Dissertations / Theses on the topic 'Effect of Cemented Fill'
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Jayasinghe, Mudiyanselage Harshani Dilanka Jayasinghe. "Scaled - Down Open Stoping Under Cemented Paste Fill." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/79930.
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The principle scope of this research was to develop relationship between stope dimensions and cemented paste fill strength. Experiments in various fill thickness to span width ratios with cemented paste fill with different mechanical properties were conducted by using a constructed scaled-down open stope. Scaled-down laboratory experiments were used to understand the mechanism of fill failure when exposure is undertaken under a relatively fresh fill mass.
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Hughes, Paul B. "Design guidelines : underhand cut and fill cemented paste backfill sill beams." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/47089.
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Difficult ground conditions negatively affect both mine production and the safety of underground workers. Underhand cut-and-fill mining is a potential solution to these issues. Discussions with mine sites revealed the use of sill beams in underhand cut-and-fill mining is not optimized. Optimization in ground support, development of in-situ strength test, and revisions of design standards are desired. Ultimately, the operations require the minimum cemented paste backfill (CPB) strength for a stable span.
Operational concerns were addressed by a multi-prong approach investigating stability of CPB sill beams using observational, experimental and analytical techniques. A case study approach summarizing the design of five mines utilizing underhand cut-and-fill with CPB is presented for different ground conditions. A historical study of span widths and beam strengths for the Stillwater mine is presented.
Laboratory testing determined the stress-strain behaviour of CPB. CPB follows a hyperbolic elastic loading path to peak stress followed by a strain-softening associated with the decay of the cohesion values. Additional testing found that cohesive and tensile strength values were on average 35 and 20 percent respectively of the unconfined compressive strength. This finding impacts sill beam design strengths as previous assumptions were conservative. Test database analyses from three mine sites found that sample size and location preparation has no effect on the strength of the sample. In-situ testing methods common in other industries were not practical with CPB; rather the in-situ strength can be represented by a site specific moisture content index relationship.
Review of current design methodology noted closure stresses were absent from the majority; a method was developed to assess closure for sill beam stability. The potential for critical failures were determined through a Monte Carlo probabilistic model. Methods reducing the risk of failure based on the simulation are investigated. Analysis found ground support does not improve the structural stability of the sill beam. Ground support keeps the beam intact: beam equations govern stability. The stability of sill beam in a seismic environment was analyzed based on the strain-energy density of the beam. The research concludes with a design guideline for CPB sill beams.
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Rask, Amanda. "Indirect methods as quality control of cemented hydraulic fill : Renström mine, Boliden mineral AB." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72962.
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The Renström mine, Boliden Mineral AB, uses, among other methods, the Transverse long hole stoping method with backfill. The mine uses a cement-stabilized hydraulic fill (CHF), which is a mixture of enrichment sand, cement and water. The most important factor in relation to strength is the water cement ratio. Today, only tests have been performed on the surface and in laboratory tests. The purpose of this work is thus to study the possibility of using other types of methods that can give a better understanding of the strength of the entire filling volume. Studies on backfill containing Portland cement and sulphur have shown that the UCS strength decreases with time, which can cause problems for the mine. A leaching method (MRM leaching test) used to evaluate potential sulphide soils has been used in this study on the backfill to investigate the sulphurs impact on the cement mixture. Electrical conductivity, pH, and redox potential were investigated and gave similar results, where the higher cement levels (8%, 10%, and 12%) were indistinguishable while the lower cement content (4%) differed significantly from the other levels. This probably indicates that the higher cement levels have a greater resistance to the influence of the sulphur. The most promising results were given when the method was used on enrichment sand alone. The linear lowering of the pH value of the enrichment sand, from pH 4.9 to about pH 3, point to that the enrichment sand contains large amounts of sulphur, as previously chemical analysis has shown. This suggests that the method can best be used in an early stage before the sand is mixed with cement. The strength results on the samples showed a strength after 7 days that was in line with the 90-day strength. However, all 90 day samples had decreased in strength during the time sequence, which may be an effect of the sulphur content, but should be further investigated to be determined. The smaller size of the samples was also experienced as a challenge during the temperature measurements due to small temperature variations and environmental effects. A maturity method for predicting the strength of concrete called "The maturity method" has been investigated in this study. To determine the strength maturity relationship, both the temperature related to time and the equivalent age must be evaluated. The study showed that the method cannot be used on the mine's backfill without first making adjustments related to the lower cement content used in the backfill compared with concrete constructions, since it is not possible to determine the strength growth in the early stage as the method requires.
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Berglund, Lina. "The Effect of Cooling Rate on Sintered Cemented Carbides." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-288541.
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Magnetic measurements are useful tools for quality control of cemented carbides. Previous work at Sandvik Mining and Rock Technology has shown that the coercivity increases with increased cooling rate during sintering for a specific grade. This study aims to investigate why the coercivity changes with the cooling rate and if this is true for other cemented carbide grades as well. Three different cemented carbide grades were sintered with different cooling rates and evaluated with coercivity, Cobalt-magnetic saturation and hardness measurements, and with microscopy and Electron Backscatter Diffraction analysis. It was found that the coercivity increased with increasing cooling rates for the previously studied grade, but not for the two other grades. It was expected that the increased coercivity would indicate a decrease in WC grain size, but the results showed that the WC grain size of the fastest and slowest cooling rate were the same. However, a change in size of the Co areas between the WC grains was found. The fast cooled sample showed smaller Co areas than the slow cooled sample. These Co/WC grain boundaries increase the coercivity. An increased fraction of hcp-Co/fcc-Co was also found for the fast cooled material which also increases the coercivity. No relationship between the hardness and the coercivity or the cooling rate was found. The contiguity for the different grades was also calculated. No significant difference in contiguity between the different cooling rates of each material was found but the contiguity values between the different materials differed. This is probably mainly dependent on the different binder contents of the materials.Magnetiska egenskaper är en viktig del av kvalitetskontrollen av hårdmetaller. Tidigare forskning hos Sandvik Mining and Rock Technology har visat att koerciviteten hos en hårdmetallsort ökar med ökad kylhastighet vid sintring. Målet med den här studien är att undersöka varför koerciviteten ökar med kylhastigheten och om detta även gäller andra hårdmetallsorter. Tre olika hårdmetallsorter sintrades med olika kylhastigheter undersöktes med mätningar av koercivitet, magnetisk mättnat i koboltfasen och hårdhet, samt med mikroskopi och Electron Backscatter Diffraction analys. Det visade sig att koerciviteten ökade med ökad kylhastighet för hårdmetallsorten som studerats tidigare, men inte för de andra två sorterna. En ökad koercivitet förväntas visa på en minskad WC-kornstorlek, men resultaten visar att det långsamt kylda och snabbkylda provet hade samma WC-kornstorlek. Däremot upptäcktes en ändring av storleken på Co-områdena mellan WC-kornen. Det snabbkylda provet visade en mindre storlek av Co-områdena jämfört med det långsamt kylda provet. Fler Co/WC-korngränser i det snabbkylda provet leder till en ökad koercivitet. Fraktionen av hcp-Co/fcc-Co-korngränser ökade också för det snabbkylda provet vilket också ökar koerciviteten. Inget samband mellan hårdheten och koerciviteten eller kylhastigheten upptäcktes. Beräkning av kontiguiteten för de olika sorterna genomfördes också. Ingen signifikant skillnad i koercivitet mellan de olika kylhastigheterna för the olika sorterna hittades, men kontiguiteten mellan de olika sorterna varierade. Det beror mest troligt på att dom olika sorterna har olika mängd matrismaterial.
