Dissertations / Theses on the topic 'Plastic engineering (Engineering)'
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LINDSTRAND, NILS, and KARL THUNELL. "From Plastic to Paper Mapping the real cost of plastics." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224931.
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Kang, JiJun. "Determination of elastic-plastic and visco-plastic material properties from instrumented indentation curves." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13509/.
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Instrumented indentation techniques at micro or nano-scales have become more popular for determining mechanical properties from small samples of material. These techniques can be used not only to obtain and to interpret the hardness of the material but also to provide information about the near surface mechanical properties and deformation behaviour of bulk solids and/or coating films. In particular, various approaches have been proposed to evaluate the elastic-plastic properties of power-law materials from the experimental loading-unloading curves. In order to obtain a unique set of elastic-plastic properties, many researchers have proposed to use more than one set of loading-unloading curves obtained from different indenter geometries. A combined Finite Element (FE) analysis and optimisation approach has been developed, using three types of indenters (namely, conical, Berkovich and Vickers), for determining the elastic-plastic material properties, using one set of ‘simulated’ target FE loading-unloading curves and one set of real-life experimental loading-unloading curves. The results obtained have demonstrated that excellent convergence can be achieved with the ‘simulated’ target FE loading-unloading curve, but less accurate results have been obtained with the real-life experimental loading-unloading curve. This combined technique has been extended to determine the elastic and visco-plastic material properties using only a single indentation ‘simulated’ loading-unloading curve based on a two-layer viscoplasticity model. A combined dimensional analysis and optimisation approach has also been developed and used to determine the elastic-plastic material properties from loading-unloading curves with single and dual indenters. The dimensional functions have been established based on a parametric study using FE analyses and the loading and linearised unloading portions of the indentation curves. It has been demonstrated that the elastic-plastic material properties cannot be uniquely determined by the test curves of a single indenter, but the unique or more accurate results can be obtained using the test curves from dual indenters. Since the characteristic loading-unloading responses of indenters can be approximated by the results of dimensional analysis, a simplified approach has been used to obtain the elastic-plastic mechanical properties from loading-unloading curves, using a similar optimisation procedure. It is assumed that the loading-unloading portions of the curves are empirically related to some of the material properties, which avoids the need for time consuming FE analysis in evaluating the load-deformation relationship in the optimisation process. This approach shows that issues of uniqueness may arise when using a single indenter and more accurate estimation of material properties with dual indenters can be obtained by reducing the bounds of the mechanical parameters. This thesis highlights the effects of using various indenter geometries with different face angles and tilted angles, which have not been covered previously. The elastic-plastic material parameters are estimated, for the first time, in a non-linear optimisation approach, fully integrated with FE analysis, using results from a single indentation curve. Furthermore, a linear and a power-law fitting scheme to obtain elastic-plastic material properties from loading-unloading indentation curves have been introduced based on dimensional analysis, since there are no mathematical formulas or functions that fit the unloading curve well. The optimisation techniques have been extended to cover time-dependent material properties based on a two-layer viscoplasticity model, has not been investigated before.
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Huss, Fredrik R. M. "In vitro and in vivo studies of tissue engineering in reconstructive plastic surgery." Doctoral thesis, Linköpings universitet, Brännskadevård, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8504.
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To correct, improve, and maintain tissues, and their functions, are common denominators in tissue engineering and reconstructive plastic surgery. This can be achieved by using autolo-gous tissues as in flaps or transplants. However, often autologous tissue is not useable. This is one of the reasons for the increasing interest among plastic surgeons for tissue engineering, and it has led to fruitful cross-fertilizations between the fields. Tissue engineering is defined as an interdisciplinary field that applies the principles of engineering and life sciences for development of biologic substitutes designed to maintain, restore, or improve tissue functions. These methods have already dramatically improved the possibilities to treat a number of medical conditions, and can arbitrarily be divided into two main principles: > Methods where autologous cells are cultured in vitro and transplanted by means of a cell suspension, a graft, or in a 3-D biodegradable matrix as carrier. > Methods where the tissue of interest is stimulated and given the right prerequisites to regenerate the tissue in vivo/situ with the assistance of implantation of specially designed materials, or application of substances that regulate cell functions - guided tissue regeneration. We have shown that human mammary epithelial cells and adipocytes could be isolated from tissue biopsies and that the cells kept their proliferative ability. When co-cultured in a 3-D matrix, patterns of ductal structures of epithelial cells embedded in clusters of adipocytes, mimicking the in vivo architecture of human breast tissue, were seen. This indicated that human autologous breast tissue can be regenerated in vitro. The adipose tissue is also generally used to correct soft tissue defects e.g. by autologous fat transplantation. Alas 30-70% of the transplanted fat is commonly resorbed. Preadipocytes are believed to be hardier and also able to replicate, and hence, are probably more useful for fat transplantation. We showed that by using cell culture techniques, significantly more pre-adipocytes could survive and proliferate in vitro compared to two clinically used techniques of fat graft handling. Theoretically, a biopsy of fat could generate enough preadipocytes to seed a biodegradable matrix that is implanted to correct a defect. The cells in the matrix will replicate at a rate that parallels the vascular development, the matrix subsequently degrades and the cell-matrix complex is replaced by regenerated, vascularized adipose tissue. We further evaluated different biodegradable scaffolds usable for tissue engineering of soft tissues. A macroporous gelatin sphere showed several appealing characteristics. A number of primary human ecto- and mesodermal cells were proven to thrive on the gelatin spheres when cultured in spinner flasks. As the spheres are biodegradable, it follows that the cells can be cultured and expanded on the same substrate that functions as a transplantation vehicle and scaffold for tissue engineering of soft tissues. To evaluate the in vivo behavior of cells and gelatin spheres, an animal study was performed where human fibroblasts and preadipocytes were cultured on the spheres and injected intra-dermally. Cell-seeded spheres were compared with injections of empty spheres and cell suspensions. The pre-seeded spheres showed a near complete regeneration of the soft tissues with neoangiogenesis. Some tissue regeneration was seen also in the ‘naked’ spheres but no effect was shown by cell injections. In a human pilot-study, intradermally injected spheres were compared with hyaluronan. Volume-stability was inferior to hyaluronan but a near complete regeneration of the dermis was proven, indicating that the volume-effect is permanent in contrast to hyaluronan which eventually will be resorbed. Further studies are needed to fully evaluate the effect of the macroporous gelatin spheres, with or without cellular pre-seeding, as a matrix for guided tissue regeneration. However, we believe that the prospect to use these spheres as an injectable, 3D, biodegradable matrix will greatly enhance our possibilities to regenerate tissues through guided tissue regeneration.On the day of the defence date the status of article V was In Press.
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Toor, A. P. S. "Biaxial cyclic plastic bending." Thesis, Coventry University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372393.
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Fredriksson, Camilla. "Keratinocytes in tissue engineering of human skin: invitro and in vivo studies." Licentiate thesis, Linköping University, Linköping University, Plastic Surgery, Hand Surgery and Burns, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-21283.
