Search

Glulam timber is gaining popularity as a structural element due to its cost-effectiveness, strength, and environmental benefits. However, being an organic material, it is susceptible to degradation. Therefore, nondestructive testing (NDT) methods are essential for assessing its structural health. In this study, two NDT approaches, ultrasound-based and modal updating, were used to predict the static bending modulus of elasticity (MOE) in Pinus Sylvestris and Spruce species. The results demonstrated that the modal updating and linear regression models outperformed the ultrasound technique in accurately determining the static MOE. Additionally, considering the influence of knots improved the accuracy of ultrasound predictions. [ABSTRACT FROM AUTHOR]

Over the past decades, sandwich structures have shown impressive performances in impact resistance and damage tolerance, which has allowed their innovations in various disciplines to flourish. The birth of sewn sandwiches has given, on the one hand, elements with structural cores that participate in the resistance to transverse shearing and, on the other hand, sandwich skins that contribute to resisting forces from the same direction to achieve an assembly, giving the structure an optimal lightness. After evaluating the behavior of said structure against impact stresses, in this study, it is proposed to start by evaluating the effect of damage caused by impacts of different energies. Then, their influence on the structure's mechanical properties and its ability to undergo one or more new impacts will be checked. For this, by using a microscope, diagnostic tests have been carried out for each sample after the first impact, followed by characterization by non-destructive tests based on vibration analysis in order to examine and compare the properties of a healthy plaque with those of the affected plaques. The tests are carried out on samples of dimensions 150 × 200 × (1.5 + 20 + 1.5 = 23) mm³. The results obtained by using the specialized software PULSE have encouraged a second series of effects on these samples. [ABSTRACT FROM AUTHOR]

The paper aims to present a bibliographic study of works on the characterization of materials, for mosques and historical minarets, using destructive methods (uniaxial compression, tension direct and indirect), and nondestructive testing (Schmidt rebound hardness, ultrasonic pulse velocity (UPV), scanning electron microscope (SEM) and X-ray diffraction (XRD) and their usefulness in the field of protection built cultural heritage. These religious buildings usually are constructed of brick masonry, stone, or/and reinforced cement concrete. Further, the form and amount of a structural defect is a function of the environment to which the structure is subjected. The different techniques used, for various construction materials, have determined the following parameters: the surface hardness, pulse velocity, structural composition, compressive strength, tensile strength and chemical composition. In general, these parameters govern the behavior under the different actions, and contribute to the strengthening and protection of the structure. [ABSTRACT FROM AUTHOR]

Polyolefin fiber is a new type of fiber that was used in concrete to improve some of the poor properties of concrete including; tensile strength, ductility, and fracture energy. In this research, the contribution of Polyolefin fiber in improving the properties of hardened concrete was examined by adding polyolefin fibers to mix with different fiber content. The polypropylene fibers were added as a ratio of 0.5, 0.75, 1.0, 1.5, and 2% of concrete volume. Destructive and non-destructive tests were carried out: slump, compression, splitting, and bending, Schmidt Hammer, and ultrasonic pulse velocity tests. The results showed that, as the polyolefin fiber content increases, the workability of concrete reduces dramatically. The experimental findings demonstrate that the concrete tensile strength and ductility were improved by a small improvement in overall compressive strength. The results show that the compressive strength increased gradually with the increase in fiber content of up to 1.5%, and then, the compressive strength starts to decrease. However, the tensile strength increases continuously with the fiber content increasing. A good relationship was obtained between the destructive and nondestructive tests.

• The damage evolution during fatigue tests and residual strength tests is characterized by AE, DIC, and Micro-CT. • The information recorded by different characterization instruments is classified and compared for verification. • Pearson correlation analysis of classified damage facilitates quantitative analysis of the residual strength evolution. The accumulation of fatigue damage leads to continuous degradation of the residual strength of three-dimensional braided composites, directly determining the fatigue life. However, the inability to continuously collect residual strength and multiple damage modes pose a challenge to study the residual strength degradation mechanisms of three-dimensional braided composites. In this work, digital image correlation and acoustic emission techniques are employed to assess the strain field and damage events of the specimens during the residual strength tests. X-ray computed tomography facilitates the visualization and quantification of the fatigue damage evolution in three-dimensional braided composites. Moreover, the "two-step" damage classification method is applied to isolate the damage mechanisms. The Pearson correlation analysis is preformed between the quantitative results of three non-destructive techniques and residual strength degradation of 3D braided composites. The integration of the outcomes provides a comprehensive depiction of the residual strength degradation mechanisms. [ABSTRACT FROM AUTHOR]

Limited studies have gathered information on structural health monitoring (SHM) of underwater structures, and most of those studies are outdated. The existing methods evaluated structural distresses separately, without accounting for the correlation between the distresses. This study developed a SHM tool which accounts for the reciprocal relationships and priority weights of different structural distresses, and assessed underwater structures using the developed structural health monitoring tool. A new rating method was developed using fuzzy analytic hierarchy process (FAHP) which incorporates visual inspections of surface distresses, nondestructive tests (NDTs), crack details, hydraulic conditions, and casual characteristics of the underwater structures. The SHM tool was applied to 12 underwater structures, including bridges, dams, canals, water tanks and quay walls. The results of NDTs such as rebound hammer tests and ultrasonic pulse velocity tests, crack surveys, and visual observations on underwater concrete structures are employed in the SHM tool and the structures were rated using priority weights allocated to different attributes. The SHM tool developed in this study supports enhanced efficiency and effectiveness of structural health monitoring of underwater structures and proposes a numerical framework which can be employed to rate and compare the structural health of different underwater concrete structures. [ABSTRACT FROM AUTHOR]

