Dissertations / Theses on the topic 'Material Properties Determination'
To see the other types of publications on this topic, follow the link: Material Properties Determination.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 47 dissertations / theses for your research on the topic 'Material Properties Determination.'
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
Vogt, Thomas Karl. "Determination of material properties using guided waves." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273280.
Full text
2
Xavier, Angela Marie. "Determination of the Material Properties of the Pediatric Rib." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392019115.
Full text
3
Steinhaus, Thomas. "Determination of intrinsic material flammability properties from material tests assisted by numerical modelling." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/3273.
Full textAbstract:
Computational Fluid Dynamics (CFD) codes are being increasingly used in the field of fire safety engineering. They provide, amongst other things, velocity, species and heat flux distributions throughout the computational domain. The various sub-models associated with these have been developed sufficiently to reduce the errors below 10%-15%, and work continues on reducing these errors yet further. However, the uncertainties introduced by using material properties as an input for these models are considerably larger than those from the other sub-models, yet little work is being done to improve these. Most of the data for these material properties comes from traditional (standard) tests. It is known that these properties are not intrinsic, but are test-specific. Thus, it can be expected that the errors incurred when using these in computations can be significant. Research has been held back by a lack of understanding of the basic factors that determine material flammability. The term “flammability” is currently used to encompass a number of definitions and “properties” that are linked to standardised test methodologies. In almost all cases, the quantitative manifestations of “flammability” are a combination of material properties and environmental conditions associated with the particular test method from which they were derived but are not always representative of parameters linked intrinsically with the tested material. The result is that even the best-defined parameters associated with flammability cannot be successfully introduced into fire models to predict ignition or fire growth. The aim of this work is to develop a new approach to the interpretation of standard flammability tests in order to derive the (intrinsic) material properties; specifically, those properties controlling ignition. This approach combines solid phase and gas modelling together with standard tests using computational fluid dynamics (CFD), mass fraction of flammable gases and lean flammability limits (LFL). The back boundary condition is also better defined by introducing a heat sink with a high thermal conductivity and a temperature dependant convective heat transfer coefficient. The intrinsic material properties can then be used to rank materials based on their susceptibility to ignition and, furthermore, can be used as input data for fire models. Experiments in a standard test apparatus (FPA) were performed and the resulting data fitted to a complex pyrolysis model to estimate the (intrinsic) material properties. With these properties, it should be possible to model the heating process, pyrolysis, ignition and related material behaviour for any adequately defined heating scenario. This was achieved, within bounds, during validation of the approach in the Cone Calorimeter and under ramped heating conditions in the Fire Propagation Apparatus (FPA). This work demonstrates that standard flammability and material tests have been proven inadequate for the purpose of obtaining the “intrinsic” material properties required for pyrolysis models. A significant step has been made towards the development of a technique to obtain these material properties using test apparatuses, and to predict ignition of the tested materials under any heating scenario. This work has successfully demonstrated the ability to predict the driving force (in-depth temperature distribution) in the ignition process. The results obtained are very promising and serve to demonstrate the feasibility of the methodology. The essential outcomes are the “lessons learnt”, which themselves are of great importance to the understanding and further development of this technique. One of these lessons is that complex modelling in conjunction with current standard flammability test cannot currently provide all required parameters. The uncertainty of the results is significantly reduced when using independently determined parameters in the model. The intrinsic values of the material properties depend significantly on the accuracy of the model and precision of the data.
4
Karlsson, Patrik. "Determination of viscoelastic properties of adhesives." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-35521.
Full textAbstract:
A research project at Linnaeus University focuses on optimizing theadhesives joints between wood and glass, with the aim of obtain stiffcomponents that can act as a load and stabilizing elements and still betransparent. But there is, however, still a lack of knowledge regarding theadhesive materials which need to be further investigated. This thesis focused on testing six different adhesives in relaxation and todetermine the viscosity (η) and modulus of elastic (MOE, E). Viscosity andMOE are then used in combination in a standard linear solid model (SLS)describing the viscoelasticity mathematically. Figures and tables are used topresent the results and the evaluation. The so determined parameters can beused in e.g. finite element models for the design of load bearing timber glasscomposites.
5
Kang, JiJun. "Determination of elastic-plastic and visco-plastic material properties from instrumented indentation curves." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13509/.
Full textAbstract:
Instrumented indentation techniques at micro or nano-scales have become more popular for determining mechanical properties from small samples of material. These techniques can be used not only to obtain and to interpret the hardness of the material but also to provide information about the near surface mechanical properties and deformation behaviour of bulk solids and/or coating films. In particular, various approaches have been proposed to evaluate the elastic-plastic properties of power-law materials from the experimental loading-unloading curves. In order to obtain a unique set of elastic-plastic properties, many researchers have proposed to use more than one set of loading-unloading curves obtained from different indenter geometries. A combined Finite Element (FE) analysis and optimisation approach has been developed, using three types of indenters (namely, conical, Berkovich and Vickers), for determining the elastic-plastic material properties, using one set of ‘simulated’ target FE loading-unloading curves and one set of real-life experimental loading-unloading curves. The results obtained have demonstrated that excellent convergence can be achieved with the ‘simulated’ target FE loading-unloading curve, but less accurate results have been obtained with the real-life experimental loading-unloading curve. This combined technique has been extended to determine the elastic and visco-plastic material properties using only a single indentation ‘simulated’ loading-unloading curve based on a two-layer viscoplasticity model. A combined dimensional analysis and optimisation approach has also been developed and used to determine the elastic-plastic material properties from loading-unloading curves with single and dual indenters. The dimensional functions have been established based on a parametric study using FE analyses and the loading and linearised unloading portions of the indentation curves. It has been demonstrated that the elastic-plastic material properties cannot be uniquely determined by the test curves of a single indenter, but the unique or more accurate results can be obtained using the test curves from dual indenters. Since the characteristic loading-unloading responses of indenters can be approximated by the results of dimensional analysis, a simplified approach has been used to obtain the elastic-plastic mechanical properties from loading-unloading curves, using a similar optimisation procedure. It is assumed that the loading-unloading portions of the curves are empirically related to some of the material properties, which avoids the need for time consuming FE analysis in evaluating the load-deformation relationship in the optimisation process. This approach shows that issues of uniqueness may arise when using a single indenter and more accurate estimation of material properties with dual indenters can be obtained by reducing the bounds of the mechanical parameters. This thesis highlights the effects of using various indenter geometries with different face angles and tilted angles, which have not been covered previously. The elastic-plastic material parameters are estimated, for the first time, in a non-linear optimisation approach, fully integrated with FE analysis, using results from a single indentation curve. Furthermore, a linear and a power-law fitting scheme to obtain elastic-plastic material properties from loading-unloading indentation curves have been introduced based on dimensional analysis, since there are no mathematical formulas or functions that fit the unloading curve well. The optimisation techniques have been extended to cover time-dependent material properties based on a two-layer viscoplasticity model, has not been investigated before.