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Full thickness wounds, such as deep burns, need restoration of both the dermal and epidermal layers of the skin. In normal wound healing, re-epithelialization occurs by migration and proliferation of keratinocytes from the wound edges and by differentiation of stem cells from remaining hair follicles. Restoration of dermis occurs by influx of growth factors secreted by macrophages, platelets, and fibroblasts; by fibroblast proliferation and subsequent synthesis and remodeling of collagenous dermal matrix. In the case of full-thickness acute burn injuries and chronic wounds (e.g. pressure ulcers, venous ulcers and diabetic foot ulcers), these processes are defective. With the principles of tissue engineering in mind (to correct, improve and maintain tissues and their functions), researchers have developed promising materials and methods to make it possible to restore either the dermal (Integra® DRT, Alloderm®) or the epidermal layer (split thickness skin grafts (STSG), cultured epithelial autografts (CEA), autologous keratinocytes in single cell suspension). It is now well established that superior results are obtained if both dermal and epidermal components are combined, for example in a bilayered skin equivalent. Apligraf® is recommended for use on venous ulcers and is the only bilayered living skin equivalent currently approved by the FDA. Studies on different factors affecting the wound healing capacity as well as techniques in use provide valuable information for further development.
In this licentiate thesis, we evaluated different transplantation techniques for delivering cultured human keratinocytes in single cell suspension, a measure becoming more frequently used in addition to STSG and CEA for restoring the epidermal layer of the skin. We found that the pressure device, commonly used to spray cell suspension onto the wound with pressures as high as 200 kPa, killed around 0% of the cells. In comparison, an ordinary syringe with the attachment of a spray nozzle showed almost 90% viable cells post transplantation and provided an equally good distribution of the cell suspension.
We also studied different silver containing dressings regarding silver accumulation in human skin. In addition, we graded the re-epithelialization to evaluate whether the dressings caused any delay in the wound healing process. We found that the silver dressings tested, with few exceptions, caused dermal accumulation of silver, primarily aggregated around blood vessels. We could also show that most of the dressings had negative effect on the re-epithelialization.
For the restoration of the dermal layer of the skin, Integra® DRT functions as a scaffold for guided tissue regeneration of the dermis. We had the possibility to study a case of necrotizing fasciitis were the treatment consisted of the use of Integra® DTR together with sub-atmospheric pressure (after initial surgical debridement) and later transplantation of split thickness skin grafts. This measure proved to be safe as well as giving satisfactory pliable and aesthetically acceptable result.
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Sayahi, Faez. "Plastic Shrinkage Cracking in Concrete." Licentiate thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-133.
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Early-age (up to 24 hours after casting) cracking may become problematic in any concrete structure. It can damage the aesthetics of the concrete member and decrease the durability and serviceability by facilitating the ingress of harmful material. Moreover, these cracks may expand gradually during the member’s service-life due to long-term shrinkage and/or loading. Early-age cracking is caused by two driving forces: 1) plastic shrinkage cracking which is a physical phenomenon and occurs due to rapid and excessive loss of moisture, mainly in form of evaporation, 2) chemical reactions between cement and water which causes autogenous shrinkage. In this PhD project only the former is investigated. Rapid evaporation from the surface of fresh concrete causes negative pressure in the pore system. This pressure, known as capillary pressure, pulls the solid particles together and decreases the inter-particle distances, causing the whole concrete element to shrink. If this shrinkage is hindered in any way, cracking may commence. The phenomenon occurs shortly after casting the concrete, while it is still in the plastic stage (up to around 8 hours after placement), and is mainly observed in concrete elements with high surface to volume ratio such as slabs and pavements. Many parameters may affect the probability of plastic shrinkage cracking. Among others, effect of water/cement ratio, fines, admixtures, geometry of the element, ambient conditions (i.e. temperature, relative humidity, wind velocity and solar radiation), etc. has been investigated in previous studies. In this PhD project at Luleå University of Technology (LTU), in addition to studying the influence of various parameters, effort is made to reach a better and more comprehensive understanding about the cracking governing mechanism. Evaporation, capillary pressure development and hydration rate are particularly investigated in order to define their relationship. This project started with intensive literature study which is summarized in Papers I and II. Then, the main objective was set upon which series of experiments were defined. The utilized methods, material, investigated parameters and results are presented in Papers III and IV. It has been so far observed that evaporation is not the only driving force behind the plastic shrinkage cracking. Instead a correlation between evaporation, rate of capillary pressure development and the duration of dormant period governs the phenomenon. According to the results, if rapid evaporation is accompanied by faster capillary pressure development in the pore system and slower hydration, risk of plastic shrinkage cracking increases significantly.
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Donkin, Richard Philip. "Plastic photovoltaic roof tiles." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/4397.
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Thesis presented in partial fulfilment of the requirements for
the degree of Master of Engineering in Renewable and
Sustainable Energy at the Stellenbosch University.Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: This project investigated the feasibility of incorporating photovoltaic cells into plastic roof tiles using injection moulding. Such tiles have the potential to provide robust and distributed electricity contained within the building envelope. Current-voltage curves of amorphous silicon modules were measured under illumination using the PVPM 2540C power measuring instrument, both before and after moulding. The efficiency after moulding was reduced by 53% to 88%, with modules that were heated for longer being degraded more. Thus the duration of exposure to high temperatures affected the extent of performance reduction during moulding. This suggested that faster moulding at a lower temperature or faster cooling could solve the problem. Economic feasibility was examined by calculating the levellised cost of electricity provided by the tiles. A large-scale development in the Western Cape was simulated using a typical meteorological year of weather data and using the anisotropic diffuse irradiance model of Perez et al. (1988). Avoided costs due to replaced roofing, avoided costs due to electricity distribution infrastructure, and Clean Development Mechanism credits were accounted for. The cost of energy calculated was R11/kWh in 2010 rands, which did not compete with the price of conventional grid-based electricity at R1.8/kWh. The importance of the cost of balance-of-system components, such as the inverter, and not only of the photovoltaic modules, was highlighted for future cost reductions. Several clear guidelines for manufacturing photovoltaic roof tiles were discovered. The most important of these was that many bypass diodes make the system more robust.
AFRIKAANSE OPSOMMING: Hierdie projek het die haalbaarheid van die integrasie van fotovoltaïse selle in plastiek dakteëls deur spuitvorming ondersoek. Sulke dakteëls het die vermoë om robuuste en verspreide elektrisiteit te lewer, sonder om die gebou se vorm te verander. Stroom-spanning kurwes van struktuurlose silikon eenhede is onder verligting gemeet met die PVPM 2540C kragmeet instrument, voor en na spuitvorming. Die doeltreffendheid na spuitvorming is met 53% tot 88% verminder, met groter vermindering in die eenhede wat langer warm was. Dus het die duur van blootstelling aan hoë temperature die mate van vermindering van doeltreffendheid beïnvloed. Dit het suggereer dat óf vinniger spuitvorming by laer temperature óf vinniger verkoeling die probleem kan oplos. Ekonomiese haalbaarheid is ondersoek deur die koste van die elektrisiteit wat deur die dakteëls gelewer is te bereken. ’n Groot behuisingsontwikkeling in die Wes-Kaap is gesimuleer deur ’n tipiese weerkundige jaar van weerdata en die anisotroop model vir verspreide ligstraling van Perez et al. (1988) te gebruik. Vermyde kostes van vervangde dakteëls, vermyde kostes van elektrisiteit distribusie infrastruktuur en krediete van die Meganisme vir Skoonontwikkeling is in ag geneem. Die elektrisiteitskoste was R11/kWh in 2010 se randwaarde, wat nie mededingend met die R1.8/kWh koste van gewone netwerk elektrisiteit was nie. Die belang van die kostes van die res van die installasieonderdele, soos die wisselrigter, en nie net die fotovoltaïse eenhede nie, is beklemtoon vir kostevermindering in die toekoms. Verskeie duidelike riglyne vir die vervaardiging van fotovoltaïse dakteëls is voorgestel. Die belangrikste van hierdie was dat meer omloopdiodes die installasie meer robuust maak.
