In Diesel engine blocks properties such as tensile strength, heat conductivity, sound damping, engine vibration and noise are strongly influenced by graphite shape and volume percent in the matrix microstructure. In this study, the engine blocks were produced at ELBA Basin&ccedil / li D&ouml / k&uuml / m Od&ouml / ksan Cast iron foundry in Osmaneli Turkey by performing casting into furan resin sand and preparing cast iron liquid alloy in induction furnace that were treated with Mg by using ladle method. The main purpose of this study is to achive 0 &ndash / 25% volume nodularity and remaining is compacted graphite in the produced engine blocks. The shape and volume percent of graphite particles were characterized by an image analyze system. In the first part of this work, after the diesel engine blocks were produced at ELBA Basin&ccedil / li D&ouml / k&uuml / m Od&ouml / ksan Cast iron foundry in Osmaneli Turkey, the blocks were cut and samples were obtained from 14 different thicknesses of diesel engine blocks. Afterwards, the samples were examined under optical microscope, Soif XJP-6A. The nodularity and compacted graphite values were obtained numerically with the help of Materials Plus image analyzer systems, which is attached to the optical microscope. v In the second part of the study, the diesel engine blocks which are produced at Od&ouml / ksan were examined by ultrasonic test that was done by using USM 35 flaw detector test machine. Solidification &ndash / time and temperature &ndash / time simulations were also done by using NovaCast NovaFlow simulation code. Finally mathematical formulas for 13 different thickness of diesel engine blocks were obtained by using excel linest code. The compacted graphite volume percent observed at different sections of the diesel engine blocks were found to be a function of cooling rate and chemical composition. Best results were obtained when chemical Mg/S ratio was approximately 1 and C.E.V. was between 4.40 &ndash / 4.50.

Polymeric materials are popular in civil infrastructure due to their durability, strength, and resistance to corrosion and environmental degradation. However, the long-term performance of such materials in civil infrastructure is still being researched and investigated. This thesis will focus on the long-term performance of two civil infrastructure applications: 1) high-density polyethylene (HDPE) above-ground storage tanks (AST) and 2) silicone and self-healing polymeric concrete sealants. HDPE is a strong and durable plastic material that is commonly used to store a wide range of liquids ASTs. Currently, there are no established protocols for carrying out non-destructive testing (NDT) and assessment of HDPE ASTs for regular inspections, so this study investigated the viability of using infrared thermography (IRT) and ultrasonic testing (UT) for routine inspection. The study discovered that environmental parameters, such as temperature, wind, and humidity, can affect IRT accuracy, and that a proper heating-cooling cycle can aid in defect detection. Concrete joints in pavement systems are often susceptible to deterioration. They are engineered cracks that enable concrete slabs to expand and contract in response to temperature. They serve the dual purpose of preventing water infiltration and improving ride quality, while extending the pavement's service life. Bridge joints, in particular, are susceptible to water and liquid penetration, which can result in extensive damage over time. By applying sealants to these connections, concrete structures can be protected from such damage, thereby extending their service life. Consequently, a better comprehension of sealant performance and additional research are required to develop effective solutions to address these issues and ensure the safety and longevity of concrete structures prone to cracking. In this study, samples of the two commercial silicone joint sealants were sandwiched between Portland cement mortar specimens and tested using a specially designed fixture to imitate the fatigue performance of the joint under simulated field conditions. The results of the study indicated that the fatigue life of the two silicone sealants were different, with Sealant 2 showed better performance than Sealant 1. Both sealants exhibited adhesive failure initiating debonding along the weak interface of cement mortar cube and joint sealant. The results of commercial sealants are then compared with self-healing polysulfide sealants. This indicates that the performance of sealants can vary, and additional research may be required to develop effective solutions to address these issues. / Master of Science / Polymeric materials are widely utilized in construction due to