Дисертації з теми "FLEXURAL STRENGHTH"
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1
Reutter, Oliver. "Assessment of masonary flexural bond strength." Thesis, Kingston University, 2007. http://eprints.kingston.ac.uk/20328/.
Повний текст джерелаАнотація:
This thesis presents the results of an experimental assessment of masonry flexural bond strength. Since there is insufficient experimental data on key performance requirements for bond between units and mortar, investigations into the development of bond and flexural strength across a range of masonry units for both traditional and new mortar types, reflecting the recent changes in European standards, were conducted. In order to demonstrate the performance of bond between unit and mortar, the latter ranging from weak to strong, a practical bond wrench testing rig was developed for use with couplets and stack bonded prisms. This involved carrying out investigations into existing designs and revaluations using up to date modelling techniques. The result is a new bond wrench applicable for use in laboratories and on site.
2
Choi, Wonchang. "Flexural Behavior of Prestressed Girder with High Strength Concrete." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-10302006-114609/.
Повний текст джерелаАнотація:
The advantages of using high strength concrete (HSC) have led to an increase in the typical span and a reduction of the weight of prestressed girders used for bridges. However, growing demands to utilize HSC require a reassessment of current provisions of the design codes. The objective of one of the research projects, recently initiated and sponsored by the National Cooperative Highway Research Program (NCHRP), NCHRP Project 12-64, conducted at North Carolina State University is to extend the use of the current AASHTO LRFD design specifications to include compressive strength up to 18,000 psi (124 MPa) for reinforced and prestressed concrete members in flexure and compression. This thesis deals with one part of this project. Nine full-size AASHTO girders are examined to investigate the behavior of using different concrete compressive strength and subjected to the flexural loadings. The experimental program includes three different configurations of prestressed girders with and without a deck slab to investigate the behavior for the following cases: 1) the compression zone consists of normal strength concrete (NSC) only; 2) the compression zone consists of HSC only; and 3) the compression zone consists of a combination of two different strengths of concrete. An analytical model is developed to determine the ultimate flexural resistance for prestressed girders with and without normal compressive strength concrete. The research also includes investigation of the transfer length and the prestress losses of HSC prestressed girders. Based on materials testing and extensive data collected from the literature, a new equation is proposed to calculate the elastic modulus for normal and high strength concrete.
3
Jackson, Rahsean LaNaul. "Vibration and Flexural Strength Characteristics of Composite Castellated Beams." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31242.
Повний текст джерелаАнотація:
With the development of lightweight concrete and design optimizations, floor vibration problems are becoming a serious serviceability problem. The castellated beam is a prime example and was the focus of this study. The vibration and flexural strength performance were verified in this paper.
The vibration characteristics of castellated beams were examined using experimental and analytical test methods. The effective moment of inertia is essential to accurately predict the frequency and deflection of a floor system due to human occupancy. Since castellated beams have non-prismatic cross-sections, their effective moment of inertia is an uncertainty and was verified in this study. This paper confirmed the accuracy of the AISC Design Guide procedures used in for prismatic beam, when applied to castellated beams.
The flexural strength of various composite castellated beam were studied. Three full-scale specimens were tested to failure to evaluate their yield and maximum applied load. Each specimensâ moment strength was verified based on span, beam properties, concrete slab, and amount of shear connection.
Master of Science
4
Heying, Jamie John Gratton David G. "Flexural strength of interim fixed prosthesis materials after simulated function." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/377.
Повний текст джерела
5
Hettiarachchi, M. T. P. "The theoretical prediction of the flexural strength of structural plywood." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/11768.
Повний текст джерела
6
Heying, Jamie John. "Flexural strength of interim fixed prosthesis materials after simulated function." Thesis, University of Iowa, 2009. https://ir.uiowa.edu/etd/377.
Повний текст джерелаАнотація:
Statement of Problem
There are limited studies evaluating the effect of a cyclic load on interim fixed prosthetic materials and its effect on flexural strength.
Purpose of Study
1) To verify the flexural strength of previously studied interim fixed prosthetic materials.
2) To establish the flexural strength of new, advanced generation and untested interim fixed prosthetic materials.
3) To determine the effect of cyclic load on the flexural strength of interim fixed prosthetic materials.
Materials and Methods
Bar-type specimens of Caulk Temporary Bridge Resin, VitaVM CC, Protemp 3 Garant and Radica were fabricated according to International Standards Organization 4049 and American National Standards Institute/American Dental Association specification 27. After being stored in distilled water for 10 days, specimens were divided into Noncycled and Cycled Groups. The Noncycled Group specimens were fractured under a 3-point loading in a Bose Electroforce 3300 testing instrument at a crosshead speed of 0.75 mm/min. Cycled Groups specimens underwent a 6-12 Newton 3 Hertz cyclic load for 20,000 cycles in a Bose Electroforce 3300 testing instrument. Immediately following completion of the cycles, the specimens were fractured under a 3-point loading. Maximal loads to fracture in Newtons were recorded and mean flexural strengths were calculated (n = 20 per group). Comparisons were made with analysis of variance and Tukey's Multiple Comparison Test.
Results
Noncycled (NC) and Cycled (C) groups order of mean flexural strengths (MPa) from lowest to highest mean were as follows: Caulk (Noncycled - 53.83; C - 60.02), Vita VM CC (NC - 65.96; C - 66.83), Protemp 3 Garant (NC - 75.85; C - 77.18), and Radica (NC - 106.1; C - 115.96). In the Noncycled and Cycled groups, Radica was statistically superior when compared to all materials and Protemp 3 Garant was statistically superior to Caulk Temporary Bridge Resin. There was no statistically significant difference between the material's flexural strengths before and after cycles.
Conclusion
Within the limitations of this study, 20,000 cyclic loads of 6-12 Newtons at 3 Hertz did not have a significant effect on the flexural strength of interim fixed prosthetic materials. Radica demonstrated significantly superior flexural strength over other materials tested.
7
MATSUDA, SIGUERU O. "Estudo de algumas variaveis de processamento na resistencia mecanica a flexao de refratarios de SiC ligado a Sisub(3)Nsub(4)." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10827.
Повний текст джерелаАнотація:
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Dissertacao [Mestrado]
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
8
Carlson, Ryne. "Flexural Strength of Steel Beams with Holes in the Tension Flange." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563527519192391.
Повний текст джерела
9
Higgs, Arek Tilmann. "Shear and Flexural Capacity of High Strength Prestressed Concrete Bridge Girders." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1757.
Повний текст джерелаАнотація:
The section of highway over the 400 South roadway in Orem, Utah is made up of two separate three span bridges. The bridges were originally constructed in 1960 and were expanded in 2004 to accommodate for one extra lane per bridge. During the fall of 2012 both bridges were scheduled for demolition and four girders were salvaged from the southernmost span of the 2004 expansion. These girders were transported to the Structural Materials And Systems Health Lab (SMASH Lab) where a series of tests were performed to determine the prestressing losses, flexural, shear, and shear-flexure capacity of the girders. The results of these tests were compared to the American Association of State Highway and Transportation Officials Load Resistance Factored Design (AASHTO LRFD) Bridge Design Specifications and an ANSYS Finite Element model. For all test results the AASHTO Bridge Design was conservative for each test setup and was able to predict the type of failure that occurred. The finite element model was developed for the four test conditions and calibrated so as to accurately represent test data. The calibrations were compared to actual tested material properties to determine the difference between the theoretical model and the girders. (120 pages)
10
Peng, Jun, and 彭军. "Strain gradient effects on flexural strength and ductility design of normal-strength RC beams and columns." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48329630.
Повний текст джерелаАнотація:
The stress-strain characteristics of concrete developed in flexure is very important for flexural strength design of reinforced concrete (RC) members. In current RC design codes, the stress-strain curve of concrete developed in flexure is obtained by scaling down the uni-axial stress-strain curve to account for the strain gradient effect. Therefore, the maximum concrete stress that can be developed under flexure is smaller than its uni-axial strength, and the use of which always underestimates the flexural strength of RC beams and columns even though the safety factors for materials are taken as unity. Furthermore, the value of strength underestimation was different for RC beams and columns, which indicates that the extent of strain gradient will affect the maximum concrete stress and stress-strain curve developed under flexure.
To investigate the maximum concrete stress, 29 column specimens were fabricated and tested in this study. They were divided into 9 groups, each of which was poured from the same batch of concrete and contained specimens with identical cross-section properties. In each group, one specimen was tested under concentric load while the rest was/were subjected to eccentric or horizontal load. To study the strain gradient effects, the ratio of the maximum concrete compressive stress developed in the eccentrically/horizontally loaded specimens to the maximum uni-axial compressive stress developed in the counterpart concentrically loaded specimens, denoted by k3, is determined based on axial force and moment equilibriums. Subsequently, the concrete stress block parameters and the equivalent rectangular concrete stress block parameters are determined. It is found that the ratios of the maximum and equivalent concrete stress to uni-axial cylinder strength, denoted respectively by k3 and , depend significantly on strain gradient, while that of the depth of stress block to neutral axis depth, denoted by , remains relatively constant with strain gradient. Design equations are proposed to relate and with strain gradient for strength calculation, whose applicability is verified by comparing the strengths of RC beams and columns tested by various researchers with their theoretical strengths predicted by the proposed parameters and those evaluated based on provisions of RC codes.