Centre for Renewable and Sustainable Energy Studies
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Derradji-Aouat, Ahmed. "Evaluation of Prevost's elasto-plastic models." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5545.
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Nowzartash, Farhood. "Elasto-plastic finite element for pipelines." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6180.
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An efficient pipe element for the modeling of the inelastic behaviour of three-dimensional pipes is presented. The formulation is based on a two-node element with twelve degrees of freedom. The element consists of an elastic portion and two potentially plastic generalized 3D hinges located at both nodes. The formulation is based on a lumped plasticity approach. The behaviour of plastic hinges is characterized using recently developed interaction relations for pipe sections. The interaction relations are exact and include the effects of axial force, bi-axial bending moments, bi-axial shear, torsion and internal and/or external pressure. The element models shear deformation effects both in the elastic and plastic ranges. Therefore, it is suitable for predicting the behaviour of pipe segments subject to high shear forces. The analysis is implemented using the displacement control scheme in order to capture the peak point of the load deformation response without numerical difficulty. The normality condition concept in conjunction with the yield hyper-surface at stress resultant level is used to approximately simulate the material nonlinearity effects. The developed technique models material nonlinearity in a very efficient way when compared to full 3D or shell finite element analysis. The model is thus particularly suitable for long pipeline systems. Solutions for simple problems are provided and compared to several other well-established elements in the ABAQUS(TM) library in order to assess the validity of the results and demonstrate their scope of applicability. A discussion of additional features that can be added to the analysis is also presented.
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Li, Wing-Jin [Verfasser], Lars Mathias [Akademischer Betreuer] Blank, and Nick [Akademischer Betreuer] Wierckx. "Plastic monomer degradation - Engineering Pseudomonas putida KT2440 for plastic monomer utilization / Wing Jin Li ; Lars M. Blank, Nick Wierckx." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1217256997/34.
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Henke, Douglas J. (Douglas John). "Elastic-plastic hull plate response to slamming induced pressures." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/39969.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1992 and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992.Includes bibliographical references (leaves 76-78).
by Douglas J. Henke.
M.S.
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Huss, Fredrik. "In vitro and in vivo studies of tissue engineering in reconstructive plastic surgery /." Linköping : Univ, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/med905s.pdf.
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Alcazar, Jorba Daniel. "A conjugated polymer plastic gel." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45359.
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Includes bibliographical references (p. 107-119).Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
We present a gel route to process highly oriented conjugated polymer films and fibers. The incorporation of hexafluoroisopropanol, a strong and stable dipolar group, to the polythiophene backbone enhances the solubility and especially, the hydrogen bond forming capabilities of the polymer. This functionalization enables the polymer to build up an isotropic self-supporting network structure based on a combination of polymer-polymer chain interactions and interchain hydrogenbondings. These thermally reversible physical crosslinks incorporate plasticity in the conjugated polymer gel. The gel network can be melted and then transformed via mechanical deformation to form an anisotropic gel with the chains highly aligned along the tensile direction. The oriented gel morphology comprises a distribution of crystalline clusters in an overall swollen network. In these ordered regions, conjugated backbones are [pi]-stacked with respect to each other neighbors. The mechanically induced structural rearrangement from an isotropic to an anisotropic conjugated polymer gel occurs when transitioning from the molten state to the gel state. This study highlights the versatility of incorporating plasticity in the design of conjugated polymer materials via a gel processing technology and its potential for applications.
by Daniel Alcazar Jorba.
M.Eng.
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Uranukul, Boonsom. "Engineering of Saccharomyces cerevisiae for renewable production of plastic precursor chemicals from plant biomass." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122531.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references.
Currently, plastics are almost exclusively produced from feedstocks derived from crude oil refining and natural gas processing. Despite the increasing awareness of the negative environmental and climate-related impacts associated with fossil fuel consumption, the relevance of fossil fuels has held steady as a result of the recent proliferation of plastics industry. The recent growing attempts to replace conventional petroleum-based production processes with renewable direct bioconversion processes, however, have not yet been made successful due to low production efficiency. Here, we studied the development of a bioprocess for the renewable production of monoethylene glycol (MEG), a precursor chemical of polyethylene terephthalate (PET) plastics, by using yeast Saccharomyces cerevisiae as biosynthesis platform. During the process, we found evidence for the existence of an endogenous biosynthetic route for MEG production from D-xylose in S. cerevisiae.
Based on the discovered biosynthetic pathway, we then demonstrated the implementation of metabolic engineering and fermentation operational strategies that led to an overproduction of MEG, as well as improved strain performance during prolonged bioreactor cultivation. Using the MEG bioconversion process as the starting point, we developed another bioprocess which allowed direct conversion of D-xylose to glycolic acid, a chemical precursor of polylactic-co-glycolic acid (PLGA). Furthermore, we investigated the biosynthesis of 1,4- butanediol, a chemical precursor of thermoplastic engineering polymer polybutylene terephthalate (PBT), in S. cerevisiae. In all of these studies, ethanol fermentation emerged as an important limitation that negatively affected the efficiency of the yeast-based processes. Our attempts to disrupt ethanol fermentation, while successfully reducing ethanol production, led to a compromise in MEG production. An analysis on the energetics of our engineered S.
cerevisiae, revealed that ethanol fermentation might, in fact, be a necessary requirement for maintaining the energy balance in certain systems, including the biosynthesis of MEG. These findings provide some insights as well as a better understanding of Saccharonyces cerevisiae as the microbial cell factory for the biosynthesis of small molecules other than ethanol.
by Boonsom Uranukul.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering
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Zywicz, Edward. "On elastic-plastic cracks between dissimilar media." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14401.
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Kim, Yun-Jae. "Modeling fully plastic, plane strain crack growth." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12223.
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Werkmeister, Jaime Brooke 1977. "Development of silicon insert molded plastic (SIMP)." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32395.
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Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 85-86).
