A brief review of fatigue design criteria on offshore wind turbine support structures

In this paper, a brief review of the main fatigue design criteria and some advanced fatigue approaches applied to offshore structures (e.g. offshore wind turbines) are presented. It is extremely important to understand the fatigue phenomenon and how it affects structures since offshore structures are constantly submitted to cyclic loading and corrosive attacks that aggravate the problem. All the influencing factors and approaches used during the design phase are also discussed

Systems design study of the Pioneer Venus spacecraft. Appendices to volume 1, sections 3-6 (part 1 of 3)

The design is described of the Venus probe windows, which are required to measure solar flux, infrared flux, aureole, and cloud particles. Window heating and structural materials for the probe window assemblies are discussed along with the magnetometer. The command lists for science, power and communication requirements, telemetry sign characteristics, mission profile summary, mass properties of payloads, and failure modes are presented

Orbital construction demonstration study

A conceptual design and program plan for an Orbital Construction Demonstration Article (OCDA) was developed that can be used for evaluating and establishing practical large structural assembly operations. A flight plan for initial placement and continued utility is presented as a basic for an entirely new shuttle payload line-item having great future potential benefit for space applications. The OCDA is a three-axis stabilized platform in low-earth orbit with many structural nodals for mounting large construction and fabrication equipments. This equipment would be used to explore methods for constructing the large structures for future missions. The OCDA would be supported at regular intervals by the shuttle. Construction experiments and consumables resupply are performed during shuttle visit periods. A 250 kw solar array provides sufficient power to support the shuttle while attached to the OCDA and to run construction experiments at the same time. Wide band communications with a Telemetry and Data Relay Satellite compatible high gain antenna can be used between shuttle revisits to perform remote controlled, TV assisted construction experiments

Antenna pattern shaping, sensing, and steering study Final report

Design of steerable satellite antenna with beam pattern sensing syste

Fracture mechanics based prediction of undercut tolerances in industry

Undercuts are geometrical discontinuities or grooves along the toe of a weld caused by loss of the parent material that remain unfilled by weld metal. Regardless of their causes, undercuts can be found in structures and components, in the majority of joints and most of the welding processes. Due to their frequency of appearance in welded structures and their detrimental effects on component life, undercut acceptance criteria had to be regulated by construction codes and standards. Depending on the area where the component is in service, specific tolerances must be satisfied in order to accept or reject the part. In general, undercut depth is considered to be the limiting parameter for this kind of imperfection. However, there is currently in industry no agreement about which value of depth is tolerable for a desired fatigue strength. The purposes of the present paper are twofold. First, to summarise the state of art associated to undercut tolerances in different codes, standards and recommendation documents, for different industries and applications. Secondly, to employ a fracture mechanics based methodology to predict safe undercut dimensions for butt welds subjected to fatigue. Predictions are in good agreement with experimental results from literature, and proposed method proved to be helpful for assessing weld discontinuities.Fil: Steimbreger, Ceferino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Chapetti, Mirco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Structural Stability of Offshore Platforms

Given the hostile nature of offshore environments, ensuring the structural stability of offshore structures is vital to their design. Acomputer program was developed for the preliminary stability analysis ofoffshore platforms under major environmental loads. The program output was interpreted for a minimum facility platform under extreme storm conditions. Also, athorough framework was set for experimental studies ofthe platform's stability using a scaled physical model. Literature review started with gathering general background information on offshore platforms. This included identifying their various types, their numbers worldwide and their construction. Next, structural stability of offshore platforms was studied in terms of the various loads exerted on offshore rigs and methods for their structural analysis. Finally, arecently installed Minimum Facility Platform was examined as an introduction to the case study structure. The platform chosen as case study for the project was ahypothetical Braced Caisson structure located at 36m of water in the North Sea. Its conceptual design and reliability assessment under extreme storm conditions were reviewed. Acomputer program was developed to calculate total base shear resulting from winds, waves and currents. The program was run for the case study platform under extreme storm conditions and results were interpreted. The breakdown of base shear by environmental loads and structural members was studied. Valuable insights were aninfr? into thp qpn^itivlfv rvf*n1ot6 •1 u:i:.. . . .: . i I The framework was defined for scale model experiments of the case study platform to assess its structural stability. Conducting the experiments by others would then be possible. The author built a model ofthe case study platform scaled down at 1:110. A hydraulic flume would then replicate storm conditions at the platform site. Expenmental setup and procedures were thoroughly specified. Procedures for measurement using a strain gauge were identified. Finally, steps to correlate results with platform stability were established

Determination of the material/geometry of the section most adequate for a static loaded beam subjected to a combination of bending and torsion

