bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energy and CO2 Savings: Systematic Approach and Examples in Polymer Production
Authors: Bachmann Rolf , Drumm Christian , Garg Vijay Kumar , Heijl Jan , Ruytinx Bert , Eynde Johan Vanden , Wolf Aurel 
Published: November 2013

SummaryThe chemical industry has set ambitious targets for the reduction of greenhouse gas emissions and energy consumption. In the present work, a systematic approach for a successful reduction of energy consumption and emissions is presented. A Structured Efficiency System for Energy (STRUCTese®) helps to identify, monitor and manage energy efficiency. The method fosters and accompanies energy saving measures as shown in the first two examples from polymer production: energy savings through operational efficiency and raw material savings with a new plant design. In addition, such a systematic approach pushes the development of innovative processes and provides a vision for an energy efficient future as shown in the third example: the use of CO2 as a raw material in the copolymerization with epoxides.
Dynamics of Network Formation in Aqueous Suspension RAFT Styrene/Divinylbenzene Copolymerization
Authors: Gonçalves Miguel A. D. , Pinto Virgínia D. , Dias Rolando C. S. , Hernándes‐Ortiz Julio C. , Costa Mário Rui P. F. N. 
Published: November 2013

SummaryExperimental studies concerning the RAFT copolymerization of styrene and commercial divinylbenzene were performed in order to assess the use of controlled radical polymerization for the production of non‐conventional polymer networks. Aqueous suspension polymerizations were carried out in stirred batch reactor and changes of a few operation parameters were tried in order to assess their effect on key product properties: reaction temperature, initial ratio monomer/RAFT agent, monomer dilution in the organic phase and crosslinker content in the monomer mixture were changed along the experimental program. Polymerizations were extended beyond the gel point in order to synthesize gel beads. The effect of different commercially available RAFT agents (e.g. S‐thiobenzoyl thioglycolic acid and two trithiocarbonates) on network process formation was also studied. Dynamics of gel formation was measured using size exclusion chromatography with refractive index and light scattering detection. Iodine chloride titration yielded pendant double bonds concentration. In‐line and off‐line FTIR‐ATR measurements were also performed in order to obtain information concerning the kinetics of formation and final structure of the gels.
An In‐Situ NMR Study of Radical Copolymerization Kinetics of Acrylamide and Non‐Ionized Acrylic Acid in Aqueous Solution
Authors: Preusser Calista , Hutchinson Robin A. 
Published: November 2013

SummaryAn in‐situ NMR technique has been developed to study the aqueous phase copolymerization of non‐ionized acrylic acid (AA) and acrylamide (AM) under near‐isothermal conditions at much higher monomer contents than previously reported in the literature. The composition data obtained over the entire conversion range provides a precise estimate of monomer reactivity ratios not available from low conversion data. The set of experiments, with initial monomer content in aqueous solution varied between 5 and 40%, were well‐fit over the complete conversion range by rAA = 1.24 ± 0.02, and rAM = 0.55 ± 0.01. It was found that the rate of monomer conversion increases with increasing monomer concentration, a trend contrary to the known decrease in the AA and AM chain‐end propagation rate coefficients.
New Reactor for Polyester Polyols Continuous Synthetic Process
Authors: Chen Like , Xi Zhenhao , Qin Zhen , Zhao Ling , Yuan Weikang 
Published: November 2013

SummaryBased on the kinetic and thermodynamic equations, a comprehensive mathematical model for the continuous synthetic process of polyester polyols was developed, which was carried out in two innovational bubbling reactive distillation towers (BRDTs). In this new type of reactor, condensation reactions among oligomers of polyester polyols were accomplished efficiently and rapidly. Two bench BRDTs with the height of 2 m were applied for the continuous process of poly(ethylene adipate) (PEA). In the first continuous esterification operation at atmospheric pressure, linear oligomers were discharged from the bottom of the column, while water and ethylene glycol (EG) passed a few column trays and a packing section and reached the top of the column. Then water was discharged as byproducts and EG was sent back to the first tray for further reaction. In the second continuous polycondensation operated in the second BRDT under partial vacuum, PEA was discharged from the bottom of the column, while water and ethylene glycol passed a few column trays, they were discharged as byproducts. The influence of major operating conditions on reactor performance was also simulated. Simulation results provided a strategy for developing and optimizing this process.
Experimental and Modeling Study of Melt Polycondensation Process of PA‐MXD6
Authors: Xi Zhenhao , Chen Like , Zhao Yong , Zhao Ling 
Published: November 2013

