Grundlagen der Schwingfestigkeitssteigerung durch Fest- und Glattwalzen

Improvement of Fatigue Properties by Roll Peening With sophisticated calculations a better understanding of the roll peening process is possible. Calculations together with experimental determination of the fatigue properties allow for a reduced test program to determine the fatigue limit of specimens with similar geometrical shape.     

Prozessmodell zum Einbringen von Eigenspannungen durch Festwalzen

Defects in axles lead to a significant reduction of lifetime. Deep rolling provides a simple way to prevent crack growth emanating from defects or at least to slow down the crack growth rate, provided the flaw size does not exceed the size of the zone affected by the compressive residual stresses. In this work, a simple process model is presented for estimating the penetration depth of compressive residual stresses from deep rolling.     

Festwalzen und Schwingfestigkeit

Deep Rolling and Fatigue Strength The fatigue properties of specimens and components are largely increased by deep rolling. Depending on geometrical shape of components and material strength the compressive residual stresses and the increased surface hardness made by deep rolling have a different effect on the improvement of fatigue strength. The fatigue properties of smooth specimens and components with a sufficient toughness can be raised by increase of surface hardness, whereas in case of notched parts the influence of permanent compressive residual stresses is dominant. The application of deep rolling in case of crankshafts shows a clear superiority of mechanical strengthening procedure to thermal surface strengthening. If there are some reasons to improve the wear behaviour beside the fatigue strength it is commendable to combine thermal and mechanical surface strengthening.     

Glatt- und Festwalzen an PKW Fahrgestell- und Antriebsbauteilen

Finsh and Solid Rolling of Automotive Running Gear and Drive Components Automotive parts, in particular running gear and drive components, are subject to high dynamic loads in regards to strength. When designing new parts, this is taken into account through dimensioning, material selection and constructional conception. Normally the mentioned measures will not be applied to old designs if, for example, they are subjected later to higher loads because of an increase in engine power output. Only the selection of different materials as well as strength increasing measures and methods remain for these parts. An important method is solid rolling. The examples of completed designs demonstrate the possible strength improvements, influence of rolling force on component strength as well as desired and undesired accompaniments. A comparison is made between solid rolling and other strength improving measures, such as inductive hardening. The results show the solid rolling method to be cost-favorable, very effective and safe in handling. The method has its limits in geometry (open rotation-symmetrical cross sections are required), size (component too large, cross section too filigreed) and application range (temperature) of components.     

Festwalzen – eine Technologie für effizienten Leichtbau

Deep Rolling – a technology for efficient lightweight design Deep rolling is a proven method for increasing the fatigue strength of dynamically loaded parts. Although this application has been used for many years, procedures that induce work hardening and residual stresses are not well known. This article concerns both deep rolling and the potential for considering the resultant residual stresses in the design phase of components to achieve efficient lightweight design. In addition, the article includes new research results regarding the numerical modelling of deep rolling.     

Kraftstoffersparnis durch Hochleistungswerkstoffe

Fuel Saving by the Use of High‐Performance Materials Due to new European regulations efficiency of modern automobiles has to be increased. Two possible ways to achieve a reduction of fuel consumption are weight reduction by light metals like aluminium and use of coatings to reduce friction losses and enable new efficient working points. An example which combines both ways is the engine of a modern automobile. More and more light alloys like AlSi are used to reduce the engine weight. Furthermore, coatings are used to maximise the weight reduction and to increase the efficiency. Thus, thermal spraying is used to avoid wear on the aluminium bores and thin coatings on piston rings deposited by means of Physical Vapour Deposition (PVD) decrease the friction losses and allow low wear within this tribological contact.     

Ultraschallwellen durch Hohlsog

Zusammenfassung Die Spektren der Ultraschallwellen, die auf Grund der Kavitation an den Proben bei Korrosionsversuchen mittels magnetostriktiver Schwingungen entstehen, sind experimentell mit dem Ziel untersucht worden, die Kavitation zu erforschen und die Ergebnisse mit der bei hydraulischen Maschinen auftretenden Kavitation zu vergleichen. Ferner lieferten die Untersuchungen auch die Form der Kavitationsblasen und der Korrosionssch?den. Es wird eine Versuchseinrichtung mit aufw?rts weisender Probenoberfl?che vorgeschlagen. Mitteilung aus dem Institut für Hochgeschwindigkeitsmechanik Tohoku Universit?t, Sendai, Japan. Der Verfasser dankt an dieser Stelle derHatakeyamas Kulturstiftung für die finanzielle Unterstützung bei dieser Untersuchung sowie den HerrenM. Hongō, I. Chida, R. Satō, Assistenten am genannten Institut, für ihre Mithilfe.     

Kugelherstellung durch Pulveragglomeration

Preparation of spheres by powder agglomeration . Some methods of producing spheres by powder agglomeration are described. The agglomerability of fine particles which is influenced by various parameters is qualitatively discussed. To produce spherical agglomerates that have smooth surfaces, low or no binder contents should be used. Besides the conditions for growth, internal structure and strength of agglomerates is dealt with. A variation of process parameters allows the preparation of different spherical structures.     

Kalibrierdruckerzeugung durch statische Gasexpansion

The method of generating well known calibration pressures by means of static expansion of gases is described and the required mathematical equations are derived in general form for real gases. Temperature effects caused by the expansion process are estimated and compared with experimental data obtained at an expansion apparatus. Thereafter, the experimental measurement of the expansion ratio and the generation of calibration pressures over a wide pressure range are discussed for a specific apparatus. Controlling the temperature by immersing the apparatus in a circulated water bath, the uncertainty contribution due to temperature effects was substantially reduced as compared to conventional apparatuses. The uncertainty budget reveals that this apparatus allows the generation of a pressure of, e.g., 0.1 mbar for various gases with a small relative uncertainty (2σ) of 1 . 10^‐3.     