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Bertrand, Timothy Paul. "Effect of water maldistribution on cooling tower fill performance evaluation." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6841.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011.ENGLISH ABSTRACT: A 1.5 x 1.5 m2 counter-flow fill performance test facility is described in detail. Instrumentation was selected and installed in the cooling tower fill test facility and calibrated to ensure measurement accuracy. A facility control program was written to simplify the operation of the test facility via a user interface. The program calculates automatically the Merkel number and loss coefficients as measures of fill thermal and flow performance respectively. A spray frame was designed and manufactured to ensure uniform water distribution to the fill. The water distribution through different fills with varying fill heights and different water flow rates was measured. The water attached to the walls of the test facility was examined. Film, trickle and splash fills are tested in the upgraded test facility. The film and trickle fill performance determined during testing is deemed acceptable as these fills have minimal migration effects. Fills with poor distribution effects and large migration of water towards the walls of the test facility, like the splash fill tested, cannot to be tested accurately in a 1.5 x 1.5 m2 test section as the results do not represent the performance of the fill in a relatively large cooling tower. Other aspects examined were: • air flow uniformity • air fill bypass effects • location of water inlet and outlet temperature measurement points • location of pressure measurement probes. It was determined that, in the current test facility: • air uniformity is suitable for performance testing • air bypass effects can be ignored for open fills and can be minimised for dense fills by packing sponge between the fill and walls • water inlet and outlet temperatures should be measured in the pipe-work, resulting in a measurement method that is not influenced by the relative weightings of each thermocouple • pressure difference over the fill height measured by the pressure measurement tap is independent of its location on the fill outlet plane provided the pressure measurement points are perpendicular to the air stream and are not against the walls.
AFRIKAANSE OPSOMMING: 'n 1.5 x 1.5 m² Teenvloei pakking werkverrigting toetsfasiliteit word in detail beskryf. Instrumentasie is gekies en geïnstalleer in die koeltoring pakking toetsfasiliteit en gekalibreer om akkuraatheid te verseker. 'n Fasiliteit beheer program is geskryf om die gebruik van die toetsfasiliteit te vereenvoudig. Die program het ‘n vriendelike gebruikers intervalk. Die program bereken outomaties die Merkel-getal en verlies koëffisiënte as mate van pakking termiese- en vloeiwerksverrigting. 'n Sproeiraam is ontwerp en vervaardig om uniforme water verspreiding aan die pakking te verseker. Die water verspreiding deur verskillende pakkings met verskillende pakking hoogtes en water vloei snelhede is gemeet. Die water aangeheg aan die mure van die toetsfasiliteit is ook ondersoek. Film, druppel en spat pakkings word in die opgegradeerde toetsfasiliteit getoets. Die film- en druppelpakking werksverrigting bepaal tydens die toetse is aanvaarbaar, aangesien hierdie pakkings minimale migrasie effekte het. Pakking met swak verspreiding effekte en 'n groot migrasie van water na die wande van die toetsfasiliteit, soos gevind met die spatpakking toetse, kan nie met akkuraatheid in 'n 1.5 x 1.5 m² toets seksie getoets word nie omdat die resultate nie die werkverrigting van die pakking verteenwoordig in 'n relatief groot koeltoring. Ander aspekte wat ondersoek was: • lugvloei uniformiteit • lug omleiding effeckte • die posisie van water in- en uitlaat temperatuur meetpunte • posisie van die drukmeetapparaat. Dit is vasgestel dat, in die huidige toetsfasiliteit • lugvloei eenvormigheid geskik is vir prestasietoetsing • lug omleiding effekte kan geïgnoreer word vir oop pakkings en kan verklein word vir digte pakkings deur spons tussen die pakking en mure te pak • water inlaat- en uitlaattemperature behoort gemeet te word in die pypwerk en lei tot 'n metings metode wat nie beïnvloed word deur die relatiewe gewigte van elke thermokoppel nie • die druk verskil gemeet deur die drupmeetpunte oor die pakkinghoogte is onafhanklik van hul posisie op die pakkinguitlaatvlak op voorwaarde dat die drukmeetpunte loodreg is teen die lugstroom en nie teen die mure nie.
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Jacobs, Jessica. "Effect of post-treatment of cemented carbide : Microstructural investigation and evaluation of mechanical properties of cemented carbide inserts for rock tool applications." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-84628.
