The thesis investigates the mechanisms and restraints which influence transverse crack propagation through the bituminous surfacings of semi-flexible pavements. These pavements incorporate continuously laid cement bound roadbases which, during curing, crack into slabs of varying length, ranging from 4-25m. Reciprocal crack growth can occur in the surfacing, known as 'reflection cracks', located through stresses concentrated at the discontinuities within the roadbase . Three mechanisms have been identified and are described as contributing to reflection crack propagation. They have been analysed independently although the majority of conclusions drawn are applicable to their combined action. Their relative importance will vary with respect to pavement geometry, material properties, environmental conditions and traffic intensity. The first mechanism, 'tensile fatigue', induces crack propagation vertically upward through the surfacing. Tensile strains are developed during daily and ru1nual fluctuations of temperature, which cause expansion and contraction of the cement bound roadbase. This mechanism is most prominent on pavements with thin surfacings and long slab lengths. The rate of crack growth is dependent on the range of temperature within the roadbase , slab length, thermal characteristics of the roadbase material and resistance of the surfacing to this form of fatigue . A model has been developed based on a combination of results from an extensive testing programme, the use of fracture mechanics theory and computer simulation of the condition. The results quantify the resistance shown by conventional bituminous mixes to reflection cracking in terms of their mix parameters. Also considered are the use of stress relieving membranes, reinforcement material and modified binders to inhibit crack growth. The second mechanism, 'tensile yield' is also thermally induced but associated with cold weather conditions. Temperature gradients through the pavement structure induce warping and contraction within the uppermost layers. Tensile strains developed at the surface can, under U.K. winter temperatures, exceed the ultimate yield strain of the wearing course material. Preliminary. investigations of four pavements constructed in the early 1970's to motorway specifications indicate that reflection cracking will initiate at the surface if the yield strain, as defined through tensile creep tests, is reduced through binder oxidization to a value of 0.5%. This mechanism will operate on pavements with greater structural layer thicknesses and is only partially dependent on slab length. The influence of a further mechanism, 'shear fatigue' induced through trafficking of the pavement, has been shown to be confined to the acceleration of crack growth in the final stages of propagation unless a breakdown of interlock occurs between adjoining roadbase slabs.

No description available.

No description available.

Autoclave processing of large scale, one-piece structural parts made of carbon fiber-reinforced polymer composite materials is the key to decreasing manufacturing costs while at the same time increasing quality. Nonetheless, even in manufacturing simple flat parts, residual strains and stresses are unavoidable. For structural design purposes and to aid in the assembly procedures, it is desirable to have proven numerical tools that can be used to predict these residual geometrical and material properties in advance, thus avoid the costly experimental trial and error methods. A 2-D finite element-based code, COMPRO, has previously been developed in-house for predicting autoclave process-induced deformations and residual stresses in composite parts undergoing an entire cure cycle. To simulate the tool-part interaction, an important source of residual deformations/stresses, COMPRO used a non-zero thickness elastic shear layer as its only interface option. Moreover, the code did not account for the large deformations and strains and the resulting nonlinear effects that can arise during the early stages of the cure cycle when the material is rather compliant. In the present work, a contact surface employing a penalty method formulation is introduced at the tool-part interface. Its material-dependent parameters are a function of temperature, degree of cure, pressure and so forth. This makes the stick-slip condition plus separation between the part and the tool possible. The large displacements/rotations and large shear strains that develop at the early stages of the cure cycle when the resin has a very low elastic modulus provided the impetus to include a large strain/deformation option in COMPRO. A new “co-rotational stress formulation” was developed and found to provide a robust method for numerical treatment of very large deformation/strain problems involving anisotropic materials of interest here. Several verification and validation examples are used to calibrate the contact interface parameters and to demonstrate the correctness of implementation and the accuracy of the proposed method. A number of comparisons are made with exact solutions, other methods, other experiments and the same models in other commercial codes. Finally, several interesting cases are examined to explore the results of COMPRO predictions with the added options.

'Home' in a country with a notorious history of division becomes both a material and symbolic handle for belonging. The thesis looks at the nature of home making and home building as it is subjected to conflicts of tradition and domestic design organisation. The material objects together with the physical as well as the psychological spaces of home in South Africa exemplify the struggle with the ironies of a nascent modern era. / The thesis addresses the combination of home and modernity in a place and at a time when the one seemed to cancel the other. The role of authorities and missionaries in determining what home was to particularly categorised people and also what modernity should represent contributes to the subtle formulations of meaning in the narrative of this thesis. South African design and material culture precedes a discussion of land as home and visual culture's expression of this. This expression is seen in the monumentalising of struggles for a home country and more specifically a homeland. Some of these visual expressions are in the form of architecture and some as sculpture, painting or drawing. The visual art of the time informs and comments upon the notion of home as a place of belonging, longing or a place that is lost. A subtle reading of this ostensibly modern art is that it is strangely disengaged from its subject matter. Notions of white supremacy in line with a romantic nationalism based on theocratic beliefs in the 'promised land' are addressed in relation to these and other visual documents of the time. / Domestic design advice and advertising for the home provides insight into the home as an ideal as well as the home as an example of ostensible modernity. Issues such as fashion, taste, relevant theories of consumption together with the constant denial of African consumption form the background to the chapter's arguments on white South African middle class consumer reticence. The printed face of South Africa's supposed domestic modernity in the advertisements and decorating columns is balanced by a discussion of deeper psychological and emotional interiorities, these are evidenced in biographies, letters, oral family histories and historical novels. The possible meaning of home is also viewed through the lens of historical documentation, which shows the role of authorities and missionaries as partial players in the construction of modern domesticities. The notion of domesticity and its association with western progress or civilisation is shown to be filled with anxieties relating to hygiene and order. / Thesis (PhDArchitectureandDesign)--University of South Australia, 2005.

Zugl.: Stuttgart, Univ., Diss., 2007

Thesis (Ph.D.) in History--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 167-173).

Bamberg, Univ., Diss., 2002

Zugl.: Diss.

Hamburg, Techn. University, Diss., 2008.