As demand for smaller devices continues to increase, current manufacturing processes will find it more challenging to meet cost, quantity, and dimensional requirements. While microfabrication technology processes can create electronic devices in vast quantities with increasingly smaller dimensions, they are challenged to do so for mechanical devices at low cost and in large quantity. More traditional manufacturing processes such as machining or injection molding can more easily meet cost and quantity requirements, but are unable to currently match the dimensional abilities of microfabrication processes. By merging microfabrication and traditional injection molding techniques, the benefits of both technologies can be combined to produce parts to meet all three requirements. The objective of this research is to investigate the possibilities of injection molding polymer parts with sub-micron three-dimensional features using a process called Silicon Insert Molded Plastics (SIMP).
by Jaime Brooke Werkmeister
Mech.E.
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Liauwnardi, Leonard. "Plastic gear transmission error measurements and predeictions." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407243719.
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Wu, Xijia. "Constitutive laws of plastic deformation and fracture." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7821.
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Environment assisted fatigue involves plastic deformation and degrading chemical reactions, which occur in a localized region ahead of the crack tip. Basically, transgranular crack growth proceeds by alternating slip processes. In this study, a transgranular fatigue crack growth rate model is developed on the basis of restricted slip reversibility (RSR), where transgranular fatigue crack growth rate is related to plastic deformation accommodation ahead of the crack tip (the product of the cyclic plastic strain range and the plastic zone size). The model is shown to take the form of the Paris equation with a power law exponent of 3 at positive R values. Fatigue crack growth behavior of a 8090 aluminum-lithium alloy has been examined by a series of tests using compact tension (C(T)) specimens with the load axis (a) parallel to the rolling direction (LT specimen), (b) inclined at 15$\sp\circ$ (L + 15$\sp\circ$), (c) inclined at 30$\sp\circ$ (L + 30$\sp\circ$), (d) inclined at 45$\sp\circ$ (L + 45$\sp\circ$) to the rolling direction. It has been found that in the LT, L + 15$\sp\circ$ and L + 30$\sp\circ$ specimens macroscopic cracks propagate along the plane normal to the rolling direction regardless of the deviation of loading directions and the fatigue crack in the L + 45$\sp\circ$ specimen propagates along the plane of specimen symmetry. Fatigue crack growth rate has been found to vary with the specimen orientation with the LT direction exhibiting the best fatigue crack growth resistance. These phenomena are discussed in terms of the crystallographic texture and the highly planar slip behavior of this ally. A revised RSR model is developed for the description of transgranular fatigue crack growth in aluminum-lithium alloys, where the effect of texture is related to a geometric factor for the favorable slip planes. Extension of the RSR model to environment assisted fatigue is also discussed. It is recognized that environmental effects contribute to crack propagation by the formation and rupture of an embrittlement zone in front of the crack tip. By incorporating a corrosion damage zone into the RSR model, fatigue crack growth rate in a deleterious environment is shown to be consists of two components: (i) mechanical fatigue which occurs by partially reversible slip and (ii) environmental enhancement of crack growth that results from the rupture of the embrittlement zone and is directly related to the characteristic dimension of this corrosion damage zone. In addition, fracture kinetics analysis is extended to crack growth behavior which exhibits the positive-negative temperature dependence. A constitutive law is derived from the general rate equation for a two-barrier consecutive system which represents stress corrosion cracking. The transition condition of the positive-negative temperature dependence is discussed and defined in terms of microstructural characteristic quantities (activation energy and work factor) and loading constraints (stress intensity factor and temperature). For the description of plastic deformation, a set of evolutionary rate equations is developed from deformation kinetics theory. Corresponding constitutive equations are derived for the dislocation glide mechanism, glide-plus-climb mechanism and diffusional flow. The operational equations are solved from the governing differential rate equation to determine deformation responses under different loading constraints.
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Wadstein, Victor. "Circular Economy in Plastic Production : The recycling challenges and solutions in plastic production." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264551.
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The consequences of the linear economy of plastic production has started to show. Media reports of "plastic seas," beaches full of waste, and habitats and environments destroyed. The question on how to make plastic production more circular have been a hot topic. Every year 311 million tonnes of plastic gets produced around the world. The plastics that can be recycled are thermoplastics. 70% of all produced plastic is made from five different plastic materials, PVC, PET, EPS, PP, and HDPE. Of the total of 311 million tonnes 87 million tonnes of that plastic is plastic packages for household consumers. Of that 87 million tonnes 32% of that is never collected, ending up in the oceans. Sweden is doing well compared to most countries, 99% of all plastic in Sweden is collected. The number is much thanks to all the regulations, recycling organs, and producer requirements that are active in Sweden compared to many other countries. This report is going to point out some important challenges and its solutions to move towards a globally circular economy. Sweden still faces challenges. Of all plastic collected only 50% goes into recycling while the other 50% ends up for incineration to energy recovery, to warm up houses and give electricity to cities. There are four different methods of recycling in facilities today. Closed - loop Open - loop Chemical recycling Energy recovery through incineration Closed - loop recycling is when the recycled product ends up as the same product after the recycling process while open - loop is when something gets recycled to a plastic product with a lower value than the original product. Chemical recycling is when chemicals in the plastic are extracted and recycle these, usually for fuels. Energy recovery through incineration is when plastic waste is burnt down to recover the energy stored in the plastic. The most common recycling methods in Sweden are open-loop recycling and energy recovery through incineration. One plastic container differs from the rest. The PET - bottles. Of all plastic bottles 85% are collected and recycled in Sweden much thanks to the deposit-refund system available in Sweden. Plastic bottles often follow a process called URRC process, which is a full process from collecting plastic bottles to selling clean plastic flakes that can be renewed to new plastic bottles. Sweden is building the largest recycling facility in Europe, with a technology called "Near-echnology" which is a technology with Near-infrared light to efficiently sort out coloured and clear plastic as well as type of material and chemical compound. This technology will help the facility sort out more than 50% plastic waste compared to other facilities in Europe, an essential step toward a circular economy. Another meaningful action is in the form of global and international producer recommendations, where strict regulation regarding production, design, and materials are agreed upon that favours packaging improving its recycling abilities. These regulations come from the recycling companies such as Returpack and Plastkretsen.Konsekvenserna från en linjär ekonomi inom plastproduktion har börjat att visas. Media rapporterar om "plast hav", stränder fulla med avfall med habitat och miljöer förstörda. Frågan hur man kan göra plastproduktionen mer cirkulär har varit ett hett debatterat ämne. Varje år produceras 311 miljoner ton plast runt om i världen. Plasten som idag går att återvinna kallas Termoplaster. Av de plasterna består 70% av dessa olika plastmaterial, PVC, PET, EPS, PP och HDPE. Av all tillverkad plast är 78% miljoner ton plastförpackningar varav 32% av det som tillverkas hamnar i haven. Sverige sköter sig bättre än många andra länder när det gäller uppsamling av plast plockas 99% upp. Denna siffra är mycket tack vare de lagar, förordningar och återvinning organ som existerar i Sverige jämfört med andra länder. Detta arbete kommer att fokusera på de utmaningar som uppkommer när man ska röra sig mot en mer cirkulär ekonomi och de lösningar som finns för att klara av utmaningarna. Sverige står för ett antal utmaningar. Av all plast som samlas in i Sverige går 50% till återvinning av materialet medan 50% går till förbränning för att få ut energi, för att värma hus och generera energi till städerna. De fyra vanligaste metoderna som används i återvinning av plast idag är. Closed - loop Open - loop Kemisk återvinning Förbränning för energi Closed - loop är en återvinningsmetod som betyder att när en produkt återvinns kommer den komma ur cykeln som samma eller liknande produkt, detta kan jämföras med open - loop där produkten återvinns till ett material med sämre kvaliteter. I kemisk återvinning återvinner man kemikalierna i plasten. Vanligt är att utvinna kemikalier för att sedan använda som olika bränslen. Den sista vanligaste metoden är förbränning av plast för att få ut energin som finns lagrad i plasten. De vanligaste metoderna i Sverige är idag open - loop samt förbränning. En typ av plastförpackning skiljer sig dock mot mängden, PET - flaskor. Av alla flaskor återvinns 85% till en ny plastprodukt. Detta är mycket beroende på det välfungerande pantsystem som finns i Sverige. Insamlade plastflaskor följer i Sverige en process som heter URRC - processen. Denna process följer allt från insamling av plastflaskor till försäljning av klara plastflingor som kan återvinnas till bland annat flaskor. Sverige bygger även Europas största återvinningscentral för plastinsamling. Med en ny teknologi som de kallar "Near- Technology" som bygger på Near - infrarött ljus´ skall öka precisionen på sortering av plasten. Från material, färg och kemisk uppsättning. Potentialen är 50% mer sorterad plast än någon annan anläggning i Europa. Andra nödvändiga åtgärder för att skapa en cirkulär ekonomi är i form av strikta förordningar, skärpa lagar och att plastproducenter följer de rekommendationer som kommer från till exempel, Returpack och Plastkretsen.