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Cemented carbides are used in rock tool applications by reason of their beneficial mechanical properties, i.e. a combination of high toughness, wear resistance and hardness. The cemented carbides commonly receive their hardness from tungsten carbides (WC) whereas cobalt (Co) is the dominating binder material. To obtain a beneficial balance of these desired properties, the binder phase can be strengthened by post-sintering treatment to minimize the risk of catastrophic failure. Previous work has shown that the face centered cubic (FCC) cobalt phase is stabilized by a higher degree of dissolved tungsten in the binder. The residual stresses have been related to both further stabilization of the FCC and local transformation to a hexagonal close packed (HCP) phase. By exposing the inserts to mechanical deformation, i.e. inducing stress, the Co-binder material could theoretically transform from FCC to HCP. In this master thesis, five cemented carbides with three different binder phase compositions have been investigated. Additionally, the influence of the carbon content and addition of an alloying element was evaluated. This was done by electron backscatter diffraction (EBSD) analysis of the microstructure of each sample in as-sintered state and after post-treatment to gain better understanding on how the phase stability of the binder is affected by a post-sintering process. In addition, magnetic measurements, hardness-testing and mechanical tests were performed on the materials to evaluate the effect of using different binder compositions. It was found that a low carbon content provides smaller and more rounded WC grains and binder phase dominated by FCC-Co compared to an equivalent material with a high carbon content. A low carbon content furthermore resulted in a more wear resistant material. The addition of alloy MA presented a greater increase in surface hardness after post-treatment and made the materials even more wear resistant compared to the non-alloyed. The non-alloyed material performed better in a test measuring the fracture energy. A material with an Fe-based binder showed the least increase in surface hardness and the highest increase and overall fracture energy. All materials experienced a WC grain size refinement and an increase in their surface hardness after post-treatment. Only one material gave an indication on FCC to HCP phase transformation, no conclusions could be drawn from the other samples.Hårdmetaller används i bergborrstift på grund av materialets fördelaktiga mekaniska egenskaper vilket innefattar en kombination av hög seghet, hårdhet och bra nötningsmotstånd. Hårdheten uppnås vanligen av volfram karbider (WC) medan segheten ges av en bindefas som oftast är baserad på cobolt (Co). För att få ett material med en bra balans mellan seghet och hårdhet så kan bindefasen stärkas genom en ytbehandling efter sintringen för att minimera risken för att borrstiftet går sönder under användning. I tidigare studier har det framkommit att ytcentrerad kubiskt tätpackad (FCC) cobolt stabiliseras av volfram som lösts i bindefasen. Spänningar som uppkommer på grund av detta har relaterats till vidare stabilisering av FCC-fasen, men även lokal omvandling till hexagonalt tätpackad (HCP) cobolt. Genom att utsätta borrstiften för mekanisk deformation, i.e. inducera spänningar, kan bindematerialet teoretiskt sett omvandlas från FCC till HCP. I detta examensarbete har fem bergborrstift med tre olika bindefassammansättningar undersökts. Därutöver har även inverkan av kolhalten och tillägget av ett legeringsämne utvärderats. Den primära metoden för att genomföra undersöka mikrostrukturen hos de sintrade och efterbehandlade stiften var bakåtspridd elektrondiffraktion (EBSD). Syftet med undersökningen var att öka förståelsen kring bindefasens fasstabilitet då den utsatts för en efterbehandlingsprocess. Även magnetisk mätning, hårdhetstestning och mekanisk prövning utfördes på materialen för att kunna jämföra de olika bindefassammansättningarna mot varandra. Resultaten visade att en låg kolhalt gav ett material med mindre och mer rundade WC korn samt att bindefasen dominerades av FCC-Co jämfört mot ett material med samma bas och hög kolhalt. Därtill uppvisade materialen med låg kolhalt bättre nötningsmotstånd. Legeringen av bindefasmaterialet visade en ökning i ythårdhet efter efterbehandling och gjorde materialen mer nötningsbeständiga än de icke-legerade materialen. De icke-legerade materialen visade däremot på högre krosstyrka. Materialet med en järn-baserad bindefas påvisade minst ökning av ythårdheten och högst ökning samt högsta värde på krosstrykan. Samtliga material visade en förfining av WC kornen och en ökning av ythårdheten efter efterbehandlingen. Endast ett material indikerade omvandling från FCC till HCP, inga slutsatser kunde dras från de övriga proverna.
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Danielsson, Olivia. "Effect of carbon activity on microstructure evolution in WC-Ni cemented carbides." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226566.
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The aim of this work was to systematically study how the microstructure evolution is affected by the carbon activity in WC-Ni cemented carbides. Seven WC-9.59at%Ni alloys with different carbon activity were sintered at 1500 °C. From investigating these alloys, the carbon window has been experimentally evaluated using light optical microscopy and compared to theoretical carbon window calculated using Thermo-Calc. The overall microstructure of cross sections and raw surfaces have been investigated using scanning electron microscopy. Finally, the WC grain size and distribution have been evaluated using electron backscatter diffraction. It was found that the experimental carbon window was slightly wider than the theoretical carbon window. The WC grain size increased and the grain size distribution got wider with increasing carbon activity. In addition, the largest WC grains showed the largest grain growth by increasing carbon activity. By comparing the present results of grain size and distribution of WC-Ni to previous results of WC-Co, it was found that the WC grain growth was more pronounced and more influenced by the carbon activity.
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Polo, Montes Carlos A. "The effect of cementation technique on the retention of adhesively cemented prefabricated posts." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2007m/polomontes.pdf.
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Juirnarongrit, Teerawut. "Effect of diameter on the behavior of laterally loaded piles in weakly cemented sand /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3071009.
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Miner, Dustin David. "The Effect of Flowable Fill on the Lateral Resistance of Driven-Pile Foundations." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3308.pdf.
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Celestin, Henry Jean Claude. "Geotechnical properties of cemented paste backfill and tailings liners: Effect of mix components and temperature." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28080.
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Cemented Paste Backfill (CPB) is extensively used in underground mine operations. Several studies have been conducted to investigate the mechanical properties of CPB. However, little attention has been devoted to the thermal conductivity of CPB. The knowledge of this thermal property is vital for the design of cost-effective and durable CPB materials. This paper presents the results of a comprehensive laboratory study on the thermal conductivity of CPB. Influencing factors on the thermal conductivity of CPB were quantitatively investigated. The measurements of thermal conductivity were performed by using the KD2 Thermal Properties Analyzer. Valuable results with regards to the effects of CPB's mix components, curing time and temperature, water saturation degree on the thermal conductivity of CPB were gained. It is felt that the present study would contribute to the better optimization of CPB mixtures and the design of more cost-effective and durable CPB underground structures.
Keywords. Cemented Paste Backfill; Thermal Conductivity; Hydration; Temperature; Sulphate; Tailings.
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Mohsin, AKM. "AUTOMATED Gmax MEASUREMENT TO EXPLORE DEGRADATION OF ARTIFICIALLY CEMENTED CARBONATE SAND." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/5003.