Based on the test results, the stress-strain curve of normal-strength concrete (NSC) developed under strain gradient is derived using least-square method by minimising the errors between the theoretical axial load and moment and the respective measured values. Two formulas are developed to derive the flexural stress-strain curve, whose applicability is verified by comparing the predicted strength with those measured by other researchers.
Lastly, the application of the proposed stress-block parameters and stress-strain curve of NSC will be illustrated by developing some charts for flexural strength design of NSC beams and columns. The application will further be extended to develop strength-ductility charts for NSC beams and columns, which enable simultaneous design of strength and ductility. By adopting the proposed design charts, the flexural strength design, as well as that of the plastic hinge forming mechanism during extreme events, will be more accurate. The resulting design will be safer, more environmentally friendly and cost effective.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
11
Yosefani, Anas. "Flexural Strength, Ductility, and Serviceability of Beams that Contain High-Strength Steel Reinforcement and High-Grade Concrete." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4402.
Повний текст джерелаАнотація:
Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes.
The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement.
The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking.
The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone (Φ); evaluation of the minimum reinforcement ratio (þmin); recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, λ, which does not consider the yield strength of reinforcement and the concrete grade.
12
Brahmachari, Koushik, of Western Sydney Hawkesbury University, of Science Technology and Agriculture Faculty, and School of Construction and Building Sciences. "Connection and flexural behaviour of steel RHS filled with high strength concrete." THESIS_FTA_CBS_BRAHMACHARI_K.xml, 1997. http://handle.uws.edu.au:8081/1959.7/526.
Повний текст джерелаАнотація:
Steel hollow section members filled with concrete have been frequently used in recent construction industry as columns and beams and beam-columns because of their superior performance and constructability. Previous research demonstrated that such system has large energy absorption capacity which is critical in the event of an earthquake. By filling steel RHS with concrete, the failure of the steel shell due to local buckling can be delayed and the ductility of the concrete core can be improved as a result of the confinement of the steel shell. This type of composite section may be used in various structures including frames of high rise buildings, bridges, offshore structures, cast-in-situ piles in foundation etc. Design methods for concrete-filled steel tubular sections are recommended in a number of code of practices. Due to the significant differences in the material properties between normal strength concrete and high strength concrete, there is a need to study the behaviour of composite sections with higher strength concretes. The study emphasises ultimate strength, ductility, post-failure strength reserve and interface bond. It also emphasises ductility and post-failure strength of the composite beams due to the brittle behaviour of higher strength concretes when compared to normal strength concrete. Spreadsheet graph were used to present the results such as load versus strains, load versus deflections etc. In this thesis analytical study is presented on the calculation of ultimate moment of resistance of the concrete-filled RHS beams. Among the main considerations of the derivation, the steel portion was assumed either elastic-perfectly plastic or perfectly plastic and concrete carries no strength in the tensile zone. At the interface both full bond and partial bond were assumed for comparison. Efforts were also made to calculate the midspan deflections of the composite beams. Simple analytical expressions derived from this study can be coded to a prgrammable calculator or in a small spreadsheet program for design use. Finite element studies were carried out by using a proprietorship software package ANSYS. In the analysis of concrete-filled, three types of elements with large deformation and nonlinear capabilities were used. A plastic shell element, a solid concrete element with cracking and crushing capabilities, and a nonlinear spring contact element were used to model the steel shell, the concrete core and the interface respectively.Doctor of Philosophy (PhD)
13
Tabassum, Javeria, and javeriaajaz@yahoo co in. "Analysis of current methods of flexural design for high strength concrete beams." RMIT University. Civil, Environmental & Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080725.143153.
Повний текст джерелаАнотація:
Considerable amount of research was carried out into the properties and structural performance of high strength concrete for more than few decades. Whilst this research has produced relevant and useful results, there are several properties of high strength concrete like compressive and tensile strengths, stiffness, durability etc. that need to be evaluated and investigated to determine an accurate representation for the determination of different structural properties of beams made of high strength concrete. For this purpose, an investigation into the behaviour of beams made of higher concrete strengths has been carried out and conclusions drawn for the design of high strength concrete beams in flexure. Experimental data from previous research was considered for the study to establish some understanding of flexural behavior of HSC beams. A number of spreadsheets in Excel were developed using available data and various graphs were plotted to determine the accuracy of the code provisions for calculating the ultimate moment capacity of beams. A study on flexural ductility of beams has been carried out using a computer program FRMPHI which generates moment-curvature curves for the beams. Ductility has been studied using ductility factors. The influence of ductility on the value of the depth of neutral axis has been analysed and discussed. A chapter on the short-term deflection of simply supported high strength concrete beams under instantaneous deflections is presented. This chapter includes analysis of the available formula to calculate deflection to determine if these can be adopted for high strength concrete. Extensive ongoing research on the shear strength of beams by several researchers since many years has lead to the generation of a large body of knowledge. Although each author has analysed the data comparing them with existing relationships, the whole body of information has not been analysed to establish a statistical significance. In this study, regression analysis on experimental data collected from published research is carried a relationship between the different parameters affecting the shear strength of beams. The level of significance of the association between parameters influencing shear strength is also discussed.
14
Azzam, Mai Ahmed. "Flexural strength comparison of monolayer resin composite to bilayer resin/ liner composite." Thesis, Connect to resource online, 2009. http://hdl.handle.net/1805/2077.
Повний текст джерелаАнотація:
Thesis (M.S.D.)--Indiana University School of Dentistry, 2009.Title from PDF t. p. (viewed Feb. 5, 2010) Advisor(s): Jeffrey A. Platt, Chair of the Research Committee, Joseph Legan, Carl J. Andres, David Brown, Burak Taskonak . Curriculum vitae. Includes abstract. Includes bibliographical references (leaves 45-52).
15
Brahmachari, Koushik. "Connection and flexural behaviour of steel RHS filled with high strength concrete." Thesis, View thesis, 1997. http://handle.uws.edu.au:8081/1959.7/526.
Повний текст джерелаАнотація:
Steel hollow section members filled with concrete have been frequently used in recent construction industry as columns and beams and beam-columns because of their superior performance and constructability. Previous research demonstrated that such system has large energy absorption capacity which is critical in the event of an earthquake. By filling steel RHS with concrete, the failure of the steel shell due to local buckling can be delayed and the ductility of the concrete core can be improved as a result of the confinement of the steel shell. This type of composite section may be used in various structures including frames of high rise buildings, bridges, offshore structures, cast-in-situ piles in foundation etc. Design methods for concrete-filled steel tubular sections are recommended in a number of code of practices. Due to the significant differences in the material properties between normal strength concrete and high strength concrete, there is a need to study the behaviour of composite sections with higher strength concretes. The study emphasises ultimate strength, ductility, post-failure strength reserve and interface bond. It also emphasises ductility and post-failure strength of the composite beams due to the brittle behaviour of higher strength concretes when compared to normal strength concrete. Spreadsheet graph were used to present the results such as load versus strains, load versus deflections etc. In this thesis analytical study is presented on the calculation of ultimate moment of resistance of the concrete-filled RHS beams. Among the main considerations of the derivation, the steel portion was assumed either elastic-perfectly plastic or perfectly plastic and concrete carries no strength in the tensile zone. At the interface both full bond and partial bond were assumed for comparison. Efforts were also made to calculate the midspan deflections of the composite beams. Simple analytical expressions derived from this study can be coded to a prgrammable calculator or in a small spreadsheet program for design use. Finite element studies were carried out by using a proprietorship software package ANSYS. In the analysis of concrete-filled, three types of elements with large deformation and nonlinear capabilities were used. A plastic shell element, a solid concrete element with cracking and crushing capabilities, and a nonlinear spring contact element were used to model the steel shell, the concrete core and the interface respectively.
16
Brahmachari, Koushik. "Connection and flexural behaviour of steel RHS filled with high strength concrete /." View thesis, 1997. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030708.160244/index.html.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of Western Sydney, Hawkesbury."Thesis presented for the Degree of Doctor of Philosophy, School of Construction and Building Sciences, Faculty of Science, Technology and Agriculture, University of Western Sydney, Hawkesbury, December 1997.
17
Ribeiro, Daniela Garcia [UNESP]. "Efeito da irradiação por microondas sobre a resistência à flexão e dureza de resinas acrílicas para reembasamento imediato." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/97304.
