bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Integration der Lebensdauerberechnung in den Fahrzeugentwicklungsprozess am Beispiel MIG‐geschweißter Bauteile aus Aluminium im Fahrwerksbereich
Authors: Brune M. , Oppermann H. , Chéreau S. , Pötter K. 
Published: September 2003

AbstractDie Lebensdauerberechnung für metallische Bauteile ist in der Ergebnisqualität wesentlich von den notwendigen Inputgrößen abhängig. Hierzu gehören die Finite‐Elemente‐Vernetzung des Bauteilmodells, die Werkstoffkennwerte und die zugrunde‐gelegten Last‐Zeitfunktionen, durch die das Bauteil beansprucht wird. In dieser Arbeit wird am Beispiel eines liniengeschweißten Fahrwerkbauteils aus Aluminium der Einfluss der Finite‐Elemente‐Modellierung auf die Lebensdauerberechnung unter‐sucht. Besonderes Augenmerk wird hier auf die Schweißnahtmodellierung gelegt. Für die Berechnung der Lebensdauer kommt das Software‐Werkzeug FEMFAT der Firma “Engineering Center Steyr” zum Einsatz. Die Bewertung der Lebensdauer für die Schweißnähte basiert hier auf einem örtlichen Spannungskonzept. Im folgenden wird die Qualifizierung der Berechnung für den Produktiveinsatz anhand von BMW‐typischen Schweißnaht‐Wöhlerlinien beschrieben.
Verhalten von Magnesiumlegierungen für Anwendungen im Fahrzeugbau bei mechanisch‐elektrochemischer Komplexbeanspruchung: Einfluss passivierender Deckschichten und Mechanismen der lokalen Schädigung
Authors: Berger C. , Troßmann T. , Gugau M. 
Published: September 2003

AbstractFür die Betriebssicherheit von Strukturbauteilen aus Magnesium ist es unerlässlich, dass alle maßgeblichen werkstofflichen, konstruktiven, fertigungsbedingten, betrieblichen und umgebungsbezogenen Einflussgrößen auf die Schwingfestigkeit bei der Bauteilauslegung berücksichtigt werden.Magnesiumlegierungen sind aufgrund der hervorragenden Verhältnisse von Festigkeit und Steifigkeit zur Dichte von besonderem Interesse für Leichtbauanwendungen. Das Korrosionsverhalten von Magnesium wird anwendungsspezifisch von den gleichen Faktoren wie bei anderen metallischen Werkstoffen bestimmt. Einerseits weist der Werkstoff Magnesium eine gute Stabilität unter atmosphärischen Umgebungsbedingungen, in alkalischen Medien sowie in Fluss‐ und Chromsäure auf. Andererseits wird durch die generelle hohe elektrochemische Aktivität die Bedeutung spezifischer Einflussfaktoren sehr stark hervorgehoben. Dies betrifft insbesondere die Ausbildung und Beständigkeit der vor Korrosion schützenden Deckschichten.Art, Zusammensetzung und Wirkung derartiger Schichten werden von folgenden Einflussfaktoren bestimmt: Legierungszusammensetzung, Passivierungsbedingungen, pH‐Wert, Elektrolytzusammensetzung sowie Art der Beaufschlagung und Temperatur.Bei lokaler Schädigung dieser so genannten Passivschichten und Anwesenheit eines wässrigen Mediums ist eine Verminderung der Beanspruchbarkeit von Bauteilen aus Magnesium zu beobachten. Ein Ziel diese Untersuchungen ist die Klärung von Mechanismen der Deckschichtschädigung. Im Wesentlichen sind für alle metallischen Konstruktionswerkstoffe zwei Mechanismen der Schädigung von Relevanz: einerseits ist dies die Ausbildung von Gleitstufen bei mechanischer Beanspruchung und andererseits die selektive elektrochemische Aktivierung (z.B. durch chloridinduzierte Lochkorrosion).Das Korrosionsverhalten hoch reiner Magnesiumlegierungen wurde in verschiedenen Lösungen (neutral, alkalisch, Wirkung spezifischer Anionen und Kationen) mit elektrochemischen Untersuchungsmethoden beschrieben. Die druckgegossenen Magnesiumlegierungen wurden wie hergestellt mit Gusshaut sowie mechanisch bearbeitet untersucht. Die Bewertung der erhaltenen Befunde verdeutlicht, dass in Abhängigkeit des Systems Legierung/Werkstoff‐ und Oberflächenzustand/Umgebungsbedingungen verschiedene Mechanismen der Schädigung der schützenden Deckschichten möglich sind. Weiterhin wird das Verhalten bei Schwingungsrisskorrosion wesentlich durch den Zustand der Bauteiloberfläche sowie die Prüfbedingungen beeinflusst.
Lebensdauerermittlung bei mehrachsigen wechselnden Beanspruchungen im niedrigen und hohen Temperaturbereich
Authors: Roos E. , Gengenbach T. , Rauch M. , Schemmel J. 
Published: September 2003

