Toughness requirements for steel structural components with surface flaws

Fracture mechanic safety analyses consist of a comparison between material toughness and toughness requirement of the Investigated structure. For the selection of suitable materials the requirements must be known. The fracture mechanics toughness requirements for a structural component depend on several parameters. Load case, geometry of the component and of a postulated or detected flaw, strength of the steel and the chosen safety criterion are decisive for the toughness requirements. Performing three-dimensional elastic plastic finite element analyses the toughness requirements for plates of high strength structural steels with surface flaws have been determined as a function of the above mentioned parameters.     

Simulation des Profilwalzens mit Hilfe von Werkstoffmodellen und der Finite-Elemente-Methode

Eine Grundvoraussetzung für die Einführung der thermomechanischen Behandlung beim Profilwalzen ist die Beherrschung der örtlichen Vorgänge im Walzspalt. Hierzu bietet sich die Finite-Elemente-Methode (FEM) als Hilfsmittel zur Ermittlung der örtlichen Prozeßparameter Vergleichsformänderung, Vergleichsformänderungsgeschwindigkeit und Temperatur an. Werkstoffmodelle können zur Beschreibung der örtlichen physikalisch-metallurgischen Vorgänge in einem Material und zur weiteren Entwicklung der FEM verwendet werden. Über die möglichen Wege für die Simulation des Profilwalzens mit FEM und Werkstoffmodellen sowie durch Verwendung von Warmumformsimulationen am IBF und am IEHK wird in dieser Arbeit berichtet. Walzungen im Labormaßstab von 4 Stichen der Kaliberreihe Oval-Quadrat werden Rechenergebnissen für die Stahlsorten C 35 und 50 CrV 4 gegenübergestellt. Ergebnisse aus Versuchswalzungen und Warmzugsimulationen für die Stahlsorte 50 CrV 4 werden verglichen und diskutiert. Erläuterungen über die allgemeine Anwendung der hier verwendeten Arbeitsroutine werden am Ende dieser Arbeit gemacht. Die Ergebnisse zeigen die Bedeutung dieser Arbeitsroutine für die Simulation des Profilwalzens.     

Aufgaben der Produktionsleitebene in der chemischen Industrie

The plant management functions in chemical industry . The information flow can be structured by a layer model, comprising the plant management layer, the process control layer, and the field layer. The higher company management layer issues production orders which are detailed at the plant management layer with the aid of a formulation; amounts of materials required, equipment, personnel, and laboratory measurements are assigned as a prerequisite for production. These tasks are described in detail, the flow of information between the adjacent layers indicated, and the layer structure of other business units briefly considered.     

Innovative microwave-assisted hydrolysis of ellagitannins and quantification as ellagic acid equivalents

The health-promoting effects of ellagic acid and its intestinal degradation products are well-known. In plants, ellagic acid mainly appears in the form of its precursors, the so-called ellagitannins. Therefore, determination of total ellagic acid content has been accomplished by cleaving ellagitannins with high temperatures and strong acids. Microwave-assisted extraction (MAE) has been shown to be a very effective and quick extraction technique. The aim of the present study was to establish an MAE-based method for a rapid hydrolysis of ellagitannins and to compare this method with a conventional acid hydrolysis. For this purpose, strawberries (Fragaria x ananassa), which have been identified as a major source of ellagitannins in human diet, were used as a model. The newly developed MAE method was quicker, less chemical-consuming and more effective in hydrolysing ellagitannins.     

Contributions of empirical and quantile processes to the asymptotic theory of goodness-of-fit tests

This paper analyzes the evolution of the asymptotic theory of goodness-of-fit tests. We emphasize the parallel development of this theory and the theory of empirical and quantile processes. Our study includes the analysis of the main tests of fit based on the empirical distribution function, that is, tests of the Cramér-von Mises or Kolmogorov-Smirnov type. We pay special attention to the problem of testing fit to a location scale family. We provide a new approach, based on the Wasserstein distance, to correlation and regression tests, outlining some of their properties and explaining their limitations. Dedicated to Miguel Martín Díaz whose scientific criticism has greatly inspirated our research by years. Research partially supported by DGICYT, grants PB98-0369-C02-01 and 02. E. del barrio and C. Matrán have also been supproted by PAPIJCL grant VA08/97.     

Reaction of Ozone with Ag(I)—Mechanistic Considerations

Ozone reacts slowly with Ag⁺ (circumneutral pH, k = (11 ± 3) × 10^?2 M^?1 s^?1). After some time, ozone decay kinetics may suddenly become faster with the concomitant formation of silver sol. As primary process, an O-transfer from O₃ to Ag(I) is suggested, whereby Ag(III) is formed [Ag⁺ + O₃ + 2 H₂O → Ag(OH)₃ + O₂ + H⁺]. This conproportionates with Ag(I), which is in large excess, leading to Ag(II) [Ag⁺ + Ag(OH)₃ ? 2 Ag(OH)⁺ + HO^?]. Further, Ag(II) reacts with ozone in a high exergonic reaction [Ag(OH)⁺ + O₃ → Ag + 2 O₂ + H⁺], where ozone acts as a reducing agent. Thereby, a single silver atom, Ag, is formed that can be oxidized by O₂ and O₃ or can aggregate to a silver sol. Aggregation slows down the rate of oxidation. When Ag⁺ is complexed by acetate ions, ozone decay and silver sol formation are speeded up by enhancing Ag(II) formation [Ag(I)acetate + O₃ → Ag(III)acetate → Ag(II) + CO₂ + ?CH₃]. In the presence of oxalate, the formed complex reacts faster with ozone than Ag⁺, and Ag(III)oxalate decarboxylates rapidly [Ag(I)oxalate + O₃ → Ag(III)oxalate → Ag⁺ + 2 CO₂]. This enhances ozone decay but prevents silver sol formation. Quantum chemical calculations have been carried out for substantiating mechanistic suggestions.     

Key Properties of Ni?Mn?Ga Based Single Crystals Grown with the SLARE Technique

Magnetic shape memory alloys (MSMAs), exhibit large strains and hence are materials, which could substitute giant magnetostrictive and piezoelectrical materials in actuating devices. The actuation stress needed to induce the strain is much lower than in other actuator materials. Since the strain can be induced without phase transformation by a magnetic field, the development of actuators with high working frequencies is possible. However, for reasonable applications, large strains have to be induced with small magnetic fields. Up to now repeatable magnetically induced strains of 5–10% in magnetic fields of less than 500 mT have been achieved only in single crystals. The production of Ni? Mn? Ga based single crystals is difficult and time consuming. The crystal quality is affected by porosity and impurities. With the Bridgeman based method called Slag Remelting and Encapsulation (SLARE) single crystalline ingots of Ni? Mn? Ga, Ni? Mn? Ga? Fe, and Ni? Mn? Ga? Co of high quality were grown and characterized. The results show that MSMA properties depend on the position within the single crystalline rods due to a composition gradient. The influence of surface treatment demonstrates that the decrease of surface roughness leads to a decrease of twinning stress. MSMAs with twinning stresses above 1 MPa show a magnetic field induced strain (MFIS) when tilting is not restricted by constraints. Softer samples can adapt to constraints much better and show large MFIS. Substituting Ni by Fe and Co, shifted the phase transitions successfully to higher temperatures. Ni? Mn? Ga alloyed with up to 6 at.% Co showed three different martensite structures: a non‐modulated tetragonal structure, a modulated tetragonal structure, showing the same behavior as Ni? Mn? Ga with identical structures and a non‐modulated orthorhombic structure with a stress–strain‐behavior explainable by the double twinning mechanism.