Rektifikation von Dreistoffgemischen insbesondere von Sauerstoff-Stickstoff-Argon-Gemischen

Ohne Zusammenfassung VDI     

Laserbeschriftung von Hartferritmagneten zur Kennzeichnung von Druckgussteilen

With the presented method of magnetic labeling die cast components are labeled and provided with production data as well as protection against plagiarism. The magnetic labels are cast close under the surface of the component during the casting operation. Serial numbers, data and graphical information was engraved on the surface of hard ferrite magnets by laser marking using a diode-pumped ytterbium fiber laser. The data and graphical information was encoded as data matrix codes. Inexpensive strontium ferrite magnets were used. Melting processes and thermally induced material changes on the magnet surface during the laser labeling of the magnets results in a local demagnetization. The measurable decrease of the magnetic field strength is a result of local heating above the Curie temperature and the geometrical change of the magnet surface. The patterns with changing magnetic flux density can be visualized directly by a magnetic viewer or measured by magnetic field sensors such as Hall effect sensors. This paper deals foremost with the laser labeling process and the induced changes on the surface of the magnets as well as visualization and measuring test. First results of casting trials are presented, to confirm the stability of the magnetic labeling procedure during the casting operation.     

Der biaxiale Kreuzzugversuch zur Ermittlung von Werkstoffkennwerten von Airbaggeweben am Beispiel von Polyamid 6.6

A biaxial cruciform test for the determination of material data of polyamid 6.6 airbag fabric The determination of material data on samples under real, complex, test conditions is of considerable interest. In this work a cruciform test for airbag fabric and some exemplarily measurement curves for a typical polyamid 6.6 airbag fabric are presented and discussed.     

Analyse von Partikeleigenschaften beim Thermischen Spritzen von Mikropulvern

Analysis of In‐Flight Particle Properties of Thermal Sprayed Ultrafine Powders Demands on functional coatings with high dimensional accuracy and high surface quality has led to increasing interest in processing of very fine powder grades in a particle size range < 20 μm in past years. Fine powders are not only showing a distinct potential for application of thin and dimensionally accurate coatings, but are also very promising for the production of dense and homogeneous coatings with improved mechanical properties. The large specific surface of fine powders is allowing for relatively low thermal energy levels that are introduced into the process. Nevertheless is also requires a very sensitive temperature control, to prevent overheating of the particles. The reduction of the thermal energy level is resulting in significant advantages particularly for the usability of the HVOF process for coating of inner diameters. Within this work in‐flight particle properties of ultrafine carbide powders were analyzed. The studied HVOF process allows the adjustment of a broad parameter range by utilization of a hydrogen stabilized liquid fuel combustion process. A conventional straight nozzle type as well as a curved nozzle for internal spraying was studied. For a further assessment of the potential of ultrafine carbide powders also spray trials with a plasma spraying system have been made.     

Untersuchung von Oberflächenschutzschichten von Gasturbinenlegierungen

Investigations on protective coatings on gasturbine alloys. It has been found by investigations of specimens of a combustion chamber pilot plant and also by experiences with gasturbines that aluminide or chromium aluminide coatings are only slightly protective under working conditions of industrial gasturbines. Chromium coatings have a distinctive better protective efficacy and are surpassed in this quality by silicide coatings. It was possible to give information on the development of silicide phases on Nimonic 105. Under the conditions of corrosive attack a surface layer of Nickelolivine is formed and the silicide phases are changed in direction of ternary phases. Even when chromium sulfides are formed in the silicide layer the specimens are stable under the test conditions. By investigations on an airfoil made from B 1900 with a protective coating of Aluminium and Silicon the presence is shown of a ternary Laves phase with Silicon.     

Bildung von geordneten Konstruktionsfamilien unter Anwendung von Ähnlichkeitsgesetzen

The theory of Constructional Similarity bases on the theory of physical similarity. The pattern construction is a model in the theory of constructional similarity. The essence of this work is to choose such constructional features of the new designed constructional means to obtain the identical states: physical, stereo mechanical or simple like in the pattern construction.     

Anwendung von Methoden der Bruchmechanik zur Lebensdauerverbesserung von Umformwerkzeugen

Application of Fracture Mechanics for the Improvement of the Life Time of Forming Dies An investigation was undertaken to determine the life times of dies when these life times are determined by crack propagation from such stress raisers as notches. Notched DCB specimens were used to investigate the processes of crack initiation and propagation in the high temperature steel X 40 CrMo V 51 at 500°C. The results showed that the life times depend both on the heat treatment of the material and also on the length of hold time at temperature. Hold times during the forming process should be minimized in order to avoid fast creep crack propagation.     

Einfluß von Sauerstoffspuren auf die Eigenschaften von Wolfram-Schwermetallen

Influence of Oxygen Traces on the Properties of Tungsten Heavy Metals Investigation carried out with differently sintered W heavy metals showed that careful pre-reduction before liquid phase sintering is essential for obtaining satisfactory mechanical properties; otherwise oxide layers at the phase boundaries deteriorate the interface strength and thus cause premature fracture. Understandably, the water vapour content of the furnace atmosphere is of considerable importance. Appropriate sintering anticipated, even severely oxidized green compacts result in highly ductile heavy metals. Addition of scavengers, e.g. Cr or V, instead of the pre-reduction improves the interface strength, the mechanical properties however remain unsatisfactory.     

