Multi-level simulation of metal-forming processes

The IBF has for some years made use of finite element programmes to solve metal-forming problems. In the course of this investigation, it has become evident that a problem-oriented adaptation of FEM simulation to the problem in hand is beneficial in terms of computation effort. The computation time for the process parameters is optimised in a multi-level simulation. At level 1 (global analysis) integral parameters such as the required force and required work are computed using a coarse FEM mesh. At level 2 (local analysis) an optimised number of elements is used to determine continuum mechanics parameters like stress, strain and temperature. Microscopic phenomena are simulated at level 3 (microscopic analysis), using special micro-material elements and thermodynamic models.     

Alternating,all-trans polyenynes: Model compounds for poly(diacetylene)s with defined conjugation length

The syntheses of polyenynes as model compounds for poly(diacetylene)s (PDAs) are described. Variation of properties (UV–VIS, Raman, NMR and bond geometries) as a function of the chain length was investigated. After extrapolation to infinite chain length these data were compared to those for PDAs. From UV–VIS spectra a value of λ = 551 nm (2.25 eV) was calculated corresponding to the electronic transition of a single polyenyne chain. This energy is located at the low energy end of a yellow PDA solution spectrum. From Raman scattering v_(C?C) = 2108–2128 cm^?1 and v_(C?C) = 1505–1532 cm^?1 were calculated after extrapolation. Similarly sp-C¹³C NMR data yielded a shift of δ = 100 ppm. These data are almost identical to data known for yellow PDA solutions. Bond geometries are almost identical to those of poly(diacetylene)s and theoretical data.     

More applicable environmental scanning systems leveraging “modern” information systems

With Ansoff’s article about weak signals as a flagship example, a substantial body of knowledge about environmental scanning systems exists. However, these concepts often go unused in practice. The 2008/2009 economic crisis provided a strong, ongoing impulse for redesigning such information systems (IS). This article develops six guidelines for the conceptual design of environmental scanning systems that are more applicable than those specified by previous research. We start with literature research, which reveals three gaps in existing approaches. Then we develop design guidelines to fill these gaps with the help of “modern” IS. To address the lack of sound requirements analysis, our first design principle proposes 360-degree environmental scanning systems for executives and suggests how to select the most important scanning areas. Three further findings cover weaknesses in the IS model perspective, focusing on more effective implications of weak signals. In terms of method, we propose incorporating scanning results more closely into executives’ decision-making processes. Applying the design guidelines at a raw materials and engineering company, we arrive at a prototype we call the “corporate radar.” It includes an IS-based tree with economic value added at risk on top. The resulting lessons learned help to evaluate our findings and the research method presented here, as well provide concrete starting points for future research.     

The liberalized δ-rule in free variable semantic tableaux

In this paper we have a closer look at one of the rules of the tableau calculus presented by Fitting [4], called the -rule. We prove that a modification of this rule, called the ⁺-rule, which uses fewer free variables, is also sound and complete. We examine the relationship between the ⁺-rule and variations of the -rule presented by Smullyan [9]. This leads to a second proof of the soundness of the ⁺-rule. An example shows the relevance of this modification for building tableau-based theorem provers.     

Tests and Proofs

This special issue collects current advances in the ongoing attempt to obtain synergies from the combination of Tests and Proofs.     

Mass-controlled capillary viscometer for a Newtonian liquid: viscosity of water at different temperatures

The operation principle of the mass-controlled capillary viscometer is presented for a Newtonian liquid. The derived equation for the temporal changes of the mass in a liquid column draining under gravity through a discharge capillary tube accounts self-consistently for the inertial convective term associated with the acceleration effect. The viscosity of water measured at different temperatures using the new approach is in good agreement with literature data.     

