Results Of Non-destructive Tests Research Articles

Application of neural fatigue cohesive element to R-DCB model with in-situ training strategy

In this work, a recently developed fatigue delamination growth (FDG) simulation tool driven by neural network (Neural Fatigue Cohesive element, NFCOH) is validated using a benchmark model that offers complex crack front known as the R-DCB model. The NFCOH is tested using two different training strategy for the driving neural network, i.e., a regular training strategy and an in-situ training strategy. For the regular training strategy, virtual samples based on material fatigue properties in the form of Paris parameters are generated to train the neural network. Whilst for the in-situ training strategy, samples are generated using non-destructive testing (NDT) results of the R-DCB model. The results for both strategies are presented and compared to demonstrate the advantages as well as disadvantages of each strategy and NFCOH in general.

Correlation between thermal and density properties of chestnuts: preliminary results of experimental non-destructive testing

This study presents the preliminary outcomes of a methodology for the physical and mechanical characterization of various chestnut elements in different states of preservation. Strategizing conservation and retrofit interventions for timber is necessary, and to do this, it is necessary to establish an estimation of physical (transmissivity, thermal conductivity, humidity level, etc.) and mechanical properties (density, compressive or bending strength, etc.). This essential information is typically associated with timber defects, but there are lack of correlations. The primary objective is to establish correlations between thermal and density properties with the aim of preserving original assets. The investigation delves into the relationship between timber density and thermal properties through experimental non-destructive testing (NDT). Two NDTs were employed with the aim of correlating: penetrometric testing and active thermography investigations. The parametric study on the excitation period yielded valuable insights into the temporal dynamics of heat transfer within the timber, underscoring the significance of selecting appropriate excitation periods to capture precise thermal properties. Tabular data on relative humidity for salified, dried, and new samples provided a quantitative backdrop to these observations, unveiling the nuanced effects of humidity on the timber’s thermal response. The results of this study are positioned to inform future conservation efforts by laying the groundwork for a comprehensive understanding of timber’s mechanical properties. Particularly, the challenge lies in accurately estimating density, where surface tests are often less reliable than in-depth ones. Therefore, it is crucial to seek validation through other NDT tests, such as thermographic analysis and visual inspection, and hygrometric tests recognizing their importance in enhancing the reliability of density assessments. This approach will contribute to the development of more discerning preservation strategies.

Ultrasonic non-destructive inspection method for glass fibre reinforcement polymer (GFRP) hull plates considering design and construction characteristics

The design and construction characteristics, including glass fibre weight fraction ( Gc), number of single-ply layers, fabric combination, and fabrication quality, of glass fibre reinforcement polymer (GFRP) hull plates affect ultrasound propagation characteristics, such as ultrasonic velocity and attenuation, thereby influencing the accuracy of ultrasonic non-destructive test results. Therefore, this study is to propose a method to decrease the ultrasonic test errors of GFRP hull plate by using statistical method. The GFRP specimens with Gc of approximately 30–50 wt%, thicknesses of approximately 5–20 mm, and different fabric combinations were prepared using the hand lay-up method, considering the general design–construction characteristics. Further, an ultrasonic velocity decision method for ultrasonic inspection was proposed considering the GFRP hull design-construction characteristics, such as Gc and number of single-ply layers of hull plate by multiple linear regression method. The results show that the proposed method can reduce the thickness measurement error from approximately 20%–30% to 1%–2%, compared to an existing ultrasonic inspection method, only considering the Gc effect on ultrasonic velocity, which indicates that the proposed test method is suitable for practical applications.