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Marcus, Miranda. "Theory Driven Engineering Model to Predict Ultrasonic Weld Strength of Plastics." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1605556381223829.
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Ruan, Haihui. "Collision between two perfectly plastic beam structures : modeling and verification /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?MECH%202004%20RUAN.
Full textAbstract:
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 235-241). Also available in electronic version. Access restricted to campus users.
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Bahous, André. "Plastic buckling of circular plates on elastic foundations." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123016.
Full textAbstract:
The thesis deals with the plastic bifurcation buckling of a full circular plate partially or fully bonded to an elastic foundation, and subjected to a uniform radial pressure at the periphery. The prebuckling state of stress in the plate is therefore a constant equibiaxial stress. Under this stress, the plate material undergoes strain-hardening, obeying an isotropically expanding J2 (von Mises) yield surface. The incremental constitutive relations, needed for the bifurcation analysis, are written in a way so as to incorporate behaviours according to both the J2 deformation and J2 -incremental theories of plasticity, and also to include the elastic theory. The governing equation and boundary conditions, suitable for non-axisymmetric or axisymmetric buckling, are derived using the principle of virtual work and Shanley's concept of bifurcation under increasing load. Exact analysis solves the fourth order partial differential equation, and obtains the buckling stresses for plates fixed and simply supported at the periphery, as a function of the radius to thickness ratio, and for various values of the foundation modulus.Four cases of foundation support are considered: (1) no foundation, (2) full foundation, (3) partial inside foundation for half the plate radius, and (4) partial outside foundation from half to the full radius. This is done for fixed as well as simply supported plates. Buckling stresses and the associated mode shapes, whether axisymmetric or nonaxisymmetric, are obtained for the investigated cases.Numerical results are presented for the bifurcation stress of Aluminum 24S-T3 plates and foam like foundation materials. The results show that the effect of foundation is less significant in the plastic range than in the elastic range. As expected, the buckling stresses for the incremental theory are always higher than the results for the deformation theory. For fixed plates the maximum difference is around 10% at the high end of the validity of the stress-strain curve. But, surprisingly for the simply supported plates, the results from the incremental theory are higher by less than 1%. This means, that for circular simply supported plates, the well-known plastic buckling paradox almost disappears, even in the presence of a foundation.Cette thèse traite du voilement plastique par bifurcation d'une plate circulaire qui est partiellement ou complètement liée à une fondation élastique, et qui est soumise à une pression radiale uniforme sur sa périphérie. Avant le voilement, la plaque se trouve dans un état de contraintes équibiaxiales constantes. Sous ces contraintes, le matériau de la plaque subit un écrouissage suivant une surface de plastification en expansion isotrope J2 (von Mises). Les lois constitutives incrémentales, requises pour l'analyse de bifurcation, sont écrites de façon à incorporer le comportement selon la théorie de déformation J2, les théories incrémentales de la plasticité J2 et la théorie élastique. L'équation régissant le comportement de la plaque et les conditions frontières, adaptés au voilement axisymétrique et non-axisymétrique, sont dérivés selon le principe du travail virtuel et le principe de bifurcation sous augmentation de charge de Shanley. L'analyse exacte de l'équation différentielle du 4e degré permet d'obtenir, en fonction du ratio rayon/épaisseur des plaques et du module de fondation, les contraintes de voilement pour les plaques encastrées et simplement supportées en leur périphérie.Quatre configurations de fondations sont considérées : (1) aucune fondation présente, (2) une fondation présente partout, (3) une fondation partielle présente uniquement à l'intérieur de la moitié du rayon de la plaque et (4) une fondation partielle présente à partir de la moitié du rayon jusqu'au bord de la plaque. Ces configurations sont appliquées pour des plaques simplement supportées et encastrées en périphérie. Les contraintes de voilement ainsi que les modes de déformations associés, qu'ils soient axisymétrique ou non-axisymétrique, sont obtenus pour chaque cas.L'analyse numérique présente des résultats de contraintes de bifurcation pour des plaques d'aluminium 24S-T3 et des matériaux de fondation peu rigides de type mousse synthétique. Il en ressort que l'effet de la fondation sur les contraintes de voilement est moins important dans le domaine plastique que dans le domaine élastique. Tel que prévu, les contraintes de voilement découlant de la théorie incrémentale de la plasticité J2 sont toujours supérieurs que celles basées sur la théorie de déformation J2. Pour les plaques encastrées, à l'extrémité de la courbe contrainte-déformation, la différence maximale est d'environ 10%. Étonnamment par contre, pour les plaques simplement supportées, les résultats de la théorie incrémentale de la plasticité sont plus importants par moins de 1%. Ceci veut dire que, pour les plaques simplement supportées, le paradoxe du voilement plastique ne s'applique pas et ce, même en présence d'une fondation.
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Kim, Sungmin Mech E. Massachusetts Institute of Technology. "A study on cork-based plastic composite material." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68899.
Full textAbstract:
Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 115-116).
Sandwich panels are mainly used in construction for lightweight structures since their concept is appropriate due to extremely high in-plane and flexural stiffness to weight ratios. However, low structural freedom and high environmental burdens of core material in sandwich panels such as fiberglass, and chemically synthesized foams have retarded a wide use in various areas. Recently it has been suggested that the better performance and economic, environmental benefits could be possibly achieved by using hybrid sandwich panels comprising non-traditional pairs of materials for sandwich panels. Therefore, in this paper, a cork-based plastic composite material has been proposed as a new core material and the possibility for substituting existing core materials have been explored by investigation on its mechanical properties, economic benefit, and environmental impact. Several mechanical testing were carried out on the cork composite and Glass Fiber Reinforced Plastic (GFRP) to determine the mechanical properties and compare their relative performances. By conducting property-limited design cases with the obtained mechanical properties, how they will perform in light, stiff panel application was investigated. Economic analysis was demonstrated with a table top application by using rigidity equality condition. Finally, Eco-impact of the cork composite was investigated by conducting Life Cycle Assessment. The result proved that the cork composite is competitive with other core materials.
by Sungmin Kim.