6
Li, Wanlu. "EXPERIMENTAL STUDIES ON THE DETERMINATION OF ACOUSTIC BULK MATERIAL PROPERTIES AND TRANSFER IMPEDANCE." UKnowledge, 2014. http://uknowledge.uky.edu/me_etds/48.
Full textAbstract:
Soft trim absorbing parts (i.e., headliners, backwalls, side panels, etc.) are normally comprised of different layers including films, adhesives, foams and fibers. Several approaches to determine the complex wavenumber and characteristic impedance for porous sound absorbing materials are surveyed and the advantages and disadvantages of each approach are discussed. It is concluded that the recently documented three-point method produces the smoothest results. It is also shown that measurement of the flow resistance and the use of empirical equations is sufficient for many common materials. Following this, the transfer impedance of covers, adhesives, and densified layers are measured using an impedance difference approach. The transfer matrix method was then used to predict the sound absorption of a multi-layered materal which included a perforated cover, fiber layers, and an adhesive. The predicted results agree well with measurement.
7
Vara, Amit Rashiklal. "Determination of material properties of mild steel at different temperatures and strain rates." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5458.
Full textAbstract:
Includes abstract.Includes bibliographical references.
Quantification of material properties through physical experiments is of significant importance. Test data from such experiments aid in the understanding of the material behaviour when exposed to a variety of loading conditions. Such data also help in the formulation of empirical and constitutive relations that can be applied in numerical simulations. This project dealt with the determination of the variation of the yield stress of mild steel with temperature and strain rate. This was achieved by carrying out high temperature tensile tests at different strain rates on mild steel specimens. These experiments also helped set a methodology for carrying out high temperature tensile tests using a servohydraulic universal tester. Results from the tests indicated that increases in temperature tended to decrease the yield stress, whereas increases in strain rate had the opposite effect. This was found to be consistent with data found in literature. It was also noted that the temperature effect was more dominant than the strain rate effect over quasi-static strain rates.
8
Frazzoli, Alessandra. "Determination of hydration properties of insoluble plant material with different methods under physiological conditions /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17305.
Full text
9
Sartkulvanich, Partchapol. "Determination of material properties for use in FEM simulations of machining and roller burnishing." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1167412216.
Full text
10
Al, Hamrani Emad, and Nemir Gibrael. "Fast determination of fuel/feedstock material properties and composition : By Near infrared (NIR) spectroscopy." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-33522.
Full text
11
Helweg, Christian. "Methods for determination of environmentally important physical- chemical properties of polar polycyclic organic material /." Roskilde : Roskilde University, Institute of Life Sciences and Chemistry, Risø National Laboratory, Department of Plant Biology and BiogeoChemistry, 1997. http://hdl.handle.net/1800/472.
Full text
12
Dippenaar, Jan Diederick. "The tensile properties of early age concrete and the experimental apparatus required for its determination." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96866.
Full textAbstract:
Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The early age cracking of concrete, which includes plastic shrinkage cracking (PShC) and plastic settlement cracking (PSeC), commonly occurs in flat concrete elements such as bridge decks and slabs or at the change of a concrete section depth. These cracks typically occur once the concrete has been cast and consolidated up to the final setting time, and initiate when the tensile stresses developed in the concrete exceeds its ultimate tensile strength or, alternatively phrased, when the restrained shrinkage induced strain in the concrete exceeds its tensile strain capacity. These cracks have a premature detrimental effect on the durability and strength of concrete structures as they allow deleterious materials to penetrate the concrete, which could cause the corrosion of steel reinforcing. With this in mind, the objective of this study is to gain a fundamental understanding of the tensile properties of early age concrete, up to the point of final setting, as well as the variables that affect these properties. This is done to better understand, and ultimately reduce the risk of early age cracking. To achieve this, experimental assemblies found in literature were evaluated and built upon to create a multi-component uniaxial tensile testing setup that is able to capture the complete stress-strain behaviour of early age concrete, while still in a plastic state. The following significant findings were attained from this study: • Reducing the coarse aggregate size in a concrete mix increases both the tensile strength and Young’s modulus of early age concrete, while reducing both its fracture energy and fracture process zone (FPZ) characteristic length. • The low volume addition of microfibres to a conventional concrete mix increases both the fracture energy and the FPZ characteristic length of early age concrete. • The low volume addition of microfibres to a conventional concrete mix increases the strain capacity of early age concrete shortly before and after the initial setting time. This increased strain capacity is believed to be of great significance for the prevention of PShC. • The addition of an accelerator to a conventional concrete mix accelerates the development of the tensile properties of early age concrete, while a retarder reduces it. • The addition of a retarder to a conventional concrete mix increases the strain capacity of early age concrete shortly before and after the initial setting time. This provides a reason for the reduced PShC severity observed in retarded mixes in certain instances. From this study it is concluded that the results from the tensile tests provide a greater understanding of the tensile properties of early age concrete as well as the variables that affect them. When interpreting these results in combination with those obtained from PShC experiments, it is suggested that it is possible to determine when and if PShC will occur.
AFRIKAANSE OPSOMMING: Die vroëe-ouderdom kraking van beton, wat plastiese krimp krake (PKK) en plastiese versakkings krake (PVK) insluit, kom algemeen voor in plat betonelemente soos brug-dekke en blaaie, of by die die verandering in die deursnit diepte van betonelemente. Die krake kom tiepies voor vandat beton gegiet en gekompakteer is totdat dit die finale settyd bereik, en vind plaas sodra die trekspanning wat in die beton ontstaan sy treksterkte oorskry of, anders bewoord, wanneer die verhinderde krimp geinduseerde vervorming van die beton, die vervormings-kapasiteit van die beton oorskry. Hierdie krake het ʼn voortydige nagelige uitwerking op die duursaamheid en sterkte van betonstrukture aangesien hulle toelaat dat skadelike stowwe die beton binnedring, wat die korrosie van staalbewapening veroorsaak. Met dit ingedagte is die doel van die studie om fundamentele kennis rakende die vroëe-ouderdom trekeienskappe van beton, tot by die punt van finale set, asook die veranderlikes wat die eienskappe beinvloed, te verwerf. Om vroëe-ouederdom krake beter te verstaan en uiteindelik, te voorkom, is hierdie kennis nodig. Eksperimentele opstellings in literatuur is ge-evalueer en op voortgebou vir die bou van ʼn multi-komponet eenassige terktoetsopstelling om die volledige spanning-vervorming gedrag van vroëe-ouderdom beton vas te vang. Die volgende bevindings het uit die studie aan die lig gekom: • ʼn Kleiner aggregaat grootte in n betonmeng verhoog beide die trekstrekte en Young se modulus van vroëe-ouderdom beton, terwyl dit beide die fraktuur-energie en die fraktuur proses sone (FPS) se karakteristieke lengte verminder. • Die lae volume byvoeging van mikrovesels tot ʼn betonmeng verhoog beide die fraktuur-energie en die FPS se karakteristieke lengte van vroëe-ouderdom beton. • Die lae volume byvoeging van mikrovesels tot ʼn betonmeng verhoog die vervormings kapasiteit van vroëe-ouderdom beton kort voor en na die aanvanklike settyd. Daar word geglo dat hierdie verhoogde vervormings-kapasiteit van groot belang is vir die voorkoming van PKK. • Die byvoeging van ʼn versneller tot ʼn betonmeng versnel die ontwikkelingstempo van die trekeienskappe van vroëe-ouderdom beton, terwyl ʼn vertrager dit verlaag. • Die byvoeging van ʼn vertrager tot ʼn betonmeng verhoog die vervormings-kapasiteit van vroëe-ouderdom beton kort voor en na die aanvanklike settyd. Dit verskaf die rede vir die bevinding dat die byvoeging van ʼn vertrager PKK in sekere gevalle verminder. Hierdie studie het bevind dat die die trektoetse ʼn groter begrip rakende die trek-eienskappe van vroëe-ouderdom beton, en die veranderlikes wat die eienskappe beinvloed, gelewer het. Wanneer die resultate van die studie tesame met PShC toetse geinterpreteer word, will dit voorkom dat dit moontlik is om te bepaal wanneer, en of PKK sal plaasvind.
