Thermo-micro-mechanical simulation of bulk metal forming processes

The newly proposed microstructural constitutive model for polycrystal viscoplasticity in cold and warm regimes (Motaman and Prahl, 2019), is implemented as a microstructural solver via user-defined material subroutine in a finite element (FE) software. Addition of the microstructural solver to the default thermal and mechanical solvers of a standard FE package enabled coupled thermo-micro-mechanical or thermal-microstructural-mechanical (TMM) simulation of cold and warm bulk metal forming processes. The microstructural solver, which incrementally calculates the evolution of microstructural state variables (MSVs) and their correlation to the thermal and mechanical variables, is implemented based on the constitutive theory of isotropic hypoelasto-viscoplastic (HEVP) finite (large) strain/deformation. The numerical integration and algorithmic procedure of the FE implementation are explained in detail. Then, the viability of this approach is shown for (TMM-) FE simulation of an industrial multistep warm forging

Seeded crystallization of β-L-glutamic acid in a continuous oscillatory baffled crystallizer

A continuously seeded l-glutamic acid cooling crystallization process, in a continuous oscillatory baffled crystallizer, was designed and operated to deliver control over polymorphic form. Different feed solution concentrations and seed loadings of β-l-glutamic acid crystals were examined. Steady-state operation, based on particle size distribution and polymorphic form, was demonstrated consistently after two residence times. Where bulk supersaturation remained in the range 2–3, the polymorphic phase purity of the thermodynamically stable β polymorph was retained. However, when the bulk supersaturation exceeded this range to values of 3–8, primary nucleation of the metastable α polymorph was observed, and product crystals were a mixed phase. In the absence of seeding the system could not be operated without significant encrustation to the vessel surface thus leading to loss of control, whereas a continuously seeded approach allowed robust processing for at least 10 h

SMART – eine verstehensorientierte Online-Diagnostik am Beispiel Variablenverständnis

Formatives Assessment mithilfe technologischer Werkzeuge bietet viele Möglichkeiten, das Lernen zu unterstützen, sowohl im Präsenz- als auch Distanzunterricht. Das Denken beim fachlichen Verständnis von Lernenden schnell und einfach zu erfassen, ist essentiell für eine gezieltes formatives Assessment. In der Regel ist für eine tiefgehende didaktische Diagnose allerdings ein erheblicher Aufwand erforderlich. Viele digitale Diagnoseinstrumente erheben hier den Anspruch, effizient und schnell zu unterstützen. Die meisten digitalen Diagnosewerkzeuge ermitteln zwar den Lernstand, indem sie untersuchen, wie häufig richtig oder falsch geantwortet wurde. Diese Häufigkeiten geben jedoch keinen ausreichenden Einblick in das fachliche Verständnis der Lernenden zum jeweiligen mathematischen Inhalt. Dies bieten hingegen verstehensorientierte, digitale, formative Diagnosetools wie das SMART-System, das in Australien entwickelt wurde (Stacey et al., 2018) und derzeit in Deutschland adaptiert und implementiert wird. Unser begleitendes Forschungsprojekt ist im Bereich der Algebra angesiedelt und konzentriert sich auf das Verständnis von Variablen

Rapid continuous antisolvent crystallization of multi-component systems

This paper describes the application of a novel antisolvent crystallization approach to rapid production of tunable solid solutions of hydrophobic amino acids, comprising L-leucine, L-isoleucine and L-valine. The antisolvent approach provides an alternative to other crystallization routes, e.g., ball-milling, liquid-assisted grinding and slurry methods, to achieve required multi-component solid phases. We report new crystal structures of L-leucine:L-isoleucine and L-leucine:L-valine, and confirm a recent report on a new form of L-isoleucine:L-valine. We used these multi-component complexes as a test set of materials to demonstrate translation of small scale batch antisolvent crystallization to a continuous production process

Multiplicity Structure of the Hadronic Final State in Diffractive Deep-Inelastic Scattering at HERA

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant mass M_X of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in e+e- annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low Q^2. A model with soft colour interactions is also successful.Comment: 22 pages, 4 figures, submitted to Eur. Phys. J., error in first submission - omitted bibliograph

Differential (2+1) Jet Event Rates and Determination of alpha_s in Deep Inelastic Scattering at HERA

Events with a (2+1) jet topology in deep-inelastic scattering at HERA are studied in the kinematic range 200 < Q^2< 10,000 GeV^2. The rate of (2+1) jet events has been determined with the modified JADE jet algorithm as a function of the jet resolution parameter and is compared with the predictions of Monte Carlo models. In addition, the event rate is corrected for both hadronization and detector effects and is compared with next-to-leading order QCD calculations. A value of the strong coupling constant of alpha_s(M_Z^2)= 0.118+- 0.002 (stat.)^(+0.007)_(-0.008) (syst.)^(+0.007)_(-0.006) (theory) is extracted. The systematic error includes uncertainties in the calorimeter energy calibration, in the description of the data by current Monte Carlo models, and in the knowledge of the parton densities. The theoretical error is dominated by the renormalization scale ambiguity.Comment: 25 pages, 6 figures, 3 tables, submitted to Eur. Phys.