Bemessungsansätze für das Biegetragverhalten von Stahl- und Spannbeton

Ohne Zusammenfassung     

Festigkeit und Spannungsabbau bei der dynamischen Belastung von Stahl- und Aluminiumproben mit bekannten Eigenspannungen

Strength and Relaxation of Stress During Dynamic Loading of Steel and Aluminium Specimens with known Residual Stress Distributions Residual stresses of the first kind can be introduced in multiply – connected bodies without accompanying changes in the material. The circular ring represents the simplest example in this group. For the circular ring the residual and applied stresses in a fatigue test can be calculated accurately with relations from the theory of elasticity. Circular rings with and without residual stresses were subjected to fatigue testing. It was established that tensile residual stresses reduce the fatigue life and compressive residual stresses have the opposite effect, with the stresses referred to the point of crack initiation. The fatigue behaviour is altered appreciably even by small magnitudes of residual stress. The effect on fatigue life is the same, whether at the point of crack initiation a residual stress or a mean stress of the same magnitude and direction acts. The stress relaxation depends primarily on the difference between the maximum superposed stress and the yield strength or the 0.2% proof stress. The degree of relaxation is particularly high when the yield strength is reached. The first few cycles in a fatigue test are important for the fading of stress. The state of residual stress changes only slightly thereafter. The stress relaxation increases again somewhat only after a very large number of cycles. The changes observed when the sum of residual and loading stresses is below the yield strength may be attributed to the small plastic deformations in favourably oriented crystallites.     

Zur Interaktion von Mathematik und Melancholie

The copperplate Melencolia I engraved by Dürer in 1514 illustrates various interdependencies between mathematics and melancholy. Dürer's engraving is one of the best known works of art in our western history. Up to our own times it has been interpreted repeatedly.The significance of Dürer's Melencolia I for our cultural history is subject of this essay. On the one hand the various changes of the conception of melancholy from antiquity up to Dürer' s times will be called in mind. In addition to it some examples will assert that during the last five centuries the correlation between mathematics and melancholy has been contemplated and shaped as well.     

Bestimmung funktioneller Oberflächenparameter beim Mehrfach-Streifenziehen von Stahl- und Aluminiumblechen in Zylinder/Blech/Zylinder Kontakt Geometrie

Determination of functional surface roughness parameters – Application to multipass strip drawing on mild steel and aluminium sheets in a cylinder/sheet/cylinder contact geometry Multipass strip drawing in cylinder/cylinder die geometry is especially suitable to simulate frictional contact between a smooth die and a rough sheet as occurring in stamping operations. Special attention is focused on the evolution of the plateaux topography, where essentially all normal contact and frictional shear stresses are accomodated. By using a 3-D profilometric scanning stylus relocation technique, we develop statistical parameters which represent the mean length and mean width of the load carrying plateaux. Plateaux flattening and contribution of wear debris to frictional contact is clearly more important for aluminium than for steel.     

Zur Rezeption von Hallers medizinischem und medizinhistorischem Werk im 19. und 20. Jahrhundert

A survey of the secondary literature of Albrecht Haller’s medical work after his death (1777) reveals that already in the 19th century most of his topics and his method were discussed and appreciated. Within physiology his doctrine of irritability and sensibility received most attention. The 20th century shows a considerable expansion of the secondary literature. However, there is still a lack of monographs dealing with Haller’s medical work in a comprehensive way. Not only was the appreciation of Haller’s medical work in the more than 200 years since his death constantly high but, for whatever reasons, it is even characterized by an increasing interest of researchers from many fields.     

Messung elastischer Wellen in Stahl- und Gesteinsstäben mit Hilfe des magnetoelastischen Effektes

Measurements effect of elastic waves in steel- and rock rods using the magneto-elastic Stress waves in steel and iron ore rods produced by a mechanical impact can be measured by a sensor using the magneto-elastic effect. A detection of the changing magnetic flux is made. The function describing the propagation of longitudinal waves in rods is known as the stress wave equation. The agreement with theory is verified by examinations of steel rods using strain gauges. Afterwards the signals of three iron ores (magnetite, hematite, siderite) are recorded. Induced voltage is measured by the magneto-elastic sensor in the case of magnetite and hematite, however it is not possible to detect any signal for siderite. This means that the change of magnetic flux depends on the kind of bulk magnetic appearance, not on content of iron. Using the magneto-elastic sensor the magneto-elastic effect offers the possibility to detect tree of contact mechanical waves produced by a mechanical impact in ferro- or ferrimagnetic solids.     

Zur Optimierung von Turbinen-Gittern

Ohne Zusammenfassung VDI     

Zur Wechselwirkung von Mehrfachrissen

On the Interaction of Cracks Stress intensity factors for multiple cracks in a plate under tension are reviewed. In addition to the known results for symmetrically arranged cracks the interaction effects due to rotation of one of the cracks relative to the load direction are calculated and in some cases examined experimentally. The results are discussed with reference to the safety assessment of structural components.     

