresponds largely with the crack arrest temperature determined in the Robertson-Test. A regression equation is given for the relation of the results of both tests.—A distinct relation between the crack arrest temperature of the Robertson-Test on the one side and the transition temperatures measured in the notched bar impact test, the Coheracy test and the drop-weight test on the other side was not observed.     

Kugelstrahlen von Spaltbiegeprofilen mit ultrafeinkörnigen Gradientengefügen

Linear bend splitting and linear flow splitting are innovative methods to produce bifurcated profiles with ultrafine grained (UFG) microstructures in an integral style. Linear bend split profiles exhibit high potential for lightweight applications, due to their bifurcations and the high strength of the ultrafine grained microstructures, which develop at the surface of the work piece. The presence of the ultrafine grained microstructure is accompanied by a duplication of hardness and strength and a markedly increase of the fatigue properties, compared to the untreated material. Because of their high strength, ultrafine grained materials exhibit increased potential for the formation of compressive residual stresses. Therefore, shot peening of ultrafine grained microstructures could result in an increased fatigue resistance. The results clearly show that shot peening, despite optimized shot peening parameters, does not lead to an increase of the fatigue resistance. Compared to the untreated ultrafine grained microstructure, the fatigue resistance of shot peened material is even lower. The lower fatigue resistance is probably caused by the roughness of the shot peened surface, which overcompensates the compressive residual stresses.     

Röntgenographische Untersuchung von Spannungszuständen in Werkstoffen

X-Ray Investigation of Stress States in Materials X-ray stress analyses on crystalline or partially crystalline materials are based on the determination of elastic lattice strains which are converted to stresses by means of theory of elasticity. The development of the sin² ψ-method of X-ray stress analysis and of diffractometers substituting film chambers during the 1960s initiated an enormous progress in X-ray stress analysis during the following three decades both in respect of the knowledge of the underlying principles and in respect of the practical application. This report sketches the historical development of X-ray stress analyses and describes the actual state of the art of this important tool for materials science and engineering. Besides some important elements of X-ray physics and theory of elasticity, experimental aspects of practical applications are outlined. Standard measuring procedures and special measuring problems are described, and hints for practical solutions are given. In particular, examples of destructive and non-destructive depth profiling of residual stresses, of residual stress analysis in thin coatings, in multilayer structures of thin coatings and in chemically graded coatings, of residual stress analyses in presence of textures, of residual and loading stress analyses in heterogeneous materials, in coarse grained, and in single crystalline materials are presented. The methods established up to now are explained and possible future developments are pointed out.     

Zerstörungsfreie,quantitative Bestimmung von innenliegenden Fehlern mit dem Wärmeflußverfahren

Nondestructive, Quantitative Evaluation of Internal Imperfections by Thermal Flux Method The thermal heat flux method with cholesterol liquid crystals to indicate the temperature is a nondestructive testing method, easy to handle and inexpensive. It is possible to inspect parts in the area. If the testing condition are chosen that there is thermal equilibrium the thermographs can be evaluated quantitative. This is the fact that the method not only detect a flaw but also the size and depth can be estimated. We will expect that the importance of thermography will grow up by the written improvement.     

Klinische Anwendungsmöglichkeiten von porösen Biomaterialien im Knochengewebe

Clinical applications of porous biomaterials in bone During therapy of bone defects and lesions it often exists the necessity to treat larger defects. While doing so porous biomaterials are frequently used as an alternative to autologeous bone in the field of implantology, traumatology and orthopaedic surgery with good clinical results. In contrast to autologeous cancellous bone grafts they are of an almost unlimited availability and are not afflicted with the problem of donor morbidity. In order to accelerate the quantity and quality of the newly formed bone and thus to enable the reconstruction of a defect, different biomaterials are used as bone substitutes. These are materials which are able to interact with biological systems, and mostly synthetic porous tricalciumphophates and hydroxyapatite ceramics as well as processed allografts are used. As an additional possibility of clinical application surface coating of implants with porous biomaterials and bone‐forming growth factors comes into consideration. In the presented work an overview of the clinical application possibilities of porous biomaterials in bone as well as an outlook on future developments is supposed to be given.     

Die Substitution von Umlaufvermögen durch Anlagevermögen im Rahmen der Produktion auf Abruf

Zusammenfassung In dieser Arbeit wird mit Hilfe einfacher Lagerhaltungs- und Warteschlangenmodelle untersucht, ob die vom Just-in-Time Konzept geforderte Minimierung der Lagerbestände sinnvoll ist, und ob es möglich ist, die Lagerbestände auf Null zu reduzieren. Hierzu wird davon ausgegangen, daß die die Lagerbestände determinierenden Parameter, insbesondere die Rüstkosten und die Lieferfristen durch strategische Maßnahmen beeinflußt werden können. Auf der operativen Ebene werden die Entscheidungen über Losgrößen und Meldemengen so getroffen, daß die laufenden Kosten, die von den strategischen Maßnahmen abhängen, minimiert werden. Durch parametrische Variation der Investitionen für strategische Maßnahmen kann gezeigt werden, daß zwar Substitutionsbeziehungen zwischen der Kapitalbindung in Lagern und der Kapitalbindung durch die erforderlichen Investitionen bestehen, daß aber abnehmende Grenzraten der Substitution bestehen. Eine Reduktion der Lager auf Null ist in den zugrundeliegenden Modellen nicht möglich.     

Raster-Tunnel-Mikroskopie zur Untersuchung und Modifizierung von Festkörperoberflächen

We present a short review of the capabilities and prospects offered by the scanning tunneling microscopy (STM). Ultra-high vacuum — in general not necessary for STM operation at all — ensures without doubt well-defined surface and tunneling conditions. The latter are especially important for atomic resolution and spectroscopic applications. Shining examples selected from an almost exhaustiveless amount of original papers illustrate the new quality in local surface structural analysis, spectroscopy and modification achieved due to the establishment of STM and related scanning probe techniques.