bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of critical strains and loads in layered composites
Authors: Menshykov Oleksandr V. , Guz Igor A. , Menshykova Maryna V. 
Published: January 2007

AbstractThe present work is devoted to investigation of the compressive fracture for piecewise homogeneous materials with specific kinds of delaminations (defects with connected edges). The critical buckling strains and loads at which ply instability in laminated composites occurs under uniaxial and biaxial compression were evaluated. Different types of layers (linear elastic, elastic‐plastic, hyper‐elastic incompressible) were investigated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isotropic softening model for high‐cycle fatigue
Authors: Paluszyński B. , Schnack E. 
Published: January 2007

AbstractAs known the high cycle loading of structural elements above the fatigue limit results in catastrophic propagation of macroscopic fatigue crack(s). Therefore it is in demand to find a method, which would allow for early prediction of the fatigue life‐time of particular structural element.The series of force‐driven tests carried on 30CrNiMo8 steel have shown that, although the stresses by high‐cycle fatigue do not reach the tensile stress, the material strength (measured indirectly from the strain‐stress loop) decreases from the begin of the test, hence the damage nucleates and propagates from the very begin of the loading history.In this study we propose a thermodynamically consistent, strain driven constitutive model for isotropic damage accumulation by high‐cycle fatigue of a homogeneous isotropic material, which should be capable to account for the above‐mentioned experimental results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of free‐edge effects by boundary finite element method
Authors: Artel Jens , Becker Wilfried 
Published: January 2007

AbstractThe scaled boundary finite element method is a novel semi‐analytical analysis technique that combines the advantages of the finite element method and the boundary element method. Only a part of the boundary of the considered domain has to be discretized but nevertheless the method is solely finite element based. The governing equations are solved in the so‐called scaling direction analytically, whereas a finite element approximation of the solution is performed in the circumferential directions, which form the boundary of the considered domain. Thus, the numerical effort can be reduced considerably when handling stress concentration problems such as e.g. the free‐edge effect in laminated plates. In order to analyze the free‐edge effect in a semi‐infinite half plane, some kinematic coupling equations have to be introduced, that not only couple the degrees of freedom on the boundary, but also within the non‐discretized domain. The implementation of kinematic coupling equations within the method is presented. Finally, the efficiency of the new approach is shown in some benchmark examples. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mehrskalenberechnungen bei inhomogenen Körpern
Authors: Bitzenbauer Johann , Schweizerhof Karl 
Published: January 2007

AbstractDie Finite‐Elemente‐Untersuchung linearer und nichtlinearer Randwertprobleme der Elastizitätstheorie führt bei vorhandenen und durchgängig diskretisierten Mikrostrukturen üblicherweise auf sehr große dünnbesetzte Gleichungssysteme. Als ein ef.zientes Lösungsverfahren empfehlen sich Mehrgittermethoden. Während bei klassischen Mehrgitterverfahren die minimale Anzahl der zur Geometriebeschreibung notwendigen Finiten Elemente von der Geometrie selbst abhängig ist, besteht bei der Composite‐Finite‐Elemente‐Methode (CFE) ein gröbstmögliches Gitter zur Diskretisierung einer beliebigen Geometrie stets aus einem Element [1]. Ein auf der CFE‐Methode basierender Mehrgitteralgorithmus nebst zugehörigen Transferoperatoren zur Berechnung elastischer Körper wird vorgestellt. Im Gegensatz zu algebraischen Mehrgittermethoden, bei denen zur Konstruktion der Transferoperatoren die Stei.gkeitsmatrizen des diskretisierten Problems herangezogen werden, nutzt der präsentierte Algorithmus Geometrieinformationen aus, ohne dabei jedoch die beim klassischen geometrischen Mehrgitterverfahren auftretenden Einschränkungen zu besitzen. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High order FE and covariant description for contact problems
Authors: Konyukhov Alexander , Schweizerhof Karl 
Published: January 2007

