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Title: Development of a multiple specimen test methodology for fatigue crack growth rate determination.
Creator: Deshayes, Frederic Rene., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A new experimental approach has been developed whereby fatigue crack growth rates are determined for multiple specimens tested in series. This involves a geometry whereby specimens respond to cyclic loading in a manner that is mutually independent. The classic compact-tension specimen geometry is inappropriate for this technique, since stress intensity factor range increases with increasing crack length (constant load amplitude or range); and this dictates load shedding according to the...
Show moreA new experimental approach has been developed whereby fatigue crack growth rates are determined for multiple specimens tested in series. This involves a geometry whereby specimens respond to cyclic loading in a manner that is mutually independent. The classic compact-tension specimen geometry is inappropriate for this technique, since stress intensity factor range increases with increasing crack length (constant load amplitude or range); and this dictates load shedding according to the specimen for which crack propagation is most rapid. Stress intensity factor range for the remaining specimens (smaller crack length) consequently decreases to low values and may even fall to below Delta KI, such that little or no information is obtained from them. To overcome this difficulty a new constant taper, side-grooved compact-tension specimen geometry for which stress intensity factor decreases with increasing crack length at constant load has been developed. Load shedding is, therefore, not necessarily required to reduce Delta KI during the test. A finite element analysis was performed to establish the stress intensity-crack length (constant load), compliance-crack length and DCPD (Direct Current Potential Drop)-crack length character of the specimen. An appropriate side-groove depth to avoid crack deviation from the intended plane was determined experimentally, and an analytical expression to account for reduced thickness in the crack plane was verified. Calibration curves between crack length and compliance and between crack length and potential drop were verified as well, and the stress intensity-crack length characteristics for the specimen were confirmed by comparison of da/dN-Delta KI curves with those for conventional C(T) specimens. A locally fabricated, five specimen fatigue testing frame was developed in conjunction with a 98 kN MTS actuator and interfaced with a commercially available control system, the hardware and software of which were modified to accommodate multiple specimen control and data acquisition. The utility of the proposed specimen and test procedure are discussed within the context of threshold and near-threshold crack growth rate determination where long test times are normally required for data development, particularly for low cyclic frequency applications such as nuclear and offshore.
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Date Issued: 1991
PURL: http://purl.flvc.org/fcla/dt/12272
Subject Headings: Materials--Fatigue
Format: Document (PDF)

Title: Discrete signal representation using triangular basis functions.
Creator: Nallur, Padmanabha., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis deals with the representation of discrete signals using triangular basis functions. Signals are usually represented by Fourier series expansions where the basis functions are cosine and sine functions which are all mutually orthogonal. The triangular basis functions used here are called TRIC (triangular cosine) and TRIS (triangular sine) functions. The TRIC and TRIS functions are like their cosine and sine function counterparts except that they are linear. The TRIC and TRIS...
Show moreThis thesis deals with the representation of discrete signals using triangular basis functions. Signals are usually represented by Fourier series expansions where the basis functions are cosine and sine functions which are all mutually orthogonal. The triangular basis functions used here are called TRIC (triangular cosine) and TRIS (triangular sine) functions. The TRIC and TRIS functions are like their cosine and sine function counterparts except that they are linear. The TRIC and TRIS functions are not all mutually orthogonal, though most of them are. A matrix method of representing discrete signals using TRIC and TRIS functions is presented. A discrete triangular transform matrix is developed and a method of deriving this matrix is presented. A Fortran program is written to derive the discrete triangular transform matrix and to prove the reconstruction of several basic functions like impulse, step, pulse and sinusoidal waveforms.
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Date Issued: 1988
PURL: http://purl.flvc.org/fcla/dt/14451
Subject Headings: Signal processing--Mathematical models
Format: Document (PDF)

Title: EFFECT OF CATHODIC POLARIZATION AND SEA WATER VELOCITY UPON CALCAREOUS DEPOSIT FORMATION ON MILD STEEL.
Creator: WOLFSON, STEPHEN LANCE., Florida Atlantic University, Hartt, William H.
Abstract/Description: To investigate environmental conditions which influence the type and formation of calcareous deposits, AISI 1010 steel specimens were exposed in sea water at constant velocities and controlled potentials. Chemistry and thickness of the deposits which formed as a result of cathodic polarization of steel in sea water were determined. These variables were found to be a function of velocity and controlled potential with film thickness decreasing as velocity increased for all potentials considered...
Show moreTo investigate environmental conditions which influence the type and formation of calcareous deposits, AISI 1010 steel specimens were exposed in sea water at constant velocities and controlled potentials. Chemistry and thickness of the deposits which formed as a result of cathodic polarization of steel in sea water were determined. These variables were found to be a function of velocity and controlled potential with film thickness decreasing as velocity increased for all potentials considered. This behavior is interpreted in terms of variations in pH at the metal surface. A mass transfer analysis is presented which projects the pH at the metal surface as a function of velocity and controlled potential. Scanning electron micrographs are also included to give information regarding the nature and type of deposits. The experimental results are discussed within the frame of accepted concepts of sea water cathodic protection.
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Date Issued: 1978
PURL: http://purl.flvc.org/fcla/dt/13954
Subject Headings: Cathodic protection
Format: Document (PDF)

Title: Effect of cathodic protection and cyclic frequency on corrosion fatigue of selected high strength steels in seawater.
Creator: Badve, Ashwin P., Florida Atlantic University, Hartt, William H.
Abstract/Description: Study of selected candidate steels for offshore application was undertaken to observe the effects of cathodic protection and cyclic frequency on corrosion fatigue life. Keyhole Compact Tension Fatigue experiments under constant amplitude sinusoidal loading and stress ratio of 0.5 were performed on 25.4 mm thick specimens in natural sea water and also in air upon three different steels (Y.S. 500-563 MPa). These steels represented different strengthening techniques, namely precipitation...
Show moreStudy of selected candidate steels for offshore application was undertaken to observe the effects of cathodic protection and cyclic frequency on corrosion fatigue life. Keyhole Compact Tension Fatigue experiments under constant amplitude sinusoidal loading and stress ratio of 0.5 were performed on 25.4 mm thick specimens in natural sea water and also in air upon three different steels (Y.S. 500-563 MPa). These steels represented different strengthening techniques, namely precipitation hardening, direct quenching--a thermomechanical control process (TMCP), and controlled rolling. Cathodic polarization was in the range between freely corroding and -1.10 Volts (SCE). The tests were performed at a frequency of 0.3 and 1.0 Hz. The results are presented in the S-N and potential versus cycles to initiation format. No effect of frequency (1.0-0.3 Hz) was observed at cathodic protection of -1.10 V (SCE). The steels showed an increase in fatigue life to an optimum potential, and excessive potentials were detrimental. The fatigue life in dry air was greater than in laboratory air (~50% RH).
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/14494
Subject Headings: Marine steel--Fatigue, Offshore structures, Sea-water corrosion, Corrosion and anti-corrosives
Format: Document (PDF)

Title: Effect of cathodic protection on bond strength between prestressing steel and concrete.
Creator: Ducrocq, Luc., Florida Atlantic University, Hartt, William H.
Abstract/Description: A series of experiments was performed on prestressed concrete specimens for the purpose of studying the tendency of disbonding between the embedded steel and the concrete due to an impressed cathodic current. The procedure first involved impressing an anodic current until active potentials were recorded along the tendon length. Subsequently, cathodic polarization of the prestressed tendons was affected using a current density of 1 mA/cm^2. The strain variation of the concrete specimens was...
Show moreA series of experiments was performed on prestressed concrete specimens for the purpose of studying the tendency of disbonding between the embedded steel and the concrete due to an impressed cathodic current. The procedure first involved impressing an anodic current until active potentials were recorded along the tendon length. Subsequently, cathodic polarization of the prestressed tendons was affected using a current density of 1 mA/cm^2. The strain variation of the concrete specimens was monitored during these two procedures using gages placed on the top or bottom surface. It was found that for a current density of 1 mA/cm^2 during the 30 day monitoring period the concrete relaxed by an amount equivalent to an 80 percent loss of bond between the tendons and concrete. The implications of this with regard to cathodic protection of prestressed concrete structures and components in actual service are discussed.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14591
Subject Headings: Prestressed steel construction, Prestressed concrete construction, Cathodic protection
Format: Document (PDF)

Title: Effect of Polarization on Steel Embedded in Simulated Piling Specimens Evaluated by Critical Chloride Threshold.
Creator: Tanner, Russell, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Critical chloride threshold, CT values for initiation of reinforced steel corrosion m mortar typical of Florida coastal bridge substructures were determined in laboratory tests. Previous research has reported CT values that vary by more than an order-of-magnitude, making design life estimation for structures difficult. On this basis, experiments on piling type specimens focused on [Cl-] contamination in the splash zone and coupling of this steel to a large surface area submerged anode. The...
Show moreCritical chloride threshold, CT values for initiation of reinforced steel corrosion m mortar typical of Florida coastal bridge substructures were determined in laboratory tests. Previous research has reported CT values that vary by more than an order-of-magnitude, making design life estimation for structures difficult. On this basis, experiments on piling type specimens focused on [Cl-] contamination in the splash zone and coupling of this steel to a large surface area submerged anode. The lower portion of simulated piling was immersed and the region above the waterline periodically sprayed with NaCI solution. Corrosion potential with respect to height above the waterline was monitored. A temporary depolarization method for determining as to whether or not corrosion had initiated is proposed. Chloride distribution at the reinforcement-concrete interface was determined in piling using energy dispersive x-ray analysis and related to height with respect to the waterline. Chloride threshold was related to corrosion potential.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012560
Subject Headings: Reinforced concrete construction, Steel, Structural--Corrosion, Chlorides, Corrosion and anti-corrosives, Seawater corrosion
Format: Document (PDF)

Title: Effect of steel reinforcement type and surface condition on corrosion initiation in mortar.
Creator: Huang, Yirong., Florida Atlantic University, Hartt, William H.
Abstract/Description: This study employed half-cell potential (Eoc), polarization resistance (PR) and galvanic current tests to explore effects of surface condition and steel reinforcement type on corrosion initiation in mortar. A low impurity steel plate and #10 grade 60 rebar were used. Four surface conditions (as-received, atmospherically rusted, #240 SiC paper polished, and #500 SiC paper polished) were employed. Cyclic wet and dry exposure of specimens in 15% NaCl solution was conducted. Half-cell potential...
Show moreThis study employed half-cell potential (Eoc), polarization resistance (PR) and galvanic current tests to explore effects of surface condition and steel reinforcement type on corrosion initiation in mortar. A low impurity steel plate and #10 grade 60 rebar were used. Four surface conditions (as-received, atmospherically rusted, #240 SiC paper polished, and #500 SiC paper polished) were employed. Cyclic wet and dry exposure of specimens in 15% NaCl solution was conducted. Half-cell potential measurements showed that the corrosion probability of specimens with as-received and pre-rusted surfaces was lower than that of specimens with a polished surface. However, the PR and galvanic current tests indicated higher corrosion rate for specimens prepared with atmospherically rusted and as-received steels. Good agreement was found between results of the polarization resistance test and galvanic current measurements. There is a lack of correlation between half-cell potential and corrosion rate.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13075
Subject Headings: Corrosion and anti-corrosives--Testing, Reinforced concrete--Corrosion, Mortar, Steel--Corrosion
Format: Document (PDF)

Title: Effects of cement alkalinity, exposure conditions and steel-concrete interface on the time-to-corrosion and chloride threshold for reinforcing steel in concrete.
Creator: Nam, Jingak., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH...
Show moreEffects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH measurement of concrete pore water. Once specimens were fabricated and exposed to a corrosive chloride solution, various experimental techniques were employed to determine time-to-corrosion, chloride threshold, diffusion coefficient and void density along the rebar trace as well as pore water pH. Based upon the resultant data, several findings related to the above parameters have been obtained as summarized below. First, time for the corrosion initiation was longest for G109 concrete specimens with high alkalinity cement (HA). Also, chloride threshold increased with increasing time-to-corrosion and cement alkalinity. Consequently, the HA specimens exhibited the highest chloride threshold compared to low and normal alkalinity ones. Second, high temperature and temperature variations reduced time-to-corrosion of reinforcing steel in concrete since chloride diffusion was accelerated at higher temperature and possibly by temperature variations. The lowest chloride threshold values were found for outdoor exposed specimens suggesting that variation of RH or temperature (or both) facilitated rapid chloride diffusion. Third, an elevated time-to-corrosion and chloride threshold values were found for the wire brushed steel specimens compared to as-received ones. The higher ratio of [OH-]/[Fe n+] on the wire brushed steel surface compared to that of as-received case can be the possible cause because the higher ratio of this parameter enables the formation of a more protective passive film on the rebar. Fourth, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized corrosion. This tendency for corrosion initiation increased in proportion to void size irrespective of specimen type. Also, [Cl -]th decreased with increasing void diameter. In addition, new ex-situ leaching method for determining concrete pore water alkalinity was developed.
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Date Issued: 2004
PURL: http://purl.flvc.org/fcla/dt/12096
Subject Headings: Reinforced concrete construction, Chlorides, Steel--Corrosion, Composite reinforced concrete
Format: Document (PDF)

