Formability of High Strength Dual‐phase Steels

The application of ferritic‐martensitic dual‐phase (DP) steels has become an increasing trend in the automotive industry due to the possibility to achieve significant weight reduction and fuel efficiency with improved crash performance while keeping the manufacturing costs at affordable levels. In order to meet the different design requirements of individual auto‐body components, a wide variety of DP grades exhibiting different strength and ductility levels is currently industrially produced. Despite the numerous studies on the relationship between the mechanical properties and the microstructural characteristics of DP steels over the last decades, it is still a challenge to increase their formability at a constant strength level (or equivalently increasing the strength while maintaining a high ductility). One of the possibilities to increase strength is grain refinement. Ultrafine‐grained ferritic‐martensitic microstructures were produced by intercritical annealing of a cold‐rolled, pre‐processed dual‐phase steel. Ferrite mean grain sizes in the order of ~ 1.5 μm were obtained. The mechanical properties of these steels are studied, revealing the beneficial effect of grain refinement. Ultimate tensile strength above 800 MPa is achievable, while reaching remarkable high uniform and total elongations, which are only slightly affected by the martensite volume fraction. Moreover, the yield to tensile strength ratio can be adjusted between 0.4 and 0.5. Light and electron microscopy investigations, fracture profile and fracture surface analyses, hole expansion tests and additional ultramicrohardness measurements are used for the interpretation of the results and for the correlation of the mechanical properties and the formability characteristics with the microstructure of the steel.     

A functional variant of the serotonin transporter gene in families with bipolar affective disorder

BACKGROUND: The serotonin transporter protein (SERT) reuptakes serotonin from synapses and has been implied as the site of therapeutic action of many antidepressant drugs. SERT is one of the most relevant candidate genes for bipolar affective disorder. Recently a functionally important 44 basepair deletion in the regulatory region of the SERT gene was described. Association between this variant and affective disorder has been suggested. METHODS: The present study analysed this variation and another variation in the SERT gene and nearby DNA markers in order to test for linkage between SERT and bipolar affective disorder in two Danish families. RESULTS AND CONCLUSION: There was no evidence that variants in the SERT gene were a stronger dominant disease gene for the development of affective disorder in the families. The possibility of a recessive disease gene at or near SERT could not be excluded. LIMITATIONS: The present study cannot exclude if variations at or near the SERT gene were weak susceptibility genes or determine if they are important for other characteristics than presence or absence of disease. CLINICAL RELEVANCE: Further studies of the SERT gene in affective and other disorders, as well as in relation to treatment response to antidepressants are needed.     

Neue Technologien — neue Korrosionsprobleme

New Technologies – New Corrosion Problems. Adequate resistance of materials to corrosion is equally important for classical and for new technologies. This article considers the economic consequences of corrosion damage and, in addition to the longknown GNP orientation, presents a new approach to the estimation of the costs of corrosion and corrosion protection via maintenance and especially corrosionrelated maintenance. The significance of “high-tech”, “medium-tech” and “low-tech” material and corrosion problems is assessed. Selected examples taken from new technologies in the areas of power engineering, environmental engineering, chemical engineering, and biotechnology demonstrate the great significance of the problems. It is concluded that corrosion research and corrosion prevention technology will never come to an end but will constantly face new problems. Two technologies are of particular interest since they focus attention on new methods of investigation: microelectronics and final disposal of radioactive wastes. The article closes by considering the importance of the transfer of experience and technology. Since the manufacturs and operators of machines and plant do not generally have access to the very latest knowledge, they should be kept informed through advisory services, experimental studies, databases, and further education.     

Control of robot manipulators for handling and assembly in spaceSteuerung von robot-manipulatoren zum handhaben und montieren im raum

Long-range NASA planning includes construction and erection of large systems in space requiring automatic handling equipment, teleoperators, or robots under supervisory control. This paper investigates and explores some of the requirements for the control of teleoperated and autonomous space manipulators. The critical technology development areas are identified and discussed in the context of the developments at the Jet Propulsion Laboratory (JPL), and other places.     