their durability, strength, and resistance to corrosion and environmental degradation. However, the long-term performance of these materials in civil infrastructure is still under investigation. This thesis specifically examines the long-term performance of two civil infrastructure applications: 1) high-density polyethylene (HDPE) above-ground storage tanks (ASTs) and 2) silicone and self-healing polymeric concrete sealants. HDPE is a robust and durable plastic material commonly employed for storing various liquids in ASTs. Currently, there are no established protocols for conducting non-destructive testing (NDT) and assessment of HDPE ASTs during regular inspections. Therefore, this study investigates the viability of utilizing infrared thermography (IRT) and ultrasonic testing (UT) for routine inspections. The findings reveal that environmental factors such as temperature, wind, and humidity can impact the accuracy of IRT, and implementing a proper heating-cooling cycle can help in detecting such defects inside the tank structure. Concrete joints in pavement systems are susceptible to deterioration. These engineered cracks allow concrete slabs to expand and contract in response to temperature changes, while preventing water infiltration and enhancing ride quality, thus prolonging the pavement's service life. Bridge joints, in particular, are prone to water and liquid penetration, leading to extensive damage over time. Applying sealants to these connections safeguards concrete structures, extending their service life. Consequently, understanding sealant performance and conducting further research are crucial for developing effective solutions to address these issues and ensure the safety and durability of concrete structures prone to cracking. This study involves testing two commercially available silicone joint sealants by sandwiching them between Portland cement mortar specimens. A specially designed fixture is employed to simulate the fatigue performance of joints under field-like conditions. The performance of commercial sealants was also compared with self-healing polysulfide sealants. These findings highlight the variability in sealant performance, emphasizing the need for additional research to develop effective solutions.

Concrete structures can often be modeled as plates, for example, bridges, tunnel walls and pipes. Near-surface damage in concrete structures mostly takes the form of cracking. Surface-breaking cracks affect concrete properties and structural integrity; therefore, the nondestructive evaluation of crack depth is important for structural monitoring, strengthening and rehabilitation. On the other hand, material damping is a fundamental parameter for the dynamic analysis of material specimens and structures. Monitoring damping changes is useful for the assessment of material conditions and structural deterioration. The main objective of this research is to develop new methodologies for depth evaluation of surface-breaking cracks and the evaluation of damping in concrete plates. Nondestructive techniques based on wave propagation are useful because they are non-intrusive, efficient and cost effective. Previous studies for the depth evaluation of surface-breaking cracks in concrete have used diffracted compressional waves (P-waves). However, surface waves exhibit better properties for the characterization of near surface defects, because (a) surface waves dominate the surface response, they carry 67% of the wave propagation energy, and present lower geometrical attenuation because the propagating wave front is cylindrical; and (b) the penetration depth of Rayleigh waves (R-waves) depends on their frequency. Most of the R-wave energy concentrates at a depth of one-third of their wavelengths. The transmission of R-waves through a surface-breaking crack depends on the crack depth; this depth sensitivity is the basis for the so-called Fourier transmission coefficient (FTC) method. R-waves only exist in a half-space (one traction-free surface); whereas in the case of a plate (two traction-free surfaces), Lamb modes are generated. Fundamental Lamb modes behave like R-waves at high frequencies, because their wavelengths are small relative to the plate thickness. Lamb modes are not considered in the standard FTC method, and the FTC method is also affected by the selected spacing between receivers. The FTC calculation requires the use of an explicit time window for the identification of the arrival of surface waves, and the selection of a reliable frequency range. This research presents theoretical, numerical and experimental results. Theoretical aspects of Lamb modes are discussed, and a theoretical transfer function is derived, which can be used to