Novel flat-top laser-aided cold metal transfer additive manufacturing for titanium alloy: Arc characteristics, microstructure, and tensile properties

In this paper, a novel flat-top laser-aided cold metal transfer additive manufacturing (F-LCAM) method is proposed for titanium alloys to restrict internal defects and anisotropy of mechanical properties in large-scale additive-manufactured titanium structures. The proposed method uses a flat-top laser to stabilise the drifting cathode spot and suppress the irregular shape of the weld deposit by promoting thermionic emission on the molten pool surface. Compared to the cold metal transfer additive manufacturing (CMT-AM) process, the auxiliary flat-top laser promotes the wettability of the molten pool and increases the contact angle of deposition from 95° to 142° in an F-LCAM sample. The non-destructive X-ray testing (NDT) results of multi-bead multilayer deposition showed that the defects caused by the pool weld bead morphology were effectively suppressed. Attributed to fluid flow in the melt pool enhanced by the flat-top laser, the dendritic arms were broken, columnar β grains in the F-LCAM sample were finer than in CMT-AM sample, and the aspect ratios of prior-β grains decreased from approximately 6 to 1. The F-LCAM sample exhibited a higher elongation and lower anisotropy than the CMT-AM sample. Defects were observed on the fracture surfaces of the CMT-AM vertical samples, which reduced the elongation of the CMT-AM samples to lower than that of the F-LCAM sample. The ultimate tensile strength, yield strength, and elongation of the multi-bead multilayer deposition met the standards of as-forged Ti6321 titanium alloy, indicating that the Ti6321 titanium alloy structure fabricated by the F-LCAM process has acceptable tensile properties for engineering applications.

Enhancing load prediction for structures with concrete overlay using transfer learning of time–frequency feature-based deep models

This study proposes a method to predict applied loads on bonded structures via non-destructive testing results. Various types of concrete, such as high-performance alkali-activated slag concrete (HPAASC) and regular Portland cement concrete (OPCC) are simultaneously tested via ultrasound testing and bi-surface shear for extracting features and target values, respectively. Variational Mode Decomposition is employed to extract useful features from ultrasound signals. In the first part, selected features using a PCA-based method are utilized to train a set of deep-learning models to estimate the imposed mechanical load on the tested specimens. The most effective models from the first step, i.e., a CNN-LSTM model and LSTM models, are then fine-tuned in the second step to estimate loading conditions in another set of specimens. Results indicate the superior performance of the CNN-LSTM model. The proposed algorithm highlights the effectiveness of ultrasound features in accurately evaluating structural loading conditions for efficient monitoring of various structures.

Damage of a post-tensioned concrete bridge – Unwanted cracks of the girders

The cracking of a post-tensioned T-beam superstructure, which was built using the incremental launching method, is analyzed in the paper. The problem is studied in detail, as specific damage was observed in the form of longitudinal cracks, especially in the mid-height zone of the girder at the interface of two assembly sections. The paper is a case study. A detailed inspection is done and non-destructive testing results of the girders are briefly discussed. The attention is especially focused on advanced and comprehensive numerical simulations of the bridge mechanical behavior. Linear and nonlinear static calculations are performed employing the Finite Element Method at global and local levels of precision, enabling deep insight into the bridge response during all the stages of bridge construction and after it is opened to traffic. The crack propagation process in local analyses is described by the application of the Concrete Damage Plasticity law, the parameters of which were carefully chosen. The predicted damage patterns closely resemble those observed at the site. The results reveal, that the girder damage process was initiated when centric prestressing was applied, because vertical reinforcement of the assembly section front-end surface was not designed. However, the damage did not compromise the safety of the bridge. Finally, the repair methods employed are described and also a discussion is presented on how to prevent the occurrence of such cracking.

Artificial Neural Network Approach for Assessing Mechanical Properties and Impact Performance of Natural-Fiber Composites Exposed to UV Radiation.

Amidst escalating environmental concerns, short natural-fiber thermoplastic (SNFT) biocomposites have emerged as sustainable materials for the eco-friendly production of mechanical components. However, their limited durability has prompted research into the experimental evaluation of the deterioration of the mechanical characteristics of SNFT biocomposites, particularly under the influence of ultraviolet rays. However, conducting tests to evaluate the mechanical properties can be time-consuming and expensive. In this study, an artificial neural network (ANN) model was employed to predict the mechanical properties (tensile strength) and the impact performance (resistance and absorbed energy) of polypropylene reinforced with 30 wt.% short flax or wood pine fibers (referred to as PP30-F or PP30-P, respectively). Eight parameters were collected from experimental studies. The ANN input parameters comprised nondestructive test results, including mass, hardness, roughness, and natural frequencies, while the output parameters were the tensile strength, the maximum impact load, and absorbed energy. The model was developed using the ANN toolbox in MATLAB. The linear coefficient of correlation and mean squared error were selected as the metrics for evaluating the performance function and accuracy of the ANN model. They calculate the relationship and the average squared difference between the predicted and actual values. The data analysis conducted by the models demonstrated exceptional predictive capability, achieving an accuracy rate exceeding 96%, which was deemed satisfactory. For both the PP30-F and PP30-P biocomposites, the ANN predictions deviated from the experimental data by 3, 5, and 6% with regard to the impact load, absorbed energy, and tensile strength, respectively.