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Soil Stiffness is an important parameter for any geotechnical engineering design. In laboratory tests it can be derived from stress-strain curves or from dynamic measurement based on wave propagation theory. The second method is a more accurate and direct method for measuring stiffness at very small strains. Until now dynamic measurements have usually been obtained manually from the triaxial test. Attempts have been made to automate the procedure but have apparently failed due to the high level of variability in dynamic measurements. Moreover, triaxial tests of soil can be very lengthy and manual dynamic measurements can be very tedious and impractical for long stress-path tests. In this research a computer program has been developed to automate the stiffness measurement (using bender elements) based on the cross- correlation technique. In this method the program records all the peaks and corresponding arrival times in the cross-correlation signal during the test. The stiffness is calculated and displayed on the screen continuously. The Bender Element enabled to get the small strain shear modulus. An arbitrary “Chirp” waveform of 4 kHz frequency was used for this purpose. Subsequently Bender Element test results were checked by ‘Sine’ waveforms of frequencies 5kHz to 20kHz, as well as by manual inspection of the arrival time. This thesis discusses the method and some of the difficulties in truly automating the process. Finally some results from a number of stress path tests on uncemented and cemented calcareous sediments are presented. Bender elements have been used by many researchers to determine the shear modulus at small strain. Most previous studies have used visual observation of arrival time, which is time consuming and often requires some judgement from the operator. This thesis will describe the use of cross-correlation as a method for automation of Gmax measurement. Cross-correlation has been claimed to be unreliable in the past. However, it will be shown that provided several peaks in the cross-correlation signal are monitored it is possible to follow the variation of Gmax throughout consolidation and shearing. The measurement can be made at regular intervals within the software controlling a stress-path apparatus. Details of the apparatus used and practical considerations including selection of waveform and frequency are discussed. A series of drained cyclic triaxial tests was carried out on artificially cemented and uncemented calcareous soil of dry unit weights 13, 15, and 17 kN/m3 and sheared with constant effective confining stress 300 kPa. Gypsum cement contents of 10%, 20% and 30% of the dry soil weight were used. In addition a series of stress path tests were performed on Toyuora sand samples. Results will be presented for two uncemented and one cemented sand. In addition to the bender elements, all tests had internal instrumentation to monitor axial and lateral strains. Results will be presented for Toyura sand to show that the measurements are consistent with those obtained by other methods. Results will also be presented for carbonate sand subjected to a wide range of stress paths. Finally, results will be presented for the carbonate sand cemented with gypsum. The degradation of Gmax of the cemented soil subjected to variety of monotonic and cyclic stress-paths is presented. Analysis of the results includes assessment of the factors influencing Gmax for uncemented sand. Preliminary analysis indicates that in order of importance these are the mean effective stress, the stress history, void ratio and stress ratio. For cemented sand, Gmax is initially constant and independent of stress path. After yielding the modulus degrades, becoming increasingly stress level dependent and eventually approaches the value for uncemented sand. Factors influencing the rate of degradation are discussed. For the Toyuora sand samples the effects of end restraint on the stress-strain response at small strains were investigated. The conventional method of mounting triaxial specimen has the effect of introducing friction between sample and end platen during a compression test. This inevitably restricts free lateral movement of the specimen ends. Frictional restraint at the sample ends causes the formation of 'dead zones' adjacent to the platens, resulting in non-uniform distribution of stress and strain (and of pore pressure if undrained). On the other hand the specimen with 'free' ends maintain an approximate cylindrical shape instead of barrelling when subjected to compression, resulting in a more uniform stress distribution.
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Mohsin, AKM. "AUTOMATED Gmax MEASUREMENT TO EXPLORE DEGRADATION OF ARTIFICIALLY CEMENTED CARBONATE SAND." University of Sydney, 2008. http://hdl.handle.net/2123/5003.
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Doctor of Philosophy(PhD)Soil Stiffness is an important parameter for any geotechnical engineering design. In laboratory tests it can be derived from stress-strain curves or from dynamic measurement based on wave propagation theory. The second method is a more accurate and direct method for measuring stiffness at very small strains. Until now dynamic measurements have usually been obtained manually from the triaxial test. Attempts have been made to automate the procedure but have apparently failed due to the high level of variability in dynamic measurements. Moreover, triaxial tests of soil can be very lengthy and manual dynamic measurements can be very tedious and impractical for long stress-path tests. In this research a computer program has been developed to automate the stiffness measurement (using bender elements) based on the cross- correlation technique. In this method the program records all the peaks and corresponding arrival times in the cross-correlation signal during the test. The stiffness is calculated and displayed on the screen continuously. The Bender Element enabled to get the small strain shear modulus. An arbitrary “Chirp” waveform of 4 kHz frequency was used for this purpose. Subsequently Bender Element test results were checked by ‘Sine’ waveforms of frequencies 5kHz to 20kHz, as well as by manual inspection of the arrival time. This thesis discusses the method and some of the difficulties in truly automating the process. Finally some results from a number of stress path tests on uncemented and cemented calcareous sediments are presented. Bender elements have been used by many researchers to determine the shear modulus at small strain. Most previous studies have used visual observation of arrival time, which is time consuming and often requires some judgement from the operator. This thesis will describe the use of cross-correlation as a method for automation of Gmax measurement. Cross-correlation has been claimed to be unreliable in the past. However, it will be shown that provided several peaks in the cross-correlation signal are monitored it is possible to follow the variation of Gmax throughout consolidation and shearing. The measurement can be made at regular intervals within the software controlling a stress-path apparatus. Details of the apparatus used and practical considerations including selection of waveform and frequency are discussed. A series of drained cyclic triaxial tests was carried out on artificially cemented and uncemented calcareous soil of dry unit weights 13, 15, and 17 kN/m3 and sheared with constant effective confining stress 300 kPa. Gypsum cement contents of 10%, 20% and 30% of the dry soil weight were used. In addition a series of stress path tests were performed on Toyuora sand samples. Results will be presented for two uncemented and one cemented sand. In addition to the bender elements, all tests had internal instrumentation to monitor axial and lateral strains. Results will be presented for Toyura sand to show that the measurements are consistent with those obtained by other methods. Results will also be presented for carbonate sand subjected to a wide range of stress paths. Finally, results will be presented for the carbonate sand cemented with gypsum. The degradation of Gmax of the cemented soil subjected to variety of monotonic and cyclic stress-paths is presented. Analysis of the results includes assessment of the factors influencing Gmax for uncemented sand. Preliminary analysis indicates that in order of importance these are the mean effective stress, the stress history, void ratio and stress ratio. For cemented sand, Gmax is initially constant and independent of stress path. After yielding the modulus degrades, becoming increasingly stress level dependent and eventually approaches the value for uncemented sand. Factors influencing the rate of degradation are discussed. For the Toyuora sand samples the effects of end restraint on the stress-strain response at small strains were investigated. The conventional method of mounting triaxial specimen has the effect of introducing friction between sample and end platen during a compression test. This inevitably restricts free lateral movement of the specimen ends. Frictional restraint at the sample ends causes the formation of 'dead zones' adjacent to the platens, resulting in non-uniform distribution of stress and strain (and of pore pressure if undrained). On the other hand the specimen with 'free' ends maintain an approximate cylindrical shape instead of barrelling when subjected to compression, resulting in a more uniform stress distribution.
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Longpradit, Panchan. "Effect of substrate pretreatment on CVD diamond coated cemented tungsten carbide tools for wood cutting application." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326525.
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Brumby, Scott Andrew. "The effect of surface roughness and a collar on fixation of cemented femoral stems in vivo /." Title page, table of contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phb8934.pdf.
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Barker, D. S. "A numerical analysis of the effect of surface finish and cement creep in cemented total hip replacement /." Title page, abstract and contents only, 1996. http://web4.library.adelaide.edu.au/theses/09ENS/09ensb255.pdf.
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Dhakal, Pashupati. "NUMERICAL INVESTIGATIONS OF THE EFFECT OF FILL FACTOR IN AN INTERNAL MIXER FOR TIRE MANUFACTURING PROCESS." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1466964421.
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Ahmed, Istiaque. "NON-ISOTHERMAL NUMERICAL INVESTIGATIONS OF THE EFFECT OF SPEED RATIO AND FILL FACTOR IN AN INTERNAL MIXER FOR TIRE MANUFACTURING PROCESS." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1524584349185209.
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Little, Lauren M. "INVESTIGATING THE EFFECT OF STRESS, WETTING, AND COMPACTION ON SETTLEMENT POTENTIAL OF MINE SPOILS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_theses/525.