SummaryThe main polycondensation reaction of poly(m‐xylene adipamide) (PA‐MXD6) is a reversible reaction strongly coupled with mass transfer in melt polycondensation process. In this work, a realistic model for melt polycondensation of PA‐MXD6 has been proposed taking in to account the kinetics data, equilibrium data and diffusion process for major by‐product water in the melts. The characteristics of reaction and the effects of mass‐transfer of polycondensation process have been studied by using stagnant film experiments. It is observed that the apparent rate of the polycondensation process increases with higher temperature, lower degree of vacuum and thinner film thickness with reduced specific interfacial area. Based on the experimental data, the model parameters including the kinetics data, equilibrium data and mass transfer coefficient of volatile have been estimated by the nonlinear least squares method. The model predictions are in a quite satisfactory agreement with the experimental data that all of the relative deviations are almost less than 2%.
Certified Nonlinear Parameter Optimization with Reduced Basis Surrogate Models
Authors: Dihlmann Markus , Haasdonk Bernard 
Published: November 2013

AbstractPDE‐constrained parameter optimization problems suffer from the high dimensionality of the corresponding discretizations, which results in long optimization runtimes. One possible approach to solve such large scale optimization problems more rapidly is to replace the PDE constraint by a low‐dimensional model constraint obtained via model reduction. We present a general technique for certification of such surrogate optimization results by a‐posteriori error estimation based on Reduced Basis (RB) models. We allow arbitrary PDEs and optimization functionals, in particular cover nonlinear optimization problems. Experiments on a stationary heat‐conduction problem demonstrate the applicability of the error bound. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling Dislocation‐Stacking Fault Interaction Using Molecular Dynamics
Authors: Rezaei Mianroodi Jaber , Svendsen Bob 
Published: November 2013

AbstractIn a number of fcc materials such as copper or aluminum, as well as more complex materials such as twinning induced plasticity (TWIP) steels, the interaction between dislocations and other defects such as stacking faults or twins plays an important role in the hardening behavior of such materials. Interactions of dislocation and twin or stacking fault layers have been studied in this work using molecular dynamics. Depending on the material and the loading conditions, possible interaction modes include (i) penetration of the dislocation into the faulted layer, (ii) reduction of the faulted layer after interaction, (iii) growth of the faulted layer after interaction. Such studies up to this point have been performed without temperature control near zero K (0 to 2 K). In this work, we extend the previous studies to higher temperature with the help of two methods, both based on molecular dynamics (MD) modeling. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterisation of bubble clusters in simulations of upward turbulent channel flow
Authors: Santarelli Claudio , Fröhlich Jochen 
Published: November 2013

AbstractThe paper reports on Direct Numerical Simulations of bubble‐laden flows performed to investigate the interaction of bubbles with turbulence in an upward flow between two parallel vertical plates. Two simulations are presented with uniform bubble diameter and a third one with bi‐disperse bubbles. Three different approaches are used to characterize bubble clustering in the investigated configuration. Horizontal pairing and tendency to form cluster has been found for all reported cases, slightly less pronounced in the bi‐disperse swarm. Among other results, a 60°‐alignment has been found by means of the angular pair correlation function for the mixed pairs in the bi‐disperse swarm. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On frequency estimations in phase fitted variational integrators for the general N‐body problem
Authors: Kosmas Odysseas , Leyendecker Sigrid 
Published: November 2013

AbstractIn the present work, the advantages of high order variational integrator methods are combined with phase lag properties for the numerical integration of the general N‐body problem. Expressing the action integral at any intermediate points along the curve segment using a discrete Lagrangian that depends only on the end points of the interval, high order integrators can be obtained by defining the discrete Lagrangian in any time segment as a weighted sum on intermediate points, whose expressions for positions and velocities use Galerkin interpolation techniques. When oscillatory behavior is taken into account, the methods derived use trigonometric interpolation functions that depend on a frequency, which needs to be estimated. For that, using phase lag analysis, a new way to derive methods has been developed, that uses frequency estimation for each body at every time step. Results on special cases of the N‐body problem show more stable orbits and less energy error when compared with the linear interpolation scheme. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elements on the Concept and Design of a Tracked Mini Robot – “ROBO GENIU” – Destined for Special Applications
Authors: Petrişor Silviu Mihai , Bârsan Ghiţă , Ioan Diana Andreea Aniela 
Published: November 2013

AbstractThe authors of this paper aim to highlight issues related to the organology and the integration of the hardware component in the mechanical structure of a tracked mini robot, called Robo Geniu, part of the unmanned ground vehicles category having the ability to act autonomously and enabling its endowment with means of observation, listening, tapping, relaying and jamming. This paper reveals, in detail, the composing parts of the hardware component, as well as the way they are assembled in the mechanical structure of the mini robot under study. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Mechanics of a High‐G Human Centrifuge
Authors: Dančuo Zorana , Rašuo Boško , Vidaković Jelena , Kvrgić Vladimir , Bućan Mirko 
Published: November 2013