Mech.E.
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Wan, Deborah Jo-May 1974. "On elastic-plastic large deformation analysis of beams." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10076.
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Ozkan, Istemi Faruk. "Plastic interaction relations for hollow structural steel sections." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6088.
Full textAbstract:
The first part of this study reports an experimental program consisting of six full-scale tests on pipe sections under load combinations of shearing forces, bending moments, and twisting moments. The experimental results agree very well with the predicted failure loads based on recently developed interaction relations. The experimental program establishes the validity of the analytical techniques used to derive the interaction relations for pipe sections. The verified methodology is extended to derive interaction relations for square hollow structural sections under combinations of normal forces, twisting moments, biaxial bending moments, and biaxial shearing forces. Careful consideration is given to the applicability limits of the developed interaction relations. A stress resultant transformation scheme is devised in order to reduce the number of interaction relations from 20 cases to only three fundamental cases.
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Chen, Weigang 1970. "Plastic resistance of thin-walled prismatic tubes under large twisting rotations." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88343.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (leaves 50-51).
by Weigang Chen.
S.M.
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Hsü, I.-Min. "Crack problems for elastic-plastic materials under antiplane shear loadings /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487598748017683.
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Chim, Jin Dercio José Pinto. "Laboratory investigation of soil reinforcement using shredded waste plastic bottles." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29296.
Full textAbstract:
Plastic bottles were first used commercially in 1947 but remained relatively expensive until the early 1960s when high-density polyethylene was introduced, with its attractive characteristics such as being strong, lightweight, durable, cheap, and resistance to breakage. Decomposition of plastic bottles or other plastic products can last from 400 to 1000 years; before this process happens, the plastic waste becomes a problem to the environment continuing to clog our waterways, forest, oceans and others natural habitats. As the capacity of landfills decrease and urbanization leads to rapid growth rates in the human population, either in Africa or any part of the world, this concern brought forward the need for this study. The research aimed to present an end-use solution for plastic bottles by investigating the feasibility of utilizing the plastic bottles as reinforcing elements in problematic soils encountered in the construction industry. In South Africa, plastic bottle waste has continued to increase despite efforts by government in the form of new waste legislation and taxes on plastic bottles. Hence, there is a need to find alternative uses for plastic bottle waste. The use of plastic bottle waste shreds as a soil reinforcement material in geotechnical engineering applications can help mitigate the disposal problems associated with plastics. In this study, a series of direct shear tests were conducted to examine the effect of plastic waste shredded pieces on the engineering properties of Cape Flats and Klipheuwel Sand. The shredded plastic bottles that were used for this study were sourced from Kaytech (supplier and manufacturer of Geosynthetics) in South Africa. The research was done to utilize this plastic through the inclusion of shredded plastic bottles as a form of soil reinforcement. The effects of introducing polyethylene shreds cut from used plastic bottles on the settlement parameters were investigated. It was found that presence of plastic shreds improved the shear strength parameters of the sand soil and they tend to improve further with increasing in plastic shred dosage. The cohesion reached its maximum value for both sands at a shred dosage of 30% by dry mass of the soil.
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Sommar, Pehr. "Differentiation of Human Dermal Fibroblasts and Applications in Tissue Engineering." Doctoral thesis, Linköpings universitet, Hand och plastikkirurgi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-60879.
Full textAbstract:
Tissue engineering applies principles of biology and engineering to the development of functional substitutes for damaged or lost tissues. Tools for the neo-generation of tissue in tissue engineering research include cells, biomaterials and soluble factors. One main obstacle in tissue engineering is the limited availability of autologous tissue specific progenitor cells. This has led to interest into using autologous cells with stem cell plasticity. Bone marrow derived stem cells were the first adult stem cells shown to have multilineage potential. Since, several reports have been published indicating that cells from other tissues; fat, muscle, connective tissue e.g., possess potential to differentiate into lineages distinct from their tissue of origin. The optimal cell type for use in tissue engineering applications should be easy to obtain, cultivate and store. The human dermal fibroblast is an easily accessible cell source, which after routine cell expansion gives a substantial cell yield from a small skin biopsy. Hence, the dermal fibroblast could be a suitable cell source for tissue engineering applications.The main aim of this thesis was to investigate the differentiation capacity of human dermal fibroblasts, and their possible applications in bone and cartilage tissue engineering applications. Human dermal fibroblasts were shown to differentiate towards adipogenic, chondrogenic, and osteogenic phenotypes upon subjection to specific induction media. Differentiation was seen both in unrefined primary cultures and in clonal populations (paper I). Fibroblasts could be used to create three-dimensional cartilage- and bone like tissue when grown in vitro on gelatin microcarriers in combination with platelet rich plasma (paper II). 4 weeks after in vivo implantation of osteogenic induced fibroblasts into a fracture model in athymic rats, dense cell clusters and viable human cells were found in the gaps, but no visible healing of defects as determined by CT-scanning (paper III). After the induction towards adipogenic, chondrogenic, endotheliogenic and osteogenic lineages, gene expression analysis by microarray and quantitative real-time-PCR found several master regulatory genes important for lineage commitment, as well as phenotypically relevant genes regulated as compared to reference cultures (paper IV). In conclusion, results obtained in this thesis suggest an inherent ability for controllable phenotype alteration of human dermal fibroblasts in vitro. We conclude that dermal fibroblasts could be induced towards adipogenic, chondrogenic, endotheliogenic or osteogenic novel phenotypes which suggest a genetic readiness of differentiated fibroblasts for lineage-specific biological functionality, indicating that human dermal fibroblasts might be a suitable cell source in tissue engineering applications.
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Suh, Myung Sung. "Plastic analysis of dented tubes subjected to combined loading." Thesis, Massachusetts Institute of Technology, 1987. https://hdl.handle.net/1721.1/121910.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1988.Title as it appeared in M.I.T. Graduate List, June 1987: Plastic analysis of dented tubes under combined loading.
Bibliography: leaves 194-198.
by Myung Sung Suh.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1988.
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Capaldi, Franco Mario 1977. "Atomistic simulations of elastic-plastic deformation of amorphous polymers." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8921.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 121-125).
