Rozprawy doktorskie na temat „Aluminium Beads”

During recent decades, the use of aluminium lipped channel (ALC) beams as purlins, and floor joists in roof and floor systems in the construction industry has significantly increased due to their superior mechanical characteristics compared to steel, such as durability, light weight, high strength to weight ratio, and being weatherproof. However, despite these advantages, the elastic modulus of aluminium is only one-third that of steel. Hence ALC beams with shorter span lengths are vulnerable to buckling failures under concentrated load, such as shear and web crippling. On the other hand, ALC beams with longer span lengths can fail due to combined actions such as bending and shear actions, and bending and web crippling actions. In the past, the structural response of ALC beams has been investigated, but only under single actions of shear, web crippling, and bending. However, the behaviour of ALC beams subjected to combined bending and shear actions, and bending and web crippling actions needs to be investigated for real-world engineering applications. To address this research gap, experimental and numerical investigations on the strength and behaviour of ALC beams subjected to two scenarios of combined bending and shear actions, and combined bending and web crippling actions were conducted, and are presented in this thesis. The first step of the research focused on experimental investigation. Subsequently, numerical investigations including validation and parametric studies were carried out. Finally, the current available design rules were assessed and new design rules were proposed where needed. The experimental study comprised four test series of pure bending, web crippling, combined bending and shear actions, and combined bending and web crippling actions, using 12 different ALC sections. All ALC beams chosen for the experimental test program were supplied by BlueScope Permalite, Australia. The test specimens were fabricated by roll-forming method using aluminium alloy 5052-H36. A total of 62 tests were conducted on the ALC specimens, consisting of six four-point bending tests undergoing local buckling; nine web crippling tests under unfastened interior-one-flange (IOF) loading condition; 24 combined bending and shear tests considering two aspect ratios (ARs) of 1.5 and 2.0; and 23 combined bending and web crippling tests considering five interaction factors of 1.0, 1.5, 2.0, 2.5 and 3.0 under unfastened IOF loading condition. In the numerical study, nonlinear finite element (FE) models of ALC beams using ABAQUS/CAE software package were developed to simulate the behaviour of such beams under pure shear, web crippling, bending and combined actions. The developed FE models were validated by comparing the finite element analysis (FEA) results with those obtained from the tests. Good agreements were achieved throughout three criteria of ultimate capacities, applied load versus vertical displacement curves, and failure modes. The developed FE models were then used to undertake a detailed parametric study to obtain a large dataset of the strengths of the ALC sections with different parameters. The ultimate capacities of ALC beams obtained from the tests and FE models were compared with those predicted using current design rules of AS/NZS 4600, including direct strength method (DSM), AS/NZS 1664.1, AISI S100, Eurocode 3 Part 1-3, and the previously proposed design equations. It was found that the current DSM was safe in predicting the ultimate bending moment capacities of ALC beams undergoing local buckling. The previously proposed design equations were reasonably reliable in predicting the shear and web crippling capacities of the ALC beams. The available design equations in the form of circular and linear interaction curves provided by AS/NZS 4600 and developed in the previous study were too conservative in estimating the combined bending and shear capacities of the ALC beams. Hence, new design equations were proposed in the current study for the accurate prediction of the capacities of ALC beams under combined bending and shear actions. The current design rules of AS/NZS 4600, AISI S100, and Eurocode 3 Part 1-3 are not suitable to predict the combined bending and web crippling capacities of the ALC beams accurately. Therefore, new design equations were developed for the accurate prediction of the combined bending and web crippling capacities of the ALC beams under unfastened and fastened IOF loading conditions.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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This project sought to design, implement and evaluate a process for the manufacture of porous, spherical salt beads, in order to enhance the reproducibility in mechanical properties of open cell aluminium foams made by a replication-based manufacturing technique. Porous beads were favoured in order to increase the dissolution rate of the salt from the preform, thereby making the manufacture of large foam parts practical. Salt beads were made by a novel method using fine NaCI powder, flour and water to make a paste that was subsequently disintegrated into large beads by mechanical stirring in oil. The NaCI paste viscosity was found to be important to the production of spherical beads and by varying the intensity of mechanical disintegration of the paste, control of the bead size was possible. The salt beads with sizes from 0.5 to 3 mm diameter were compacted into preforms and made into moulds for infiltration with molten pure aluminium by pressure- assisted investment casting. The heat treatment used to "cure" the plaster mould containing the preform was sufficient to remove the flour from the beads, sinter the preform and increase its strength. The effect of preform compaction conditions on the size, shape and volume fraction of porosity was quantified using a number of techniques, including mercury porosimetry, which was used to model the infiltration process. At the highest infiltration pressure 0.25 MPa (2.5 bar) the resulting foam densities were higher, but led to extensive penetration of molten aluminium into the porous beads, slowing down salt removal. In general, the compression strength increased with increasing foam density, and was highly reproducible, but where metal infiltration into the beads was extensive, the foam density increased but with little improvement in the compressive strength.