Title: Effects of High Alkalinity Cements on the Control of Alkali-Silica Reaction for Reinforced Concrete.
Creator: Suarez, Jorge Alejandro, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In previous research, cements with high alkali content (EqA 1.0-1.2 percent) extended the corrosion initiation time of reinforcing steel in concrete. During this study, laboratory tests were performed to determine the suitability of high alkalinity cements to improve concrete durability without modifying physical properties and to control the risk of alkali-aggregate reaction (AAR). A mix design for the FOOT-Class V concrete served as base material for this study. On a cubic meter basis the...
Show moreIn previous research, cements with high alkali content (EqA 1.0-1.2 percent) extended the corrosion initiation time of reinforcing steel in concrete. During this study, laboratory tests were performed to determine the suitability of high alkalinity cements to improve concrete durability without modifying physical properties and to control the risk of alkali-aggregate reaction (AAR). A mix design for the FOOT-Class V concrete served as base material for this study. On a cubic meter basis the cementitious material in this concrete included 363 kg of Type l/ll Portland cement and 83 kg of Class F fly ash. The water-to-cementitious material ratio of the concrete was 0.40. The fine aggregate used in the experimental concretes was quartz sand from a Florida source with no history of alkali-silica reactivity (ASR) susceptibility. A number of cement alkali contents were prepared by different additions of sodium hydroxide to the concrete mix (3.42 - 4.57 kglm\ in some cases, and by using different cements in others. Thus, effects on concrete susceptibility to ASR, electrical resistivity, and strength were studied. Pore water alkalinity was measured by ex-situ leaching and pore water extraction methods. It was concluded that leaching procedures were not appropriate to determine concrete pore water alkalinity in the presence of fly ash. Results suggested that it is feasible to use high alkali cement without the risk of ASR or the loss of strength for two of the seven coarse aggregates studied, given that supplementary cementitious materials and lithium nitrate admixtures are utilized. Criteria for qualification of a concrete as being ASR resistant was based on dimensional stability (less than 0.01% average specimen length change) and the absence of cracking over the one and two year exposure periods according to ASTM Cl293. Based on the fundamentals of the electric double layer theory, the incidence of bivalent cations adjacent to the surface of cement hydrates and reactive silica particles was proposed to provide an explanation for the effects of alkali addition on the electrical resistivity of concrete and the source of the expansive nature of the ASR gel.
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Date Issued: 2006
PURL: http://purl.flvc.org/fau/fd/FA00012578
Subject Headings: Reinforced con crete construction, Concrete--Deterioration, Alkali-aggregate reactions, Silica
Format: Document (PDF)

Title: EFFECTS OF NATURAL SEAWATER AND CATHODIC POLARIZATION OF HIGH CYCLE FATIGUE OF 5086-H34 ALUMINUM.
Creator: FLODDER, STEVEN PAUL., Florida Atlantic University, Hartt, William H.
Abstract/Description: High cycle fatigue tests were conducted using symmetrical center cracked plate specimens in air, sea water and constant potentials of -1.0V and -1.3V(SCE) at 20 Hz. (1200 cycles per minute) to determine what effect these environments had on crack growth rates, delta a/delta n (inches per cycle), of 5086-H34 aluminum when plotted against stress intensity range, delta K (Ksi root of in). Crack growth rates of 10^-8 inches per cycle were obtained which indicated that apparent threshold stress...
Show moreHigh cycle fatigue tests were conducted using symmetrical center cracked plate specimens in air, sea water and constant potentials of -1.0V and -1.3V(SCE) at 20 Hz. (1200 cycles per minute) to determine what effect these environments had on crack growth rates, delta a/delta n (inches per cycle), of 5086-H34 aluminum when plotted against stress intensity range, delta K (Ksi root of in). Crack growth rates of 10^-8 inches per cycle were obtained which indicated that apparent threshold stress intensities, delta K th, exist which are the same for air, sea water and a constant potential of -1.0V(SCE); however, under a constant potential of -1.3V(SCE) the threshold shifts to a significantly higher value. It was also observed that the different enviroments had a pronounced effect on crack growth rate only at low stress intensities. Several mechanisms are considered to explain this behavior.
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Date Issued: 1977
PURL: http://purl.flvc.org/fcla/dt/13859
Subject Headings: Aluminum--Testing, Aluminum--Fatigue
Format: Document (PDF)

