Dissertations / Theses on the topic 'Mechanical property'
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Janakiraman, Balasubramanian. "Mechanical property measurement by indentation techniques." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3111.
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The mechanical properties of materials are usually evaluated by performing a tensile or
hardness test on the sample. Tensile tests are often time consuming, destructive and need
specially prepared specimens. On the other hand, there is no direct theoretical correlation
between the hardness number and the mechanical properties of a material although
phenomenological relationships do exist. The advantages of indentation techniques are
that they are non-destructive, quick, and can be applied to small material samples and
localized in fashion. Mechanical properties are typically determined from spherical
indentation load-depth curves. This process is again a time consuming one and not
suitable for situations where a quick assessment is required such as in the sheet metal
rolling industry.
In the present study, a novel method of measuring mechanical properties of the material
by multiple spherical indentations is developed. A series of indentations are made on the
substrate with a spherical indenter with different loads. The diameter of the indentation is
related to the load applied to determine the mechanical properties of the material, namely
the yield strength and the work hardening parameters. To determine the diameter of the
indentation quickly, a fiber optic sensing technique is developed. An incident light beam
from a semiconductor laser is coupled back into an optical fiber upon reflection from the
metal surface. By measuring the diffused light power reflected from the metal surface,
the diameter of the indentation is measured.
The spherical indentation technique is difficult for real time mechanical property
measurement of sheet metal in a processing line. Problems arise as the strip is traveling at
2,000 to 4,000 ft/min (10,000 to 20,000 mm/sec) in the processing line. As a first step in
developing a process that could be implemented in a real time processing line, a
preliminary study has been conducted for the prediction of yield strength by laser shock
processing.
2
Bargo, Johnny E. "Mechanical property characterization of recycled thermoplastics." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1473.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xvii, 143 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 104-105).
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Hill, Jeremy Lee. "Mechanical property determination for flexible material systems." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54993.
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Inflatable Aerodynamic Decelerators (IADs) are a candidate technology NASA began investigating in the late 1960’s. Compared to supersonic parachutes, IADs represent a decelerator option capable of operating at higher Mach numbers and dynamic pressures. IADs have seen a resurgence in interest from the Entry, Descent, and Landing (EDL) community in recent years. The NASA Space Technology Roadmap (STR) highlights EDL systems, as well as, Materials, Structures, Mechanical Systems, and Manufacturing (MSMM) as key Technology Areas for development in the future; recognizing deployable decelerators, flexible material systems, and computational design of materials as essential disciplines for development. This investigation develops a multi-scale flexible material modeling approach that enables efficient high-fidelity IAD design and a critical understanding of the new materials required for robust and cost effective qualification methods. The approach combines understanding of the fabric architecture, analytical modeling, numerical simulations, and experimental data. This work identifies an efficient method that is as simple and as fast as possible for determining IAD material characteristics while not utilizing complicated or expensive research equipment. This investigation also recontextualizes an existing mesomechanical model through validation for structures pertaining to the analysis of IADs. In addition, corroboration and elaboration of this model is carried out by evaluating the effects of varying input parameters. Finally, the present investigation presents a novel method for numerically determining mechanical properties. A sub-scale section that captures the periodic pattern in the material (unit cell) is built. With the unit cell, various numerical tests are performed. The effective nonlinear mechanical stiffness matrix is obtained as a function of elemental strains through correlating the unit cell force-displacement results with a four node membrane element of the same size. Numerically determined properties are validated for relevant structures. Optical microscopy is used to capture the undeformed geometry of the individual yarns.
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Wright, Andrew M. (Andrew Milton) 1976. "Real-time mass property estimation." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88852.
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Alifierakis, Michail. "Mechanical Property Modeling of Graphene Filled Elastomeric Composites." Thesis, Princeton University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10823814.
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Accessing improved elastomeric composites filled with functionalized graphene sheets (FGSs) requires an understanding of how the FGSs aggregate and how the position of FGSs affects the mechanical properties of the final composite material. In this thesis, I study both effects by devising models for 2-D particles in the 10s of microns scale and comparing my results with experiments. These models enable an understanding of the effect of the particles in a level that is hard to be studied experimentally or by molecular models. In the first part, I present a model for aggregation of 2-D particles and apply it to study the aggregation of FGS in water with varying concentrations of sodium dodecyl sulfate (SDS). The model produces clusters of similar sizes and structures as a function of SDS concentration in agreement with experiments and predicts the existence of a critical surfactant concentration beyond which thermodynamically stable FGS suspensions form. Around the critical surfactant concentration, particles form dense clusters and rapidly sediment. At surfactant concentrations lower than the critical concentration, a contiguous ramified network of FGS gel forms which also densifies, but at a lower rate, and sediments with time. This densification leads to graphite-like structures. In the second part, I present a model for the prediction of the mechanical properties of elastomers filled with 2-D particles. I apply this model to the Poly-dimethylsiloxane (PDMS)-FGS system. For a perfect polymer matrix and when inter-particle forces are ignored the strength of the composite can be increased with the addition of particles but elongation at failure decreases relative to neat PDMS. Maximum load transfer to the particles is achieved when particles are covalently linked to span the whole polymer matrix. Minimum drop in elongation at failure can be achieved by maximizing the distance between the covalently linked particles. When the assumption of a perfect polymer matrix is relaxed, it can be shown that there is a certain particle concentration range for which elongation at failure can be increased as the particles can protect the polymer by redistributing high stresses created by inherent polymer defects that would lead to early failure.
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Carrasquel, Isha. "STRUCTURE-PROPERTY QUANTIFICATION RELATED TO CRASHWORTHINESS." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07102008-140429/.
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The objective of this study is to characterize critical component structure-properties on a Dodge Neon for material response refinement in crashworthiness simulations. Crashworthiness simulations using full-scale finite element (FE) vehicle models are an important part of vehicle design. According to the National Highway Traffic Safety Administration (NHTSA), there were over six million vehicle crashes in the United States during 2004, claming lives of more than 40,000 people. Crashworthiness simulations on a detailed FE model of a 1996 Plymouth/Dodge Neon were conducted on the NHTSA for different impact crash scenarios. The top-ten energy-absorbing components of the vehicle were determined. Material was extracted from the as-built vehicle and microstructural analyses were conducted. Tension tests at different temperatures and strain rates were performed as well as microhardness tests. Different microstructural spatial clustering and mechanical properties were found for diverse vehicle components. A plasticity model based on microstructure was used to predict the material response of the front bumper.
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Kim, Joon-Seop. "Structure-morphology-mechanical property relationships in various random ionomers." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28475.