AbstractThis paper presents the kinematic characteristics of a human centrifuge for pilot training. The focus is placed on the influence of the tangential acceleration on human centrifuge performances. The main planetary motion is expressed with an ordinary first‐order nonlinear differential equation, which is solved numerically. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative Study of the Influence of Statistically Distributed Microscopic Quantities on the Damage in Collagenous Tissues
Authors: Schmidt Thomas , Balzani Daniel , Holzapfel Gerhard A. 
Published: November 2013

AbstractIn this contribution we investigate the influence of dispersed microscopic quantities on the damage behavior in collagenous tissues. Therefore, we derive a damage model, that may take into account statistical distributions of collagen fiber properties. In detail, we regard distributions of the orientation of fibril‐interconnecting proteoglycan (PG) bridges and of an internal fibril length parameter. The damage model is embedded into the constitutive framework from [1] and a numerical example in a finite element framework is given. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of muscle paths in biomechanical simulations
Authors: Maas Ramona , Leyendecker Sigrid 
Published: November 2013

AbstractWithin dynamical simulations of biomechanical motion, the actuation of a multibody system (representing bones and joints) can be implemented via Hill‐type muscle models. The main task of these models is to describe the typical force‐length and force‐velocity relation of real muscles. Thus, it is crucial that the muscle path itself, which is dynamically changing during a motion, is represented correctly in the model, because its length and the change of its length in time, i.e. its concentric or eccentric velocity, are related to the scalar value of the muscle force amount and to the direction of the force acting on the multibody system. In our work, we assume that a muscle tone is always present, even at rest, which leads to the conclusion that tendons and muscles are supposed to follow the path of minimal distance between two insertion points not intersecting the bones. This problem can for example be formulated as a constrained nonlinear optimisation problem, or it can be solved with a more efficient algorithm that determines this path as a G1 (geometrical) continuous combination of given curves. Within this work, both procedures are compared concerning the resulting path length and force directions and their computational costs. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hyperelastic biphasic fiber reinforced model for articular cartilage considering the distribution and orientation of collagen fibers
Authors: Albrecht Daniel , Ricken Tim , Pierce David M. , Holzapfel Gerhard A. 
Published: November 2013

AbstractArticular cartilage is a multiphase material consisting of fluids and electrolytes, which is described with the Theory of Porous Media. The mechanical characteristics of articular cartilage are porosity, incompressible material behavior combined with transversely isotropic behavior for solid and fluid phases. There are two central points to model articular cartilage: the poro‐viscosity of the porous matrix and the visco elasticity, and orientation of the collagen fibers. A numerical example is presented. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a FEM model for isotropic and transversely isotropic growth in biphasic materials
Authors: Werner Daniel , Ricken Tim , Ferreira Pfeiffer Anne 
Published: November 2013

AbstractThe presented continuum mechanical model describes isotropic and transversely isotropic growth in biphasic materials with focus on biological tissue. The model is capable to describe full isotropic growth, full transversely isotropic growth as well as a combination of both types. This approach is chosen to describe the most common occurring growth types, namely isotropic and transversely isotropic growth, but also to describe effects where the growth of the investigated body depends on multiple single growth effects that are difficult to distinguish among each other. For the description of growth a biphasic homogenized approach within the framework of the theory of porous media (TPM) is used. In this work we focus on the applied formulation of multiple multiplicative decoupling of the deformation gradient into elastic, growth, isotropic and transversely isotropic parts including the governing constitutive equations. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of microstructural damage evolution during very high cycle fatigue (VHCF) using the boundary element method
Authors: Hilgendorff P.‐M. , Fritzen C.‐P. , Grigorescu A. , Zimmermann M. , Christ H.‐J. 
Published: November 2013

AbstractA simulation model for damage evolution in slip bands under VHCF condition is presented. By use of a numerical method it is applied to a real simulated microstructure of AISI304. It considers orientations of slip systems as well as individual anisotropic elastic properties in each grain. The numerical method is the two‐dimensional boundary element method which is based on two integral equations and implies fundamental solutions for anisotropic elastic solids. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Configurational‐Force‐Driven Crack Propagation and Adaptive Mesh Refinement in Finite Inelasticity
Authors: Böger Lukas , Miehe Christian 
Published: November 2013