13
Pitié, Frédéric. "High temperature thermal energy storage : encapsulated phase change material particles : determination of thermal and mechanical properties." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/57108/.
Full text
14
Demiralp, Yurdaer. "Determination of Material Properties and Prediction of Springback in Air Bending of Advance High Strength Steel (AHSS) and Commercially Pure Titanium (CP) Sheet Materials." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339768136.
Full text
15
Petropoulos, Nikolaos. "Improved understanding of sublevel blasting : Determination of the extent of the compacted zone, its properties and the effects on caving." Doctoral thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65973.
Full textAbstract:
Sublevel caving (SLC) is a mass mining method relying on the flowability of the blasted material. The ore is blasted in slices against caved material which is mainly waste rock. The result of the confined blast is greatly influenced by the interaction between the blasted material and the caved material. During blasting both materials change characteristics; the blasted material increases its porosity and compressibility due to breakage and swelling while the caved material is compacted and decreases in porosity and compressibility. The understanding of the mechanisms involved in this process is of significant importance. The behavior of the caved material (confining material) was studied in laboratory under dynamic loading. A new apparatus was developed to conduct impact tests to simulate blasting conditions. The tested material was a blend of crushed waste rock from drift development in the Kiirunavaara mine with maximum particle size 32 mm. The material was tested for two conditions, i.e. dry and wet (pendular state), and with different impact velocities (low (5 m/s), medium (8 m/s) and high (10-12 m/s)). During the impact tests, two types of measurements were taken; dynamic measurements based on the recordings from the installed accelerometers on the machine and static measurements pre- and post-impact. Additionally, the angle of repose, the impact duration, and the fragmentation was measured. In addition to the laboratory tests, small-scale blasting tests were carried out to investigate the burden behavior in confined conditions. The blasted specimen was a cuboid magnetic mortar block and the confining material was crushed concrete with maximum particle size 16 mm. The blocks were instrumented with custom-made incremental displacement sensor. After the analysis of the results from the above experimental work, two confined pillar tests (test #1 and test #2) were carried out at the Kiirunavaara mine. The preparation work for the pillar tests involved the development of instrumentation and installation techniques. The experimental configuration contained two blastholes and measurement holes in between the blastholes drilled from the neighboring drift. Test #1 mainly focused on the evaluation of the instrumentation and techniques while test #2 was focused on the interaction between the blasted burden and the confining material. The confining material in test #1 was a blend of ore and waste material from drift development at the Kiirunavaara mine. The characteristics of the material were unknown. Test #2 was split into two parts, the confining material in the first part was the same as in the laboratory impact tests and the second part of the pillar was confined by caved masses. The instrumentation was installed in the burden of the pillars and was equipped with accelerometers and displacement sensor. Additional instrumentation was also installed in the confining material. The burden in the small-scale blasting tests reached maximum velocity 29 m/s and maximum displacement 12.6 mm. In pillar tests, the burden movement was in the range of 0.9 to 1.1 m. In both pillar tests, burden erosion material was observed in the gap between the intact and the blasted burden. This material was finer compared to the blasted burden. The origin of this material was from the vicinity of the blastholes. The results of the laboratory tests showed that the wet material exhibited larger compaction zone than that of the dry material. The wet material showed apparent cohesion close to the impact surface of the tested material. A similar observation was made in test #2 where an agglomeration of the confining material, as a result of apparent cohesion, was observed on the surface of the blasted burden. The displacement data from the instrumentation in the burden and inside the confining material showed that the compaction zone follows an inverse exponential behavior. After the blast steeper angles of repose were measured indicating higher frictional forces between the particles. Moreover, the evidence of apparent cohesion and a larger angle of repose indicated the introduction of tensile strength in the material. The mass of the confining material was compressed elastically and plastically during the blast. After the blast, the material recovered its elastic deformation and pushed the blasted burden backward as observed in the small-scale blasting tests and the pillar tests. At this stage, the burden erosion material was compacted. Hence, there were 3 materials, i.e. burden erosion material, burden and confining material, which were compacted with different compaction rates. This condition promotes interlocking of the particles in the materials. If this behavior is correlated with a production SLC ring, then it indicates disturbances in flowability of the blasted material.
16
Senan, Anish Sen. "Determination of the Viscoelastic Properties of General Anisotropic Materials." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/SenanAS2003.pdf.
Full text
17
Sher, Arnold. "Holographic determination of mechanical properties and behaviour of materials." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/21833.
Full textAbstract:
Bibliography: pages 116-122.This study, which was primarily experimental, was aimed at investigating the feasibility and development of experimental procedures using holographic interferometry to determine different material properties such as: i) Modulus of Elasticity (E) ii) Poisson's ratio (v) (which included a study into the Modulus of Rigidity. (G)) iii) creep behaviour at room temperature. The Elastic Modulus (E) was determined from the relationship E=v²p, where v is the velocity of a longitudinal wave propagating in a long rod and p is the density of the rod. The technique of double-exposure holographic interferometry was used to record longitudinal waves propagating in long brass and steel rods. The waves were initiated by striking the end of the rod with a pendulum. From the pulsed laser interferograms obtained, the distance travelled by the wave in a known time could be measured and thereby the velocity (v) could be calculated. Experimental results indicate that it is feasible fo use holographic interferometry when dynamically determining the Elastic Modulus. The values produced for brass and steel compared favourably with the ones obtained from the ultrasonic velocity technique.
18
Kravets, Robert R. "Determination of thermal conductivity of food materials using a bead thermistor." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54223.
Full textAbstract:
The ultimate goal of this research was to determine the feasibility of measuring thermal conductivity of food materials using the bead thermistor with particular reference to high temperature.
Feasibility was established by examining the effects of the input parameters and the measurement error associated with them on the ability to estimate the test medium thermal conductivity test medium. This study showed that estimation of effective radius and bead thermal conductivity, the probe parameters, had the most significant impact on the ability to estimate the thermal conductivity of food materials. The probe parameters were determined by standardizing the thermistor probe against materials of known thermal conductivity. The current lack of well defined thermal reference materials in the range of water and most food products is a primary source of error associated with the method.
