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Development of a Three-Dimensional Multiscale Octree SBFEM for Viscoelastic Problems of Heterogeneous Materials

Computer Modeling in Engineering & Sciences 2024年第8期140卷 1831-1861页

作者： Xu Xu Xiaoteng Wang Haitian Yang Zhenjun Yang Yiqian He State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDepartment of Engineering MechanicsDalian University of TechnologyDalian116024China Hubei Key Laboratory of Geotechnical and Structural Safety School of Civil EngineeringWuhan UniversityWuhan430072China mechanik–materialtheorie Ruhr-Universität BochumBochum44801Germany

The multiscale method provides an effective approach for the numerical analysis of heterogeneous viscoelastic materials by reducing the degree of freedoms(DOFs).A basic framework of the Multiscale Scaled Boundary Finite Element Method(MsSBFEM)was presented in our previous works,but those works only addressed two-dimensional *** order to solve more realistic problems,a three-dimensional MsSBFEM is further developed in this *** the proposed method,the octree SBFEM is used to deal with the three-dimensional calculation for numerical base functions to bridge small and large scales,the three-dimensional image-based analysis can be conveniently conducted in small-scale and coarse nodes can be flexibly adjusted to improve the computational ***,the Temporally Piecewise Adaptive Algorithm(TPAA)is used to maintain the computational accuracy of multiscale analysis by adaptive calculation in time *** results of numerical examples show that the proposed method can significantly reduce the DOFs for three-dimensional viscoelastic analysis with good *** instance,the DOFs can be reduced by 9021 times compared with Direct Numerical Simulation(DNS)with an average error of 1.87%in the third example,and it is very effective in dealing with three-dimensional complex microstructures directly based on images without any geometric modelling process.

关键词： Three-dimensionalmultiscale viscoelastic analysis numerical base functions octree SBFEM image-based analysis temporally piecewise adaptive algorithm

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A theoretical justification of the slip index concept in fretting analysis

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Friction 2023年第7期11卷 1265-1275页

作者： Ivan I.ARGATOV Young S.CHAI Institut für mechanik Technische Universität Berlin10623 BerlinGermany School of Mechanical Engineering Yeungnam UniversityGyeongsan 712-749Republic of Korea

Fretting in the partial-slip and gross-slip regimes under a constant normal load is *** tangential force-displacement relations for the forward and backward motions are described based the generalized Cattaneo-Mindlin theory of tangential contact and Masing's hypothesis on modelling the force-displacement hysteretic *** the critical force and displacement parameters(characterizing the triggering of sliding),the model includes one dimensionless fitting parameter that tunes the tangential contact stiffness of the friction-contact *** expressions are derived for the main tribological parameters of the fretting loop,including the slip index and the signal *** presented phenomenological modelling approach has been applied to the analysis of two sets of experimental data taken from the *** has been shown that the experimentally observed simple relation of a rational type between the slip index and the slip ratio corresponds to the gross-slip asymptotics of the corresponding model-based predicted *** known quantitative criteria for the transition from the partial slip regime to the gross slip regime are expressed in terms of the stiffness parameter,and a novel geometric transition criterion is formulated.

关键词： fretting wear slip index signal index partial slip energy ratio

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A Crash Course in 1

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1999年

作者： Stephan Kaufmann

"A Crash Course in Mathematica" is a compact introduction to the program Mathematica, which is widely used in mathematics, as well as in the natural and engineering sciences.

ISBN: (数字)9783034875899

ISBN: (纸本)9783764361273

"A Crash Course in Mathematica" is a compact introduction to the program Mathematica, which is widely used in mathematics, as well as in the natural and engineering sciences.

关键词： Mathematics of Computing Mathematical Software

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The contribution of small leaks in a baghouse filter to dust emission in the PM2.s range-A system approach

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Particuology 2017年第1期15卷 40-52页

作者： Oliver Kurtz Jorg Meyer Gerhard Kasper Institut for Mechanische Verfahrenstechnik und mechanik Karlsruhe Institute of Technology 76131 Karlsruhe Germany Freudenberg Filtration Technologies 69465 WeinheimGermany.