AbstractZur Berechnung der Dauerfestigkeit von Bauteilen aus duktilen Werkstoffen bei komplexer Schwingbeanspruchung stehen unterschiedliche Verfahren zur Verfügung. Hierbei wird im Wesentlichen zwischen den Festigkeitshypothesen der Integralen Anstrengung und denen der Kritischen Schnittebene unterschieden. Als typische Repräsentanten werden die Schubspannungsintensitätshypothese (SIH) sowie die Methode der kritischen Schnittebene (MKS) ausgewählt und für körperfeste und nicht körperfeste Hauptspannungsrichtungen gegenübergestellt. Für synchrone Beanspruchungen wird darüber hinaus das Berechnungsverfahren mit dem Anstrengungsverhältnis nach Bach verglichen.Die Berechnungsmethodik wird deutlich komplexer, wenn zeitabhängige Werkstoffeigenschaften bei entsprechend hohen Temperaturen mit in die Betrachtung einbezogen werden müssen. Für diesen Fall wird die Anwendung von viskoplastischen Stoffgesetzen erforderlich, die eine Beschreibung von Kriechen und Ermüdung in Kombination ermöglichen. Am Beispiel eines modifizierten Werkstoffmodells nach Chaboche / Nouailhas wird die Berechnung mehrachsiger Kriechermüdungsversuche vorgestellt.
Singularity extraction technique for integral equation methods with higher order basis functions on plane triangles and tetrahedra
Authors: Järvenpää Seppo , Taskinen Matti , Ylä‐Oijala Pasi 
Published: September 2003

AbstractA numerical solution of integral equations typically requires calculation of integrals with singular kernels. The integration of singular terms can be considered either by purely numerical techniques, e.g. Duffy's method, polar co‐ordinate transformation, or by singularity extraction. In the latter method the extracted singular integral is calculated in closed form and the remaining integral is calculated numerically. This method has been well established for linear and constant shape functions. In this paper we extend the method for polynomial shape functions of arbitrary order. We present recursive formulas by which we can extract any number of terms from the singular kernel defined by the fundamental solution of the Helmholtz equation, or its gradient, and integrate the extracted terms times a polynomial shape function in closed form over plane triangles or tetrahedra. The presented formulas generalize the singularity extraction technique for surface and volume integral equation methods with high‐order basis functions. Numerical experiments show that the developed method leads to a more accurate and robust integration scheme, and in many cases also a faster method than, for example, Duffy's transformation. Copyright © 2003 John Wiley & Sons, Ltd.
Quasi‐dual reciprocity boundary‐element method for incompressible flow: Application to the diffusive–advective equation
Authors: Loeffler C. F. , Mansur W. J. 
Published: September 2003

AbstractThis work presents a new boundary‐element method formulation called quasi‐dual reciprocity formulation for heat transfer problems, considering diffusive and advective terms. The present approach has some characteristics similar to those of the so‐called dual‐reciprocity formulation; however, the mathematical developments of the quasi‐dual reciprocity approach reduces approximation errors due to global domain interpolation. Some one‐ and two‐dimensional examples are presented, the results being compared against those obtained from analytical and dual‐reciprocity formulations. The method convergence is evaluated through analyses where the mesh is successively refined for various Peclet numbers, in order to assess the effect of the advective term. Copyright © 2003 John Wiley & Sons, Ltd.
Structural design optimization on thermally induced vibration
Authors: Chen Biaosong , Gu Yuanxian , Zhang Hongwu , Zhao Guozhong 
Published: September 2003