As the demand for polymers with superior properties increases, an understanding of the fundamental connections between the mechanical behavior and underlying chemical structure becomes imperative. In this work, the thermo-mechanical behavior and the molecular-level origins of plastic deformation of an amorphous glassy polymer were studied using atomistic simulations. Understanding of the molecular response will aid the development of physics-based continuum level models for these materials. A polyethylene-like molecular network was numerically constructed using a Monte Carlo algorithm and then subjected to uniaxial deformation over a wide range of strain rates and temperatures using Molecular Dynamics. The model exhibits many experimentally observed characteristics such as an initial elastic response followed by yield then volume preserving plastic deformation. The stress response was decomposed into intra and inter molecular components and analyzed throughout deformation. In the glassy regime, activation parameters were calculated in the context of the Eyring Model of flow in a solid. In addition, observations were made of the evolution of chain configuration and the correlation of transitions between dihedral angle states. Below the glass transition, dynamic heterogeneity is observed. It was also observed that mobility, as measured by the transitioning between dihedral angle states, increases during plastic deformation to levels observed at much higher temperatures under zero stress. At temperatures near the glass transition temperature, the mobility approaches levels of undeformed samples at the glass transition temperature.
by Franco Mario Capaldi.
S.M.
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Kim, Do-Nyun. "Contributions to the anisotropic elasto-plastic analysis of shells." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/49760.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 133-142).
Shells are probably the most widely used structural component in engineering and also in nature due to their high efficiency and excellent performance when properly designed. On the other hand, they can be very sensitive to changes in geometries, thicknesses, applied loads and boundary conditions. Hence much research effort has been devoted to the reliable and efficient analysis of shells. This work contributes to the anisotropic elasto-plastic analysis of shells by addressing key issues in developing shell elements for finite element analysis and an elasto-plasticity model considering anisotropy and its evolution. First we develop a shell element that models the three-dimensional (3D) effects of surface tractions. The element is the widely used MITC4 shell element enriched by the use of a fully 3D stress-strain description, appropriate through-the-thickness displacements to model surface tractions, and pressure degrees of freedom for incompressible analyses. The element formulation avoids instabilities and ill-conditioning. We also develop a triangular 6-node shell element that represents an important improvement over a recently published element. The element is spatially isotropic, passes the membrane and bending patch tests, contains no spurious zero energy mode, and is formulated without an artificial constant. In particular, the improved element does not show the instability sometimes observed with the earlier published element.
(cont.) Finally we review a constitutive model for anisotropic elasto-plastic analysis which takes into account the anisotropy of both the elastic and plastic material behaviors, as well as their evolution with plastic strains. It is based on continuum energy considerations, the Lee decomposition of deformations and a stored energy function of the logarithmic strains. The present work focuses on giving some physical insight into the parameters of the model and their effects on the predictions in proportional and in non-proportional loading conditions.
by Do-Nyun Kim.
Ph.D.
34
Li, Liping. "Atomistic simulation of plastic deformation mechanisms in crystalline polyethelene." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37807.
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Bass, Michael Kevin 1975. "Fully-plastic open-bend and back-bend fracture specimens." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88831.
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Ressa, Aaron. "Plastic Deformation and Ductile Fracture Behavior of Inconel 718." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449001835.
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Bartleet, Trevor Clive. "Real-time automatic machine inspection of plastic bottle closures." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/9643.
Full textAbstract:
Bibliography: leaves 89-91.This thesis presents work done developing an automatic system for plastic bottle closures. These plastic closures ae manufactured at 20 per second and the inspection must be done in real-time at this rate. Two types of defects must be detected and the defective closures removed from the production line. Inspection by human operators proved to be unreliable and subjective, and an automatic inspection system was needed. A machine vision system is capable of producing reliable and repeatable results in an environment which is unpleasant to humans. An automatic inspection system was implemented on the production line. The development of this system is divided into three sections.
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Moening, Andrew. "Post-Consumer Plastic Particle Sortation by Plastic Type with the Use of Magnetic Fields and Ferrofluids for the Recycling Industry: A Proof of Concept Study." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1384548911.
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Schubak, Robert Brian. "Nonlinear rigid-plastic analysis of stiffened plates under blast loads." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/31482.
Full textAbstract:
The large ductile deformation response of stiffened plates subjected to blast loads is investigated and simplified methods of analysis of such response are developed. Simplification
is derived from modelling stiffened plates as singly symmetric beams or as grillages thereof. These beams are further assumed to behave in a rigid, perfectly plastic manner and to have piecewise linear bending moment-axial force capacity interaction relations, otherwise known as yield curves.
A blast loaded, one-way stiffened plate is modelled as a singly symmetric beam comprised
of one stiffener and its tributary plating, and subjected to a uniformly distributed line load. For a stiffened plate having edges fully restrained against rotations and translations,
both transverse and in-plane, use of the piecewise linear yield curve divides the response of the beam model into two distinct phases: an initial small displacement phase wherein the beam responds as a plastic hinge mechanism, and a final large displacement phase wherein the beam responds as a plastic string. If the line load is restricted to be a blast-type pulse, such response is governed by linear differential equations and so may be solved in closed form. Examples of a one-way stiffened plate subjected to various blast-type pulses demonstrate good agreement between the present rigid-plastic formulation and elastic-plastic beam finite element and finite strip solutions.
The response of a one-way stiffened plate is alternatively analysed by approximating it as a sequence of instantaneous mode responses. An instantaneous mode is analogous to a normal mode of linear vibration, but because of system nonlinearity exists for only the instant and deformed configuration considered. The instantaneous mode shapes are
determined by an extremum principle which maximizes the rate of change of the stiffened plate's kinetic energy. This approximate rigid-plastic response is not solved in closed form but rather by a semi-analytical time-stepping algorithm. Instantaneous mode solutions compare very well with the closed-form results.
The instantaneous mode analysis is extended to the case of two-way stiffened plates, which are modelled by grillages of singly symmetric beams. For two examples of blast loaded two-way stiffened plates, instantaneous mode solutions are compared to results from super finite element analyses. In one of these examples the comparison between analyses is extremely good; in the other, although the magnitudes of displacement response
differ between the analyses, the predicted durations and mechanisms of response are in agreement.
Incomplete fixity of a stiffened plate's edges is accounted for in the beam and grillage models by way of rigid-plastic links connecting the beams to their rigid supports. Like the beams, these links are assumed to have piecewise linear yield curves, but with reduced bending moment and axial force capacities. The instantaneous mode solution is modified accordingly, and its results again compare well with those of beam finite element analyses.
Modifications to the closed-form and instantaneous mode solutions to account for strain rate sensitivity of the panel material are presented. In the closed-form solution, such modification takes the form of an effective dynamic yield stress to be used throughout the rigid-plastic analysis. In the time-stepping instantaneous mode solution, a dynamic yield stress is calculated at each time step and used within that time step only. With these modifications in place, the responses of rate-sensitive one-way stiffened plates predicted by the present analyses once again compare well with finite element and finite strip solutions.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Vaziri, Reza. "Finite deflection dynamic analysis of rigid-plastic beams." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25142.
