This study first examined the kinetic changes of fiber carboxyl group content in bulk fiber, polysaccharide, and residual lignin of oxygen delignified pulps during one-stage oxygen delignification of a low kappa (32.5) kraft pulp. The carboxyl group contents determined in different chemical components of oxygen delignified pulps was used to establish the distribution of carboxyl groups in lignin and pulp polysaccharide and decouple the responses from residual lignin and polysaccharide. Following this study, two high kappa (~ 49.0) SW kraft pulps prepared were delignified through two-stage oxygen delignification. Fiber carboxyl group profiles of these pulps were elucidated to investigate the effect of lignin content of incoming unbleached kraft pulps on fiber carboxyl group formation. Due to a limitation to enhance fiber carboxyl groups only by parameter optimization during one- and two- stage oxygen delignification, a catalytic oxidation program was developed to enhance fiber carboxyl groups by 52.2 116.0 % employing 0.10 - 0.18% of a bismuth ruthenium pyrochlore oxide catalyst during oxygen delignification. The mechanism of fiber carboxyl group formation through the catalytic oxidation was proposed. The main factor on carboxyl group formation in pulp carbohydrate was identified to follow the order: NaOH > oxygen pressure> reaction temperature through a 3-factor at 3-level (L933) orthogonal experimental design and the optimal conditions were found at 2.5% NaOH, 85-100 oC, and 800-960 kPa O2 during the catalytic oxidation. ECF bleaching study was also conducted on these pulps with higher amount of fiber carboxyl group enhanced at early pulping and oxygen delignification processes. The bleaching results demonstrated that the early-stage enhanced fiber carboxyl groups were partially retained through ECF bleaching. Additionally, fiber carboxyl groups of fully bleached kraft pulps were ~ 20% different from typical bleaching protocols, depending on bleaching chemicals used and the bleaching sequences such as DEDED, (D+C)EDED, ODEDD, and OQPZP. This study finally demonstrated that an increase of fiber carboxyl groups by 17.4-62.1% through chemical oxidation resulted in reduced fiber curl, increased fiber WRVs, 4.3-25.5 % increase in paper tensile index at comparable pulp viscosity; and 4.4 -30.1% increase in paper dry tensile stiffness.

In this research, the amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various conditions such as individual layer thickness, total layer thickness, and interface type have been successfully fabricated by the multi-gun sputtering processes. To investigate the mechanical properties and deformation behaviors of substrate-supported ZrCu/Cu multilayered thin films, these films deposited on the Cu or polyimide foils were prepared for tensile testing. Firstly, the tensile behaviors of the monolithic ZrCu thin film metallic glass and the ZrCu/Cu multilayered thin films deposited on the pure Cu foils are systematically examined. The extracted tensile modulus and strength of the 1-£gm-thick multilayered thin films are in good agreement with the theoretical iso-strain rule of mixture prediction. The extracted 2-£gm-thick multilayered film data are lower, but can be corrected back by considering the actual intact cross-sectional area during the tensile loading. Moreover, the current results reveal that the ZrCu/Cu multilayered coating exhibit much better tensile performance than the monolithic ZrCu coating. It indicates that the amorphous/nanocrystalline multilayered thin film structure can certainly enhance the mechanical properties of monolithic thin film metallic glasses under tension. Secondly, for the further investigation of tensile response, the polyimide-supported amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various individual layer thicknesses from 10 to 100 nm were prepared. The relatively soft, smooth, and flexible polyimide foils as the substrates in this experiment can undergo sufficient deformation under In this research, the amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various conditions such as individual layer thickness, total layer thickness, and interface type have been successfully fabricated by the multi-gun sputtering processes. To investigate the mechanical properties and deformation behaviors of substrate-supported ZrCu/Cu multilayered thin films, these films deposited on the Cu or polyimide foils were prepared for tensile testing. Firstly, the tensile behaviors of the monolithic ZrCu thin film metallic glass and the ZrCu/Cu multilayered thin films deposited on the pure Cu foils are systematically examined. The extracted tensile modulus and strength of the 1-£gm-thick multilayered thin films are in good agreement with the theoretical iso-strain rule of mixture prediction. The extracted 2-£gm-thick multilayered film data are lower, but can be corrected back by considering the actual intact cross-sectional area during the tensile loading. Moreover, the current results reveal that the ZrCu/Cu multilayered coating exhibit much better tensile performance than the monolithic ZrCu coating. It indicates that the amorphous/nanocrystalline multilayered thin film structure can certainly enhance the mechanical properties of monolithic thin film metallic glasses under tension. Secondly, for the further investigation of tensile response, the polyimide-supported amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various individual layer thicknesses from 10 to 100 nm were prepared. The relatively soft, smooth, and flexible polyimide foils as the substrates in this experiment can undergo sufficient deformation under tension. The modulus and strength of the multilayered thin film are again demonstrated to be consistent with the theoretical iso-strain rule of mixture values. As the individual layer thickness decreases from 100 to 10 nm, the Young¡¦s moduli are only varied slightly. However, the maximum tensile stress exhibits a highest value for the 25 nm layer thickness. The higher crack spacing, or the lower crack density, of this 25 nm multilayer film leads to the highest strength. Thirdly, to avoid the stress and strain incompatibility owing to the mismatch of elastic modulus and strength levels from the connected amorphous/nanocrystalline layers, the Cu-supported amorphous/nanocrystalline ZrCu/Cu multilayered thin films with sharp and graded interfaces were successfully sputtered and examined by tensile testing. The extracted tensile properties of the multilayered films can be compared with the predicted values based on the two-phase and three-phase iso-strain rule of mixture model. The multilayered films with graded interfaces, each about 50 nm thick, consistently exhibit higher tensile strength and elongation. This can be rationalized by the reduced stress and strain incompatibility along the interfaces.