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The aim of this study was to explore the effects of a range of variables on the properties of ionomers, and also to investigate the structure-morphology-property relationships in these materials in order to advance our understanding in the light of the EHM model. In the first part of the work, the influence of variables such as sample preparation conditions, molecular weight and degree of neutralization on the dynamic mechanical properties of ionomers were studied.In the second part, the effects of surfactant addition and chemical structure of ionomers were investigated. Sodium sulfonated polystyrene ionomers were mixed with the surfactant sodium p-dodecylbenzene sulfonate. This surfactant molecule has a head group identical to the ionic group of the polymer chain. Therefore, the head group resides in the multiplets, and tail group in the restricted mobility region surrounding the multiples. This results in a dramatic decrease in the cluster $T sb{ rm g}$ as a function of the amount of added surfactant. In the next project, the contact surface area of the chain and its effect on multiplet size was studied. An inverse relationship between contact surface area and size of multiplet was found; if the size of multiplet is decreased, the cluster $T sb{ rm g}$ increases and the ionic plateau is also higher and longer. Furthermore, when the pendant group of the polymer is replaced by a bulkier group, the chain becomes stiffer. As a result, the two $T sb{ rm g}$s shift to higher temperatures. In still another part of the study, the dynamic mechanical properties of poly(styrene-co-sodium methacrylate) ionomers were re-investigated in detail. Discontinuities in the plots of various parameters obtained from the tan $ delta$ vs temperature and modulus vs temperature curves as a function of the ion contents were found. These discontinuities suggest that there are two morphological changes in the system as a function of the ion contents, one at ca. 4-6 and the other at ca. 12-14 mol % of ions. In addition, the data were interpreted using filler and percolation concepts. The Guth equation for modulus vs filler content is applicable up to 30 volume % of the clusters. The Halpin-Tsai equation for the regular system is also applicable at low ion contents. For the percolation approach, the percolation threshold was found at 5.4 mol % of ions. The critical exponent and critical volume fraction of clusters were found to be 1.31 and 0.64, respe
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Benjamin, Alex(Alex Robert). "3D organ property mapping using freehand ultrasound scans." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128989.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 141-151).
3D organ property mapping has gained a considerable amount of interest in the recent years because of its diagnostic and clinical significance. Existing methods for 3D property mapping include computed tomography (CT), magnetic resonance imaging (MRI), and 3D ultrasound (3DUS). These methods, while capable of producing 3D maps, suffer from one or more of the following drawbacks: high cost, long scan times, computational complexity, use of ionizing radiation, lack of portability, and the need for bulky equipment. We propose the development of a framework that allows for the creation of 3D property maps at point of care (specifically structure and speed of sound). A fusion of multiple low-cost sensors in a Bayesian framework localizes a conventional 1D-ultrasound probe with respect to the room or the patient's body; localizing the probe relative to the body is achieved by using the patient's superficial vasculature as a natural encoding system. Segmented 2D ultrasound images and quantitative 2D speed of sound maps obtained using numeric inversion are stitched together to create 3D property maps. A further advantage of this framework is that it provides clinicians with dynamic feedback during freehand scans; specifically, it dynamically updates the underlying structural or property map to reflect high and low uncertainty regions. This allows clinicians to repopulate regions within additional scans. Lastly, the method also allows for the registration and comparison of longitudinally acquired 3D property/structural maps.
by Alex Benjamin.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Hollinshead, Phillip Anthony. "Texture and mechanical property developments in aluminium alloy hot rolling." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38036.
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Kibble, Kevin Alexander. "Surface finish-mechanical property relation in reaction-bonded silicon carbide." Thesis, University of Wolverhampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240364.
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Fahey, Maureen Theresa. "Mechanical property characterization and enhancement of rigid rod polymer fibers." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/42983.
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Stagon, John Thomas. "The Mechanical Property Analysis of Thin Diamond Coated Metal Substrates." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1337013344.
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Richardson, Mark D. "Microstructural and mechanical property development in metastable beta titanium alloys." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/12663/.
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Titanium alloys represent an ever increasing proportion of the materials employed in aerostructural applications. Metastable beta alloys in particular, offer high specific strength and good corrosion resistance that allow them to compete with steels. Ti-5Al-5Mo-5V-3Cr and Ti-10V-2Fe-3Al are two such alloys used in the main landing gear of large commercial aircraft. Thermomechanical processing of metastable beta alloys is critical in obtaining the desired microstructure, which in turn governs the mechanical properties. This therefore demands a thorough understanding of the relationship between processing, microstructure and mechanical properties in order to optimise the final product and process route. This project characterises the microstructural and mechanical property variation within forged Ti-5553. Microstructural variables are quantified in order to examine their relative influence on mechanical properties. This reaffirmed the importance of microstructural control during materials processing. Gradual changes in primary alpha morphology, beta volume fraction and grain structure were observed throughout the forgings. However, it was also found that the size of secondary alpha precipitates could fluctuate rapidly over relatively short distances. The effect on mechanical properties was significant enough to completely reverse the general trends exhibited over the entire forging. It was also found that the heat treatment response varied with orientation. It would appear that unspecified microstructural variables limited the maximum achievable properties in certain orientations, preventing the heat treatment from further affecting them. However, changes in work hardening behaviour were observed which increased the proof stress while leaving the tensile strength essentially unchanged. The influence of subtransus thermomechanical processing on the microstructural evolution of Ti-10-2-3 was also investigated. Flow curves exhibited an initial peak at low strain followed by extensive flow softening. Microstructural analysis would suggest that the fragmentation and globularisation of acicular alpha particles is at least partially responsible for this softening effect. The use of torsion tests demonstrated that non-linear strain paths may not represent an efficient means of globularising primary alpha. The Burger’s Orientation Relationship (BOR) was found to break down at a linear strain of about 0.5. However, the process of ‘strain reversal’ could partially restore this up to an original linear strain of around 0.8. Solution treatment and ageing revealed that more highly strained regions were less responsive to age hardening.
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Xie, Mayue. "Interface problems in micromechanics and effective composite property analysis." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.
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Wigley, Nicholas Roy. "Property prediction of continuous annealed steels." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/38602/.
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To compete in the current economic climate steel companies are striving to reduce costs and tighten process windows. It was with this in mind that a property prediction model for continuous annealed steels produced at Tata Steel’s plants in South Wales was developed. As continuous annealing is one of the final processes that strip steel undergoes before being dispatched to the customer the final properties of the strip are dependent on many factors. These include the annealing conditions, previous thermo-‐mechanical processing and the steel chemistry. Currently these properties, proof stress, ultimate tensile strength, elongation, strain ratio and strain hardening exponent, are found using a tensile test at the tail end of the coil. This thesis describes the development of a model to predict the final properties of continuous annealed steel. Actual process data along with mechanical properties derived using tensile testing were used to create the model. A generalised regression network was used as the main predictive mechanism. The non-‐linear generalised regression approach was shown to exceed the predictive accuracy of multiple regression techniques. The use of a genetic algorithm to reduce the number of inputs was shown to increase the accuracy of the model when compared to those trained with all available inputs and those trained using correlation derived inputs. Further work is shown where the fully trained models were used to predict the relationships that exist between the processing conditions and mechanical properties. This was extended to predict the interaction between two process conditions varying at the same time. Using this approach produced predictions that mirrored known relationships within continuous annealed steels and gives predictions specific to the plant that could be used to optimise the process.