AbstractThe numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in the software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal‐induced vibration coupled with both linear and non‐linear transient heat conduction is firstly proposed. Based on the finite element method, the linear structural dynamics is treated simultaneously with linear and non‐linear transient heat conduction. In the heat conduction, the non‐linear factors include the radiation and temperature‐dependent materials. The sensitivity analysis of transient linear and non‐linear heat conduction is performed with the precise time integration method; and then, the sensitivity analysis of structural transient responses is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration. In the adjoint method, two adjoint vectors of structure and of heat conduction are used to derive the adjoint equations. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With the coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. Numerical examples are given to validate the proposed methods and to demonstrate the importance of the coupled design optimization. Copyright © 2003 John Wiley & Sons, Ltd.
A posteriori error estimates and an adaptive scheme of least‐squares meshfree method
Authors: Park Sang‐Hoon , Kwon Kie‐Chan , Youn Sung‐Kie 
Published: September 2003

AbstractA posteriori error estimates and an adaptive refinement scheme of first‐order least‐squares meshfree method (LSMFM) are presented. The error indicators are readily computed from the residual. For an elliptic problem, the error indicators are further improved by applying the Aubin–Nitsche method. It is demonstrated, through numerical examples, that the error indicators coherently reflect the actual error. In the proposed refinement scheme, Voronoi cells are used for inserting new nodes at appropriate positions. Numerical examples show that the adaptive first‐order LSMFM, which combines the proposed error indicators and nodal refinement scheme, is effectively applied to the localized problems such as the shock formation in fluid dynamics. Copyright © 2003 John Wiley & Sons, Ltd.
Near‐crack contour behaviour and extraction of log‐singular stress terms of the self‐regular traction boundary integral equation
Authors: Jorge Ariosto B. , Cruse Thomas A. , Fisher Timothy S. 
Published: September 2003

AbstractThis work contains an analytical study of the asymptotic near‐crack contour behaviour of stresses obtained from the self‐regular traction‐boundary integral equation (BIE), both in two and in three dimensions, and for various crack displacement modes. The flat crack case is chosen for detailed analysis of the singular stress for points approaching the crack contour. By imposing a condition of bounded stresses on the crack surface, the work shows that the boundary stresses on the crack are in fact zero for an unloaded crack, and the interior stresses reproduce the known inverse square root behaviour when the distance from the interior point to the crack contour approaches zero. The correct order of the stress singularity is obtained after the integrals for the self‐regular traction‐BIE formulation are evaluated analytically for the assumed displacement discontinuity model. Based on the analytic results, a new near‐crack contour self‐regular traction‐BIE is proposed for collocation points near the crack contour. In this new formulation, the asymptotic log‐singular stresses are identified and extracted from the BIE. Log‐singular stress terms are revealed for the free integrals written as contour integrals and for the self‐regularized integral with the integration region divided into sub‐regions. These terms are shown to cancel each other exactly when combined and can therefore be eliminated from the final BIE formulation. This work separates mathematical and physical singularities in a unique manner. Mathematical singularities are identified, and the singular information is all contained in the region near the crack contour. Copyright © 2003 John Wiley & Sons, Ltd.
On discontinuous Galerkin methods
Authors: Zienkiewicz O. C. , Taylor R. L. , Sherwin S. J. , Peiró J. 
Published: September 2003

AbstractDiscontinuous Galerkin methods have received considerable attention in recent years for problems in which advection and diffusion terms are present. Several alternatives for treating the diffusion and advective fluxes have been introduced. This report summarizes some of the methods that have been proposed.Several numerical examples are included in the paper. These present discontinuous Galerkin solutions of one‐dimensional problems with a scalar variable. Results are presented for diffusion–reaction problems and advection–diffusion problems. We discuss the performance of various formulations with respect to accuracy as well as stability of the method. Copyright © 2003 John Wiley & Sons, Ltd.
Molecular orientation gradients in thermotropic liquid crystalline fiber
Authors: Taylor Jennifer E. , Romo‐Uribe Angel , Libera Matthew R. 
Published: September 2003