Rapid prototyping methods embrace a family of manufacturing methods that are developed to speed up the prototyping stage of product design. The sole needed input for production being the solid model of the part, mold/tool-free production characteristics and the geometric part complexity that can be achieved due to layer-by-layer production have extended the applicability/research areas of these methods beyond prototyping. Local pore formation in part that occurs as a result of the discrete manufacturing nature of rapid prototyping methods can be viewed as an opportunity for material development. In this thesis, the manufacturing-internal (porous) structure-mechanical property relations of porous materials are investigated. These porous parts are produced via Selective Laser Sintering (SLS) which is a rapid prototyping method. The elastic modulus, tensile strength, rupture strength and Poisson&rsquo / s ratio of uniform porous specimens with known porosities are determined through standardized mechanical tests for polymeric materials. The mechanical property variation profiles in graded materials are determined using the mechanical properties of uniform parts. The mechanical behavior of uniform and graded materials under applied loads are modeled using finite element method and simulation results are compared to the results of mechanical tests performed on graded materials. In addition, feasibility of producing resin filled composite parts from these uniform and graded porous parts are sought. Porous parts (both uniformly and graded) that are infiltrated with epoxy resin have been characterized mechanically and the results have been compared with the uninfiltrated porous parts.

Analysis of aircraft structures are mainly performed by assuming that the structure behaves linearly. In linear finite element analysis, it is assumed that deformations are small, thus geometric nonlinearity can be neglected. In addition, linear analysis assumes that linear constitutive laws applicable, implying that material nonlinearity can also be neglected. One very common type of nonlinearity is associated with the boundary conditions. Contact between two deformable bodies or between a deformable and rigid body are typical examples of nonlinearity associated with boundary conditions. Linear structural analysis, in general, does not include contact analysis. Simplicity of linear analysis in terms modeling, interpreting the results and solution time makes the linear analysis approach very convenient in preliminary design and analysis stage of aircraft structures. However, simplicity of linear analysis may result in unconservative results which may occur due to neglecting the true nonlinear behavior of the structure. In this thesis, one such nonlinear eect called prying load eect on the tensile connections is studied. The eect of prying load on structures are initially described by referencing the analytical approaches presented in the literature. Finite element models of typical bolted connections such as L and T type are generated for various combinations of the chosen design parameters such as bolt diameter, flange thickness, washer diameter and edge distances. Parametric modeling approach is used to perform the high number of finite element analysis which involve contact for the purpose of calculating the prying load. Comparative study of the eect of prying load is then conducted by also including the results presented in the literature. Comparisons of the prying load are done with the experimental results presented in the literature. Series of finite element analyses are preformed for various cases such that eect of geometrical variables and bolt preload on prying ratio can be understood. According to the results obtained, it is concluded that main factors eecting the prying ratio are the distance of bolt center to the clip web, flange thickness of the clip and preload on the bolt where the eect of edge distance of the bolt is insignificant.