Повний текст джерелаАнотація:
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ribeiro_dg_me_arafo.pdf: 507473 bytes, checksum: 1c6ba03d7141c053da8a5a15fc65d0c1 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O uso do microondas tem sido indicado como um método efetivo na desinfecção de resinas acrílicas. Entretanto, há pouca informação sobre o efeito da irradiação do microondas nas propriedades mecânicas desses materiais. Considerando esses aspectos, o objetivo deste estudo foi avaliar o efeito da irradiação por microondas sobre as propriedades mecânicas de resistência à flexão e dureza de resinas acrílicas. Os corpos-de-prova para a realização dos testes mecânicos foram confeccionados com os seguintes materiais: Kooliner (K), Tokuso Rebase Fast (TR), Ufi Gel Hard C (UGH) e New Truliner (NT), todas resinas indicadas para reembasamento imediato, e Lucitone 550 (L), que é uma resina para base de prótese. Para cada material foram confeccionados 48 corpos-de-prova que foram divididos igualmente em seis grupos. As resinas autopolimerizáveis (K, TR, UGH e NT) foram submetidas à irradiação logo após a confecção, enquanto que os corpos-de-prova da resina termopolimerizável (L) permaneciam 50 l 2 horas em água a 37ºC l 1ºC antes da irradiação. Para o procedimento de irradiação, cada corpo-de-prova foi individualmente imerso em 200 mL de água destilada e submetido a dois ciclos de irradiação pelas microondas, para simular o envio da prótese ao laboratório e o retorno dela ao consultório odontológico. Cada corpo-de-prova foi irradiado a uma potência constante de 650 W, variando-se o tempo de exposição: 1 minuto (T1), 2 minutos (T2), 3 minutos (T3), 4 minutos (T4) ou 5 minutos (T5). O grupo controle (T0) foi submetido aos testes mecânicos sem ser irradiado pelas microondas. Os ensaios de resistência à flexão para todos os corpos-de-prova foram realizados em máquina MTS-810 Material Test System sob velocidade de 5 mm/minuto, utilizando o teste em três pontos a uma distância de 50 mm entre os apoios. Em seguida, um dos fragmentos do...
Microwave irradiation was previous suggested as an effective method for the disinfection of acrylic resins. However, little information is available concerning the effect of microwave irradiation on the mechanical properties of acrylic resins. The purpose of this study was to evaluate the effect of two cycles of a microwave disinfection procedure on the flexural strength and Vickers hardness of acrylic resins. Four autopolymerized resins (Kooliner- K, Tokuso Rebase Fast- TR, Ufi Gel Hard- UGH and New Truliner- NT) and one heat-cured resin (Lucitone 550- L) were used for preparing specimens. For each material, 48 specimens were made and equally divided into six groups. The relined specimens were submitted to disinfection procedures after polymerization and the denture base polymer specimens were stored in water for 50 l 2 hours at 37ºC l 1ºC prior to disinfection. The specimens were individually immersed in 200 mL of destilated water and microwaved twice, simulating when dentures come from the patient and before being returned to the patient. Each cycle of microwave disinfection was performed at 650 W for one of the following irradiation times: 1 minute (T1), 2 minutes (T2), 3 minutes (T3), 4 minutes (T4) or 5 minutes (T5). Control group (T0) specimens were subjected to mechanical tests without being disinfected. The flexural strength values of the materials were determined using a testing machine MTS-810 at a crosshead speed of 5 mm/minute using a three-point bending fixture with a span of 50 mm. Thereafter, one fragment of specimen was submitted to Vickers microhardness test. The values were determined by using a 25 gf load, after 30 seconds contact. Twelve hardness measurements were taken on each specimen and the average was then calculated. The flexural and hardness values were submitted to ANOVA and ...(Complete abstract, click electronic access below)
18
Mohr, Benjamin Alan. "Investigation of Ultimate Bending Strength of Steel Bracket Plates." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31172.
Повний текст джерелаАнотація:
Currently, the design model for flexural rupture of an eccentrically loaded bracket plate is based on the material tensile rupture strength times the net elastic section modulus. Different bolt and plate sizes were tested to determine if this model is correct. It was found that the current model is conservative and that the material tensile rupture strength times the net plastic section modulus is a superior design model. Also, limited finite element modeling was performed to predict the elastic stiffness of such connections. The resulting data correlates well with test results, and confirms that most of the connection ductility comes from bolt plowing. These results can be used for splice plate connections in cantilever construction, as well.Master of Science
19
Islam, Md Shahidul. "Shear capacity and flexural ductility of reinforced high- and normal-strength concrete beams." Thesis, Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1766536X.
Повний текст джерела
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Alawadhi, Khaled N. "Correlation between flexural strength and denture base acrylic thickness overlaying implant stud attachments." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11245.
Повний текст джерелаАнотація:
Thesis (M.S.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains viii, 49 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 41-48).
21
Lee, Stephen Kim Lon. "Flexural strength of reinforced concrete beams strengthened using carbon fibre reinforced composite sheets." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420192.
Повний текст джерела
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ARAUJO, AELLINGTON FREIRE DE. "EXPERIMENTAL STUDY ON THE FLEXURAL STRENGTH OF CONCRETE BEAMS PRESTRESSED WITH SYNTHETIC TENDONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1927@1.
Повний текст джерелаАнотація:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORNos últimos anos a protensão externa tem sido empregada tanto na recuperação e reforço de estruturas existentes quanto na concepção de novas estruturas. A protensão externa pode ser feita com cabos de aço ou com cabos sintéticos. Dentre esses, podem-se destacar os cabos Parafil, cujo núcleo é constituído de fibras kevlar. Essas fibras têm alta resistência (3700MPa), alto módulo de elasticidade (126000MPa) e excelente resistência à corrosão. Neste trabalho é feito um estudo do comportamento de vigas protendidas com cabos externos tipo Parafil, onde se identificam os principais fatores que influenciam a resistência à flexão através de um estudo paramétrico, utilizando um modelo computacional desenvolvido por Krüger (1989) e Campos (1993). Foram ensaiadas experimentalmente cinco vigas protendidas com dois cabos externos, considerando a taxa de armadura passiva e o tipo de carregamento como principais variáveis. Os resultados mostram que a taxa de armadura passiva, o tipo de carregamento, o módulo de elasticidade do reforço, a resistência do concreto e o nível de protensão inicial (protensão efetiva) têm um efeito significante sobre a resistência à flexão das vigas. Os resultados teóricos obtidos através de equações desenvolvidas para o caso de cabos de aço, mostram, de um modo geral, bons resultados para o caso de cabos Parafil.
External prestressing has been used either in new structures or in the repair and rehabilitation of existing ones. The use of steel tendons has been the most usual solution, but synthetic cables have also been used over the last years. One example of these cables is a parallel-lay rope known as Parafil, which is made from the high strength (3700 MPa), high modulus (126000 MPa) and corrosion resistant fiber commercially known as Kevlar. An investigation on the behavior of beams prestressed with external Parafil tendons is conducted with the purpose of studying the flexural strength of these beams. The main variables which affect the behavior of the beams are firstly identified through a parametric analysis using an existing computational model based on the finite element method. Secondly, an experimental investigation of five simple supported beams, in which the non-prestressed reinforcement and type of loading are the main variables, is presented. The results show that the non-prestressed reinforcement, type of loading, elastic modulus of the tendons, effective prestressing force level and concrete strength have a significant affect on the flexural strength of the beams. The comparison between the experimental results and those obtained from equations developed for steel tendons, shows that these equations could also be used for beams prestressed with synthetic cables.
En los últimos años la protensión externa há sido empleada tanto en la recuperación y refuerzo de extructuras existentes como en la concepción de nuevas extructuras. La protensión externa puede ser realizada con cables de acero o con cables sintéticos. Dentro de estos, se pueden destacar los cables Parafil, cuyo núcleo está constituido de fibras kevlar. Esas fibras tienen alta resistencia (3700MPa), alto módulo de elasticidad (126000MPa) y excelente resistencia a la corrosión. En este trabajo se realiza un estudio del comportamientode vigas protendidas con cables externos tipo Parafil, donde se identifican los principales factores que tienen influencia sobre la resistencia a la flexión, a través de un estudio paramétrico, utilizando un modelo computacional desarrollado por Krüger (1989) y Campos (1993). Fueron ensayadas cinco vigas protendidas con dos cables externos, considerando como principales variables la tasa de armadura pasiva y el tipo de carga. Los resultados muestran que la tasa de armadura pasiva, el tipo de carga, el módulo de elasticidad del refuerzo, la resistencia del concreto y el nível de protensión inicial (protensión efectiva) tienen un efecto significativo sobre la resistencia a la flexión de las vigas. Los resultados teóricos obtenidos a través de las ecuaciones desarrolladas para el caso de cables de acero, muestran, de un modo general, buenos resultados para el caso de cables Parafil.
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Reynolds, Kevin Brandt. "Evaluation of the flexural strength of cold-formed steel studs with embossed flanges." Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1504.
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Roth, Michael Jason 1975. "Flexural and tensile properties of thin, very high-strength, fiber-reinforced concrete panels." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11062007-215816.
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Carter, Jeffrey Scott. "Effects of Low Velocity Impact on the Flexural Strength of Composite Sandwich Structures." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1327.
Повний текст джерелаАнотація:
The use of composite sandwich structures is rapidly increasing in the aerospace industry because of their increased strength-to-weight and stiffness-to-weight characteristics. The effects of low velocity impacts on these structures, however, are the main weakness that hinders further use of them in the industry because the damages from these loadings can often be catastrophic. Impact behavior of composite materials in general is a crucial consideration for a designer but can be difficult to describe theoretically. Because of this, experimental analysis is typically used to attempt to describe the behavior of composite sandwiches under impact loads. Experimental testing can still be unpredictable, however, because low velocity impacts can cause undetectable damage within the composites that weaken their structural integrity. This is an important issue with composite sandwich structures because interlaminar damage within the composite facesheets is typical with composites but the addition of a core material results in added failure modes. Because the core is typically a weaker material than the surrounding facesheet material, the core is easily damaged by the impact loads. The adhesion between the composite facesheets and the core material can also be a major region of concern for sandwich structures. Delamination of the facesheet from the core is a major issue when these structures are subjected to impact loads.
