Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 126-130.

Submitted by Eduardo Felipe de Campos null (eduardo81010@aluno.feis.unesp.br) on 2018-01-11T17:05:53Z No. of bitstreams: 1 DISSERTACAO.pdf: 18831766 bytes, checksum: c62a5bf82a73cc4a7517b74b6a078fb4 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-01-11T18:55:13Z (GMT) No. of bitstreams: 1 campos_ef_me_ilha.pdf: 18831766 bytes, checksum: c62a5bf82a73cc4a7517b74b6a078fb4 (MD5) / Made available in DSpace on 2018-01-11T18:55:13Z (GMT). No. of bitstreams: 1 campos_ef_me_ilha.pdf: 18831766 bytes, checksum: c62a5bf82a73cc4a7517b74b6a078fb4 (MD5) Previous issue date: 2017-08-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Estruturas de paredes finas são muito utilizadas na engenharia moderna devido sua boa relação entre peso e resistência. Sua aplicação vai desde obras civis, como cúpulas em edifícios e pontes, até estruturas aeronáuticas e equipamentos industriais. Uma geometria que é muito comum de ser encontrada nas estruturas de paredes finas são os cilindros, como pode ser observado no corpo dos aviões, tubulações e vasos de pressão. Submetidas a esforços compressivos, essas estruturas ficam suscetíveis ao fenômeno de instabilidade ou flambagem, podendo entrar em colapso repentinamente, mesmo antes de apresentar altas tensões. Assim, compreender o comportamento da instabilidade se torna crucial em um projeto de estruturas de paredes finas. Um dos fatores que influenciam no comportamento da instabilidade é a imperfeição geométrica da estrutura, e qualquer processo de fabricação possui erros associados ao processo. Para iniciar o estudo foi necessário medir os defeitos devido ao processo de fabricação do cilindro. Duas alternativas para realizar as medidas foram propostas, a primeira utilizando LVDTs, que medem a variação do raio do cilindro ao longo de toda sua extensão, e a segunda o fotoprocessamento. Ambos os métodos nos deram uma nuvem de pontos que foram processadas para obter a estrutura 3D CAD, possibilitando sua análise pelo método de elementos finitos e obtenção das respectivas cargas de flambagem numéricas. Além do método numérico foi realizado um ensaio experimental visando validar a análise numérica. O cilindro foi fechado com duas tampas e montado em uma bancada experimental, instrumentado com LVDTs, manômetro e por fim, uma bomba de vácuo foi ligada a uma das tampas. A bomba criou vácuo dentro do cilindro até o mesmo sofrer colapso. As cargas de flambagem numéricas foram superiores a encontrada experimentalmente em 14,48% a geometria foto, 11,72% da geometria LVDT e 39,98% a do cilindro referência. Os resultados mostram que as imperfeições geométricas são de grande relevância na resistência a instabilidade de uma estrutura, e também que grandes imperfeições geométricas tendem a ser o local onde ocorrem as ondas de flambagem. Em relação ao método de medição por fotoprocessamento os resultados mostram que é interessante estudar a técnica para aplicações na área de instabilidade. / Thin-walled structures are widely used in modern engineering because of their good weight-to-strength ratio. Its application ranges from civil works, such as domes in buildings and bridges, to aeronautical structures and industrial equipment. One geometry that is very common to be found in thin-walled structures is the cylinder, as can be seen in the body of airplanes, pipes and pressure vessels. Under compressive stresses, these structures are susceptible to the buckling phenomenon, which can suddenly collapse, even before presenting high stresses. Therefore, understanding the behavior of instability becomes crucial in designing thin-walled structures. One of the factors influencing the behavior of instability is the geometric imperfection of the structure, and any manufacturing process has errors associated with the process. To begin the study it was necessary to measure the defects due to the cylinder manufacturing process. Two alternatives to carry out the measurements were proposed, the first using LVDTs, which measure the variation of the cylinder radius along its length, and the second the photoprocessing. Both methods gave us a point cloud that were processed to obtain the 3D CAD structure, allowing its analysis by the finite element method and obtaining the respective numerical buckling loads. In addition to the numerical method, an experimental test was carried out to validate the numerical analysis. The cylinder was closed with two flat heads and mounted on an experimental bench, instrumented with LVDTs, manometer and finally, a vacuum pump was attached to one of the flat heads. The pump has created a vacuum inside the cylinder until it collapses. Numerical buckling loads were greater than that found experimentally at 14.48 % photo geometry, 11.72 % LVDT geometry and 39.98 % a reference cylinder. The results show that the geometric imperfections are of great relevance in the resistance to buckling of a structure, and also that great geometric imperfections tend to be the place where the buckling waves occur. Regarding the method of measurement by photoprocessing the results show that it is interesting to study the technique for applications in the area of instability. / CAPES: 1544963