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Tucker, Matthew T. "STRUCTURE-PROPERTY STRESS STATE DEPENDENT RELATIONSHIPS UNDER VARYING STRAIN RATES." MSSTATE, 2009. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04022009-091044/.
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In this work, understanding the microstructural effects on stress state and strain rate dependent plasticity, damage, and failure of aluminum and magnesium alloys were examined. Several experimental techniques were employed to implement the test data into a physics-based internal state variable plasticity-damage model. Effects arising from various strain rates, stress states, and material orientations were quantified and discussed within the framework of linking microstructural features to mechanical properties. The method developed for determining structure-property relations was validated by accurately capturing the effects for a variety of materials and loading conditions. The end result is a methodology capable of predicting the onset of damage and failure for a material loaded under complex dynamic conditions.
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Ji, Guang. "Study on Microstructure and Adhesion Property of Electrospun Polymer Blends." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1435789657.
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Cerezo, Frances Therese, and francestherese_cerezo@hotmail com. "Thermal stability and mechanical property of polymer layered graphite oxide composites." RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080627.161157.
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Polymer composites formed from layered fillers with high surface volume ratio show enhanced reinforcement. Graphite oxide is a high modulus material that can be separated into thin layers with high surface area. The aim of this study is to prepare polymer layered graphite oxide composites using functionalised polyolefin to enhance compatibility with various forms of layered graphite oxide in varying concentration. Functionalised polyolefins reinforced with layered graphite oxides and expanded graphite oxides were prepared using solution blending and melt blending methods. Three different mixing methods with varying shear intensity were employed to prepare polymer layered graphite oxide composites. The crystalline structure, thermal and mechanical properties of the prepared polymer layered graphite oxide composites was studied. Oxidised graphite prepared from the Staudenmaier method and its exfoliated form were dispersed in poly(ethylene-co-methyl acrylate-co-acrylic acid) (EMAA) via solution blending to prepare EMAA layered composites. The thermal stability was determined using thermogravimetric analysis. The EMAA layered composites showed higher thermal stability in comparison with pure EMAA. The mechanical properties of these EMAA layered composites were determined through dynamic mechanical analysis. Shear modulus, yield stress and storage modulus of EMAA in the presence of graphite oxide fillers decreased. A solution blending method was used to prepare poly(propylene-grafted-maleic anhydride) layered expanded graphite oxide composites (PPMA-EGO). Two types of PPMA-EGO were prepared using different mixing methods - low and high shear were employed. The effects of preparative mixing methods on the PPMA-EGO properties were investigated. The mechanical properties of PPMA-EGO obtained from dynamic mechanical analysis indicated that EGO had a reinforcing effect on the elastic behaviour of PPMA-EGO. This is due to strong interfacial adhesion between PPMA and EGO as a result of hydrogen bonding. The elastic behaviour of PPMA-EGO was affected by the surface area of graphite flakes. Low sheared PPMA-EGO elastic behaviour was found to be higher compared with that of high sheared PPMA-EGO. A melt blending method was used to prepare PPMA-EGO with varying EGO concentration. The interconnected network structure of EGO in the PPMA-EGO was not observed as shown by its scanning electron microscopy images. Thermogravimetric analysis of PPMA-EGO indicates increased decomposition temperature of the PPMA matrix. Dynamic mechanical analysis showed enhanced storage modulus of PPMA-EGO. The maximum elastic modulus of PPMA-EGO was observed at 3 %wt of EGO. The electrical conductivity of PPMA-EGO was measured only for EGO concentrations above 2 %wt. The EGO concentration was found to be the most critical factor in the enhancement of the electrical conductivity of PPMA-EGO. Wide angle X-ray diffraction analysis of all polymer layered graphite oxide composites revealed no change in interlayer spacing of graphite layers, indicating the absence of EMAA intercalation in the graphite layers. The crystallisation temperature and crystallinity of all polymer layered graphite oxide composites were determined using differential scanning calorimetry. The results indicated that graphite oxide and expanded graphite oxides acted as nucleating agents in inducing the crystallisation of functionalised polyolefin in the layered composites. However, the degree of crystallinity of functionalised polyolefin decreased in the layered composites.
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Zhang, Zhongbin. "Transport and mechanical property studies of barrier plastic food packaging materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ40392.pdf.
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Aitchison, Graham. "The mechanical characterisation of a model bioresorbable composite for property prediction." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421490.
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Kumar, Naresh. "Exploring the variability in mechanical property testing of dental resin composites." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1494/.
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The invention of dental resin based-composites (RBCs) has provided a broad range of materials for the restoration of load-bearing posterior teeth with excellent clinical results and adequate longevity. Currently, a lack of consensus exists among researchers regarding classification of RBCs as a result of slight variations in filler size and associated interchangeable mechanical properties of “microhybrid”, “nanohybrid” and “nanofilled” RBCs. Also, the inconsistency in mechanical property testing of RBCs is evident amongst researchers. This research explored the variability in experimental and statistical testing methodologies of RBCs. The current study identified a wide variation in the bi-axial flexure strength (BFS) of commercial and experimental RBCs with respect to deformation rate with a complex relationship between resin constituents and filler morphology. Experimental unfilled resins revealed deformation rate dependence in BFS following 1 week dry, 1 and 13 weeks wet storage regimes, whereas the addition of fillers modified the deformation rate dependence following 13 weeks wet storage and resulted in the BFS of filled resin composites being independent of testing speed. These findings suggested the need for the development of RBCs with appropriate formulations for clinical situations where variable strain rates may occur, for example, patients with parafunctional habits. To date, the alignment of specimens during storage regimes prior to mechanical property testing has rarely been reported. The effect of specimen alignment on the BFS and surface hardness of RBCs was evaluated and a greater decrease in the both properties were found following wet upright compared with stacked and upper surface exposed alignments. These observations were attributed to a variation in diffusion of water as the result of difference in exposed surface areas of specimens, which may lead to different findings and associated interpretation between investigators. Weibull statistics are used for the analysis of strength data of RBCs, however their applicability to RBCs might be questioned due to some viscous deformation prior to brittle failure. The findings of current study supported the applicability of Weibull statistics for the microhybrid and nanofilled RBCs but not a flowable RBC, which suggested that Weibull statistics may not necessarily be applicable for all RBC types. It was demonstrated that variability and irrelevance in testing methods may cause incorrect interpretation of data among researchers and consequently affect the future research and development of RBCs. Therefore, further standardisation of testing methods is required.
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Wang, Wei. "Selective laser melting of Al alloys : microstructure and mechanical property development." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6613/.