study changes of Lamb modes in the time and frequency domains as a function of distance. The maximum amplitude of the wavelet transform varies with distance because of the dispersion of Lamb modes and the participation of higher Lamb modes in the response. Numerical simulations are conducted to study the wave propagation of Lamb modes through a surface-breaking crack with different depths. The surface response is found to be dominated by the fundamental Lamb mode. Using the 2D Fourier transform, the incident, transmitted and reflected fundamental Lamb modes are extracted. A transmission ratio between the transmitted and incident modes is calculated, which is sensitive to crack depths (d) normalized to the wavelength (λ) in a range (d / λ) = 0.1 to 1/3. A new wavelet transmission coefficient (WTC) method for the depth evaluation of surface-breaking cracks in concrete is proposed to overcome the main limitations of the FTC method. The WTC method gives a global coefficient that is correlated with the crack depth, which does not require time windowing and the pre-selection of a frequency bandwidth. To reduce the effects of wave reflections, which are present in the FTC method because of the non-equal spacing configuration, a new equal spacing configuration is used in the WTC method. The effects of Lamb mode dispersion are also reduced. In laboratory tests, an ultrasonic transmitter with central frequency at 50kHz is used as a source; the 50kHz frequency is appropriate for the concrete plate tested (thickness 80mm), because the fundamental Lamb modes have converged to the Rayleigh wave mode. The new method has also been used in-situ at Hanson Pipe and Precast Inc., Cambridge, Ontario, Canada, and it shows potential for practical applications. In general, the evaluation of material damping is more difficult than the measurement of wave velocity; the dynamic response and attenuation of structural vibrations are predominantly controlled by damping, and the damping is typically evaluated using the modal analysis technique, which requires considerable efforts. The existing methods based on surface waves, use the Fourier transform to measure material damping; however, an explicit time window is required for the spectral ratio method to extract the arrival of surface wave; in addition, a slope of the spectral ratio varies for different frequency ranges, and thus a reliable frequency range needs to be determined. This research uses the wavelet transform to measure material damping in plates, where neither an explicit time window nor the pre-selection of a frequency bandwidth are required. The measured material damping represents an average damping for a frequency range determined by source. Both numerical and experimental results show good agreement and the potential for practical applications.

Concrete structures can often be modeled as plates, for example, bridges, tunnel walls and pipes. Near-surface damage in concrete structures mostly takes the form of cracking. Surface-breaking cracks affect concrete properties and structural integrity; therefore, the nondestructive evaluation of crack depth is important for structural monitoring, strengthening and rehabilitation. On the other hand, material damping is a fundamental parameter for the dynamic analysis of material specimens and structures. Monitoring damping changes is useful for the assessment of material conditions and structural deterioration. The main objective of this research is to develop new methodologies for depth evaluation of surface-breaking cracks and the evaluation of damping in concrete plates. Nondestructive techniques based on wave propagation are useful because they are non-intrusive, efficient and cost effective. Previous studies for the depth evaluation of surface-breaking cracks in concrete have used diffracted compressional waves (P-waves). However, surface waves exhibit better properties for the characterization of near surface defects, because (a) surface waves dominate the surface response, they carry 67% of the wave propagation energy, and present lower geometrical attenuation because the propagating wave front is cylindrical; and (b) the penetration depth of Rayleigh waves (R-waves) depends on their frequency. Most of the R-wave energy concentrates at a depth of one-third of their wavelengths. The transmission of R-waves through a surface-breaking crack depends on the crack depth; this depth sensitivity is the basis for the so-called Fourier transmission coefficient (FTC) method. R-waves only exist in a half-space (one traction-free surface); whereas in the case of a plate (two traction-free surfaces), Lamb modes are generated. Fundamental Lamb modes behave like R-waves at high frequencies, because