Measurements and characterization for extremely harsh environments require accurate approach especially by means of image-based computer vision. Because of harsh conditions, such as high temperature, pollution, turbulences, radioactive exposure, high energy, direct measurements through conventional sensors are not easy even with recent sensing technologies. Live and/or shortest time-delayed sensing, by means of imaging, can come to help to overcome the aforementioned constraints. The paper outilines the use of sensed images for characterizing the effects of high temperatures, at the inlet of a blast furnace, during the discharge of materials using a chute. This latter is subject to wear due to chemico-physical reactions at around 350-450 °C. Given the specific application related to the harsh environment, two algorithms are comparatively proposed and updated for the purposes of the paper; they are based both on computer vision, namely monadic technique and conventional neural network. For the first technique, virtual sensors have been introduced within the image thanks to sinogram and backprojection subtechniques. The results highlight the effects of the environment on the layers of anti-wear compounds applied on the chute, then they permit to understand the chute life-cycle. Quantitative percentage of material detection has been included as well as specific metrics for machine learning expression. [ABSTRACT FROM AUTHOR]

This paper determines the effect of steel, glass, and nylon fibers on the elastic modulus of concrete. The effect of different fiber volume fractions (0.1, 0.25, 0.5, 0.75, 1, and 1.5% vol.) and water-cement ratios (w/c: 0.32 to 0.6) on the elastic properties of concrete was investigated using the fundamental resonant frequencies. Experiments were carried out on more than 100 standard cylindrical specimens. The experimental values were determined using resonance frequencies and compared to the available empirical equations in the literature and those of ACI 318 and ACI 363. The dynamic elastic modulus of concrete in the longitudinal and transverse directions were determined experimentally using the resonance test gauge (RTG). Moreover, the dynamic modulus of rigidity of concrete was also determined using the RTG. The results show that the modulus of elasticity of fiber-reinforced concrete (FRC) with a coarse-to-fine aggregate ratio (C/S) less than 1 decreases with the addition of fibers. A new equation to better evaluate the elastic modulus of FRC within the range of 0.1 to 1.5% of fiber volume fraction is proposed. The proposed equation shows good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Concrete is considered an isotropic material for structural analysis and design purposes. However, during concrete placement and compaction, segregation and bleeding may occur. A water film is deposited around larger aggregate particles, especially on the bottom surface. This effect was already identified in the literature as a cause of anisotropy in compression strength, but there is no evidence of anisotropy of concrete in terms of elastic constants. In this paper, impact acoustics and ultrasound measurements were used to measure dynamic elastic properties in prismatic specimens (125×125×400 mm). The specimens were produced with two directions of concrete placement and compaction: longitudinal and transversal. Three concrete batches were produced with high, medium, and low percentages of cement. Five identical specimens were produced for each combination of concrete mix and direction of concrete placement. A pattern of anisotropy was identified for all specimens through natural frequencies of the specimens and measured ultrasonic wave velocities. Although this effect is small, it could be clearly identified by impact acoustics and ultrasonic tests. [ABSTRACT FROM AUTHOR]

Structural integrity is a major concern for both manufacturers and consumers, thus health monitoring is mandatory for a proper quality control. The use of more reliable and widespread techniques is urged. In this context, this work developed a nondestructive procedure for microstructural characterization of age-hardened aluminum alloys. By the combination of ultrasonic inspection parameters, we developed two highly sensitive methods of hardness evaluation. The results proved the versatility of ultrasonic waves for materials inspection and characterization, expanding the onsite evaluations range. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The LHC collimation system must adopt materials with excellent thermal shock resistance, high electrical conductivity, geometrical stability, and radiation hardness. Two novel composites, Molybdenum–Carbide–Graphite and Copper–Diamond, are proposed for the LHC collimation upgrade. A postirradiation examination was performed to assess the status of the composites, tested under intense proton beam impacts at the CERN HiRadMat facility. Metrology measurements, computed tomography, and 3D topography allowed to evaluate the localized spallation induced by the beam. This article provides an overview of the thermophysical characterization of the two composites before irradiation and nondestructive postirradiation results. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Vibration Engineering is the property of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In the competitive world of aircraft industry, the reduction of maintenance periods is a decisive factor when companies and arm forces are undergoing the procurement processes for the acquisition of their next fleets. Thus being, the investigation in the aeronautical sector today is focusing not only in the development of better and more reliable aircraft systems, but also in the development of techniques and tools that allow for the performance of the required maintenance tasks in faster and more optimized manners. This work arises within this field of investigation addressing the validation of innovative failure preventive equipment for the evaluation of the electromechanical impedance (EMI) response of aeronautical structures, and for the dynamic balancing of propellers of aircraft in the category of Normal, Utility, Aerobatic and Commuter. This work is divided into two parts, in which the first explores the accuracy and competitiveness of one alternative nondestructive test (NDT) equipment developed by Critical Materials S.A. in aeronautical applications, when compared to the classical NDT methods. This part ends with the assessment of the technique's capability to identify defects in one EPSILON TB-30 Nose Landing Gear of the Portuguese fleet which had been put out of service through a high-frequency eddy current inspection. The second part regards the development of a maintenance equipment for the dynamic balancing of propellers systems, specifically optimized for the dynamic balancing of the propeller of the Lycoming engine used in TB-30 aircraft of the Portuguese Air Force. This study ends by highlighting the gains achieved in the overall TB-30 maintenance costs with the use of the developed tool, by comparing the average time used for the process of balancing the Lycoming propeller, with and without the use of this tool. Highlights • The evaluation of the electromechanical impedance response of aeronautical structures was performed • The accuracy and competitiveness of one alternative nondestructive test equipment was explored • The validation of a failure preventive tool for aeronautical applications was carried out • The development and validation of an engine monitoring tool for the dynamic balancing of aircraft propellers was developed [ABSTRACT FROM AUTHOR]

