This dissertation is concerned with experimental and analytical studies of the mechanics of interaction where a pneumatic tire is loaded vertically on a supporting ground, i.e., rigid base, clay and sand. / The numerous experiments were conducted under various conditions to characterized the interactions in terms of the experimental results, e.g. axle displacement, contact area, contact pressure, etc. The results of pressure distribution indicate that recognizing a tire as a pneumatic body is crucial in establishing a rational theory for tire-supporting ground interaction problems. The pressure distribution and contact area obtained in the experiments are also utilized in validating an analytical approach (i.e. First Analytical Approach) established in the dissertation. / A hypothetical description of the progress of tire deformation is discussed based on the experimental results. The discussion helps in providing a better understanding of the mechanics of the interaction, and for selecting basic analytical and/or numerical tools in establishing the present analytical methods. / In the analytical work, the two distinct analytical approaches (i.e. First and Second Analytical Approaches) are established under the plane strain condition in predicting contact length and pressure. However, the first analytical approach is emphasized in this dissertation, while the second one is rather a complementary work. / In the first analytical approach, the real contact profile is taken into account, while the existing contact theories (by Hertz, Muskhelishvili, etc.) essentially ignore the real kinematics of contact surfaces on which the pattern of pressure distribution greatly depends. In this first analytical approach, the following steps are taken: (1) transform a tire-supporting ground interaction problem into an equivalent free boundary (-value) problem of the deformed supporting ground; this is done so that the complex factors inherent to pneumatic tires are not directly taken into the analytical formulation; (2) determine the modulus of elasticity of the deformed supporting ground by taking into account the contact profile; (3) find the contact length and pressure by means of the complex variable method. / The contact length and pressure analytically obtained are in close agreement with those obtained through experimentation. An attempt has also been made to solve the sliding interaction problems. / The second analytical approach, which is an iterative technique combining the incremental finite element method and the complex variable method, is established fundamentally to solve an interaction problem between an elastic solid and a nonlinear elastic half-plane. Two different types of interaction problems are solved, i.e. tire-clay and rigid wheel-snowpack interactions. Numerical results on contact length for both problems showed acceptable agreement with the experimental results, while those on sinkage obtained for the rigid wheel did not.

This study considers a number of problems which remain in nonlinear consolidation modelling and prediction, despite the considerable research effort which has already been devoted to the subject. Nonlinear consolidation models refer to those models capable of accounting for material nonlinearity either explicitly, in the formulation of the governing equation, or implicitly in the numerical-solution technique. A nonlinear model can be characterised by its generality, appropriateness for modelling consolidation and prediction-capability. These three characteristics are not consistent; a model's superiority with respect to one characteristic does not imply its overall superiority. This inconsistency between the characteristics is resolved by a proposed model. This model is seen as an improvement over two available and widely used models; the Gibson et al. (1967) and Yong et al. (1983) models. / Nonlinear multiple-layer analysis requires the satisfaction of continuity conditions at the inter-layer boundaries. Existing continuity procedures seek to reduce the problem to a tractable single-layer problem, ignore the interaction between layers and are unsuitable for use with nonlinear models. Procedures, based on the trial-function technique, are proposed which satisfy the continuity conditions and facilitate these analyses. Various procedures are necessary to define the initial consolidation status of a soil depending on whether the field data is complete or incomplete. Procedures which can acknowledge incomplete data by calling for bounded analyses and yet can take full advantage of available data are proposed. / A finite-difference numerical-solution algorithm is developed for use with the proposed non-linear model. This algorithm is efficient, versatile and more suitable for multiple-layer analysis than the Yong et al. (1983) algorithm, on which it is based. / The findings of this study are successfully field validated on the basis of three case histories; the consolidation of highly compressible organic soils underlying two embankments in Poland and subsidence due to groundwater withdrawal in Bangkok, Thailand.

The present thesis studies the stability of a rotating cylindrical shell containing a co-rotating axial viscous flow. The system can be thought of as a long thin-walled pipe carrying an internal axial flow while the whole is in a frame of reference rotating at a prescribed rate. The equations of the previously solved inviscid model are rederived and the problem is studied further. The results obtained for purely axial flow are reproduced, but as expected from literature, it is impossible to obtain satisfactory results for the system subjected to rotation due to the presence of singularities in the flow pressure solution. A hypothetical physical explanation for these singularities is put forward and has similarities with the phenomenon of atmospheric flow blocking. / Considering the unsuccessful results obtained with the inviscid theory, it is believed that the added realism brought in by the introduction of viscosity in the theory can lead to a successful model. Assuming a travelling-wave perturbation scheme, the linear Donnell-Mushtari thin shell equations are coupled with the fluid stresses obtained by solving numerically the incompressible Navier-Stokes equation for a laminar or turbulent flow. A novel triple-perturbation approach is established to consider the interaction between the fluid and the structure. This triple-perturbation approach is in essence a superposition of three fluid fields caused by the three components of the shell deformation for a given oscillation mode. It is found that the usual technique for linear aeroelasticity studies consisting of applying the fluid boundary conditions at the undeformed position of the wall instead of the instantaneous deformed position greatly alters the stability of the system. To remedy to this problem, three different corrections are applied and tested on the carefully derived model. The dynamics of the system subjected to purely axial flow with no rotation is successfully studied with the viscous model for both laminar and turbulent flow conditions. Because no experimental or previous theoretical data is available, it is impossible to validate the results obtained in the laminar regime. For the turbulent regime, as the Reynolds number is increased, the results tend more and more towards those obtained with the inviscid theory. / The results obtained for small rates of rotation show that both in the laminar and in the turbulent regime, the system tends to be stabilised when subjected to a small rate of rotation. On the other hand, this tendency should be reversed for higher rates of rotation, but it is impossible to show this due to the limitations of the root-finding method employed.