The diploma thesis deals with project of a new building of university dormitories in the city center of Brno. It is detached building with basement and four above-ground floors with the irregular rectangular shape. Dormitories can be divided into three fundamental parts. The underground garages can be considered as the first part. Parking places are designed only for students, occasional visitors, and employees. In the underground floor, technical rooms and large warehouse can be found. The second part is designed to the general public including association areas such as reception, coffee-house with outdoor terrace, copy center and tobacco shop. Rooms for students, manager offices, repairman’s room, and laundry can be found in the third part. In total there are 44 two-person rooms and one room for a disabled person on the second floor. The structural system of the building is a cast-in-place concrete frame with a filling of ceramic fittings. The external wall is insulated with mineral wool with a ventilated facade and fiber-cement facade tiles. The building is based on base piles with a pile under each pillar. Vegetation covers a flat roof as well as a part of the north side of the facade. There will also be a public park and two volleyball fields in the area.

The scope of this diploma thesis is design and processing of the project documentation of the guesthouse along with coffee shop. The proposed object of this thesis is located in the village Čeladná next to the golf course Prosper Golf Resort Čeladná, in the location designated for mixed constructions. One of the double-storeyed, non-cellular object with roofed surface and steep roof. The object is based on the base stripes made of plain concrete and on the reinforced concrete flaps. Carrying, perihepral and dividing walls are designed on the Velox systém. The same systém was used to design roof constructions. In the rooms with excessive width are filled with reinforced concrete columns. Part of the guesthouse and second floor of the coffee shop is designed with ventilated facade with wood paneling ThermoWood. The object is divided in two parts with common entrance section. One part of the coffee shop has ability to handle capacity of 70 guests. Part of the double-storeyed coffee shop is hygienic facilities, kitchen, room for employees, warehouse and mechanical ventilation. Second part of the object is the guesthouse with flat of the manager of the guesthouse. The guesthouse consists of room with hygienic facilities for 18 people, including barrier-free room. The rooms are divided in the first floor on separate units, the rooms with hygienic facilities and the apartments in the second floor has two rooms, kitchen and hygienic facilities. For the next parts of the guesthouse is warehouse clean and dirty laundry and shared kitchen. The whole first floor is designed as barrier-free. In front of the object is the parking lot for 21 cars, which 3 of the parking places are for the cars of the disabled.

In this thesis we study a novel soft-matter system that imitates motility. Our system consists of a few asymmetrically tapered brass rods and aluminium beads which are confined between two vertically shaking plates. The rods are motile due to interplay of their the fore-aft asymmetric shape, vibrational energy input, and the mechanics of contact with the bounding surfaces. Experiments done by our col- laborators revealed that the system undergoes a phase transition from a disordered state to an ordered coherently moving flock above a critical bead concentration. We have used time-driven numerical simulations and analytical theory to understand the physics underlying the phenomenon.

碩士
國立中正大學
光機電整合工程研究所
105
Ultrashort pulses laser, besides water jet-based and diamond tool-based, is a common method for glass substrate cutting. It provides a kind of material modification in the focal of volume method to separate materials. This type of processing method has characteristics such as extremely small pulse width (femtoseconds or even picoseconds), the ability of fine processing in substrates (to micron scale) and the ability to process on both metal and non-metal non-transparent materials. The principle behind laser processing is to remove surface material on the substrate by laser ablation, focus inside the substrate via thin and homogenous Bessel beans and cut through substrates after various laser scans. In this study, we use optical analysis design software ASAP to create the optical system. We analyze the energy distribution on the central focus spot after the Gaussian bean passing through the lens group. From the analysis, we are able to understand the transmission distance and the beam profile characteristics of Bessel beam. We also are able to obtain the required distance for processing in work environment through different lens combinations and to discuss possible factors that will affect the process quality of Bessel beam. Through the comparison between experiment and simulation, we are not only able to find the optimal the central of spot size and depth of focus for processing substrate cutting, but also improve the completeness of the beam profile from Bessel beam. Keywords: Bessel beam, Laser processing