This study investigated, through experimental and numerical analysis, how varying the core and facesheet material combination affected the flexural strength of a composite sandwich subjected to low velocity impact. Carbon, hemp, aramid, and glass fiber materials as facesheets combined with honeycomb and foam as core materials were considered. Three layers of the same composite material were laid on the top and bottom of the core material to form each sandwich structure. This resulted in eight different sandwich designs. The carbon fiber/honeycomb sandwiches were then combined with the aramid fiber facesheets, keeping the same three layer facesheet design, to form two hybrid sandwich designs. This was done to attempt to improve the impact resistance and post-impact strength characteristics of the carbon fiber sandwiches. The two and one layer aramid fiber laminates on these hybrid sandwiches were always laid up on the outside of the structure. The sandwiches were cured using a composite press set to the recommended curing cycle for the composite facesheet material. The hybrid sandwiches were cured twice for the two different facesheet materials. The cured specimens were then cut into 3 inch by 10 inch sandwiches and 2/3 of them were subjected to an impact from a 7.56 lbf crosshead which was dropped from a height of 38.15 inches above the bottom of the specimen using a Dynatup 8250 drop weight machine.
The impacted specimen and the control specimen (1/3 of the specimens not subjected to an impact) were loaded in a four-point bend test per ASTM D7250 to determine the non-impacted and post-impact flexural strengths of these structures. Each sandwich was tested under two four-point bend loading conditions which resulted in two different extension values at the same 100 lbf loading value. The span between the two supports on the bottom of the sandwich was always 8 inches but the span between the two loading pins on the top of the sandwich changed between the two loading conditions. The 2/3 of the sandwiches that were tested after being impacted were subjected to bending loads in two different ways. Half of the specimens were subjected to four-point bending loads with the impact damage on the top facesheet (compressive surface) in between the loading pins; the other half were subjected to bending loads with the damage on the bottom facesheet (tensile surface).
Theoretical failure mode analysis was done for each sandwich to understand the comparisons between predicted and experimental failures. A numerical investigation was, also, completed using Abaqus to verify the results of the experimental tests. Non-impacted and impacted four-point bending models were constructed and mid-span deflection values were collected for comparison with the experimental testing results. Experimental and numerical results showed that carbon fiber sandwiches were the best sandwich design for overall composite sandwich bending strength; however, post-impact strengths could greatly improve. The hybrid sandwich designs improved post-impact behavior but more than three facesheet layers are necessary for significant improvement. Hemp facesheet sandwiches showed the best post-impact bending characteristics of any sandwich despite having the largest impact damage sizes. Glass and aramid fiber facesheet sandwiches resisted impact the best but this resulted in premature delamination failures that limited the potential of these structures. Honeycomb core materials outperformed foam in terms of ultimate bending loads but post-impact strengths were better for foam cores. Decent agreement between numerical and experimental results was found but poor material quality and high error in material properties testing results brought about larger disagreements for some sandwich designs.
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Chen, Mantai, and 陈满泰. "Combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206429.
Повний текст джерелаАнотація:
The stress-strain relationship of concrete in flexure is one of the essential parameters in assessing the flexural strength and ductility of reinforced concrete (RC) structures. An overview of previous research studies revealed that the presence of strain gradient would affect the maximum concrete stress and respective strain developed in flexure. Previously, researchers have conducted experimental studies to investigate and quantify the strain gradient effect on maximum concrete stress and respective strain by developing two strain-gradient-dependent factors k3 and ko for modifying the flexural concrete stress-strain curve.
In this study, the author established a new analytical concrete constitutive model to describe the stress-strain behavior of both normal-and high-strength concrete in flexure with the effect of strain gradient considered. Based on this, comprehensive parametric studies have been conducted to investigate the combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns with concrete strength up to 100 MP a by employing the strain-gradient-dependent concrete stress-strain curve using non-linear moment-curvature analysis.
From the results of the parametric studies, it is evident that both the flexural strength and ductility of RC beams and columns are improved under strain gradient effect. A design value of ultimate concrete strain of 0.0032and anew equivalent rectangular concrete stress block incorporating the combined effects of strain gradient and concrete strength have been proposed and validated by comparing the proposed theoretical strength with the strength of 198 RC beams and 275 RC columns measured experimentally by other researchers. It is apparent from the comparison that the proposed equations can predict more accurately the flexural strength of RC beams and columns than the current RC design codes.
Lastly, for practical engineering design purpose, design formulas and charts have been produced for flexural strength and ductility design of RC beams and columns incorporating the combined effects of strain gradient and concrete strength.published_or_final_version
Civil Engineering
Master
Master of Philosophy
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Asia, Winifred. "An in-vitro study of the physical properties of core build-up materials." University of the Western Cape, 2017. http://hdl.handle.net/11394/6307.
Повний текст джерелаАнотація:
Magister Chirurgiae Dentium - MChD (Prosthodontics)The aim of this study was to evaluate and compare the physical properties of two core build-up materials (ParaCore and CoreXflow) and compare this to conventional composite material (Filtek Supreme Plus and SDR Flow) used as core build-up material.
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Yang, Jing 1988. "Grinding effects on surface integrity, flexural strength and contact damage resistance of coated hardmetals." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/396135.
Повний текст джерелаАнотація:
This thesis assesses the influence of substrate surface integrity on different mechanical (flexural strength and contact damage resistance under spherical indentation) and tribological (scratch resistance as well as cracking and delamination response under Brale indentation) properties for a TiN-coated fine-grained hardmetal grade (WC-13 wt.%Co). In doing so, three different surface finish conditions are studied: as-sintered (AS), ground (G), mirror-like polished (P) and ground plus thermal annealed (GTT). Moreover, a relevant part of the work is devoted to nude hardmetal substrates.
The result indicates that grinding induces significant alterations in the surface integrity. It yielded in high roughness and emergence of a topographic texture; anisotropic distribution of microcracks within a thin subsurface layer; severe deformation, microstructure refinement and phase transformation of binder regions; and large compressive residual stresses. Subsequent ion etching and coating deposition resulted in a significant residual stresses decrease while damage induced by grinding was not completely removed in the substrate surface. On the other hand, high temperature annealing (GTT condition) completely relieved the referred residual stresses, but without inducing any additional change in terms of existing damage. This was not the case for the metallic binder phase where such treatment induced an unexpected microporosity, development of a recrystallized subgrain structure and reversion of grinding-induced phase transformation.
Strength of hardmetals was significantly enhanced by grinding, as compared to AS and P conditions. Such beneficial effect is partly lost during the subsequent ion etching and coating deposition stages. On the other hand, strength of coated GTT condition increases compared to that of the corresponding uncoated one. Systematic residual stress analysis combined with extensive fractographic inspection reveal that strength variations measured after individual manufacturing chain or heat treatment steps (grinding, ion-etching, coating and/or thermal annealing) may be rationalized on the basis of effective residual stress state and location, either at the surface or at the subsurface, of strength-controlling flaws.
Independent of substrate surface finish, coated AS, G and P samples exhibit similar critical load for initial substrate exposure as well as same predominant failure mode as they get scratched. However, clear differences in the failure scenario were evidenced. Scratch track for G samples exhibited discrete and localized substrate exposure, compared to the more pronounced and continuous exposure for AS and P ones. On the other hand, GTT samples showed lower critical load and changes in the mechanisms for the scratch-related failure; the latter depending on the relative orientation between scratch and grinding directions.
Coated hardmetals exhibit more brittleness and lower adhesion strength, under Brale indentation testing conditions, with decreasing binder content. Grinding is discerned to promote delamination, compared to the polished condition, but also to strongly inhibit radial cracking. Such a response is analyzed on the basis of the interaction between elastic-plastic deformation imposed during indentation and several grinding-induced effects: remnant compressive stress field, pronounced surface texture and microcracking within a thin microcracked subsurface layer.