No description available.

There is a class of plate buckling problems in which buckling occurs in the presence of a constraining medium. This type of buckling has been investigated by many researchers, mainly as buckling of elastic columns and plates on elastic foundations. Analytical solutions have been obtained by assuming the foundation to provide tensile as well as compressive reaction forces. The present work differs from the previous ones in two respects. One, the foundation is assumed to be one-sided, thus providing only the compressive resistance. Two, the plates are allowed to be stressed in the plastic, strain-hardening range. Equations for determining the buckling stresses and wavelengths are obtained by solving the differential equations for simply supported and clamped long rectangular plates stressed uniformly in the longitudinal direction. The relevance and the usefulness of the obtained formulas is demonstrated by comparing the predicted results with the experimental results of other researchers on buckling of concrete filled steel box-section and HSS columns. It is shown that the theoretical buckling loads match quite closely with the experimental ones, and hence, should prove useful in formulating rules for the design of such columns.

This thesis is concerned with the experimental evaluation of the volumetric deformation of a two-phase medium at the microscopic level. The basic definitions of the significant parameters involved in the mechanical response behaviour of the structured medium are based on the concepts of Probabilistic Micromechanics. A simple phenomenological model and the leading structural parameter $ theta sb{s}$ (Solid phase volume fraction) are discussed briefly. The experimental work makes use of a series of macroscopic tests to attain different states of deformation so that the evolution of the internal microstructural changes can be analyzed. The combined use of ultramicrotomy techniques and the Scanning Electron Microscopy operating in the Backscattered Electron mode allowed the quantification of the microstructural changes at large magnifications. The concepts of practical Stereology were adopted for the quantification of a large number of observation areas representative of the complete phenomenon to determine the leading structural parameter $ theta sb{s}.$ A semi-automatic system was developed for the determination of $ theta sb{s}$ corresponding to each observation area. A fully-automatic image analyzer also was used for the evaluation of the first state of deformation. The experimental procedure employed in this investigation is described in detail and its application is illustrated by the evaluation of $ theta sb{s}$ and its evolution at the microscopic level. The evaluations of the distributions of this parameter also are shown. In the conclusion of this thesis, the obtained results for the Al-Quetol are discussed and general remarks concerning the experimental technique and its application to other structured media are indicated.

No description available.

This thesis presents two problems in the field of fluid mechanics. Both problems concern the flow of a Newtonian viscous fluid in the laminar and early-transitional regimes. Geometrically, they also share the following features: a square corner; a wall boundary layer; and a semi-infinite physical domain. Part 1 of this thesis, comprising Chapters 2–5, considers the laminar flow parallel to a streamwise corner. In Chapter 2 we present an in-depth study of the laminar flow internal to a square corner. The hydrodynamic stability of this flow is the subject of Chapter 3. For the special case of zero pressure gradient, our analysis suggests a critical Reynolds number of Re[subscript]c ≈ 44 000 (based on streamwise distance from the leading edge), indicating that this flow is significantly less stable than the well-known Blasius boundary layer on a semi-infinite flat plate. In Chapter 4 we derive the laminar flow external to a square corner. Finally, in Chapter 5 we summarize our findings and offer some recommendations for future research on laminar and transitional corner flows. Part 2, comprising Chapters 6–10, considers the sudden blockage of steady laminar flow within a circular pipe. Even though the blockage occurs almost instantaneously, the fluid takes an appreciable time to come to rest. Accordingly, Chapter 6 presents a detailed analysis of the laminar-decay process at an arbitrary location upstream of the blockage point. The hydrodynamic stability of this unsteady upstream flow is the subject of Chapters 7 and 8. Chapter 7 uses traditional linear eigenmode theory, originally developed for steady laminar flow, to estimate that the laminar flow is absolutely stable in the event that the pre-blockage Reynolds number does not exceed Re[subscript]c ≈ 450. The linear pseudomode analysis of Chapter 8 yields the substantially lower estimate Re[subscript]c ≈ 115, above which there exists the theoretical possibility of transient growth initiating a ‘bypass’ transition to turbulence. However, after accounting for the transient nature of the underlying flow itself, we hypothesize a significantly higher threshold Re[subscript]c ≈ 1000 for full breakdown of the laminar structure. Chapter 9 rounds off the present work by extending the laminar-flow analysis of Chapter 6 to the immediate vicinity of the blockage point. We present a direct numerical simulation of the complete laminar-decay process within this end-region, highlighting the early-phase development of an unsteady corner boundary layer and the subsequent development of vortices in the interior of the pipe. The thesis concludes in Chapter 10 by summarizing the findings from Part 2 and suggesting some fruitful directions for future research on unsteady pipe flows. / Thesis (Ph.D.) -- University of Adelaide, School of Mathematical Sciences, 2009

Thesis (Ph. D.)--University of Washington. / Vita. Bibliography: L. 150-156.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1058. Advisers: Jonathan B. Freund; Robert D. Moser. Includes bibliographical references (leaves 110-114) Available on microfilm from Pro Quest Information and Learning.