Full textAbstract:
An analytical procedure, which retains the influence of finite deflections,
is developed herein for the dynamic behaviour of rectangular shaped rigid-plastic beams. In the general formulation of the problem deformation is assumed to proceed under two distinct mechanisms depending on the extent to which the value of the peak pressure exceeds the static collapse pressure of the beam. These mechanisms are described by kinernatically admissible velocity fields that satisfy the appropriate continuity conditions. The governing equations of motion are derived from a variational
statement consisting of the principle of virtual work and D'Alembert's principle. The conventional parabolic yield surface (which describes the coupling action between axial forces and bending moments at yield) and its associated flow rule are adopted to describe the plastic behaviour of the beam material. The kinematic small but finite deflection analysis, in which the membrane forces and bending moments interact, generally leads to basic equations which are of nonlinear character. These resulting equations
are solved analytically and closed form expressions are developed for the prediction of maximum permanent deformation of the beam. A dynamic membrane analysis is carried out in those cases when the input energy is sufficiently high that the beam undergoes moderately large deformation (i.e. deflections of the order of beam thickness). Finally the dependence of the permanent deflection on the applied pressure and impulse is obtained for a family of rectangular pulses. This relationship is represented by an isoresponse curve in a form convenient for direct engineering use.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Alhajeri, Saleh N. "Processing of aluminium and titanium alloys by severe plastic deformation." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/185107/.
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Li, Likai. "Design, Fabrication and Metrology of Precision Molded Freeform Plastic Optics." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1412162892.
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CHAKRABARTI, SEKHAR KUMAR. "INELASTIC BUCKLING OF GUSSET PLATES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184188.
Full textAbstract:
The strength and behavior of gusset plates in buckling is evaluated herein based on data from the experimental investigations conducted by other researchers and the analytical work presented herein. A set of design guidelines has been recommended through the review of the current practice. Representative single and double brace gusset plates normally adopted for connections with compressive bracing/diagonal members in braced frames and trusses, were modeled and analyzed using linear and nonlinear finite element methods to determine the buckling loads. The buckling analysis data along with the test data indicated the occurrence of inelastic buckling of the gusset plates. Current design practice and a set of formulas for determination of gusset plate thickness have been reviewed. A set of guidelines has been recommended for the design and evaluating gusset plate buckling loads.
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Hoffman, Rebecca M. "Nonlinear elastic-plastic analysis using the modified finite quasi-prism element /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488193665235655.
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Geng, Lumin. "Application of plastic anisotropy and non-isotropic hardening to springback prediction /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488195154360632.
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Bartlett, Leah Paige. "A Preliminary Study of Using Plastic Molds in Injection Molding." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1509440406290043.
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Alqahtani, Fahad Khshim. "Production of novel manufactured plastic aggregate and its utilisation in concrete." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7821/.
Full textAbstract:
Plastic waste and its low recycling rate make a significant contribution towards the pollution of the environment. Therefore , it is essential that plastic waste is utilised in different applications . One of the applications is its use either as an aggregate or to form aggregate for use in the concrete. New aggregates were developed using plastic waste and by-product or low cost granular materials. These aggregates have a relatively low density and water absorption as compared to conventional aggregates , and were successfully used to produce sustainable or green lightweight concrete. The new aggregates were used to replace the conventional coarse fraction of either nonnal weight or lightweight aggregates at full or partial replacements; where both properties of fresh and hardened concrete were investigated. It was found that the effect of the replacement level of the conventional aggregate with the manufactured recycled plastic aggregates was less prominent on density as compared to the other properties. The hardened concrete showed a reduction in mechanical properties , with an increase in the proportions of manufactured recycled plastic aggregates in the mix . The assessment of durability properties, thermal conductivity and curing temperature was also carried out. The concrete ductility, drying shrinkage, creep strain and thennal conductivity increased as the content of manufactured recycled plastic aggregate increased in the mix. Whilst, the chloride penneability was found to decrease with an increase in the percentage of recycled plastic aggregate. Finally, models were proposed to predict the mechanical and durability properties utilising the results of this study.
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Daniel, Dominique. "Prediction of elastic and plastic anisotropy in deep drawing steels." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74533.
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Yield stresses and r-values were measured as a function of inclination with respect to the rolling direction on thirty-one steels selected from high strength low alloy (HSLA), Al-killed (AKDQ), interstitial free (IF1 and IF2) and rimmed (RIM) types. Modul-r and electromagnetic acoustic (EMAT) techniques were employed to determine the elastic anisotropy in terms of the angular variation of Young's modulus and the ultrasonic velocities, respectively. Orientation distribution functions (ODF's) were also measured for these steels in their as-received states and after deformation in tension and in drawing. The various initial textures and their evolutions along the latter strain path are analyzed in terms of the 4- and 6-ear behaviours commonly observed during the forming of cylindrical cups.The series expansion method was employed for predicting the elastic and plastic anisotropies from the initial texture data. Comparison with the experimental measurements of Young's modulus indicates that the so-called elastic energy method can accurately reproduce the elastic anisotropy if the single crystal elastic constants are appropriately chosen within their ranges of uncertainty. The systematic evaluation of various grain interaction models for predicting the polycrystal plastic anisotropy reveals that the "pancake" relaxed constraint model is a more accurate predictor of the behaviour than the Taylor, Sachs-Kochendorfer, or other relaxed constraint models. The best quantitative agreement is obtained when the critical resolved shear stress (CRSS) ratio for glide on the $ {112 } langle 111 rangle$ and $ {110 } langle 111 rangle$ systems is 0.95 (except for the AKDQ and IF2 grades, for which values of 0.90 and 1.0, respectively, are preferred).
The ODF coefficients of order greater than 4 were evaluated and calculated non-destructively from the anisotropy of the ultrasonic velocities of the lowest order symmetrical Lamb (S$ sb{ rm o}$) and shear horizontal (SH$ sb{ rm o}$) waves propagating in the rolling plane. The elastic energy method was employed, together with a decomposition of the texture into the principal preferred orientations. The calculated pole figures based on the ODF coefficients obtained in this way are similar to those derived from complete X-ray data. It is shown that the plastic properties of commercial deep drawing steels are predicted more accurately when the 4th and 6th order ODF coefficients are employed than when only the 4th order ones are used.
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Pan, Yong. "Analytical Development of A Plastic Hinge Detail for Steel SMFs." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194268.
Full textAbstract:
A modular plastic hinge seismic special detail has been developed for use in steel special moment frames (SMFs). The aim of the special detail design is to dissipate seismic energy through stable yielding of a beam "link" in plastic hinge region. Reliable and repeatable energy dissipation at high ductility is assured through the elimination of weld failure modes, and the mitigation of local buckling and high multi-axis restraint. A casting process is used to configure the modular detail directly to meet these performance objectives. The primary features of the link region are an isolated flange with an integrally cast stiffener and a reduced section isolated web. Two forms of the detail exist: a plastic hinge modular node (PH-MN) and a bolted alternative, the bolted plastic hinge connector (BPHC). The PH-MN, a "node" occupying the entire beam-to-column joint, was used to develop the concept. The PH-MN configuration removes the field weld from the critical cross-section, reduces triaxiality and eliminates through-thickness failure modes at the beam/column interface. The BPHC preserves the primary features of the PH-MN and provides performance at nearly the same efficiency, but, as a replaceable field-bolted component, is significantly more economical, improves modularity, and has certain practical advantages. A design procedure was developed to create a family of modular designs.
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LaHousse, Sean W. (Sean William). "Vacuum insulation using perlite powder sealed in plastic and glass." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/72769.
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