AbstractThe degree of molecular alignment averaged over meso‐length scale areas within thermotropic liquid crystalline polymer (LCP) fibers has been intensely studied over recent years. In this work, the degree of molecular orientation is found from spatially‐resolved electron diffraction of areas as small as 100 nm in diameter to relieve structural averaging of lower resolution techniques. This investigation reveals that the maximum degree of molecular alignment across a fiber 18 μm in diameter is approximately 1 μm from the fiber surface. Dark‐field imaging shows region with little crystallinity adjacent to the fiber surface. The banded structure, typical of TLCP fibers, is also less apparent in the surface region. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and functional properties of green fluorescent poly(methylmethacrylate) for use in liquid crystal systems
Authors: Grabchev Ivo , Chovelon Jean‐Marc 
Published: September 2003

AbstractThe copolymerization of six 4‐aminosubstituted‐1,8‐naphthalimide dyes comprising an allylic polymerizable group with methylmethacrylate has been investigated. The utility of the copolymers prepared as fluorescent component in polymer/liquid crystal systems has been examined. The photophysical and photochemical properties of the systems monomeric dye/liquid crystal and copolymer/liquid crystal have been also discussed. It has been shown that in a liquid crystal mixture 1,8‐naphthalimide dyes and respective copolymer/liquid crystals have yellow–green fluorescent color with good photostability. Copyright © 2003 John Wiley & Sons, Ltd.
UV curing behaviors and hydrophilic characteristics of UV curable waterborne hyperbranched aliphatic polyesters
Authors: Asif Anila , Huang Chengyu , Shi Wenfang 
Published: September 2003

AbstractA series of waterborne hyperbranched polyesters (WBHPs) endcapped with methacrylic and salt‐like groups in different ratios have been investigated as UV curable resins. The kinetic studies of the drying step and UV curing were carried out by FT‐IR measurements. The drying of the film of 100 μm thickness was completed in less than 6 hr at 70°C or within 10 hr at 50°C in an oven. The influence of different photoinitiators and their concentrations, extent of unsaturation and acid content of WBHP on final unsaturation conversion was studied. The surface free energy is a critical character, which affects the surface properties of a cured film. So one method based on the measurement of contact angle of a pure liquid on a solid surface was applied to determine the polar and dispersive components of the surface energy of UV cured films. The investigations of surface energy of WBHPs illustrated that those with more acid content and thus higher polar component are more sensitive to water, while those containing less acid content and thus lower polar term are less water sensitive. Moreover, the UV cured films of WBHPs and their blends with commercial waterborne resins (trade name EB 210, EB 2002, EB 11 and IRR 160) have acceptable pendulum hardness varying from 55 to 180 sec. Copyright © 2003 John Wiley & Sons, Ltd.
Short communication the preparation of stable protected 3‐ethynylpyrrole suitable for electrochemical polymerization
Authors: Hlavatý Jaromír , Kubišta Jiří , Štícha Martin 
Published: September 2003

AbstractStable protected 3‐triisopropylsilylethynylpyrrole, 4b, was prepared in the yield 73% by first observed selective deprotection of double protected 1‐triisopropylsilyl‐3‐triisopropylsilylethynylpyrrole, 3b, which was obtained in the yield 44%. This deprotection in preference proceeds at the pyrrole nitrogen leaving the 3‐triisopropylsilylethynyl group intact. Due to its stability, ethynylpyrrole derivative 4b protected was like the first alkynyl pyrrole derivative electrochemically polymerized giving a black polypyrrole layer deposited on the platinum anode. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and characterization of cellulose resins
Authors: El‐Zawawy Waleed K. , Ibrahim Maha M. 
Published: September 2003

AbstractA series of cellulose‐phenol‐formaldehyde (LCPF) and cellulose‐urea‐formaldehyde (CUF) resins were produced using banana waste. Detailed structure and quantitative information was provided by FT‐IR and mass spectroscopy. The main interests were the ability to use banana waste as a source of cellulose in the condensation reaction. Functionality of CPF and structure of CUF were investigated. Copyright © 2003 John Wiley & Sons, Ltd.
Anion exchange fibers for arsenate removal derived from a vinylbenzyl chloride precursor
Authors: Dominguez Lourdes , Economy James , Benak Kelly , Mangun Christian L. 
Published: September 2003

