In the development of explosively formed projectiles (EFPs), researchers are faced with the problem of testing prospective metals at high strain rates. So far it has been assumed that, relative to the cooling time, the deformation time is practically instantaneous indicating that the test is adiabatc: none of the heat generated within the metal is lost to conduction. In this paper we construct a model that subtracts out the effects of kinetic energy and uses specific heat as a function of temperature. In this way we can focus on the energy change in the specimen that can be attributed to temperature and determine just how adiabatic the high strain rate test is. / vi, 74 leaves : ill. ; 28 cm.

The present study involves the analysis and design optimization of thin and thick laminated composite structures using symbolic computation. The fibre angle and wall thickness of balanced and unbalanced thin composite pressure vessels are optimized subject to a strength criterion in order to maximise internal pressure or minimise weight, and the effects of axial and torsional forces on the optimum design are investigated. Special purpose symbolic computation routines are developed in the C programming language for the transformation of coordinate axes, failure analysis and the calculation of design sensitivities. In the study of thin-walled laminated structures, the analytical expression for the thickness of a laminate under in-plane loading and its sensitivity with respect to the fibre orientation are determined in terms of the fibre orientation using symbolic computation. In the design optimization of thin composite pressure vessels, the computational efficiency of the optimization algorithm is improved via symbolic computation. A new higher-order theory which includes the effects of transverse shear and normal deformation is developed for the analysis of laminated composite plates and shells with transversely isotropic layers. The Mathematica symbolic computation package is employed for obtaining analytical and numerical results on the basis of the higher-order theory. It is observed that these numerical results are in excellent agreement with exact three-dimensional elasticity solutions. The computational efficiency of optimization algorithms is important and therefore special purpose symbolic computation routines are developed in the C programming language for the design optimization of thick laminated structures based on the higher-order theory. Three optimal design problems for thick laminated sandwich plates are considered, namely, the minimum weight, minimum deflection and minimum stress design. In the minimum weight problem, the core thickness and the fibre content of the surface layers are optimally determined by using equations of micromechanics to express the elastic constants. In the minimum deflection problem, the thicknesses of the surface layers are chosen as the design variables. In the minimum stress problem, the relative thicknesses of the layers are computed such that the maximum normal stress will be minimized. It is shown that this design analysis cannot be performed using a classical or shear-deformable theory for the thick panels under consideration due to the substantial effect of normal deformation on the design variables. / Thesis (Ph.D.)-University of Natal, Durban, 1994.

Aviation is known to have some of the most stringent structural health monitoring standards in the world. An example of this would be the fact that certain bolts in the aircraft assembly must be periodically removed and inspected for fatigue damage. This can be a very costly endeavour: a case in point being the Hercules C130 aircraft, which requires approximately 200 man hours of down-time for the inspection of the bolts that attach the wings to the fuselage. The substitution of TRIP (Transformation Induced Plasticity) steel bolts for the current HSLA steel (AISI 4340) from which the bolts are manufactured, allows the bolt to act in the capacity of load bearing member as well as damage detector. This unique feature is a consequence of the transformation characteristic exhibited by TRIP steels when they are strained: an irreversible change within their microstructure from paramagnetic austenite parent phase to permanent ferromagnetic state occurs in direct proportion to the peak strain. This property allows us to establish a relationship from which the service life of the component can be determined. A prototype of a smart aircraft bolt and washer system has been developed, where the bolt acts as damage detector and the washer effectively examines the health of the bolt by reading the changing magnetic susceptibility of the bolt. This study presents both material development and product development phases of the Smart Aircraft Bolt prototype. A prediction of transformation characteristic due to deformation is carried out using finite element analysis (mechanical model) and a constitutive model (strain induced martensitic transformation kinetics) to predict the best situation for the smart washer. In addition, experimental work is performed in the form of cyclic temperature testing (with and without external loading) and tension-tension fatigue testing. For both sets of experimental testing, two positions of washer placement are tested. A correlation between volume fraction of martensite present and remaining life, is therefore possible. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

The objective of this work is to study crack path deflection under proportional and non-proportional mixed-mode fatigue and predict crack branching direction based on linear elastic fracture mechanics (LEFM) driving forces. Under proportional in-phase mixed Mode I / Mode II loading conditions, crack growth direction has previously been observed in some materials to shift from tensile-dominated Mode I to shear-dominated Mode II or mixed-mode crack growth at higher proportions of initial Mode II loading, but non-proportional loads are not well-characterized. An LEFM approach is desired in order to implement the model in crack growth software such as the boundary element-based fracture analysis package FRANC3D. A novel specimen configuration has been designed and analyzed for generation of wide ranges of mixed-mode loading conditions in a single test. This specimen and a more conventional thin-walled tubular specimen have been used to test polycrystalline nickel-base superalloy Inconel 718 under proportional in-phase and 3 kinds of non-proportional fatigue loading. Stress intensity factors for the various configurations have been analyzed with FRANC3D. Modal transition from Mode I (tensile) to Mode II (shear) crack branching has been observed in several load cases. Qualitative microscopy of fracture surfaces was used to characterize the difference between crack branch modes. An LEFM approach based on an effective stress intensity factor range, which incorporates the maximum value and range of each appropriate stress intensity (Mode I or Mode II), has been used to successfully predict the crack deflection angles, and in some cases to quantify modal transition, within each load case considered. Variability between load cases and specimen configurations points to the limitations of LEFM in providing a general predictor of crack path behavior across all types of non-proportional mixed mode loading.

Thesis (Ph.D.)--Tufts University, 2004. / Adviser: Masoud Sanayei. Submitted to the Dept. of Civil Engineering. Includes bibliographical references (leaves 300-305). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: P.S. Nicholson. Includes bibliographical references (leaves 135-157).

Thesis (Ph.D.)--Northwestern University, 2002. / Includes bibliographical references (leaves 191-202).

Thesis (M.Sc. (Maxillofacial Prosthetics))--Mahidol University, 2008. / LICL has E-Thesis 0043 ; please contact computer services. LIRV has E-Thesis 0043 ; please contact circulation services.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 223-229). Also available on the Internet.

Thesis (M.Eng.(Metallurgical Engineering))--University of Pretoria, 1999. / Summaries in Afrikaans and English. Includes bibliographical references.