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The aim of this project is developing a near net-shape processing route for Al-alloy compressor components with Selective Laser Melting (SLM). Design of experiments (DOE) techniques such as the Response Surface Method, and statistical analysis using the analysis of variance (ANOVA) were applied for processing parameter optimisation in order to minimise the defects (pores or cracks) and studying the influence of powder, such as chemical composition, particle shape/ morphology and particle size and SLM parameters, such as laser power, laser scan speed, hatch spacing, laser scan strategy, island size. The tensile, fatigue and creep properties of the samples built using the optimum parameters were assessed. The microstructures were assessed using optical, scanning and electron transmission microscopy. The influence of building directions (0°, 45°, and 90°) and post processing (T6 heat treatment and Hot Isostatic Pressing (HIPping)) on microstructure and mechanical properties were also investigated.
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Lam, Eric W. (Eric Wing-Jing). "Mechanical property characterization of metal nano-particle films for MEMS devices." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78451.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 79-83).
Printing-based fabrication methods have emerged as a promising alternative to conventional lithographic processes in a number of applications. These methods are being exploited in display manufacturing, flexible electronics, and more recently MEMS. Unlike applications in printed electronics, MEMS devices require comparatively thick layers, typically on the order of microns. In the micron-thickness regime, nanoparticle-based inks are the preferred means for material delivery, in large part due to the ability to deliver high solids content. However, sintered nanoparticle films possess unique morphology and hence different properties when compared to bulk material or materials deposited through other methods and are dependent on the processing conditions. As such, careful characterization of the film's properties is critical to successful adoption of this technology. A detailed methodology to identify the process-mechanical property of metal nanoparticle-based films was developed using silver nanoparticles as the case study. Silver nanoparticle-based cantilevers and films were fabricated through inkjet printing and conventional microfabrication techniques. These structures were mechanically characterized by beam deflection analysis and nanoindentation to map Young's moduli versus the processing conditions. The results were coupled with sintering and powder metallurgy models to explain the data. For silver-based nanoparticle films, it was determined that the process and mechanical property have a power law relationship with the ratio of the sintering temperature and the melting point of bulk silver. This relationship enables prediction of mechanical properties and provides guidance for optimization of sintering conditions towards a desired mechanical property. The specific results reported include: i) process flows to fabricate nanoparticle-based microstructures, ii) detailed methodology to map film features and properties versus processing conditions, and iii) an empirical model explaining the data and enabling prediction of the resultant properties. While this methodology was shown to determine the process-mechanical property relationship for silver nanoparticle-based films, it should be generally applicable to other metal nanoparticle-based films and lays the groundwork for characterizing this class of materials.
by Eric Wing-Jing Lam.
Ph.D.
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Park, Conrad. "Mechanical Performance and Structure-Property Relations in6061B Aluminum Metal Matrix Composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1547842396716777.
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Yanagioka, Masaki. "Analysis of the structure-mechanical property relationships of nanoparticle-filled hydrogels /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Eng, Mindy. "Exploring property driven design fabrication through materials testing and software development." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/65176.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis. Vita.
Includes bibliographical references (p. 33).
Since its introduction in the late 1980s, layered manufacturing has become an increasingly efficient and common means to delivering functional and visually representative prototypes in relatively short amounts of time from previously prepared Computer-Aided Design files. However, most layered manufacturing technologies today produce only single material, constant property prototypes from a limited array of materials. In this project, we explore a different approach to layer manufacturing, namely, a layered manufacturing product that, while using a single material, produces an entity of varying material properties. Materials testing of PMC®-724 demonstrate the material's capacity to possess a range of Shore A Hardness over a range of elasticity, illustrating the potential for printing with variable property materials. Moreover, we will also explore a new approach to fabrication that challenges the concept of Computer- Aided Manufacturing (CAM) by introducing a software application that, rather than providing a means of digitizing the geometry of a completed design, allows engineers and designers to create and design structures that are defined at various points by their material behavior as opposed to their geometry. As a proof of concept demonstration, a mono-material, variable property shoe sole will be printed using property-mapped polyurethane elastomer PMC®-724 with the new software.
by Mindy Eng.
S.B.
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Burcham, Megan Noel. "Multiscale structure-property relationships of ultra-high performance concrete." Thesis, Mississippi State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10141618.
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The structure-property relationships of Ultra-High Performance Concrete (UHPC) were quantified using imaging techniques to characterize the multiscale hierarchical heterogeneities and the mechanical properties. Through image analysis the average size, percent area, nearest neighbor distance, and relative number density of each inclusion type was determined and then used to create Representative Volume Element (RVE) cubes for use in Finite Element (FE) analysis. Three different size scale RVEs at the mesoscale were found to best represent the material: the largest length scale (35 mm side length) included steel fibers, the middle length scale (0.54 mm side length) included large voids and silica sand grains, and the smallest length scale (0.04 mm side length) included small voids and unhydrated cement grains. By using three length scales of mesoscale FE modeling, the bridge of information to the macroscale cementitious material model is more physically based.
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Söderberg, Jansson Marcus, and Oskar Lundkvist. "Property Optimization of PM-gearing." Thesis, KTH, Maskinkonstruktion (Inst.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209549.
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The purpose of this bachelor thesis is to design and optimize a powder metal gear through FEM-analyzes. The moment of inertia and weight of the gear shall be reduced at the same time as the demands on tension and bending stiffness are met. The gear that is used as reference and will be optimized is the standard gear in the FZG-rig at the department of Machine Design at KTH. The work is initiated with a literary study. After that a CAD-model of the gear and its pinion is created in Solid Edge. Then the reference gear is analyzed in the FEM-program Ansys and control calculations are made according to standards and handbooks. Thereafter different geometry and density variations are made and tested. The tests are then compared to the reference gear. By varying the density of the gear and varying the geometry of the waist of the gear several different optimization proposals could be made. By cutting material off the waist of the gear the weight can be reduced by 6 % with an increase in bending stress of 1 %. If a bigger increase in bending stress is allowed more material can be removed. If the bending stress increase is allowed to be 5 % a decrease in weight and moment of inertia of 14 % is obtained. With an increase in deformation of 5 % a decrease of 11 % in weight and moment of inertia was obtained. The different tested geometries behave relatively equal up to a 3 % decrease in weight with respect to deformation but begins to vary considerably if the weight is further decreased. Removal of material should be symmetric around every gear tooth to avoid transmission failure which also leads to increased noise. The results show that it is better to remove material under each gear tooth rather than under the root. It is also advantageous to remove material close to the flange. Further work is required to analyze and optimize the gears even more. Fatigue tests as well as different load cases should be analyzed.Syftet med kanditatexamensarbetet är att ta fram och egenskapsoptimera ett pulvermetallurgiskt kugghjul med hjälp av FEM-analyser. Tröghetsmomentet och vikten på kugghjulet ska minimeras samtidigt som kraven på spänningar och böjstyvhet uppfylls. Det kugghjul som används som referens och ska optimeras är standardkugghjulet i FZG-riggen på institutionen för maskinkonstruktion på KTH. Arbetet inleds med att en litteraturstudie görs. Sedan tas en CAD-modell för kugghjulet och dess tillhörande drev fram i Solid Edge. Därefter analyseras referenskugghjulet i FEM-programmet Ansys och kontrollberäkningar görs enligt standarder och handböcker. Därefter konstrueras och analyseras olika geometrier och densitetsvariationer och jämförs med referenskugghjulet. Genom att variera densiteten på kugghjulet och variera geometrin på kugghjulets liv kunde flertalet optimeringsförslag tas fram. Genom att göra en utskärning i livet kan vikten minskas med 6 % utan att böjspänningen påverkas mer än 1 %. Om en större ökning i böjspänning tillåts kan ytterligare material avlägsnas. Om böjspänningsökningen tillåts vara ca 5 % kan en viktminskning och tröghetsmomentsminskning på ca 14 % åstadkommas. Vid en deformationsökning på 5 % erhölls en viktminskning och tröghetsmomentsminskning på ca 11 %. De olika geometrier som testas beter sig relativt lika upp till 3 % viktminskning med avseende på deformation och börjar därefter variera kraftigt. Borttagning av material måste ske symmetriskt kring varje kuggtand för att transmissionsfel och därmed ökat buller ska undvikas. Det visar sig att ta bort material under kuggen är bättre än att ta bort material under kuggroten. Det gynnsamt att göra geometriska förändringar närmast flänsen på kugghjulet. Vidare arbete krävs för att analysera och optimera kugghjulen ytterligare. Utmattningstester och fler lastfall bör analyseras.