AbstractThe covariant contact description is applied to incorporate the treatment of contact problems into the high‐order finite element technique. A hierarchical enrichment of the Ansatz space allows to construct a contact layer finite element combining both an exact geometry for contact surfaces, and a mesh with linear Ansatz functions for the interior of the contacting bodies. Good correlation with the Hertz problem is shown even within a few contact elements for the contact zone, however, not in general. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical instabilities in structural optimization – analogy between topology & shape design problems
Authors: Kotucha Gregor , Hackl Klaus 
Published: January 2007

AbstractThe formulation of structural optimization problems on the basis of the finite–element–method often leads to numerical instabilities resulting in non–optimal designs, which turn out to be difficult to realize from the engineering point of view. In the case of topology optimization problems the formation of designs characterized by oscillating density distributions such as the well–known “checkerboard–patterns” can be observed, whereas the solution of shape optimization problems often results in unfavourable designs with non–smooth boundary shapes caused by high–frequency oscillations of the boundary shape functions. Furthermore a strong dependence of the obtained designs on the finite–element–mesh can be observed in both cases. In this context we have already shown, that the topology design problem can be regularized by penalizing spatial oscillations of the density function by means of a penalty–approach based on the density gradient. In the present paper we apply the idea of problem regularization by penalizing oscillations of the design variable to overcome the numerical difficulties related to the shape design problem, where an analogous approach restricting the boundary surface can be introduced. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of Daubechies wavelets approximation to plate bending
Authors: Kozbial Tomasz 
Published: January 2007

AbstractIn this paper a new wavelet‐based approach is presented for solving two‐dimensional boundary‐value mechanical problems on the example of plate bending. The deflection equation of a bending plate is approximated by two‐dimensional Daubechies wavelets using a least‐squares Galerkin method. Due to the order of the differential equation in mechanics of plate structures is four, a way to perform the calculations of high order connection coefficients (that is, integrals of products of basis functions with their high order derivatives) is suggested. The implementation of two‐dimensional Daubechies scaling functions approximation to plate bending is exhibited numerically in some examples. The results show that this method has good precision and reliability. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental analysis of shrouded blades with friction contact
Authors: Schmidt‐Fellner A. , Siewert C. , Panning L. 
Published: January 2007

AbstractTurbine blades are subjected to high thermal and mechanical loads. Damages at the blades are frequent causes for the failure of turbomachines. To reduce the vibration amplitudes and the resulting dynamic stresses, friction damping devices are widely used. Because of the relative displacements in the contact between the friction damping devices and the blades, additional damping is generated due to energy dissipation.At simulations a close description of the forces in the friction contact and a mathematical implementation of the mechanical contact model is necessary to optimize the friction damping devices. In this paper experimental measurements of heated blades coupled by tip shrouds are presented. The application of the calculation method to experimental measurements gives an insight in the influence of the temperature towards the contact parameters, especially the coefficient of friction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
“New” branched structures of mechanical systems as result of synthesis of selected class of dynamical characteristics
Authors: Buchacz Andrzej 
Published: January 2007

AbstractIn this paper the problem of synthesis has been formulated and its basics has been formalized, according to the discrete mechanical systems with branched structure represented by graphs. In this case the essential field of basic conceptions according to the concerned class of structures and used graphs has been described. The way of receiving “new” structures as a result of synthesis of characteristics into partial fraction has been presented farther on. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Friction Modes in Low Frequency disc‐brake noise ‐ experimental results and implications on modelling
Authors: Hetzler Hartmut , Seemann Wolfgang 
Published: January 2007

AbstractToday, low frequency disc‐brake noises are commonly explained as self‐sustained stick‐slip oscillations. Although, at a first glance this explanation seems reasonable, there are indications that cast doubt on it. Indeed, experimental studies on groaning noises reveal two qualitatively totally different vibration patterns: stick‐slip vibrations at almost vanishing relative speeds and another vibration pattern at low to moderate relative speeds. Within this article, experimental results are presented and discussed. Based on this, suggestions for appropriate mechanical models are derived. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiple Impacts of Transversely Struck Aluminum Beams
Authors: Seifried Robert 
Published: January 2007