Title: The effects of substrate, surface finish, flow rate and exposure duration on calcareous deposits.
Creator: Mantel, Katherine Elizabeth., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The effect of substrate finish and composition, flow rate and exposure duration on the composition, morphology and protective properties of calcareous deposits formed during cathodic polarization of several steels in seawater has been investigated. The current density behaviour of the scale formation in conjunction with morphology and composition characteristics indicated that the substrate finish and composition did not influence the nucleation or growth of the deposit. The results strongly...
Show moreThe effect of substrate finish and composition, flow rate and exposure duration on the composition, morphology and protective properties of calcareous deposits formed during cathodic polarization of several steels in seawater has been investigated. The current density behaviour of the scale formation in conjunction with morphology and composition characteristics indicated that the substrate finish and composition did not influence the nucleation or growth of the deposit. The results strongly suggest a relationship between electrolyte velocity, current density behaviour and morphology. With increased flow and consequent higher current density requirements, results indicated a low nucleation rate of CaCO3. The current density behaviour and composition of the calcareous deposit revealed a growth progression of a Mg rich film formed in the first few minutes, followed by an increasingly uniform surface coverage by CaCO3 in the form of aragonite.
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/14575
Subject Headings: Steel--Cathodic protection, Calcium carbonate
Format: Document (PDF)

Title: Embrittlement susceptibility of corroded pre-stressing steel in concrete during cathodic polarization.
Creator: Poeydomenge, Arnaud., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Experiments and analyses were performed to better define the limits of concern regarding hydrogen embrittlement in association with application of cathodic protection to prestressed concrete. To accomplish this, prestressed concrete specimens were locally corroded to different levels by anodic polarization and then polarized to -1.30 V SCE. A procedure of examination was developed using strain gauges to determine the level of prestrain. Relatively few brittle failures of wires resulted due,...
Show moreExperiments and analyses were performed to better define the limits of concern regarding hydrogen embrittlement in association with application of cathodic protection to prestressed concrete. To accomplish this, prestressed concrete specimens were locally corroded to different levels by anodic polarization and then polarized to -1.30 V SCE. A procedure of examination was developed using strain gauges to determine the level of prestrain. Relatively few brittle failures of wires resulted due, at least in part, to a relatively low prestrain of the pretensioned tendons. A model was developed which, coupled with data from parallel research, permitted definition of the minimum cross section for brittle failure as a function of the magnitude of prestrain and corrosion morphology of the wire. These results were tabulated in a format that can be used during field inspection to identify structural elements for which fracture could occur upon application of cathodic protection.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/15417
Subject Headings: Prestressed concrete--Corrosion, Cathodic protection, Prestressed concrete--Embrittlement, Prestressed steel construction
Format: Document (PDF)

Title: Environmental cracking of prestressing steel in calcium-hydroxide solutions.
Creator: Kumria, Chetan Chand., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Failure of prestressed steel tendon in concrete due to corrosion or environmental cracking (or both) has become a major technological concern because of increased utilization of this form of construction in corrosive exposure such as coastal bridge deck structures. At the same time cathodic protection has evolved as the most practical means for arresting corrosion of reinforcing steel in existing structures. This technology also applies to pretensioned tendons. However, concerns have been...
Show moreFailure of prestressed steel tendon in concrete due to corrosion or environmental cracking (or both) has become a major technological concern because of increased utilization of this form of construction in corrosive exposure such as coastal bridge deck structures. At the same time cathodic protection has evolved as the most practical means for arresting corrosion of reinforcing steel in existing structures. This technology also applies to pretensioned tendons. However, concerns have been raised that cathodic protection might cause embrittlement, since yield stress of these materials is relatively high. For the purpose of analyzing this embrittlement tendency a series of constant load and slow strain rate experiments were performed and the data evaluated. Influence of potential, chloride concentration, pH and precharging on the cracking susceptibility have been evaluated. The cracking process has been explained based on test results and SEM analysis.
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/14531
Subject Headings: Steel, High strength--Brittleness
Format: Document (PDF)

Title: Environmental cracking of reinforcing steel in saturated calcium hydroxide solutions.
Creator: Mathew, Ivan., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Deterioration of reinforcing steel in concrete structures due to rebar corrosion is of national and international concern. Cathodic protection has evolved as the appropriate mitigating technique for existing structures. Another method which is being investigated is the electrochemical removal of chlorides from concrete. The current density used for this process leads to steel potentials at which hydrogen evolves. This raises concern regarding hydrogen embrittlement of reinforcing steel in...
Show moreDeterioration of reinforcing steel in concrete structures due to rebar corrosion is of national and international concern. Cathodic protection has evolved as the appropriate mitigating technique for existing structures. Another method which is being investigated is the electrochemical removal of chlorides from concrete. The current density used for this process leads to steel potentials at which hydrogen evolves. This raises concern regarding hydrogen embrittlement of reinforcing steel in concrete. For the purpose of analyzing this embrittlement tendency, a series of constant extension rate experiments was conducted in saturated calcium hydroxide solutions using notched and smooth specimens. While notched specimens did not show any effect of hydrogen embrittlement, the smooth specimens have revealed a reduction in ductility at high current densities. Experiments have shown that this loss in ductility is recoverable. Tests were also conducted on mortared smooth specimens which essentially exhibited the same trend observed as in the calcium hydroxide solution. The loss in ductility has been attributed to the enhanced void development in the presence of hydrogen during plastic deformation.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14639
Subject Headings: Steel--Corrosion, Steel--Brittleness
Format: Document (PDF)