Full textAbstract:
Strip mining in Kentucky has left large areas of land that could potentially be used for business and housing developments. However, the mine spoils underlying these areas are prone to severe differential settlement due to a variety of factors. Mine spoil from the Gateway Business Park in Jenkins, Kentucky was used for a series of laboratory tests to develop relationships between shear wave velocity, confining stress, compaction energy, and dry unit weight to develop a method to assess settlement potential. It was found that a stress-corrected shear wave velocity of greater than 275 ft/s/psi0.25 typically indicated dry mine spoil, and less than 275 ft/s/psi0.25 typically indicated wet mine spoil. Equations were developed to predict the amount of settlement of a mine spoil profile based on the load, the mine spoil lithology, and the shear wave velocity of the mine spoil. With regards to compaction, it was found that if the mine spoil was compacted to at least 120 pcf (18.8 kN/m3), or a void ratio of 0.45 or less, the mine spoil would suffer little to no volume change when wetted. The results provided herein form the basis of a methodology for screening mine spoil sites for development based on settlement potential.
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Park, Bongcheol. "Effect of cavity pre-fill and geometry on flow patterns and air entrapment in the die cavity in cold chamber die casting /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399451963137.
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Mahal, Raj-Deep Singh. "A standardized approach to determine the effect of thermocycling and long term storage on the shear bond strength of orthodontic brackets cemented to bovine enamel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0021/MQ53415.pdf.
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JAIN, NAVEEN KUMAR. "EFFECT OF CEMENTED FILL ON STRENGTH OF JOINTED SPECIMEN." Thesis, 2015. http://dspace.dtu.ac.in:8080/jspui/handle/repository/14368.
Full textAbstract:
ABSTRACT
Several, complicated and difficult structures are constructed or in
planning stages under complex geological conditions around the world. Even
small variation in analysis and design can cost significantly. It is well
recognized that the strength of rock masses depends upon the strain history,
extent of discontinuities, orientation of plane of weakness, condition of joints,
fill material in closely packed joints and extent of confinement. Several
solutions are available for strength of jointed rock mass with a set of
discontinuities. There is a great multiplicity in the proposed relationships for
the strength of jointed rocks. In the present study, the author conceives the
effect of increasing stresses to induce permanent strains. This permanent
strain appears as micro crack, macro crack and fracture. A fully developed
network of permanent deformations forms joint. The joint may contain
deposits of hydraulic and hydrothermal origin commonly known as a fill
which may have cementing tendency. The joint factor numerically captures
varied engineering possibilities of joints in a rock mass. The joints grow as an
effect of loading. The growth of the joints is progressive in nature. It
increases the joint factor, which modify the failure stresses. After extensive
experimentation significant joint properties affecting the strength of jointed
rocks with unfilled joints and joints with cemented fill has been evolved. This
factor is called joint modified factor in which number of joints per meter
length, orientation of joints and strength along joints and strength along joints
are clubbed together. As the in situ determinations of jointed rock mass is
costly and time consuming attempts are being made to predict the strength
and deformation of rock mass through model test under controlled laboratory
conditions
In the present work jointed rocks are simulated by preparing specimens
of mortar and cemented joints containing PoP were created artificially by
inducing paste of PoP inside the joints. The experimental investigations have
been carried on PoP cemented at varied joints possibilities specimen. The
specimen made of cement and standard sand in the ratio of 1:3 to simulate the
rock mass. The samples were cured at the interval of 7 days to create weakly
cemented rock mass and at 28 days to make a comparatively stronger rock
mass. The strength changes on 7 days and 28 days are incorporated in
relation to their peak compressive strength in presence of PoP cemented
joints. The specimen was tested under uniaxial compression to determine the
various parameters. The results have been analysed in relation to the
modified joint factor Trivedi(40) and a simple empirical approach has been
found to predict unconfined compressive strength of jointed rocks with PoP
cemented joints. The investigation indicates that the results are in conformity
with the recent analyses proposed by Trivedi [40].
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Teye, Vida Dede. "The effect of fill density on rectal balloon dosimetry." 2013. http://liblink.bsu.edu/uhtbin/catkey/1713805.
Full textAbstract:
Access to abstract permanently restricted to Ball State community only.Literature review -- Interaction of radiation with matter -- Radiation dosimetry -- Materials and methods -- Results -- Discursion.
Access to thesis permanenty restricted to Ball State community only.
Department of Physics and Astronomy
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Peng, Yang-Ching, and 彭揚景. "Investigation of the effect of cobalt concentration on the grindability of cemented carbide." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/36712686547623951853.
Full textAbstract:
碩士淡江大學
機械與機電工程學系碩士班
100
Glass molding process (GMP) is regarded as a very promising technique for mass producing high precision optical components such as spherical/aspheric glass lenses and free-form optics. However, only a handful of materials can sustain the chemical reaction, mechanical stress and temperature involved in the glass molding process and almost all of these mold materials are classified as hard-to-machine materials. This makes the machining of these materials to sub-micrometer form accuracy and nanometer surface finish a rather tough and expensive task. Amongst those handful choices, tungsten carbide (WC) is by far the most commonly used mold material in GMP industry. WC, also known as sintered/cemented WC with cobalt (Co) binder, is a metal matrix composite of WC particles and Co matrix. Cobalt concentration plays an important role in shaping mechanical properties of the obtained WC/Co materials. This research aimed to investigate the effect of Co concentration on the grindability of WC/Co materials. Efforts have been made to correlate grinding parameters such as spindle speed, cut depth and feed to the obtained surfaces. It is found that, despite of higher hardness values, better surface finish can be achieved on WC/Co specimen of lower Co concentration. In the present study, surface roughness (Ra) values better than 5nm and 10nm were obtained on WC/Co specimens of 0~3% and 6~13% Co concentrations respectively.
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Zhi-Huang, Juan, and 簡志晃. "Effect of Fill/Postfill Switch on the Quality of In jection olded Plastics." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/21464462925657940089.
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Chien, Cheng-hao, and 簡誠浩. "Effect of fill-in material in a flaw in pile on wave propagation." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/16418819246725428145.
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Bahorich, Benjamin Lee. "Examining the effect of cemented natural fractures on hydraulic fracture propagation in hydrostone block experiments." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6394.
Full textAbstract:
Micro seismic data and coring studies suggest that hydraulic fractures interact heavily with natural fractures creating complex fracture networks in naturally fractured reservoirs such as the Barnett shale, the Eagle Ford shale, and the Marcellus shale. However, since direct observations of subsurface hydraulic fracture geometries are incomplete or nonexistent, we look to properly scaled experimental research and computer modeling based on realistic assumptions to help us understand fracture intersection geometries. Most experimental analysis of this problem has focused on natural fractures with frictional interfaces. However, core observations from the Barnett and other shale plays suggest that natural fractures are largely cemented. To examine hydraulic fracture interactions with cemented natural fractures, we performed 9 hydraulic fracturing experiments in gypsum cement blocks that contained embedded planar glass, sandstone, and plaster discontinuities which acted as proxies for cemented natural fractures.