Outre leur fonction principale de correction visuelle, les verres ophtalmiques offrent des valeurs ajoutées supplémentaires, tels que des propriétés anti-rayures et antireflets, afin d'optimiser le confort visuel des porteurs. Ces caractéristiques sont apportées par des revêtements déposés sur le substrat polymère constitutif du verre ophtalmique. Plus précisément, un vernis anti-rayures de quelques microns d'épaisseur est déposé par voie humide, suivi par l'évaporation d'un empilement antireflet à l'échelle nanométrique. Le défi consiste à assurer la qualité de l'interface entre ces couches. Compte-tenu de leur faible dimension, l'évaluation de l'adhérence au sein de l’empilement ophtalmique est principalement effectuée qualitativement à ce jour. L’objectif de ces travaux de recherche est de fournir une estimation quantitative de l'adhérence à l'interface la plus sensible de la structure, située entre la couche de SiO2 de l’antireflet et le vernis. Parmi les 300 essais d'adhérence décrits dans la littérature, l’essai d'adhérence par compression a été choisi car il permet de reproduire des défauts observés dans les conditions d’utilisation réelles du verre ophtalmique. Par ailleurs, cet essai d’adhérence offre l'avantage de permettre une application mécanique uniaxiale et sans contact dans la zone d'observation. L'adhérence entre la couche de SiO2 et le vernis a été estimée quantitativement en étudiant les morphologies de cloques générées expérimentalement. Afin d'étudier les dimensions des cloques rectilignes, le développement de l’essai d’adhérence par compression in situ sous profilomètre optique, a été réalisé. Une attention particulière a été portée aux conditions d’essai lors de la mise en compression de l’éprouvette. La conception de la platine de compression et des dimensions d'échantillons ont été revues pour favoriser l'homogénéité de la déformation du substrat. L'adhérence des échantillons issus de différents procédés d’évaporation a été déterminée. L'influence des paramètres du procédé ainsi que l'impact du vieillissement sur l'adhérence ont été évalués. Afin de mieux décrire le scénario expérimental et de mieux comprendre les mécanismes d'adhérence entre la couche mince de SiO2 et le vernis, un modèle numérique a été développé. Les propriétés mécaniques des matériaux constituant le système étudié ont été caractérisées par nanoindentation et couplées à des modèles de nanoindentation prenant en compte l'influence du substrat sur la couche mince de SiO2 de faible épaisseur. Le délaminage interfacial par flambement de la couche de SiO2 a été simulé en utilisant la technique des surfaces cohésives. Les paramètres interfaciaux permettant de reproduire les résultats expérimentaux sont présentés. Des analyses de sensibilité ont été réalisées pour évaluer les facteurs principaux permettant une description correcte du scénario de flambage. / Besides its main function of providing visual correction, ophthalmic lenses offer additional benefits, such as anti-scratch and anti-reflective properties, in order to optimize visual comfort. These features are brought by coatings deposited on top of the plastic polymeric substrate constituting the lens. More specifically, an anti-scratch hardcoat of a few microns thick is deposited by wet chemical methods, followed by the evaporation of an anti-reflective stack within the nanometric scale. The challenge is to ensure interface quality between layers. Considering their small dimensions, assessment of mechanical adhesion within the ophthalmic stack is mostly performed qualitatively to this day. The aim of this research is to provide a quantitative estimate of the mechanical adhesion at the most sensitive interface of the structure, located between the SiO2 layer of the anti-reflective stack and the hardcoat. Among the 300 adhesion tests described in the literature, adhesion test by compression has been chosen because of its ability to replicate defects observed in real life. Moreover compression tests offer the advantage of allowing uniaxial and contactless mechanical application within the observation area. Mechanical adhesion at this interface has been estimated quantitatively by studying buckle morphologies generated by compression tests. In order to study dimensions of straight-sided buckles, development of in situ compression test under an optical profilometer was carried out. Special attention was given to experimental conditions during application of compressive stress on test specimen. Both designs of samples and compression testing stage were revised to promote substrate’s strain homogeneity. Mechanical adhesion of samples which underwent different deposition processes was assessed. Influence of process parameters as well as impact of ageing on mechanical adhesion was evaluated. In order to better describe the experimental scenario and gain a greater understanding of mechanisms of adhesion between the SiO2 layer and the hardcoat, a numerical model was developed. Mechanical properties of materials composing the interface were characterized by nanoindentation and coupled with nanoindentation models taking into account influence of substrate for thin SiO2 layer. Interfacial delamination through buckling of the SiO2 layer was simulated using cohesive surface technique. Interfacial parameters allowing close compliance with experimental results are presented. Sensitivity analyses were performed to evaluate leading factors allowing proper description of buckling scenario.