their wavelengths are small relative to the plate thickness. Lamb modes are not considered in the standard FTC method, and the FTC method is also affected by the selected spacing between receivers. The FTC calculation requires the use of an explicit time window for the identification of the arrival of surface waves, and the selection of a reliable frequency range. This research presents theoretical, numerical and experimental results. Theoretical aspects of Lamb modes are discussed, and a theoretical transfer function is derived, which can be used to study changes of Lamb modes in the time and frequency domains as a function of distance. The maximum amplitude of the wavelet transform varies with distance because of the dispersion of Lamb modes and the participation of higher Lamb modes in the response. Numerical simulations are conducted to study the wave propagation of Lamb modes through a surface-breaking crack with different depths. The surface response is found to be dominated by the fundamental Lamb mode. Using the 2D Fourier transform, the incident, transmitted and reflected fundamental Lamb modes are extracted. A transmission ratio between the transmitted and incident modes is calculated, which is sensitive to crack depths (d) normalized to the wavelength (λ) in a range (d / λ) = 0.1 to 1/3. A new wavelet transmission coefficient (WTC) method for the depth evaluation of surface-breaking cracks in concrete is proposed to overcome the main limitations of the FTC method. The WTC method gives a global coefficient that is correlated with the crack depth, which does not require time windowing and the pre-selection of a frequency bandwidth. To reduce the effects of wave reflections, which are present in the FTC method because of the non-equal spacing configuration, a new equal spacing configuration is used in the WTC method. The effects of Lamb mode dispersion are also reduced. In laboratory tests, an ultrasonic transmitter with central frequency at 50kHz is used as a source; the 50kHz frequency is appropriate for the concrete plate tested (thickness 80mm), because the fundamental Lamb modes have converged to the Rayleigh wave mode. The new method has also been used in-situ at Hanson Pipe and Precast Inc., Cambridge, Ontario, Canada, and it shows potential for practical applications. In general, the evaluation of material damping is more difficult than the measurement of wave velocity; the dynamic response and attenuation of structural vibrations are predominantly controlled by damping, and the damping is typically evaluated using the modal analysis technique, which requires considerable efforts. The existing methods based on surface waves, use the Fourier transform to measure material damping; however, an explicit time window is required for the spectral ratio method to extract the arrival of surface wave; in addition, a slope of the spectral ratio varies for different frequency ranges, and thus a reliable frequency range needs to be determined. This research uses the wavelet transform to measure material damping in plates, where neither an explicit time window nor the pre-selection of a frequency bandwidth are required. The measured material damping represents an average damping for a frequency range determined by source. Both numerical and experimental results show good agreement and the potential for practical applications.

This study focuses on the reliability of railway track in the relation with high loads resulted from wheel damages, where higher (dynamic) vertical wheel loads are expected from trains with damaged wheels. The Swedish Transport Administration (Trafikverket) has monitored and recorded data of rail defects and breaks. This data is important for the risk evaluation and management process, in order to obtain a balance between the maintenance costs and availability and quality of service for the railway transportation. To detect wheel damages in advance, Wheel Impact Loads (WIL) are measured and recorded by Wheel Impact Load Detectors (WILD), which are installed along the Swedish railway network, currently at 29 locations. Additionally, to detect defects and breakages in rails, Ultrasonic Testing (UT) is a common non-destructive testing method used by Trafikverket. In this project, a case study is conducted to examine statistically the frequency of rail defects and rail breaks after trains with high WILs, which exceed 350 kN, continued to operate in a defined area during the winter of 2019/20 at Bodsjön. The case study compares the data of WILD at Bodsjön and UT of the nearby track sections, 211 and 212, over a period of five years, from 2016 to 2020. Rail reliability levels are examined based on the absolute frequencies of rail