There were three main fracture intersection geometries observed in our experimental program. 1) A hydraulic fracture is diverted into a different propagation path(s) along a natural fracture. 2) A taller hydraulic fracture bypasses a shorter natural fracture by propagating around it via height growth while also separating the weakly bonded interface between the natural fracture and the host rock. 3) A hydraulic fracture bypasses a natural fracture and also diverts down it to form separate fractures. The three main factors that seemed to have the strongest influence on fracture intersection geometry were the angle of intersection, the ratio of hydraulic fracture height to natural fracture height, and the differential stress.
Our results show that bypass, separation of weakly bonded interfaces, diversion, and mixed mode propagation are likely in hydraulic fracture intersections with cemented natural fractures. The impact of this finding is that we need fully 3D computer models capable of accounting for bypass and mixed mode I-III fracture propagation in order to realistically simulate subsurface hydraulic fracture geometries.text
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Sun, Kuang-Tung, and 孫光東. "Effect of Setback Distance on Loading Behavior of Shallow Foundation in a Poorly Cemented Sandstone." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/31612276926453634638.
Full textAbstract:
碩士國立交通大學
土木工程系所
92
This study aims to investigate the effect of setback distance on the loading behaviors of the shallow foundation located on the crest of a slope of poorly cemented sandstone. Based on the loading curves and the phenomena of crack development during loading, the effect of setback distance of foundation bearing stress and the failure mechanisms are explored. From the observation, the foundation rock after failure can be categorized into three zones, the triangular active zone beneath the footing, the outer passive zone near the free surface and the transition zone between both. For a footing located on a horizontal ground, a symmetric failure mode with respect to the footing is observed at the foundation rock. Due to the existence of a slope, the failure mode of foundation rock for the footing located on a crest of an inclined ground is different with the footing on a horizontal surface. Because the volume of active zone at the slope side is less than that in the side of level ground, major fractures are developed at the active zone of the slope side. Consequently, the passive and transition zones connect and induce ruptures in the slope side. The ultimate bearing stress measured is due to lack of lateral support at the slope side, meanwhile the rock in the level ground side does not contribute to the bearing stress. Based on the experimental results, the fact reflects that the bearing capacity of the foundation on the slope crest varies with its setback distance. The bearing capacity increases with the increase of setback distance. The slope will not influence the bearing capacity while the failure surface does not extend to the slope. According to the results of loading tests conducted in this study, the bearing capacity is independent of the slope when the setback stance is more than 3 times of the width of the foundation (15 cm). Keywords : artificial poorly cemented sandstone , soft rock, foundation model for loading test , failure mechanism, setback distance, active zone, passive zone, transition zone, intact zone
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Lee, Chun-wei, and 李俊葦. "Unconfined compression test on Fiber-Reinforced Cemented Silt: Effect of Cement on Fiber Bonding Strength." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/77710101265756948487.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
104
Marginal soils (i.e., silt and clay) have not been a preferred option of a backfill material for reinforced soil structures due to its low shear strength and permeability. In this research, fiber-reinforced silt (FRS) and fiber-reinforced cemented silt (FCS) were studied as a measure of improving the stability of reinforced soil structures backfilled with marginal soil. A series of triaxial unconfined compression tests are perform to investigate the effect of adding polypropylene (PP) fibers and cement on the shear behavior and failure mode of silty soil subject to undrained loadings. The test variables considered in this study are fiber content (0, 1, 2, 3%), fiber length (6, 12, 19 mm) and cement content (0, 5%). The specimens were prepared at a maximum dry unit weight and optimum moisture content based on standard proctor compaction test results. For FCS specimens, the 7 day curing strength was obtained and compared in this study. The experimental results revealed that adding fiber and cement substantially increased the undrained shear strength and reduced the loss of post peak strength of the reinforced soil. The failure mode steadily transformed from brittle to ductile type as the fiber content increased. Test results also indicated that the modulus of FRS under working stress conditions (at 2% of axial strain) decreased as fiber content increased but increased as fiber length increased. Regardless of fiber content and length, the modulus of FRS is less than that of unreinforced silt, whereas the modulus of FCS is larger than that of unreinforced silt. The improvement of undrained shear strength as a result of cement-induced extra boning strength was determined by quantifying the strength increment between FRS and FCS specimens. The analytical results suggested that for reinforced specimens with 2 and 3% of fiber content the strength improvement from the contribution of cement-induced extra boning strength is larger than that from the contribution of fiber alone. This observation demonstrated the significance of adding cement as an adhesive to improve the bonding strength between fiber and soil matrix. As a result, higher fiber tensile strength could be mobilized and contributed to the increase of overall undrained shear strength of reinforced soil. Images acquired from scanning electron microscope (SEM) also provided clear visual evidences of soil-fiber interaction improved by adding cement.
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Wang, Bor-Hau, and 王柏皓. "Effect of Slope Inclination on the Loading Behavior of Shallow Foundation In a Poorly Cemented Sandstone." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/6f3dg7.
Full textAbstract:
碩士國立交通大學
土木工程系所
92
This thesis aims to investigate the loading behavior of shallow foundation in poorly cemented sandstone on slope crest where slope angles are 10 degree,20 degree and 30 degree . In this thesis, an artificial soft rock was developed as the foundation material. The mechanical behavior of the artificial rock is analogous to the natural sandstone. A set of laboratory loading equipments for foundation model was assembled. The samples were prepared and loaded in a steel box with the dimension of 60 cm x 30 cm x 65 cm. To observe the fracturing of the specimen during test, a observed window was made on the upper and central part of one of the wall of the box using high strength glasses . Then, twelve sets of model loading tests were performed in the laboratory. Base on these tests, not only the bearing capacity but also the mechanisms of progressive failure are investigated by image processing analysis. We explore the behavior of the shallow foundation of poorly cemented sandstone by the progressive failure and the analyzed results. To prepare the model material the sandstone was first gently crushed and ground in order to appropriately represent actual grain size distribution of the natural sandstone. After grinding, the rock grains passing #30 sieve and retaining on the #200 sieve were adopted as the basic model material. The solution passing #200 sieve was used as the cementing material for producing the artificial soft rock model. The particles and the solution with fines were mixed thoroughly with the ratio of 1:1 by volume. After that, their mixture was poured into a model container. The load on the specimen was slowly increased up to 250 tons step by step. After the consolidation stage completed, the specimen was extruded from the container and was exposed to electric fans for three weeks to produce an air-dried specimen; Then the specimen was ready for a load bearing tests. The results of model bearing test on slope crest indicate that a load-settlement curve is analogous to that on horizontal specimens. It also can be roughly divided into the incipient stage, the linear stage, the non-linear stage, and the final stage. The peak point of the load-settlement curve is the ultimate stress and decreases varies with slope angles. Generally speaking, the bearing capacity of 10 degree slope is approximately about 91 percent of horizontal specimens; the bearing capacity of 20 degree slope is approximately about 79 percent of horizontal specimens; the bearing capacity of 30 degree slope is approximately about 63 percent of horizontal specimens. At the incipient stage, the specimens have no obvious cracks. And at the linear stage , cracks just beneath both edges of footing could be observed, these cracks were likely due to the stress concentration near both footing edges and extended outward with the increasing bearing load. At the non-linear stage, as the cracks grows completely, it reaches the peak point of the load-settlement curve and an active zone right under the foundation base was clearly formed. At the failure stage, the active zone slide toward the slope faces and the bearing stress decreases. After tests, the failure zones and mechanism were also identified. Failure zones were divided into the active zone, the transitional zone, and the passive zone. Not only the horizontal specimens but the inclination specimens, it was found that the bearing behavior on poorly cemented sandstone is distinct from the cases on hard rock or soil, with both plasticity and brittle characteristics. The bearing capacity formulas commonly used for soil or hard rock is not necessarily suitable for the case of poorly cemented soft sandstone.