Abstract We employed 2D/3D X-ray computed tomography in conjunction with microzone analysis to study the failure mechanisms of lithium-ion battery packs at low temperatures. A nondestructive X-ray computed tomography strategy confers the direct and comprehensive observation of the hard-swelling of lithium-ion battery packs at low temperatures. X-ray computed tomographic images indicate that severe wrinkles occur in the electrode components, thus shedding light on the evolution of the failure process, which provides a valid secondary analysis of the failure mechanisms without damaging the battery pack. Combined with the results of the microzone analysis, swelling failure can be attributed to the generation of Li dendrites, volume expansion and delamination of the active materials. These processes can be caused by the slow electrochemical kinetics of the active materials at low temperatures. Graphical abstract Image 1087 Highlights • 2D/3D X-ray computed tomography has been applied to studied failure of LIBs. • Nondestructive detection combined with micro-zone and component analysis is useful. • Research reveals that LIBs easily occur swelling failure at low temperature. • Reason of swelling failure of LIBs has been explored by various characterizations. [ABSTRACT FROM AUTHOR]

Copyright of METU Journal of the Faculty of Architecture / Mimarlık Fakültesi Dergisi is the property of METU Journal of the Faculty of Architecture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work aims to compare the ultrasonic inspection of 9%Ni steel joints welded with the Gas Metal Arc Welding (GMAW) process and Shielded Metal Arc Welding (SMAW) process. These are the two most widely used processes used to weld pipes for CO2 injection units for floating production storage and offloading (FPSO) in the Brazilian oil and gas industry. The SMAW equipment is simple and portable, which is convenient for the FPSO; however, the GMAW process has the advantage of welding with high productivity. In this study we performed a numerical simulation using the software CIVA, 11th version, to analyze the behavior of ultrasonic longitudinal wave beams through GMAW and SMAW dissimilar weld joints. Ultrasonic tests were performed on calibration blocks drawn from both welded joints to evaluate the simulation results. The results are discussed with regard to the microstructure of the weld metal via electron backscatter diffraction (EBSD) analyses. The SMAW process presented better inspection performance than the GMAW process in terms of attenuation and dispersion effects. Although the SMAW had a better outcome, for both processes the configuration of 16 active elements and a scanning angle of 48° resulted in an optimized inspection of the entire joint.

There is a significant rising in development of new concentrated solar plants due to global energy demands. Concentrated solar plant requires to improve the operational and maintainability in this industry. This article presents a new approach to identify defects in the solar receiver tubes and welds employing a simple electromagnetic acoustic transducer. The absorber tubes in normal working conditions must withstand high temperatures, which can cause the tubes to deteriorate in areas such as welding, or it can cause hot spots due to defects or corrosion. A proper predictive maintenance program for the absorber pipes is required to detect defects in the tubes at an early stage, reducing corrective maintenance costs and increasing the reliability, availability, and safety of the concentrated solar plant. This article presents a novel approach based on signal processing and pattern recognition for predictive maintenance employing electromagnetic acoustic transducers. Hilbert transform is used to obtain the envelope of the signal that is smoothed by wavelet transform. It reduces the probability of detecting false-positive alarms. The algorithm uses the distance of the sensors from the edges to perform a self-identification of signal events. The events are located using two possible ways of ultrasound propagation, forward and reverse, and the time of flight of each echo. The algorithm correlates the theoretical events with events found experimentally. These echoes could come from different paths due to the electromagnetic acoustic transducer that generates forward and reverse shear waves. The main novelty in this approach is that the detection and location of the defect is determined considering two echoes that come from the same defect, but they arrive at the sensor flowing by different paths. The results are obtained with a double validation by matching the echoes that meet certain conditions. It increases the accuracy of the inspection and reduces false alarms. The approach has been tested and validated in an experimental platform that simulates the concentrated solar plants. [ABSTRACT FROM AUTHOR]

The ultrasonic pulse velocity method is a nondestructive test commonly used for the determination of the elastic properties of materials and verification of non-homogeneities and damages in structural elements. Another application for the ultrasound is the measurement of the stress state in a material. However, the use of ultrasonic waves for the latter purpose has been poorly studied, mainly regarding application in concrete structures. This paper addresses the use of ultrasound for the evaluation of stresses in concrete structures. Uniaxial compression tests were performed on concrete prisms. During the tests, longitudinal and shear ultrasonic waves were emitted to specimens subjected to different compressive stress levels. The results showed the increase of compression stress leads to higher velocities of ultrasonic waves, which proved the acoustoelastic effect. Such behavior was not observed in longitudinal waves emitted perpendicularly to the direction of the stress application. The largest increase in velocity was observed for longitudinal waves propagating in the same direction of the load application (variations on the order of 1%). Acoustoelastic coefficients were determined for each tested prism, according to the change in the velocities of the ultrasonic waves. The present study contributed to the knowledge on the acoustoelastic behavior of the concrete elements and shows the potential of ultrasonic tests to evaluate the stress state in concrete structures. [ABSTRACT FROM AUTHOR]

