On a contact problem for a viscoelastic von Kármán plate and its semidiscretization

summary:We deal with the system describing moderately large deflections of thin viscoelastic plates with an inner obstacle. In the case of a long memory the system consists of an integro-differential 4th order variational inequality for the deflection and an equation with a biharmonic left-hand side and an integro-differential right-hand side for the Airy stress function. The existence of a solution in a special case of the Dirichlet-Prony series is verified by transforming the problem into a sequence of stationary variational inequalities of von Kármán type. We derive conditions for applying the Banach fixed point theorem enabling us to solve the biharmonic variational inequalities for each time step

Modelización del flujo de un fluido viscoso en un tubo curvilíneo con paredes viscoelásticas

El objetivo de esta tesis doctoral es modelizar el problema de un fluido viscoso incompresible en una tubería curva con paredes viscoelásticas utilizando el método de los desarrollos asintóticos. Por un lado, se deduce un modelo unidimensional para el flujo viscoso incompresible justificado con estimaciones del error. Por otro lado, se deducen las ecuaciones bidimensionales para una lámina viscoelástica a partir del correspondiente tridimensional y presentamos resultados de convergencia fuerte que justifican los modelos. Finalmente, combinando los resultados obtenidos en la memoria, se presentan las ecuaciones del modelo acoplado para el problema motivador y se muestran ejemplos numéricos considerando una ley de pared algebraica elástica

Exact strip analysis and experiments on buckling and post-buckling of plates and stiffened panels with mode jumping

Engineering components consisting of plated structures subjected to in plane loading can potentially fail due to buckling. This work focuses on presenting novel approaches to enhance the buckling and post-buckling behaviour of flat plates and stiffened panels made with metal and composite materials under in-plane loading conditions. A better understanding of post-buckling behaviour, including the phenomenon of mode jumping, will lead to improvements in both design criteria and manufacturing processes. The first part of this thesis describes an extensive study using the exact finite strip computer program VICONOPT and the finite element method to investigate the buckling of simply supported composite plates under different in plane loads. This approach utilises the lamination parameters to enhance the buckling capacity through the anisotropic properties of the laminate. Numerical relationships are presented as an optimisation procedure to maximise the buckling load under in plane uniaxial compression, shear or a combination of both. The procedure is applied to a series of anisotropic symmetric and balanced laminates with varying thickness and aspect ratios. The second part presents a numerical and experimental study to explore the post-buckling phenomenon of mode jumping phenomenon in plates and stiffened panels. The VICONOPT post-buckling analysis is extended to predict mode jumping, and the resulting numerical investigations are validated by finite element analysis. Furthermore, a series of experimental tests have been devised to investigate the buckling, post-buckling and mode jumping behaviour of curved stiffened panels with different radii of curvature. The experimental results are compared with finite element results in order to examine the similarities and differences between simulations and real behaviour of panels under compressive load

A systematic approach for integrated product, materials, and design-process design

Designers are challenged to manage customer, technology, and socio-economic uncertainty causing dynamic, unquenchable demands on limited resources. In this context, increased concept flexibility, referring to a designer s ability to generate concepts, is crucial. Concept flexibility can be significantly increased through the integrated design of product and material concepts. Hence, the challenge is to leverage knowledge of material structure-property relations that significantly affect system concepts for function-based, systematic design of product and materials concepts in an integrated fashion. However, having selected an integrated product and material system concept, managing complexity in embodiment design-processes is important. Facing a complex network of decisions and evolving analysis models a designer needs the flexibility to systematically generate and evaluate embodiment design-process alternatives. In order to address these challenges and respond to the primary research question of how to increase a designer s concept and design-process flexibility to enhance product creation in the conceptual and early embodiment design phases, the primary hypothesis in this dissertation is embodied as a systematic approach for integrated product, materials and design-process design. The systematic approach consists of two components i) a function-based, systematic approach to the integrated design of product and material concepts from a systems perspective, and ii) a systematic strategy to design-process generation and selection based on a decision-centric perspective and a value-of-information-based Process Performance Indicator. The systematic approach is validated using the validation-square approach that consists of theoretical and empirical validation. Empirical validation of the framework is carried out using various examples including: i) design of a reactive material containment system, and ii) design of an optoelectronic communication system.Ph.D.Committee Chair: Allen, Janet K.; Committee Member: Aidun, Cyrus K.; Committee Member: Klein, Benjamin; Committee Member: McDowell, David L.; Committee Member: Mistree, Farrokh; Committee Member: Yoder, Douglas P