Quantitative relationships among processing parameters, microstructure, and material properties are of considerable interest in the context of development of robust processing routes that optimize the required material properties. As a result, the scientific literature contains a large number of experimental and theoretical studies on microstructure-properties relationships. Fracture sensitive mechanical properties such as ductility, ultimate tensile strength, fatigue life, and fracture toughness depend on the average microstructural parameters as well as the distributions of microstructural parameters and their extrema.Development of quantitative relationships between such material properties and microstructural distributions and extrema has received considerably less attention, particularly in the wrought metals and alloys. Accordingly, an important objective of this research is to perform a systematic investigation in this direction. The dependence of the fracture-sensitive mechanical properties on the microstructural distributions and extrema often leads to substantial variability in these properties: a set of specimens having the same average chemistry, the same average processing history, and the same average microstructural parameters such as volume fractions of different constituents can exhibit substantially different material properties. The present research (i) is concerned with high strength (~ 1000 MPa) high martensite (>50%) dual phase steel where the martensite is a topologically continuous phase (matrix) containing a dispersion of islands of ferrite, and (ii) focuses on understanding the microstructural origins of the variability in fracture sensitive mechanical properties, in particular variability in the room temperature uniaxial tensile ductility. The research involves quantitative microstructure characterization using stereology and digital image processing and quantitative fractography using scanning electron microscopy (SEM) and fracture profilometry. The analysis of the quantitative fractographic and microstructural data obtained in this research leads to useful guidelines for reducing the variability in the tensile ductility of the dual phase steel under investigation.

<p>Abstract</p><p>The purpose of this research is to investigate the influence of Manganese (Mn) on cast aluminum alloys where a substantial amount of Iron (Fe) is included. Ductility and tensile strength need to be improved in recycled aluminum alloys where greater amounts of Fe are found. Fe is a common impurity and is known to be detrimental to mechanical properties and in order to neutralize the effects of Fe; modifiers such as Mn are added. In this investigation, attempts will be carried out aiming to find the optimal amount of Mn. Other related topics that will be discussed are whether there exists a Mn/Fe ratio which clearly modifies the harmful iron- rich phases and improves the properties for a certain alloy or not. Also, will the heat treatment have a significant effect on mechanical properties? These are some of the questions that will be answered in this paper.</p><p>It is hard to find research articles that focus only on the influence of Mn on the microstructure and mechanical properties of Al-Si cast alloys. Much of the work that is already published concerns only a specific alloy and casting method. In this work three different casting processes, sand-, die- and high pressure die-casting, will be simulated by using gradient solidification equipment. Furthermore, the influence of heat treatment on the mechanical properties will be examined.</p><p>The results showed that the solidification rate had the biggest impact on the microstructure and mechanical properties of the alloys, where the fastest cooling rate gave the best results. The effect of Mn seems to influence the samples with coarser microstructures significantly where it had time to modify the Iron-rich needles, also called the β-phase. At higher cooling rates the impact of Mn was impeded. It has been observed that a high content of Mn (around 0.6%) needs to be added before the properties start to improve. UTS (Ultimate Tensile Strength) and YS (Yield Strength) are improved while ductility is lowered. Heat treatment did not seem to have any influence on the effects of Mn.</p>

No description available.

In this thesis, the Mechanical properties of polypropylene yarn of outer protection layer on Submarine High Voltage Cable, twisted around submarine cable,is determined on various conditions at ABB Company. In the first step, tensile tests are done with polypropylene yarn specimens with and without Bitumen at Room temperature. In the second step,tensile tests are done with polypropylene yarn specimens with and without Bitumen and with knotted polypropylene yarn namely: the Fishermen’s knot, the Weaver’s knot, the Square knot and the Overhand knot at Warm Condition (60˚c) and Cold Condition(-5˚c). In the final step,it is proposed to obtain numerical solution using FEM analysis with ABAQUS Software to obtain the hoop stress , the yarn stresses from twisting cable and analyzing of the cylindrical buckling in the buckling torsion and buckling bending on the outer layer of submarine cable with polypropylene material that is mixed with Bitumen.