Diyarbakir Grand Mosque is one of the oldest and the most significant mosques in the Islamic world and the Mesopotamia. The mosque was heavily damaged due to fire following an earthquake which was predicted 8 magnitude in 1114. It was rebuilt between 1117 and 1125. It is predicted that a great earthquake in the forthcoming years will be occurred in the region. Therefore, conservation and retrofitting works should execute for this 891 years old building. In this study, nonlinear seismic analyses of the main prayer hall of the mosque are performed and damage assessment of it due to a probable great earthquake is determined. Material properties of the mosque are defined by using nondestructive tests. Three level seismic acceleration data are produced by considering seismic characteristics of the region. Damage regions on the mosque are obtained under these earthquake loads. Suggestions about retrofitting of this significant historical mosque are recommended. [ABSTRACT FROM AUTHOR]

Geo-mechanical parameters of intact rocks like uniaxial compressive strength (UCS) and young's modulus (E) have been essentially evaluated for many objects. These parameters are obtained by standard UCS tests that are destructive, expensive, and time-consuming task. By using nondestructive methods such as the ultrasonic or physical tests, the parameters can be indirectly predicted. Consequently, presentation of multiple linear regression equations between destructive and nondestructive parameters is proposed in this paper. In order to predict the UCS and E in terms of density ( ρ), porosity (n), primary wave velocity (V) and shear wave velocity (V), 482 rock samples' data of five sedimentary rock types (in range from limestone to marl) from five different dam sites (located in Asmari formation, southwest of Iran) were analyzed. After regression analysis of the test results, the best fit equations are selected-equations with four independent variables ( ρ, n, V, V) and high coefficients of determination (R) on levels of 0.91 for UCS and 0.88 for E. These equations are simple, practical, and accurate enough to apply. They also can be used in practice for prediction purposes with acceptable accuracy. [ABSTRACT FROM AUTHOR]

A method is developed for presentation of a concrete bridge deck condition assessed by multiple nondestructive evaluation (NDE) technologies using a three-dimensional (3D) visualization program. Four types of NDE data are merged and visualized in the program: (1) impact echo for mapping and describing the severity level of concrete delamination; (2) ultrasonic surface wave for concrete quality (elastic modulus) assessment; (3) electrical resistivity for estimating the corrosion rate of steel reinforcement; and (4) high-resolution imaging of a bridge deck surface for documenting signs of deterioration, previous repairs, and surface wear. The developed visualization platform integrates the four NDE data types and visualizes in a 3D space in a very intuitive way. As such, the program assists in understanding of the complex relationships of bridge deck conditions assessed by multiple NDE techniques. In addition, a correlation between external (surface cracks, wear, and previous repairs) and internal deterioration (delamination, concrete degradation, and corrosion) can be studied and visually identified utilizing the developed 3D visualization program. [ABSTRACT FROM AUTHOR]

The research goal was to assess the stress wave speed in the longitudinal and radial directions of Acer saccharum Marshall and Thuja plicata L. wood and weighting this parameter with the wood density, to determine the dynamic modulus of elasticity. For each species, 32 addoc wood specimens were prepared with an average moisture content of 11 % in which stress waves tests were realized. The experimental design consisted in normality and difference of means tests. The response variables were the wood density and for the longitudinal and tangential directions, the speed of the stress waves and the dynamic modulus. The wood species was considered the variation factor. The stress waves method allowed the dynamic characterization of A. saccharum and T. plicata wood. Significant statistical difference was found between the response variables. The density of A. saccharum wood is greater than the corresponding to T. plicata wood. In the longitudinal direction, the stress wave speed and dynamic modulus of A. saccharum wood are lower than the T. plicata ones. In the tangential direction, the stress wave speed of A. saccharum is bigger than the T. plicata wood. In contrast, the dynamic modulus is smaller. When compared to the tangential direction, the stress wave speed and dynamic modulus are bigger in the longitudinal direction for both species. [ABSTRACT FROM AUTHOR]

Over their lifetime, concrete structures can suffer from different pathologies, one of them is exposure to high temperatures, which diminishes their load-bearing capacity. This study describes how different concrete types were exposed to high temperatures. To simulate fire extinction, where the temperature of the overheated concrete descends suddenly, different cooling systems were applied: slowly cooling in the open air and fast cooling by spraying different water volumes. Several physical-mechanical characteristics were analyzed such as compressive strength, splitting tensile strength, porosity, capillary suction, and carbonation depth. Ultrasound nondestructive tests were conducted to quantify deterioration. A petrographic study using a stereomicroscope and microscopy of polarization was performed on thin sections to evaluate aggregate composition and concrete characteristics, focusing on interface areas. Physical and mechanical properties were affected by the increase in temperature, with damage worsening through the appearance of cracks and microcracks when water is used as a cooling system. [ABSTRACT FROM AUTHOR]

Shrinkage compensating concrete (SCC) and Self-stressing concrete (SSC) technique have been employed for reducing early-age cracking and leakage while the addition of expansive agent would have a negative impact on mechanical properties and durability. The objective of the current research was to quantitatively assess the damage development in cementitious materials with expansive agent by both the strength tests and nondestructive acoustic tests including ultrasonic measurements and acoustic emission (AE) tests. The damage degree was defined based on strength as well as ultrasonic properties and a significant linear relationship was observed between the damage degree and autogenous strains. AE parameters such as AE amplitude, AE counts and AE energy were related to AE activity of the cement-expansive agent system. Crack mode identification was performed based on the relationship between average frequency and RA value (rise time/amplitude). A decreasing ratio of tensile cracks and an increasing ratio of shear cracks were observed which could be an indication of aggravated damage inside the materials. [ABSTRACT FROM AUTHOR]