碩士
大同大學
化學工程學系(所)
95
In a methanol steam reformer, the endothermic reactions are carried out, therefore, a large quantity of energy needs to provide in time to maintain the reactions at a constant temperature. In order to transfer the heat from the heat source usually located at the outer of the reactor tube into the catalyst bed in the reactor, we evaluate the heat transfer capability of the available catalyst dispersion mediums including the aluminum beads and r-Al2O3. The reforming reactions were carried out in a tubular reactor packed with the commercial MDC III catalysts and the adopted dispersion medium to study the effects of dispersion medium on the conversion of methanol and the selectivity of CO over CO2 at the same operating conditions (the ratio of water over methanol (S/C) equals to one, the operating temperature equals to 250℃). The experimental results show that adopting the aluminum beads can not only improve the heat transfer capability but also increase the methanol conversion to obtain a higher hydrogen production rate, although the CO selectivity in the product stream is some how higher than the reactions carried out adopting the r-Al2O3 as the dispersion medium. Furthermore, the full factor experimental design was applied to carry out the experiments to study the effects of the control factors (The first control factor was different catalyst loading at the upper and lower section of the reactor, while the second control factor was the location the temperature sensor at the upper and lower section of the reactor) on the performance of the reformer. On the basis of the defined objective function (the desirability in terms of the cumulative quantities of hydrogen and CO production), the experimental results show that it is incentive to adopt a uniformly distributed catalysts with the dispersion medium when Wc/F is greater than 0.011(kg s/mmol) . Otherwise, it is more incentive to adopt the paring of the operating control factors: the upper section of the reactor is loaded with less catalysts and the temperature is located at the upper section.

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do Paraná
When a structural damage changes the characteristics of stiffness and mass of a mechanical system, the dynamic behavior of this beam will also change. Only a few studies about the correlation between damage and the effect caused in dynamic behavior can be found. Based on this, this study will analyze the behavior of the natural frequencies and damping ratios of four aluminum beams, with and without damages. This work aims to determine the error between the two methods of data acquisition and the effects of the damage inflicted on the shape modes, natural frequencies and damping ratios for each beam. To achieve the purposes, initially, a numerical FEM simulation will be performed, followed by experimental impact tests, aiming to obtain the estimated natural frequencies and damping ratios. After this, damages will be made on these beams and the impact tests will be repeated for each beam. The FEM analysis will be performed using Ansys. For the impact tests, two data acquirement methods will be used during the impact testing, the first, using accelerometers to obtain the vibration response, the second using a Brüel & Kjær’s sound level meter. The obtained data will be compared and will be possible to determinate the error between the natural frequencies measured using both methods. The results obtained will be used to correlates the dynamic behavior with the damages inflicted on the beams. This paper allowed analyzing the usage viability of the sound level meter to measure the output of a vibrating system, considering certain limitations. In addition, the damage effects on the natural frequencies of the beams.
Quando um dano altera as características de massa e rigidez de um sistema (uma viga, por exemplo), seu comportamento dinâmico também é afetado. O estudo dos efeitos do dano infligido no comportamento modal é relativamente recente, tendo poucos estudos correlacionando o dano com seus efeitos em vigas. Baseado nisso, este estudo visa analisar o comportamento e variação do valor das frequências naturais e dos fatores de amortecimento de quatro vigas de alumínio com e sem danos. Este trabalho tem por objetivo determinar: o erro entre as medições efetuadas utilizando ambos os métodos de obtenção da resposta de vibração das vigas e os efeitos dos danos causados no comportamento modal do sistema analisado (modos de vibração, frequências naturais e fatores de amortecimento). Para tal, incialmente, uma simulação numérica utilizando elementos finitos será efetuada, seguida por testes de impacto, com o objetivo de obter as frequências naturais e os fatores de amortecimento para cada caso. A simulação numérica será efetuada utilizando o software Ansys e os testes de impacto utilizarão dois métodos de aquisição da resposta do sistema: utilizando acelerômetros e um medidor de pressão sonora. Os dados obtidos serão comparados e será possível determinar o erro entre os métodos de medição utilizados. Os resultados obtidos também serão utilizados para analisar os efeitos dos danos no comportamento dinâmico das vigas utilizadas. A elaboração deste trabalho possibilitou averiguar a viabilidade do uso de um medidor de pressão sonora para medição de vibrações, dentro de seus limites de utilização e suas limitações. Também foi possível analisar os efeitos dos danos nos valores de frequências naturais das vigas analisadas.