Contact damage resistance of coated hardmetals, subjected to spherical indentation, is enhanced by grinding of the substrate previous to coating stage. Such beneficial effects are discerned regarding both crack nucleation at the coating surface and subsequent propagation into the hardmetal substrate. The grinding-induced compressive residual stresses are pointed out as the main reason for the improved response against contact loading. Such statement is sustained by the lower damage resistance evidenced in coated GTT specimens.En este trabajo se estudia la influencia de la integridad superficial del sustrato sobre diferentes propiedades mecánicas (resistencia tanto a la rotura en flexión como al daño inducido por contacto) y tribológicas (resistencia al rayado así como el comportamiento bajo solicitaciones de indentación Brale) de una calidad fina de metal duro (WC-13% peso Co) recubierta con una capa de TiN. La investigación incluye la consideración de cuatro acabados superficiales: en condiciones de sinterizado (AS), rectificado (G), pulido (P), y rectificado más un tratamiento térmico de recocido (GTT). Los resultados indican que el rectificado induce alteraciones importantes en la integridad superficial: se incrementa la rugosidad y emerge una textura superficial; se evidencia la existencia de microfisuras, anisotrópicamente distribuidas a nivel subsuperficial; se introduce una deformación muy severa, lo cual da lugar a un refinamiento de la microestructura y transformación de fase en el ligante metálico; y finalmente, se inducen tensiones residuales compresivas elevadas. Estas tensiones se ven reducidas durante las etapas subsecuentes de pulverización por bombardeo iónico y deposición de la capa cerámica. Por su parte, las tensiones residuales referidas si son completamente eliminadas en las muestras GTT, aunque sin que el tratamiento posterior al rectificado induzca cambio alguno respecto al daño existente. Éste no es el caso para la fase metálica, donde el tratamiento de recocido conlleva la aparición de una inesperada microporosidad, recristalización microestructural a nivel subsuperficial y la reversión de la transformación de fase inducida durante el rectificado. La operación de rectificado resultó en un incremento significativo de la resistencia a flexión del metal duro. Este efecto positivo se perdió parcialmente al recubrir el material. Por el contrario, la deposición de la capa de TiN promovió un aumento de la resistencia mecánica para la condición GTT. Las variaciones en resistencia a rotura determinadas se explican considerando las tensiones residuales efectivas existentes en cada caso y la ubicación, en la superficie o por debajo de ella, de los defectos críticos responsables de la rotura del material. La carga crítica para la exposición del sustrato en el ensayo de rayado resultó ser Independiente del acabado superficial, para las muestras AS, G y P. Sn embargo, el daño irreversible inducido por el indentador bajo condiciones de contacto y deslizamiento simultáneo fue discreto y localizado para las muestras G, a diferencia de la exposición continua y más pronunciada del sustrato que se evidenció en las condiciones AS y P. Por su parte, las muestras GTT mostraron una carga crítica inferior y cambios relevantes en el mecanismo de fallo correspondiente. El ensayo de indentación Brale de metales duros recubiertos indicó una mayor fragilidad y una menor resistencia a la adhesión para la calidad con menor contenido de ligante metálico. En este marco experimental, y en comparación con el acabado de pulido, se evidenció que el rectificado del sustrato favorece la delaminación, pero también inhibe la aparición de fisuras radiales en metales duros recubiertos. La respuesta observada se analiza y explica sobre las bases de la interacción entre la deformación elasto-plástica impuesta durante la indentación y las alteraciones en integridad superficial resultantes del rectificado. El rectificado del sustrato, previo a la deposición de una capa cerámica, incrementa la resistencia al daño inducido bajo solicitaciones de contacto esférico. Esta influencia positiva se evidencia en términos no solo de la nucleación de fisuras sino también de la subsecuente propagación de ellas dentro del sustrato de metal duro. La principal razón de ello son las elevadas tensiones residuales de compresión introducidas en el proceso de rectificado. Esta afirmación se sustenta por la menor resistencia al daño por contacto que se determinó en las muestras GTT recubierta
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Cattell, Michael James. "The crystallisation and flexural strength optimisation of leucite reinforced glass ceramics for dental applications." Thesis, Queen Mary, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410040.
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Yang, Jing. "Grinding effects on surface integrity, flexural strength and contact damage resistance of coated hardmetals." Doctoral thesis, Linköpings universitet, Nanostrukturerade material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-127341.
Повний текст джерелаАнотація:
The tribological and mechanical behavior of coated tools depends not only on intrinsic properties of the deposited film but also on substrate surface and subsurface properties – such as topography and residual stress state – as well as on interface adhesion strength. It is particularly true in the case of coated tools based on WC-Co cemented carbides (backbone materials of the tool manufacturing industry, and simply referred to as hardmetals in practice) as substrates. Manufacturing of hardmetals often involves grinding, and in the case of cutting tools also edge preparation, etching and coating. The quality of the shaped components is influenced by how the surface integrity evolves through the different process steps. In this regard, substrate grinding and coating deposition represent key steps, as they are critical for defining the final performance and relative tool manufacturing cost. Within this framework, it is the main objective of this thesis to assess the influence of substrate surface integrity on different mechanical (flexural strength and contact damage resistance under spherical indentation) and tribological (scratch resistance as well as cracking and delamination response under Brale indentation) properties for a TiN-coated fine-grained hardmetal grade (WC-13 wt.%Co). In doing so, three different surface finish conditions are studied: as-sintered (AS), ground (G), and mirror-like polished (P). Moreover, aiming for an in-depth analysis of surface integrity evolution from grinding to coating, a relevant part of the work is devoted to document and understand changes induced by grinding in nude hardmetal substrates. The study is also extended to a fourth surface finish variant (GTT), corresponding to a ground substrate which is thermal annealed before being ion etched and coated. Because residual stress induced by grinding are effectively relieved after this high temperature thermal treatment, GTT condition allows to separate grinding-induced effects associated with surface texture and surface/subsurface damage changes (inherited from the G surface finish) from those related to the referred residual stresses. Surface integrity was characterized in terms of roughness, residual stresses (prior and after coating deposition), and damage at the subsurface level. It was found that grinding induces significant alterations in the surface integrity of cemented carbides. Main changes included relevant roughness variations; emergence of a topographic texture; anisotropic distribution of microcracks within a subsurface layer of about 1 micron in depth; severe deformation, microstructure refinement and phase transformation of binder regions, down to 5 microns in depth; and large compressive residual stresses, gradually decreasing from the surface to baseline values at depths of about 10-12 microns. Additional changes in surface integrity are induced during subsequent ion etching and coating deposition. In general, removal of material from the surface during sputter cleaning and extended low-temperature (during film deposition) treatment resulted in a significant residual stresses decrease (about half its original value). However, damage induced by grinding was not completely removed, and some microcracks were still left on the substrate surface (close to the interface). On the other hand, and as expected, high temperature annealing (GTT condition) resulted in a complete relief of the referred residual stresses, but without inducing any additional change in terms of existing microcracks and depth of damaged layer. This was not the case for the metallic binder phase where thermal treatment induced an unexpected microporosity, development of a recrystallized subgrain structure, and reversion of grinding-induced phase transformation. Flexural strength was measured on both uncoated and coated hardmetals, and complemented with extensive fractographic analysis. It was found that grinding significantly enhances the strength of hardmetals, as compared to AS and P conditions. However, such beneficial effect was partly lost in the corresponding coated specimens. On the other hand, film deposition increases strength measured for GTT surface variant. These findings were analyzed on the basis of the changes on nature and location of critical flaws, induced by the effective residual stress field resulting at the surface and subsurface after each manufacturing stage. The influence of substrate surface finish on scratch resistance of coated hardmetals and associated failure mechanisms was investigated. It was found that coated AS, G and P samples exhibit similar critical load for initial substrate exposure and the same brittle adhesive failure mode. However, damage scenario was discerned to be different. Substrate exposure was discrete and localized to the scratch tracks for G samples, while a more pronounced and continuous decohesion was seen for AS and P ones. Relieving of the substrate compressive residual stresses (GTT condition) yielded lower critical loads and changes in the mechanisms for the scratch-related failure, the latter depending on the relative orientation between scratching and grinding directions. The cracking and delamination of TiN-coated hardmetals when subjected to Brale indentation was studied while varying the microstructure and surface finish of the substrate. In this case, another fine-grained WC-Co cemented carbide with lower binder content (6 wt.%Co) was included in the investigation. It was found that polished and coated hardmetals exhibit more brittleness (radial cracking) and lower adhesion strength (coating delamination) with decreasing binder content. Such a response is postulated on the basis of the influence of intrinsic hardness/brittleness of the hardmetal substrate on both cracking at the subsurface level and effective stress state, particularly regarding changes in shear stress component. On the other hand, grinding was discerned to promote delamination, compared to the polished condition, but strongly inhibits radial cracking. This was the result of the interaction between elastic-plastic deformation imposed during indentation and several grinding-induced effects: remnant compressive stress field, pronounced surface texture, and microcracking within a thin microcracked subsurface layer. It is then concluded that coating spallation prevails over radial cracking as the main mechanism for energy dissipation in ground and coated hardmetals. Contact damage resistance of coated hardmetals with different substrate surface finish conditions was investigated by means of spherical indentation under increasing monotonic loads. It was found that grinding enhanced resistance against both crack nucleation at the coating surface and subsequent propagation into the hardmetal substrate. Hence, crack emergence and damage evolution was effectively delayed for the coated G condition, as compared to the reference P one. The observed system response was discussed on the basis of the beneficial effects associated with compressive residual stresses remnant at the subsurface level after grinding, ion-etching and coating. The influence of the stress state was further corroborated by the lower contact damage resistance exhibited by the coated GTT specimens. Finally, differences observed on the interaction between indentation-induced damage and failure mode under flexural testing pointed in the direction that substrate grinding also enhances damage tolerance of the coated system when exposed to contact loads.
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Abdelaal, Maged Mohamed Elsayed. "Effect of post- processing heat treatment on flexural strength of zirconia for dental applications." Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/3031.
Повний текст джерелаАнотація:
Purpose: the purpose of this study was to evaluate the effect of annealing heat treatment on biaxial flexural strength and reliability of 3Y-TZP, sintered at various temperatures.