Correctness issues for distributed relational database design

This paper examines correctness issues that arise in distributed database design. A distributed relational database design is traditionally considered to be valid if every global relation can be reconstructed from its fragments by join operations. In this paper, three successively less restrictive definitions of validity are presented, each providing progressively improved handling of incomplete information. Examining these forms, a hybrid reconstruction approach involving inner- and outer-joins is proposed and we briefly describe its application to query formulation.We also propose replacing the notion of global reconstructability with the less restrictive, yet intuitively natural notion of object reconstructability. Universal relations need not be constructed. The need for maintenance of constraints across sites of a distributed system is discussed, and the notion of adistributed referential constraint is proposed which fulfills this need. Recommended by: Clement Yu     

Enhancement of the quality of the reactor pressure vessel used in light water power plants by advanced material,fabrication and testing technologies

Fracture safe assessment of nuclear reactor pressure vessels (RPV) is based upon an adequate stress analysis, reliable material characteristics and acceptable defect sizes.Problems may arise concerning inhomogeneities, low toughness and crack phenomena as observed in the base material and heat affected zone (HAZ). Therefore, efforts have been made to develop a steel which would be both non-susceptible to embrittlement and/or cracking in the HAZ, and have a higher upper-shelf toughness of base and HAZ material. Tests have been made on inhomogeneities and defects and also on improvement of chemical composition, the steel-making process, welding procedures and the optimum temperature cycle and level for stress-relief heat treatment.To solve these problems, common testing methods were supplemented by tangential-cut techniques, small HAZ-tensile test procedures and HAZ-simulation techniques.Results indicate that 50 per cent of 100 investigated component-strength welds are affected by micro stress-relief cracking (SRC) on a micro- and millimetre scale. The 22 NiMoCr 37 steel with optimised chemical composition, and the 20 MnMoNi 55 steel are both resistant to stress-relief embrittlement and SRC. Specific welding techniques are found to limit SRC and proposals for optimum stress-relief temperatures are given.For the generation of new components, the fracture-safe analysis can now be based completely upon homogeneous and high upper-shelf base materials including the HAZ.     

Present quality level of large heat resistant rotor forgings made of 1 % CrMoV steels – Part 1

The mechanical and toughness properties of steam turbine rotors of different production methods and different heat treatments are described and compared. Air and oil quenched rotors have similar properties in respect to creep behaviour while the toughness level of the oil quenched rotors is better. Rotors manufactured since about 1975 have a better level of all properties than older ones which is due to higher degree of purity, lower level of trace elements and a today better controlled temperature process during the whole manufacturing.     

Photometrische und titrimetrische Bestimmung von Schwefelverbindungen nebeneinander in wäßriger Lösung

Photometrische und titrimetrische Verfahren zur Bestimmung von Sulfid, Sulfat, Sulfit, Thiosulfat, Polysulfiden und Polythionaten im Auslaugewasser von metallurgischen Schlacken (Hochofenschlacke) und anderen Wässern. Ermittlung und Ausschaltung der Fehlermöglichkeiten. Überprüfung der Arbeitsvorschriften und Bestimmung der Genauigkeit mit Modellanalysen. Anwendung auf das Auslaugewasser von Hochofenschlacken und verschiedene andere Wässer.     

Sicherheitstechnik bei der Handhabung von Wasserstoff

Safety engineering in the handling of hydrogen . After a survey of the handling of hydrogen as a gaseous or liquid industrial gas, possible safety risks are discussed in the light of its properties, and primary, secondary, and tertiary safety measures are deduced therefrom. The most important German regulations for stationary and mobile hydrogen installations are indicated. A comparison shows that hydrogen, which was introduced into industry decades ago, is no more dangerous than other inflammable gases and liquids freely available even to the public.