Evaluation of the historic wooden structure condition based on the results of non-destructive tests

Deformation of wooden roof structures is the effect of strength parameters reduction caused by biological corrosion, passage of time, looseness in joints and assembly inaccuracies. It is a significant problem, especially in buildings built several hundred years ago. Over many years of operation, historical structures are exposed to various loads, not only from their own weight or from external environmental influences (wind, snow). There are also accidental loads such as fires or warfare. Repairs and reconstructions, carried out as a result of accidental damages, are also important for the building structure. Renovation processes often influence on changes in the static scheme of the originally constructed structural system. Rheological phenomena of structural elements and joints have a significant impact on the redistribution of internal forces.In the paper the thorough condition evaluation of the historical church building is presented. The evaluation is performed with the use of non-destructive testing (NDT) methods. The analyzed church building was built in 1579–1601. Throughout its history, it was rebuilt after a fire when the structure of the roof and ceiling above the main nave was reconstructed. Then the roof covering was changed from heavy ceramic tiles to light sheet metal covering, and finally the sheet metal was replaced with metal roof tiles. In the meantime, the roof structure suffered damage resulting from the war, and a part of the roof structure had to be replaced. The current condition of the roof truss was analyzed using finite element method (FEM) software. The influence of the condition of carpentry joints on the deformation of the roof truss was analyzed. The duration of load (DOL) effect on the deformation of structural elements, as well as the influence of biological corrosion and uneven distribution of wood strength parameters in individual structural elements were considered. Based on the presented detailed analysis of the condition of the historic wooden structure using NDT methods, suggestions regarding the general applicable area in historic structures were formulated.

Assessing the Influence of Banana Leaf Ash as Pozzolanic Material for the Production of Green Concrete: A Mechanical and Microstructural Evaluation.

This paper reports an investigation of the mechanical and microscopic properties of partially replaced banana leaf ash (BLA) concrete. In this research, the cement was partially replaced by BLA in two phases: Phase A (0%, 5%, 10%, 15%, 20%, 25% and 30%) and Phase B (0%, 10%, 20% and 30%). The consequence of partially replacing cement with BLA in concrete was investigated by the application of a range of tests, namely X-ray fluorescence (XRF), compressive strength, splitting tensile strength, flexure strength, ultrasonic pulse velocity and scanning electron microscopy (SEM) analysis. The properties were then correlated with the properties of a standard 100% Portland cement concrete of similar strength. The XRF result of the BLA identified a composition with 48.93% SiO2 and 3.48% Al2O3, which indicates that the material potentially possesses pozzolanic properties. The mechanical properties of the partially replaced BLA concrete noted minor strength loss, approximately 5% with 20% partial replacement. The nondestructive testing data showed enhanced performance up to 20% partial replacement, with ultrasonic pulse values above 3500 m/s. The scanning electron microscopy analysis illustrated that the morphology of BLA specimens contained increased microcracks compared with the control. The decrease in strength observed is attributed to the fibrous composition of the BLA. The mechanical, nondestructive testing and microscopic results highlight the potential to utilize BLA as a partial replacement for cement as a pozzolanic material in concrete at up to 20% by weight of cement.