Materials & methods: 3Y-TZP blanks were pre-sintered at 850°C for 2 hours and sliced into discs (20x1.2mm). Specimens were randomly assigned to 5 groups and subsequently sintered at various temperatures ranging from 1350°C to 1650°C for 2 hours. For each sintering temperature, specimens were divided into three treatment groups. One group (n=20) was left as-sintered as control. One group was air-abraded with 50 micron aluminum oxide powder (n=20). The last group was air-abraded and heat-treated at 1250°C for 20 minutes (n=20). In addition, polished specimens (n=5 per sintering temperature) were prepared to study microstructure, grain size and indentation crack patterns. The mean density was measured by helium pycnometry. The percent porosity was calculated from measured and theoretical density. The mean grain size was determined by the linear intercept method on atomic force micrographs. Crystalline phases were analyzed by x-ray diffraction (XRD). Biaxial flexural strength (BFS) was tested according to ISO standard 6872 using a Universal Testing Machine. Polished specimens were thermally etched, gold coated and Vickers indentations were produced under a 98N load. Indentation crack patterns were analyzed by Scanning Electron Microscopy (SEM) on digital images. The length ratio of trans-granular to inter-granular fracture was determined. Results were analyzed by Kruskal-Wallis test and Turkey's adjustment for multiple comparisons. A 0.05 level of segnificance was used. Reliability was evaluated by weibull analysis.
Results: There was an inverse relationship between density and sintering temperature Spearman rank correlation r = -0.982, p<0.0001). Statistically significant differences were found between all the groups (p<0.0001, exact Kruskal-Wallis test). There was strong evidence of an increase in the percentage of porosity with increasing sintering temperature Spearman rank correlation r=1.00, exact p = 0.017). The mean real grain size increased with sintering temperature. Analysis of XRD data showed that the monoclinic phase as well as ferro-elastic domain switching were present for all air-abraded groups. A small amount of monoclinic phase was also present in groups sintered at 1600°C and 1650°C. In The mean BFS was higher for all air-abraded groups compared to as-sintered or air abraded and heat-treated groups. Air-abraded groups sintered at 1350, 1450, 1550, and 1600°C showed the highest mean BFS (1552.97±200.85, 1502.29±102.36, 1391.4±108.3, 1258.5±114.8 MPa), respectively. The highest Weibull moduli (reliability) were obtained with the heat-treated group sintered at 1550°C (19.8), air-abraded group sintered at 1450°C (17.6) and heat-treated group sintered at 1350°C (15.4). The group sintered at 1650°C was the least reliable, independently of treatment state. Based on the data analysis of both the biaxial flexural strength and Weibull modulus, it was found that, the optimal treatment combination was obtained for the air-abraded group sintered at 1450°C, followed by the air-abraded group sintered at 1550°C. Crack patterns analyses showed that the proportion of trans-granular fracture increased with sintering temperature.
Conclusions: Annealing heat treatment is not recommended after any adjustments, as it does not improve the reliability of the material. Crack patterns and flexural strength are strongly influenced by the crystalline phase composition of the material. Sintering at 1600°C and 1650°C is not recommended due to the corresponding decrease in mechanical properties independently of treatment. Air-abrasion of zirconia sintered at 1450°C or 1550°C led to the best combination of high strength and reliability.
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Carlin, Brian Patrick. "Investigation of the Strength and Ductility of Reinforced Concrete Beams Strengthed with CFRP Laminates." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36546.
Повний текст джерелаАнотація:
The use of fiber reinforced plastics (FRP) in repairing and strengthening bridges has been researched in recent years. In particular, attaching unidirectional FRP to the tension face of reinforced concrete beams has provided an increase in stiffness and load capacity of the structure. However, due to the brittle nature of the unidirectional FRP, the ductility of the beam decreases. One possible solution to this problem is the use of cross-ply or off-axis FRP laminates. This thesis focuses on the investigation of the flexural behavior of reinforced concrete beams strengthened with one of two different FRP orientations (0°/90° and ±45°). More particularly, the change in strength and ductility of the beams as the number of FRP layers are altered is investigated. Seven under-reinforced concrete beams were constructed and tested to failure. With the exception of the control beam, each specimen was applied with two, three, or four layers of either 0°/90° and ±45° FRP orientations. To predict the flexural behavior of the specimens, a theoretical model was derived using basic concepts, past research, and the tested properties of the concrete, steel reinforcement, and FRP. Also, two methods were used to analyze the ductility of the tested beams. Along with the test details of each specimen; the moment, deflection, CFRP strain, crack patterns, and mode of failure are discussed. The results included an increase in load capacity with respect for the number of CFRP layers applied for both orientations. Also, the ductility of the beams were reduced by adding CFRP orientations.Master of Science
33
Nassar, Adil J. "Investigation of Transfer Length, Development Length, Flexural Strength and Prestress Loss Trend in Fully Bonded High Strength Lightweight Prestressed Girders." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32941.
Повний текст джерелаАнотація:
Encouraged by the performance of high performance normal weight composite girders, Virginia Department of Transportation has sought to exploit the use of high strength lightweight composite concrete (HSLWC) girders to achieve economies brought about by the reduction of dead loads in bridges. Transfer Length measurements conducted on two AASHTO Type IV HSLWC prestressed girders, resulted in an average transfer length of 17 inches, well below the AASHTO and ACI guidance.
Two girders composed of HSLWC AASHTO Type II girders and a 48" x 8" normal weight 4000-psi concrete deck were produced. The HSLWC Type II girders were cast of concretes with a compressive strength of 6380 psi and unit weight of 114 pcf. Full scale testing of the girders was conducted to evaluate development length and flexural strength in HSLWC composite girders. Embedment lengths of five, six and eight feet were evaluated. Tests indicated a development length of about 72 inches, marginally below the ACI and AASHTO stipulation. Four of eight strands in the girders showed general bond failure nevertheless, the tested girders exceeded their theoretical flexural capacity by 24 to 30 percent.
A third composite girder was cast of a high strength normal weight concrete (HSNWC) Type II girder, and topped with a 48" x 8" normal weight 4000-psi concrete deck. This girder was intended as a control specimen to contrast its test results with the HSLWC composite girders. The targeted compressive strength of both the HSLWC and HSNWC AASHTO beams was 8000 psi. The compressive strength of the HSNWC mixture, however, was about 8990 psi compared to 6380 psi for the HSLWC mixture.
Prestress losses in HSLWC AASHTO Type IV girders monitored over a nine-month period were found to be less than those calculated using the ACI and PCI models. Furthermore, the ACI model indicated that the effective prestressess retained in the HSLWC girders in 30 year's time are greater than 50% of the specified tensile strength of the strands.Master of Science
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Malik, Aneeqa. "Flexural strength, fracture toughness, and denture tooth adhesion of computer aided milled andprinted denture bases." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563296646075298.
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Ribeiro, Daniela Garcia. "Efeito da irradiação por microondas sobre a resistência à flexão e dureza de resinas acrílicas para reembasamento imediato /." Araraquara : [s.n.], 2004. http://hdl.handle.net/11449/97304.
Повний текст джерелаАнотація:
Orientador: Ana Cláudia PavarinaBanca: Eunice Teresinha Giampaolo
Banca: Ricardo Faria Ribeiro
Resumo: O uso do microondas tem sido indicado como um método efetivo na desinfecção de resinas acrílicas. Entretanto, há pouca informação sobre o efeito da irradiação do microondas nas propriedades mecânicas desses materiais. Considerando esses aspectos, o objetivo deste estudo foi avaliar o efeito da irradiação por microondas sobre as propriedades mecânicas de resistência à flexão e dureza de resinas acrílicas. Os corpos-de-prova para a realização dos testes mecânicos foram confeccionados com os seguintes materiais: Kooliner (K), Tokuso Rebase Fast (TR), Ufi Gel Hard C (UGH) e New Truliner (NT), todas resinas indicadas para reembasamento imediato, e Lucitone 550 (L), que é uma resina para base de prótese. Para cada material foram confeccionados 48 corpos-de-prova que foram divididos igualmente em seis grupos. As resinas autopolimerizáveis (K, TR, UGH e NT) foram submetidas à irradiação logo após a confecção, enquanto que os corpos-de-prova da resina termopolimerizável (L) permaneciam 50 l 2 horas em água a 37ºC l 1ºC antes da irradiação. Para o procedimento de irradiação, cada corpo-de-prova foi individualmente imerso em 200 mL de água destilada e submetido a dois ciclos de irradiação pelas microondas, para simular o envio da prótese ao laboratório e o retorno dela ao consultório odontológico. Cada corpo-de-prova foi irradiado a uma potência constante de 650 W, variando-se o tempo de exposição: 1 minuto (T1), 2 minutos (T2), 3 minutos (T3), 4 minutos (T4) ou 5 minutos (T5). O grupo controle (T0) foi submetido aos testes mecânicos sem ser irradiado pelas microondas. Os ensaios de resistência à flexão para todos os corpos-de-prova foram realizados em máquina MTS-810 Material Test System sob velocidade de 5 mm/minuto, utilizando o teste em três pontos a uma distância de 50 mm entre os apoios. Em seguida, um dos fragmentos do ...(Resumo completo, clicar acesso eletônico abaixo)
Abstract: Microwave irradiation was previous suggested as an effective method for the disinfection of acrylic resins. However, little information is available concerning the effect of microwave irradiation on the mechanical properties of acrylic resins. The purpose of this study was to evaluate the effect of two cycles of a microwave disinfection procedure on the flexural strength and Vickers hardness of acrylic resins. Four autopolymerized resins (Kooliner- K, Tokuso Rebase Fast- TR, Ufi Gel Hard- UGH and New Truliner- NT) and one heat-cured resin (Lucitone 550- L) were used for preparing specimens. For each material, 48 specimens were made and equally divided into six groups. The relined specimens were submitted to disinfection procedures after polymerization and the denture base polymer specimens were stored in water for 50 l 2 hours at 37ºC l 1ºC prior to disinfection. The specimens were individually immersed in 200 mL of destilated water and microwaved twice, simulating when dentures come from the patient and before being returned to the patient. Each cycle of microwave disinfection was performed at 650 W for one of the following irradiation times: 1 minute (T1), 2 minutes (T2), 3 minutes (T3), 4 minutes (T4) or 5 minutes (T5). Control group (T0) specimens were subjected to mechanical tests without being disinfected. The flexural strength values of the materials were determined using a testing machine MTS-810 at a crosshead speed of 5 mm/minute using a three-point bending fixture with a span of 50 mm. Thereafter, one fragment of specimen was submitted to Vickers microhardness test. The values were determined by using a 25 gf load, after 30 seconds contact. Twelve hardness measurements were taken on each specimen and the average was then calculated. The flexural and hardness values were submitted to ANOVA and ...(Complete abstract, click electronic access below)
Mestre
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Majumdar, Nandita N. "Development of Low Expansion Glaze Coatings on As Fired Si₃N₄ to Enhance Room Temperature Flexural Strength." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36798.