Dissertação de mestrado integrado em Engenharia de MateriaisThe Finite Element Method (FEM) is widely used to solve structural analysis problems. In this work, a novel Finite Element Model Updating methodology for static analysis is presented. The aim of the work is to improve the quality of the results using the Finite Element Updating techniques, by optimizing geometric parameters of the models and material properties in order to minimize deflection. Deflection can be minimized by increasing the Inertia moment of the section and/or Young modulus of the material. The Young modulus can be optimized by selecting an adequate material. In this work, material selection charts were used to determine the most reliable material. The selected material was then tested by tensile and extensometry tests to obtain Young modulus, Yield stress, and Poisson coefficient. The Inertia moment can be maximized by improving the geometry of the section, such as adding ribs or webs. A substantial improvement of the deflection can be achieved, but, in order to obtain the best results, optimization must be used. A MATLAB program was used to optimize the ANSYS models using a programming code. In order to know if the results are getting worse or better in relation to the previous iterations, an objective function was defined. The model is optimized when is not possible to further optimize the objective function.O método dos elementos finitos (FEM) é amplamente utilizado para resolver problemas de análise estrutural estática. Neste trabalho é apresentada uma nova metodologia de melhoria de modelos de elementos finitos para análise estática. O objectivo do trabalho é melhorar a qualidade dos resultados utilizando as técnicas de melhoramento de elementos finitos, através da optimização de parâmetros geométricos dos modelos e propriedades do material, de modo a reduzir os deslocamentos. Os deslocamentos podem ser minimizados através do aumento do momento de Inércia da secção e/ou módulo de Young do material. O módulo de Young pode ser optimizado através da escolha de um material adequado. Neste trabalho foram usadas cartas de selecção de materiais para determinar o material mais adequado. Foram feitos ensaios de extensometria e de tracção ao material seleccionado para obter as propriedades relevantes do material: módulo de Young, tensão de Cedência e coeficiente de Poisson. O momento de inércia pode ser maximizado melhorando a geometria da secção com nervuras ou redes longitudinais. Uma melhoria substancial do deslocamento pode ser obtida, mas, de modo a obter os melhores resultados, tem de se usar optimização. O programa MATLAB foi utilizado para optimizar os modelos do ANSYS com um código de programação. De modo a saber se os resultados estão a melhorar ou a piorar em cada iteração, em relação às iterações anteriores, uma função objectivo foi definida. O modelo está optimizado quando não é possível optimizar mais a função objectivo

COMPARISON OF DESIGN AND ANALYSIS OF TUBE SHEET THICKNESS BY USING UHX CODE OF ASME AND TEMA STANDARD

ABSTRACT In order to investigate the optimized tube sheet thickness different methodologies are used. For the mechanical design of existing fixed tube sheet heat exchanger of a waste heat Boiler various code solutions are compared with each other. Solutions of Finite Element Analysis are used to optimize the design parameters. The purpose of this paper is to compare and analyse tube sheet design code UHX of ASME section VIII Div. 1 with TEMA standards. From the design methodology it is found that both standards are based on different theory of design. It is also found that FE analysis results are closed to exact solution and these results can be accepted with a reasonable degree of accuracy. Thus FEA can be used as an optimization tool for tube sheet thickness

Textile Reinforced Structural Composites for Advanced Applications

Textile-reinforced composites are increasingly used in various industries such as aerospace, construction, automotive, medicine, and sports due to their distinctive advantages over traditional materials such as metals and ceramics. Fiber-reinforced composite materials are lightweight, stiff, and strong. They have good fatigue and impact resistance. Their directional and overall properties can be tailored to fulfill specific needs of different end uses by changing constituent material types and fabrication parameters such as fiber volume fraction and fiber architecture. A variety of fiber architectures can be obtained by using two- (2D) and three-dimensional (3D) fabric production techniques such as weaving, knitting, braiding, stitching, and nonwoven methods. Each fiber architecture/textile form results in a specific configuration of mechanical and performance properties of the resulting composites and determines the end-use possibilities and product range. This chapter highlights the constituent materials, fabric formation techniques, production methods, as well as application areas of textile-reinforced composites. Fiber and matrix materials used for the production of composite materials are outlined. Various textile production methods used for the formation of textile preforms are explained. Composite fabrication methods are introduced. Engineering properties of textile composites are reviewed with regard to specific application areas. The latest developments and future challenges for textile-reinforced composites are presented

Modeling the integration of thermoelectrics in anode exhaust combustors for waste heat recovery in fuel cell systems

Recently developed small-scale hydrocarbon-fueled fuel cell systems for portable power under 1 kW have overall system efficiencies typically no higher than 30-35%. This study explores the possibility of using of thermoelectric waste heat recovery in anode exhaust combustors to improve the fuel cell system efficiencies by as much as 4-5% points and further to reduce required battery power during system start-up. Two models were used to explore this. The first model simulated an integrated SOFC system with a simplified catalytic combustor model with TEs integrated between the combustor and air preheating channels for waste heat recovery. This model provided the basis for assessing how much additional power can achieve during SOFC operation as a function of fuel cell operating conditions. Results for the SOFC system indicate that while the TEs may recover as much as 4% of the total fuel energy into the system, their benefit is reduced in part because they reduce the waste heat transferred back to the incoming air stream and thereby lower the SOFC operating temperatures and operating efficiencies. A second model transient model of a TE-integrated catalytic combustor explored the performance of the TEs during transient start-up of the combustor. This model incorporated more detailed catalytic combustion chemistry and enhanced cooling air fin heat transfer to show the dynamic heating of the integrated combustor. This detailed model provided a basis for exploring combustor designs and showed the importance of adequate reactant preheating when burning exhaust from a reformer during start-up for the TEs to produce significant power to reduce the size of system batteries for start-up