To see the other types of publications on this topic, follow the link: Fiber reinforced metal.
Dissertations / Theses on the topic 'Fiber reinforced metal'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Fiber reinforced metal.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Al-lami, Karrar Ali. "Experimental Investigation of Fiber Reinforced Concrete Beams." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2296.
Full textAbstract:
Shear strength of fiber reinforced concrete beams was studied in this research project. Three types of fibers were examined: hooked-end steel fiber, crimped-steel fiber, and crimped-monofilament polypropylene fibers. The experimental program included five beam specimens. Two of the beams were control specimens in which one was reinforced with minimum shear reinforcement according to ACI 318, while the other one did not have any shear reinforcement. Each one of the other three specimens was reinforced with one of the above mentioned fibers by 1% volumetric ratio. In addition to the beam specimens, three prisms were also made for each type fiber to determine their toughness.
The aim of this research was to investigate the following questions for medium-high concrete strength 1) to evaluate the effectiveness of each type of fibers on the shear strength, 2) to investigate the shear strength, toughness, crack patterns and near ultimate load crack width of each beam, and 3) to determine if using 1% volumetric ratio of fibers as shear reinforcement in beams would provide adequate strength and stiffness properties comparable to reinforcing steel used as minimum shear reinforcement.
The results showed that all three types of fibers increased the shear capacity of the beam specimens more than the beam reinforced with minimum shear reinforcement. Moreover, some of the fibers used could shift the type of failure from a pure shear failure to a combined flexural-shear or pure flexural failure.
2
Osiecki, Tomasz, Colin Gerstenberger, Holger Seidlitz, Alexander Hackert, and Lothar Kroll. "Behavior of Cathodic dip Paint Coated Fiber Reinforced Polymer/Metal Hybrids." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-175536.
Full textAbstract:
Increasing mechanical, economic and environmental requirements lead to multi material designs, wherein different classes of materials and manufacturing processes are merged to realize lightweight components with a high level of functional integration. Particularly in automotive industry the use of corresponding technologies will rise in the near future, as they can provide a significant contribution to weight reduction, energy conservation and therefore to the protection of natural resources. Especially the use of continuous fiber reinforced polymers (FRP) with thermoplastic matrices offers advantages for automotive components, due to its good specific characteristics and its suitability for mass production. In conjunction with isotropic materials, such as steel or aluminum, optimized lightweight structures can be produced, whose properties can be easily adapted to the given component requirements.
The present paper deals with the development of innovative hybrid laminates with low residual stresses, made of thin-walled steel sheets and glass fiber reinforced thermoplastic (GFRP) prepregs layers. Thereby the interlaminar shear strength (ILSS) was increased by an optimization of the FRP/metal-interfaces, carried out by examining the influence of several pre-operations like sanding, cleaning with organic solvents and applying primer systems. Based on these findings optimized compound samples were prepared and tested under realistic Cathodic dip paint conditions to determine the influence on the ILSS.
3
Yang, Yanzhe. "Fabrication of Long-Fiber-Reinforced Metal Matrix Composites Using Ultrasonic Consolidation." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/213.
Full textAbstract:
This research is a systematic study exploring a new fabrication methodology for long-fiber-reinforced metal matrix composites (MMCs) using a novel additive manufacturing technology. The research is devoted to the manufacture of long-fiber-reinforced MMC structures using the Ultrasonic Consolidation (UC) process. The main objectives of this research are to investigate the bond formation mechanisms and fiber embedment mechanisms during UC, and further to study the effects of processing parameters on bond formation and fiber embedment, and the resultant macroscopic mechanical properties of UC-made MMC structures. From a fundamental research point of view, bond formation mechanisms and fiber embedment mechanisms have been clarified by the current research based on various experimental observations. It has been found that atomic bonding across nascent metal is the dominant bond formation mechanism during the UC process, whereas the embedded fiber are mechanically entrapped within matrix materials due to significant plastic deformation of the matrix material during embedment. From a manufacturing process point of view, the effects of processing parameters on bond formation and fiber embedment during the UC process have been studied and optimum levels of parameters have been identified for manufacture of MMC structures. An energy-based model has been developed as a first step toward analytically understanding the effects of processing parameters on the quality of ultrasonically consolidated structures. From a material applications point of view, the mechanical properties of ultrasonically consolidated structures with and without the presence of fibers have been characterized. The effects on mechanical properties of UC-made structures due to the presence of embedded fibers have been discussed.
4
Lam, Su Ki. "Design of tough, metal fibre reinforced ceramics for use at high temperatures." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708380.
Full text
5
Funn, John V. "Creep behavior of the interface region in continuous fiber reinforced metal-matrix composites." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA341255.
Full textAbstract:
Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, September 1997."September 1997." Thesis advisor(s): Indranath Dutta. Includes bibliographical references (p. 91-93). Also available online.
6
Richard, Brandon Demar. "Thermal Infrared Reflective Metal Oxide Sol-Gel Coatings for Carbon Fiber Reinforced Composite Structures." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4569.
Full textAbstract:
Recent trends in composite research include the development of structural materials with multiple functionalities. In new studies, novel materials are being designed, developed, modified, and implemented into composite designs. Typically, an increase in functionality requires additional material phases within one system. The presence of excessive phases can result in deterioration of individual or overall properties. True multi-functional materials must maintain all properties at or above the minimum operating limit. In this project, samples of antimony and cobalt-doped tin oxide (ATO(Co2O3)) sol-gel solutions are used to coat carbon fibers and are heat treated at a temperature range of 200 - 500 °C. Results from this research are used to model the implementation of sol-gel coatings into carbon fiber reinforced multifunctional composite systems. This research presents a novel thermo-responsive sol-gel/ (dopant) combination and evaluation of the actuating responses (reflectivity and surface heat dissipation) due to various heat treatment temperatures. While ATO is a well-known transparent conductive material, the implementation of ATO on carbon fibers for infrared thermal reflectivity has not been examined. These coatings serve as actuators capable of reflecting thermal infrared radiation in the near infrared wavelengths of 0.7-1.2 μm. By altering the level of Co2O3 and heat treatment temperatures, optimal optical properties are obtained. While scanning electron microscopy (SEM) is used for imaging, electron diffraction
spectroscopy (EDS) is used to verify the compounds present in the coatings. Fourier transform infrared (FT-IR) spectroscopy was performed to analyze the chemical bonds and reflectivity in the infrared spectra after the heat treatments. Total reflection and angle-dependent reflectivity measurements were performed on the coatings in the wavelengths of 0.7-2 μm. Laser induced damage threshold testing was done to investigate the dielectric breakdown and used to calculate surface temperatures.
7
Butler, Joseph Edmund. "In-situ Fiber Strength Distribution in NextelTM 610 Reinforced Aluminum Composites." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32433.
Full textAbstract:
MetPreg, a composite developed by Touchstone Research Laboratories (Tridelphia, WV), is an aluminum metal matrix composite reinforced by continuous NextelTM 610 alumina fibers. The question is, after processing, are the NextelTM fibers affected in any way that their strengthening contribution to the composite is reduced? From experimentation and statistical analysis, a strength distribution of pre-processed NextelTM 610 fibers is formed and an empirical correlation is developed relating strength to the observed flaw size on the failed single fibers. This correlation is then independently applied to flaw size information gathered from fibers on the fracture surface of MetPreg samples to develop a separate strength distribution of post-processed NextelTM 610 fibers. The pre- and post-processed distributions are compared to one another to determine the effect, if any, that composite processing has on the strength of NextelTM 610 fibers. The results indicate that the in-situ strength distribution of fibers was increased by composite processing.Master of Science
8
Durkin, Craig Raymond. "Low-Cost Continuous Production of Carbon Fiber-Reinforced Aluminum Composites." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19857.
Full textAbstract:
The research conducted in this study was concerned with the development of low-cost continuous production of carbon fiber/aluminum composites. Two coatings, alumina and zirconia, were applied to the fibers to protect against interfacial degradation. They were applied using a sol-gel method and common metal salts. The fibers were infiltrated with molten aluminum using an ultrasound sonicator. The resultant composites were well-infiltrated and were tested in tension to determine their mechanical properties. Strengths were only 15-35% of the theoretical values predicted by the rule of mixtures. The composite microstructure revealed a sizable void fraction and that the fibers within the composites did not contain any coating on their surface. It was hypothesized that this was a result of few exposed graphite plane edges on the fiber surface, causing poor adhesion of the oxide coating to the fiber surface. To improve adhesion, an amorphous carbon coating was applied to the fiber surface, but still the oxide coatings were removed from the fibers upon infiltration. It was found, however, that the carbon coating on its own did strengthen the interface between the fiber and the aluminum.
9
Belghiti, Moulay El Mehdi. "Influence of steel fibres on response of beams." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100222.