Title: Evaluation of carbon fiber/polyetheretherketone composites exposed to marine microbial communities in laboratory media and natural seawater.
Creator: Sheetz, Andrew Douglas., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This research proposed to characterize any microbial induced degradation of carbon fiber/polyetheretherketone (PEEK) composites from acid-producing bacteria (APB) and sulfate-reducing bacteria (SRB). Electrochemical impedance spectroscopy (EIS) was used to provide a measure of degradation of the composite system as a function of exposure time. In addition, mechanical testing and microscopic evaluation of the specimens were utilized to determine if changes in the EIS spectra as a function of...
Show moreThis research proposed to characterize any microbial induced degradation of carbon fiber/polyetheretherketone (PEEK) composites from acid-producing bacteria (APB) and sulfate-reducing bacteria (SRB). Electrochemical impedance spectroscopy (EIS) was used to provide a measure of degradation of the composite system as a function of exposure time. In addition, mechanical testing and microscopic evaluation of the specimens were utilized to determine if changes in the EIS spectra as a function of exposure time correlated to changes in the mechanical properties. Results from most EIS scans were consistent with a well-consolidated and undamaged composite system. Changes in the EIS response of specimens exposed to the SRB environment were not matched by a reduction in the flexural strength. Mechanical testing also indicated no reduction in the flexural strength in any of the other exposure environments. Environmental scanning electron microscopy (ESEM)/energy dispersive x-ray spectroscopy (EDS) were inconclusive, though changes in the EDS spectra were seen. No definitive degradation was seen to occur in this composite system.
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Date Issued: 1998
PURL: http://purl.flvc.org/fcla/dt/15531
Subject Headings: Corrosion and anti-corrosives, Composite materials--Biodegradation
Format: Document (PDF)

Title: Evaluation of Corrosion Resistant Ferric-Alloys in Chloride Contaminated Concrete.
Creator: Himiob, Rodrigo J., Hartt, William H., Florida Atlantic University
Abstract/Description: The penetration of chloride ions through concrete can compromise the integrity of a structure. The chloride concentration, [Cl-], at which the corrosion process initiates is termed the critical chloride concentration or chloride threshold, [Cl-]th. One of the purposes of this research was to determine the [Cl-]th for various reinforcing alloys. Furthermore, the time-to-corrosion (TIC) was measured to determine the time at which bars become active. Both parameters, [Cl-]th and TTC, were found...
Show moreThe penetration of chloride ions through concrete can compromise the integrity of a structure. The chloride concentration, [Cl-], at which the corrosion process initiates is termed the critical chloride concentration or chloride threshold, [Cl-]th. One of the purposes of this research was to determine the [Cl-]th for various reinforcing alloys. Furthermore, the time-to-corrosion (TIC) was measured to determine the time at which bars become active. Both parameters, [Cl-]th and TTC, were found to be distributed; therefore, statistical analyses were performed to forecast the probability of activity. A new experimental procedure was introduced to increase the TTC data set by electrically isolating the top bars as they became active. The research also compared the [Cl-] for core samples with those values obtained from along the top rebar trace. In general, this analysis demonstrated that core sample [Cr] was lower than at the rebar-trace.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012527
Subject Headings: Steel--Corrosion, Reinforcing bars--Corrosion, Chlorides
Format: Document (PDF)

