Flow fields in electromagnetic stirring of rectangular strands with linear inductors: Part II. computation of flow fields in billets, blooms, and slabs of steel

The model presented in Part I of this series of papers is used to compute flow velocities in the longitudinal stirring of steel blooms and billets, and in the horizontal stirring of steel slabs. In longitudinal stirring of blooms and billets the reverse flow is on the side of the strand opposite to the inductor. The effects of penetration depth of the electromagnetic force, of the force itself, of the length of the stirrer, and of the width of the liquid core were determined. In horizontal stirring of slabs the reverse flow takes place outside of the stirrer region, forming the so-called butterfly stirring pattern. The characteristics of this flow field depend to a considerable extent on the width of the stirrer. The effects of stirrer width, of thickness of the liquid core, of force and of width of the slab were elucidated. The maximum velocities in both types of stirring are represented as simple formulae. Formerly with Institut für Allgemeine Metallurgie, Technische Universit?t Clausthal     

Rotational electromagnetic stirring in continuous casting of round strands

A model is presented to compute the three-dimensional flow field in rotational electromagnetic stirring of round strands. The model involves the solution of the Maxwell equations, the Navier-Stokes equations, and the transport equations for the turbulence characteristicsk andε. For the limiting case of one-dimensional stirring, the computations were checked with experiments using mercury as the fluid. Several sets of computations were carried out to determine the influence of stirrer position, stirrer length, and electromagnetic parameters on the flow field in continuous casting of steel strands.     

Effect of bottom stirring and post stirring on the oxygen distribution between metal and slag at the end of the LD process

Studies concerning the effect of stirring and post-stirring on the oxygen distribution at the end of the LD process show that a post-stirring phase following the end of the blow establishes an oxygen distribution close to equilibrium. The sub-lance tests performed at 90% of the oxygen throughput show in comparison with the post-stirring phase a distinct oxygen deficiency, while the blow end-point measurements show an excess of oxygen.     

Effect of weld metal mis-match on toughness requirements: Some simple analytical considerations using the Engineering Treatment Model (ETM)

The recently introduced Engineering Treatment Model (ETM) relates the crack tip opening displacement (CTOD) to the applied load or strain for work hardening materials. The formalisms of ETM were applied to a transverse welded wide plate with a crack in the weld metal. Both the base material and the weld metal were regarded as power law hardening materials. It can be shown that differences in the plastic properties of the weld metal and base material, respectively, significantly affect the CTOD. Quantitative relations are given for the CTOD of a crack in the weld metal normalised by the CTOD a crack in the base material would exhibit. An important result is that the characterisation of a non-matching weld metal by the matching factor M only is not sufficient since work hardening plays an important role.From this, requirements for minimum weld metal toughness can be established in order to make the toughness performance of the weldment no worse than that of the base material.     

Kinetic resolution of heptan-2-ol-enantiomers by lipase-catalysed esteri?ication in organic solvent

Summary The lipase-catalysed esterification of racemic heptan-2-ol in organic solvent has been investigated. Porcine pancreas lipase, suspended in heptane, preferentially catalyses the synthesis of (R)-2heptyl butyrate starting from (R,S)-heptan-2-ol and butyric acid. The distribution of the reaction products and the stereochemical course of the esterification have been investigated by means of capillary gas chromatographic methods.

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Lipase-katalysierte Veresterung von Heptan-2-ol durch Trennung der Enantiomere in organischem Lösungsmittel

Zusammenfassung Die Lipase-katalysierte Veresterung von racemischen Heptan-2-ol in organischem Lögsmittel wurde untersucht. Ausgehend von Buttersäure und (R,S)-Heptan-2-ol katalysiert in Heptan suspendierte Schweinepankreas-Lipase bevorzugt die Bildung von (R)-Buttersäure-2-heptylester. Die quantitative Verteilung der Produkte und der stereochemische Verlauf der Reaktion wurde mittels capillargaschromatographischer Methoden untersucht.

     

Einfluß der nukleierung auf struktur und mechanische eigenschaften von spritzgußteilen aus polyhexamethylenadipinamid (PA 66)

The influence of the variation of the molecular weight, of the mold temperature and of the temperature of the melt during injection molding as well as of the addition of nucleating agents on the morphology and the mechanical properties of injection molded PA 66 samples was studied. The orientation of the needle-shaped phthalocyanine particles, acting as nucleating agents, which took place preferably in the shear zone, gave rise to the formation of row nucleated spherulites. The mechanical properties remained unchanged although the degree of the crystal orientation increased. The addition of a specific nucleating agent for polyamides resulted in a decrease of the elongation to break by 80% and in an increase of the yield strength by 15%. This behaviour can be attributed to the formation of small spherulites having a diameter of about 3?4 μm as compared to the original sample which is characterized by diameters of spherulites of about 30 μm. The observation that the addition of nucleating agents to PA 66 does not lead to a distinct shift in the temperature of the crystallization exotherm in the DSC-experiment indicates that this method is not beyond doubt in determining the nucleating capacity of a nucleating agent with respect to induced changes in the morphology and the mechanical properties.     

A.I.K.E.F.: Adaptive hybrid model for space plasma simulations

The interaction between magnetized space plasmas and obstacles like comets, asteroids or planets is determined by a variety of physical processes that occur simultaneously on significantly different length and time scales. Frequently the dynamics of individual ions play a key role for the shape of the interaction region: strong velocity shear between light and heavy plasma constituents, non-Maxwellian particle distributions due to pick up and asymmetries in the magnetic field topology are crucial in determining this type of interaction. Covering these processes is beyond the scope of any Magnetohydrodynamic (MHD) model. In order to account for these effects we have developed a new adaptive hybrid code A.I.K.E.F. (Adaptive Ion-Kinetic Electron-Fluid). The code operates on Cartesian meshes that can adapt to the physical structures in both, space and time. To the authors' knowledge, there is no other adaptive hybrid simulation code in space plasma physics to the present day. Adaptivity is implemented by means of Hybrid-Block-AMR, that is individual octs are refined rather than entire blocks, where an oct is one eighth of a block. In order to account for a reasonable number of particles in each cell, particles are refined via splitting and merging. Both procedures conserve mass, momentum and kinetic energy. The code is implemented in C++ and efficiently parallelized for distributed systems by means of the Message Passing Interface (MPI). In order to demonstrate the validity of our newly developed code we have applied it to a series of fundamental test scenarios. On the one hand we demonstrate that the dispersion relation as well as the propagation characteristics of MHD and whistler mode waves are quantitatively reproduced by our simulation code. Wave propagation remains unaffected when traveling through regions that include different refinement levels. On the other hand we verify that the results obtained on high resolution uniform meshes are identical to the results from adaptive simulations that use coarse base meshes but include various levels of refinement. A remarkable speedup could be observed: the adaptive simulations required 71 times less CPU-hours than the uniform mesh simulations. Finally, we present a first series of global, three-dimensional simulations for the interaction of Mercury with the solar wind and a real time study of Titan's plasma interaction during a magnetosheath excursion.