Orientador: Amarildo Tabone Paschoalini / Resumo: Estruturas de paredes finas são muito utilizadas na engenharia moderna devido sua boa relação entre peso e resistência. Sua aplicação vai desde obras civis, como cúpulas em edifícios e pontes, até estruturas aeronáuticas e equipamentos industriais. Uma geometria que é muito comum de ser encontrada nas estruturas de paredes finas são os cilindros, como pode ser observado no corpo dos aviões, tubulações e vasos de pressão. Submetidas a esforços compressivos, essas estruturas ficam suscetíveis ao fenômeno de instabilidade ou flambagem, podendo entrar em colapso repentinamente, mesmo antes de apresentar altas tensões. Assim, compreender o comportamento da instabilidade se torna crucial em um projeto de estruturas de paredes finas. Um dos fatores que influenciam no comportamento da instabilidade é a imperfeição geométrica da estrutura, e qualquer processo de fabricação possui erros associados ao processo. Para iniciar o estudo foi necessário medir os defeitos devido ao processo de fabricação do cilindro. Duas alternativas para realizar as medidas foram propostas, a primeira utilizando LVDTs, que medem a variação do raio do cilindro ao longo de toda sua extensão, e a segunda o fotoprocessamento. Ambos os métodos nos deram uma nuvem de pontos que foram processadas para obter a estrutura 3D CAD, possibilitando sua análise pelo método de elementos finitos e obtenção das respectivas cargas de flambagem numéricas. Além do método numérico foi realizado um ensaio experimental visando vali... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Thin-walled structures are widely used in modern engineering because of their good weight-to-strength ratio. Its application ranges from civil works, such as domes in buildings and bridges, to aeronautical structures and industrial equipment. One geometry that is very common to be found in thin-walled structures is the cylinder, as can be seen in the body of airplanes, pipes and pressure vessels. Under compressive stresses, these structures are susceptible to the buckling phenomenon, which can suddenly collapse, even before presenting high stresses. Therefore, understanding the behavior of instability becomes crucial in designing thin-walled structures. One of the factors influencing the behavior of instability is the geometric imperfection of the structure, and any manufacturing process has errors associated with the process. To begin the study it was necessary to measure the defects due to the cylinder manufacturing process. Two alternatives to carry out the measurements were proposed, the first using LVDTs, which measure the variation of the cylinder radius along its length, and the second the photoprocessing. Both methods gave us a point cloud that were processed to obtain the 3D CAD structure, allowing its analysis by the finite element method and obtaining the respective numerical buckling loads. In addition to the numerical method, an experimental test was carried out to validate the numerical analysis. The cylinder was closed with two flat heads and mounted on an expe... (Complete abstract click electronic access below) / Mestre

abstract: Ordered buckling of stiff films on elastomeric substrates has many applications in the field of stretchable electronics. Mechanics plays a very important role in such systems. A full three dimensional finite element analysis studying the pattern of wrinkles formed on a stiff film bonded to a compliant substrate under the action of a compressive force has been widely studied. For thin films, this wrinkling pattern is usually sinusoidal, and for wide films the pattern depends on loading conditions. The present study establishes a relationship between the effect of the load applied at an angle to the stiff film. A systematic experimental and analytical study of these systems has been presented in the present study. The study is performed for two different loading conditions, one with the compressive force applied parallel to the film and the other with an angle included between the application of the force and the alignment of the stiff film. A geometric model closely resembling the experimental specimen studied is created and a three dimensional finite element analysis is carried out using ABAQUS (Version 6.7). The objective of the finite element simulations is to validate the results of the experimental study to be corresponding to the minimum total energy of the system. It also helps to establish a relation between the parameters of the buckling profile and the parameters (elastic and dimensional parameters) of the