defects detected by UT and the normalised ones per kilometre of UT-checked track, as well as the severity levels of those rail defects. The severity levels are denoted from the highest to the lowest, as 1a/ 1v/ 1m, 2b and 3i, based on the derailment risks and the priority of maintenance. It is observed that the extremely high WILs in the winter 2019/2020 has coincided with the more severe rail defects found by the following UT in 2020. Furthermore, the dominant rail defect type is found as squats. By studying the frequency of squats and their locations along the defined track sections, it is shown that there is a similar trend in the frequencies of squats and the high WILs. While, the effect of the high WILs’ magnitudes onto the occurrence of squats is undefined. However, the correlation between the frequencies and magnitudes of high WILs and the rail reliability levels could not be determined from this case study due to the limitations in the data collections. The current way of data collections for WILs, wheel damage types and rail defects are discussed for future works. Lastly, the statistics shows that the level of rail reliability of the area defined in the case study is considered as acceptable, considering the recent national levels that have been reported in the annual reports on rail defects. This gives the basis for the possibility of reviewing the permissible power level and proposing a new alert limit value of WIL. Nevertheless, considering the recommendation of The International Union of Railways (UIC) for the international railway sections, the implementation of the increased alert limit of WIL shall be examined carefully, with a future pilot study in railway sections that are not used for international traffic. / Denna studie fokuserar på tillförlitligheten för järnvägsspår i samband med höga laster som orsakas av hjulskador, där högre (dynamiska) vertikala hjullaster förväntas från tåg med skadade hjul. Trafikverket har övervakat och registrerat data om järnvägsfel och avbrott. Dessa uppgifter är viktiga för riskutvärderingen och hanteringsprocessen för att få en balans mellan underhållskostnader och tillgänglighet och kvalitet på järnvägstransportens kvalitet. För att upptäcka hjulskador i förväg, mäts och registreras Wheel Impact Loads (WIL) av Wheel Impact Load Detectors (WILD), som är installerade längs det svenska järnvägsnätet, för närvarande på 29 platser. För att upptäcka defekter och brott i skenor är Ultrasonic Testing (UT) en vanlig icke-destruktiv testmetod som används av Trafikverket.I det här projektet, genomförs en fallstudie för att statistiskt undersöka frekvensen av järnvägsdefekter och rälsavbrott efter tåg med höga WILs, som överstiger 350 kN, fortsatte att köra i ett definierat område under vintern 2019/20 vid Bodsjön. Fallstudien jämför data från WILD vid Bodsjön och UT för de närliggande spåravsnitten, 211 och 212, under en period på fem år, från 2016 till 2020. Järnvägssäkerhetsnivåer undersöks baserat på de absoluta frekvenserna av järnvägsdefekter som upptäcks av UT och de normaliserade per kilometer UT-kontrollerat spår, liksom svårighetsgraden av dessa järnvägsdefekter. Svårighetsgraderna anges från det högsta till det lägsta, som 1a/ 1v/ 1m, 2b och 3i, baserat på urspårningsriskerna och underhållets prioritet.Det observeras att de extremt höga WILs under vintern 2019/2020 har sammanfallit med de allvarligare järnvägsdefekterna som hittades av följande UT år 2020. Vidare återfinns den dominerande järnvägstypstypen som knäböj. Genom att studera frekvensen av knäböj och deras platser längs ett definierat spåravsnitt, visas det att det finns en liknande trend i frekvenserna för knäböj och de höga WILs. Medan effekten av de höga WILs storheter på förekomsten av knäböj är odefinierad. Korrelationen mellan frekvenserna och storheterna för höga WILs och järnvägssäkerhetsnivåerna kunde dock inte fastställas från denna fallstudie på grund av begränsningarna i datasamlingarna. Det nuvarande sättet för datainsamling för WILs, hjulskadetyper och järnvägsdefekter diskuteras för framtida arbeten.Slutligen visar statistiken att nivån på järnvägstillförlitlighet för det område som definieras i fallstudien anses vara acceptabel, med tanke på de senaste nationella nivåerna som har rapporterats i de årliga rapporterna om järnvägsdefekter. Detta ger grunden för möjligheten att granska den tillåtna effektnivån och föreslå ett nytt varningsgränsvärde för WIL. Med tanke på rekommendationen från The International Union of Railways (UIC) för de internationella järnvägssektionerna, ska genomförandet av den ökade varningsgränsen för WIL undersökas noggrant, med en framtida pilotstudie i järnvägssektioner som inte används för internationell trafik.