Full textAbstract:
The following thesis presents the results of six full scale beams tests as part of a research program conducted at McGill University on the effect of steel fibres on the shear capacity of a beam with an aid ratio greater than 2.5. The test specimens had the following dimensions: 4400 mm long, 300 mm wide and 500 mm long. The beams had 4-25M bottom reinforcing bars and 2-20M top reinforcing bars. Two series were designed with different reinforcing details: the "BA" series contained transverse reinforcement spaced at 275 mm center to center while the "BB" series had no transverse reinforcement. The specimens were cast in three batches of two specimens from each series, with each batch containing concrete with respectively 0%, 0.5% and 1% fibres content by volume. The beams were simply supported and were tested with two equal point loads located at 500 mm from the centre of the beam.This research project demonstrated a clear improvement of the shear capacity resulting from the use of steel fibres for the beams without transverse reinforcement. For the beams with transverse reinforcement, displacement ductility was highly increased. This suggests that fibres have the potential to reduce the congestion of the reinforcement if fibres are designed to replace partially closely spaced transverse reinforcement. Also, it was noted that a redistribution of stresses occurred resulting in the formation of more well-controlled cracks. Finally, the strength predictions using the method developed by Aoude (Aoude, 2007) agree very well with the experimental results.
10
Tu, Zhiqiang. "Fabrication and Mechanical Properties of Carbon Fiber Reinforced Aluminum Matrix Composites by Squeeze Casting." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40523.
Full textAbstract:
Rapid modern technological changes and improvements bring great motivations in advanced material designs and fabrications. In this context, metal matrix composites, as an emerging material category, have undergone great developments over the past 50 years. Their primary applications, such as automotive, aerospace and military industries, require materials with increasingly strict specifications, especially high stiffness, lightweight and superior strength. For these advanced applications, carbon fiber reinforced aluminum matrix composites have proven their enormous potential where outstanding machinability, engineering reliability and economy efficiency are vital priorities.
To contribute in the understanding and development of carbon fiber reinforced aluminum matrix composites, this study focuses on composite fabrication, mechanical testing and physical property modelling. The composites are fabricated by squeeze casting. Plain weave carbon fiber (AS4 Hexcel) is used as reinforcement, while aluminum alloy 6061 is used as matrix. The improvement of the squeeze casting fabrication process is focused on reducing leakage while combining thermal expansion pressure with post-processing pressing. Three different fiber volume fractions are investigated to achieve optimum mechanical properties. Piston-on-ring (POR) bend tests are used to measure the biaxial flexural stiffness and fracture strength on disc samples. The stress-strain curves and fracture surfaces reveal the effect of fiber-matrix interface bonding on composite bend behaviour. The composites achieved up to 11.6%, 248.3% and 90.1% increase in flexural modulus, strain hardening modulus and yield strength as compared with the unreinforced aluminum alloy control group, respectively. Analytical modelling and finite element modelling are used to comparatively characterise and verify the composite effective flexural modulus and strength. Specifically, they allowed
iii
evaluating how far the experimental results deviate from idealized assumptions of the models, which provides an insight into the composite sample quality, particularly at fiber-matrix interfaces. Overall, the models agree well with experimental results in identifying an improvement in flexural modulus up to a carbon fiber volume fraction of 4.81vol%. However, beyond a fiber content of 3.74vol%, there is risk of deterioration of mechanical properties, particularly the strength. This is because higher carbon fiber volume fractions restrict the infiltration and wetting of carbon fibre by the liquid, potentially leading to poor fiber-matrix interface bonding. It is shown that higher thermal expansion pressures and subsequent post-processing pressing can overcome this challenge at higher carbon fiber volume contents by reducing fiber-aluminum contact angle, improving infiltration, reducing defects such as porosity, and overall improving fiber-matrix bonding.
11
Foster, Glenn C. "Tensile and Flexure Strength of Unidirectional Fiber-Reinforced Composites: Direct Numerical Simulations and Analytic Models." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36688.
Full textAbstract:
A Local Load Sharing (LLS) model recently developed by Curtin
and co-workers for the numerical simulation of tensile
stress-strain behavior in fiber-reinforced composites is used
to predict the tensile strength of metal matrix composites
consisting of a Titanium matrix and unidirectionally aligned
SiC fibers.
This model is extended to include the effects of free
boundary conditions and non-constant load gradients and then
used to predict the strength of a Ti-6Al-4V matrix reinforced
with Sigma SiC fibers under 4-point flexure testing.
The predicted tensile and flexure strengths agree very well
with the values measured by Gundel and Wawner and Ramamurty
et al.
The composite strength of disordered spatial fiber
distributions is investigated and is shown to have a
distribution similar to the corresponding ordered composite,
but with a mean strength that decreases (as compared to the
ordered composite) with increasing Weibull modulus.
A modified Batdorf-type analytic model is developed and
similarly extended to the case of non-uniform loading to
predict the strength of composites under tension and flexure. The
flexure model is found to be inappropriate for application
to the experimental materials, but the tensile model yields
predictions similar to the Local Load Sharing models for the
experimental materials.
The ideas and predictions of the Batdorf-type model, which
is essentially an approximation to the simulation model, are
then compared in more detail to a simulation-based model
developed by Ibnabdeljalil and Curtin to more generally
assess the accuracy of the Batdorf model in predicting
tensile strength and notch strength versus composite size
and fiber Weibull modulus.
The study shows the Batdorf model to be accurate for tensile
strength at high Weibull moduli and to capture general trends
well, but it is not quantitatively accurate over the full
range of material parameters encountered in various fiber
composite systems.Master of Science
12
King, Joel David. "Characterization of the corrosion of a P-130x graphite fiber reinforced 6063 aluminum metal matrix composite." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25734.
Full text
13
Keles, Ozgur. "Production And Characterization Of Alumina Fiber Reinforced Squeeze Cast Aluminum Alloy Matrix Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609726/index.pdf.
Full textAbstract:
The aim of the present study was to investigate the effects of different levels of Saffil alumina fiber addition, magnesium content in aluminum alloy matrix and casting temperature on the mechanical behavior, microstructure and physical properties of short fiber reinforced aluminum matrix composites. The main alloying element silicon was kept constant at 10 wt%. Magnesium contents were selected as 0.3 wt% and 1 wt%. Saffil alumina fiber preforms varied from 10 to 30 vol%. The casting temperatures were fixed at 750 °C and 800 °
C. Micro porosity was present at the fiber-fiber interactions. Closed porosity of the composites increased when fiber vol% increased, however, variation in casting temperature and magnesium content in matrix did not have influence on porosity. Hardness of the composites was enhanced with increasing fiber vol%, magnesium content in matrix and decreasing casting temperature. Alignment of fibers within the composite had an influence on hardness
when fibers were aligned perpendicular to the surface, composites exhibited higher hardness. The highest hardness values obtained from surfaces parallel and vertical to fiber orientation were 155.6 Brinell hardness and 180.2 Brinell hardness for AlSi10Mg1 matrix 30 vol% alumina fiber reinforced composite cast at 800 °
C and at 750 °
C, respectively. 30 vol% Saffil alumina fiber reinforced AlSi10Mg0.3 matrix composite cast at 750 °
C showed the highest flexural strength which is 548 MPa. Critical fiber content was found as 20 vol% for all composites.
14
Turkyilmaz, Gokhan. "Processing And Assessment Of Aluminum Ceramic Fiber Reinforced Aluminum Metal Matrix Composite Parts For Automotive And Defense Applications." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610751/index.pdf.
Full textAbstract:
The aim of this study was to produce partially reinforced aluminum metal matrix
composite components by insertion casting technique and to determine the effects
of silicon content, fiber vol% and infiltration temperature on the mechanical
properties of inserts, which were the local reinforcement parts of the components.
Silicon content of alloys was selected as 7 wt% and 10 wt%. The reinforcement
material, i.e. Saffil fiber preforms, had three different fiber vol% of 20, 25 and 30
vol% respectively. The infiltration temperatures of composite specimens were fixed
as 750 °C and 800 °
C. In the first part of the thesis, physical and mechanical properties of composite specimens were determined according to the parameters of silicon content of the matrix alloy, infiltration temperature and vol% of the reinforcement phase. X-ray diffraction examination of fibers resulted as the fibers mainly composed of deltaalumina fibers and scanning electron microscopy analyses showed that fibers had planar isotropic condition for infiltration. Microstructural examination of composite specimens showed that appropriate fiber/matrix interface was created together with small amount of micro-porosities. Bending tests of the composites showed that as fiber vol% increases flexural strength of the composite increases. The highest strength obtained was 880.52 MPa from AlSi10Mg0.8 matrix alloy reinforced with 30 vol% Saffil fibers and infiltrated at 750 °
C. Hardness values were also increased by addition of Saffil fibers and the highest value was obtained as 191 HB from vertical to the fiber orientation of AlSi10Mg0.8 matrix alloy reinforced with 30 vol% Saffil fibers. Density measurement revealed that microporosities existed in the microstructure and the highest difference between the theoretical values and experimental values were observed in the composites of 30 vol% Saffil fiber reinforced ones for both AlSi7Mg0.8 and AlSi10Mg0.8 matrix alloys. In the second part of the experiments, insertion casting operation was performed. At casting temperature of 750 °
C, a good interface/component interface was obtained. Image analyses were also showed that there had been no significant fiber damage between the insert and the component.