Framework for assessing bridge quality index based on the correlation of non-destructive test results

This paper presents the new method for quality indexing of bridge components on the basis of non-destructive tests (NDT) for the assessment of the structural condition of Reinforced Concrete (RC) bridges. For the purpose of establishing indexing values, results obtained from the Electrical Resistivity Test (ERT), Rebound Hammer Test (RHT), Ultrasonic Pulse Velocity Test (UPVT), and visual inspection were used as the NDT variables. The radar plot for index determination is based on the area of the polygon whose vertices are formed on the basis of the correlation coefficient between NDT variables. Then, using the radar plot formulation, a bridge quality index is introduced to evaluate the corrosion and strength properties of in-service RC bridges to determine their structural health. The bridge quality index ranges from 0 to 1, representing low to high levels of deterioration. Based on simply non-destructive testing, the bridge quality index can serve as a framework for evaluating the present condition of the bridge and its components.

Prediction Models for Mechanical Properties of Cement-Bound Aggregate with Waste Rubber

The high stiffness of cement-bound aggregate (CBA) is recognized as its main drawback. The stiffness is described by the modulus of elasticity, which is difficult to determine precisely in CBA. Incorporating rubber in these mixtures reduces their stiffness, but mathematical models of the influence of rubber on the mechanical characteristics have not previously been defined. The scope of this research was to define a prediction model for the compressive strength (fc), dynamic modulus of elasticity (Edyn) and static modulus of elasticity (Est) based on the measured ultrasonic pulse velocity as a non-destructive test method. The difference between these two modules is based on the measurement method. Within this research, the cement and waste rubber content were varied, and the mechanical properties were determined for three curing periods. The Edyn was measured using the ultrasonic pulse velocity (UPV), while the Est was determined using three-dimensional digital image correlation (3D DIC). The influence of the amount of cement and rubber and the curing period on the UPV was determined. The development of prediction models for estimating the fc and Est of CBA modified with waste rubber based on the non-destructive test results is highlighted as the most significant contribution of this work. The curing period was statistically significant for the prediction of the Est, which points to the development of CBA elastic properties through different stages during the cement-hydration process. By contrast, the curing period was not statistically significant when estimating the fc, resulting in a simplified, practical and usable prediction model.

Advantages of Friction Welding of Fittings with Small Diameter Conical Contact Form

Introduction. As numerous production tests show, the use of manual arc welding (MAW) of thick-walled fittings of small diameter (up to 80 mm) does not provide a high-quality weld joint that meets the requirements of regulatory and technical documents of nuclear power plants (NPP). The solution to this problem is possible on the basis of research and development of welding technology with optimal heat input instead of MAW. Existing fusion welding technologies do not allow for optimal regulated heat input. However, this can be realized during the development and further use of the friction welding (FW) method. Therefore, this work aimed at developing a technology based on an automated technique of friction welding, which could provide the enhancing of the quality of weld joints of small diameter fittings of power equipment to the level of regulatory requirements.Materials and Methods. Small diameter fittings with a conical contact surface made of low-alloy steel 10GN2MFA were used. The experimental study was performed on a friction welding machine MST–41. Methods of non-destructive and destructive quality control were used in accordance with the regulatory and technical documentation of nuclear power engineering.Results. A methodology was developed, and the optimal dimensions of the conical contacting surface under welding were determined. It was shown that optimal heat input during friction welding was achieved by preparing a conical contacting surface in the angle range α = 30º–40º. The methodology and parameters of the friction welding mode for models of small diameter fittings were experimentally tested. In the course of the research, a cyclogram of the friction welding process was obtained and described, which confirmed the stage-by-stage formation of the weld joint due to the sequential inclusion of annular sections of the conical surface of the connected parts in the heating stage. The results of non-destructive and destructive testing were obtained, confirming the presence of a high-quality weld joint at the level of the requirements of the regulatory and technical documents of the NPP.Discussion and Conclusion. The obtained research results can be used to develop the technology of friction welding of pipes, as well as products made of carbon and low-alloy steels.