The contribution of leakage in a baghouse filter （defined as a short circuit between the upstream and downstream sides of the filter） to the emission of fine particles is quantified in comparison to other dust emission sources, and the influence of key operating variables on overall system response is analyzed. The study was conducted on a well-maintained pilot-scale filter unit （9 bags of 500 g/m^2 calendered polyester needle felt; total surface area 4.2 m^2） operated in Ap-controlled mode over a range of pulsing intensities, with two types of test dust （one free-flowing and the other cohesive） at inlet concentrations of 10 and 30 g/m^3. Leaks included single holes between 0.5 and 4 mm diameter, intentionally placed in either the plenum plate or one of the filter bags, as well as seamlines from bag confectioning. Emissions were sep- arated by source into a transient contribution due to dust penetration through the filter bags after each cleaning pulse, and a continuous contribution from leaks. This separation was based on a novel method of data processing that relies on time-resolved concentration measurements with a specially calibrated optical particle counter. Tiny leaks on the order of 1 mm generated the same emission level as all the bags combined, and dominated continuous emissions. The equivalent leak cross section （leakage = media emission） was about 1 ppm of the total installed filter surface, independent of upstream dust concentra- tion. Leakage through open seamlines amounted to 75% of media emissions in case of free-flowing test dust. Leakage was restricted to aerodynamic diameters less than ~5 μm （roughly the PM2.s mass frac- tion）. For comparison, time-averaged mass penetration through conventional needle-felt media ranged from about 10^-5 to 10^-6, depending on cohesiveness of the particle material and pulse cleaning intensity, giving emission levels between about 0.02 and 0.2 mg/m^3 at the reference concentration of 10 R/m^2.

关键词： Air filtration Baghouse Pulse-cleaned filters Leaks PM2.5 Dust emission

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MULTIVARIABLE FINITE ELEMENTS:CONSISTENCY AND OPTIMIZATION

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Science China Mathematics 1991年第3期34卷 284-299页

作者：吴长春 HANS BUFLER Institute fur mechanik (Bauwesen) Universitat Stuttgart Pfaffenwaldring 7 7000 Stuttgart 80 West Germany Department of Modern MechanicsUniversity of Science and Technology of ChinaHefeiChina. Institute für mechanik (Bauwesen) Universitat Stuttgart Pfaffenwaldring 7 7000 Stuttgart 80 West Germany

A nonlinear analysis of the energy consistency of multivariable finite elements based onincompatible trial functions is presented. The nonlinear forms of the convergence and opti-mization condition are set up. The relevant optimization approach for hybrid elements andthe optimal parameter matching is suggested and applied to the 3-dimensional problem ofelasticity.

关键词： energy consistency condition element optimization condition optimizing pattern optimal parameter matching.

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A new hybrid piezoelectric ultrasonic motor with two stators

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Journal of Central South University of Technology 2005年第3期12卷 324-328页

作者：易幼平 Wolfgang Seemann Rainer Gausmann 钟掘 College of Mechanical and Electrical Engineering Central South University Changsha 410083China Institut für Technische mechanik Universitt KarlsruheKarlsruhe 76128Germany AG Maschinendynamik Universitt Kaiserslautern Kaiserslautern 67653 Germany

A new hybrid piezoelectric ultrasonic motor, which consists of one rotor and two stators, was proposed in this paper. In order to match the resonance frequencies of longitudinal vibration and torsional vibration excited in the stators, a symmetrical structure was adopted in design of the motor. A so-called mass matching method, namely adding two rings to the outside circumference of the two stators respectively, was used to adjust the resonance frequencies of these two vibrations. A finite element model was developed using ANSYS software for the purpose of analyzing the resonance frequencies of longitudinal vibration and torsional vibration as well as the function of the adjusting rings. The results show that the resonance frequency of torsional vibration varies with the position of the ring, but the resonance frequency of longitudinal vibration changes little. By means of adjusting the mass and the position of the rings, the first order resonance frequency of longitudinal vibration is coincided with that of torsional vibration and the value is 20.75kHz. An experimental prototype motor was fabricated according to the analytical results and its performance is in agreement with the theoretical predictions. The speed of motor reaches the maximum 92r/min at the working frequency 19.0kHz.