Повний текст джерелаАнотація:
Silicon nitride (Si3N4) has the potential for use in various high-performance applications.
However, surface defects such as voids/pits are commonly present on as processed Si3N4. When
subjected to external forces, fracture originates at such flaws. To reduce or eliminate surface
flaws, machining operations are required which constitute a major proportion of production costs.
In order to offer an inexpensive alternative to machining and also to enhance the room
temperature flexural strength of as fired Si3N4, low expansion glaze coatings of lithium
aluminosilicate (LAS) and magnesium aluminosilicate (MAS) compositions were developed.
Homogeneous and crack-free glaze coatings were successfully formed on as processed Si3N4.
This ensured formation of compressive surface stresses on the as fired Si3N4 which, in turn, led to
the reduction of the effects of surface flaws. When compared to the uncoated as fired Si3N4, both
the glaze coatings helped achieve greater flexural strength. Analyses of the two glazes indicated
better strength for the MAS coating compared to the LAS. Wear tests revealed that the MAS
glaze exhibited higher wear resistance than the LAS glaze. These differences were attributed to
the ability of the magnesium aluminosilicate glaze to achieve greater surface smoothness and
better adherence to the substrate than the lithium aluminosilicate.Master of Science
37
Esposito, Alessandro. "Creep deflection of low-strength reinforced concrete flexural members strengthened with carbon fiber composite sheets." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10340/.
Повний текст джерелаАнотація:
The low-strength concrete is defined as a concrete where the compressive cubic strength is less than 15 MPa. Since the beginning of the last century, many low-strength concrete buildings and bridges have been built all over the world. Being short of deeper study, composite sheets are prohibited in strengthening of low-strength reinforced concrete members (CECS 146; ACI 440). Moreover, there are few relevant information about the long-term behavior and durability of strengthened RC members.
This fact undoubtedly limits the use of the composite materials in the strengthening applications, therefore, it is necessary to study the behaviours of low-strength concrete elements strengthened with composite materials (FRP) for the preservation of historic constructions and innovation in the strengthening technology.
Deformability is one of criteria in the design of concrete structures, and this for functionality, durability and aesthetics reasons. Civil engineer possibly encounters more deflection problems in the structural design than any other type of problem. Many materials common in structural engineering such as wood, concrete and composite materials, suffer creep; if the creep phenomenon is taken into account, checks for serviceability limit state criteria can become onerous, because the creep deformation in these materials is in the same order of magnitude as the elastic deformation.
The thesis presents the results of an experimental study on the long-term behavior of low-strength reinforced concrete beams strengthened with carbon fiber composite sheets (CFRP). The work has investigated the accuracy of the long-term deflection predictions made by some analytical procedures existing in literature, as well as by the most widely used design codes (Eurocode 2, ACI-318, ACI-435).
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Collins, Travis Collins. "Estimating in-situ flexural strength of heat-affected prestressed concrete beams using constituent material models." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219953974/.
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Yu, Zhou. "Flexural strength of lithospere in central Asia and development of intracontinental orogens : the Tien Shan." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10718.
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Rosensvärd, Markus, and David Danneker. "Flexural strength of zirconia after grinding, using diamond burrs, silicon carbide burr and water-cooling." Thesis, Malmö universitet, Odontologiska fakulteten (OD), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-19863.
Повний текст джерелаАнотація:
SyfteSyftet med föreliggande studie är att undersöka om slipning av zirkonia med silikatkarbid, diamant, vattenkylning, höghastighetsturbin och låghastighetshandstycke påverkar böjhållfastheten hos zirkonia.Material och metodFemtio provkroppar av yttriumoxidstabiliserad tetragonal zirkonia framställdes med CAD/CAM. Provkropparna delades in i 5 grupper med 10 i varje; polerad med låghastighetshandstycke (P), vattenkylning med finkornig diamantfräs (HDW), höghastighetsturbinshandstycke utan vattenkylning med finkornig diamantfräs (HDD), låghastighetshandstycke med finkornig diamantfräs (LD) och låghastighetshandstycke med kiselkarbidfräs (LC). Efter slipningen polerades alla provkropparna med låghastighetshandstycke och polertrissa. Artificiell åldring genomfördes med cyklisk dynamisk förbelastning och termocykling. Provkropparna testades med ett biaxialt böjhållfasthetstest i en universaltestmaskin. Resultaten analyserades med hjälp av en One-way ANOVA, Tukey’s test. Signifikansnivån sattes till α = 0,05.ResultatResultatet visade ingen signifikant skillnad mellan de olika grupperna. MPa medelvärde för varje grupp och standardavvikelser; P 1061(±82), HDW 1023(±92), HDD 1002(±127), LD 812(±228) and LS 984(±83).SlutsatsInom begränsningarna för föreliggande studie kan slutsatsen dras att böjhållfastheten hos zirkonia inte signifikant påverkas efter användning av följande slipningsprocesser:Höghastighetstubin med fin diamant och vattenkylning eller med höghastighetsturbin med fin diamant och utan vattenkylning eller med låghastighetshandstycke med fin diamant eller kiselkarbidfräs när zirkoniaytan är polerad.AimThe purpose of this study is to investigate whether grinding zirconia with silicon carbide, diamond, water cooling, high speed turbine and low speed handpiece affects the flexural strength of zirconia.Material and methodFifty specimens of yttrium oxide stabilized tetragonal zirconia were produced using CAD/CAM. The specimens were divided into 5 groups with 10 in each; polished with low speed handpiece (P), high speed turbine with water cooling using a fine diamond burr (HW), high speed turbine without cooling using a fine diamond burr (H), low speed handpiece with a fine diamond burr (LD) and low speed handpiece with silicon carbide burr (LC). After grinding all specimens were polished with a slow speed handpiece and a polishing wheel. Artificial aging was performed using cyclic dynamic loading and thermocycling. The specimens were then tested in a biaxial flexural strength test using a universal testing machine. The results were analysed using One-way ANOVA, Tukey’s test. Level of significance was set at α = 0.05.ResultsThe results showed no significant differences between the groups. MPa means for each group and SD; P 1061(±82), HDW 1023(±92), HDD 1002(±127), LD 812(±228) and LS 984(±83).ConclusionWithin the limitations of this study it can be concluded that flexural strength of zirconia is not significantly affected using the following grinding processes: High-speed turbine with fine diamond and water cooling or with fine diamond without water cooling, low-speed handpiece with fine diamond or with silicon carbide burr when the zirconia has been polished.
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Alazemi, Athbi. "Investigate the Effects of Nano Aluminum Oxide on Compressive, Flexural Strength, and Porosity of Concrete." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1544693885397299.
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Cheng, Ming. "Experimental investigation of the biaxial flexural strength of 8YSZ thin film ceramic substrates as electrolytes." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/279958.
Повний текст джерелаАнотація:
Thin ceramic substrates are widely used in engineering applications in modern industry. For example, they are used as molecular filters in fuel cells and solid oxide electrolyzers for oxygen generation. Development of high-reliability substrate materials inevitably requires the accurate characterization of their mechanical properties. The loading conditions in service on the ceramic substrates, such as the solid oxide electrolytes with a thickness of much less than 2 mm, often involve multiaxial bending instead of simple tension or bending. In this dissertation, the ASTM standard piston-on-3-ball experimental technique at ambient temperature is employed to investigate the quasi-static biaxial flexural strength of pure 8YSZ and Al₂O₃ or 3YSZ doped 8YSZ ceramic substrates. Furthermore, this piston-on-3-ball experimental technique is developed into a dynamic piston-on-3-ball technique at ambient temperature and a quasi-static piston-on-3-ball technique at elevated temperatures. Stress distribution functions in the tensile surface of a specimen under piston-on-3-ball loading condition are formulated and used to develop statistical models, which are proven to be in the form of a Weibull distribution function, to describe the biaxial flexural strength behavior of ceramic substrates under piston-on-3-ball loading condition. Analytical modeling was conducted on the dynamic piston-on-3-ball loading configuration. This analytical model can be used to guide the experimental design and judge the validity of experimental results. A new material constitutive model is developed to give a good description of the dynamic strength behavior of ceramic materials under constant stress-rate loading. Quasi-static experiments under piston-on-3-ball loading are conducted at both ambient temperature and elevated temperatures, while dynamic experiments are conducted at ambient temperature. Experimental results, as well as observations from SEM microstructure images and values of fracture toughness measured using a newly developed Vickers micro-indentation toughness technique, lead to a conclusion that no obvious overall improvement to the SYSZ ceramic substrates in the biaxial flexural strength can be observed by adding Al₂O₃ additive with amount up to 3 mol% or 3YSZ additive with amount up to 30 wt%.