Degradation of reinforced concrete ( RC) structures is a serious safety problem affecting all industrialized countries, and the economical aspect of this problem cannot be neglected. One of the main reasons for the degradation of RC is the corrosion of steel reinforcing bars as a result of concrete cover cracking and reduction in bar cross section. As a consequence, the structural capacity of RC elements decreases progressively as degradation develops. Nondestructive testing and/or analytical formulation represent high-quality rapid methods for evaluating the corrosion penetration of bars and provide useful parameters for designing retrofits. This paper presents an additional tool that can be used to evaluate and assess the vulnerability of existing structures in terms of the determination of bar cross section lost. Using simple charts and formulas, this can be accomplished by calculating reinforcing bar cross section loss due to corrosion by measuring external crack widths in the concrete cover. Predictions were obtained by using two analytical models developed. These predictions have been satisfactorily compared with both the literature and new experimental results, as well as with previous empirical models available in the scientific literature. The experimental results were obtained by corroding real-scale concrete specimens reinforced with smooth and ribbed bars (according to old and modern building codes) using 3.5 wt% sodium chloride solution and an applied current. [ABSTRACT FROM AUTHOR]

Although several researchers have been working on the mechanical and physical characterization of iron-ore tailings (IOT) in order to consider the possibility of using this material to replace natural aggregate in the preparation of mortars, they have not investigated the dynamic and static modulus of elasticity of IOT mortars yet. Therefore, the main goal of this study is to present an experimental investigation on the determination of the static and dynamic Young’s modulus of IOT mortars using destructive and non-destructive tests respectively. It is also presented the correlation between the IOT mortar static (E ci ) and dynamic (E) elasticity modulus. It is seen that 88% of the observed variation in the elasticity modulus is attributable to the approximate linear relationship between the dynamic and static values, a very impressive result. The results indicate that it is possible to obtain high-performance mortars to be used not only as rendering material but also as structural material in building construction. [ABSTRACT FROM AUTHOR]

Using recycled materials in construction of asphalt pavements yields both economic and technical advantages. Recycled asphalt shingles (RAS) and reclaimed asphalt pavement (RAP) are two major sources to serve this purpose for which proper design and characterization are key elements. In this study, engineering properties of asphalt concrete containing RAP and RAS under dynamic loading were investigated. Three asphalt mixes were designed and included in this research: a conventional mix with no RAP/RAS as a control, a mix with 35% RAP, and finally a mix with 35% RAP and 5% RAS. A conventional resonant column (RC) apparatus was retrofitted and used for testing the specimens in torsional mode. Testing was conducted at five temperatures ranging from 10 to 45°C. Damping ratios and moduli of the mixes were analyzed and compared to assess the effect of the recycled materials on dynamic properties of asphalt concrete. Results clearly show the impact of RAP and RAS in increasing the mix stiffness. The study also included uniaxial dynamic modulus (DM) testing of the control mix to compare the moduli measured at high frequencies through RC testing to those estimated by the DM master curve through extrapolation. Results show that the modulus obtained from RC testing correlates well with that extrapolated from DM tests. Results also indicate that the accuracy of such correlation is significantly increased once dependency of Poisson's ratio on modulus is incorporated. [ABSTRACT FROM AUTHOR]

Pipelines conveying fluids are considered strategic infrastructures to be protected and maintained. They generally serve for transportation of important fluids such as drinkable water, waste water, oil, gas, chemicals, etc. Monitoring and continuous testing, especially on-line, are necessary to assess the condition of pipelines. The paper presents findings related to a comparison between two spectral response algorithms based on the decimated signal diagonalization (DSD) and decimated Padé approximant (DPA) techniques that allow to one to process signals delivered by pressure sensors mounted on an experimental pipeline.

• Interval analysis model is applied to quantify the uncertainties in the elastic wave tomography of concrete structures. • The relationship between the measurements error and tomography uncertainty was established. • The identified uncertain boundaries provide more information to make a better assessment of the internal condition of concrete. This paper presents a non-probabilistic uncertainty quantification method for the elastic wave tomography of concrete structures. An interval analysis model is applied to establish the relationship between the measurement error and identified tomography images. Measurements of parameters such as travel time and wave amplitude are modeled as intervals described by their upper and lower boundaries. Based on the straight-ray assumption of the wave propagation path, the relationship between wave velocity and travel time measurements is described by a set of linear equations. The inversion linear equation is converted into an extended fuzzy linear equation using interval analysis. Subsequently, a simultaneous iterative reconstruction technique is applied to solve this fuzzy linear equation. In contrast to the traditional methods, the obtained tomography images are described in terms of the upper and lower boundaries. Finally, numerical simulation and experimental investigation using several plain concrete models are conducted to verify the proposed approach. [ABSTRACT FROM AUTHOR]