Solid state reaction in sandwich-type Al/Cu thin films

Al/Cu/Al and Cu/Al/Cu triple layers with approximately 10 nm single layer thickness deposited on tungsten substrates were analyzed in the early stages of reactive interdiffusion by means of atom probe tomography. The first reaction product is found after 5 min thermal treatment at 110 degrees C and identified by direct chemical analysis to be Al2Cu. Surprisingly, we found a significant asymmetry in the reaction rate of the new phase with the stacking sequence: the thickness of the product grown at the interfaces, at which Cu is deposited on top of the Al layer, is approximately 1.5-2 times thicker than the other one at the interfaces at which Al is deposited onto a Cu layer. On the other hand, at both interfaces the thickness of the product layer depends parabolically on time. No precursory interdiffusion and no distinct nucleation process of the product are observed.     

SDS electrophoresis of legume seed proteins in horizontal ultrathin-layer pore gradient gels

Summary Horizontal SDS electrophoresis of 18 legume seed protein extracts was performed in ultrathin-layer polyacrylamide gels on foil supports. Separation results of the SD S pore gradient electrophoresis (T=4–22.5%) are compared to those of SDS electrophoresis in a constant pore size gel (T=10%). Resolution as well as the sensitivity (0.1 g protein per band) of the ultrathin-layer SDS pore-gradient electrophoresis were extremely high. Because of the very low gel thickness, separation, staining and drying were completed in substantially shorter times than achieved with conventional thick gels. An easy technique for casting ultrathin-layer (360 gm) concave gradient gels for 10 cm separation distance and a width of 25 cm is described. The even distribution of the concave exponential pore-gradient over the whole gel width is demonstrated. Molecular weights of the legume proteins are detected from 5,000 to 110,000 daltons. The protein patterns are genus- and species-specific.

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Horizontale Ultradünnschicht SDS-Gradientengel-Elektrophorese von Leguminosensamenproteinen

Zusammenfassung Die ausgezeichnete Trennschärfe der horizontalen Ultradünnschicht-SDS-Gradienten-gel Elektrophorese wird am Beispiel von Samenproteinen 18 verschiedener Leguminosengattungen, -arten und -sorten gezeigt. Es werden die Trennergebnisse der SDS-Elektrophorese mit Gelgradienten (T=4-22,5%) bzw. mit Gelen konstanter Porengröße (T=10%) verglichen. Das höchste Auslösungsvermögen und die beste Trennschärfe zeigen ultradünne Gradientengele. Die Nachweisempfindlichkeit ist bei allen Ultradünn-schicht-SDS-Elektrophoresen sehr hoch (0,1 g Protein/Bande). Da die auf Folie polymerisierten Gele sehr dünn sind (360 m) kann mit wesentlich verkürzten Trenn-, Färbe-, Entfärbe- und Trocknungszeiten gear-beitet werden. Es wird eine einfache Herstellung ultradünner Polyacrylamidgele mit exponentiellen konkaven Gradienten für die Trenndistanz von 10 cm mit einer Breite von 25 cm beschrieben. Die gerade und gleichmäßige Verteilung des Gradienten über die gesamte Gelbreite wird gezeigt. Mit der beschriebenen Methode werden bei den untersuchten Leguminosen-proteinen Molekulargewichte von 5 000 his 110 000 Dalton gefunden. Die Proteinmuster erweisen sich als gattungs- und artspezifisch.

     

An automated Thixo‐Forging Plant for Steel Parts

The scope of the article is to describe the automated production of a thixoformed steel part. The production plant was set up within a prototype initiative at the Institute of Metal Forming in cooperation with the Institute of Automatic Control of RWTH Aachen University and industrial partners. Preliminary experiments showed that the quality of the formed parts varied to a great extent due to changing production conditions since the handling of the billet was carried out manually. To eliminate the possible disturbances introduced by the manual handling of the billet, an automation concept has been elaborated in order to guarantee a defined production environment. An industrial robot (KUKA) fulfils the handling tasks like the feeding of the induction coil with the feedstock material and the placing of the heated billet into the hydraulic press. The removal of the formed part from the press is realised by a simple mechanical device in order to be able to use only one gripper. The design of the gripper ensures a minimal heat loss during handling. The induction coil, the gripper system and the cavity are flooded with inert gas in order to prevent scaling. The sequence control for the production of a part is realised on the controller of the robot which provides sufficient PLC functionality and can be easily equipped with the required I/O components to trigger the different automation components.