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Barker, D. S. "A numerical analysis of the effect of surface finish and cement creep in cemented total hip replacement." Thesis, 1996. http://hdl.handle.net/2440/120735.
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Jamali-Firouz-Abadi, Maryam. "Effect of Binder Content and Load History on the One-dimensional Compression of Williams Mine Cemented Paste Backfill." Thesis, 2012. http://hdl.handle.net/1807/35326.
Full textAbstract:
Large voids created by underground mining are backfilled to provide regional ground support. This thesis examines using conventional oedometer techniques and electromagnetic (EM) techniques to characterize consolidation and binder hydration in mine backfill so that EM monitoring can be used in the field to provide real-time feedback to operators to optimize the backfilling process.
New techniques are given for interpreting the full range of deformation (initial compression, primary and secondary consolidation). Deformation due to initial compression is non-trivial and may have to be accounted for in numerical back-analyses of field case studies. EM parameters are sensitive to binder content, progress of hydration and loss of water caused by consolidation and binder hydration.
The integrated interpretation of consolidation and EM behaviours has significant potential impact on real-time monitoring of mine backfill operations, and recommendations are made to advance the technique for this purpose.
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Alhaddad, Abdulrahman Jafar M. "Effect of real time aging and cyclic fatigue on fused and cemented machined veneers to Y-TZP zirconia." Thesis, 2016. https://hdl.handle.net/2144/18657.
Full textAbstract:
OBJECTIVES: The objectives of this study was to determine the differences in failure load between cemented and fused machined veneers to zirconia while observing the effects of real time aging on failure load between cemented and fused machined veneers to zirconia. The study was to examine the differences in aging and fatigue resistance amongst a machined glass-ceramic veneer and a machined feldspathic porcelain veneer.
MATERIALS AND METHODS: VITA In Ceram YZ zirconia blocks were used as a substructure framework for the three unit fixed partial denture. The veneering material was either milled IPS e.max CAD (glass-ceramic) or milled VITABLOCS Triluxe Forte (feldspathic porcelain). The types of linking material between the substructures and veneering material were either fusing or cementation. Observations were compared between aged and non-aged specimens divided into two main groups; (a) non-aged group (b) aged for three years at room temperature. Each group has two subgroups; fused and cemented which are further divided into static and cyclic fatigue at 20K, 60K and 80K. Specimens were subjected to load to failure test using universal test machine. 40% of failure load was calculated for the cyclic fatigue subgroups. In order to examine the difference in failure load between the static and fatigued specimens, the Tukey-Kramer HSD test was used to analyze the data.
RESULTS AND CONCLUSIONS: The VITABLOCS Triluxe Forte (feldspathic porcelain) fused to YZ zirconia showed significantly lower failure load values compared to all the other groups (p˂0.05). The non-aged VITABLOCS Triluxe Forte cemented to YZ zirconia (static and cyclic) showed significantly higher load to failure than the aged cemented Triluxe fatigued groups (p˂0.05). There is no significant difference in failure load between IPS e.max CAD fused and IPS e.max CAD cemented to YZ zirconia framework (p˃0.05). The aged IPS e.max CAD fatigued (20K, 60K and 80K cycles) cemented to YZ zirconia showed lower significant difference in failure load among all the other IPS e.max groups. (p˂0.05).
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Sahoo, Biranchi Narayan. "Effect of Cryogenic Treatment of Cemented Carbide Inserts on Properties & Performance Evaluation in Machining of Stainless Steel." Thesis, 2011. http://ethesis.nitrkl.ac.in/2811/1/PRINT.pdf.
Full textAbstract:
In this research work, the influence of cryogenic treatment on different characteristics of ISO P30 grade cemented carbide insert was studied, followed by performance evaluation in dry turning of AISI 316 grade austenitic stainless steels using untreated and cryo treated carbide inserts. Microstructural characterisation and crystallographic orientation were studied with the help of scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Chemical composition of the untreated and cryo treated inserts were determined using energy dispersive spectroscopy (EDS) through X-ray. Microhardness of the same specimens were evaluated using Vickers microhardness. The results indicated that cryo treatment resulted in formation of hard and wear resistant η phase carbides. At the same time, the concentration of binder phase i.e. cobalt on the top surface region increased. The turning tests were conducted at three different cutting speeds (100, 150, and 200 m/min.) while feed rate and depth of cut were kept constant at 0.2 mm/rev and 1 mm, respectively. The influences of cryogenic treatment were investigated on the average flank wear and chip characteristics. Both the worn parts of the cutting tools as well as the chips were also examined using optical microscopy and SEM. The results showed that cryogenic treatment significantly improved the average flank wear. The cryo treated demonstrated superior resistance to tool wear compared to its untreated counterpart in the entire range of cutting speeds. The chip thickness along with chip reduction coeffiecient was found to decrease for cryo treated insert compared to those for untreated insert during dry turning of AISI 316 grade austenitic stainless steel.
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Brumby, Scott Andrew. "The effect of surface roughness and a collar on fixation of cemented femoral stems in vivo / by Scott Andrew Brumby." Thesis, 1996. http://hdl.handle.net/2440/18921.
Full textAbstract:
Bibliography: leaves 193-206.xiii, 206 leaves : ill. (chiefly col.) ; 30 cm.
This thesis investigates the effect of femoral stem surface roughness and a collar on the fixation of cemented hip hemi-arthroplasty femoral stems in an in vivo sheep model up to nine months following implantation. Plain radiography, micromotion between prosthesis and bone during mechanical testing and histology are used.
Thesis (Ph.D.)--University of Adelaide, Dept. of Orthopaedics and Trauma, 1997?
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"Effect of Series Resistance Increase on Fill Factor of PV Cells Extracted from Field Aged Modules of Different Climates." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.40306.