Title: Experimental and Modeling Study of Chloride Ingress into Concrete and Reinforcement Corrosion Initiation.
Creator: Yu, Hui, Hartt, William H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Effects of reinforcement and coarse aggregate on chloride ingression into concrete and reinforcement corrosion initiation have been studied with experimental and modeling (finite element method) analyses. Once specimens were fabricated and exposed to a chloride solution, various experimental techniques were employed to determine the effect of reinforcement and coarse aggregate on time-to-corrosion and chloride ingress and concentration at corrosion locations. Model analyses were performed to...
Show moreEffects of reinforcement and coarse aggregate on chloride ingression into concrete and reinforcement corrosion initiation have been studied with experimental and modeling (finite element method) analyses. Once specimens were fabricated and exposed to a chloride solution, various experimental techniques were employed to determine the effect of reinforcement and coarse aggregate on time-to-corrosion and chloride ingress and concentration at corrosion locations. Model analyses were performed to verify and explain the experimental results. Based upon the results, it was determined that unexpectedly higher chloride concentrations were present on the top of the rebar trace than that to the side at the same depth and an inverse concentration gradient (increasing [Cl-] with increasing depth) occurred near the top of rebars. Also, coarse aggregate volume profile in close proximity to the rebar and spatial distribution of these aggregates, in conjunction with the physical obstruction afforded by reinforcement to chloride flow, complicates concrete sampling for Cl- intended to define the critical concentration of this species to initiate corrosion. Modeling analyses that considered cover thickness, chloride threshold concentration, reinforcement size and shape, and coarse aggregate type and percolation confirmed the experimental findings. The results, at least in part, account for the relatively wide spread in chloride corrosion threshold values reported in the literature and illustrate that more consistent chloride threshold concentrations can be acquired from mortar or paste specimens than from concrete ones.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012582
Subject Headings: Reinforced concrete construction--Corrosion, Chlorides--Diffusion rate, Composite reinforced concrete, Concrete--Chemical resistance
Format: Document (PDF)

Title: Experimental and theoretical characterization of near-threshold fatigue crack growth for high strength steels in seawater.
Creator: Yang, Jingjun., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Near-threshold fatigue crack growth rate data were generated for six high strength steels at stress ratios of 0.5 and 0.8 under different environmental conditions, which included air, freely corroding in seawater, and cathodically polarized in seawater to -0.80v, -0.95v and -1.10v (vs SCE). The influence of stress ratio, loading frequency, magnitude of cathodic polarization and initial DeltaK on fatigue crack growth behavior for these high strength steels was experimentally characterized. The...
Show moreNear-threshold fatigue crack growth rate data were generated for six high strength steels at stress ratios of 0.5 and 0.8 under different environmental conditions, which included air, freely corroding in seawater, and cathodically polarized in seawater to -0.80v, -0.95v and -1.10v (vs SCE). The influence of stress ratio, loading frequency, magnitude of cathodic polarization and initial DeltaK on fatigue crack growth behavior for these high strength steels was experimentally characterized. The results disclosed general trends of fatigue crack growth under conditions relevant to offshore structure applications and circumscribed variables that are primarily influential with regard to service performance. The rate controlling processes and cracking mechanisms of near-threshold fatigue crack growth, particularly under cathodic polarization in seawater, were also studied in conjunction with crack mouth opening displacement measurements, fractographic observation and crack profile examination. The data and observations suggest that calcareous deposit induced closure was the rate-controlling factor for near-threshold fatigue crack growth under cathodic polarization in seawater although the cracking involved a brittle failure mechanism as a result of hydrogen embrittlement. With different FCGR determining procedures which included natural K-decreasing, enhanced K-decreasing, natural K-increasing and constant DeltaK, the FCGR under cathodic polarization in seawater was found to be time-dependent and, as such, was not a unique function of DeltaK but depended upon K-history or experimental procedures. These observations were consistent with results of a theoretical analysis which involved kinetics modeling of the interaction between fatigue crack growth and calcareous deposit thickening. The model also predicted the existence of an upper limit transition DeltaK, DeltaK Upp/T, between the Paris and threshold regions and it was found that the predicted DeltaK Upp/T was in agreement with the experimental one. The basis for applying this critical parameter (DeltaK Upp/T) to offshore structure designs was addressed in conjunction with experimental results.
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Date Issued: 1995
PURL: http://purl.flvc.org/fcla/dt/12410
Subject Headings: Seawater corrosion, Steel--Fatigue, Steel--Fracture, Corrosion and anti-corrosives
Format: Document (PDF)

Title: FATIGUE CRACK DEVELOPMENT IN CATHODICALLY POLARIZED WELDED STEEL IN SEAWATER.
Creator: WEHLING, CHRISTOPHER MARK., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The fatigue crack growth behavior of welded ABS DH32 steel spec~mens cathodically polarized to -1.00 volt (Cu-CuS04) and subjected to bending fatigue of nominal stress + 69 MN/m^2 (+- 10 ksi) in seawater was investigated. Small non-propagating surface cracks with lengths up to 4.93 mm formed in the specimens. There were no s~gns of failure after 36 x 10^6 cycles when the experiment was terminated. Comparison of this test with similar freely corroding and -0.85 volt (Cu-CuS04) tests indicated...
Show moreThe fatigue crack growth behavior of welded ABS DH32 steel spec~mens cathodically polarized to -1.00 volt (Cu-CuS04) and subjected to bending fatigue of nominal stress + 69 MN/m^2 (+- 10 ksi) in seawater was investigated. Small non-propagating surface cracks with lengths up to 4.93 mm formed in the specimens. There were no s~gns of failure after 36 x 10^6 cycles when the experiment was terminated. Comparison of this test with similar freely corroding and -0.85 volt (Cu-CuS04) tests indicated that -1.00 volt (Cu-CuS04) cathodic protection is conducive to arrestment of small fatigue cracks. This suggests that modest cathodic over-protection of steel in seawater may beneficial.
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Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14091
Subject Headings: Steel--Fatigue
Format: Document (PDF)

Title: Fatigue crack growth rate of short cracks for high strength steels in sea water.
Creator: Kim, Kijoon., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Experiments have been performed which determined the fatigue crack growth rate (FCGR) of short cracks (a > 0.1mm) for five high strength steels (yield stress 370-570 MPa) in air and in natural seawater with and without cathodic protection. Attention was focused upon Regions I and Il of the classical FCGR-stress intensity range(Delta K) curve with particular consideration of the near-threshold behavior for short cracks. Single edge notch (SEN) three-point bend specimens and a direct current...
Show moreExperiments have been performed which determined the fatigue crack growth rate (FCGR) of short cracks (a > 0.1mm) for five high strength steels (yield stress 370-570 MPa) in air and in natural seawater with and without cathodic protection. Attention was focused upon Regions I and Il of the classical FCGR-stress intensity range(Delta K) curve with particular consideration of the near-threshold behavior for short cracks. Single edge notch (SEN) three-point bend specimens and a direct current potential drop (DCPD) crack monitoring system were employed, and test parameters simulated offshore structure conditions. The results indicated enhanced FCGR for short cracks compared to macrocracks by 3-20 times in air and 2-6 in seawater free-corroding(FC). Also, the Delta Kth for short cracks was apparently lower than for long ones in both environments. The transition from short to long crack behavior occurred at constant $\Delta$K in each environment (15.6 MPa m in air and 10.0 MPa m in seawater(FC)) irrespective of initial Delta K (Delta K(0)). The transition crack length ranged from 0.25 to 1.6 mm and was inversely proportional to $\Delta$K(0). Scanning electron microscope fractography showed that the mechanism of enhanced crack growth rate was associated with secondary crack (SC) formation in air and SC or inter-granular cracking (or both) in seawater (FC). The enhanced FCGR for short cracks was minimized by polarization to -950 mV(SCE). Through an elastic-plastic fracture mechanics analysis using the J-integral parameter it was found that the influence of plastic deformation at the crack tip was approximately independent of crack length (short versus long), and the linear-elastic fracture mechanics analysis gave a realistic representation for fatigue behavior.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/12313
Subject Headings: Steel--Fatigue--Environmental aspects, Underwater acoustics, Seawater--Acoustic properties
Format: Document (PDF)

FAU Theses and Dissertations (80)	+ -
HBOI Faculty Contributions (1)	+ -
Florida Atlantic University Patents (1)	+ -

Steel--Corrosion (19)	+ -
Cathodic protection (15)	+ -
Steel--Fatigue (9)	+ -
Corrosion and anti-corrosives (8)	+ -
Reinforced concrete--Corrosion (8)	+ -

Chlorides (6)	+ -
Sea-water corrosion (6)	+ -
Seawater corrosion (6)	+ -
Offshore structures (4)	+ -
Pipelines--Cathodic protection (4)	+ -
Seawater (4)	+ -
Steel--Cathodic protection (4)	+ -
Underwater pipelines (4)	+ -
Aluminum--Corrosion (3)	+ -
Concrete--Corrosion (3)	+ -
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Marine steel (2)	+ -
Post-tensioned prestressed concrete construction (2)	+ -
Prestressed concrete--Corrosion (2)	+ -
Reinforced concrete (2)	+ -
Reinforced concrete construction (2)	+ -

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article (1)	+ -
patent (1)	+ -

Florida Atlantic University (81)	+ -
College of Engineering and Computer Science (54)	+ -
Department of Ocean and Mechanical Engineering (54)	+ -
Clark, A. M. (2)	+ -
Suarez, Jorge Alejandro (2)	+ -

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