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Acoustic stop bands in almost-periodic and weakly randomized stratified media:perturbation analysis

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Acta Mechanica Sinica 2008年第5期24卷 549-556页

作者： S.Guenneau a.b.movchan N.V.movchan J.Trebicki Department of Mathematical Sciences University of LiverpoolPeach StreetLiverpool L69 3BXUK Polish Academy of Sciences Institute of Fundamental Technology ResearchSwietokrzyska 21Warsaw 00049Poland

In this paper, we analyze the effect of both deter- ministic and random perturbations of a regular multi-layered elastic structure on its stop band properties. The tool of choice is the transfer matrix method, which is both versatile and easy to implement. In both cases, we find that the stop-bands widen. We observe the appearance of very narrow pass-bands within the stop-bands, which can be observed in other instances in optics.

关键词： Transmission problem Small random perturbations Stop bands

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Acta Mechanica Sinica 2010年第4期26卷 567-572页

作者： D.J.Colquitt a.b.movchan I.S.Jones W.Daniels Department of Mathematical Sciences University of Liverpool School of Engineering John Moores University Serco Assurance Walton House 404 The QuadrantBirchwood ParkRisleyWarringtonCheshireWA3 6GAUK

The paper presents a computational model for elastic waves in a structured weld adjacent to the free surface of an elastic solid. The main emphasis is on the interaction of waves with the micro-structure of the weld. Effects of localisation and channeling of waves are addressed. A model of a grain structure within the weld is also considered.

关键词： Macro-structured welds Waves in stratified media Dispersion Localisation

Asymptotic and numerical study of a surface breaking crack subject to a transient thermal loading

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Acta Mechanica Sinica 2006年第1期22卷 22-27页

作者： A.b. movchan I.S. Jones ljmu.ac.uk Department of Mathematical SciencesUniversity of Liverpoo UK L69 3bX School of EngineeringJames Parsons buildingJohn Moores Universitybyrom St.Liverpool UK. L3 3AF E-mail: i.s.jones

An asymptotic algorithm is applied to the problem of a finite, thermo-elastic solid containing a surface breaking crack, when the exterior surface is subjected to oscillatory thermal loading. This algorithm involves the study of a model problem. An analytical and numerical study of this model problem of a thermo-elastic half space containing a surface breaking crack and subjected to oscillatory thermal loading is presented. The crack surface is traction free. In particular, the amplitude of the stress intensity factor at the crack vertex is found as a function of the crack depth and the frequency of thermal oscillation.

关键词： Thermo-elasticity Surface breaking crack Wiener-Hopf solution Weight function method

Analysis of lattices with non-linear interphases

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Acta Mechanica Sinica 2006年第4期22卷 323-330页

作者： S. Haq A. b. movchan G. J. Rodin Faculty of Engineering Sciences GIK Institute Topi 23640 NWFP Pakistan Department of Mathematical Sciences University of Liverpool Liverpool L69 3BX UK Institute for Computational Engineering and Sciences The University of Texas at Austin Austin TX 78712 USA

Anti-plane deformation of square lattices containing interphases is analyzed. It is assumed that lattices are linear elastic but not necessarily isotropic, whereas interphases exhibit non-linear elastic behavior. It is demonstrated that such problems can be treated effectively using Green＇s functions, which allow to eliminate the degrees of freedom outside of the interphase. Illustrative numerical examples focus on the determination of applied stresses leading to lattice instability.

关键词： Interphases in lattices Stability Green's functions Evolution algroithm

Singular perturbation analysis of dynamic fields in a thermoelastic solid with a small surface-breaking crack

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Acta Mechanica Sinica 2006年第5期22卷 449-454页

作者： E. Zhelezina liv.ac.uk A. b. movchan I. S. Jones ljmu.ac.uk Department of Mathematical Sciences University of Liverpool Liverpool L69 3BX UK e-mail: ezzh School of Engineering John Moores University Liverpool L3 3AF UK e-mail: i.s.jones

An asymptotic analysis is presented for a dynamic problem of a semi-infinite isotropic thermoelastic solid with a small surface breaking crack. The exterior surface of the solid is subjected to a series of short thermal pulses. The crack surface is traction free and an ideal thermal contact is assumed across the crack. The stress intensity factor is asymptotically evaluated as a function of the crack depth and time. The effect of a boundary layer associated with the diffusive term is identified. The theoretical model is supplied with numerical simulations.

关键词： Thermoelasticity Surface breakingcrack Weight function method Stress intensity factor Thermal shock