Full textAbstract:
abstract: Solar photovoltaic (PV) industry is tipped to be one of the front-runners in the renewable industry. Typically, PV module manufacturers provide a linear or step warranty of 80% of original power over 25 years. This power loss during the field exposure is primarily attributed to the development of performance affecting defects in the PV modules. As many as 86 different defects can occur in a PV module. One of the major defects that can cause significant power loss is the interconnect metallization system (IMS) degradation which is the focus of this thesis. The IMS is composed of cell-interconnect (cell-ribbon interconnect) and string-interconnect (ribbon-ribbon interconnect). The cell interconnect is in turn composed of silver metallization (fingers and busbars) and solder bonds between silver busbar and copper ribbon. Weak solder bonding between copper ribbon and busbar of a cell results in increase of series resistance that in turn affects the fill factor causing a power drop. In this thesis work, the results obtained from various non-destructive and destructive experiments performed on modules exposed in three different climates (Arizona - Hot and Dry, Mexico - Warm and Humid, and California - Temperate) are presented. These experiments include light I-V measurements, dark I-V measurements, infrared imaging, extraction of test samples from the modules, peel strength measurements and four-point resistance measurements. The extraction of test samples was performed using a mechanical method and a chemical method. The merits and demerits of these two methods are presented. A drop of 10.33% in fill factor was observed for a 0.05Ω increase in the series resistance of the modules investigated in this work. Different combinations in a cell that can cause series resistance increase were considered and their effect on fill factor were observed using four-point probe experiments. Peel test experiments were conducted to correlate the effect of series resistance on the ribbon peel strength. Finally, climate specific thermal modelling was performed for 4 different sites over 20 years in order to calculate the accumulated thermal fatigue and also to evaluate its correlation, if any, with the increase of series resistance.Dissertation/Thesis
Masters Thesis Mechanical Engineering 2016
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El-Ebrashi, Sameh Kamal. "The effect of coping/die fit of procera aluminum oxide copings cemented with different cements a thesis submitted in partial fulfillment ... for the degree of Master of Science in Prosthodontics ... /." 1998. http://catalog.hathitrust.org/api/volumes/oclc/68800579.html.
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Hifeda, Nedda. "Bond strength between veneer porcelains and CAD/CAM ceramic to CP titanium and evaluation of fracture load and effect of aging on low fusing porcelain fired over CP TI and CAD / CAM materials cemented onto CP TI." Thesis, 2016. https://hdl.handle.net/2144/18673.
Full textAbstract:
OBJECTIVES: The aim of this study was to evaluate the bond strength of three different
veneering porcelains fired over CP Titanium and a CAD/CAM ceramic cemented to CP
Titanium.
METHODS: Sixty-four bars of CP Titanium grade II (25±1x 3±0.5x 0.5±0.05 mm) were
divided randomly into four groups: Group 1: Titankeramik (Vita Zahnfabrik), Group 2:
Triceram (Dentaurum), Group 3: Initial Ti (GC), and Group 4: MKII blocks (Vita). Each
veneer porcelain (groups 1-3) was applied with dimensions limited to 8x3x1mm and fired
on CP Ti bars following the manufacturer’s instructions and ISO 9693 recommendations.
Group 4, Vita Mark II blocks were sectioned into sixteen bars (8x3x1mm) and cemented
with Multilink Implant cement (Ivoclar) on CP Ti bars. Fifteen specimens from each
group were tested for bond strength by Schwickerath crack initiation test (ISO 9693)
using an Instron machine; the mode of failure and bond interface was evaluated by
SEM / EDS.
RESULTSs: The data were analyzed statistically using ANOVA and Tukey ≤ 0.05. Group 4 is
significantly higher than the other groups. Group 1 is significantly higher than group 3, but similar to group 2.
SEM/EDS analysis reveals that the modes of failure for groups 1 - 4 are a mixture of
adhesive, mixed, and cohesive failures.
CONCLUSION: Cementing a milled ceramic to CP Ti produces bond strength significantly
greater than conventional veneering porcelains.2018-09-28T00:00:00Z
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(8848484), Arturo Garcia. "EXPERIMENT AND MODELING OF COPPER INDIUM GALLIUM DISELENIDE (CIGS) SOLAR CELL: EFFECT OF AXIAL LOADING AND ROLLING." Thesis, 2020.
Find full textAbstract:
In this paper various applications of axial tensile load, bending load, and rolling loading has
been applied to a Copper Indium Gallium Diselenide (CIGS) Solar Cell to lean how it would affect
the solar cell parameters of: Open circuit voltage (Voc), Short circuit current, (Isc), Maximum power
(Pmax), and Efficiency (EFF), and Fill Factor (FF). These Relationships were found for with three
different experiments.
The first experiment the applies axial tensile stress is to a CIGS solar cell ranging from 0 to
200 psi with various strain rates: 0.0001, 0.001, 0.01, and 0.1 in/sec as well as various relaxation
time: 1min, 5min, and 10 min while the performance of solar cell is measured. The results of this
gave several trends couple pertaining the Voc . The first is that open circuit voltage increases
slightly with increasing stress. The second is the rate of increase (the slope) increases with longer
relaxation times. The second set of trend pertains to the Isc. The first is that short circuit current
generally is larger with larger stress. The second is there seems to be a general increase in the Isc
up to a given threshold of stress. After that threshold the Isc seems to decrease. The threshold stress
varies depending on strain rate and relaxation time.
The second set of experiments consisted of holding a CIGS solar cell in a fixed curved
position while it was in operational use. The radii of the curved cells were: 0.41, 0.20, 0.16, 0.13,
0.11, 0.094, and 0.082 m. The radii were performed for both concave and convex cell curvature.
The trends for this show a slight decrease in all cell parameters with decreasing radii, the exception
being Voc which is not effecting, the convex curvature causing a slightly faster decrease than the
concave. This set of experiments were also processed to find the trends of the single diode model
parameters of series resistance (Rs), shunt resistance (Rsh), dark current (I0), and saturation current
(IL), which agreed with the experimental results.
The second experiment consisted of rolling a CIGS solar cell in tensile (cells towards dowel.)
and compression (cells away from dowel) around a dowel to create internal damage. The diameter
of the dowels decreased. The dowel diameters were: 2. 1.75, 1.25, 1, 0.75, 0.5, and 0.25 inches.
This experiment showed similar trends as the bending one but also had a critical diameter of 1.75
in where beyond that damage much greater.
Finally a parametric study was done in COMSOL Multiphysics® to examine how changes
in the CIGS material properties of electron mobility (EM), electron life time, (EL), hole mobility
15
(HM), and Hole life time (HL) effect the cell parameters. The trends are of an exponential manner
that converges to a given value as the material properties increase. When EL, EM, HL are very
small, on the order of 10-4 times smaller than their accepted values, a transient like responses occurs.