Aluminum alloys have been chosen over other lightweight structural materials because of their advantages regarding strength, long-term durability, and low cost. Aluminum comes under the category of highly reactive metals, where an inherently stable oxide layer can protect against aggressive corrosive conditions. Therefore, this research investigated the application of the ultrasonic nondestructive technique for inspection and monitoring of corrosion behavior of AA6351 heat-treated aluminum alloys. The samples were artificial age hardened at five different conditions. The complementary engineering experiments for materials evaluation included hardness, X-ray diffraction and salt spray tests. Overall findings showed correlations between ultrasonic and destructive data representing a fast, versatile and reliable inspection technique. Furthermore, findings show a significant correlation (>99%), thus supporting the benefits of the multiparametric ultrasonic test for heat treatment inspection and quality control of lightweight structural materials. • The effect of age hardening on the mechanical and corrosion behavior of AA6351 alloys was examined. • Findings support the applicability of the ultrasonic nondestructive tests for corrosion evaluation. • The technique tested enables the determination of peaks and adjacencies of mechanical strength in AA6351 alloys. • The technique tested can be used in Al-alloys in T4 and T6 conditions. [ABSTRACT FROM AUTHOR]

Estimating pavement surface thicknesses without requiring large footprint equipment or pavement repairs is critical for the structural evaluation of airfield pavement. A research team from the U.S. Army Engineer Research and Development Center conducted an evaluation of eleven nondestructive technologies, including eight ground penetrating radar (GPR) devices and three wave propagation technologies, on twenty-one hot-mix asphalt concrete (AC) and nineteen portland cement concrete (PCC) test locations with varying pavement thicknesses. The different technologies were used to estimate pavement thickness over predetermined test points. For each pavement structure, a core was extracted from one of the test points to provide calibration data of each testing device for data refinement. The accuracy of each technology was quantified by calculating the absolute difference between the actual core measurement and the estimated thickness measurement. The results from the devices tested led to the conclusion that separate devices are required on AC and PCC for optimal performance. The ultrasonic tomography and impact echo devices worked best on PCC surfaces, and the 1 GHz horn antenna GPR devices performed best on AC surfaces. The side-by-side testing demonstrated the capabilities of the technologies on varying pavement structures without discrepancies that would likely occur when comparing one set of results to those from a different study. [ABSTRACT FROM AUTHOR]

Drilled shaft foundations are increasingly being used to support various types of buildings and infrastructure facilities. The load carrying capacity of these drilled shafts is largely dependent on their diameter. The large loads carried by such structural elements make quality control and assurance of their diameters during construction extremely critical. Current methods adopted by the industry for measuring drilled shaft diameters during construction depend on discrete points of concrete volumetric measurements that lack both accuracy and continuity. An empirical model is developed and presented in this paper for computing the diameter of drilled shaft foundations that overcomes these limitations. The model is developed using signal processing performed on cross-hole sonic logging (CSL) experimental data obtained from three drilled shaft specimens. The model is validated using experimental data obtained from two separate specimens. The research reported in this paper demonstrates that there exists a high correlation between the maximum amplitude of CSL signal frequency and thickness of concrete. The results show that the model is capable of accurately computing the diameter of drilled shafts, with an absolute average error of 2.42%. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the steel-to-concrete bond phenomenon in two kinds of deformed bars: black steel and hot-dip galvanized steel. The differences in the steel-to-concrete bond behavior are identified in terms of the load-slip curves and the acoustic emission (AE) patterns measured during pull-out tests. Test results show that the bond capacity and the initial stiffness of the bond stress-slip curve of black steel are approximately 20 and 50% greater, respectively, than those of galvanized steel, and the slip corresponding to the maximum bond stress is approximately 20% times larger in the latter. By measuring the AE activity, it is possible to identify the transitional points between the four stages characterizing interaction between the concrete and the bar subjected to pull-out force. Each transition coincides with a sudden drop in the AE activity. [ABSTRACT FROM AUTHOR]

Two dimensional carbon fiber reinforced silicon carbide composites (2D C/SiCs) subjected to low-velocity impact (LVI) damage were investigated, in order to evaluate the efficiency of stitching as a reinforcing mechanism able to improve the delamination resistance of 2D C/SiCs. The damage microstructures of the specimens at different stitched density (SD) were observed by infrared thermography and industrial computed tomography scanners. While the damage depth of specimens with the SD of 10 mm/needle was greater than that of specimens with SD of 5 or 15 mm/needle, the residual tensile strength of the specimens with the SD of 10 mm/needle was the highest. With the decreasing of SD, the real damage radius of 2D C/SiCs measured by thermography increased whereas the residual tensile strength did not appear the same phenomenon. The 2D C/SiCs with the SD of 5, 10, and 15 mm/needle had good damage resistance after the LVI, with the tensile strength still retaining 72.43%, 95.20%, and 91.49%, respectively. [ABSTRACT FROM AUTHOR]

Although the practice of repairing or strengthening concrete infrastructure with externally bonded carbon-fiber-reinforced polymer (CFRP) has become common, the development of robust guidelines and techniques for its quality assurance, inspection, and monitoring is lagging significantly. Whereas common inspection methods (e.g., visual inspection or acoustic sounding) are sufficient to broadly identify deboned regions, it is difficult to reliably and accurately define the boundaries of bond defects, as is often required by acceptance criteria. Infrared thermography is a more sophisticated alternative, but the results of its application are influenced by ambient environmental conditions and operator interpretation of the data. Further, for applications in which multiple layers of CFRP are required, none of these techniques are capable of fully characterizing existing bond defects, including the depth through the thickness. To this end, pulse phase thermography (PPT) has the potential to more reliably and accurately detect the location and size of bond defects. By observing images in the frequency domain, one is able to identify a specific "blind frequency" at which a certain defect is no longer visible, and thereby also predict the defect's depth through the thickness. This paper presents a procedure using PPT to develop a calibrated equation based on blind frequency, specific to the strengthening system, which allows for one to predict the interface at which a bond defect is present for externally bonded CFRP-to-concrete systems. With the development of more robust techniques enhancing quality assurance and reliability, and the facilitation of regular monitoring and inspection, infrastructure owners will gain more confidence in this repair or strengthening technology, ultimately leading to its widespread acceptance and adoption. [ABSTRACT FROM AUTHOR]