AbstractWe introduce a consistent variational framework for inelasticity at finite strains, yielding dual balances in physical and material space as the Euler equations. The formulation is employed for the simultaneous usage of configurational forces as both driving forces for crack propagation as well as h‐adaptive mesh refinement. The theoretical basis builds upon a global balance of internal and external power, where the mechanical response is exclusively governed by two scalar functions, the free energy function and a dissipation potential. The resulting variational structure is exploited in the context of fracture mechanics and yields evolution equations for internal variables. In the discrete setting, we present a geometry model fully separated from the finite element mesh structure that represents structural changes of the material configuration due to crack propagation. Advanced meshing algorithms provide an optimal discretization at the crack tip. Local and global criteria are obtained via error estimators based on configurational forces being interpreted as indicators of an energetic misfit due to an insufficient discretization. The numerical handling is decomposed into a staggered algorithm scheme for the dual set of equilibrium equations in material and physical space and efficient mesh generation tools. Exemplary numerical examples are considered to illustrate the method and to underline the effects of inelastic material behaviour in the presented context. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A modified multistage fatigue model to study the fatigue life of forged HS6‐5‐3 tool steel under high cycle fatigue
Authors: Giang Ngoc Anh , Özden Utku Ahmet , Bezold Alexander , Broeckmann Christoph 
Published: November 2013

AbstractDIN type forged HS6‐5‐3 tool steel (AISI M3:2) is most commonly used in tooling industry and also in some engine parts. Those components are usually exposed to cyclic mechanical stresses and 90% of them failed by fatigue damage. For predicting the life time of this tool steel under high cycle fatigue (HCF) a modified multistage fatigue model found by McDowell is proposed, which leads to reduce effects and cost for predicting life time of this material. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison between multi‐layered and functionally graded spherical pressure vessels
Authors: Arslan Eray 
Published: November 2013

AbstractTwo analytical models are developed for elastic multi‐layered and functionally graded thick walled spherical pressure vessels subjected to uniform internal pressure. Simple and comprehensive recursive algorithms are proposed for the multi‐layered vessel. In the model for functionally graded one, the modulus of elasticity is assumed to vary in radial direction according to a power law. Stress distributions of those vessels are compared and the results are presented in graphical form. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Developing a Simplified Surrogate Model for Structured Sheet Metals with Numerical and Experimental Comparisons
Authors: Mahler‐de Silva Tina , Kühhorn Arnold , Kober Markus 
Published: November 2013

AbstractIt is important to steadily refine lightweight designs with regard to saving resources and energy in common with good economic efficiency.Thin structured sheet metals offer significantly improved component stiffnesses in addition to an upgraded buckling behavior compared to flat, unstructured sheet metals.By using a distortion energy based homogenization method it is possible to develop a mechanical surrogate model which describes effective mean properties. The accurate selection of symmetric and periodic boundaries enables to determine the required parameters. The conditions are contemplated on elementary cells whose structural mechanical behavior is representative for the elastic behavior of large structures. By doing this, the amount of elements can be reduced and thus the calculating time of large components can considerably be saved.For an efficient surrogate model it is required to analyze and compare numerical with experimental investigations. Some different versions of optimization will be tested to get better approximation of the data. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fraeijs de Veubeke variational principle‐based cylindrical shell finite element model
Authors: Kocsán Lajos György 
Published: November 2013

AbstractIn this paper a dimensionally reduced cylindrical shell model based on the dual‐mixed variational principle of Fraeijs de Veubeke will be presented. The fundamental variables of this variational principle are the not a priori symmetric stress tensor and the skew‐symmetric rotation tensor. The tensor of first‐order stress functions is applied to satisfy translational equilibrium. A shell model derived in this way makes the application of the classical kinematical hypotheses unnecessary, and enables us to use unmodified three‐dimensional constitutive equations. On the basis of this shell model, a new dual‐mixed cylindrical shell finite elements capable of both h‐ and p‐approximation can be derived. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improving the numerical efficiency for 3D enhanced assumed strain finite elements in explicit time integration
Authors: Schmied Christoph , Mattern Steffen , Schweizerhof Karl 
Published: November 2013

AbstractExplicit time integration has proven to be highly suitable for the simulation of very fast processes and highly nonlinear applications. As is well known the time integration algorithm is only stable if the Courant‐Friedrichs‐Lewy criterion is fulfilled leading usually to very small time step sizes. As a result the efficiency of the time integration algorithm is dictated by the computational time of element operations. In structural mechanics low order finite elements are attractive due to their efficiency but introduce artificial stiffness effects. To resolve the so‐called locking effects a transient description – suitable for the solution in the context of explicit time integration – of the method of enhanced assumed strains (EAS) is formulated utilizing a generalization of the method of incompatible modes (IM). The element routines are computationally realised applying symbolic programming. The functionality and achieved efficiency are demonstrated on a numeric example. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)