Sandwich beams are composite systems having high stiffness-to-weight and strength-to-weight ratios and are used as light weight load bearing components. The use of thin, strong skin sheets adhered to thicker, lightweight core materials has allowed industry to build strong, stiff, light, and durable structures. Due to the use of viscoelastic polymer constituents, sandwich beams can exhibit time-dependent behavior. This study examines and predicts the time-dependent behavior of sandwich beams driven by the viscoelastic foam core. Governing equations of the deformation of viscoelastic materials are often represented in differential form or hereditary integral form. A single integral constitutive equation is used to model linear viscoelastic materials by means of the Boltzmann superposition principle. Based on the strength of materials approach, the analytical solution for the deformation in a viscoelastic sandwich beam is determined based on the application of the Correspondence Principle and Laplace transform. Finite element (FE) method is used to analyze the overall transient responses of the sandwich systems subject to a concentrated point load at the midspan of the beam. A 2D plane strain element is used to generate meshes of the three-point bending beam. User material (UMAT) subroutine in ABAQUS FE code is utilized to incorporate the viscoelastic constitutive model for the foam core. Analytical models and experimental data available in the literature are used to verify the results obtained from the FE analysis. The stress, strain, and deformation fields during creep responses are analyzed. Parameters such as the viscosity of the foam core, the ratio of the skin and core thicknesses, the ratio of the skin and core moduli, and adhesive layers are varied and their effect on the timedependent behavior of the sandwich system is examined.

碩士
國立彰化師範大學
機電工程學系
97
In this paper the test microstructure was designed the triangular cantilever beam and fabricated by the standard C-MOS processes, which can improve stress distribution non-uniform problem and the thickness regime of deposited metal thin film on its surface could reduce to several nanometers. In order to reduce the measure error and calculation complex due to the contact force (like indenter), the driving system was used electrostatic force to making the paddle cantilever beam bend and the deflection of paddle cantilever beam due to the electrostatic force was measured by a point laser reflected from paddle plate into the Position Sensing Detector (PSD). According to the displacement of the laser point on the PSD using a simple geometry calculation the deflection of paddle cantilever will be obtained. Than, we figure out the stress versus the stain and the Young’s Modulus of the thin films. It presents the mechanical properties of thin films.

碩士
國立臺灣海洋大學
機械與機電工程學系
101
The face/core interfacial crack behavior of the sandwich beams with glass/polypropylene faces and aluminum foam cores was experimentally studied in this thesis using mixed-Mode bending (MMB) method. The effects of the mixed Mode at the crack tips and the core heights on the critical loads and the critical strain energy release rates at the interfaces of the studied sandwich structures under the static loading were investigated first. The mixed Mode at the crack tips can be adjusted by changing the length of level arm of the MMB configuration. The finite element method was employed to determine the Mode-mixity at the crack tips, which was expressed using the phase angles. Secondly, the relationship between the crack propagation rate and the range of strain energy release rate for the studied pre-cracked sandwich beams was experimentally determined. The effects of the mixed Mode at the crack tips and the core heights on the crack propagation rates were also studied. In this study, the beam theory was used to obtain the compliance of the pre-cracked specimen under MMB, and correspondingly the strain energy release rate can be determined. Experimental results show that in the static tests, the critical loads and the critical strain energy release rates decrease as the phase angles at the crack tips of the studied specimens increase. In the fatigue tests, the crack propagation rate of the sandwich specimen with thinner core height is less than that with thicker core height. Furthermore, the ratios of the tensile Mode to the shear Mode at the crack tips have slight effect on the crack growth rates of the studied sandwich specimens.

碩士
國立臺灣海洋大學
機械與機電工程學系
101
Finite element method was employed in this thesis to analyze the face/core interfacial crack behavior of the sandwich beams with glass/polypropylene laminate faces and aluminum foam cores under mixed-mode bending (MMB). The finite element code ANSYS was employed to study the effects of core thicknesses, crack lengths, the lengths of level arms employed in the MMB loading configuration on the specimen compliance, local mixed modes, and the strain energy release rates at the interfaces. The beam theory was also used in the study to obtain the specimen compliance, local mixed mode and the strain energy release rate, which were compared with the results of finite element analyses. The mixed mode at the crack tip can be adjusted by changing the level arms of the MMB loading configuration, and the local mixed modes at the crack tips can be calculated using the finite element analysis and expressed using the phase angles. The finite element simulated results of the specimen compliances was also compared with the experiment results. The finite element results of the specimen compliances describe more accurate specimen compliance behaviors than the theoretical solution. Furthermore, the effects of the lengths of the level arm in MMB configuration, detailed dimensions of the specimens, and the mechanical properties of the face/core materials on the specimen compliances are significant. The mixed modes at the crack tips were found to remain constant when the normalized crack lengths are larger than 0.2. The larger length of level arms and larger core heights were found to increase the mode I loading in the mixed mode at the crack tips.