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Dong, Yao. "Effects of Processing Techniques on Mechanical Properties of Selected Polymers." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271805/.
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The mechanical properties of a polymer represent the critical characteristics to be considered when determining the applications for it. The same polymer processed with different methods can exhibit different mechanical properties. The purpose of this study is to investigate the difference in mechanical properties of the selected polymers caused by different processing techniques and conditions. Three polymers were studied, including low density polyethylene (LDPE), polypropylene (PP), and NEXPRENE® 1287A. Samples were processed with injection molding and compression molding under different processing condition. Tensile and DMA tests were performed on these samples. The acquired data of strain at break from the tensile tests and storage modulus from the DMA were utilized to calculate brittleness. Calculated brittleness values were used to perform analysis of variance (ANOVA) to investigate the statistical significance of the processing technique and condition. It was found that different processing techniques affect the brittleness significantly. The processing technique is the major factor affecting brittleness of PP and NEXPRENE, and the processing temperature is the major factor affecting brittleness of LDPE.
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Korte, Sandra. "Processing-Property Relationships of Hemp Fibre." Thesis, University of Canterbury. Mechanical Engineering, 2006. http://hdl.handle.net/10092/1175.
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There is great interest in the plant Cannabis sativa (hemp) as a source of technical fibres for the reinforcement of polymers in composite materials due to its high mechanical properties. As a natural fibre hemp also offers biodegradabilty and is therefore an inexpensive and renewable alternative to glass fibres However, the environmental benefits of natural fibres cannot be fully exploited if the manufacturing of their composites involves polluting processing steps. Unfortunately, there is still a lack of environmetally sustainable processing methods yielding technical fibres of sufficient quality. Enzyme application as a biotechnological processing method is a good candidate for this aim and is therefore actively investigated at present. In this work the effects of a range of enzymes on the morphological, compositional and mechanical properties of hemp was investigated. The enzymes were firstly characterised and then applied to hemp fibre for differing periods of time. After visual inspection, a set of fibre samples were selected and subjected to further analysis by Fourier-Transform Infrared Spectroscopy (FTIR), tensile testing and scanning electron microscopy (SEM). The commercial formulation Pectinex® Ultra-SL emerged as the most efficient in terms of treatment time and fibre quality. The effectiveness of treatments was further investigated by developing a novel experimental method that correlates the adhesion forces measured by atomic force microscopy (AFM) on the fibre surface to the properties of the fibres or composites. In order to identify correlations between the adhesion forces and fibre or composite properties, hemp fibre was subjected to four distinctly different treatments to obtain significant differences between fibre properties. The fibres and composites were then analyzed using a combination of FTIR, tensile testing, 3-point bend testing, dynamic mechanical analysis (DMA) and SEM. Based on this comprehensive dataset the AFM data was correlated using the software SPSS. The information derived from AFM (adhesion forces and surface topology) was useful in the clarification of fibre modifications evoked by the treatments.
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Thiraphattaraphun, Linda. "Structure/property relationships in polypropylene nanocomposites." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/structureproperty-relationships-in-polypropylene-nanocomposites(388eafc0-a98e-4a78-be0d-4d647a122d87).html.
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In this work, structure/property relationships in polypropylene (PP) nanocomposites have been investigated for different nanofillers. Nanofillers of modified clay based on montmorillonite (MMT) and multi-wall carbon nanotubes (MWNTs) have been selected and incorporated to the PP matrix as either single nanofillers or hybrid nanofillers. Melt mixing via a twin screw extruder and further moulding by injection moulding have been used to prepare PP nanocomposites. Moreover, the dilution of MWNT masterbatch has been used to prepare PP/MWNT and PP/clay/MWNT nanocomposites. Three types of the PP nanocomposites have been obtained: PP/clay, PP/MWNT and PP/clay/MWNT nanocomposites. In all three types of the PP nanocomposites, α- and -PP crystals were observed in the wide angle X-ray diffraction (WAXD) patterns. Furthermore, the addition of nanofillers to the PP did not appear to affect the PP orientation. Slight PP orientation in the PP nanocomposites was shown in the two-dimensional X-ray diffraction (2D-XRD) patterns. Mixed clay layers were combined in the PP/clay and PP/clay/MWNT nanocomposites and investigated by WAXD as well as transmission electron microscopy (TEM). In addition, the aggregated and individual MWNTs were present in both the PP/MWNT and PP/clay/MWNT nanocomposites TEM images. A rough fracture surface with cracks was revealed from the scanning electron microscopy (SEM) images of the three types of PP nanocomposites. Polarized optical microscopy (POM) micrographs were taken at different temperatures during cooling in a hot stage and revealed the limitation of PP spherulite growth upon adding the nanofillers to the PP. The incorporation of nanofillers was found not to affect the glass transition temperature (Tg) of PP which investigated by dynamic mechanical analysis (DMA). However, the increase of both the peak melting temperature (Tm) and the peak crystallization temperature (Tc) of PP with adding the nanofillers was shown by differential scanning calorimetry (DSC) thermograms. In addition, the nanofillers also have been shown to act as nucleating agents. The thermal stability of PP in a nitrogen atmosphere was enhanced by the nanofillers when examined by thermogravimatric analysis (TGA). DMA and tensile testing were performed and showed that the nanofillers act as reinforcement for the PP. The distribution, orientation and deformation of MWNTs in the PP/MWNT and PP/clay/MWNT nanocomposites have been followed by Raman spectroscopy. Significant shifts of the Raman G'-band from the MWNTs was obtained during deformation of the MWNT nanocomposites and the hybrid clay/MWNT nanocomposites as the stress transfer from the PP matrix to the MWNTs has occurred. A correlation between calculated modulus from deformation and measured modulus from DMA and tensile testing has been found for PP/MWNT and PP/clay/MWNT nanocomposites. Finally, the PP nanocomposites have been considered for use in packaging applications.