Einfluss von Schmierstoffsystemen auf die Ermüdungsbeanspruchbarkeit von Schraubenverbindungen

The fatigue behavior of bolted joints is critical to failure for many applications due to the high notch effect. Among other parameters, the life-time is based on the influence of the surface system, consisting of coating and lubricant. Intended to consider the surface system in the design and dimensioning process of bolted joints systematic experimental investigations are carried out for an exemplary selected basecoat and various lubricant systems. The basis is given by fatigue tests supported by selected methods of material analysis for the fractographic evaluation. A reproducible method to determine the crack initiation as well as the crack propagation has been developed for the evaluation of lubricant systems.     

Komplexe Bewertung von Indentereindrücken zur Charakterisierung von Konstruktionskeramik

The induction of indentations in brittle materials and their evaluation result in information useful for the characterization of materials. In addition to the fracture-mechanical evaluation of the indentations, i.e. of the incipient cracks resulting from them, which cracks are used for determining the fracture toughness. Information regarding the hardness, critical size of surface defects, characteristic quantities of crack propagation, durability as well as existing internal stresses can be derived.     

Konfidenzintervalle von unfallzahlen

The theoretical principles for finding the confidence limits of empirically obtained accident figures are here set forth. The conventional statistical estimates at present known from literature on the subject are valid only for high accident figures empirically obtained. The estimate here adduced is based on the Bayes statistical procedure. It is valid independently of the magnitude of the empirically obtained accident rate. It therefore offers the possibility of laying down confidence limits even for very low empirically obtained accident figures. By utilizing the largely known Tables of the χ² distribution it is relatively easy to determine the exact confidence limits. This estimate also enables a previous knowledge of the order of magnitude of an accident rate to be included in the calculation. This procedure can lead to a reduction in the span width of the confidence interval and thus to the defining of a statement. The practical application of this treatise leads to the compilation of tables and diagrams for the confidence limits of accident figures.

Résumé

Les principes théoriques pour trouver les limites de confiance de chiffres d'accidents obtenus empiriquement sont présentés ici. Les estimations statistiques classiques présentement connues de la littérature sur le sujet ne sont valables que pour les chiffres élevés d'accidents obtenus empiriquement. L'estimation donnée ici est fondée sur la procédure statistique de Bayes. Elle est valable indépendement de la grandeur du taux d'accident obtenu empiriqueiment. Elle offre par conséquent la possibilité de préparer des limites de confiance même pour les chiffres faibles d'accidents obtenus empiriquement. En utilisant les tables bien connues de la répartition χ² il est relativement facile de déterminer les limites de confiance exactes. Cette estimation permet également d'inclure dans les calculs les connaissances précédentes de l'ordre de magnitude d'un taux d'accident. Cette procédure peut mener à une réduction de la largeur de portée de l'intervalle de confiance et ainsi à la définition d'une déclaration. L'application pratique de ce traité mène à la préparation de tables et de diagrammes pour les limites de confiance de chiffres d'accidents.     

Anpassung von Lenkkosten

Zusammenfassung Ein in der Industrie implementiertes (s,S)-Lagerhaltungsmodell wird mit einem Wagner-Whitin (WW)-Modell verglichen. Drei Kriterien werden dazu herangezogen: Mittlerer Lagerstand, Bestellhäufigkeit und Servicegrad. Es zeigt sich, daß sich im WW-Modell Lenkkostenparameter angeben lassen, für die das WW-Modell in allen Zielen dominant ist. Diese Untersuchungen bestätigen sich nicht nur an den gegebenen empirischen Nachfragezeitreihen, sondern auch an allgemeineren durch Simulation generierten Zeitreihen.

---

Summary An adaptive (s,S)-inventory model being implemented in industry is compared with a Wagner-Whitin (WW)-model. Three criteria are taken into account: mean stock on hand, order frequency, and service level. It is shown that cost parameters can be chosen for the WW-model such that this model leads to dominant values for all 3 criteria. These results not only hold for the empirical time series of the company studied but also for more general time series generated by simulation.

     

Schmelzpunkte von Reaktor-Werkstoffen

Ohne Zusammenfassung VDI     

Dauerfestigkeit von Sinterwerkstoffen

Fatigue Strength of Sintered Materials Based on recently published fatigue test results it is now for the first time possible to estimate fatigue diagrams for sintered steels. Fatigue strength of sintered steels is mainly influenced by density and alloying content, production parameters being of lesser importance.     

Kantenwiderstand von Schaufelreihen

Zusammenfassung Um dem Leistungsbedarf von Str?mungsmaschinen im Leerlauf oder die Radreibung partiell beaufschlagter Laufkr?nze bestimmen zu k?nnen, ist die Kenntnis des Kantenwiderstandes von Schaufelreihen von gro?er Wichtigkeit. Nachstehend wird über Versuche an einem rechteckigen Kanal berichtet, dessen beide Seitenw?nde mit Schaufelstummeln besetzt waren, deren Neigung zur Str?mungsrichtung gew?hlt wurde. Der Kantenwiderstand erwies sich als wesentlich abh?ngig von der Reynoldsschen Zahl, dem Schaufelwinkel, dem Verh?ltnis Kanalbreite zu Schaufelteilung und bei kleineren Kanalbreiten auch von der gegenseitigen Versetzung der Schaufelreihen.