system. Two methods of non-linear analysis namely, the Newton-Raphson method and Arc-Length method are used. It is found that the Arc-Length method is the most cost effective in terms of total simulation time for large models (higher number of elements).The convergence of the results is affected by a variety of factors like the dimensional parameters of the substrate, mesh density of the model, length of the substrate and the film, the angle included. For narrow silicon films the buckling profile is observed to be sinusoidal and perpendicular to the direction of the silicon film. As the angle increases in wider stiff films the buckling profile is seen to transit from being perpendicular to the direction of the film to being perpendicular to the direction of the application of the pre-stress. This study improves and expands the application of the stiff film buckling to an angled loading condition. / Dissertation/Thesis / M.S. Mechanical Engineering 2010

Orientador: Amarildo Tabone Paschoalini / Resumo: Estruturas de parede fina são amplamente utilizadas na engenharia contemporânea devido à sua boa relação peso x resistência. Sua aplicação vai da construção civil, como cúpulas e pontes, até a aeronáutica e aeroespacial. Uma geometria de parede fina comum são os cilindros, observados em oleodutos, fuselagem e vasos de pressão. Para ser classificados como parede fina, a razão entre a espessura da parede e seu raio não deve ultrapassar 1:10. Eles ficam submetidos a esforços constantes e suscetíveis à instabilidade estrutural, em especial à flambagem, entrando em colapso repentinamente, muito abaixo da carga de projeto estipulada. Assim, compreender o comportamento desta instabilidade torna-se essencial para o avanço da engenharia. Para iniciar a compreensão da instabilidade, primeiro necessita-se conhecer as imperfeições geométricas da estrutura, ocasionadas, muitas vezes, pelo próprio processo de fabricação. A concepção destas imperfeições foi tratada por duas técnicas: CMM – Coordinates Mensuring Machine e CAI –Computer Aided Inspection. A primeira, tradicional, por contato, utilizando sensores LVDT – Linear Variable Differential Transformer, e, a segunda, vanguardista, sem contato, denominada "fotogrametria". Com isto, foi possível conceber uma estrutura tridimensional a ser analisada numericamente para obtenção das cargas críticas de flambagem, na qual estas duas técnicas apresentaram desvios condizentes com a literatura atual. Isto demonstrou, não somente, a acuracidade da... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Thin wall structures are widely used in contemporary engineering because of their good weight and strength ratio. Their application goes from civil construction such as domes and bridges, to aeronautics and aerospace. A common thin wall geometry are the cylinders, observed in oil pipelines, fuselage and pressure vessels. In order to be classified as thin wall, the ratio between the wall thickness and its radius must not exceed 1:10. They are subjected to constant efforts and susceptible to structural instability, especially buckling, suddenly collapsing, quite below the stipulated design load. Thus, understanding the behavior of this instability becomes essential for the advance of engineering. In order to begin the understanding of instability, it is firstly necessary to know the geometrical imperfections of the structure, often caused by the manufacturing process itself. The design of these imperfections was treated by two techniques, CMM – Coordinates Measuring Machine and CAI – Computer Aided Inspection. The first one, more conservative, by contact, using LVDT sensors, and, the second one, avant-garde, contactless, called “photogrammetry”. With this, it was possible to design a three-dimensional structure to be numerically analyzed to obtain the critical loads of buckling, in which these two techniques presented follow deviations from the current literature. This demonstrates not only the accuracy of the traditional contact technique to obtain geometry, but also how photo... (Complete abstract click electronic access below) / Mestre