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GUPTA, KARTIC. "EFFECT OF AIR COOLED BLAST FURNANCE SLAG AND METAKAOLIN ON COMPRESSIVE AND FLEXURAL STRENGHTH OF CONCRETE CONTAINING FLY ASH." Thesis, 2018. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16364.
Повний текст джерелаАнотація:
Concrete is the most commonly used construction material in the world. Concrete is extensively used in infrastructure projects. The concrete obtained by mixing cement, water and an inert matrix of sand and gravelundergoes a number of operations such as transportation, placing, compacting, finishing and curing.
Pozzolanic materials including flyash, metakaolin, slag, Rice Husk Ash and silica fume have been used in recent years as cement replacement material for developing HSC with improved workability, strength and durability with reduced permeability. Metakaolin, which is a relatively new material in the concrete industry is effective in increasing strength, reducing sulphate attack and improving air-void network. Pozzolanic reactions improve the microstructure of concrete and chemistry of hydration products by consuming the released calcium hydroxide (CH) and production of additional calcium silicate hydrate (C-S-H), resulting in an increased strength and reduced porosity and therefore improved durability.
Use of Metakaolin in construction industry as partial replacement of cement started in the 1960’s and the interest in this material has considerably increased in recent years. Metakaolin has pozzolanic properties bringing positive effects on resulting properties concrete. Pozzolanic properties cause chemical reaction of active components with calcium hydroxide (portlandite), which is formed as a product of cement hydration. This reaction leads to formation of binding phases of following types: secondary C-S-H gel, C4AH13, C3AH6, and C2ASH8 thereby increasing strength.
The Air cooled blast furnance slag (ACBFS) has also been used as partial replacement of coarse aggregates in the recent past . In the previous studies it has been confirmed that the concrete made with natural aggregates and with ACBFS has comparable compressive.
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Wu, Zhenhua. "Behavior of high-strength concrete members under pure flexure and axial-flexural loading." 2006. http://www.lib.ncsu.edu/theses/available/etd-12122006-101746/unrestricted/etd.pdf.
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45
Alhayek, Hanan. "Flexural stiffness and strength of reinforced timber beams." 2009. http://hdl.handle.net/1993/21384.
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46
Lin, Nan-Shian, and 林南賢. "The Flexural Behavior of High-Strength Concrete Beams Using High-Strength Steels." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/84906442104978502572.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
營建工程系
96
This study is to investigate the flexural behavior of high-strength concrete beams using high-strength steels. Sixteen specimens were tested to study the effects on flexural behavior of concrete strength (f'c), yielding strength of steels (fy), reinforcement radio (ρ) and section size (b*h). For high-strength concrete beams using high-strength steels, this study predicts the ultimate flexural strength and the midspan deflection of beams using the recommendations proposed by ACI Code [2], Leslie [3] and Carrasquillo [4]. This study also predicts the flexural crack width of beams using the recommendations proposed by Gergely and Lutz [6]. Test results indicate that the recommendations proposed by ACI Code [2] and Leslie [3] are conservative for predicting the ultimate flexural strength of beams. But the recommendations proposed by Leslie [3] are more conservative for predicting the ultimate flexural strength of beams. At service loads, the recommendations proposed by ACI Code [2] and Carrasquillo [4] can reasonably predict the midspan deflection of beams. This study also indicates that the crack width calculated using the recommendations proposed by Gergely and Lutz [6] will overestimate the flexural crack width of beams.
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Lai, Hong-Jin, and 賴弘晉. "Out-of-Plane Flexural Bond Strength of Brick Walls." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/51037676972555206523.
Повний текст джерелаАнотація:
碩士國立中興大學
土木工程學系所
102
The purpose of this research is to investigate the out-of-plane flexural bond strength of brick walls. Two-hundred and twenty specimens were made in this study. The variables included type of brick, finess modulus of sand, water content of brick, water-cement ratio(W/C) of mortar, and relative humidity of curing. The following results were observed. 1. Brick type will affect the bond strength, but not as apparent as other variables. 2. Bond strength of brick walls with coarse sand (FM = 2.67) was higher than that with fine sand (FM = 1.99), the increase was about 50%. 3. The bricks better be water-saturated when laying, otherwise, the bond strength would be reduced by about 90%. 4. The water-cement ratio of mortar affects the bond strength. Bond strength with W/C of 0.7 was lower than that with W/C of 0.5 by approximately 68%. Addition of methyl cellulose in the mortar increases the bond strength. For W/C of 0.7, the increase could be 613%, while for W/C of 0.5, the increases was 160%. 5. Higher curing humidity will lead to higher bond strength, the increase could be up to 90%.
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Yakel, Aaron Jon. "Flexural strength and ductility of high performance steel girders." 2009. http://proquest.umi.com/pqdweb?did=1702663591&sid=5&Fmt=2&clientId=14215&RQT=309&VName=PQD.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009.Title from title screen (site viewed July 21, 2009). PDF text: xv, 386 p. : ill. (some col.) ; 10 Mb. UMI publication number: AAT 3352204. Includes bibliographical references. Also available in microfilm and microfiche formats.
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Jiang, Wei-shin, and 江偉新. "Hydraulic Flexual Strength Testing for Brittle Materials." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/15525574338471335996.
Повний текст джерелаАнотація:
碩士國立海洋大學
機械與輪機工程學系
86
In this study , a hydraulic flexural test device is developed for measur-ing the biaxial flexural strength of brittle materials . Both sides of thecircular specimen are subjected to hydraulic with equal , opposite resultantforces . The effect of the stress concentration and frictinal resistant existingalong the supports can be alleviated . The close form solutions for the structural responses based on the thin platetheory are obtained . The elasticity solutions and the solutions based on theshear deformation theory obtained using the ANSYS finite element code are alsopresented for assessing the validity of the thin plate solutions . The effects of dimension errors due to manufacture and the misalignment of the specimen on the structural responses are thoroughly examined . First , steel circular plates with strain gages attached at the plate centerare tested in the elastic region . The experimental results show that the hydraulic device is adequate to produce accurate results . Also , the results correspondingto several repeated tests are in good agreement . Finally , the fracture strength ofglass plates in tested . The Weibull distribution function is employed to analyze the test data .
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Adcook, Richard S. (Richard Scott) 1973. "Flexural strength and shear bond strength of self-etching/self-adhesive resin luting agents." Thesis, 2009. http://hdl.handle.net/1805/2083.
Повний текст джерелаАнотація:
Indiana University-Purdue University Indianapolis (IUPUI)Traditional resin luting agents generally have mechanical properties that are superior to the newer so-called “universal” self-etching/self-adhesive resin luting agents. However, recent reports indicate that some properties of these new luting agents have been improved, approaching those of the traditional etch and rinse resin luting agents. The objective of this study was to test some mechanical properties of four of these self-etching/self-adhesive resin luting agents [Maxcem Elite (ME), Multilink Automix (MA), RelyX Unicem (RU), SmartCem 2 (SC)] and compare them to a traditional etch and rinse resin luting agent [RelyX ARC (RA)] and a resin-modified glass ionomer luting cement [Fuji Plus (FP)], both of which have much longer histories of clinical success. By comparing the properties of the newer cements to the standards, it may be possible to determine how clinically successful the newer cements may be. The mechanical properties tested were flexural strength (FS) and shear bond strength (SBS). The FS test included making beams of each material, storing them in water for periods of time (24 hours and 90 days) and then performing a three-point bending test on a universal testing machine. The 90 day groups were thermocycled. The SBS test involved preparing human molar specimens, making flat dentin surfaces. Composite cylinders were fabricated, luted to the dentin surfaces with each of the materials tested, stored in water for periods of time (24 hours or 90 days), and then a knife edge shear test was performed on a universal testing machine. The 90 day groups were thermocycled. A Weibull-distribution survival analysis was performed. The results revealed significant differences in the FS of all materials tested at 24 hours. After 90 days and thermocycling, only SC and RA were not significantly different. At both time periods, FP had the lowest and MA the highest FS. The SBS results showed MA, RA, and RU to have the highest bond strengths; SC and ME the lowest at 24 hours. After 90 days and thermocycling, RA had significantly higher bond strength than all other groups; ME, FP and SC had the lowest. The self-etching/self-adhesive resin luting agents all performed at least as well as FP, with the exception of SC (SBS 24 hour). They did not all perform as well as RA, with the exception of SC (FS 90 day), MA (SBS 24 hour, FS 24 hour and 90 day), and RU (SBS 24 hour). The newer luting agents should expect to have clinical success, regarding flexural strength and shear bond strength, at least as good as resin-modified glass ionomer luting cements and approach the level of traditional etch and rinse resin luting agents.