The accuracy and coefficient of variation of the Bead Thermistor Method were statistically documented in 10° increments over the temperature range of 25°C to 125°C. These results showed the method to have better than 10% accuracy across the entire temperature range. Distinct differences in accuracy between probes at a given temperature were also discovered. Standardization with water and castor oil resulted in a more accurate method than was achieved using water, castor oil, and glycerin.
The minimum particle diameter necessary to maintain the infinite boundary condition assumption required by heat transfer theory was found to be >5 mm.
The methodology was evaluated by examining the effects of temperature on the thermal conductivity of milk of different fat contents. A prediction equation for each product was attempted from the experimental data, but the data appear best fit by assuming a constant value across temperature. Heat altered the product physically which likely affected temperature dependence.
Based on the results of this study, the bead thermistor method can be considered a practical method for determining thermal conductivity of food materials over the temperature range considered in this study.Ph. D.
19
Tytler, Duncan G. F. "Determination of the thermal properties of materials utilising remote sensing techniques." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760687.
Full text
20
Yurtseven, Alp Eren. "Determination Of Mechanical Properties Of Hybrid Fiber Reinforced Concrete." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605268/index.pdf.
Full textAbstract:
ABSTRACT
DETERMINATION OF MECHANICAL PROPERTIES OF
HYBRID FIBER REINFORCED CONCRETE
Yurtseven, Alp Eren
M.Sc. Department of Civil Engineering
Supervisor: Prof. Dr. Mustafa Tokyay
Co-Supervisor: Asst. Prof. Dr. . Özgü
r Yaman August 2004, 82 pages Fiber reinforcement is commonly used to provide toughness and ductility to brittle cementitious matrices. Reinforcement of concrete with a single type of fiber may improve the desired properties to a limited level. A composite is termed as hybrid, if two or more types of fibers are rationally combined to produce a composite that derives benefits from each of the individual fibers and exhibits a synergetic response. This study aims to characterize and quantify the mechanical properties of hybrid fiber reinforced concrete. For this purpose nine mixes, one plain control mix and eight fiber reinforced mixes were prepared. Six of the mixes were reinforced in a hybrid form. Four different types of fibers were used in combination, two of which were macro steel fibers, and the other two were micro fibers. Volume percentage of fiber inclusion was kept constant at 1.5%. In hybrid reinforced mixes volume percentage of macro fibers was 1.0% whereas the remaining fiber inclusion was v composed of micro fibers. Slump test was carried out for each mix in the fresh state. 28-day compressive strength, flexural tensile strength, flexural toughness, and impact resistance tests were performed in the hardened state. Various numerical analyses were carried out to quantify the determined mechanical properties and to describe the effects of fiber inclusion on these mechanical properties. Keywords: Fiber Reinforcement, Hybrid Composite, Toughness, Impact Resistance
21
Kesler, Olivera E. (Olivera Elizabeth). "Experimental determination of processing-induced stresses and properties of graded nickel-alumina coatings." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46097.
Full text
22
Abbas, Zulkifly. "Determination of the dielectric properties of materials at microwave frequencies using rectangular dielectric waveguide." Thesis, University of Leeds, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569541.
Full text
23
Chen, Hongniao, and 陈红鸟. "Incremental displacement collocation method for the determination of fracture properties of quasi-brittle materials." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B49799447.
Full textAbstract:
This thesis presents experimental and numerical investigations on the fracture properties of quasi-brittle materials, including mortar, concrete and graphite. Fracture toughness in terms of the critical stress intensity factor K_IC and fracture energy G_F of the materials were determined through three-point bending tests on centre-notched beams. Furthermore, full-field displacement of the beams subjected to bend was obtained using Electronic Speckle Pattern Interferometry (ESPI) technique.
In order to verify the accuracy of the displacement data measured using the ESPI technique and to obtain reliable deformation information, the displacement and strain errors induced by the rigid-body motions of the specimen were quantified. This study found that the displacement errors were negligible whereas the strain errors were notable and must be eliminated. The influence of different rigid-body motions was analyzed. It was found that the out-of-plane movement of the specimen was critical and affected considerably the accuracy of strain data. Thus the experimental setup was improved accordingly to eliminate the influence of critical rigid-body motions.
Quasi-brittle materials have a finite stress region near the crack tip, known as the fracture process zone (FPZ). The materials exhibit nonlinear fracture behaviour in the FPZ. The cohesive crack model (CCM) is widely used to characterize the nonlinear fracture behaviour of quasi-brittle materials. According to the CCM, all the nonlinear behaviours in the FPZ can be represented by a cohesive crack, and the crack propagation is controlled by the relationship between the cohesive stress and crack opening, namely, the tension softening curve (TSC). Thus an accurate estimation of the TSC is essential.
In order to determine the TSC of quasi-brittle materials, an incremental displacement collocation method (IDCM) was originally developed in this study. In the IDCM, the deformation data measured by the ESPI sensor was analyzed to obtain the crack opening displacement (COD) of the notched specimens. The experimental COD profiles together with the CCM were then integrated into a finite element model to simulate the nonlinear fracture response of the specimen. By minimizing the difference between the computed and measured displacements at selected collocation points, the cohesive stress corresponding to certain crack opening was determined. The entire TSC was constructed in a step-by-step manner following the loading steps.
The IDCM was first applied to estimate the TSC of mortar. By using the estimated TSC, the displacements of the specimen under certain loading levels were computed. By comparing the computed displacements with the experimental data, the reliability of the IDCM and the accuracy of the estimated TSC were verified.
The application of the IDCM was further extended to the determination of the TSCs of concrete and graphite. The parameters used to define the shape of the TSC of the materials were determined using regression analysis. The applicability of those parameters was verified by comparing the TSCs estimated in the present study with those derived by other researchers. Recommendations were put forward to choose appropriate tensile properties of quasi-brittle materials in the numerical simulations. Furthermore, by using the ESPI technique, fracture phenomena of quasi-brittle materials were observed and reported. Such records can greatly enhance the understanding of crack initiation, growth and arrest in quasi-brittle materials, and lead to improvements to the existing fracture models.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
24
Lawson, Joseph L. "On the determination of the elastic properties of geopolymeric materials using non-destructive ultrasonic techniques /." Online version of thesis, 2008. http://hdl.handle.net/1850/7356.
Full text
25
Pavlov, Tsvetoslav. "Experimental determination and modelling of various thermo-physical properties of nuclear materials above 1500 K." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/58012.