AbstractTransverse impacts of steel spheres on aluminum beams are investigated numerically and experimentally. For the numerical investigation, modally‐reduced models are used in combination with local Finite Element contact models. The proposed numerical models are verified by extensive experimental investigations using Laser‐Doppler‐Vibrometers. The numerical and experimental investigations show that impacts of steel spheres on aluminum beams yield strong structural vibrations causing multiple successive impacts. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A vertically acting tuned liquid column damper
Authors: Ziegler Franz 
Published: January 2007

AbstractThe U‐shaped tuned liquid column damper (TLCD) increases the effective structural damping of horizontal vibrations similar to the classical tuned mechanical pendulum type damper (TMD). The pipe‐in‐pipe TLCD applies to vertical vibrations, likewise to the spring‐mass‐dashpot TMD. When sealed, the gas‐spring effect extends the frequency range of application to about five Hertz. The geometric analogy between the novel TLCD and the TMD still exists, making the first step in the tuning procedure “classical”. Subsequent fine tuning in state space when the TLCD is split into smaller ones in parallel action, renders an even more robust passive action. The experimentally observed averaged turbulent damping of the relative fluid flow and the weakly nonlinear gas‐spring render the TLCD insensitive to overloads and parametric forcing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global solution on Cauchy problem in nonlinear non‐simple thermoelastic materials
Authors: Gawinecki Jerzy August , Łazuka Jarosław 
Published: January 2007

AbstractWe prove a theorem about global existence (in time) of the solution to the initial‐value problem for a nonliear system of coupled partial differential equations of fourth order describing the thermoelasticity of non‐simple materias. We consider such the case of thim system in which some nonlinear coeffcients can depend not only on the temperature and the gradient of displacement and also on the second derivative of displacement. The corresponding global existence theorem has been proved using the L p – L q time decay estmates for the solution of the associated linearized problem.Next, we proved the energy estimate in the Sobolev space with constant independent of time.Such an energy estimate allows us to apply the standard continuation argument and to continue the local solution to one desired for all t ∈ (0, ∞)
Heat conduction in laminates with a weak transversal inhomogeneity
Authors: Lacinski Lukasz , Wozniak Czeslaw 
Published: January 2007

AbstractThe purpose of this contribution is to formulate a tolerance model, [1], for periodically laminated media with a weak transversal inhomogeneity. Laminates in which layers are of the same material but one of them is reinforced by thin fibers in parallel to the interfaces are this kind of media. Taking into account the weak transversal inhomogeneity makes possible to separate model equations for the averaged temperature and temperature fluctuations. To analyse and solve these equations we apply asymptotic expansions. Using the proposed model selected initial‐boundary value problems were solved. Results were verified by direct numerical solutions obtained in the framework of the Fourier model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Asymmetric Effects in Plasticity
Authors: Mahnken Rolf 
Published: January 2007

AbstractIn the framework of plasticity the simulation of materials is addressed, which experimentally exhibit different behavior in different loading scenarios, such as tension, compression and shear. To this end an additive decomposition of the yield function and the plastic potential, is assumed into a sum of weighted stress mode related quantities. The characterization of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the Lode angle, such that stress mode dependent scalar weighting functions can be constructed. Verification of the proposed methodology is succeeded for simulation of the pseudoelastic behavior of shape memory alloys with different hardening characteristics in tension and shear. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling Phase Separation and Coarsening in Ag‐Cu
Authors: Müller Wolfgang H. , Böhme Thomas 
Published: January 2007