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Brosi, Justin Keith. "Mechanical Property Evolution of Al-Mg Alloys Following Intermediate Temperature Thermal Exposure." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270163761.
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Thesis (Master of Sciences (Engineering))--Case Western Reserve University, 2010Department of Materials Science and Engineering Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Peters, Ashton. "Digital Image Elasto-Tomography: Mechanical Property Reconstruction from Surface Measured Displacement Data." Thesis, University of Canterbury. Department of Mechanical Engineering, 2007. http://hdl.handle.net/10092/2775.
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Interest in elastographic techniques for soft tissue imaging has grown as relevant research continues to indicate a correlation between tissue histology and mechanical stiffness. Digital Image Elasto-Tomography (DIET) presents a novel method for identifying cancerous lesions via a three-dimensional image of elastic properties. Stiffness reconstruction with DIET takes steady-state motion captured with a digital camera array as the input to an elastic property reconstruction algorithm, where finite element methods allow simulation of phantom motion at a range of internal stiffness distributions. The low cost and high image contrast achievable with a DIET system may be particularly suited to breast cancer screening, where traditional modalities such as mammography have issues with limited sensitivity and patient discomfort. Proof of concept studies performed on simulated data sets confirmed the potential of the DIET technique, leading to the development of an experimental apparatus for surface motion capture from a range of soft tissue approximating phantoms. Error studies performed on experimental data from these phantoms using a limited number of shape and modulus parameters indicated that accurate measurements of surface motion provide sufficient information to identify a stiffness distribution in both homogeneous and heterogeneous cases. The elastic reconstruction performed on simulated and experimental data considered both deterministic and stochastic algorithms, with a combination of the two approaches found to give the most accurate results, for a realistic increase in computational cost. The reconstruction algorithm developed has the ability to successfully resolve a hard spherical inclusion within a soft phantom, and in addition demonstrated promise in reconstructing the correct stiffness distribution when no inclusion is present.
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Edwards, Wendy M. "Microstructural and mechanical property modelling for the processing of Al-Si alloys." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/7754.
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The components of a modem internal combustion engine are required to give extreme reliability over extended periods of operation and none is exposed to more arduous conditions than the piston, especially in the pin boss and crown regions of pistons for diesel engines. The increasing emissions requirements and performance targets demanded of direct injection diesel engines has resulted in steep increases in both specific powers and maximum cylinder pressures. This has in turn lead to greater temperatures and pressures being felt by the piston. The adaptation of the piston design to these increasingly demanding load and temperature conditions has required a continuous improvement and innovation in the field of materials and process technologies. The vast majority of the internal combustion engine pistons produced globally are made by a gravity die casting process using Al-Si based alloys. Although Al-Si alloys have been the subject of a great deal of research over the last 30 years, the majority of work has been based on fairly rudimentary characterisation of the microstructures as a function of alloy chemistry and cooling rate. Most of the attention has been paid to the silicon morphology and distribution rather than on a fundamental knowledge of the development of the complex microstructures and intermetallic phases that arise in commercial alloys. However, the properties of cast near-eutectica: luminium-silicon alloys are very strongly influenced by the microstructure, i.e. the primary aluminium, and the interdendritic microconstituents, such as secondary phases, intermetallics, inclusions and porosity. A fine and uniform grain size is often desired as it improves mechanical properties of castings such as tensile strength, ductility and fatigue resistance, and at the same time aids castability, improves porosity distributions and reduces hot tearing susceptibility. A thorough phase characterisation has been carried out using a number of techniques including optical and electron microscopy with electron backscatter diffraction (EBSD), and image analysis. Use was also made of thermodynamic modelling to predict the volume fraction and distribution of phases within the microstructure as a function of chemical composition and process parameters. From this analysis a detailed understanding of the phases occuffing in multicomponent Al-Si alloys was established. Furthermore, additions associated with grain refining, i.e. Ti, Zr and V, have been investigated systematically using commercial and model alloy systems. All three additions were observed to refine the structure of the castings through the formation of the phase A13Ti, although combined additions with Zr were found to be less efficient due to a 'poisoning' effect on the A13Ti. It was also established that there is a strong competition between the effects of grain refiners and P, with the formation of AbTi reducing the nucleating efficiency of AIP to silicon. The nucleation and growth of the primary silicon phase were thus examined by EBSD. AIP was confirmed as nucleating the silicon epitaxially, after which growth continues by surface nucleation, although the presence of twins were seen to influence the shape of the crystal. Finally, suggestions have been made as a consequence of this work for the future development of piston alloys.
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Rong, Zhouwen. "Multiscale modelling of defect behaviour and mechanical property effects in irradiated metals." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406831.
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Nolte, Adam John. "Fundamental studies of polyelectrolyte multilayer films : optical, mechanical, and lithographic property control." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38516.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 207-225).
Polyelectrolyte multilayers (PEMs) are a versatile type of thin film that is created via layer-by-layer assembly of positively and negatively charged polymers from aqueous solutions. Precise control of the PEM thickness, chemical functionality, and molecular architecture is made possible by changing the polyelectrolytes and assembly conditions during film growth, allowing films to be designed with properties suitable for a given application. This thesis elucidates the intra-film structure and interactions of PEMs through the use of optical, mechanical, and chemical techniques. PEM rugate filters, wherein the refractive index varies through the depth of the film in a continuous, periodic fashion, were constructed by confining silver nanoparticle growth to layers of nanometer-scale thickness. The ability to construct such structures is shown to be dependent on the ability to precisely control the concentration of metal-binding carboxylic acid groups throughout the depth of the film. Software to enable the computation design and optical simulation of these and similar structures was developed.
(cont.) A buckling instability technique was used to probe the Young's modulus of PEM assemblies as a function of polyelectrolyte type, assembly pH, and the relative humidity of the ambient environment. In particular, a two-plate methodology was developed to allow testing on a broad array of multilayer films, and an experimental apparatus was constructed to allow in situ modulus measurements of PEM films under controlled humidity conditions. These techniques are used to elucidate the strong effects that polyelectrolyte type, assembly pH, and the ambient humidity can have on the stiffness of PEM films. The controlled removal of material from assembled PEMs was accomplished via etching of films in solutions of increasing ionic strength. The properties of etched films and process dynamics point to evidence of a polydispersity-enabled phenomenon driven by dissolution of polyelectrolyte complexes containing chains of disproportionate molecular weight. Kinetic and equilibrium data are presented that support this hypothesis. Beyond elucidation of the underlying mechanisms governing molecular interactions within PEMs, possible practical applications for the particular PEM assemblies described in this thesis are discussed, including conformable interference filters and buckling-enabled patterning.
by Adam John Nolte.
Ph.D.
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Wang, Hsuan-Ho, and 王炫和. "Mechanical Property Measurement of Biomolecules." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/14602282405342265122.