Full textAbstract:
In the framework of improving nuclear power plant safety during accidents, the current study is focused on developing and applying a new technique for the high temperature determination of thermal conductivity, specific heat, thermal diffusivity, spectral and total hemispherical emissivity, as well as the melting points of nuclear materials. The new inverse method is based on the laser flash approach. The novel use of a finite element analysis (FEA) model (as part of the inverse method) allows accurate description of complex boundary conditions and has led to an improved accuracy of the evaluated properties. The inverse method has been tested for use with two devices – a pyrometer and an infrared camera. All experimental results are complemented by novel and existing solid state theory. The results obtained on isotropic, isostatically pressed, graphite (neutron moderator) are in good agreement with literature values (available to around 1500 K) and extend the available data up to 2800 K. Values are reported of specific heat, thermal conductivity and thermal diffusivity of UO2 from 1500 K to 2900 K. The specific heat model and measurements show, for the first time that a gradual pre-melting transition is consistent with high temperature literature values – enthalpy increment measurements and independently measured high temperature oxygen defect concentrations. Experimental results are also presented for the thermal conductivity, specific heat, thermal diffusivity, spectral and total hemispherical emissivity of ThO2 from 2000 K to 3050 K. It is the first time direct measurements of thermal conductivity and total hemispherical emissivity have been carried out on ThO2 at such high temperatures. All new results commit to a better understanding of the properties of nuclear materials, in particular nuclear fuel, under extreme conditions. Hence, this work will contribute towards improved predictions of nuclear core behaviour during an accident (using fuel performance or severe accident codes).
26
Lombardo, David. "Accurate Determination of Nonlinear Optical Properties of Cadmium Magnesium Telluride." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1429272337.
Full text
27
Kim, Sung-Hee. "Determination of aggregate physical properties and its effects on cross-anisotropic behavior of unbound aggregate materials." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2745.
Full textAbstract:
Work done by several researchers reveals that unbound aggregate materials show nonlinear cross-anisotropic behavior. The incorporation of cross-anisotropic properties significantly improves the predictions of stress distribution by reducing tensile stresses computed within granular layers. Existing pavement analysis and design approaches, however, generally assume the pavement structure to be linear isotropic layered system. This assumption is motivated by the difficulties in determining cross-anisotropic resilient material properties from laboratory experiments and lack of pavement anisotropic analysis programs.
Recently, the International Center for Aggregates Research (ICAR) developed a methodology to characterize unbound aggregate layers by considering stress-sensitivity and nonlinear cross-anisotropy. The ICAR model requires nine coefficients to account for stress-sensitivity and anisotropy of vertical, horizontal, and shear moduli. Unfortunately, ICAR testing protocol is time-consuming and expensive to perform and certainly do not lend themselves to routine testing. Since it is important to be able to consider the stress-sensitive and anisotropic nature of unbound granular materials, a simple procedure was proposed by accounting for the effects of aggregate gradation and shape properties in predicting the cross-anisotropic modular ratio of unbound granular materials. Variable confining pressure type repeated load triaxial tests were performed on six aggregate sources with three different gradations and three different moisture contents. The experimental results were analyzed within the framework of nonlinear cross-anisotropic elastic model in order to determine the model coefficients. Image analysis techniques were utilized to measure aggregate shape properties. The gradation and shape properties were fitted using a cumulative distribution function and nonlinear regression analysis, which is capable of capturing the complete distribution of these properties. The experimental and analytical results indicate that the vertical resilient modulus is greater than the horizontal resilient modulus and that aggregate physical properties significantly affect the anisotropic resilient behavior.
Based on finite element analysis, the anisotropic resilient behavior has substantial effect on the critical pavement responses. Thus, it is extremely valuable to approximate the degree of cross-anisotropy in unbound aggregates and to use it as input in the pavement analysis programs to adequately model unbound aggregate bases for pavement design and analysis.
28
Muir, Dave D. "One-sided ultrasonic determination of third order elastic constants using angle-beam acoustoelasticity measurements." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29766.
Full textAbstract:
Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Michaels, Thomas; Committee Co-Chair: Michaels, Jennifer; Committee Member: Degertekin, Levent; Committee Member: Qu, Jianmin; Committee Member: Ruzzene, Massimo; Committee Member: Scott, Waymond. Part of the SMARTech Electronic Thesis and Dissertation Collection.
29
Deniz, Saygin. "Determination Of Relations Between Elastic Properties Of Cement Mortars By Using Destructive And Nondestructive Methods." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611544/index.pdf.
Full textAbstract:
The measurement and monitoring of the elastic properties of cement-based materials is very important for assessing their quality, integrity and performance. Due to the nonhomogeneous and time-dependent characteristics of these materials, it is difficult to observe the developments in elastic properties with traditional destructive methods.
The aim of this thesis is to determine and monitor elastic properties of mortar specimens made with different cements by using resonant frequency and ultrasonic pulse velocity test methods, and to obtain relationships between these elastic properties.
For this purpose, eight different cement mortar mixtures were prepared with different constituent CEM I cements. Dynamic elastic moduli, static elastic moduli, dynamic Poisson&rsquos ratio and strength of these mixtures were observed for different ages. The relationships between these elastic properties are determined and the results obtained from two different nondestructive test methods are compared. Although nondestructive tests made it possible to obtain elastic properties of mortar mixtures, the results revealed that it is very difficult to develop a single relationship between different elastic properties of mortars with varying mixture proportions. This situation is mainly due to the anisotropy and nonlinear behavior of the mortar and the difficulty of describing the actual behavior of mortar by formulations defined for perfectly elastic materials.
30
Poolthong, Suchit. "Determination Of The Mechanical Properties Of Enamel Dentine And Cementum By An Ultra Micro-Indentation System." Thesis, The University of Sydney, 1998. http://hdl.handle.net/2123/4963.
Full text
31
Dejana, Herceg. "Modelovanje mernih transformatora bez jezgra sa feromagnetskim oklopom." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=96158&source=NDLTD&language=en.
Full textAbstract:
U ovoj doktorskoj tezi razvijen je postupak za ispitivanje uticajaoklopa na merni transformator bez jezgra sa stanovištalinearnosti transformatora i zaštite transformatora oduticaja elektromagnetske smetnje. Formiran je parametarski modeloklopa i mernog transformatora bez jezgra. Izvedena su merenjamagnetskih karakteristika feromagnetskih materijala, dat je novianalitički model histerezisa i određene su krive magnetisanja ipermeabilnosti materijala. Na osnovu numeričkih ieksperimentalnih rezultata, a u skladu sa definisanimkriterijumom, izvršena je analiza kvaliteta oklapanja zarazmatrane tipove oklopa.In this thesis a method for examining the effects of shielding on a corelessmeasuring transformer from the standpoint of transformer linearity and EMradiation shielding is developed. A parametric model of the shield and thecoreless measuring transformer is constructed. Measurements of magneticproperties of ferromagnetic materials were performed; a new analytical modelof hysteresis is developed; magnetization curves and permeability of thematerials are determined. Based on numerical and experimental results, andusing the defined criterion, the analysis of shielding quality of the consideredshield types was performed.
32
Mponya, Ereck. "Determination of rock material properties to design robust support at Unki Mine." Thesis, 2016. http://hdl.handle.net/10539/22326.
Full textAbstract:
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering.