Zur Position von Mathematik und Mathematiker/innen in der Industrieforschung vor 1945

The paper considers the status of mathematics and mathematicians in German industrial labs from the 1920s. As an example, we take the use of statistical methods in the electrical engineering company Osram in Berlin. In the United States, the former employee and member of a special mathematical research department of the Bell Telephone Laboratories, Walter Andrew Shewhart (1891–1967), is regarded as the father of statistical quality control. Although the first textbook on applications of mathematical statistics to problems of mass production was published in Germany in 1927, Germany was nevertheless generally considered as conservative in using statistical methods until 1945. In the past we have known little about whether and how these methods were actually applied in German industry before 1945. The present analysis is based on laboratory reports and other sources. It shows that in this field of research there was a close cooperation between industry and university, which was cut off in the mid 1930s due to the Nazi regime. Furthermore, we discovered that female researchers – such as Iris Runge (1888–1966) in the Osram company – could as individuals play a decisive role as mathematical consultants. The position of Runge will be described and compared with the position of mathematical researchers in other industrial labs.

am Beispiel früher Anwendung von mathematischer Statistik in der Osram G.m.b.H. Hans Wu?ing zum 80. Geburtstag gewidmet

     

Zur Berechnung von Tragflügeln und Beschaufelungen nach derPrandtlschen Theorie der tragenden Wirbel

Zusammenfassung Die Grundannahme der Prandtlschen Tragfl?chentheorie über das Verhalten der in ?flüssigen Flügeln? eingeschlossenen Flüssigkeit wird für den allgemeinen Fall eines dreidimensionalen Vorgangs erstmalig mathematisch bewiesen, und zwar sowohl für station?re Str?mungen inkompressibler Flüssigkeiten um ruhende Flügel als auch für station?re relative Str?mungen solcher Flüssigkeiten durch rotierende Beschaufelungen. Im zweiten Fall ist eine getrennte Behandlung der von dem relativen Kanalwirbel erzeugten Bewegung n?tig. Eine Erweiterung der erhaltenen Ergebnisse auf Str?mungen kompressibler Flüssigkeiten bedingt nur kleine ?nderungen des angegebenen Berechnungsgangs. VDI     

Zur korrosionsfestigkeit von verzinktem stahlblech

The surface of galvanized steel proved to be covered with intermetallic compounds, i.e. Zn₂₁Ni₅ and Zn₂₂Ni₃. This covering was passivated when weathered in the air, a solid solution (Ni, Zn)(OH)₂ and amorphous substances being formed there. The specimen surfaces were studied by the aid of electron reflection.     

Zur Wahl der Struktur von Stangenmechanismen

Zusammenfassung Am Beispiel eines Lenksystems mit zwei doppeltwirkenden Hydraulikzylindern für Fahrzeuge mit Knickgelenk wird eine Methode zur Prüfung aller m?glichen Strukturen von Stangenmechanismen dargestellt. Danach wird mit Hilfe der Polyoptimierung die Geometrie des Getriebes bestimmt, das'den Konstruktions- und Einsatzbedingungen genügt. Die Methode der Polyoptimierung liefert dem Konstrukteur, im Vergleich zu den verbreiteten Optimierungsmethoden mit einer Zielfunktion, praxisnahe Ergebnisse. Der angewendete L?sungsweg zeigt neue M?glichkeiten für Mechanismen zur Lenkung von Fahrzeugen mit Knickgelenk. Diese L?sungen charakterisieren günstige Leistungsparameter.     

Berechnung und Optimierung von Geometrie und Eingriffsverhalten von Zahnformen beliebiger Achslage

The main benefit, the economical manufacturability of traditional gear profiles, such as an involute, are no longer of major importance in times of computer-aided design and production. Due to existing modern production techniques standard and more sophisticated gear types can be produced with high precision and maintainable financial effort. Especially for non-standard gear types modern gear production systems ensure high quality and reliability to the operator with regard to flank and meshing geometry. Depending on the context of application different gear types have advantages and disadvantages concerning load carrying capacity, effectiveness or noise excitation. Developing an optimized gearing for the desired application is thus a complex and elementary goal within the design process.     

Zur Viskosität von Glasschmelzen und porösen Sintergläsern

Qn the viscosity of glass melts and porous sintered glasses Suspensions of solid phase particles in molten glasses modify their flow behavior and therefore their viscosity. This work deals with the dependence of the effective viscosity (η_eff) of isotropic suspensions on the concentration of the solid phase particles. Independently of the shape of the inclusions the values of the effective viscosities lie between upper [η_eff = η_L (1 ? C_D)^?14 ]and lower bounds [η_eff = η_L (1 ? C_D)^?3], where η_L is the viscosity of the molten glass and C_D is the volume fraction of solid inclusions. The lower bound is also valid for the effective viscosity of suspensions containing spherical inclusions. Pores present in a glass matrix affect its flow behavior and consequently its creep and sintering behavior. The effective viscosity of porous glasses (η_P) as a function of the volume fraction of pores, or porosity (P), also varies between and upper [η_P = η_M (1 ? P)^1.04] and a lower bound [η_P = η_M (1 ? P)¹⁴], where η_M is the viscosity of the nonporous glass matrix. For spherical porosity the equation is: Measured values for the viscosity of different suspensions as reported in the literature as well as own experimental data on two glass-solid systems are compared with the theoretical values predicted by these equations. In a similar way literature data for the viscosity of porous sintered glasses are compared with the respective equations. In all cases a fair agreement between experiment and theory was found in some cases the agreement was excellent. Therefore the presented equations constitute a reliable approach for the prediction of the viscosity of suspensions and porous sintered glasses and since they do not contain fitting parameters, they are of substantial practical relevance (for a comprehensive english treatment of the matter compare Glastechnische Berichte, Proc. Otto-Schott-Colloquium 1994).