AbstractThe ongoing miniaturization and environmental trends in microelectronics recently turn the attention to new materials the properties of which still have to be studied. Of fundamental importance for material properties is the temporal development of the microstructure which can experimentally be observed in several solder alloys. Starting with a detailed overview on coarsening phenomena and intermetallic growth as observed in lead‐free solders we concentrate on the description of nucleation and spinodal decomposition in these alloys. An extended diffusion equation of the phase field type is presented in which all required material parameters are determined either from the literature / databases or from calculations based on the Embedded‐Atom Method (EAM). We will restrict to the one dimensional case of diffusion and consider as an example the FCC‐structured lead‐free binary solder alloy Ag‐Cu. Furthermore a numerical study is performed in order to arrive at a quantitative description of temporal micromorphological development. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear deformation of Three‐Component Composites
Authors: Nazarenko Lidija 
Published: January 2007

AbstractThe model of nonlinear deformation of stochastic composites under microdamaging is developed for the case of threecomponent composite, when the microdamages are accumulated in the matrix. The composite is treated as isotropic matrix strengthened by two different types of spheroidal inclusions with transversally‐isotropic symmetry of elastic properties. Fractured microvolumes are modeled by a system of randomly distributed quasispherical pores. The porosity balance equation and relations for determining the effective elastic modules for the case of transversally‐isotropic components are taken as basic relations. The fracture criterion is assumed to be given as the limit value of the intensity of average shear stresses occurring in the undamaged part of the material. The algorithm for determination of nonlinear deformative properties of such a material is constructed. The nonlinear stress‐strain diagrams for three‐component concrete for the case of uniaxial tension are obtained. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non–Isothermal Shear Band Localization in Crystal Plasticity
Authors: Rosato Daniele , Miehe Christian 
Published: January 2007

AbstractWe analyze the formation of shear bands in plastically deforming single crystals under non‐isothermal quasi‐static loading conditions. A key feature of the present work is to motivate the constitutive coupled thermomechanical equations for the slip resistance and the slip evolution by micromechanical investigations of defects in crystals. Here, we put particular emphasis on comparative investigations of hardening–softening effects of crystals under non‐isothermal conditions, including a quantification of the latent energy storage. Furthermore, we analyze a numerical solution algorithm for the coupled thermomechanical problem and we test the performance on a typical benchmark example of finite‐strain single‐crystal thermoplasticity: the localization of deformation into a shear band for the case of a rectangular strip. Experimental evidence for this problem is well documented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Material‐Force‐Based Refinement Indicators in Adaptive Strategies
Authors: Zimmermann Dominik , Miehe Christian 
Published: January 2007

AbstractA material‐force‐based refinement indicator for adaptive finite element strategies for finite elasto‐plasticity is proposed. Starting from the local format of the spatial balance of linear momentum, a dual material counterpart in terms of Eshelby's energy‐momentum tensor is derived. For inelastic problems, this material balance law depends on the material gradient of the internal variables. In a global format the material balance equation coincides with an equilibrium condition of material forces. For a homogeneous body, this condition corresponds to vanishing discrete material nodal forces. However, due to insufficient discretization, spurious material forces occur at the interior nodes of the finite element mesh. These nodal forces are used as an indicator for mesh refinement. Assigning the ideas of elasticity, where material forces have a clear energetic meaning, the magnitude of the discrete nodal forces is used to define a relative global criterion governing the decision on mesh refinement. Following the same reasoning, in a second step a criterion on the element level is computed which governs the local h‐adaptive refinement procedure. The mesh refinement is documented for a representative numerical example of finite elasto‐plasticity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Single thermoplastic pellet molding by means of diode laser for micromolding application
Authors: Citrea Isabella , Quadrini Fabrizio 
Published: January 2007