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碩士國立交通大學
機械工程學系
98
In this study, we developed a device to measure mechanical property of biomolecules. It mainly utilized the micropipette and AFM probe for the measurement, and it can stretch the cell from its initial length to the ultimate break point. We calculated the stretching force from the bending deflection of the AFM probe. Myotubes are the objects in this study. Myotubes are the basic unit cell in muscular structure and are derived of myoblast differentiation. The measurement and understanding of myotube strength is the foundation from which to investigate the mechanical properties of muscle.
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Zhang, Zong-Qi, and 張宗祺. "Study On Mechanical Property of Heel Pad." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/06668571820230750405.
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Yen-Ming, Peng. "Preparation and Mechanical Property of Carbon Nanotube Bundles." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709322392.
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YEN, CHENG CHUN, and 鄭鈞晏. "Electrical and Mechanical Property of ABS/graphite Nanocomposites." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/z42p7r.
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碩士國立臺北科技大學
化學工程研究所
100
Polymeric materials are used in many fields. Polymer nanocomposites can have more applications by adding different types of nanoparticles to the polymer matrix. For example, nanographite platelets(NGP) are common materials that are added to polymer matrices to increase the electrical conductivity of composites due to their lower price. Adding conductive fillers into a matrix can change a polymer from an insulator into a semiconductor. These conductive polymer composites can be used in electromagnetic interference applications. As well as the conductive properties, the mechanical properties of the composites can also be increased due to the rigidity of nanoparticles. This article focuses on the different processes that could affect the electrical and mechanical property of materials. Two different issues were studied, one is solid material, while the other one is foamed material. In the case of solid material, compounding ABS with nanographites of different aspect ratios by solvent blending and by melt compounding to fabricate polymer conductive composites. In the case of solvent blending, due to the small size of NGP, the Van Der Waals force can make the graphite aggregated. Before blending, ultra-sonication was used. In the case of melt compounding, we pre-mixed the graphite powder with ABS particles before feeding it into the extruder. The compounded samples were either compression molded for electrical conductivity testing or injection molded for mechanical properties testing. In the case of solvent blending, since the aspect ratio of the nanographite can be maintained, the percolation threshold will be lower than samples made by compounding. Percolation threshold can be as low as3wt%. To predict the aspect ratio of graphite after compounding, the percolation model and the Halpin-Tasi equation were applied. It is found that the dispersion and aspect ratio of the filler in the polymer matrix are the important factors that decide the fitting result between the experimental modulus data and theoretical predictions using Halpin-Tsai equations. In the case of foam materials, we find that the electrical properties increase with the foam density, percolation threshold rise from 14wt% to 10wt%. For the foam materials,surface resistivity dropped from 3.7x1013 to 3.1x108 with the concentration from 10wt% to 12wt%.
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Peng, Yen-Ming, and 彭彥銘. "Preparation and Mechanical Property of Carbon Nanotube Bundles." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/96354938341424701610.
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碩士國立清華大學
材料科學工程學系
94
In the past decade, there have been a lot of progress in the research of carbon materials. The discovery of fullerenes has given us a whole new insight into carbon materials. Furthermore, since the carbon nanotubes (CNTs) were discovered by Iijima in 1991, many potential applications have been proposed for carbon nanotubes, including electron transport, high-strength composites, energy storage, sensors, field emission displays, nanometer-sized semiconductor devices, probes, and drug release. Some of these applications have now been realized in commercial products. A great deal of effort has been devoted to the research of manufacture and properties of carbon nanotubes. In this study, CNT bundles were fabricated via pyrolysis of hydrocarbons by chemical vapor deposition. A template-synthesis method based on the porous anodic aluminum oxide membrane was applied. Both one-step and two-step processes were attempted to improve the morphologies of CNT bundles. The effect of amount of catalyst on fabricating the CNT bundles was studied as well. The bundles with 200-300nm in diameter and several micrometers in length were composed of amorphous carbon film on the outside and tangled muti-walled carbon nanotubes with an average outer diameter of 13nm inside the film. In addition, the mechanical properties of the CNT bundles fixed by platinum pads at both ends were studied by nanoindentation. The elastic modulus of a single CNT bundle was calculated to be 33 GPa. The field emission properties were also measured. It exhibited a turn-on field of 2.64 V/μm as the electric current density reached 10 μA/cm2 from the J-E curve. The field enhancement factor was calculated to be 891 from the F-N plot.
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Chen, wei-shen, and 陳威伸. "Extraction of Mechanical Property Parameters Using Asymmetrical Structures." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/23717400810481936915.
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碩士東南技術學院
機電整合研究所
95
ABSTRACT This research investigated the dynamics characteristics of symmetrical and asymmetrical structures, by combining the finite element analysis and modal testing results, and then used an optimization scheme to extract the mechanical properties of the structures under test. With the help of experimental modal testing and finite element analysis, two sets of natural frequencies and mode shapes of the structures could be obtained. Integrating both sets of natural frequencies into an optimization procedure and utilizing the ANSYS software to perform analysis and optimization, the structures’ Young’s modulus, Poisson’s ratio and shear modulus were extracted. For a comparison purpose, this research employed a symmetrical and an asymmetrical structure of two entirely different scales: one in millimeter scale and the other in micrometer scale. Conducting experimental modal testing on both structures, assorting the obtained frequencies, and updating the finite element models with the frequency information, the length of an error vector defined as the difference between analysis and experimental frequencies could be minimized. As for the symmetrical microcantilevers, only bending modes were able to be measured, and therefore the extraction of Poisson’s ratio performed poorly. As for the asymmetrical aluminum plates, the torsional modes were easily measured, and therefore the extraction of Poisson’s ratio achieved a very good result. In general, this research successfully employed an optimization scheme to extract structures’ mechanical properties proving the feasibility of the proposed procedure, and it provides an alternative choice for determining the mechanical properties of materials.
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Shimpi, Nilesh Nathu. "Mechanical testing and numerical simulation of mechanical structure-property relationship of silica aerogel." 2005. http://digital.library.okstate.edu/etd/umi-okstate-1518.pdf.
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General, Michael. "Microstructural and Mechanical Property Changes in Ion Irradiated Tunsgten." Thesis, 2013. http://hdl.handle.net/1969.1/149365.
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Sustainable fusion power is within reach; however, more research is needed in the field of material science and engineering. One critical component of a fusion reactor is the plasma facing material. Very little literature exists on the sustainability of tungsten as a plasma facing material (PFM). During operation, PFM must withstand harsh conditions with combined effects from high temperature, mechanical stress, irradiation, transmutation, and the production of hydrogen (H) and helium (He) from nuclear reactions. Therefore, this thesis will focus on co-implantation of H and He into tungsten to investigate the mechanical and microstructural material response.
For the first part of this study, Molecular Dynamics (MD) was used to qualitatively understand defect migration and mechanical property changes in tungsten. A Brinell hardness test was simulated using MD in tungsten to study the dependence on void size and void density hardness. It was found that hardness changes vary as the square root of the void size and void density. Also the movement of dislocations and its interaction with voids were investigated.