Partially saturated compacted-sand specimens were characterized by using three-dimensional (3D) image registration of dualmodal (neutron and X-ray) tomography data. Neutron and X-ray imaging provide complementary information for precisely identifying the three phases (silica sand, air, and water) of a compacted sand specimen that is partially saturated. Neutron tomography provides high contrast of the water phase, whereas X-ray tomography provides high contrast of the silica sand phase due to different fundamental interaction mechanisms of neutron and X-ray with matters. X-ray interacts with the electron cloud surrounding the nucleus, whereas neutron radiation interacts with the nucleus of an atom. In this paper, a computational technique was developed to unify digital images of dual-modal data obtained at different image resolution and specimen orientations based on the maximization of the normalized mutual information to combine the information from the water phase inferred from a neutron image and information from the sand and pore phases obtained from an X-ray image. The combined microstructure obtained from registered X-ray and neutron images can thus be analyzed in 3D to precisely differentiate silica, air, and water distribution spatially. Microstructure information for granular assembly including pore size distribution and coordination number was determined from X-ray tomography data due to higher precision in identifying solid particle boundaries. Local values of saturation along the height of the specimen are obtained from the pore and water phases segmented from the registered neutron and X-ray images. Image registration of neutron and X-ray images provides the ability to obtain the microstructure of partially saturated sand in terms of the detailed variation of solid particles, air, and water phases spatially. [ABSTRACT FROM AUTHOR]

In 2009, a joint American Society of Civil Engineers Structural Engineering Institute and American Association of State Highway and Transportation Officials ad hoc group was created to study how current bridge practices could be improved for the future. Among their recommendations was the wider use of nondestructive evaluation (NDE) techniques. Risk-based planning to determine the appropriate inspection frequency, scope, intensity, and methodology would help make the increased time and costs associated with NDE inspections feasible for management budgets. However, a rigorous risk-based approach requires that the accuracy and reliability be quantified for each test. This paper serves as a starting point for quantifying these important variables and identifies the type of information that is still needed. Common NDE techniques were identified, and existing studies were reviewed to identify what data relevant to accuracy and reliability are currently available for these techniques. This review indicates that there is only a limited amount of quantifiable data available for most common NDE techniques for bridges, and not enough to statistically describe the uncertainty. [ABSTRACT FROM AUTHOR]

The use of X-ray as an inspection technique to ensure the integrity of industrial products dates from the beginning of the 20th century. Therefore, it is a tool of non-destructive inspection widely known. Nowadays, however, there are several researches forward on the optimization of such inspection technique, mainly for the development of an automatic system of radiographic image analysis. That is, a system that can identify and classify the defects in the radiography. An important step in the construction of this system is the classification of defects, which is usually done by using some of their features. The purpose of this work is to study the relevance of some defect features in order to classify some of the main classes of defects. The employed technique is the linear correlation between the defect features and the classes of defects. A non-linear pattern classifier is used, implemented by a neural network, to evaluate the performance in the classification. The results showed the efficiency of the method used.

This paper presents a new nondestructive way of identifying the values of pull-off adhesion between the concrete layers in concrete floors. It based on the roughness parameters of the base layer surface, using the nondestructive optical technique, and on the floor surface, using the nondestructive acoustic techniques and employing artificial neural networks (ANNs) for this purpose. The new way has a potential for being widely used in practice, whereby it may become possible to employ previously trained ANNs to identify the pull-off adhesion, without impairing the surface of the tested concrete floor.

Nondestructive testing (NDT) methods for identifying stress levels in materials mostly rely on the theory of acoustoelasticity. However, the sensitivity and the accuracy of acoustoelasticity are affected by several factors such as the (1) type, (2) propagation, and (3) polarization directions of the used signals. This paper presents the results of an experimental investigation of longitudinal waves propagating perpendicular to the applied uniaxial tensile stresses in structural steel specimens. The changes in four ultrasonic signal characteristics were investigated with increasing stress levels ranging from below to above the yield stress of steel. The considered signal characteristics were the peak amplitudes and signal energy in the time domain, and the fast Fourier transform (FFT) and chirp-Z transform (CZT) in the frequency domain. Even though the acoustoelastic effect on the type ultrasonic signal used is very small, clear distinctions between prior to and postyielding are observed for all investigated parameters. The results are presented with a detailed statistical and receiver operating characteristics (ROCs) analyses. The results show that identifying damage to steel structures due to local yielding is possible using the simple ultrasonic signal classification. [ABSTRACT FROM AUTHOR]

Stress and residual stress are two crucial factors which play important roles in mechanical performance of materials, including fatigue and creep, hence measuring them is highly in demand. Pulse eddy current (PEC) and ultrasonic testing (UT) are two non‐destructive tests (NDT) which are nominated to measure stresses and residual stresses by numerous scholars. However, both techniques suffer from lack of accuracy and reliability. One technique to tackle these challenges is data fusion, which has numerous approaches. This study introduces a promising one called neural network data fusion, which shows effective performance. First, stresses are simulated in an aluminium alloy 2024 specimen and then PEC and UT signals related to stresses are acquired and processed. Afterward, useful information obtained is fused using artificial neural network procedure and stresses are estimated by fused data. Finally, the accuracy of fused data are compared with PEC and UT information and results show the capability of neural network data fusion to improve stress measurement accuracy. [ABSTRACT FROM AUTHOR]