AbstractThe preparation of anionic exchange fibers (AEFs) is described utilizing an oligomer derived from vinylbenzyl chloride as the precursor coating on a glass fiber substrate. This approach permits a significant reduction in number of synthetic steps required for commercial beads, as well as eliminating the need for solvents prior to functionalization. The amination reaction time was also substantially reduced. These fibers were characterized through a variety of techniques such as scanning electron microscopy (SEM), analytical titration, and diffuse reflectance fourier transform infrared spectroscopy (DRIFTS) of the copolymer. With respect to ion exchange properties the fibers could be regenerated for over 20 cycles with no capacity loss or physical degradation of the coating. Particular emphasis was placed on establishing conditions for the removal of arsenate from water. The design and testing of AEF filters for breakthrough experiments were carried out and compared to commercially available beads. The results indicate that AEF have a significant kinetic advantage over the anionic exchange beads, which approaches an order of magnitude improvement in lowering effluent contaminants. Copyright © 2003 John Wiley & Sons, Ltd.
Flame retardancy and heat resistance of phenol‐biphenylene‐type epoxy resin compound modified with benzoguanamine
Authors: Iji Masatoshi , Kiuchi Yukihiro , Soyama Makoto 
Published: September 2003

AbstractThe flame retardancy and heat resistance of a phenol‐biphenylene‐type epoxy resin compound, which forms a self‐extinguishing network structure, were increased by the inclusion of a benzoguanamine‐modified phenol biphenylene resin. The benzoguanamine‐modified phenol biphenylene resin contains a benzoguanamine unit to release non‐flammable nitrogen substances during ignition and to increase the resin's reactivity toward epoxy resins, and biphenylene units to keep the resin's thermal degradation and water resistance. The addition of the benzoguanamine‐modified phenol biphenylene resin in the epoxy resin compound improved the epoxy resin compound's flame retardancy and heat resistance, and also increased its glass transition temperature while maintaining its water resistance and mechanical properties. Copyright © 2003 John Wiley & Sons, Ltd.
Morphology and degradation of biodegradable poly(L‐lactide‐co‐β‐malic acid)
Authors: He Bin , Bei Jianzhong , Wang Shenguo 
Published: September 2003

AbstractPoly(L‐lactide‐co‐β‐malic acid) was obtained after the hydrogenolysis of the copolymer of L‐lactide (L‐LA) and β‐benzyl malate (MA). 1H‐NMR demonstrated that the composition of the copolymer was identical to the feeding dose. Thermal property study revealed the morphology of the copolymer could be changed from semi‐crystalline to amorphous with increasing hydrophilic β‐malic acid content. The copolymers with 8 and 13 mol% β‐malic acid content possessed enough mechanical property for fabricating cell scaffold. Degradation result demonstrated that most of the hydrophilic β‐malic acid units broke down from the copolymer within 1 week and the ester bond between L‐lactide and β‐malic acid hydrolyzed prior to the inner ester bond of poly(L‐lactide) (PLLA). Copyright © 2003 John Wiley & Sons, Ltd.
Direct current electric‐field induced scattering behavior in lyotropic liquid crystalline cell composed of carbazolyl groups pendant polypeptide and TNF
Authors: Naijo Yoshihisa , Fujisaki Eita , Tsunoda Makoto , Tanaka Toyohide , Kobayashi Norihisa 
Published: September 2003

AbstractPolypeptide having carbazolyl groups (poly(γ‐[2‐(9‐carbazolyl)ethyl]‐L‐glutamate) (PCLG)) was synthesized in order to prepare a lyotropic liquid crystalline cell with higher mobility. This liquid crystal was revealed to show d.c. electric‐field induced scattering behavior, in which the transparent cell became scattered after applying d.c. bias voltage. This behavior was enhanced by adding small amounts of 2,4,7‐trinitrofluorenone (TNF) which is known to form charge transfer complex with carbazole. The transmittance varied from 90 to 20% under d.c. bias application. More than 150 turn‐on and off cycles were achieved in this cell without serious degradation. Copyright © 2003 John Wiley & Sons, Ltd.