Submitted by Bernardo Luis Pessutto (b_pessutto@hotmail.com) on 2018-08-22T02:28:26Z No. of bitstreams: 1 Trabalho Rev17.pdf: 4549693 bytes, checksum: 1dd1971769da127eccb0da40a664879e (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-08-22T17:32:16Z (GMT) No. of bitstreams: 1 pessutto_bl_me_ilha.pdf: 4549693 bytes, checksum: 1dd1971769da127eccb0da40a664879e (MD5) / Made available in DSpace on 2018-08-22T17:32:16Z (GMT). No. of bitstreams: 1 pessutto_bl_me_ilha.pdf: 4549693 bytes, checksum: 1dd1971769da127eccb0da40a664879e (MD5) Previous issue date: 2018-02-23 / Estruturas de parede fina são amplamente utilizadas na engenharia contemporânea devido à sua boa relação peso x resistência. Sua aplicação vai da construção civil, como cúpulas e pontes, até a aeronáutica e aeroespacial. Uma geometria de parede fina comum são os cilindros, observados em oleodutos, fuselagem e vasos de pressão. Para ser classificados como parede fina, a razão entre a espessura da parede e seu raio não deve ultrapassar 1:10. Eles ficam submetidos a esforços constantes e suscetíveis à instabilidade estrutural, em especial à flambagem, entrando em colapso repentinamente, muito abaixo da carga de projeto estipulada. Assim, compreender o comportamento desta instabilidade torna-se essencial para o avanço da engenharia. Para iniciar a compreensão da instabilidade, primeiro necessita-se conhecer as imperfeições geométricas da estrutura, ocasionadas, muitas vezes, pelo próprio processo de fabricação. A concepção destas imperfeições foi tratada por duas técnicas: CMM – Coordinates Mensuring Machine e CAI –Computer Aided Inspection. A primeira, tradicional, por contato, utilizando sensores LVDT – Linear Variable Differential Transformer, e, a segunda, vanguardista, sem contato, denominada "fotogrametria". Com isto, foi possível conceber uma estrutura tridimensional a ser analisada numericamente para obtenção das cargas críticas de flambagem, na qual estas duas técnicas apresentaram desvios condizentes com a literatura atual. Isto demonstrou, não somente, a acuracidade da técnica tradicional de contato para obtenção da geometria, mas, também, como a fotogrametria pode ser uma alternativa viável para inspeções rápidas de geometria. / Thin wall structures are widely used in contemporary engineering because of their good weight and strength ratio. Their application goes from civil construction such as domes and bridges, to aeronautics and aerospace. A common thin wall geometry are the cylinders, observed in oil pipelines, fuselage and pressure vessels. In order to be classified as thin wall, the ratio between the wall thickness and its radius must not exceed 1:10. They are subjected to constant efforts and susceptible to structural instability, especially buckling, suddenly collapsing, quite below the stipulated design load. Thus, understanding the behavior of this instability becomes essential for the advance of engineering. In order to begin the understanding of instability, it is firstly necessary to know the geometrical imperfections of the structure, often caused by the manufacturing process itself. The design of these imperfections was treated by two techniques, CMM – Coordinates Measuring Machine and CAI – Computer Aided Inspection. The first one, more conservative, by contact, using LVDT sensors, and, the second one, avant-garde, contactless, called “photogrammetry”. With this, it was possible to design a three-dimensional structure to be numerically analyzed to obtain the critical loads of buckling, in which these two techniques presented follow deviations from the current literature. This demonstrates not only the accuracy of the traditional contact technique to obtain geometry, but also how photogrammetry can be a viable alternative for rapid geometry inspections.

Despite the increasing availability of personal fabrication hardware and services, the true potential of digital fabrication remains unrealized due to lack of computational techniques that can support 3D shape design by nonexperts. This work develops computational methods that address two key aspects of content creation:(1) Function-driven design synthesis, (2) Design assessment. For design synthesis, a generative shape modeling algorithm that facilitates automatic geometry synthesis and user-driven modification for nonexperts is introduced. A critical observation that arises from this study is that the most geometrical specifications are dictated by functional requirements. To support design by high-level functional prescriptions, a physics based shape optimization method for compliant coupling behavior design has been developed. In line with this idea, producing complex 3D surfaces from flat 2D sheets by exploiting the concept of buckling beams has also been explored. Effective design assessment, the second key aspect, becomes critical for problems in which computational solutions do not exist. For these problems, this work proposes crowdsourcing as a way to empower non-experts in esoteric design domains that traditionally require expertise and specialized knowledge.