The lightweight deflectometer (LWD) is a portable device that measures surface deflections and applied force, from which dynamic stiffness and elastic modulus can be estimated. The inclusion of radial offset sensors with LWD testing, referred to here as multiple sensor LWD testing, stemmed from the well-established falling weight deflectometer (FWD) testing method. However, little research exists in the literature addressing LWD use on stabilized or lightly bound layers with multiple sensors, or exploring the applicability of backcalculating/ isolating layer moduli from multiple sensor LWD tests. To this end, over 200 multiple sensor LWD tests on stabilized base materials were performed at five sites and rigorously analyzed to determine if the test could capture growth in stabilized base stiffness while the underlying subgrade layer remained unchanged. Deflection results demonstrate that the LWD test is capable of detecting changes in the stiffness of the stabilized base material during curing as illustrated by the decreasing magnitude in center deflections. Furthermore, radial offset deflections measuring 60 cm from the plate center remained constant during curing, providing valuable information about the subgrade support. The findings made directly from the deflections were confirmed via an analytical backcalculation using Boussinesq's equations and Odemark's method of equivalent thickness. The use of multiple sensor LWD testing allows for a richer interpretation of earthwork behavior than the traditional center deflection LWD results. [ABSTRACT FROM AUTHOR]

The results of studies into the usefulness of 3D surface roughness parameters determined by 3D laser scanning, for the nondestructive evaluation of the pull-off adhesion of concrete layers are presented. Twenty-one 3D roughness parameters were identified. Their correlations with pull-off adhesion f b determined by the semi-nondestructive pull-off method were established. For two of the parameters, i.e. the texture aspect ratio ( Str ) and the peak material volume ( Vmp ) the correlation coefficient was found to be high. The possibility of the nondestructive evaluation of the pull-off adhesion on the basis of solely the existing concrete topography examinations is critically looked at. [ABSTRACT FROM AUTHOR]

Clay soil with low-bearing capacities can present great problems underlying pavement and light structures due to uncertainty associated with their performance. This paper describes a sonic based testing methodology for quality control of a surface stabilized soil. From an engineering aspect, an increase in water content has a number of disadvantageous consequences: cohesion decreases, the soil swells, the alternating dry-out/shrinkage and wetting/swelling effects destroy the rock or a soil structure. Cement is mixed into the soil to increase both the strength and the usability of local soils in constructions purposes. This is to overcome the problems by strengthening the soil underlying the structure or diminishing the leads transmitted from the foundation to the soil. The compressive strength of the stabilized soil is highly dependent on the type of soil, moisture content, cement content, and compaction work, and can therefore vary significantly in the field. The authors performed the quality control by measuring the sonic and tensile strength velocity in the stabilized soil that has been correlated to compressive strength in native materials. The improvement of the soil materials by the addition of cement could make the material suitable as filling materials, foundation and/or a road base construction. The quality control for the stabilized soils was investigated using sonic measurements and strength gain. The test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the soil under study. Scanning electron microscopy and electron dispersive X-ray analyses were performed on raw and laboratory treated for qualitative understanding the strength minerals formed during stabilization. The sonic test showed a considerable improvement with curing time and percentages of stabilizer. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of cement treated clay particles suggesting adequate mixing of the soil and binder owing to the strength of the soil materials. [ABSTRACT FROM AUTHOR]

This paper presents a new nondestructive way of identifying the values of pull-off adhesion between the concrete layers in concrete floors. It based on the roughness parameters of the base layer surface, using the nondestructive optical technique, and on the floor surface, using the nondestructive acoustic techniques and employing artificial neural networks (ANNs) for this purpose. The new way has a potential for being widely used in practice, whereby it may become possible to employ previously trained ANNs to identify the pull-off adhesion, without impairing the surface of the tested concrete floor. [ABSTRACT FROM AUTHOR]

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter () varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance () and receiver spacing (), and (2) for two different heights () of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength () and minimum wavelength () associated with the combined dispersion curve, corresponding to a particular combination of and , were noted to increase almost linearly with an increase in the magnitude of the input source energy (). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of . Based on statistical analysis, two regression equations have been proposed to determine and for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. [ABSTRACT FROM AUTHOR]

This paper presents the development and validation of a cyberinfrastructure architecture for research in nondestructive evaluation (NDE) using acoustic emission (AE) data. Existing cyberinfrastructures for civil engineering focus in the curation and preservation of data. In contrast, the proposed cyberinfrastructure is intended to serve as a tool to enable innovation by providing a platform to prototype analysis techniques and sharing data and analysis methods among a research team while removing the burden of memory and computational cost from the user. This is achieved by streamlining the access of large and complex experimental data sets, facilitating the selection of part of the experimental data depending on data features, distributing data analysis using a distributed computing strategy, and allowing the creation of new data features that can be used for subsequent analysis. The experimental data set potentially include data from AE sensors, strain gages, load cells, clip gages, and accelerometers. The proposed framework uses a relational database to store data, web services for data communication, a Condor pool for high throughput computing, and a graphical interface for interaction with the user. An example using data obtained from a compact tension fatigue test is used to show the capabilities of the developed framework. [ABSTRACT FROM AUTHOR]