Synthesis of high molar mass polycarbonate polyurethanes using a novel polyol is described. The resulting elastomers demonstrate excellent mechanical properties as well as the capability to re-heal after rupture without the addition of additives or imbedded healing agents. The self-healing functionality is shown to greatly improve with the addition of up to 1% single and multi-walled carbon nanotubes. The interface of the carbon nanotubes and self-healing polymer are probed using Raman techniques and provide an insight into how the self-healing actions are improved with the addition of carbon nanotubes. Synthesis of polycarbonate polyurethanes and carbon nanotube composites using a novel casting method is described and compared to the more traditional solution casting method. The dispersion of the carbon nanotubes is evaluated as well as the effect of effective dispersion on the composites through tensile testing, rheometry and hardness testing. Although complete agglomeration avoidance could not be achieved, significant size decrease was observed. Over 200% improvement in tensile strength is shown with conventional solution casting method which is further improved by the described novel solution casting method. Contact angle measurements on our novel self-healing poly (carbonate urethane) and CNTs composites show that surface energies are drastically changed when CNTs are used. The most revealing finding is that f×svp increases in CNT composite materials from ~30% of the surface energy on average for the samples tested, to ~80%. We have shown that surface free energies increase most likely as a result of exposing hydrogen bonding sites typically found within the bulk in polyurethanes. Our polyurethane differs from traditional polyurethanes in that it has both novel soft segments made from a novel polycarbonate polyol discussed in chapter 2 and relatively soft ¡§hard¡¦ segments resulting from the use of H12MDI, all leading to increased ability to hydrogen bond within the material. The availability of the hydrogen bonding sites is demonstrated by FTIR absorbance bands for associated and unassociated hydrogen bonding sites, which do not seem to be accessible to a large until the PCPU¡¦s surface is disrupted. Once disrupted, the exposed hydrogen bonding sites are able to bond with other bonding sites of adjacent ruptured surfaces. This would explain why our material is non-blocking, e.g. won¡¦t stick to itself, until the surface is ruptured. It would also explain why any two ruptured surfaces of our material will reheal, even if they were not attached previously.

The objectives of the research are to establish the process of obtaining regenerated fibers and films from wood pulp and bagasse pulp with the ionic liquid 1-Butyl-3-methylimidazolium Chloride (BMIMCl) as a solvent; to study the impacts on tensile strength of different spinning parameters; to find the optimal spinning condition, and to obtain regenerated cellulose products with flame retardant properties. Solutions were obtained by dissolving cellulose (wood/bagasse) pulp into the BMIMCl. The solutions were extruded in a dry-jet and wet-spinning method using water as a coagulation bath. The obtained fibers were tested to evaluate the properties such as tensile strength, thermal property, thermal mechanical property, crystal order, and ionic liquid residue in obtained fiber. The orthogonal experiments were designed to find out the strongest affective variable and the optimal condition of the spinning process. The regenerated cellulose films with melamine resin or zinc oxide were obtained. Their flame retardant properties were tested. Cellulose fiber with melamine resin was also obtained. Thermo-gravimetric analyzer (TGA) was used to measure the thermal properties of obtained products, and to calculate their activation energies. Dynamic mechanical analysis (DMA) was used to determine the thermal mechanical properties of obtained fibers. Wide angle X-ray diffraction (WAXD) was used to measure the degree of crystallinity and degree of crystal orientation. The tensile strength was tested by a tensile machine. To evaluate the quantity of ionic liquid residue in the regenerated fibers, the instrumental methods of FT-IR and Mass Spectrometry were applied. Research results indicated increases in the degree of crystallinity and storage modulus under a higher fiber drawing speed. Both regenerated bagasse fibers and regenerated wood fibers had similar thermal properties. However, the regenerated bagasse fibers showed a higher degree of crystallinity and a higher tenacity than the regenerated wood fibers obtained under the same condition. The study also revealed water treatment would be helpful for eliminating the ionic residue in regenerated fibers. It was also found the concentration of cellulose in the BMIMCl solution affected the tensile strength of regenerated fiber mostly. Certain amount of melamine or zinc oxide nanoparticles contained in the cellulose matrix could improve the flame retardant property effectively. / text