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The present study addresses an optimization strategy for maximizing the structural ductility of Fiber Reinforced Concrete (FRC) with long textile fibers. Due to material brittleness of both concrete and fiber in addition to complex interfacial behavior between above constituents the structural response of FRC is highly nonlinear. Consideration of this material nonlinearity including interface is mandatory to deal with this kind of composite. In the present contribution three kinds of optimization strategies based on a damage formulation are described. The performance of the proposed method is demonstrated by a series of numerical examples; it is verified that the ductility can be substantially improved.

A set of techniques is developed that allows the incorporation of flight dynamics metrics as an additional discipline in a high-fidelity aerodynamic optimization. Specifically, techniques for including static stability constraints and handling qualities constraints in a high-fidelity aerodynamic optimization are demonstrated. These constraints are developed from stability derivative information calculated using high-fidelity computational fluid dynamics (CFD). Two techniques are explored for computing the stability derivatives from CFD. One technique uses an automatic differentiation adjoint technique (ADjoint) to efficiently and accurately compute a full set of static and dynamic stability derivatives from a single steady solution. The other technique uses a linear regression method to compute the stability derivatives from a quasi-unsteady time-spectral CFD solution, allowing for the computation of static, dynamic and transient stability derivatives. Based on the characteristics of the two methods, the time-spectral technique is selected for further development, incorporated into an optimization framework, and used to conduct stability-constrained aerodynamic optimization. This stability-constrained optimization framework is then used to conduct an optimization study of a flying wing configuration. This study shows that stability constraints have a significant impact on the optimal design of flying wings and that, while static stability constraints can often be satisfied by modifying the airfoil profiles of the wing, dynamic stability constraints can require a significant change in the planform of the aircraft in order for the constraints to be satisfied.

An accelerated high cycle fatigue testing approach is presented to determine the fatigue endurance limit of materials at high frequencies. Base excitation of a tapered plaque driven into a high frequency resonance mode allows the test to be completed in a significantly shorter time. This high cycle fatigue testing is performed using the tracked sine resonance search and dwell strategy. The controller monitors the structural health during the test. Any change in the dynamic response indicates crack initiation in the material. In addition, a shape optimization finite element model is conducted for the design of the tapered plaques. An integrated neural (Neural-Network) genetic (NSGA_II) optimization technique is implemented to carry out the shape optimization for this component. This process results in a significant reduction in the computational cost. A Pareto set is then produced that meets the designer’s requirements and provides the decision maker several alternatives to choose from.

An accelerated high cycle fatigue testing approach is presented to determine the fatigue endurance limit of materials at high frequencies. Base excitation of a tapered plaque driven into a high frequency resonance mode allows the test to be completed in a significantly shorter time. This high cycle fatigue testing is performed using the tracked sine resonance search and dwell strategy. The controller monitors the structural health during the test. Any change in the dynamic response indicates crack initiation in the material. In addition, a shape optimization finite element model is conducted for the design of the tapered plaques. An integrated neural (Neural-Network) genetic (NSGA_II) optimization technique is implemented to carry out the shape optimization for this component. This process results in a significant reduction in the computational cost. A Pareto set is then produced that meets the designer’s requirements and provides the decision maker several alternatives to choose from.

Short annular diffusers were essential components for turbomachines that have been used to expand the air entering the compressor, as interstage ducts between gas generators and power turbines, and on the exhaust gases exiting the turbine. The industrial community was interested and invested in improving diffuser design that was challenging owing to the unfavourable fluid flow effects. Efficient design of fluid flow devices was possible through the complementary use of experimental testing and computational fluid dynamics (CFD). A numerical shape optimization study was undertaken to determine preferential annular diffuser configurations. Experimental data were compared against CFD that simulated the steady-state Reynolds-averaged Navier-Stokes equations with two-equation turbulence models. This investigation reached equivalent conclusions with respect to the influences associated with diffuser geometry and swirl. Vorticity effects caused by square tabs, that were not as well understood, were investigated. The tabs were effective in reducing the central toroidal recirculation zone created by a swirling flow, but at a static pressure penalty for the area ratio, AR<2.73, diffusers tested. Results identified several shortcomings in the CFD that typically over-estimated pressure recovery and outlet velocity uniformity; however, properly qualitatively predicted wall pressure distributions and outlet velocity profiles. The use of CFD on modest grids, with preference given to the realizable k-epsilon turbulence model, for annular diffusers that have length to inlet height ratio of 12 and at least AR=2.73 with up to 20-degrees inlet swirl was encouraged as a design tool. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2014-05-29 09:03:16.591

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This paper was presented in WCSMO-9, Shizuoka.

This paper was presented at CJK-OSM 7, 18–21 June 2012, Huangshan, China.