15
Bandi, Raghava. "Effect of Surface Treatment on the Performance of CARALL, Carbon Fiber Reinforced Aluminum Dissimilar Material Joints." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011869/.
Full textAbstract:
Fiber-metal laminates (FML) are the advanced materials that are developed to improve the high performance of lightweight structures that are rapidly becoming a superior substitute for metal structures. The reasons behind their emerging usage are the mechanical properties without a compromise in weight other than the traditional metals. The bond remains a concern. This thesis reviews the effect of pre-treatments, say heat, P2 etch and laser treatments on the substrate which modifies the surface composition/roughness to impact the bond strength. The constituents that make up the FMLs in our present study are the Aluminum 2024 alloy as the substrate and the carbon fiber prepregs are the fibers. These composite samples are manufactured in a compression molding process after each pre-treatment and are then subjected to different tests to investigate its properties in tension, compression, flexural and lap shear strength. The results indicate that heat treatment adversely affects properties of the metal and the joint while laser treatments provide the best bond and joint strength.
16
Canino-Vazquez, Iván R. "Aerodynamic Load Characteristics Evaluation and Tri-Axial Performance Testing on Fiber Reinforced Polymer Connections and Metal Fasteners to Promote Hurricane Damage Mitigation." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/128.
Full textAbstract:
Damages during extreme wind events highlight the weaknesses of mechanical fasteners at the roof-to-wall connections in residential timber frame buildings. The allowable capacity of the metal fasteners is based on results of unidirectional component testing that do not simulate realistic tri-axial aerodynamic loading effects. The first objective of this research was to simulate hurricane effects and study hurricane-structure interaction at full-scale, facilitating better understanding of the combined impacts of wind, rain, and debris on inter-component connections at spatial and temporal scales. The second objective was to evaluate the performance of a non-intrusive roof-to-wall connection system using fiber reinforced polymer (FRP) materials and compare its load capacity to the capacity of an existing metal fastener under simulated aerodynamic loads. The Wall of Wind (WoW) testing performed using FRP connections on a one-story gable-roof timber structure instrumented with a variety of sensors, was used to create a database on aerodynamic and aero-hydrodynamic loading on roof-to-wall connections tested under several parameters: angles of attack, wind-turbulence content, internal pressure conditions, with and without effects of rain. Based on the aerodynamic loading results obtained from WoW tests, sets of three force components (tri-axial mean loads) were combined into a series of resultant mean forces, which were used to test the FRP and metal connections in the structures laboratory up to failure. A new component testing system and test protocol were developed for testing fasteners under simulated tri-axial loading as opposed to uni-axial loading. The tri-axial and uni-axial test results were compared for hurricane clips. Also, comparison was made between tri-axial load capacity of FRP and metal connections. The research findings demonstrate that the FRP connection is a viable option for use in timber roof-to-wall connection system. Findings also confirm that current testing methods of mechanical fasteners tend to overestimate the actual load capacities of a connector. Additionally, the research also contributes to the development a new testing protocol for fasteners using tri-axial simultaneous loads based on the aerodynamic database obtained from the WoW testing.
17
Ehmaida, Mutyaa M. "Friction and lubrication behaviour of hip resurfacing metal-on-metal and ZTA ceramic on CFR peek implants with various diameters and clearances : friction and lubrication behaviour of hip resurfacing Co-Cr-Mo and zirconia toughened alumina ceramic heads against carbon fibre reinforced poly-ether-ether-ketone cups with various diameters and clearances have been investigated using serum-based lubricants." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5665.
Full textAbstract:
Total hip joint prostheses made of CoCrMo heads versus ultra high molecular weight polyethylene (UHMWPE) cups have a limited lifetime, mainly due to the wear of the UHMWPE cups as a result of high friction between the articulating surfaces leading to osteolysis and implant loosening with revision surgery becoming inevitable in more active patients. Tribology plays an important role in developing the design, minimizing wear and reducing friction of hip joint prostheses in order to improve their long-term performance, with good lubricating properties. Metal-on-metal hip resurfacing prostheses have shown significantly lower wear rates compared with conventional metal-on-polyethylene implants and thus osteolysis is potentially reduced leading to increased lifetime of the prosthesis. Nevertheless, excessive wear of metal-on-metal joints leads to metal ion release, causing pseudo-tumours and osteolysis. An alternative approach to such bearings is the use of newly developed carbon fiber-reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups articulating against ceramic femoral heads due to their better wear resistance compared to UHMWPE. In this study, therefore, friction and lubrication properties of large diameter, as cast, Co-Cr-Mo metal-on-metal hip resurfacing implants with various diameters and clearances have been investigated and compared to those of the newly developed zirconia toughened alumina (ZTA) ceramic femoral heads articulating against carbon fiber reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups with different diameters and clearances. Friction hip simulator was used to measure frictional torque and then friction factors were calculated along with Sommerfeld numbers leading to Stribeck analysis and hence the lubricating mode was also investigated. This involved using lubricants based on pure bovine serum (BS) and diluted bovine serum (25 vol. %BS+75 vol. %distilled water) with and without carboxymethyl cellulose (CMC) (as gelling agent). Standard Rheometer was used to measure lubricant viscosity ranged from 0.0014 to 0.236 Pas at a shear rate of 3000 . Pure bovine serum, diluted bovine serum without CMC and with CMC (25BS+75DW+0.5gCMC and +1gCMC) showed pseudoplastic flow behaviour up to shear rate of ~139 s⁻¹ above which a Newtonian flow with significant increase in shear stress was observed. The viscosity flow curves for the 25BS+75DW+2gCMC, +3.5gCMC and +5gCMC showed only shear thinning up to a shear rate of 3000 . The shear rate application modified the flow behaviour of bovine serum from a pseudoplastic to a Newtonian flow depending on its purity and CMC content. This will cause a different frictional behaviour depending on joint diameter and clearance, as seen in this work. The experimental data were compared with theoretical iv predictions of the lubricating regimes by calculating theoretical film thickness and lambda ratio. The metal-on-metal Biomet ReCaps showed similar trends of Stribeck curves, i.e. friction factors decreased from ~0.12 to ~0.05 as Sommerfeld numbers increased in the range of viscosities ~0.001-0.04Pas indicating mixed lubrication regimes above which the friction factor increased to ~0.13 at a viscosity of 0.236Pas. The Stribeck analyses suggested mixed lubrication as the dominant mode with the lowest friction factor in the range ~0.09 - ~0.05 at the physiological viscosities of ~0.01 to ~0.04 Pas and that such joints can be used for more active patients as compared to the conventional total hip replacement joints with 28mm diameter. The Stribeck curves for all ZTA ceramic-on-CFR PEEK components illustrated a similar trend with BS fluids showing higher friction factors (in the range 0.22-0.13) than the diluted BS+CMC fluids (in the range 0.24-0.05). The friction tests revealed boundary-mixed lubrication regimes for the ZTA ceramic-on-CFR-PEEK joints. The results, so far, are promising and suggest clearly that the newly developed ZTA ceramic femoral heads articulating against CFR PEEK cups have similar friction and lubrication behaviour at optimum clearances to those of currently used metal-onmetal hip resurfacing implants at the range of viscosities 0.00612 to 0.155Pas. These results clearly suggest that the ZTA ceramic-on-CFR-PEEK joints showed low friction at the physiological viscosities of ~0.01Pas in the range ~0.1-0.05, suggesting that these novel joints may be used as an alternative material choice for the reduction of osteolysis. The result of this investigation has suggested that the optimum clearance for the 52mm diameter MOM Biomet ReCaps could be ~170μm. However, 48 and 54mm joints showed lower friction due to clearances to be >200μm. For the 52mm ZTA ceramic-on-CFR-PEEK joints the optimum clearance seems to be ≥ 630μm radial clearance. These results suggested that increased clearance bearings have the potential to generate low friction and hence no risk of micro- or even macro-motion for the ceramic-on-CFR-PEEK joints. This study found no correlation between theoretical predictions and experimental data for all metal-onmetal and ZTA ceramic-on-CFR PEEK bearings at the physiological viscosity (0.0127Pas). However, at lubricant viscosity of 0.00157Pas, the theoretical prediction of lubrication regime correlated well with the experimental data, both illustrating boundary lubrication. As expected, a decrease in viscosity resulted decrease in the film thickness.
18
Silva, Marcelo Gomes da. "Distribuição de tensões em próteses parciais fixas posteriores livres de metal com retentores intracoronários: análise em elementos finitos." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2764.