Johannesburg, 2016Since mining platinum started at Unki Mine in 2005, large and small geologically controlled falls of ground (FOG) have been problematic especially in 2011 where a FOG caused a fatality. This study is about determining the rock properties at Unki Mine and then using the results to design and recommend robust support to reduce the FOG problems that are continuously happening. The study analysed all the FOG data from the mine database from 2010 to 2015 using statistical methods. Rock properties of the hangingwall, ore zone and footwall were determined from the laboratory tests. The geological structures were also mapped carefully. The results were then used as input data to the numerical modelling softwares Phase2 and J-Block. The J-Block program was used to determine the number of keyblocks that were stable, unstable and failed with support in designated and specified bords. A probabilistic approach was used to evaluate the stable span with special reference from small to large hangingwall instabilities for different mining scenarios. It was found out using Phase2 that large spans at Unki Mine are possible provided appropriate and robust support system is adopted. To fully address the issue of FOG problem at Unki Mine, a probabilistic approach is recommended as this is considered to be more appropriate than a deterministic approach that has been the traditional design approach so far.
MT2017
33
Zheng, Hong-Hui, and 鄭鴻輝. "Development of Resonant Ultrasound Spectroscopy for Determination of Material Properties of Solids at High Frequency." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/53372473796737249041.
Full textAbstract:
碩士國立成功大學
土木工程學系碩博士班
96
In this thesis, a resonant ultrasound spectroscopy was developed for determination of material properties of solids at high frequency, such as the shear modulus G, Young’s modulus E and linear viscoelastic damping of the material. Specimens are mounted between two piezoelectric ultrasonic transducers by corner contact without gluing. One of the transducers generates mechanical excitation, and the other behaves as a receiver. The corner contact provides elastically weak coupling to the transducers, and hence minimal perturbation to the vibration, minimal shift in resonant frequency and minimum parasitic damping. To compare with experimental results, finite element calculations with ABAQUS are performed. It is found that shear transducers provide stronger signals than compressional ones due to the lowest resonance mode being shear modes. For short cylinders, the orientation of the cylinder may influence the strength of measured signals when shear transducers are adopted. The tilt of the specimens may affect measurements as well. The linear viscoelastic damping is found to be linearly decreases as frequency increases, suggesting the string theory of vibrating dislocations is correct in metals, such as Sn, Al and stainless steel. In experiment result, the damping tan δ of Al about 2.29 ~ 5.58 × 10-4, SS about 3.21~8.46×10-4, and Sn about 4.55~ 1.29×10-3, roughly consistent with the data reduction method by using the Lorentzian curve fitting.
34
Fatseyeu, Arkadz. "Determination of properties of viscoelastic materials by nanoindentation." Thesis, 2005. http://spectrum.library.concordia.ca/9160/1/MR20759.pdf.
Full textAbstract:
The purpose of this work was to explore the possibility of measuring properties of viscoelastic materials by nanoindentation. Indentation is not a common method for determining properties of viscoelastic materials and nanoindentation is a very new, state-of-the art technology. Therefore, this research is one of very few works in this area. This study includes nanoindentation experiments on viscoelastic materials, determining bulk properties of the same materials by conventional rheological techniques, suggesting of physical models to measure properties of viscoelastic solids and viscoelastic liquids by nanoindentation and numerical simulations of the nanoindentation process. The experimental part includes nanoindentation tests of viscoelastic solids and viscoelastic liquids and comparing measured local properties with the bulk ones. The bulk properties were measured with SAOS and Torsion tests. For this investigation polybutadiene was selected as an example of a viscoelastic liquid and silicon cross-linked rubber as a viscoelastic solid. It was found that the local properties of solid polymers vary widely. However, by averaging data collected from various locations, the bulk properties can be determined accurately for the viscoelastic solids. For the physical modeling we validated the Sneddon & Sakai model of indentation of viscoelastic solids and suggested a model for the indentation of viscoelastic liquids, based on Stoke's theory of a potential flow around a sphere. Also nanoindentation of a viscous liquid was simulated using the FLUENT commercial code. It was found that for the indentation of viscoelastic materials with dominantly viscous properties, the indentation model developed from Stoke's theory gives realistic values for shear forces, but predicts a smaller than actual compression force, acting on the surface of the indenter. The comparison of the results of the mentioned above different approaches allowed us to draw conclusions about the advantages and limitation of the technology and theoretical analysis of nanoindentation and its application in rheometry. It was shown that nanoindentation can be successfully used for investigation of viscoelastic materials. Because of its unique abilities nanoindentation will become an irreplaceable tool in such areas as the testing of thin films, study of materials in a transient states, and biomedical research. However, there are number of technical and theoretical issues that need to be addressed. We outlined issues that need to be resolved and suggested direction for further research and development. Among them are: selection of a proper model to simulate behavior of particular viscoelastic material, further improvement of indentation control and data acquisition system, manufacturing new indenters of optimum shape and material
35
Chien, Hui-Lung, and 簡惠龍. "The Determination of Mechanical Properties of Biomedical Materials." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/85917240827423764764.
Full textAbstract:
博士國立中山大學
機械與機電工程學系研究所
100
The mechanical properties of biomedical materials were determined and discussed in this study. The extension and tensile tests for aorta and coronary artery were carried out using tensile testing machine. Based on incompressibility of biological soft tissue, the stress-stretch curves of arteries were obtained. This study proposed a nonlinear Ogden material model for the numerical simulation of coronary artery extension during stent implantation. The corresponding Ogden model parameters were derived by the obtained stress-stretch curves from tensile tests. For validation, the proposed nonlinear Ogden material model for coronary artery was applied to a Palmaz type stent implantation process. The simulated stent deformation was found to be reasonable. It had a good correlation with the measured results. The microindentation experiments were used to measure the mechanical properties of enamel and dentine of human teeth in this study. To reveal the relation between the experimental parameters and measured mechanical properties, Young’s moduli were investigated by varying experimental parameters. The parameter of maximum indentation load significantly influences measured values. Young’s modulus varies very slightly when 10 to 100 mN of maximum indentation load applied. Young’s modulus is not sensitive to the parameters of portion of unloading data and teeth age. The combination of finite element analysis and curve-fitting method is proposed to determine the mechanical properties of thin film deposited on substrate. The mechanical properties of thin film, i.e. Young’s modulus, yield strength and strain-hardening exponent, were extracted by applying an iterative curve-fitting scheme to the experimental and simulated force-indentation depth curves during the microindentation loading and unloading processes. The variation of mechanical properties of TiN thin films with thicknesses ranging from 0.2 to 1.4 μm was extracted. The results presented the film thickness effect makes the Young’s modulus of TiN thin films reduces with reducing film thickness, particularly at thicknesses less than 0.8 μm. Therefore, it can be inferred that a film thickness of 0.8 μm possibly represents the upper bound when employing macroscopic mechanics with bulk material properties.
36
Kang, Lee Chen, and 李承康. "Practical Determination of Dielectric Properties of Materials in ency." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/40111942206436427354.
Full textAbstract:
碩士國立臺灣科技大學
工程技術研究所
83
In this study, a dielectric constant measurement technique of microwave frequency is presented with theoretical analysis and experimental results. In this measurement technique the sample is inserted between waveguides to measure the S parameters over a wide bandwidth. Furthermore, in this study, with rigorous network analyzer calibration and de-embedding procedures, erect a complete measurement system. Experimental results are very close to known data.