O crescente aumento do uso de madeira laminada colada (MLC) em peças estruturais exige dos meios acadêmicos a pesquisa e desenvolvimento de teorias e rotinas de cálculo, que proporcionem suporte teórico para projetos estruturais que empreguem tal material. Nesta pesquisa foi desenvolvido em laboratório de modelos estruturais, um programa para o cálculo estrutural de vigas de madeira laminada colada (MLC), por meio do método dos elementos finitos para material ortotrópico e material isotrópico. Foram rompidas, em uma prensa universal, vigas de Madeira Laminada Colada (MLC), em escala natural, com e sem emendas nas lâminas, com a finalidade de comparação dos resultados assim obtidos, com os obtidos em modelos de cálculo existentes para vigas maciças de material isotrópico, como o método de cálculo da NBR 7190/97 e o método de cálculo da Teoria da Elasticidade (Timoshenko). Tais resultados também foram comparados com os resultados obtidos pelo método dos Elementos Finitos para materiais isotrópicos e ortotrópicos, acima citados. Para comparação entre as propriedades da madeira maciça e da madeira laminada colada, foram retirados corpos de prova das partes intactas das vigas sacrificadas, para realização de ensaios de cisalhamento na linha de cola e nas lâminas coladas, bem como corpos de prova para ensaios de flexão nas lâminas maciças das vigas de MLC. Para obtenção da tensão de ruptura a compressão paralela às fibras e do módulo de elasticidade, foram rompidos corpos de prova de 5cm x 5 cm x 15 cm. A comparação e análise dos resultados obtidos pelos procedimentos acima, levou à conclusão de que a madeira laminada colada (MLC), quando fabricada com cola estrutural, comporta-se como madeira maciça. Também foi possível observar que os modelos de cálculo empregando elementos finitos, ortotrópicos ou isotrópicos, reproduzem o comportamento de uma viga de madeira laminada colada. O modelo de cálculo da NBR 7190/97, pode ser empregado, mas apresenta resultados conservadores, a favor da segurança. Assim como o modelo de cálculo da Teoria da Elasticidade não deve ser empregado sem adaptação à madeira, pois apresentou resultados muito discrepantes. Os módulos de elasticidade da madeira maciça obtidos por ensaios de flexão e a partir do ensaio de compressão paralela às fibra, não representa o módulo de elasticidade representativo de uma viga de MLC. Da mesma forma a existência ou não de emendas nas lâminas, não altera os resultados. / The increasing use of glued laminated timber in structural parts requires academic research and development of theories and calculation routines that provide theoretical support for structural designs employing such material. In this research was developed in the laboratory of structural models, a program for calculating structural glued laminated timber beams by the finite element method for orthotropic material and isotropic material. Were disrupted in a press universal beam of glued laminated wood in full scale with and without splices blades, for the purpose of comparison of the results thus obtained with those obtained in calculation models exist for solid beams material isotropic, as the method of calculating the NBR 7190/97 and the calculation method of the theory of elasticity (Timoshenko). These results were also compared with results obtained by the method of finite elements for isotropic and orthotropic materials, mentioned above. To compare the properties of solid wood and glued laminated timber, specimens were removed from intact parts of the broken beams for testing shear line glue and glued the layers, as well as specimens for bending tests blades massive beam. To obtain the tensile strength parallel to the compression of the fibers and elastic modulus were broken specimens with the dimensions 5 cm x 5 cm x 15 cm. The comparison and analysis of the results obtained by the above procedure led to the conclusion that the glued laminated wood when manufactured with structural adhesive, behaves as solid wood. It was also noted that the model calculations using finite elements, both isotropic and orthotropic represent the behavior of a beam of glued laminated wood. The calculation model of the NBR 7190/97, can be employed, but has conservative results, in favor of security. As the calculation model of the theory of elasticity should not be used without adjustment to the wood, because it showed very discrepant results. The modulus of elasticity of solid wood obtained by bending tests from test and compression parallel to the fiber, it is not the representative elastic modulus of a beam of glued laminated wood. Likewise, the presence or absence of amendments in the layers, does not change the results.

M.Ing. / Because cold-formed stainless steel is a new type of light steel material and dose not have a long history of utilisation in structures, there are many issues that need to be researched and discussed. Making a more thorough investigation and study of cold-formed stainless steels is essential. As a numerical analysis tool, the finite element method proves to be useful in structural analysis. The buckling modes of cold-formed stainless steel members, such as local, flexural, torsional and torsional-flexural buckling, are well known and well documented in design specifications. Distortional buckling is a special kind of buckling mode, which is less well known. Researchers have recently paid more attention to this problem. For stainless steel structures, it is necessary to investigate their behaviour when distortional buckling occurs. In this project, the distortional buckling of cold-formed stainless steel columns under axial compression is investigated. The finite element method is used to analyse and calculate different buckling modes, especially distortional buckling. This is compared to experimental results and other theoretical predictions. The ABAQUS finite element code is used throughout. Finite element modelling is very important prior to processing and analysis. ABAQUS models are created to study distortional buckling. The initial imperfection of structural members is taken into account with these models, using specific sine wave descriptions with respect to different structural parameters. A dynamic processing approach is chosen in the finite element analysis. The effectiveness and accuracy of these models have been verified by both experimental tests and theoretical calculations. Buckling mode and behaviour are predicted and analysed in terms of the finite element models and processes. Suggestions are made for buckling analysis and design based on the research results.