Analysis of profile and flatness in flat hot rolling based on non linearly coupled models for elastic roll stack deflection and pseudo-steady-state elasto-viscoplastic strip

An enhanced iterative concept for the effective numerical simulation of flat hot rolling processes is presented. The underlying physical process is the forming of metal within a flat rolling stand, i.e. between a lower and an upper roll set, each of them consisting of one or more rolls. The strip material is described elasto-viscoplastically, whereas the roll stack is deformed elastically. The accurate coupling of the strip model with the routines for the elastic roll stack deflection is a precondition to get reliable results concerning profile transfer and incompatible residual strains inside the strip, which allows the prediction of flatness defects, such as buckling. Especially for thin, wide strips and heavy plates, where the aspect ratio width over thickness is extremely unfavourable, the determination of profile transfer and flatness bviously leads to extremely high calculation times with commercial FEM-programs. Therefore, a tailor-made FEM-code for the efficient simulation of the elasto-viscoplastic material flow inside the roll gap was developed and programmed in C++. It is based on pseudo-steady-state, fully implicit stress-update approaches, where the incremental material objectivity is satisfied exactly. The developed model is well suited for systematic parameter studies to investigate flatness defects in more detail and to develop enhanced flatness criteria for thin hot and cold strips and plates

Analysis of camber formation, suppression and control in hot rolling of wedge-shaped slabs by utilizing fem and analytical concepts

Reducing wedge without generating camber is still a big challenge for today’s process automation systems for hot strip mills. Therefore, detailed transient 3D-models of the underlying severely asymmetric flat hot rolling processes have been developed by the authors with the help of the commercial FEM-package ©Abaqus Explicit. By utilizing suitably positioned edging rolls, the corresponding lateral force acting on the strip induces a lateral material flow inside the roll gap, leading to stress-redistributions such that the outgoing camber-curvature is drastically reduced. Systematic parameter studies performed so far revealed how the lateral edging force and the resulting strip camber-curvature depend on characteristic rolling parameters, such as slab width, thickness, initial wedge and thickness reduction. To understand the underlying highly non-linear elasto-viscoplastic forming processes inside the strip or slab in more detail, and to develop fast simulation-tools, semi-analytical model reduction approaches have been developed. This enables a quantitative analysis of the induced lateral material flow and the occurring stress-redistributions inside the roll bite. By introducing a lateral material transfer parameter directly correlated to the camber-curvature, an analytical relation could be derived for the bending moment (and external work) that has to be applied to eliminate the camber of the strip or slab. These analytical predictions, although based on rough simplifications, correspond quite satisfactorily with those attained by 3D-FEM simulations

Minimal Model for Sand Dunes

We propose a minimal model for aeolian sand dunes. It combines an analytical description of the turbulent wind velocity field above the dune with a continuum saltation model that allows for saturation transients in the sand flux. The model provides a qualitative understanding of important features of real dunes, such as their longitudinal shape and aspect ratio, the formation of a slip face, the breaking of scale invariance, and the existence of a minimum dune size.Comment: 4 pages, 4 figures, replaced with publishd versio

Differential Cross Sections and Cross-Section Ratios for the Electron-Impact Excitation of the Neon 2p⁵3s Configuration

Electron-impact differential cross-section measurements for the excitation of the 2p53s configuration of Ne are reported. The Ne cross sections are obtained using experimental differential cross sections for the electron-impact excitation of the n = 2 levels of atomic hydrogen [Khakoo et al., Phys. Rev. A 61, 012701-1 (1999)], and existing experimental helium differential cross-section measurements, as calibration standards. These calibration measurements were made using the method of gas mixtures (Ne and H followed by Ne and He), in which the gas beam profiles of the mixed gases are found to be the same within our experimental errors. We also present results from calculations of these differential cross sections using the R-matrix and unitarized first-order many-body theory, the distorted-wave Born approximation, and relativistic distorted-wave methods. Comparison with available experimental differential cross sections and differential cross-section ratios is also presented

Unresponsive wakefulness syndrome: a new name for the vegetative state or apallic syndrome

BACKGROUND: Some patients awaken from coma (that is, open the eyes) but remain unresponsive (that is, only showing reflex movements without response to command). This syndrome has been coined vegetative state. We here present a new name for this challenging neurological condition: unresponsive wakefulness syndrome (abbreviated UWS). DISCUSSION: Many clinicians feel uncomfortable when referring to patients as vegetative. Indeed, to most of the lay public and media vegetative state has a pejorative connotation and seems inappropriately to refer to these patients as being vegetable-like. Some political and religious groups have hence felt the need to emphasize these vulnerable patients' rights as human beings. Moreover, since its first description over 35 years ago, an increasing number of functional neuroimaging and cognitive evoked potential studies have shown that physicians should be cautious to make strong claims about awareness in some patients without behavioral responses to command. Given these concerns regarding the negative associations intrinsic to the term vegetative state as well as the diagnostic errors and their potential effect on the treatment and care for these patients (who sometimes never recover behavioral signs of consciousness but often recover to what was recently coined a minimally conscious state) we here propose to replace the name. CONCLUSION: Since after 35 years the medical community has been unsuccessful in changing the pejorative image associated with the words vegetative state, we think it would be better to change the term itself. We here offer physicians the possibility to refer to this condition as unresponsive wakefulness syndrome or UWS. As this neutral descriptive term indicates, it refers to patients showing a number of clinical signs (hence syndrome) of unresponsiveness (that is, without response to commands) in the presence of wakefulness (that is, eye opening)

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s=7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb(-1) of root s = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved