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1
Macdougall, Duncan. "Materials testing for constitutive relations." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360368.
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Eriksson, Alexander. "Bioactivity testing of dental materials." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-382042.
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Ever since Hench et al. first discovered bioactive glass in 1969, extensive interest was created because of the materials ability to chemically bond with living tissue. In this project the bioactivity of three different compositions of the bioactive glass Na2O-CaO-SiO2 have been studied. The compositions of the different glasses were A (25% Na2O, 25% CaO and 50% SiO2), B (22.5% Na2O, 22.5% CaO and 55% SiO2) and C (20% Na2O, 20% CaO and 60% SiO2). Their bioactivity was tested through biomimetic evaluation, in this case by soaking samples of each glass in simulated body fluid (SBF) and phosphate buffered saline (PBS). After soaking, the samples were analyzed with Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Grazing Incidence X-ray Diffraction (GIXRD) and Fourier-Transform Infrared Spectroscopy (FTIR) to analyze if hydroxyapatite formed on the glass surfaces. Both the A and B glass showed bioactivity in SBF and PBS, while the C glass did not. Further work is necessary to determine which of the A and B glass has the highest apatite formability and the reason why the C glass were not bioactive.
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Wright, William Matthew David. "Air-coupled ultrasonic testing of materials." Thesis, University of Warwick, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319811.
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Palamidi, Elisavet. "Hopkinson bar testing of cellular materials." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/hopkinson-bar-testing-of-cellular-materials(2f10af3d-752e-42ab-9270-fff248b2cc84).html.
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Cellular materials are often used as impact/blast attenuators due to their capacity to absorb kinetic energy when compressed to large strains. For such applications, three key material properties are the crushing stress, plateau stress and densification strain. The difficulties associated with obtaining these mechanical properties from dynamic/impact tests are outlined. The results of an experimental investigation of the quasi-static and dynamic mechanical properties of two types of cellular materials are reported.The dynamic tests were carried out using Hopkinson pressure bars. Experimentally determined propagation coefficients are employed to represent both dispersion and attenuation effects as stress waves travel along the bars. Propagation coefficients were determined for 20 mm and 40 mm diameter viscoelastic PMMA pressure bars and for elastic Magnesium pressure bars. The use of the elementary wave theory is shown to give satisfactory results for frequencies of up to approximately 15 kHz, 8 kHz and 30 kHz for the 20 mm and 40 mm diameter PMMA bars and the 23 mm diameter Magnesium bars respectively. The use of low impedance, viscoelastic pressure bars is shown to be preferable for testing low density, low strength materials.The quasi-static and dynamic compressive properties of balsa wood, Rohacell-51WF and Rohacell-110WF foams are investigated along all three principal directions. The dynamic properties were investigated by performing Split Hopkinson Pressure Bar (SHPB) and Direct Impact (DI) tests. In general, the crushing stress, the plateau stress and the densification strain remain constant with increasing strain rate of the SHPB tests. However, a dynamic enhancement of the crushing stress and plateau stress was revealed for balsa wood and Rohacell-51WF. In contrast, the plateau stresses of the Rohacell-110WF specimens are lower for SHPB than quasi-static tests. From the DI tests, it is shown that compaction waves have negligible effect on the stresses during dynamic compaction of along and across the grain balsa wood at impact speeds between approximately 20-100 m/s. Alternatively, the proximal end stresses of both Rohacell-51WF and 110WF foams increase with increasing impact velocity, following the quadratic trend predicted by 'shock theory'. This indicates that compaction waves are important for the case of Rohacell foam, even at low impact velocities.
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Dekany, Justin. "Cryostat System for Spacecraft Materials Testing." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5014.
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The main cause of spacecraft failures is due to the harsh space environment; therefore, rigorous testing of materials used in modern spacecraft is imperative to ensure proper operation during the life span of the mission. Enhancing the capabilities of ground-based test facilities allows for more accurate measurements to be taken as it better simulates the environment to which spacecraft will be exposed. The range of temperature measurements has been significantly extended for an existing space environment simulation test chamber used in the study of electron emission, sample charging and discharge, electrostatic discharge and arcing, electron transport, and luminescence of spacecraft materials. This was accomplished by incorporating a new two-stage, closed-cycle helium cryostat, which has an extended sample temperature range from 450 K, with long-term controlled stability of -7Pa) that can simulate diverse space environments. These existing capabilities include controllable vacuum and ambient neutral gases conditions (< 10-7 to 10-1 Pa), electron fluxes (5 eV to 30 KeV monoenergetic, focused, pulsed sources ranging from 10-4 to 1010 nA-cm-2), ion fluxes (<0.1 to 5keV monoenergetic sources for inert and reactive gases with pulsing capabilities), and photon irradiation (numerous continuous and pulsed monochromatic and broadband IR/VIS/UV [0.5 to 7 eV] sources). The original sample mount accommodates one to four samples of 1 cm to 2.5 cm diameter in a low-temperature carousel, which allows rapid sample exchange and controlled exposure of the individual samples. Multiple additional sample mounts have been added to allow for standalone use for constant voltage measurements, radiation induced and conductivity tests, as well as extended capabilities for electron-induced luminescent measurements to be conducted using various material sample thickness in the original existing space environment simulation test chamber.
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Rosala, Fabrice. "Improvement and Development of Powder Spreadability Testing." Thesis, KTH, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-301259.
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With rising interest in metal additive manufacturing and, specifically, in powder bed fusion processes, it is essential to understand relevant process parameters and the behavior of powders used in such processes. At the time of writing, the flow behavior of powders is in the spotlight whereas little research into the spreadability of a powder is being conducted. While the two characteristics are related, powders that are being spread are subject to different force loads which are not present during the simple flow of a powder. This work develops a testing system capable of qualitatively and quantitatively assessing spreadability in metal powders. Seven gas atomized powders of varying size distributions and four different chemistries supplied by Uddeholms AB were used to examine the efficacy and accuracy of the system. Image analysis of the spread layers was found to be effective in measuring the areas of the powder layers. It was also possible to assess the quality of powder coverage in the layer in terms of defects, which were sensitive to process parameters such as layer thickness and rake speed. From measurements of the mass of powder in each layer, a layer density was calculated and shows greater sensitivity than powder coverage to changes in layer thickness parameters. The spreadability data collected were compared to relevant existing flowability metrics, including some derived from powder rheometry. Two metrics were created to assess how well the rheometry data can predict spreading behavior. Firstly, the change in area coverage as a function of rake speed correlated to an increase in basic flowability energy, both of which became less sensitive to rake speed at higher speeds. Finally, an equation was formulated to assess the gap that forms between the true height of a spread layer and the nominal layer thickness. This gap showed great sensitivity to the cohesion values attained from shear cell tests: highly cohesive powders produced larger spread layer gaps. This work is expected to contribute to moving toward a standardized method to attain a powder characteristic for spreadability.With rising interest in metal additive manufacturing and, specifically, in powder bed fusion processes, it is essential to understand relevant process parameters and the behavior of powders used in such processes. At the time of writing, the flow behavior of powders is in the spotlight whereas little research into the spreadability of a powder is being conducted. While the two characteristics are related, powders that are being spread are subject to different force loads which are not present during the simple flow of a powder. This work develops a testing system capable of qualitatively and quantitatively assessing spreadability in metal powders. Seven gas atomized powders of varying size distributions and four different chemistries supplied by Uddeholms AB were used to examine the efficacy and accuracy of the system. Image analysis of the spread layers was found to be effective in measuring the areas of the powder layers. It was also possible to assess the quality of powder coverage in the layer in terms of defects, which were sensitive to process parameters such as layer thickness and rake speed. From measurements of the mass of powder in each layer, a layer density was calculated and shows greater sensitivity than powder coverage to changes in layer thickness parameters. The spreadability data collected were compared to relevant existing flowability metrics, including some derived from powder rheometry. Two metrics were created to assess how well the rheometry data can predict spreading behavior. Firstly, the change in area coverage as a function of rake speed correlated to an increase in basic flowability energy, both of which became less sensitive to rake speed at higher speeds. Finally, an equation was formulated to assess the gap that forms between the true height of a spread layer and the nominal layer thickness. This gap showed great sensitivity to the cohesion values attained from shear cell tests: highly cohesive powders produced larger spread layer gaps. This work is expected to contribute to moving toward a standardized method to attain a powder characteristic for spreadability.Med ett ökande intresse för additiv tillverkning av metaller i allmänhet, och pulverbäddsprocesser i synnerhet, är det viktigt att förstå relevanta processparametrar och beteendet av pulver som används i sådana processer. I skrivande stund är flytbarheten i fokus, medan väldigt lite forskning görs på spridbarheten. Dessa två egenskaper är relaterade, men pulver som sprids utsätts för andra krafter vilka inte återfinns i simpla flytbarhetstester. I detta arbete utvecklas ett testsystem som är kapabelt till att undersöka spridbarheten kvalitativt och kvantitativt. Sju gasatomiserade pulver som tillhandahålles av Uddeholms AB, med varierande storleksfördelningar och fyra olika sammansättningar användes för att undersöka effektiviteten och noggrannheten av systemet. Bildanalys av de utspridda pulverlagren visade sig vara effektivt för att mäta arean av lagren. Det var också möjligt att undersöka kvalitén på pulvertäckningen med avseende på defekter, som visade sig vara känsliga för processparametrar så som lagertjocklek och rake-hastigheten. Från mätningarna av pulvermassan från varje lager kunde en lagerdensitet räknas ut, och denna visar större känslighet med avseende på processparametrar än pulvertäckningen. Spridningsdatan jämfördes med relevanta flytbarhetsmätningar, inklusive reometrimätningar av pulver. Två mätetal användes för att undersöka hur väl reometri kan användas för att förutse spridbarheten. Först användes ändringen i täckning som en funktion av rake-hastigheten korrelerat till ökningen av grundläggande flytbarhetsenergi, där båda parametrarna blev mindre känsliga vid högre rake-hastigheter. Sedan formulerades en ekvation för att redogöra för glappet mellan den verkliga höjden av ett pulverlager och den nominella lagertjockleken. Detta glapp visade stor känslighet för koherensen som mättes med hjälp av skjuvcellstest: koherenta pulver gav större glapp i spridlagren. Detta arbete förväntas bidra till utvecklingen av en standardiserad metod att undersöka spridbarhet hos pulver.
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Seward, Colin Robert. "Rain erosion testing of infrared window materials." Thesis, University of Cambridge, 1992. https://www.repository.cam.ac.uk/handle/1810/251469.
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Hinton, Christopher Eric. "Control of servo-hydraulic materials-testing machines." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282326.
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Stone, Robert Michael 1957. "Shear modulii for cellular foam materials." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277020.
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The use of cellular foam as a core material in light-weight structural applications is of considerable interest. However, advances in this technology have been limited due to the lack of information concerning the macroscopic material behavior of cellular foams. Of particular interest in the design of composite structures is the shear modulus, G, of the core material, which must be established with a high degree of accuracy. Current ASTM test methods for shear modulus determination were researched and found inadequate for testing cellular foam materials. The difficulty in testing foam and the inaccuracies associated with the standard test methods established the need for the development of a test method for these materials. The test method (test fixture and test procedure) developed for cellular foam materials is presented. The design of the test fixture and the finite element analysis performed to determine fixture accuracy are discussed in detail. Additionally, the test procedure is presented, as well as the results for the 32 tests performed.
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Abenoja, Christine Knox. "Friction produced by esthetic brackets with varying ligation." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/abenoja.pdf.
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Hooke, David A. "Design and evaluation of test apparatuses and methods for extension-twist coupled laminates." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12252.
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Round, Robert. "Evaluation of reaction kinetics and material properties of cementitious ceramic materials using ultrasonic velocity and attenuation measurements." Thesis, Brunel University, 1996. http://bura.brunel.ac.uk/handle/2438/6512.
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Ultrasonic velocity and attenuation measurements have been used to characterise a range of phosphate bonded, alumina filled, magnesia ceramics and other ceramic materials... Measurements were made over a range of frequency from 50kHz - 1 OM Hz, using a variety of commercial probes and equipment, and a variety of techniques. An ultrasonic double-probe method was used to monitor the setting process of the cementitious ceramics using commercial 2.25MHz and 2MHz transducers, for compressional and shear wave modes, respectively, in samples with alumina content in the range of 0 - 60 wt 0/0. The elastic properties of the material were determined from ultrasonic velocity measurements and were found to be dependent upon the filler volume fraction. The measured elastic moduli were found to Increase as porosity decreased, and this effect might possibly be used to estimate porosity. The composition dependence of the elastic moduli is compared with the Hashin and Shtrikman theoretical bounds for the elastic moduli of two-phase materials. All data lie between these bounds, suggesting that the alumina particles were well dispersed and well bonded to the matrix. However, the fact that the data are slightly above the lower bound suggested that the particles are not spherical, and this, together with other evidence obtained from an analysis of reaction rates, indicates the predominence of plate-like gram structures.
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Jordan, Jeff. "Composites at micro- and nano-scale and a new approach to the problem of a concentrated force on a half-plane." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16431.
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Fragachan, Jose M. "Accelerated testing methodology for evaluating pavement patching materials." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050407-140250/.
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Rehman, Shafiq-ur. "Laboratory testing of envelope materials for pipe drains." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23419.
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Soils which were known to have caused sedimentation problems in drain pipes were used in the investigations. Different envelope combinations such as soil-fabric, soil-gravel and soil-sand-fabric were evaluated. Nine 100 mm diameter, 250 mm high permeameters were used to determine the functioning of envelope materials and to improve the criteria for testing of envelope materials. To obtain a clear indication of success/failure of an envelope, a wide range of hydraulic gradients and different thicknesses of soils and envelopes were used. The most effective thicknesses were, 5 cm of soil with fabrics and 2.5 cm of soil plus 7.5 cm of gravel for gravel envelopes.All the fabrics were successful in retaining the soil particles. No clogging was observed and higher flow rates were measured in fabrics having 2 to 3 mm thicknesses with openings O$ sb{95}$ finer than 100 $ mu$m.
SCS criteria (1988) with the following modifications: $ rm D sb{100}0.3$ mm for gravel; and $ rm D sb{100}<9.5$ mm for crushed rock mixed with sand are suggested. The performance of envelopes meeting these criteria were successful.
The laboratory tests show that the use of a fabric with river sand as an envelope has a very good potential for successful field operation. There was no laboratory evidence to reject the functioning of this concept.
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Schulze, Michael. "Non-destructive testing and evaluation of magnetostrictive materials." Thesis, University of Hull, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306801.
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Theberge, Ryan C. "Comparison and Testing of Various Noise Wall Materials." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1399372564.
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Quirke, SJ. "Abrasive wear testing of steels in soil." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/21798.
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Bibliography: pages 133-136.A survey has been made of the quality and type of materials used for tillage tools in South Africa. Conclusions have been drawn regarding the inadequacy of the manufacturing processes used and the resultant quality of the tool material. A rig has been designed for the abrasion testing of materials in soil. The reproducibility of the method has been shown to be high and an evaluation has been made of the relative wear resistance of a series of ·heat treated steels. A medium carbon boron steel has been shown to have great promise as a tillage tool material because of its high wear resistance and toughness. The deformed surface layers and the mechanisms of wear of steels subjected to field and laboratory abrasive testing has been examined. The removal of material through predominantly ploughing or cutting mechanisms has been shown to be dependent on the heat treatment and composition of the steels together with the nature of the abrasive. White surface layers have been observed to form on medium and high carbon steels subjected to soil abrasion. Suggestions have been advanced for their formation. Attempts have been made to assess the transferability of data between field and laboratory testing.
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Tudela, Mark A. "Impact response of a laminated beam on an elastic foundation." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17880.
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Carney, Alison Fox. "The effect of microstructure on the mechanical properties of a 30% titanium diboride/70% alumina composite." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19994.
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Karim, Md Rezaul. "Transient response of laminated composites with subsurface cracks." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184541.
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The dynamic response of subsurface cracks in fiber reinforced composites is analytically studied. The response of layered half-space and three-layered plate with two interface cracks excited by a plane SH-wave and line load respectively are studied by formulating the problem as integral equations in the frequency domain. The governing equations along with boundary, regularity and continuity conditions across the interface are reduced to a coupled set of singular integral equations by using Betti's reciprocal theorem along with the Green's functions. In addition, the transient response of an orthotropic half-space with a subsurface crack subjected to inplane line load at an arbitrary angle is analyzed. Two new Green's functions for the uncracked medium are developed and used along with the representation theorem to derive the scattered field. Satisfaction of the traction free condition at the crack surfaces gives rise to a system of singular integral equations. Singular integrals involved in the analysis are computed numerically by removing the poles. Part of the integrals containing the poles are then obtained analytically by using residue theorem. The solution of singular integral equations are obtained by expanding the unknown crack opening displacements (COD) in terms of a complete set of Chebychev polynomials. The problem is first solved in the frequency domain, the time histories are then obtained numerically by inverting the spectra via Fast Fourier Transform (FFT) routine. Numerical results are presented for isotropic and anisotropic materials for several different crack geometries. The results show significant influence of crack geometries and material properties on the COD and surface response of composites.
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Lima, Leandro Soares de. "A influência das variáveis de processamento e de diferentes tipos de nanocargas nas propriedades dos compósitos de polipropileno." reponame:Repositório Institucional da UCS, 2015. https://repositorio.ucs.br/handle/11338/980.
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Neste trabalho foi realizado uma avaliação das propriedades térmicas e mecânicas dos compósitos de PP/PP-g-AM com 5% e 10% m/m das nanocargas MMT-Na+, MMT-15A, MMT-30B, CaCO3 e CaCO3-AE, preparados em extrusora de dupla rosca co-rotante com configuração de L/D 32 para elencar três nanocargas com melhor desempenho nestas propriedades. Posteriormente foram processados compósitos de PP/PP-g-AM com 10% m/m das nanocargas MMT-Na+, MMT-15A e CaCO3 com a configuração de L/D 46 processadas uma e três vezes para avaliar a influência do processamento nas propriedades mecânicas, térmicas, morfológicas, reológicas e termomecânicas. Nos compósitos de PP com nanocargas preparados com L/D 32, os resultados demonstraram que a adição do agente compatibilizante PP-g-AM provoca alterações nas propriedades mecânicas, indicando que os compósitos de PP compatibilizados apresentaram resultados superiores nestas propriedades em relação aos compósitos de PP não compatibilizados. Nos compósitos de PP com as nanocargas MMT-Na+, MMT-15A e o CaCO3 preparados na configuração L/D 32 apresentaram os resultados mais significativos nas análises das propriedades mecânicas e térmicas quando incorporadas em 10% m/m ao PP/PP-g-AM, sendo utilizadas para análise da variação das condições de processamento. Posteriormente foi realizado o estudo do efeito do tipo de configuração da rosca (L/D 46) e de nanocarga nos compósitos de PP/PP-g-AM. Estes compósitos foram caracterizados pelas suas propriedades mecânicas, propriedades térmicas, morfologia, reologicas e termomecânicas. A análise das propriedades mecânicas dos compósitos processados com a configuração L/D 46 uma e três vezes apresentou uma redução nas propriedades mecânicas em comparação com os compósitos processados com configuração L/D 32, ficando com valores próximos ao do PP puro. Este resultado indicou que a variação da configuração L/D no processamento proporcionou a degradação da matriz polimérica, evidenciada nos ensaios de reologia, onde houve um aumento da fluidez dos compósitos e uma redução na viscosidade complexa. As análises de MET mostraram que a argila MMT-15A incorporada de 10% m/m ao PP/PP-g-AM apresentou formação de tactóides intercalados e fase esfoliada no processamento com L/D 32. A análise das propriedades discutidas neste trabalho indicou que a argila MMT-15A apresenta a melhor adesão e dispersão na matriz de polipropileno.Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-08-12T17:55:06Z No. of bitstreams: 1 Dissertacao Leandro Soares de Lima.pdf: 3194982 bytes, checksum: 3979198068c0c31fd2c896803cf04888 (MD5)
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In this work an evaluation of the thermal and mechanical properties of PP/PP-g-MA composites with 5 and 10 wt% of MMT-Na+, MMT-15A, MMT-30B, CaCO3 and CaCO3-AE nanofillers was performed. Composites were prepared in a co-rotating, double-screw extruder configured at L/D ratio 32 to specify three nanofillers of best performance. Thereafter PP/PP-g-MA composites with 10 wt% of MMT-Na +, MMT-15A and CaCO3 nanofillers at L/D ratio 46 were processed one and three times in order to evaluate the influence of processing on the mechanical, thermal, morphological, rheological and thermo- mechanical properties. For PP nanocomposites with nanofillers prepared at L/D ratio 32, results demonstrate that the addition of the compatibilizing agent PP-g-MA changes the mechanical properties, indicating that for these properties, the results obtained for the compatibilized PP composites are improved in relation to those obtained for the non-compatibilized samples. PP composites with MMT-Na+, MMT-15A and CaCO3 nanofillers prepared at L/D ratio 32 configuration had the most relevant results obtained for mechanical and thermal properties when these nanofillers were incorporated in the amount of 10% m/m to PP/PP-g-MA, so they were used in the analysis of the variation of the processing conditions. The effect of the screw configuration L/D ratio 46 and of nanofiller in PP/PP-g-MA composites was also studied. These composites were characterized by their mechanical, thermal, morphological, rheological and thermo-mechanical properties. Analysis of the mechanical properties of the composites processed at L/D 46 ratio one and three times showed to reduced values when compared to the composites processed at the configuration L/D 32 the figures being close to those of neat PP. These data reveals that by varying the L/D ratio configuration during processing the polymer matrix is degraded, as evidenced by rheology tests, a flow increase and reduction in complex viscosity being observed in the composites. TEM analyses have shown that 10 wt% MMT-15A clay incorporated to PP/PP-g-MA formed intercalated tactoids and exfoliated phase during processing at L/D ratio 32. Analysis of the properties discussed in this work indicated that MMT-15A clay has the best adhesion and dispersion in the polypropylene matrix.
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Imbert, de Smirnoff Severine. "Nondestructive Flaw Characterization in a Unidirectional Composite Plate." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/ImbertdeSmirnoffS2002.pdf.
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Elmansy, N. M. "Deformation of bituminous highway pavement materials." Thesis, University of Bradford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373221.
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In, Chi-Won. "Defect characterization in heterogeneous civil materials using ultrasound." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47545.
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Asphalt and Portland cement concrete constitutes a significant portion of the total infrastructure all over the world. It has been reported that much of this concrete infrastructure is now approaching or has already passed its original design life. Thus it is critical to be able to quantitatively assess the condition of these concrete components. In order to rehabilitate or repair the civil infrastructure, nondestructive evaluation (NDE) techniques have been of great interest for infrastructure management agencies. However concrete components present several specific NDE challenges that must be addressed. . Concrete naturally exhibits large scale heterogeneous microstructure with a great deal of local material property variability, For this reasons, many conventional NDE techniques that work well for steel and other homogeneous materials cannot be applied to concrete; concrete is unable to transmit high frequencies, as the heterogeneity of the concrete causes signals of smaller wavelengths or wavelengths equal to the nominal aggregate size to be scattered and severely attenuated. Nevertheless, progress has been made towards accurate and reliable in-place NDE of concrete structures and materials, for example impact echo, ultrasonic pulse velocity method, and the ultrasonic wave transmission method. However, the detection of smaller sized defects or remote defects that are located away from the testing location still pose problems. In addition, the large size and potential limited access conditions of civil structures raise additional challenges. To overcome the limitations of current NDE techniques for concrete, this research considers two different types of ultrasonic waves (coherent and incoherent wave) to quantitatively characterize and monitor defects in heterogeneous concrete materials. The global objective of this research is to determine the feasibility and applicability of using these ultrasonic waves as a global, rapid, reliable, and non-biased technique for the routine screening of defects or monitoring of concrete structures and materials. Three different problems are considered: 1) characterization of segregation in asphaltic concrete, 2) crack depth determination in pier cap of concrete bridge structure, and 3) monitoring of self-healing process in cement-based concrete.
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Thurairajah, Aravinthan. "Unbound materials resilient modulus testing for Truckee Meadows area." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446459.
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Roberts, Matthew Robert. "High-throughput fabrication and testing of lithium battery materials." Thesis, University of Southampton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494756.
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Gudlavalleti, Sauri 1978. "Mechanical testing of solid materials at the micro-scale." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29741.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 145-149).
Successful design and fabrication of structures and systems at the micro-scale requires a sound theoretical understanding and reliable experimental data on the mechanical behavior of materials at that scale. Generation of experimental data requires accurate, robust, reliable, versatile and yet simple micro-scale mechanical testing devices. This thesis describes the design, development and applications of materials testing technologies at the micro-scale. Using the rectilinear travel characteristics of compound flexures, two novel testing machines have been designed and built to conduct tension, bending and indentation tests in the force regime of 10 pN - 35 N and displacement regime of 20 nm - 6 mm. These machines have been used in measuring the mechanical properties of free-standing gold thin films, rolled metallic foils, elastomeric fibers and other materials. Numerical simulations of the mechanical behavior of gold thin films and rolled copper foils have been conducted and compared with experimental results. Microstructural investigations into deformation mechanisms of the free-standing gold thin films have also been conducted.
by Sauri Gudlavalleti.
S.M.
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Giudici, Henri. "Frost heave testing of norwegian materials for road infrastructure." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7590/.
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In areas of seasonal frost, frost susceptibility composed by frost heaving during the winter and thaw softening during the spring is one of the most dangerous phenomenon for transportation, road and railway infrastructure. Therefore, the need for frost protection layer becomes imperative. The purpose of frost protection layer is to prevent frost from penetrating down through the pavement and into the sub-soils. Frost susceptible soils under the road can be cause damages on the roads or other structures due to frost heave or reduced capacity characteristics thaw period.
"Frost heave" is the term given to the upwards displacement of the ground surface caused by the formation of ice within soils or aggregates (Rempel et al., 2004). Nowadays in Scandinavia the most common material used in frost protection layer in the pavement structure of roads and in the ballast of the railway tracks are coarse-grain crushed rocks aggregates. Based on the capillary rise, the mechanics of frost heave phenomenon is based on the interaction between aggregates and water, as suggested by Konrad and Lemieux in 2005 that said that the fraction of material below the 0.063 mm sieve for coarse-grained soils must be controlled so as to reduce the sensitivity to frost heave. The study conducted in this thesis project is divided in two parts:
- the analysis of the coarse grained aggregates used in frost protection layer in Norway;
- the analysis of the frost heave phenomenon in the laboratory under known boundary conditions, through the use of the most widely used method, the frost heave test, in” closed system” (without access of water).
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Sanderson, Terry. "Thermoelastic modeling of laser generated ultrasound for nondestructive materials testing." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18978.
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Palomino, Angelica Maria. "Fabric formation and control in fine-grained materials." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-06072004-131309/unrestricted/palomino%5Fangelica%5Fm%5F200405%5Fphd.pdf.
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Thesis (Ph. D.)--School of Civil and Environmental Engineering, Georgia Institute of Technology, 2004. Directed by J. Carlos Santamarina.Vita. Includes bibliographical references (leaves 183-192).
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Camposilvan, Erik. "Surface stability and small-scale testing of zirconia." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/311627.
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Tetragonal polycrystalline zirconia stabilized with 3 mol% of yttria (3Y-TZP) is a biocompatible ceramic showing superior mechanical properties, which are partly the consequence of phase transformation: the tetragonal metastable phase can transform, with a net volume increase, to the stable monoclinic phase by a martensitic transformation. The transformation can be activated either mechanically by the application of high stresses, or chemically by the diffusion of water species, when the material is exposed to humid environment and moderate temperatures. In the first case, the local transformation at the crack tip under tension hinders their propagation, producing a phenomenon known as transformation toughening, which allows the design of damage-tolerant ceramics. On the other hand, the spontaneous and progressive surface transformation in presence of humidity represents an aging phenomenon known as low-temperature degradation (LTD), hydrothermal degradation or aging. Affecting a surface layer of only few micrometers, this phenomenon is accompanied by a substantial impairment of the surface integrity, representing a serious issue for the use of 3Y-TZP in load-bearing biomedical applications. It was shown in orthopedics that zirconia femoral heads used in arthroplasty may be vulnerable to LTD, leading in some cases to premature failures. Likewise, some recent publications devoted to dental zirconia have highlighted that it is susceptible to LTD if exact processing conditions are not followed.
The first subject of the thesis is the study of reliable solutions to avoid hydrothermal degradation of 3Y-TZP. Two novel methods are proposed, which allow a strong enhancement of the aging resistance through limited changes in the processing. These methods are based on co-doping the material from the surface with CeO2 by two different approaches. One includes infiltration of CeO2 precursors in the pre-sintered porous material. During thermal decomposition and sintering, CeO2 is trapped into the pores and diffused into 3Y-TZP, obtaining a functionally-graded material with decreasing CeO2 content from the surface to the bulk. The co-doping profile has been optimized by studying the pre-sintering, infiltration and sintering parameters in order to avoid a drop in the mechanical properties generally found in CeO2-doped zirconia. The second approach is applied to the dense material, where surface roughness has been created for adhesion or osseointegration purposes. After pressure infiltration of CeO2 precursors into the surface defects and pores created during the roughening process, a few-micrometers thick co-doped layer is obtained with a diffusion treatment. This helps sealing the surface defects and avoids hydrothermal degradation, without affecting the color or the mechanical properties, being so directly applicable in the manufacturing of dental crowns, abutments and dentures.
The second subject focuses on small-scale testing of zirconia near-surface regions. The existence of extrinsic size effects on the mechanical properties has been investigated, and the mechanical response of the degraded and non-degraded state has been compared in bending and compression. By testing micropillars and micro-cantilevers milled with focused ion beam (FIB), higher strength and strain at failure have been recorded with respect to the bulk state, as a result of transformation-induced plasticity and the absence of processing defects. No size effect has been found in terms of strength among small-scale samples, whereas the "yield" stress for phase transformation is lower for smaller samples. Hydrothermal degradation produces a microcrack network which controls the behavior and strongly impairs the mechanical properties of small-scale samples milled inside the degraded layer. In bending, a different response in terms of strength and stiffness has been measured depending on sample orientation, proving that that the induced damage is anisotropic.El óxido de zirconio tetragonal estabilizado con 3 mol% de itria (3Y-TZP, o simplemente circona) es un material cerámico biocompatible de altas prestaciones mecánicas. Esto se debe, en parte, a la transformación de la fase tetragonal metastable en la fase monoclínica, acompañada por un incremento de volumen. Esta transformación martensítica se puede activar mecánicamente mediante esfuerzos elevados, o bien químicamente por la difusión de especies acuosas, cuando el material está expuesto a ambiente húmedo y temperaturas moderadas. En el primer caso, la transformación local que ocurre en la punta de las grietas bajo tensión permite el diseño de cerámicos tolerantes al daño (aumento de tenacidad por transformación). Por otra parte, la transformación espontánea y progresiva de la superficie en presencia de humedad es un fenómeno conocido como degradación hidrotérmica o envejecimiento. Aunque afecta una capa superficial de unas pocas micras, el envejecimiento reduce de manera substancial la integridad superficial, representando un problema para aplicaciones biomédicas estructurales. Se ha demostrado en ortopedia que las cabezas femorales de 3Y-TZP pueden ser vulnerables a la degradación hidrotérmica, llegando en algunos casos al fallo de la prótesis. En años recientes, la circona está siendo empleada en el campo dental, donde se ha visto que puede sufrir envejecimiento. La primera parte de esta tesis trata de desarrollar soluciones viables para evitar el envejecimiento. Se han propuesto dos nuevos métodos, que con pequeños cambios en el procesado permiten una fuerte mejora en la resistencia a la degradación. Estos están basados en el co-dopaje del material desde la superficie con CeO2 con dos estrategias diferentes. Una incluye la infiltración de precursores de CeO2 en el material presinterizado, que es poroso. Durante la descomposición térmica y el sinterizado, parte del CeO2 se queda atrapado en los poros y difunde en el retículo de la TZP, obteniendo un gradiente de composición con contenidos decrecientes de CeO2 desde la superficie hacia el interior. Se ha optimizado el gradiente estudiando los parámetros de pre-sinterizado, infiltración y sinterizado para evitar una posible caída en las propiedades mecánicas que se encuentra generalmente en la circona estabilizada con CeO2. La segunda estrategia se aplica en materiales densos donde se haya inducido rugosidad superficial para favorecer la adhesión o la osteointegración. Después de infiltrar a presión los precursores de CeO2 en los defectos y poros presentes en la superficie, se ha creado una capa co-dopada de pocas micras de espesor con un tratamiento de difusión. Esto contribuye en eliminar los defectos superficiales y evitar el envejecimiento sin modificar el color o las propiedades mecánicas, siendo directamente aplicable al procesado de coronas dentales, pilares y dentaduras postizas. La segunda parte de la tesis está enfocada en estudiar las las propiedades mecánicas de regiones superficiales de 3YTZP mediante ensayos de muestras microscópicas, para evaluar la presencia de efectos de escala y comparar la respuesta del material antes y después del envejecimiento. En micropilares y microvigas mecanizados con haz de iones focalizados se han medido resistencias y deformaciones de rotura mucho más altas que en probetas macroscópicas, gracias a la plasticidad inducida por deformación y a la ausencia de defectos de procesado. No se han encontrado efectos de escala entre las muestras microscópicas en cuanto a la resistencia, mientras que el límite de elasticidad donde aparece la transformación de fase es menor para muestras más pequeñas. El envejecimiento produce una red de microgrietas que controla el comportamiento y afecta las propiedades mecánicas de muestras microscópicas mecanizadas dentro la capa degradada. En flexión se ha medido una respuesta diferente en términos de resistencia y rigidez según la orientación, demostrando que el daño producido es anisotrópico
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May, Katelun. "Small Scale Tensile Testing of Titanium Alloys." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282099780.
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Abdulla, Ali Abdulhussein 1967. "Testing and constitutive modeling of cemented soils." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186066.
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The behavior of cemented sands is examined experimentally and theoretically in this study. The first segment of the investigation involves an extensive laboratory program to examine the effects of slenderness ratio, effects of cementation, and effects of confining pressure on the stress-strain curves of cemented sands. Results show that specimens with slenderness ratio of 1.5 or greater exhibit lower strength, higher dilatation rates, and relatively brittle behavior when compared to samples with slenderness ratio of 1. Furthermore, cemented sands have an essentially straight line Mohr-Coulomb failure envelope, whose cohesion intercept increases with the degree of cementation of the soil. The effective friction angles measured for cemented sands with various cementation levels are in the same ranges as the effective friction angle evaluated for uncemented sands. Moreover, failure modes of the material varies from brittle to ductile depending upon the level of cementation and the degree of confinement. In general, as cementation increases, cemented sand exhibits a brittle failure behavior; while increasing the confining pressure causes a ductile failure response. The second portion of the project includes development of a constitutive model for cemented sands. Cemented sand is viewed as a multi-phase material comprising three phases: sand, cement, and pore water. The elastoplastic behavior of cemented sands is the consequence of the behavior of the individual phases plus the interaction of the phases. The individual phases (sand and cement) are modeled using the theory of plasticity. Mixtures theory is used to assemble the individual phases to simulate the overall behavior of cemented sands. The gradual damage of the internal structure of cemented sands is also incorporated within the model. The agreement between experimental data and model predictions is very good. In summary, mixtures theory using simple plasticity models for the individual phases is capable of capturing the complex behavior of cemented sands.
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Bowsher, John G. "Accelerated wear testing methodologies for total hip replacements." Thesis, Queen Mary, University of London, 2001. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1513.
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Over the last three decades tribological studies of polyethylene total hip replacements have been undertaken using a simplified model of normal walking. As hip prostheses are being implanted in younger and more active patients, coupled with the increased wear resistance of crosslinked polyethylene, such in vitro approximations in patient activity are limiting. Therefore an alternative wear testing methodology for total hip replacements has been proposed, measuring the influences of fast walking, stumbling and simulated jogging sequences, all at varying cycle speeds with both smooth and roughened femoral components. This hip simulator study has shown that the influence of femoral roughness on the wear of crosslinked polyethylene becomes significantly greater under increased patient activity, demonstrating that roughness may be a more influential factor than previously ascribed. The combined effects of high roughness (Re of 0.38 μm), high joint forces (4.5 kN max) and high sliding speed (1.75 Hz) generated excessive crosslinked polyethylene wear and high joint torque, with wear rates exceeding 3000 mm3/106 cycles (k = 50 x10-6 mm3/N m). Thus for more active patients, implant survival can be greatly increased by using harder and more damage resistant femoral heads compared to CoCrMo. Under smooth conditions however, the overall influence of a significant increase in patient activity showed a much weaker effect. It was found that with smooth heads and non-constraining socket fixtures, the occurrence of excessive stumbling at 1 Hz (5 kN max) had a negligible effect on the wear of crosslinked polyethylene, whilst simulated jogging at 1.75 Hz (4.5 kN max) only showed a median increase in wear volume of 40 % compared to normal walking. Fast walking produced the largest wear rate (53 mm3/106 cycles), and was consistently greater than for simulated jogging. Ignoring fixation and other factors, these results suggest that whilst preserving polished surfaces, short periods of increased patient activity, for example, aerobics, tennis etc, will not greatly reduce the survival of crosslinked polyethylene/metal implants. Sliding speed and the degree of socket clamping were shown to be the most influential factors under smooth conditions, with the results showing no significant differences in wear rate when testing in varying quantities of bovine serum, or using an inverted or physiological specimen orientation.
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Shipway, Philip Howard. "Erosive wear of brittle materials and its laboratory simulation." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282026.
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Yao, Zhao-Cheng. "Reliability of structures with load history-dependent strength and an application to wood members." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26753.
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Because of an interaction between the load history and the material's properties a reduction in the serviceability of safety of a structure may be seen as the result of a random process of damage accumulation with time.
A damage model is proposed and verified to deal with this type of problem in general, and specifically with duration-of-load effects in timber structures.
Through comparisons with and discussion of other damage accumulation models, the proposed model is found to be both suitable to represent experimental results and relatively easy to use.
A reliability analysis for a single structural member with a service life of 30 years is studied for different snow loading conditions of three Canadian cities,using the damage model in combination with Rackwitz-Fissler's algorithm.
A simplified analysis method is proposed and compared with a large-scale Monte-Carlo simulation. The results of the reliability analysis are found to be satisfactory.
Finally, the implementation of the reliability analysis in a simple design guideline for load duration effects is discussed.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Craciun, Ovidiu Engineering & Information Technology Australian Defence Force Academy UNSW. "Matric suction response of unbound granular base materials subject to cyclic loading." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/43927.
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The emergence of analytically-based pavement design has encouraged investigations toward a better understanding of the behaviour of pavement layers under cyclic loading. Unbound granular base (UGB) materials are commonly placed as base course layers in the design of pavement foundations. Due to their nature and geometry they are unsaturated geo-materials and therefore, it is desirable to study their behaviour using the framework of unsaturated soil mechanics. Current literature reflects very limited achievements in this direction. This thesis presents the development of a cyclic triaxial testing system and associated testing methodology that meets the challenges of testing an UGB material as an unsaturated soil. The testing system enables the initialisation of a specimen to target matric suction and facilitates direct measurement of its evolution under cyclic loading. In conjunction with the use of accurate on-specimens strain measurement transducers, ???clean??? strain and matric suction cyclic responses are obtained. Two types of cyclic triaxial testing are investigated: with constant cell pressure (i.e., CSeries testing) and with varying (cyclic) cell pressure where both axial and radial stress components are simultaneously (and in phase) pulsed (i.e., V-Series testing). Different initial matric suctions, si will be imposed in the testing program and the influence of si on material behaviour is analysed. This is investigated in a similar manner for C- and V-Series testing. The influence of si appears to be significant for both cyclic and permanent strain responses. A strong stress path dependency is found to characterise the behaviour of the UGB material. Under a wide range of cyclic deviator stress magnitudes, permanent strain response is found to correlate with that of matric suction response. Both appear to indicate better the relative performance of a UGB material than the response of resilient modulus. Another particular aspect investigated is the influence of additional fines on the behaviour of the UGB material. To ???isolate??? the effects of additional fines the cyclic and permanent strain responses of ???equivalent??? specimens with equivalent compaction and unsaturation condition, but different fines content, are compared. The results showed that the relative performance of the two materials (distinguished by the different percentage of fines content) in intertwined with the strong stress path dependency. It is also found that a material compacted at higher dry density may not improve its behaviour under cyclic loading, but may worsen with load cycles. Soil-water characteristic curve tests are conducted for the UGB materials investigated, showing high sensitivity of initial matric suction to moisture content, which increases further for the material with additional fines. This explains the notion of ???sensitivity??? of UGB materials as commonly suggested by practicing pavement engineers.
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O'Donnell, Jeffrey R. (Jeffrey Robert). "Design, construction, and commissioning of an in-core materials testing facility for slow strain rate testing." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28129.
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Cocle, Jennifer. "Development of the EBSD Intensity Response for Quantitative Strain Analyses of Materials." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=93017.
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Electron BackScattered Diffraction (EBSD) systems can be considered as a tool providing three kinds of responses: EBSD patterns (EBSPs) themselves, an indexing response (orientation data), and an intensity response (also called Band Contrast "BC", Image Quality "IQ", or Pattern Quality "PQ or P"). This work focused on the characterization and development of the intensity response. For now, the intensity response cannot be used for quantitative microstructural analyses, including strain analyses of materials. Indeed, this response is affected by several material and experimental conditions. Moreover, properties of the intensity response (strain sensitivity, reproducibility, exact relation with EBSP quality or diffraction band intensities) are not well-known and understood. This project constitutes an exploratory study on the development of the intensity response for quantitative strain analyses of materials. A new modelling and statistical approach is presented and assessed for transforming the raw (current) intensity response (values and grey-tones of intensity images) of commercial EBSD systems into an accurate and reproducible parameter allowing objective visualization and measurements of strain.Les systèmes de diffraction des électrons rétro-diffusés (EBSD) peuvent être considérés comme un outil offrant trois types de réponses: les patrons EBSD (EBSPs), la réponse d'indexation (données d'orientation) et la réponse d'intensité (aussi appelée Contraste de Bande «BC », Qualité d'Image « IQ », ou Qualité de Patron « PQ ou P »). Le présent projet s'est concentré sur la caractérisation et le développement de la réponse d'intensité. En effet, pour l'instant, la réponse d'intensité ne peut être utilisée pour réaliser des analyses microstructurales quantitatives des matériaux. En effet, cette réponse est influencée par de nombreux facteurs relatifs au matériau analysé et aux conditions expérimentales utilisées. De plus, les propriétés de la réponse d'intensité (sensibilité à la déformation, reproductibilité, relation exacte avec la qualité des EBSPs ou les intensités des bandes de diffraction) ne sont pour l'instant pas bien connues ni même compnses. Le présent projet représente donc une étude exploratoire visant le développement de la réponse d'intensité des systèmes EBSD commerciaux pour l'analyse quantitative de la déformation des matériaux. Dans ce projet, une approche de modélisation statistique est présentée et évaluée afin de transformer la réponse d'intensité actuelle (valeurs et tons de gris des images d'intensité) des systèmes EBSD commerciaux en une réponse précise et reproductible permettant de visualiser et de mesurer objectivement la déformation.
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Maess, Matthias. "Material characterization using nonlinear wave propagation." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/19311.
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Schliesman, Michael Dean. "Improved testing methods for measurement of extension-twist coupling." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18862.
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Wadlow, Philip James. "MATERIAL SELECTION AND TESTING FOR A RADIATION THERAPY CATHETER." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1661.
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Three different polymers (a high-density polymer and two other polymers) were tested for use as an x-ray catheter in a radiation therapy application. This report describes the testing of these three materials to determine which material is the best option for a long use catheter. Tests included tensile, simulated clinical life, and other tests. Some testing was performed using nitrogen and an industrial coolant. Testing revealed significant non-circularities for some catheters. With increasing pressure, the circularity of these catheters increased. The tensile tests were performed on samples with varying doses of radiation. Tensile testing showed significant decreases in ultimate tensile strength with increasing radiation dose for both polyurethanes. Other testing was performed on the two polyurethanes to determine their compatibility with the industrial coolant. The test showed good compatibility with the coolant. Simulated clinical life tests were performed on a test fixture and with software to run the radiation source automatically for several hours at a time. Overall, one material was found to have very low ductility, made lower with increasing radiation. The material with the higher ductility was chosen as the better catheter material despite some disadvantages when compared to the stiffer polymer. This report describes necessary tests for thin polymer geometries used in applications where resistance to radiation, mechanical integrity, and coolant compatibility are the main considerations.
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Lambert, John Peter. "Novel assessment test for granular road foundation materials." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/3099.
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Drivers for sustainability have made it necessary for the construction industry to adapt its traditional processes to become both more efficient and produce less waste. Performance based design and specification in the UK for motorways and trunk roads permits a very flexible approach to pavement design, material selection and performance related testing aimed at utilising materials to their maximum potential. However, it is clear that within the emerging philosophy of using materials that are 'fit for purpose' there are many technical challenges for design and specification. There is a need to develop suitable methods of evaluating materials prior to their being used on site. This project was born out of this requirement, with a particular emphasis on coarse granular materials due to their common role in capping construction and also their unique difficulty for measurement under laboratory conditions due to their large range of particle size. A novel assessment test for coarse capping materials for roads that can be used to indicate their likely short-term in situ performance, under controlled laboratory conditions before construction on site, has been developed during this research programme. Key findings relating to the behaviour of coarse capping materials, the use of stiffness measuring devices and variables that influence the measurement of composite stiffness are discussed in detail. The research highlights the necessity for adequate drainage and protection of foundation materials against increase in water content. When adopting a performance specification the timing of the pavement assessment is critical, both on site and in the laboratory. The performance measured on site should perhaps only be considered as a 'snapshot' relating to the stress state in the material at the time of testing.
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Barney, Ian Timothy. "Fabrication and Testing of Hierarchical Carbon Nanostructures for Multifunctional Applications." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1347925373.
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Goldbaum, Dina. "Micromechanical testing of cold sprayed Ti splats and coatings." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110400.
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Cold spray is a thermo-mechanical process where powder deposition is achieved through particle acceleration to supersonic velocities using a preheated and pressurized gas and a deLeval nozzle. The operating temperatures are typically below the melting point of most metals, which limits the material oxidation and phase transformations. Thick, dense coatings can be produced at fast deposition rates (20 g/min), making cold spray a candidate for near net shape production and part repair technology for aerospace applications. However, the cold-spray process is not as well documented as thermal spray techniques and the lack of the reliable experimental data limits the use of the cold spray, especially in load bearing applications.The present study explored the mechanical and microstructural properties of the cold spray titanium splats and coatings with novel micro-mechanical testing techniques coupled with high resolution microscopy. Electron channelling contrast imaging and nanoindentation mapping were used to examine the evolution of the microstructure and hardness of individual cold spray splats. The grain refinement and recrystallization were observed at particle interfaces which contributed to the strain hardening of the material. Splats deposited above critical velocity (700 - 900 m/s) exhibited nanometer scale grains with average grain diameters in the range of 50 to 200 nm at the splat/substrate interface with regions of metallurgical bonding. A modified ball bond shear test was implemented to measure the adhesion strength of individual cold spray splats. Deposition conditions under which the adhesion strength of splats reached the theoretical shear strength of titanium were identified. Coatings, produced at the same deposition conditions as strongly bonded splats, showed strong particle cohesion strength and low coating porosity. The coating porosity and poor particle cohesion strength affected the microindentation hardness measurements and tensile properties of the titanium coating. A new multi-scale indentation method was developed, where the comparison between the nanoindentation and microindentation and the definition of a "hardness loss parameter" was used to quantify the effect of the coating defects on hardness measurements. Titanium coatings that demonstrated hardness loss parameter approaching that of the bulk titanium were also coatings that demonstrated tensile properties, measured with microtensile testing technique, of fully dense material. The splat adhesion and multi-scale indentation testing techniques developed in the present research were shown to provide new methods that can be used towards optimization of the cold spray process for deposition of titanium coatings with properties of commercially manufactured material.La projection à froid est un processus thermomécanique où la déposition du revêtement est accomplie en accélérant les particules de la poudre, avec un gaz préchauffé et en pression, vers da vitesse supersonique. La température opérationnelle est, d'habitude, plus petite que le point de fusion de la plupart des métaux, ce qui limite l'oxydation et la transformation de phase. Des revêtements épais et denses peuvent être produits avec un taux de déposition rapide (20 g/min) permettant l'utilisation de la projection à froid pour la réparation des pièces et la formation des pièces proche de la forme finale pour les applications aérospatiales. Néanmoins, le processus de la projection à froid n'est pas aussi bien documenté que la projection thermique et manque de données expérimentales fiables, ce qui empêche l'application de la projection à froid aux pièces de portance. Le travail accomplis dans cette thèse est basé sur l'exploration des propriétés mécaniques et microstructurales des trempes et des revêtements par projection à froid de titane avec les nouvelles techniques micromécaniques et à l'aide de la microscopie à haute résolution. L'imagerie de contraste par canalisation et la cartographie par nanoindentation ont été utilisées pour examiner l'évolution de la microstructure et la dureté des trempes du titane. La diminution de taille des grains et la recristallisation des grains ont été observés à l'interface des particules ce qui a contribué à la hausse de dureté dans cette région. Les trempes, qui ont été déposées à une vitesse plus hautes que la vélocité critique (700 - 900 m/s), avaient des grains à l'échelle nanométrique (de 50 à 200 nm) à l'interface de trempe/substrat et présentaient des liaisons métallurgiques. Une nouvelle technique de balle au cisaillement modifié a été utilisée pour mesurer la force d'adhérence de ces trempes. Les conditions de la projection à froid, pour lesquelles les trempes ont démontré la force d'adhésion s'approchant de la force de cisaillement théorique du titane, ont était identifiées. Les revêtements, déposés aux mêmes conditions que les trempes démontrant une adhérence supérieure, ont présenté une forte cohésion des particules et une porosité du revêtement réduite. La porosité et la force de cohésion des particules avaient un effet sur les mesures de dureté et les propriétés de traction des revêtements. Une nouvelle méthode d'indentation multi-échelle a était développée dans laquelle la comparaison entre les mesures faites par nanoindentation et microindentation, définît comme le paramètre de perte de dureté, a été utilisé pour quantifier l'effet des défauts sur la mesure de dureté du revêtement. Les revêtements de titane qui avait un paramètre de perte de dureté s'approchant de celui du titane massif, ont démontré également les propriétés de traction du titane massif. Les techniques micromécaniques développées dans cette thèse, présente les nouvelles méthodes qui peuvent être utilisées envers l'optimisation du processus de projection à froid et le dépôt des revêtements de titane ayant des propriétés mécaniques de matériaux commerciaux.
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Kancherla, Anuroopa. "Resilient modulus and permanent deformation testing of unbound granular materials." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2711.
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Numerous research efforts have been devoted to characterizing the behavior of granular materials, which is one of the main concerns of pavement engineers. For better understanding of this behavior, laboratory tests where in-situ stress conditions and traffic loads are adequately simulated are needed. This study makes use of an expanded test protocol called a performance test that includes resilient modulus as well as permanent deformation testing. This test protocol determines three nonlinear resilient modulus parameters (k1, k2, k3) and two permanent deformation parameters (?,??). The resilient modulus test results are required inputs in the Level 1 analysis of the proposed American Association of State Highway and Transportation Officials (AASHTO) Pavement Design Guide. In addition, both resilient modulus and permanent deformation test results provide material property inputs to pavement performance prediction models.
This study also evaluated the within laboratory repeatability of the performance test and developed a within laboratory precision statement. Further, a statistical analysis was conducted on the test results to estimate the number of test specimens required for testing for specific reliability levels. Two test specimens are required for a reliability level of 15%. A within laboratory study was also conducted to investigate the influence of specimen size on test results. The specimen height was reduced from 12 in. (304 mm) to 8 in. (203 mm), and there was no difference in test results at a confidence level of 95%.
The performance test was further used successfully in subsequent studies to evaluate the behavior of granular materials and the influence of various factors on their behavior. As fines content increased, the resilient modulus values decreased and permanent deformation increased. As the moisture content increased, the resilient modulus value decreased and the resistance to permanent deformation decreased.
A simplified laboratory measurement tool that is repeatable, relatively cheap and easy to perform might prompt the use of laboratory measured values of resilient modulus in pavement design and facilitate correlation of these values to field measured values on a large scale. Use of measured data for the base properties rather than estimates would insure improved pavement designs and, in many cases, would save money in construction costs.
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Hu, Jinhua. "Computational modelling of hardness and soft impresser testing of materials." Thesis, Nottingham Trent University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429260.
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Gurav, Neelam. "Biocompatibility testing of resorbable materials using improved in-vitro techniques." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286360.
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Cox, Michael. "Development of high strain rate mechanical testing for metallic materials." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23989.
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Recent developments of high strain rate servo-hydraulic systems and high speed video imaging equipment have made the simple tensile test covering the quasi-static to dynamic range possible. However, obtaining reliable material data from the raw data produced from such tests requires a good understanding of the unique set of problems this testing technique can present. Tensile tests covering the quasi-static to 760 s-1 strain rate range were performed on Oxygen Free Electrolytic (OFE) copper, Al 6061-T6 and a Ta-2.5%W alloy. Modified standard sized tensile specimens were used in all tests and evaluations of the higher strain rate tests were carried out to understand the specimen dynamics at these high strain rates. Digital Image Correlation was used to measure strain at the higher strain rates and was ideal as a non-contact extensometer and could provide an indication if dynamic equilibrium is maintained throughout the test. The work strongly suggests that each material and specimen geometry will have its own strain rate threshold at which stress equilibrium is maintained. Appropriate methods were also necessary in processing the raw dynamic output to extract meaningful material data from the tests. Data obtained from the tests were successful in evaluating the materials behaviour over the quasi-static to dynamic strain rate range. The materials responded in a typical manner to that expected of their crystal structure and stacking fault energy, agreeing with results available from open literature. The tests performed in tension were compared with tests carried out in compression and showed the strain rate sensitivity in tension did not differ substantially to that in compression. Three constitutive material models were assessed, the Johnson-Cook (J-C) model was found to represent the experimental results of the OFE Cu and Al 6061-T6 materials well, but did not give such a good fit to the Ta-2.5%W material. The Zerilli-Armstrong (Z-A) model provided a good fit to Ta-2.5%W but not the OFE Cu and Al 6061-T6 materials. No satisfactory fit was achieved using the Mechanical Threshold Stress (MTS) model.