Publications
198 results found
Wadee MA, 2001, Modelling of localized folding in geomechanics using 4th order nonlinear parabolic equations, EPSRC Applied Nonlinear Mathematics Theme Day
Hunt GW, Wadee MA, Peletier MA, 2001, Friction models of kink-banding in compressed layered structures, Lisse, The Netherlands, 5th International Workshop on Bifurcation and Localisation Theory in Geomechanics, Publisher: Swets & Zeitlinger, Pages: 249-256
Wadee MA, 2001, Book review: 'Shear deformable beams and plates: relationships with classical solutions'
Hunt GW, Peletier MA, Wadee MA, 2000, The Maxwell stability criterion in pseudo-energy models of kink banding, J STRUCT GEOL, Vol: 22, Pages: 669-681, ISSN: 0191-8141
Kink banding, common to many structures in nature and engineering, has several distinctive features-notably highly nonlinear snap-back instability leading to localization and sequential lock-up. The proposed friction model, although simplified, introduces these defining characteristics without obscuring them by including other effects of lesser immediate significance. In the absence of small imperfections or disturbances, linearized theory suggests that in its pre-kinked configuration the system never goes unstable. However, under sufficient applied end-displacement it is in a state of extreme metastability, such that micro-disturbances would trigger a non-linear response. This is overcome when an energy approach based on a global rather than a local stability criterion is used. When applied to imperfect systems with small initial misalignments, the critical displacement thus defined shows little of the sensitivity expected from other stability criteria, and provides a lower bound on the expected critical displacement and associated load. (C) 2000 Elsevier Science Ltd. All rights reserved.
Wadee MA, 2000, Effects of periodic and localized imperfections on struts on nonlinear foundations and compression sandwich panels, INT J SOLIDS STRUCT, Vol: 37, Pages: 1191-1209, ISSN: 0020-7683
Heuristic studies of a strut on an elastic foundation and a strut with a sinusoidally varying load are extended to include initial geometric imperfections. Examination of Various shapes of imperfection leads to the conclusion that for the majority of cases the most severe form is localized to a section of the structure rather than periodically distributed along the length. This leads to an examination of the imperfection sensitivity of an axially-loaded sandwich panel, the geometry of which is determined from a simple optimization routine bringing together two distinct modes of buckling. It is found that such a structure exhibits highly unstable snap-back behaviour in the perfect case and that combined with localized imperfections, it would never attain its linear critical buckling load. (C) 1999 Elsevier Science Ltd. All rights reserved.
Hunt GW, Peletier MA, Champneys AR, et al., 2000, Cellular buckling in long structures, NONLINEAR DYNAM, Vol: 21, Pages: 3-29, ISSN: 0924-090X
A long structural system with an unstable (subcritical) post-buckling response that subsequently restabilizes typically deforms in a cellular manner, with localized buckles first forming and then locking up in sequence. As buckling continues over a growing number of cells, the response can be described by a set of lengthening homoclinic connections from the fundamental equilibrium state to itself. In the limit, this leads to a heteroclinic connection from the fundamental unbuckled state to a post-buckled state that is periodic. Under such progressive displacement the load tends to oscillate between two distinct values.The paper is both a review and a pointer to future research. The response is described via a typical system, a simple but ubiquitous model of a strut on a foundation which includes initially-destabilizing and finally-restabilizing nonlinear terms. A number of different structural forms, including the axially-compressed cylindrical shell, a typical sandwich structure, a model of geological folding and a simple link model are shown to display such behaviour. A mathematical variational argument is outlined for determining the global minimum postbuckling state under controlled end displacement (rigid loading). Finally, the paper stresses the practical significance of a Maxwell-load instability criterion for such systems. This criterion, defined under dead loading to be where the pre-buckled and post-buckled state have the same energy, is shown to have significance in the present setting under rigid loading also. Specifically, the Maxwell load is argued to be the limit of minimum energy localized solutions as end-shortening tends to infinity.
Wadee MA, Simoes da Silva LAP, Hunt GW, 2000, Localization in compression sandwich structures: A discussion of theoretical formulations and physical experimentation, London, CIMS 2000: 3rd International Conference on Coupled Instabilities in Metal Structures, Publisher: Imperial College Press, Pages: 27-34
Wadee MA, 1999, Experimental evaluation of interactive buckle localization in compression sandwich panels, J SANDW STRUCT MATER, Vol: 1, Pages: 230-254, ISSN: 1099-6362
Experimental observations on the axially-loaded sandwich panel compare well with the recent developments in the theoretical modelling of interactive localized buckling. Comparisons of experimental collapse loads, buckle wavelengths and equilibrium paths with the theoretical model show good correlation.
Wadee MA, Peletier MA, Hunt GW, 1999, Formation of kink bands in geological strata, Bath, UK, BAMC99: The 1999 British Applied Mathematics Colloquium, Publisher: University of Bath
Wadee MA, Peletier MA, Hunt GW, 1999, Formation of kink bands in geological strata, San Antonio, USA, GS99: 5th SIAM Conference on Mathematical and Computational Issues in the Geosciences, Publisher: SIAM, Pages: 82-83
Hunt GW, Wadee MA, 1999, Localization and mode interaction in sandwich structures, Localization and solitary waves in solid mechanics, Editors: Champneys, Hunt, Thompson, Singapore, Publisher: World Scientific, Pages: 301-320, ISBN: 9810239157
Bolchover P, Myers TG, Peletier MA, et al., 1999, Behaviour of bentonite clay in toxic waste barriers, 31st European Study Group with Industry
Wadee MA, Hunt GW, 1998, Interactively induced localized buckling in sandwich structures with core orthotropy, J APPL MECH-T ASME, Vol: 65, Pages: 523-528, ISSN: 0021-8936
Recent work on the interactive buckling behavior of compressed sandwich structures (Hunt and Wadee, 1998) is extended to orthotropic core materials. The variation of the material properties can tend to maximize the interactive effect such that overall and secondary localized modes are triggered almost simultaneously, giving rise to highly unstable post-buckling behavior in systems of practical dimensions.
Hunt GW, Wadee MA, 1998, Localization and mode interaction in sandwich structures, P ROY SOC LOND A MAT, Vol: 454, Pages: 1197-1216, ISSN: 1364-5021
Compressed sandwich structures, comprising two stiff face plates separated by a softer core materials, while designed principally as efficient integral structures, can lose this quality when faces buckle locally. Interaction between overall (Euler) buckling and local buckling of one face suggests that failure will localize into the centre. A variational formulation, leading to a pair of nonlinear differential equations subject to integral constraints; describes the post-buckling response. These are solved by a combination of numerical shooting and continuation techniques, such that the response far into the unstable post-buckling regime can be portrayed. Solutions with both linear and nonlinear constitutive core relations are compared with the results of an engineering (body-force) approach, and with those of earlier (periodic) Rayleigh-Ritz analyses. The latter demonstrate the extra destabilization that comes with localization.
Wadee MA, Hunt GW, 1998, Nonlinear interaction and localization in sandwich structures: A case of optimization promoting complex instability, Victoria, Australia, ACSO98: Australasian Conference on Structural Optimisation, Publisher: Oxbridge Press, Pages: 189-196
Wadee MA, Newman GM, 1995, The behaviour of steel columns in fire, Technical Report 524, Steel Construction Institute, 524
Wadee MA, 1995, Local instability phenomena in fire, Technical Report 533, Steel Construction Institute, 533
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.