AbstractAn innovative system for thermoplastic micromolding is presented. A completely transparent mold is used, and a diode laser is used as heating source. Laser heating is performed on a single thermoplastic pellet positioned inside the mold between two glass plates. A very low force is necessary for shaping. Molding tests were performed on commercial ABS and several process parameters were investigated such as laser power, interaction time, focalization condition, and support material properties. High pellet formability was observed in all the cases. Using nontransparent pellet supports it is possible to increase molding efficiency even if the risk of polymer degradation increases. A master curve can be fabricated for molding test results providing a correct comparison among the different process conditions. POLYM. ENG. SCI., 47:168–173, 2007. © 2007 Society of Plastics Engineers
Molecular modeling of poly(p‐phenylenevinylene): Synthesis and photophysical properties of oligomers
Authors: Jiu Tonggang , Li Yuliang , Liu Xiaofeng , Liu Huibiao , Li Cuihong , Ye Jianping , Zhu Daoben 
Published: January 2007

AbstractA series of oligo(phenylenevinylene)s (OPVs) of different lengths containing aldehyde and dialdehyde groups on the ends were synthesized and characterized. Their photophysical properties were also investigated via ultraviolet–visible, steady‐state, and time‐resolved fluorescence spectra. The results indicated that the absorption maximum, radiative rate constant, and excitation maximum of an OPVnCHO oligomer series (where n represents the oligomeric length) showed linear relationships with the reciprocal number of conjugated units. Similarly, the absorption maximum and emission lifetime of the oligomers of an OPVn–2CHO series showed linear relationships with the reciprocal number of conjugated units. The dependence of the fluorescence intensities of the OPVs on the concentration of the quencher C60 was evaluated. Apparently, upon photoexcitation, the OPVs underwent significant fluorescence quenching. The results for different OPV derivatives and a quenching mechanistic discussion showed that the static quenching contribution was indeed responsible for the significant upward curvature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 911–924, 2007
Thermal quenching of luminescence and isovalent trap model for rare‐earth‐ion‐doped AlN
Authors: Lozykowski H. J. , Jadwisienczak W. M. 
Published: January 2007

AbstractInvestigations of the luminescent properties of Pr‐, Eu‐, Tb‐ and Tm‐implanted AlN thin films at temperature in the range 9–830 K are reported. The temperature studies of photoluminescence and cathodoluminescence spectra revealed unexpectedly weak thermal quenching for all investigated rare earth (RE) ions. The maximum CL emission is observed from Eu (red) at 485 K, Tb (green) at 590 K and Tm (blue) at 530 K, respectively. For Tb‐ and Tm‐doped AlN samples, temperature‐dependent crossrelaxation processes were observed. Photoluminescence excitation spectra, obtained under UV excitation in the spectral range 200–400 nm, exhibit several bands. It is proposed that the RE ions exist in semiconductors as isolated ions (singlet), nearest‐neighbor (nn) ion pairs (dimer), and three ions (trimer). The Koster–Slater and simple spherical potential‐well models for RE‐structured isovalent (RESI) hole trap are proposed. The exciton binding energies of RESI traps are calculated and compared with experimental thermal‐quenching energies. The energy‐transfer processes between the AlN host and the 4f‐shell systems are emphasized as the main mechanisms for thermal‐quenching processes rather than nonradiative decay of 4f transitions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrating maintenance activities and Quality Assurance in a research and development (R&D) system
Authors: Basak Debasish 
Published: January 2007

AbstractA well‐balanced maintenance program furnishes information and instructions to personnel involved in maintaining existing equipment, provides current information on the availability and location of maintenance materials, improves utilization of labor forces and increases equipment reliability. Planned and preventive maintenance procedures where components are serviced and changed when they approach the end of their useful lives can be augmented by suitable means, which continuously check vital machine functions. Quality Assurance can be seen as a management system that brings maintenance activities undertaken by all parties under control with the aim of preventing things from going wrong and costing time, effort and money to put them right. An attempt has been made to highlight the integration of maintenance activities with Quality Assurance as a whole in a research and development (R&D) system. Copyright © 2006 John Wiley & Sons, Ltd.