37
Shiou-AnTsai and 蔡修安. "Modulated Ellipsometer for the Determination of the Properties of Optical Materials." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/04906751154118061265.
Full textAbstract:
碩士國立成功大學
工學院工程管理專班
98
In this research, we propose a scheme to measure the ellipsometric parameters of the materials, and construct an analytic model which is composed of the 4x4 method and signal processing system. And the simulation results and experimental initial results confirms that the feasibility of the proposed the modulated ellipsometry system which is combined with a heterodyne interferometer. The frequency of the saw tooth signal from a function generator that applied to the EO modulator was 1 kHz. In the experimental results, we have shown that the standard deviation of Ψ is 0.1313o, the standard deviation of Δ is 0.6829o, and the standard deviation of thickness is 0.9355(nm). In addition, we also show the feasibility of the full-field measurement by using the modulated ellipsometry we proposed. However, it’ll combine an image processing algorithm based on a three-integrating-bucket method and a heterodyne interferometer. The pre-experimental results have shown that the ellipsometric parameters (Ψ and Δ) have slight difference on the pattern of the solar cell. In this study, the measurement based on the modulated ellipsometry has been developed. Moreover, the proposing system has the ability to measure the full range of the ellipsometric parameters form the detected area of materials. However, this new proposed measurement system has two special characteristics. Unlike the other previous studies, we propose the scheme to measure the ellipsometric parameters of the materials by taking the two phases from the optical model. In addition, the presence of environmental disturbances via the use of a common-path configuration for the interferometer system cannot affect the measurement results by eliminating the DC component of the output light intensity signal in the signal processing algorithm.
38
"Numerical Modeling, Determination, and Characterization of Electrical Properties of Nanocomposites." Thesis, 2011. http://hdl.handle.net/1911/70493.
Full textAbstract:
A numerical model is presented for the determination of the electrical properties of carbon nanotube-based composites. The model incorporates several experimentally-based statistical distributions to account for the stochastic nature of the problem. These distributions include parameters such as nanotube length and diameter in addition to contact resistance. Using a Monte Carlo-based simulation technique, a random nanotube geometry is generated, checked for a percolation spanning network and then converted into a pseudo-3D resistor network for which the effective electrical conductivity is found. Each data point is the ensemble average of 500 or more simulations, each with a unique set of realized parameter values thereby reducing statistical variations of the solution. Studies are conducted to investigate the importance of incorporating the stochastic parameters and to characterize the impact of nanotube waviness and alignment on the effective composite properties. Electron tunneling distance is also included as a variable model parameter.
39
Chen, Ya-Wan, and 陳雅玟. "Theoretical Determination for Mechanical Properties of High-Performance Cementitious Materials with Defects." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/94347925113576605761.
Full textAbstract:
碩士國立高雄應用科技大學
土木工程與防災科技研究所
95
Based on the concept of a three-phase composite, the mechanical properties of high-performance cementitious materials (cement paste, mortar and concrete) with defects are examined. Those defects, especially voids and microcracks, were measured by MIP and SEM respectively while the materials with different aggregate contents were subjected to 0.3 , 0.5 , 0.8 and in turns. With the aim of a four-parameter model and the three-phase composite model, the stress-strain curves of high-performance cementitious materials were simulated. The simulated stress-strain curves were compared with the experimental ones to confirm the reliability of this three-phase composite theory we propose. Results show that the four-parameter model is suitable to determine stress-strain curves of high-performance cementitious materials by means of four parameters. Meanwhile, by comparing with the experiments, the theoretical predictions are in an acceptable range for the stress-strain curves of materials with voids and microcracks. Thus, it is anticipated that the three-phase micromechanics theory can be chosen to simulate the stress-strain relationships of high-performance cementitious materials.
40
Chen, Po-Chun, and 陳柏郡. "Mueller-matrix-based Polarimeter for the Determination of the Properties of Optically Anisotropic Materials." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/31676121772961220740.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
97
A new technique to measure optically anisotropic materials by Mueller matrix and Stokes parameters using a polarimeter is proposed. The measuring technique to determine the principal axis angle (α), retardance (β), diattenuation axis angle (θd), diattenuation (D), and optical rotation angle (γ) in the linear birefringence, linear diattenuation, and circular birefringence is successfully extracted by an analytical model. The dynamic range of five parameters α, β, θd, γ, and D are 0°~180°, 0°~180°, 0°~180°, 0°~180°, and 0~1, respectively, and only β is not in the full range. From author’s knowledge, this is the first finding that the linear birefringence and linear diattenuation could decouple in the analytical model. Five optical parameters of a single-mode fiber are extracted simultaneously and successfully. Also, a complex polarimetric system with an optical fiber is first quantitatively analyzed in Stokes parameters successfully by using this new proposed model. In conclusion, this could be an important step for researches on anisotropic materials like optical thin films or bio-tissues.
41
"A Numerical Resistor Network Model for the Determination of Electrical Properties of Nanocomposites." Thesis, 2011. http://hdl.handle.net/1911/70487.
Full textAbstract:
This thesis introduces a comprehensive numerical model for the determination of the electrical properties of carbon nanotube reinforced polymer composites. Procedures of this model are based on a new spanning network identification algorithm and the resistor network method. First, realistic nanotube geometry is generated from input parameters defined by the user. The spanning network algorithm then determines the connectivity between nanotubes in the representative volume element. Next, interconnected nanotube networks are converted to equivalent resistor circuits. Finally, Kirchhoff's Current Law is used in conjunction with finite element analysis to solve for the voltages and currents in the system and calculate the effective electrical conductivity of the nanocomposite. The Monte Carlo method is used to eliminate statistical variation by simulating five hundred random geometries. The model accounts for electrical transport mechanisms such as electron hopping and simultaneously calculates percolation probability, identifies the backbone, and determines effective conductivity. The accuracy of the model is validated by comparison to both models and experiments reported in the literature.
42
Vaidyanathan, M. S. "Modeling Lysis Dynamcis Of Pore Forming Toxins And Determination Of Mechanical Properties Of Soft Materials." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2466.
Full textAbstract:
Pore forming toxins are known for their ability to efficiently form transmembrane pores which eventually leads to cell lysis. PFTs have potential applications in devel-oping novel drug and gene delivery strategies. Although structural aspects of many pore forming toxins have been studied, very little is known about the dynamics and subsequent rupture mechanisms. In the first part of the thesis, a combined experimental and modeling study to understand the lytic action of Cytolysin A (ClyA) toxins on red blood cells (RBCs) has been presented. Lysis experiments are carried out on a 1% suspension of RBCs for different initial toxin concentrations ranging from 100 – 500 ng/ml and the extent of lysis is monitored spectrophotometrically. Using a mean field approach, we propose a non – equilibrium adsorption-reaction model to quantify the rate of pore formation on the cell surface. By analysing the model in a pre-lysis regime, the number of pores per RBC to initiate rupture was found to lie between 400 and 800. The time constants for pore formation are estimated to lie between 1-25 s and monomer conformation time scales were found to be 2-4 times greater than the oligomerization times. Using this model, we are able to predict the extent of cell lysis as a function of the initial toxin concentration. Various kinetic models for oligomerization mechanism have been explored. Irreversible sequential kinetic model has the best agreement with the available experimental data. Subsequent to the mean field approach, a population balance model was also formulated.