For the second part of the study, H and He were co-implanted into tungsten to look at the mechanical and microstructural changes. Hardness changes were measured using a nano-indenter ex-situ on post-irradiated specimen. Results show that the hardness of tungsten after co-implantation is proportional to the square root of the fluence. Additionally, the microstructure of irradiated tungsten samples was investigated by using a Transmission Electron Microscope (TEM). It was observed that the defect microstructure in tungsten, after co-implantation, is quite complex, with a number of intriguing features, such as the presence of the nano-bubbles and dislocation loops. Also it was observed that there was an effect that H has on the nucleation of He nano-bubbles. The results from this work suggest that the effect of co-implanting H and He into tungsten is crucial to fully understand its viability as a PFM.
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LI, YU-WEN, and 李裕文. "The castability and mechanical property of A206 aluminum alloy." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/99320465555648513229.
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Kuo, Yu-Hao, and 郭育豪. "Mechanical Property Control of Heavy Section Ductile Cast Irons." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/nvq6mq.
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碩士國立臺灣大學
機械工程學研究所
105
The primary purposes of this research are two folds: (1) To investigate the effect of Ni on the mechanical properties (tensile strength, yield strength, elongation, hardness, and low-temperature impact value) and microstructures (nodularity, nodule counts and percent pearlite) of heavy-section ductile iron. Based on the experimental results, multiple regression analyses were performed to correlate the mechanical properties with chemical composition and microstructure. (2) To establish the optimal conditions for the production of ductile cast iron inserts for the storage of the spent nuclear fuels through alloy design and manufacturing process control. Furthermore, in this study, the microstructure that occurred in the castings were analyzed and schemes were proposed to eliminate those abnormities, aiming to conform with the specification of EN-GJS-400-15U (T.S.>370MPa, Y.S.>240MPa and El.>7%) for the ductile cast iron inserts. The results of the first part indicate that the addition of Ni to the ductile cast irons can enhance the mechanical properties, i.e., as tensile strength, yield strength, microhardnesses of both ferrite and pearlite phases. However, the effect is affected by other factors, such as the Si and Mn contents, the pearlite (or ferrite) percentage, and the nodule count. The multiple regression analyses were performed to correlate the impact value at various temperatures with the selected metallurgical parameters (percent Ni, percent pearlite, and nodule counts). The results show that the impact value increase with increasing Ni content, and decreasing the percent pearlite and nodule counts. Regarding the trial tests of the reduced-length small scale ductile cast iron inserts, the results of the first attempt fail to conform with the specification due to the presence of chunky graphite in the microstructure, which causes a significant drop in tensile properties. The presence of chunky graphite can be attributed to the excessive amount of Cerium (Ce), especially in heavy section castings. To counteract the adverse effect of Ce, an appropriate amount of antimony (Sb) was added in the second trial. The results of the second trial of the reduced-length small scale ductile cast iron insert can meet the requirement of the specification. Finally, the reduced-length ductile cast iron insert was poured based upon the optimal casting conditions obtained from the first two trials for the reduced-length small scale ductile cast iron inserts. Again, the results fulfill the specification. In addition, the quality indices of all the specimens obtained from the three ductile cast iron inserts, together with the standard grades ductile cast iron, were calculated and compared. The comparisons in quality index can serve as basis for the evaluation of casting performance.
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Cho-LinWang and 王焯林. "Mechanical Property of LARS Artificial Ligament after Tissue Ingrowth." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/39896365895120074085.
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Yu, Chung-Han, and 游京翰. "Measure Mechanical Property of Carbon Nanocoils by AFM Manipulator." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/36820180875545981997.
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碩士國立臺灣大學
機械工程學研究所
96
In this paper, we researched on the carbon nanocoil’s mechanical property by AFM nanomanipulator. The nanocoil were fabricated by CVD with Fe-Sn as catalyst. The Au electrodes were fabricated on SiO2 by photolithography. The gap between electrodes is around 10μm. Then the nanocoils were aligned by electrophoresis. By Au clustering, the nanocoil were fixed on the surface of wafer. As the sample completed, the coil were imaged and manipulated by AFM manipulator. During the experiment, the difference of lateral force can be recorded. By analyzing the change of lateral force, the spring const of nanocoil can be realized. The coil diameter and line diameter were determined by SEM. With spring const, coil diameter, and line diameter, the shear modulus of nanocoil can be calculated. After calculation, the shear modulus of the nanocoil is 2.0~2.6 GPa. During the experiment, we realized the friction between nanocoil and SiO2 surface during moving smaller then the tension of nanocoil.
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Hu, You-Wen, and 胡友文. "A Study on the Mechanical Property ofShape Memory Alloy." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/59309647196687208440.
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碩士大同大學
機械工程學系(所)
94
The shape memory effect of the shape memory alloy (SMA) was driven by its phase transformation caused by temperature change. Previous researches show that the SMA present different stiffness and loading ability under different operating temperature. This study makes assumption as the stiffness of SMA is a function of its temperature. A cantilever beam with SMA was heated by electric current. Then, the load and deflection under different operation temperature of SMA cantilever beam were measured. The results were used to estimate the elastic modulus (E) of the SMA by the cantilever beam deflection formula. A series of experiments were carried out in the study. The experimental results were used to define the relative function between elastic modulus of SMA with temperature by the regression analysis method. Experimental results shown that the elastic modulus of SMA depends on its temperature in the shape transformation range form 100% austenite to 100% martensite. In this phase transformation range and under its elastic limit of shape memory effect range , the relationship of elastic modulus of SMA with temperature is nonlinear. A theoretical expression of elastic modulus of SMA with its temperature was established here.
50
Chen, Ke-yue, and 陳克岳. "Measurement and Analysis on Mechanical Property of Heel Pad." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/08969469526313109089.
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碩士臺灣大學
應用力學研究所
95
This research is to develop a set of mechanical model which can simulate heel pad effectively, and perform the stress relaxation experiment to get the coefficients of constitutive law using the optimization method. Then we get the EDR (energy dissipation ratio) of heel pad by mechanical model, and compare to the experiment result of the non-invasive measurement by the ultrasound . The experiment subjects are two young and non-diabetes men .First we perform the stress relaxation and EDR measurements on them, then compare the hysteresis curves and energy dissipation ratio which are simulated by the mechanical property models to EDR experiment results. The comparison results are 31.05% of experiment value and 29.37% of simulation value for subject A , and 46.27% of experiment value and 38.36%of simulation value for subject B. Finally we build a set of mechanical model which is a series of a nonlinear spring and a nonlinear vogit model to simulate the viscoelastic property of heel pad effectively. As a result, we do not need to perform the non-invasive measurement by the ultrasound to decrease cost and conform to economic benefits. The result shows that when the damping coefficients are smaller, the stress rate decreases faster and EDR becomes higher, and vice verse. When the spring coefficients are smaller, the stress rate decreases faster and the slope of hysteresis curve becomes smaller, and vice verse.