Korrosion durch Biokraftstoffe – Schutz durch Beschichtungen auch bei zyklischer Beanspruchung

Corrosion by biofuels ‐ Protection by coatings also under cyclic loadings The influence of corrosion on fatigue design must be considered in numerous component parts in the automotive industry. By using appropriate coatings the negative influence of corrosion under static and cyclic loading can be suppressed. Using the aluminum cast alloy AlSi7Mg0,3 T6 as an example, selected material‐coating‐systems were to be characterized under mechanical‐thermal‐corrosive complex loadings and characteristic properties for the fatigue design under cyclic loadings were to be determined. Conditioning tests were carried out with uncoated, anodized and chemical‐nickel‐plated specimen at different temperatures in the media fuel E5 (fuel with 5 % ethanol added) and E10 (fuel with 10 % ethanol added) and followed by SEM examined. The cyclic fatigue tests with chemically‐nickel‐plated and tempered aluminum in the fuel E5 at 100 °C no reduced influence on the fatigue strength, within the scattering, was discerned. This result agrees with the conditioning tests in the fuel E5 at 100 °C, where no corrosion was observed. Despite the coating of the specimens salt spray fog leads to a clear reduction in the fatigue strength. Using a damage accumulation calculation, it could be shown, that the real damage sum of the callipers and specimens, despite different types of coating, are comparable.     

Optimierung der Schneckenradfertigung durch Prozesssimulation

The simulation program developed in recent years allows the complete worm wheel manufacturing process to be simulated. Depending on the state of wear of the grinding tool, the simulation provides optimum machine setting data – and more precisely the center distance when milling and the milling tool swivel angle. The target gear flank topography of the worm wheel can now also be calculated using this machine setting data. Instead of the previous contact pattern check using special blueing paste and a master worm, the actual flank topography of the gearwheel can be determined on a gear measuring center. A comparison then identifies the deviations between the actual and target flank topographies. The simulation program calculates optimized machine setting data from the values that are determined. This technique has an inestimable advantage due to the fact that it also essentially compensates topography errors caused by deviations at the milling tool, deformation of the milling machine etc. A subjective assessment of the tooth contact pattern by the machinist is now replaced by an objective measurement and a simulation of the milling process.     

Stabilisierung und Labilisierung durch Schwingungen

Zusammenfassung Ziel dieses Aufsatzes ist es, gewisse Schwingungserscheinungen zu beschreiben und zu erkl?ren, die sich mit Hilfe der “üblichen Schwingungslehre”, d. i. der Theorie der linearen Differentialgleichungen mit konstanten Koeffizienten, nicht mehr beschreiben und erkl?ren lassen, zu deren Erkl?rung vielmehr Differentialgleichungen mit periodischen Koeffizienten herangezogen werden müssen. Die Betrachtung wird in der Hauptsache auf den einfachsten Fall einer Differentiagleichung mit periodischen Koeffizienten, die sogenannte Mathieusche Differentialgleichung, beschr?nkt. Das besondere Augenmerk richtet sich dabei auf die Unterschiede, die bezüglich der Stabilit?t der L?sungen in den beiden genannten F?llen bestchen. VDI Mitteilung aus dem Institut für Schwingungsforschung an der Technischen Hochschule Berlin     

Selbstoptimierung der Regelparameter durch Orthogonal-Strategie

Zusammenfassung In der modernen, flexibel automatisierten Fertigung stellen sich mit Proze?regelung und Qualit?tssicherung regelungstechnische Aufgaben, die auch mit digitalen Regelungskonzepten gel?st werden. Bei Auslegung und Realisierung solcher Regelungen tritt die Bestimmung der Regelparameter, die mit dem dynamischen Verhalten des Regelkreises verbunden sind, in den Vordergrund. um die optimale Kombination der Regelparameter zu finden und stets das geforderte Regelverhalten zu gew?hrleisten, bietet sich eine Selbtoptimierung der Regelparameter an. Diese erfolgt in der Praxis sehr h?ufig durch direkte Methoden an einem realen Regelkreis. Hierzu wird unter technischen und wirtschaftlichen Gesichtspunkten ein geeignetes Suchverfahren entwickelt. Der aus der Fertigung stammende Anwendungsfall ist die Druck-und Abfolgesteuerung der hydraulischen Spannyzylinder für automatischen Aufspannung von komplexen Werkstücken. Die optimierte Regelung wird zwecks besserer Reproduzierbarkeit und h?herer Pr?zision angewandt.     

Temperaturstabilisierung durch Wärmerohre

Zusammenfassung W?rmerohre, mit denen wechselnde W?rmestr?me übertragen werden, lassen sich zur Stabilisierung ihrer Betriebstemperatur verwenden, wenn sie z. T. mit Edelgas gefüllt sind. Die experimentell ermittelte Temperatur?nderung zwischen 0,5 kW und 1,0 kW übertragener Leistung betr?gt 0,5% für eine wassergekühlte, selbstregelnde Anordnung und 2,2% für eine entsprechende strahlungsgekühlte Anordnung. Einen ungünstigen Einflu? auf die Temperaturstabilisierung hat die w?hrend des Betriebs wechselnde Gastemperatur insbesondere dann, wenn der Partialdruck des W?rmetr?gerdampfes in dieser Zone Werte annimmt, die man nicht mehr vernachl?ssigen kann. Diese Untersuchung wurde mit finanzieller Unterstützung der Kommission der Europ?ischen Gemeinschaft im Euratom-Forschungszentrum Ispra, Italien, ausgeführt.