The mechanics of cell rupture due to pore formation is poorly understood. Efforts to address this issue are concerned with understanding the changes in the membrane mechanical properties such as the modulus and tension in the presence of pores. The second part of the thesis is concerned with using atomic force microscopy to measure the mechanical properties of cells. We explore the possibility of employing tapping mode AFM (TM-AFM) to obtain the elastic modulus of soft samples. The dynamics of TM-AFM is modelled to predict the elastic modulus of soft samples, and predict optimal cantilever stiffness for soft biological samples. From experiments using TM-AFM on Nylon-6,6 the elastic modulus is predicted to lie between 2 and 5 GPa. For materials having elastic moduli in the range of 1– 20 GPa, the cantilever stiffness from simulations is found to lie in the range of 1 – 50 N/m. For soft biological samples, whose elastic moduli are in the range of 10-1000 kPa, a narrower range of cantilever stiffness (0.1 – 0.6 N/m), should be used.
43
"A non-linear finite element model for the determination of elastic and thermal properties of nanocomposites." Thesis, 2009. http://hdl.handle.net/1911/61893.
Full textAbstract:
This thesis presents a non-linear model for the thermal and elastic properties of single-walled carbon nanotube reinforced polymer composites. Finite Element Analysis (1-EA), in conjunction with the Embedded Fiber Method (EFM), is used to calculate the effective stress-strain curve and thermal conductivity of the composite material. First, the geometry of a user-defined volume fraction of nanotubes is randomly generated and their properties are incorporated into the polymer matrix using the EFM. Non-linear FEA is next performed to account for the non-linear properties of the polymer matrix and the carbon nanotubes. Finally, Monte Carlo Analysis of five hundred random microstructures is performed to capture the stochastic nature of the random fiber generation and to derive statistically sound results. The model is validated by comparison with several different experiments reported in the open literature.
44
Erdoğan, Sinan Turhan Fowler David W. Garboczi Edward J. "Determination of aggregate shape properties using X-ray tomographic methods and the effect of shape on concrete rheology." 2005. http://repositories.lib.utexas.edu/bitstream/handle/2152/1904/erdogans78599.pdf.
Full text
45
Erdoğan, Sinan Turhan. "Determination of aggregate shape properties using X-ray tomographic methods and the effect of shape on concrete rheology." Thesis, 2005. http://hdl.handle.net/2152/1904.
Full text
46
Kunte, Girish V. "Vapour Pressure Studies Of Precursors And Atomic Layer Deposition Of Titanium Oxides." Thesis, 2008. http://hdl.handle.net/2005/762.
Full textAbstract:
This thesis describes the deposition of thin films of titanium oxide and Magnéli phases of titanium oxide by atomic layer deposition (ALD) using a novel β-ketoesterate precursor. Titanium oxide is a promising candidate for the high-k dielectric gate oxide layer for CMOS devices in microelectronic circuits. The Magnéli phases of titanium oxide are difficult to grow and stabilize, especially in the thin film form, and have useful properties. The thin film deposition of oxides by CVD/ALD requires suitable precursors, which are often metalorganic complexes. The estimation of vapour pressure using thermogravimetry is described, and employed, using an approach based on the Langmuir equation. This data is important for the evaluation of the suitability of these complexes as CVD precursors.
The first chapter gives a brief introduction to the topics that will be discussed in this thesis. Part one of the thesis deals with the synthesis, characterization, and studies of the vapour pressure and partial pressures of the precursors for CVD. This part comprises of the second, third and fourth chapter. The second chapter deals with the synthesis and characterization of the various metalorganic complexes that have been synthesized and characterized to evaluate their suitability as precursors for CVD. The third chapter describes the derivation of vapour pressure of precursors for CVD and ALD, from rising temperature thermogravimetric analysis (TGA) data, using the Langmuir equation. The fourth chapter deals with the determination of partial pressure of CVD precursors using data from low-pressure thermogravimetry.
Part Two of the thesis reports the deposition of titanium oxide thin films by ALD, and the detailed investigation of their properties, for application as high-k dielectric materials. Chapters five, six and seven constitute this part. The fifth chapter deals with the deposition of titanium oxide thin films by ALD. Chapter six describes the electrical characterization of the thin films of titanium oxide, for applications as high-k dielectric gate oxide layers for CMOS circuits. In the seventh chapter, the deposition of Magnéli phases of titanium by ALD is described. The dielectric properties of the films are studied.
47
(8713962), James Ulcickas. "LIGHT AND CHEMISTRY AT THE INTERFACE OF THEORY AND EXPERIMENT." Thesis, 2020.
Find full textAbstract:
Optics are a powerful probe of chemical structure that can often be linked to theoretical predictions, providing robustness as a measurement tool. Not only do optical interactions like second harmonic generation (SHG), single and two-photon excited fluorescence (TPEF), and infrared absorption provide chemical specificity at the molecular and macromolecular scale, but the ability to image enables mapping heterogeneous behavior across complex systems such as biological tissue. This thesis will discuss nonlinear and linear optics, leveraging theoretical predictions to provide frameworks for interpreting analytical measurement. In turn, the causal mechanistic understanding provided by these frameworks will enable structurally specific quantitative tools with a special emphasis on application in biological imaging. The thesis will begin with an introduction to 2nd order nonlinear optics and the polarization analysis thereof, covering both the Jones framework for polarization analysis and the design of experiment. Novel experimental architectures aimed at reducing 1/f noise in polarization analysis will be discussed, leveraging both rapid modulation in time through electro-optic modulators (Chapter 2), as well as fixed-optic spatial modulation approaches (Chapter 3). In addition, challenges in polarization-dependent imaging within turbid systems will be addressed with the discussion of a theoretical framework to model SHG occurring from unpolarized light (Chapter 4). The application of this framework to thick tissue imaging for analysis of collagen local structure can provide a method for characterizing changes in tissue morphology associated with some common cancers (Chapter 5). In addition to discussion of nonlinear optical phenomena, a novel mechanism for electric dipole allowed fluorescence-detected circular dichroism will be introduced (Chapter 6). Tackling challenges associated with label-free chemically specific imaging, the construction of a novel infrared hyperspectral microscope for chemical classification in complex mixtures will be presented (Chapter 7). The thesis will conclude with a discussion of the inherent disadvantages in taking the traditional paradigm of modeling and measuring chemistry separately and provide the multi-agent consensus equilibrium (MACE) framework as an alternative to the classic meet-in-the-middle approach (Chapter 8). Spanning topics from pure theoretical descriptions of light-matter interaction to full experimental work, this thesis aims to unify these two fronts.