关键词：压电超声马达锆钛酸铅谐振频率振动

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Friction-Induced Instabilities in a Disk Brake Model

Friction-Induced Instabilities in a Disk Brake Model

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第十一届IFTOMM世界大会

作者： Jōrg Wauer Jürgen Heilig Institut für technische mechanik Universitāt Karlsruhe D-76128 KarlsruheGermany Institut für technische mechanik Universitāt Karlsruhe D-76128 KarlsruheGermany

＜正＞The dynamics of a structural car brake model is examined to explain brake noise by friction-induced instabilities including thermal effects. The rotating brake disk is modeled as a ring with two pads considered as rigid bodies which are in a one-point contact with the ring. Each pad is viscoelastically suspended in axial and circumferential direction and loaded with a constant brake load. At the two contact points, heat is fed into the thermoelastic ring which is proportional to the power of the two friction forces. After discretizing the governing boundary value problem by a modal expansion technique, a highly nonlinear system of ordinary differential equations is obtained. It forms the starting point of the stability analysis showing instabilities for high and for low driving speed responsible for brake noise. Several suggestions are made to obtain stable operation conditions without noise.

关键词： Brake Noise Structural Model Friction Heating Instabilities

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Robust Implementation of Kinematic and Boundary Conditions in Complex Free-Surface Flow Simulation

Robust Implementation of Kinematic and Boundary Conditions i...

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The Sixth World Congress on Computational Mechanics in Conjunction with the Second Asian-Pacific Congress on Computational MechanicsⅠ

作者： Marek Behr Lehrstuhl für Numerische mechanik TU München Boltzmannstr. 15 85747 Garching Germany

Free-surface flow simulations are an invaluable design and analysis tool in many areas of engineering, including civil engineering, marine and coating industries, and off-shore exploration. Two alternative computational approaches—interface-tracking and interface-capturing—are commonly considered. While the interface-capturing approach exhibits unmatched robustness for complex free-surface motion, i.e. merging and void formation, the interface-tracking approach is very attractive due to its better mass conservation properties at a comparable resolution. Therefore, expanding the reach of the interface-tracking methods is the primary issue discussed here.

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Numerical investigation of the influence of shear band localization on the resonant behavior in the VHCF regime

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Theoretical & Applied Mechanics Letters 2014年第5期4卷 24-29页

作者： Philipp-M.Hilgendorff Andrei Grigorescu Martina Zimmermann Claus-P.Fritzen Hans-J.Christ Institut f¨ur mechanik und Regelungstechnik-Mechatronik Universit¨at Siegen Institut f¨ur Werkstofftechnik Universit¨at Siegen Institut f¨ur Werkstoffwissenschaft Technische Universit¨at Dresden Institut f¨ur Werkstofftechnik Universit¨at Siegen

The monitored resonant behavior of fatigue specimens of metastable austenitic stainless steel （AISI304） is correlated with its damage accumulation in the very high cycle fatigue （VHCF） regime. The resonant behavior is stud- ied experimentally and shows a distinct transient characteristic. Microscopic ex- aminations indicate that during VHCF a localized plastic deformation in shear bands arises on the specimen surface. of damage accumulation in shear bands Hence, this work focuses on the effect on the resonant behavior of AISI304 in the VHCF regime. A microstructural simulation model is proposed that takes into account specific mechanisms in shear bands proven by experimental results. The simulation model is solved numerically using the two-dimensional bound- ary element method and the resonant behavior is characterized by evaluating the force-displacement hysteresis loop. Simulation of shear bands agrees well with microscopic examinations and plastic deformation in shear bands influences the transient characteristic of the resonant behavior.

关键词： shear bands resonant behavior very high cycle fatigue boundary elementmethod

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