Full textAbstract:
Fundação de Amparo à Pesquisa do Estado do Rio de JaneiroPara reabilitar a ausência de um elemento dentário posterior, as próteses parciais fixas (PPF) com retentores intracoronários são uma alternativa aos implantes osseointegrados. O objetivo deste estudo foi avaliar a distribuição de tensões nessas próteses com três combinações de materiais: cerâmica de zircônia parcialmente estabilizada por ítria (ZPEI) revestida por cerâmica de fluorapatita (α), cerâmica de dissilicato de lítio (β) ou compósito fibrorreforçado (γ). Na composição α, foram analisadas a presença ou ausência da cerâmica de revestimento na parede cervical das caixas proximais e três variações na área total da seção transversal dos conectores (4 mm de largura x 3,2, 4,2 ou 5,2 mm de altura). Em 8 modelos bidimensionais de elementos finitos, uma carga vertical de 500 N foi aplicada na fossa central do pôntico e as tensões principais máximas (tração) e mínimas (compressão) foram apontadas em MPa. Inicialmente foram avaliados os 6 modelos com PPF de ZPEI e suas variações. Os maiores valores das tensões de tração foram encontrados no terço cervical dos conectores. Quando presente nestas regiões, a cerâmica de revestimento recebeu tensões acima do limite de sua resistência à flexão. Na comparação entre os modelos sem cerâmica de revestimento na parede cervical das caixas proximais, mesmo aquele com conectores de 3,2 x 4 mm, cuja infraestrutura apresentava 2,5 x 3 mm, poderia ser recomendado para uso clínico. Altos valores de tensões de compressão foram registrados entre o terço oclusal e médio dos conectores, correspondente à união entre as cerâmicas, o que poderia ocasionar, devido à flexão, falhas adesivas. Posteriormente, o modelo de ZPEI com a cerâmica de fluorapatita ausente da parede cervical das caixas proximais e área total dos conectores de 4,2 x 4 mm foi comparado aos dois outros materiais com conectores de mesma área. Na PPF de dissilicato de lítio, os valores representaram uma provável violação do limite de sua resistência à flexão. A PPF de compósito fibrorreforçado apresentou tensões bem abaixo do limite de resistência à flexão de sua infraestrutura, mas, como no modelo de ZPEI, tensões compressivas se concentraram com alto valor entre o terço oclusal e médio dos conectores, local de união entre a resina composta e a infraestrutura de fibras. Os resultados mostraram que a cerâmica de dissilicato de lítio e a presença da cerâmica de fluorapatita na parede cervical das caixas proximais deveriam ser contraindicadas para a condição proposta. Parece viável uma área de conectores na infraestrutura de ZPEI com no mínimo 2,5 x 3 mm. A PPF de compósito fibrorreforçado apresenta resistência estrutural para a situação estudada, mas, como também aquelas compostas de ZPEI, aparenta ter como pontos fracos a adesão entre a infraestrutura e o material de cobertura e a própria resistência deste último.
Inlay-retained fixed partial dentures (IRFPD) are an alternative to osseointegrated implants to replace a single missing posterior tooth. The aim of this study was to evaluate the stress distribution within these prostheses with three material combinations: yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic veneered with fluorapatite ceramic (α), lithium-disilicate ceramic (β) or fiber-reinforced composite (γ). In composition α, an analysis was conducted on the presence or absence of the veneering ceramic on the cervical wall of the proximal boxes and three variations in the total area of the connectors cross-section (4 mm in width x 3.2, 4.2 or 5.2 mm in height). In 8 two-dimensional finite element models, a vertical load of 500 N was applied on the central fossa of the pontic. Maximum (tension) and minimum (compression) principal stresses were then shown in MPa. First, the 6 models with Y-TZP fixed partial dentures (FPD) and their variations were evaluated. The highest values of tensile stresses were found at the cervical third of the connectors. When present in these regions, the veneering ceramic received stresses beyond its flexural strength limit. In the comparison among models without veneering ceramic on the cervical wall of the proximal boxes, even the model with connectors of 3.2 x 4 mm, whose framework presented 2.5 x 3 mm, could be recommended for clinical use. High values of compressive stresses were recorded between the middle and occlusal thirds of the connectors, corresponding to the juncture of the ceramics. Owing to flexure, these stresses might lead to adhesive failures. Then, the Y-TZP model without fluorapatite ceramic on the cervical wall of the proximal boxes and total connector area of 4.2 x 4 mm was compared to the other two materials with connectors of the same area. For the lithium-disilicate FPD, the observed values would probably exceed its flexural strength limit. The fiber-reinforced composite FPD presented stresses far below the flexural strength limit of its framework, but, as observed in the Y-TZP model, high values of compressive stresses were concentrated between the middle and occlusal thirds of the connectors, where the juncture of the composite and the fiber framework is located. The results showed that the use of lithium-disilicate ceramics and the presence of fluorapatite ceramics on the cervical wall of the proximal boxes should be contraindicated for the condition proposed. A minimum of 2.5 x 3 mm for the connector area of the Y-TZP framework seems viable. The fiber-reinforced composite FPD presented structural resistance for the situation studied but, as was also the case of the Y-TZP fixed partial dentures, its weak points seem to be the adhesion between the framework and the veneering material, as well as the resistance of the veneering material itself.
19
DEL, TORO RIVERA RAUL. "Comportement des noeuds d'ossature en beton arme sous sollicitations alternees." Marne-la-vallée, ENPC, 1988. http://www.theses.fr/1988ENPCA004.
Full textAbstract:
Etude des joints sous sollicitation sismique sur la base de trois essais sur corps d'epreuve de grande dimensionm en analysant les mecanismes des glissements constates des armatures principales dans la partie centrale du noeud, et le type de rupture a laquelle cela donne lieu; etude sur la base d'un essai de la possibilite d'utiliser un beton de fibres metalliques avec ferraillage transversal reduit
20
Delfaut, Laurence. "Elaboration et caractérisation d'un matériau composite nouveau à base de tungstène." Grenoble INPG, 1996. http://www.theses.fr/1996INPG4203.
Full textAbstract:
Pour la realisation de projectiles-fleches, il a ete envisage de remplacer les alliages lourds frittes par un nouveau materiau plus performant. Nous avons donc elabore un materiau composite unidirectionnel constitue d'une forte fraction volumique de fils de tungstene (diametre 1 mm) et d'une matrice en nickel. Ce materiau vise a exploiter au maximum les proprietes des fils de tungstene telles qu'une densite et une resistance tres elevees, une microstructure fibreuse conferant une certaine ductilite. Pour la mise en forme du materiau, nous avons choisi d'utiliser une technique peu exploitee mais parfaitement adaptee au materiau recherche (materiau isotrope transverse et a forte fraction volumique de fils en tungstene, utilisation de fils nickeles) qui est l'electroformage avec martelage rotatif a chaud (temperature < 1000c). Pour l'obtention d'un materiau parfaitement densifie et sans endommagement, il a ete necessaire de definir les parametres de mise en forme qui sont principalement la temperature et le taux de martelage a travers l'observation microstructurale du composite mais aussi a travers une etude sur l'evolution microstructurale et mecanique des fils de tungstene nickeles en fonction de la temperature de recuit ou d'essai. Ceci nous a amene a etudier le phenomene de reaction interfaciale qui se produit entre le tungstene et le depot de nickel a temperature superieure a 1000c et qui se caracterise par une recristallisation du fil de tungstene induite par une diffusion intergranulaire du nickel. Des essais en compression statique menes sur le materiau composite ont permis de montrer la forte resistance du composite (1800 mpa) ainsi qu'un bon comportement vis a vis de l'endommagement. Grace a ces essais, nous avons pu montrer qu'une approche micromecanique (loi des melanges) permet de prevoir correctement les caracteristiques mecaniques du composite en compression mais aussi en traction
21
Winfield, P. H. "Toughness development in fibre reinforced metals." Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259794.
Full text
22
Papworth, Adam John. "Squeeze-casting of fibre reinforced metal matrix composites." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364201.
Full text
23
Filho, Antonio de Padua Lima. "Production and properties of continuous fibre metal-reinforced metal matrix composites." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284793.
Full text
24
Dear, Matthew Nicholas. "Fatigue in SiC fibre reinforced titanium metal matrix composites." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6603/.
Full textAbstract:
The fatigue and interfacial characteristics of a unidirectional, SiC (SCS 6), fibre reinforced Ti 6Al 4V metal matrix composite have been investigated using a series of fatigue crack propagation, total life, and interfacial characterisation techniques. A room temperature crack arrest to catastrophic failure (CA/CF) transition was quantified using the initial stress intensity factor range ΔKapp. This transition occurred between 21 and 18 MPa√m in the three point bend geometry, and was found to be dependent on volume fraction of intact fibres bridging the crack. Increasing the test temperature to 300˚C had different effects on the resistance to fatigue crack growth depending on crack opening displacements and test piece stiffness. Total life fatigue tests revealed that the dominant failure mechanism was matrix fatigue cracking and fibre bridging. The extent of fatigue crack growth and fibre bridging was dependant on the applied stress and test temperature. The introduction of a dwell period at maximum load resulted in a small reduction in the total fatigue life. Post fatigue fibre push out tests identified that fatigue caused a reduction of interfacial properties below the as received levels. This reduction of interfacial properties was dependent on fatigue test temperature and initial loading conditions.
25
Demir, Adem. "Silicon carbide fibre reinforced #beta#-sialon ceramics." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391291.
Full text
26
Zamperini, Silvia. "Effects of cyclic loading on fibre reinforced titanium metal matrix composites." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289709.
Full text
27
Bystrický, Pavel. "Plasticity of metal matrix composites reinforced with continuous alumina fibers." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/44488.
Full text
28
Arola, Dwayne Dale. "The influence of net shape machining on the surface integrity of metals and fiber reinforced plastics /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/7138.
Full text
29
O'Rourke, Jane. "Microstructure and mechanical properties of fibre-reinforced heat-treatable aluminium alloys." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261348.
Full text
30
GuzmaÌn, J. Fernando GuilleÌn. "Cooling rate effects in glass reinforced thermoplastic-based fibre metal laminates." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399210.
Full text
31
Smith, Joel Edmund. "Development of improved metal matrix composite via the control of interface and matrix microstructure." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296330.
Full text
32
Behloul, Mouloud. "Analyse et modélisation du comportement d'un matériau à matrice cimentaire fibrée à ultra hautes performances : bétons de poudres réactives, du matériau à la structure." Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0026.
Full textAbstract:
L'objectif de ce travail est d'étudier le comportement mécanique des bétons de poudres réactives renforces de fibres métalliques (bpr) et de définir des modèles de calcul permettant la prédiction du comportement des structures en bpr. Le comportement du bpr sous différentes sollicitations: compression, traction et flexion est présenté dans un premier temps. Ensuite, la distribution des fibres dans les structures est étudiée et son aspect aléatoire quantifié ; une formulation empirique de sa dispersion est proposée. Cet aspect aléatoire de la distribution des fibres est intégré dans un modèle probabiliste. Ce modèle, base sur la loi du maillon le plus faible, permet de rendre compte du comportement de structures sollicitées en traction directe. Une approche continue permettant la prédiction du comportement des structures fléchies est développée. La loi de comportement représentative intervenant dans ce calcul est obtenue en utilisant le modèle probabiliste. Enfin, l'ensemble de cette approche est validée sur des structures de différentes tailles, précontraintes et non précontraintes
33
Li, Maojun. "Drilling of carbon fibre reinforced plastic (CFRP) and metal matrix composites (MMC)." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5953/.
Full textAbstract:
The use of carbon fibre reinforced plastic (CFRP) and metal matrix composites (MMC) is steadily increasing as an alternative to traditional metallic materials in various industrial sectors. The overall aim of the project is to assess the machinability when drilling epoxy based CFRP and Al/SiCp MMC composites and understand its effects on feature quality and workpiece integrity. Specific objectives of the project relate to establishing preferred/optimum operating parameters (cutting speed, feed rate and drill strategies) and investigating the influence of cutting environment (dry, chilled air, high pressure internal/external supplied coolant and low pressure flood) for drilling specific composite material systems. Key response measures include tool wear/life, thrust force/torque, hole size and geometrical accuracy, hole edge quality (delamination, uncut fibres and burrs) as well as workpiece surface integrity (surface roughness, microhardness, fibre/particle pullout, subsurface damage, etc.). The latest cutting tool materials and advanced diamond coatings, drill geometry and design format (e.g. domed PCD) were assessed in an attempt to improve productivity levels, tool life and hole quality. Tool wear mechanisms and its effect on hole surface quality were also investigated.
34
Batikha, Mustafa. "Strengthening of thin metallic cylindrical shells using fibre reinforced polymers." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/3994.
Full textAbstract:
Steel silos are widely used as long-term or short-term containers for the storage of granular solids, of which a huge range are stored, from flour to iron ore pellets, coals, cement, crushed rocks, plastic pellets, chemical materials, sand, and concrete aggregates. The radius to thickness ratio for silos is in the range of 200 to 3000, so they fall into the category of thin shells, for which failure by buckling is the main concern and requires special attention in design. The primary aim of this thesis is to investigate the possible application of Fibre Reinforced Polymer (FRP) as a new repair and strengthening technique to increase the buckling capacity of thin metallic cylindrical shells. Extensive research has been conducted on the use of fibre reinforced polymer (FRP) composites to strengthen concrete, masonry and timber structures as well as metallic beams. However, all these studies were concerned with failure of the structure by material breakdown, rather than stability. As a result, this thesis marks a major departure in the potential exploitation of FRP in civil engineering structures. Many analyses of cylindrical shells are presented in the thesis. These are all focussed on strengthening the shell against different failure modes. Two loading conditions were explored: uniform internal pressure accompanied by axial load near a base boundary, and axial loads with geometric imperfections. For the latter, local imperfections are usually critical, and two categories of imperfection were studied in detail: an inward axisymmetric imperfection and a local dent imperfection. For the first loading condition, which leads to elephant’s foot buckling, an analytical method was used to derive general equations governing the linear elastic behaviour of a cylindrical shell that has been strengthened with FRP subject to internal pressure and axial compression. It was used to identify optimal application of the FRP. All the later studies were conducted using nonlinear finite element analysis (using the ABAQUS program) to obtain extensive predictions of many conditions causing shell buckling and the strengthening effect of well-placed FRP. In all the cases studied in this thesis, it was shown that a small quantity of FRP composite, applied within a small zone, can provide a significant enhancement of the resistance to buckling failure of a thin metal cylinder. These calculations demonstrate that this new technique is of considerable practical value. However, it is clear that not all the relevant questions have been fully answered, so the author poses appropriate questions and makes suggestions for future work.
35
ABDUL, KARIM MUHAMMAD RAMZAN. "Metal matrix composites reinforced with SiC long fibers and carbon nanomaterials produced by electrodeposition." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2591591.
Full textAbstract:
The research work of this PhD thesis was done on the study, production and characterization of two types of metal matrix composites: 1) fiber reinforced metal matrix composites and, 2) carbon nanomaterials reinforced metal matrix composites.
In fiber reinforced metal matrix composites, a metal or an alloy is reinforced with continuous or discontinuous fibers in order to improve the specific strength and stiffness at high temperatures. For example superalloys are the typical materials for the hot parts of aeronautic engines. They are very important in the aerospace field as they offer high temperature mechanical strength together with a good resistance to oxidation and corrosion. But due to high temperatures involved in the service conditions, buckling of the material may occur. In order to avoid this high temperature buckling phenomena, a reinforcement of the superalloy could be needed to maintain the mechanical properties. For this reason it was thought to investigate the possibility of realizing continuous fibers reinforced metal matrix composites over the superalloys that can further improve the high temperature properties. Due to its simplicity and viability, electrochemical deposition was chosen as the production technique to produce this kind of composite materials. The selected substrate for electrodepositing the nickel matrix composite was nickel based superalloy Inconel-718, and monofilament continuous silicon carbide fibers were chosen as reinforcement.
First of all chemical compatibility was studied between the nickel matrix, superalloy and silicon carbide fibers, both in the uncoated form, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, suggesting the use of a carbon coating over fibers and a buffer layer of nickel to increase the interface quality as well as to avoid unwanted reactions between substrate and silicon carbide fibers. After studying the chemical feasibility of all the related components, electrodeposition of the composites was performed in order to demonstrate the practical feasibility of the process. Then final composites were deposited on the dog-bone shaped specimens of Inconel-718. The produced composites were subjected to mechanical tests in order to evaluate the mechanical properties at room temperature and at high temperatures (400 °C and 600 °C). Evaluation of the results shows improvement in the yield strength of the produced composites with respect to the superalloy alone at room temperature. There is a decrease in the yield strength at high temperatures due to the failure of the interface between the superalloy and the composite layer but it is demonstrated that if a hot pressing treatment is done, then the interface strength is retained at high temperature and thus yield strength values will also increase.
Fracture analysis and EDS analysis were also performed on the fractured surfaces of the samples with the help of field emission scanning electron microscope in order to study the fracture mechanisms involved and the composition of the interface after their testing at high temperatures. The fracture mechanisms in Ni/SiC composite layer was of debonding and pull out type which is typical characteristic of the fiber reinforced composites. The superalloy fractures with ductile behavior at room temperature. At temperatures of 400 °C and 600 °C, the superalloy fails with more ductile character after extensive amount of plastic deformation before its fracture.
Carbon nanomaterials are widely being used to reinforce the metallic materials in order to improve their electrical, thermal, corrosion, wear and friction resistance for particular applications. In this part of the research work, graphene nanoplatelets (GNPs) and graphene oxide (GO) were chosen as nano reinforcements to produce nickel matrix nanocomposites with the intention to evaluate their wear and friction behavior. Graphene nanoplatelets and graphene oxide consist of few layers of graphene and graphene oxide respectively and their layered structure coupled with the small size of these materials can be helpful reducing the wear rate of the composites. Crystallite size, hardness and roughness of the coatings were also studied in order to understand the effect of nano phases on these properties.
Again the production technique employed consists of electrodeposition of the composites over a conducting steel substrate. A lot of work has been done in producing metal matrix composites reinforced with carbon nano fibers, carbon nanotubes and graphene. But graphene nanoplatelets and graphene oxide are not much evaluated for reinforcing the metallic matrices especially with the electrodeposition technique. To produce these types of composites by electrodeposition, a uniform and stable dispersion of the carbon nanomaterials in the nickel deposition baths is necessary. So particular attention was given to this aspect and uniform and stable dispersions were obtained by using a suitable dispersant, chosen after a wide screening, namely poly sodium styrene sulphonate (PSS). The dispersing technique employed the ultrasonication of the deposition bath with the help of an ultrasonic probe. The obtained coatings were strong and well adherent to the steel substrate, and presented rather well dispersed graphene oxide or graphite nanoplatelets, even if some agglomerates were still present in samples obtained from highly concentrated suspensions.
The nanocomposites were characterized in terms of microhardness, crystallite size, roughness and wear and friction behaviors. The composites with GO show very little effect on the microhardness whereas Ni/GNP composites show slight increase in the hardness. The effect on the crystallite size is not significant. Low concentration of the nano phase gives the composites a good smooth surface with less roughness whereas, by increasing the concentration of the carbon nanomaterials, the composites produced presents a rougher surface. Pin-on-disk tests were chosen to evaluate the wear behavior of the composites. The obtained results demonstrated a significant decrease in the wear rate, percent mass loss and volume loss of the composites as compared to the pure nickel one. The worn tracks observations suggest that the nanocomposites were worn by adhesive wear mechanism.
36
Attar, Ahmed. "Le béton renforcé de fibres metalliques, matériau anisotrope et hétérogène : caractérisation et modélisation du comportement en traction uniaxiale." Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0011.
Full textAbstract:
Les résultats des essais d'identification des paramètres de la loi de comportement en traction disponibles pour les bétons renforcés de fibres métalliques, ne peuvent généralement rendre compte de manière satisfaisante des capacités réelles du matériau. On cherche à apprécier la sensibilité des grandeurs caractéristiques de la loi de comportement (la résistance en traction f#t et l'énergie de post-fissuration g#f) aux facteurs relatifs a la constitution du corps d'épreuve et aux conditions expérimentales. En suivant la méthodologie des plans d'expériences qui permet d'adopter une démarche formelle dans la définition des essais et d'apprécier la confiance a accorder aux résultats expérimentaux, on définit un modèle rhéologique pour les réponses ainsi retenues. Huit facteurs ont été pris en compte. Certains aspects macroscopique du comportement, ne peuvent être expliques que par une analyse portée a l'échelle micro. Une attention particulière est consacrée à l'étude de l'hétérogénéité et l'anisotropie du matériau. Les modèles de comportement élaborés, sont introduits dans un code de calcul aux éléments finis qui a permis en mettant a profit la théorie de la fissure distribuée, d'apprécier l'apport des fibres sur le comportement global des poutres en flexion
37
Vogel, Veronika. "Endlosfaserverstärkte Thermoplaste zur Abschirmung elektromagnetischer Strahlung." Universitätsverlag Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A36413.
Full textAbstract:
Durch die Ergänzung von Organoblechen mit gewebten Strukturen aus Metalldrähten können hochbelastbare Bauteile gleichzeitig mit einer abschirmenden Wirkung versehen werden und ermöglichen so Anwendungen wie beispielsweise im Umfeld der Elektromobilität.
Im Rahmen der vorliegenden Arbeit wird ein polypropylen-basierter Schichtverbund aus thermoplastischen Hochleistungsfaserverbunden und Metalldrahtgewebe hinsichtlich seiner Eignung zur Abschirmung elektromagnetischer Wellen für Gehäusestrukturen und seiner Verarbeitbarkeit im Spritzgießen näher analysiert. Die Untersuchungen zeigen den Einfluss von Defekten, wie sie bei der Herstellung realer Bauteile entstehen können, und deren Auswirkung auf die Abschirmwirkung des Bauteils. Darüber hinaus werden mit Vibrations-,Infrarot- und Heißgasschweißen mögliche Fügeverfahren aufgezeigt und hinsichtlich ihrer Abschirmwirkung bewertet, die auch eine elektrische Kontaktierung über die Fügestelle hinweg ermöglichen.:1 Einleitung
2 Grundlagen
3 Experimentelles
4 Analyseverfahren
5 Untersuchungsergebnisse
6 Zusammenfassende Bewertung der Ergebnisse
7 ZusammenfassungBy combining endless glass fiber reinforced thermoplastic semifinished products with embedded metal wire meshes it is possible to produce highly stressable parts, which additionally allow shielding of electromagnetic waves. Therefore these party can be used for electric cars. In this study a multi-layer film, consisting of polypropylene-based organosheets, PPGF30 and metal wire meshes, is analyzed regarding its suitability for shielding against electromagnetic waves and its processability in injection molding. The analysis show the influences defects, which accure during the production of housings, and their impact of the shielding effectiveness. Moreover possible joining technologies, such as infraredwelding, vibrationwelding and ultrasonicwelding, are studied and evaluated whether it’s possible to create a electrically conductive joint.:1 Einleitung 2 Grundlagen 3 Experimentelles 4 Analyseverfahren 5 Untersuchungsergebnisse 6 Zusammenfassende Bewertung der Ergebnisse 7 Zusammenfassung
38
Velthuis, Rudi [Verfasser], and Peter [Akademischer Betreuer] Mitschang. "Induction Welding of Fiber Reinforced Thermoplastic Polymer Composites to Metals / Rudi Velthuis ; Betreuer: Peter Mitschang." Kaiserslautern : Technische Universität Kaiserslautern, 2017. http://d-nb.info/1138630500/34.
Full text
39
Kryze, Jana. "Méthode d'élaboration et propriétés mécaniques de composites duralumin / fibres ou particules céramiques, obtenus par métallurgie des poudres et filage." Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0444.
Full textAbstract:
Nous avons mis au point un procédé de fabrication de composites à matrice métallique, dont nous avons montre l'efficacité pour divers renforts céramiques, fibres de carbone, fibres d'alumine saffil, ou particules de carbure de silicium. Nous avons comparé les comportements en traction monotone de ces composites en fonction du type de renfort. L'utilisation de modèles de calcul du type Mori-Tanaka nous a permis de mieux comprendre l'influence des divers paramètres microstructuraux tels que la fraction volumique ou l'orientation des renforts. Nous avons mis en parallèle les résultats d'essais en traction simple, l'observation au microscope de la structure initiale et de la structure endommagée du composite, et l'observation in-situ de l'évolution de l'endommagement. Un traitement thermomécanique de type T351, calqué sur celui de la matrice, permet de tirer parti à la fois du durcissement structural de la matrice et de l'écrouissage élevé induit par les renforts. Le composite renforce par fibres de carbone présente un allongement à la rupture très faible, que nous avons attribué a une faible résistance de l'interface fibre-matrice. Le composite renforcé par fibres d'alumine présente une interface fibre-matrice forte, grâce à la formation de cristaux de spinelles par réaction de l'alumine avec le magnésium de l'alliage. Ceci semble expliquer son bon allongement à rupture. Ce composite présente, en revanche, une réserve de contrainte quasi nulle après le début de la plasticité, et une contrainte à la rupture inferieure a celle de la matrice. Le composite renforcé par particules de carbure de silicium semble le meilleur compromis pour les applications a température ambiante. Un essai comparatif a 180°C montre cependant qu'en température, la limite d'élasticité du composite a renfort particules de sic chute davantage que celle du composite a renfort fibres de carbone
40
Gagnon, Geneviève. "Cast Al-based metal matrix composites reinforced by alumina short fibers : micromechanical behavior under thermal cycling /." [S.l.] : [s.n.], 1995. http://library.epfl.ch/theses/?nr=1366.
Full text
41
Lobley, Christopher Marcus. "Tape casting as a novel processing route for silicon carbide fibre-reinforced titanium metal matrix composites." Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298249.
Full text
42
Kadam, Ruthvik Dinesh. "Design and Additive Manufacturing of Carbon-Fiber Reinforced Polymer Microlattice with High Stiffness and High Damping." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/103009.
Full textAbstract:
Carbon fiber reinforced polymer (CFRP) composites are known for their high stiffness-to-weight and high strength-to-weight ratios and hence are of great interest in several engineering fields such as aerospace, automotive and defense. However, despite their light weight, high stiffness and high strength, their application in these fields is limited due to their poor energy dissipation and vibration damping capabilities. This thesis presents a two-phase microlattice design to overcome this problem. To realize this design, a novel tape casting integrated multi-material stereolithography system is developed and mechanical properties of samples fabricated using this system are evaluated. The design incorporating a stiff phase (CFRP) and a high loss phase, exhibiting high stiffness as well as high damping, is studied via analytical and experimental approaches. To investigate its damping performance, mechanical properties at small-strain and large-strain regimes are measured through dynamic material analysis (DMA) and quasi-static cyclic compression tests respectively. It is seen that both intrinsic (small-strain) and structural (large-strain) damping in terms of a figure of merit (FOM), E1/3tanδ/ρ, can be enhanced by a small addition of a high loss phase in Reuss configuration. Moreover, it is seen that structural damping is improved at low relative densities due to the presence of elastic buckling during deformation. For design usefulness, tunability maps, displaying FOM in terms of design parameters, are developed by curve fitting of experimental measurements. The microlattice design is also evaluated quantitatively by comparing it with existing families of materials in a stiffness-loss map, which shows that the design is as stiff as commercial CFRP composites and as dissipative as elastomers.Master of Science
43
Molliex, Ludovic. "Approche micromécanique de la résistance en traction de composites à matrice métallique : carbure de silicium/titane et carbure de silicium/aluminium." Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0400.
Full textAbstract:
L’interface fibre-matrice dans les composites à matrice métallique est le siège de réactions chimiques complexes et d'un état de contraintes résiduelles particulier. On se propose de caractériser l'interface fibre-matrice à l'aide de l'essai de fragmentation sur composite monofilamentaire. Cet essai impose de quantifier l'endommagement de la fibre au sein du composite et de calculer les contraintes résiduelles à l'interface. Puis moyennant quelques simplifications, une simulation est développée afin de prévoir la résistance en traction d'un composite multifilamentaire sollicité dans le sens des fibres. Les paramètres utiles a cette modélisation sont le cisaillement interfacial déterminé par l'essai de fragmentation, la distribution de Weibull des résistances de la fibre ainsi que les caractéristiques de la matrice. Après confrontation du modèle avec l'expérience, le bon accord entre les résultats d'essais de traction en température et la simulation, tend à valider les hypothèses sur les micromécanismes intervenant lors d'un essai de traction
44
Almonte, Thania Grisel Rodriguez. "Avaliação da resistência à fratura de prótese parcial fixa provisória confeccionada sobre componentes do tipo UCLA em titânio - efeito de diversos reforços." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/25/25135/tde-11042015-110150/.
Full textAbstract:
As restaurações provisórias no tratamento reabilitador oral são de suma importância. Por isso é preocupante que os materiais utilizados para a execução das mesmas sejam críticos com relação à sua resistência e longevidade, principalmente, quando estas são executadas em tratamentos prolongados e/ou em espaços desdentados extensos. O objetivo deste trabalho foi avaliar em 4 grupos reforçados, compostos por 9 espécimes cada um, a resistência e o modo de fratura, de uma resina acrílica poli(metilmetacrilato) auto-polimerizável (Dencor® - Clássico®, São Paulo, SP, Brasil) utilizada para restaurações provisórias quando reforçada com fibras de vidro (Fibrante® e Interlig® - Angelus®, Londrina, PR, Brasil), fibras de aramida (Kevlar® - Du Pont®, USA) y fio ortodôntico ∅ 0, 7mm. E um grupo controle sem nenhum tipo de reforço, com a mesma quantidade de corpos de prova. A análise dos resultados (ANOVA, p < 0,05), para o teste de resistência, mostrou haver diferença estatística entre os grupos. O teste de Tukey encontrou que os grupos reforçados, aqueles que alcançaram maior média de resistência à fratura foram os que utilizaram a fibra de vidro trançada pré-impregnada com resina composta foto-polimerizável, Interlig® (1083 N); a fibra de vidro unidirecional préimpregnada com dimetacrilato de glicol, Fibrante® (1022 N) e a fibra de poli(aramida) unidirecional sem pré-impregnação, Kevlar® 29, aumentando em 26%, 22% e 17%, respectivamente, esta resistência em relação ao grupo controle (800 N), não havendo diferença estatística significante entre eles. O grupo reforçado com fio de aço com ∅ 0,7 mm (871 N) apareceu em seguida com uma resistência somente 8% maior e semelhante àquela apresentada pelo grupo controle sem reforço. A análise das fraturas concorreu com a elaboração de um novo sistema de classificação dividindo-as em quatro tipos: Ausente, Parcial, Total Não Separada e Total Separada. As fraturas dos espécimes reforçados foram consideradas mais favoráveis ocorrendo, predominantemente, os tipos Ausente e Parcial.Provisional restorations are of ultimate importance in the oral rehabilitation treatment. Thus, clinicians have to bear in mind that materials used for their fabrication are critical due to its longevity and strength, when these are done for longterm therapy and/or large edentulous spaces. The aim of this work was to evaluate the flexural resistance and fracture mode of an auto-cure polymethylmetacrilate resin (Dencor® - Classico® , Sao Paulo, SP, Brasil) used for provisional restorations and reinforced with four materials. Samples were divided in four groups of nine each, as the following: glass fiber (Fibrante® and Interlig® Angelus®, Londrina, PR, Brasil), aramide fibers (Kevlar® Du Pont®, USA), and orthodontic wire ∅ 0,7mm. one group whitout reinforcement served as control. Data was submitted to statistical analysis with one-way ANOVA (p<.05) test. Results showed statistically significant difference among the groups. Tukeys test showed that glass-fiber Interlig® exhibited the greatest value of flexural strength (1083 N); followed by unidirectional glycol dimetacrylate glass-fiber Fibrante® (1022 N) and aramid fiber Kevlar® (966 N). These values represent 26%, 22% and 17% in relation to the control group (800 N), being non statistically significant difference observed among them. The group with ∅ 0,7mm orthodontic wire (871 N) had a resistance only 8% higher and similar of that of control group without reinforcement. Fracture analysis was conducted by the following scale: absence, partial, complete without separation, and complete with separation. Fracture modes observed on reinforced samples were considered more favorable, with types absent and partial seeing more frequently.
45
Friend, Gareth William. "The effect of defects on the mechanical properties of fibre reinforced titanium metal matrix composites under fatigue loading." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5438/.
Full textAbstract:
Applications for titanium metal matrix composites (TiMMCs) are currently being developed by Rolls-Royce plc in gas turbine engine components. With any component manufacturing process there is a probability of defects, as much of the work on TiMMCs to date has been laboratory scale there is as yet no study that looks specifically at the defects that can arise in full scale components. This work set out to investigate the influence of a selection of defects on the fatigue properties of titanium diffusion bonds – an integral joint type in TiMMC components – using conditions derived from TiMMC component stress analysis. The study found that cladding material microstructure and texture greatly affected the fatigue life of the bond. This was characterised by a new technique called Spatially Resolved Acoustic Spectroscopy (SRAS). Airborne debris and residual degreasing agent staining were found to be contaminants the most detrimental to fatigue life and methods of modifying the manufacturing process have been suggested to eliminate them. A number of other methods have been discussed for reducing the sensitivity of the TiMMC components to defects of this type through the control of residual stresses microstructure and texture.
46
Klein, Mario, Frank Podlesak, Kevin Höfer, Holger Seidlitz, Colin Gerstenberger, Peter Mayr, and Lothar Kroll. "Advanced Joining Technologies for Load and Fibre Adjusted FRP-Metal Hybrid Structures." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-177669.
Full textAbstract:
Multi-material-design (MMD) is commonly realized through the combination of thin sheet metal and fibre reinforced plastics (FRP). To maximize the high lightweight potential of the material groups within a multi-material system as good as possible, a material-adapted and particularly fibre adjusted joining technology must be applied. The present paper focuses on two novel joining technologies, the Flow Drill Joining (FDJ) method and Spin-Blind-Riveting (SBR), which were developed for joining heavy-duty metal/composite hybrids. Tests were carried out with material combinations which are significant for lightweight constructions such as aluminium (AA5083) and carbon fibre-reinforced polyamide in sheet thickness of 1.8 mm. The mechanical testing and manufacturing of those multi-material joints was investigated.
47
Cheng, Ming-Yi. "An experimental investigation into tool wear in micro-drilling of aluminium, aluminium/copper metal alloys and carbon fibre reinforced composites." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/14613.
Full textAbstract:
Limitation of conventional machining equipment has become a growing concern over the past two decades due to the demands for greater machining accuracy in today’s manufacturing. The development of micro-machining has therefore attracted significant attention; it signifies the advancement of national economy as well as the level of accuracy manufacturing industry could achieve. While the connection between tool lifespan, cost of machining and throughput is well established, the factor of tool lifespan appears to have more significance since the miniaturization of tool could lead to further performance concerns such as its lack of strength and durability. On the other hand, raising feed rate and spindle rotation speed are the two common approaches for increasing manufacturing throughput. Such approaches tend to cause an increase in the thrust force subjecting the tool to greater stress, which is the main cause of tool wear and even tool failure. Through literature review and preliminary experiments, it was found that spot-drill is often done prior to micro-drilling since it prepares a pre-drill countersunk hole that helps the alignment of tool for subsequent micro-drilling. Although such pre-drill step does improve the micro-drilling operation, the fundamental issue of tool diameter difference still remains. Often the tool used for pre-drill has a bigger diameter than the one for micro-drilling although a significant difference is always something to be avoided. This is because the difference has to be picked up by the tool used for micro-drilling and is directly linked to the wear caused by increased thrust force. In this research the operation of micro-drilling is investigated via mathematical models. Such operation is further broken down into various steps and stages so more detailed description can be achieved. The findings are then further enhanced by simulation based on the 3D model of micro-drilling. Three materials were selected for this research: Al 6061T, Al/Cu metal alloy panel and Carbon fibre reinforced composites. Such a selection enables the study of individual characteristics of different materials and the variation in respective thrust forces. Finally, Conclusions present the summary of the main findings from micro-drilling process analysis based on research and investigation shown in earlier chapters. By combining actual measurements on micro-drilling and mathematic model this research hopefully would improve the understanding towards micro-drilling processes.
48
Said, Assma Musbah. "Friction and lubrication behaviour of metal-on-metal and ZTA ceramic-on-CFR PEEK hip prostheses : friction and lubrication behaviour of metal-on-metal hip resurfacing and ZTA ceramic heads versus CFR PEEK cups with various diameters and clearances using serum-based lubricants with various viscosities." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/6339.
Full textAbstract:
The natural hip joint in healthy people has a very low friction with very little (or no) wear. It works as a dynamically loaded bearing and is subjected to about 1-2 million cycles of loading per year. The applied load is the body weight which is tripled when walking and even higher during other activities such as running and jumping. Unfortunately these joints are not always healthy due to various causes such as fractures or disease leading to severe pain which necessitates joint replacement. Currently, the orthopaedic industries are working towards developing an ideal artificial hip joint with low wear, low friction, good lubrication, better fixation/stability and biocompatibility. Many different designs and materials have been investigated with some promising new implants which can be used depending on patients' individual need (large or small joint), activity and age. In this work, two types of artificial hip joints were tested for friction and lubrication studies: Metal-on-Metal (MoM) Biomet hip resurfacing ReCaps with large diameters (>35-60 mm) and different diametral clearances (~ 60-350 µm), and Zirconia Toughened Alumina (ZTA) heads against carbon-fibre-reinforced poly-ether-ether ketone (CFR PEEK) cups with different diameters (>35-60 mm) and diametral clearances (60-1860 µm). Seven serum-based lubricants with different viscosities were used with and without carboxy methyl cellulose (CMC) additions as gelling agent to increase viscosity depending on the CMC content. The maximum load applied was 2000 N for the stance phase with a minimum load of 100 N for the swing phase. A Pro-Sim friction hip simulator was used to investigate the frictional torque generated between the articulating surfaces so as the friction factor can be calculated. Stribeck analysis was then employed to assess the mode of lubrication. For the metal-on-metal hip resurfacing joints, the friction factors were in the range 0.03-0.151 and those for the ZTA ceramic heads versus CFR PEEK cups were in the range 0.006-0.32. Stribeck analyses showed mainly mixed lubrication for both MoM and ZTA ceramic-on-CFR PEEK joints. The experimental results were in agreement with most of the theoretical calculations suggesting mixed lubricating regimes at low viscosities and moving on to fluid film lubrication at higher viscosities. Joints with larger-diameters, lower clearances and lower surface roughness exhibited a higher lambda ratio suggesting improved lubrication. Viscosity flow curves for the serum-based lubricants having viscosity ≤ 0.00524 Pas showed non-linear relationship between viscosity and shear rate indicating non-Newtonian flow with pseudoplastic or shear-thinning characteristic, i.e. viscosity decreased as shear rate increased up to shear rates of ~ 1000 s⁻¹. However, at shear rates greater than 1000 s⁻¹ Newtonian flow became dominant with almost constant viscosity, i.e. a linear relationship between shear stress and shear rate. On the other hand, viscosity flow curves for the lubricants with viscosity ≥ 0.0128 Pas showed non-Newtonian behaviour up to a shear rate of 3000 s⁻¹ with shear-thinning characteristic.
49
Kenningley, Scott David Peter. "High temperature thermal and mechanical load characterisation of a steel fibre reinforced aluminium metal matrix composite (AlMMC) for automotive diesel pistons." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/high-temperature-thermal-and-mechanical-load-characterisation-of-a-steel-fibre-reinforced-aluminium-metal-matrix-composite-almmc-for-automotive-diesel-pistons(5cc789fc-d64e-4905-bc1c-beb0e3b9c0df).html.
Full textAbstract:
In modern automotive engines, the vast majority of light vehicle diesel (LVD) pistons are made from gravity die cast monolithic AlSi based alloy systems. Presently, the market drivers for reduced emissions, more efficient fuel consumption and increased specific power output are providing cyclic thermal and mechanical fatigue loading above the safe life durability threshold for the current AlSi based alloy systems. Peak temperatures in the diesel piston’s fatigue critical combustion bowl region are presently 420 °C for the AlSi based alloys, which represents a homologous TH value in excess of 0.8. In combination with peak temperatures of 420 C, the pistons are subject to cylinder pressures up to 220 bar, inducing mechanical stress amplitudes 15-20% greater than the allowable component fatigue strength for 1x108 cycles, in some applications. This durability deficit naturally leads to a requirement for new material and process solutions aimed at improving thermal and mechanical fatigue resistance at temperatures in excess of 420 C.One solution to this problem is to locally reinforce the pistons combustion bowl edge with a metal matrix composite (MMC) system. In this study, an aluminium based metal matrix composite (AlMMC) has been investigated and has shown some promise with increases in iso-thermal high cycle (1x 107) fatigue strength of 50 % compared to standard monolithic piston alloys. The AlMMC consists of a premium AlSi based LVD piston alloy matrix reinforced with 0.15 Vf of an interconnected network of 2-4 mm long Fe based fibres. The AlMMC is manufactured by pressure assisted infiltration of a sintered metallic fibre preform with as cast materials having a pore density of 0.2 %. In contrast to the use of ceramic fibre reinforcement systems generally requiring high pressure infiltration techniques, preform infiltration is considered possible with a comparably inexpensive manufacturing route. The Fe based fibre preforms can be infiltrated at lower pressure due to the reactivity between the Fe based fibres and the AlSi based matrix alloy. Unfortunately, this increased reactivity, although an advantage for preform infiltration, can result in (FeAlXX)Si(+X) interfacial reaction products forming between the fibre and matrix at operating temperatures of greater than 440 °C. These interfacial reactions result in a 15-20 m interfacial intermetallic layer after prolonged periods of exposure (>500 hrs), resulting in depleted fibre Vf and void formations on the matrix side of the interface.
50
Fernandes, Andrea. "Utilização de fibras de aço para reforço de concreto em aneis pre-moldados segmentados para revestimento de tuneis." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257680.
Full textAbstract:
Orientador: Newton de Oliveira Pinto JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-08T03:07:34Z (GMT). No. of bitstreams: 1 Fernandes_Andrea_M.pdf: 3789790 bytes, checksum: 3995163d23effcb84c04682718a55ef9 (MD5) Previous issue date: 2005
Resumo: O reforço do concreto através da utilização de fibras de aço vem se mostrando, ao longo dos anos, como alternativa econômica e tecnicamente viável para diversos tipos de aplicações . Sua ampla utilização na indústria da construção mundial, em diversos casos de sucesso, despertou interesse também do segmento tuneleiro moderno. Passou-se a utilizar fibras para reforçar o concreto das aduelas dos anéis montados por tuneladoras (TBM- Tunnel Boring Machines ¿ máquina de escavar túneis) nas principais obras ao redor mundo. Desta forma, após diversos anos sem obras importantes de túneis metroviários no Brasil, a construção da linha 4 (Amarela) do Metrô de São Paulo, utilizará uma destas máquinas de escavar túneis, sendo do tipo EPBM (Earth Pressure Balanced Machine), cujo revestimento será feito com anéis segmentados (aduelas) de concreto. O projeto básico desta obra (década de 60) prevê armação das aduelas de forma tradicional (em desuso) com gaiolas de aço. Em virtude dos benefícios que o reforço com fibras oferece, e ainda, baseando-se no sucesso da experiência mundial, surgiu a necessidade de um estudo no Brasil sobre esta tecnologia. Assim, tomando como base os dados do projeto básico do projeto da linha 4 (cargas, geometrias, etc.), iniciou-se um estudo comparativo do reforço com gaiolas e do reforço com fibras de aço. Este trabalho apresenta algumas etapas deste estudo, procura abordar aspectos relevantes do processo desde a fabricação até a instalação das aduelas no túnel, explica os benefícios possíveis de serem atingidos, resume alguns dos principais motivos que levaram a indústria tuneleira a adotar a tecnologia de reforço com fibras de aço, vantagens e desvantagens
Abstract: The reinforcement of the concrete using steel fibers became possible, through the years, by it¿s economical and technical viability. It¿s wide range of utilization in civil construction, in several success work cases, made the modern tunneling industry realize the necessity of studding it as well. Concrete Segmental Lining Rings placed by TBMs - Tunnel Boring Machines - have been produced with Steel Fiber in the ultimate reference jobs around the world. After several years without of Metro projects in São Paulo Brasil, the already under construction line 4 with total 12,8 km of tunnels, will use one EPBM - Earth Pressure Balanced Machine ¿ witch lining is being considered made by reinforced concrete. The Basic Project (from the 60¿s) primarily considered steel bars as cage reinforcement. To benefit from the steel fiber reinforcement concrete, still, based on successful practical cases world wide, became the necessity to study this technology locally, in Brasil. Thus, taking the basic data from the original Line 4 project (geometry, etc.) a comparative study between steel cages and steel fibers started. This work contents some of the steps from this study and intents to evaluate key aspects from the whole process, since production phase at the segment plant, transport, installation and maintenance of the tunnel. Also explains the basic reasons of migration to the steel fiber reinforcement, including the benefits for the whole tunneling industry and society
Mestrado
Edificações
Mestre em Engenharia Civil