Degradation of SMA-13 low-temperature performance under coupled dry and wet-salt corrosion

To investigate the low-temperature performance of polyester fiber-modified asphalt mixtures under the influence of dry-wet-salt corrosion coupling, six different polyester fiber content levels (0%, 0.3%, 0.35%, 0.4%, 0.45%, and 0.5% by weight of the mixture) were chosen for preparing SMA-13 asphalt mixture specimens. The Ultrasonic non-destructive testing, semi-circular bending tests, and scanning electron microscopy (SEM) were employed to evaluate the low-temperature performance of these mixtures under dry-wet-salt corrosion conditions with varying cycle numbers (0, 2, 4, 6, 8 cycles). The results of ultrasonic non-destructive testing showed that the wave velocity exhibited a trend of initial increase followed by a subsequent decrease with the increase in polyester fiber content. It reached a maximum value of 4.06 cm/us at a fiber content of 0.4%. The semi-circular bending tests (SCB) revealed that the fracture toughness of the polyester fiber asphalt mixture decreased as the number of dry-wet cycles increased. The impact of salt-dry-wet coupling > water-dry-wet coupling. Notably, after undergoing 4 cycles of water-dry-wet exposure, the overall fluctuation in specimen fracture toughness was minimal, indicating that results after four cycles could be suitable for evaluating the long-term degradation performance of asphalt mixtures under extended water-dry-wet cycling. SEM test results demonstrated that a polyester fiber content of 0.4% led to the formation of a strong fibrous network structure within the asphalt mixture. This significantly reduced moisture and salt intrusion during the dry-wet cycling process, enhancing the low-temperature crack resistance of the specimens.

Comparing the results of testing a longitudinal tube weld by nondestructive methods

Defects of longitudinal tube welds identified by X-ray inspection are studied in order to determine possible causes of their occurrence and to assess the reliability of nondestructive testing results. Metallographic analysis shows that the base metal and weld metal meet the requirements of regulatory documents. The strength properties and the chemical composition conform to the standards. The contamination with non-metallic inclusions in the segregation streamers of the sheet extending to the edge and falling into the fusion zone was detected in X-ray photographs and incorrectly interpreted as a defect. This assumption is based on the correlation of X-ray patterns with the position of the grooves in the zones of the studied welded joints, but it ignores the results of studying by other nondestructive testing methods, and most importantly, it is not confirmed by metallographic studies. Neither were these defects found in the tubes during magnetic flaw detection by means of a UMD-101M device in the line of production of longitudinally electric-welded tubes. Erroneous defect identification during X-ray inspection happens in tube making. The results of the study show the expediency of the integrated application of different testing methods for a reliable assessment of the quality of tubes or pipes of both small and large diameters.

Variation characteristics of key dynamic measurement signals of anchor bolts with different anchorage qualities under pull-out loads

Pull-out load and the cement-sand ratio (CSR) can affect the non-destructive testing (NDT) results of anchor bolts. Therefore, in this article, NDT experiments were conducted on both fully and defectively grouted anchor bolts, and variation patterns of key dynamic testing signal parameters were analyzed. A longitudinal vibration model of defectively grouted anchor bolts considering dynamic and static damping was proposed, and simulated NDT of anchor bolts with varying qualities. The results indicated that grouting defects resulted in an increase in wave velocity, along with a decrease in the fundamental frequency and dynamic stiffness of anchor bolts. When grouting defects and pull-out load acted concurrently, the fundamental frequency, and dynamic stiffness of the defectively grouted anchor bolts were consistently smaller than those of fully grouted ones during the initial loading phase. With pull-out load increasing, wave velocity decreased first, then increased; fundamental frequency increased, followed by a decrease; dynamic stiffness rose. When the CSR of defectively grouted anchor bolts was reduced, wave velocity decreased, fundamental frequency increased slightly, and a substantial increase in dynamic stiffness was observed. Pull-out loads were more sensitive to anchor bolt key dynamic signals than defects and CSR. Simulated validation demonstrated the reliability of the proposed theory.

A Numerical Study on the Fire Induced Collapse of a Real Life Warehouse Structure Based on Post-Fire NDT Results

Fires being a Low-Probability High-Consequence problem, can have a big impact on the structures due to their occurrence; irrespective of the construction materials. Even, the damage might lead to structural collapse. Such failures have warned to check the impact of fire on structural elements, which is frequently overlooked in popular design guidelines. Warehouses are used for the storage of different types of commodities; however, the vulnerability of these structures during fire event depends on the storage materials and other factors. Such a warehouse with steel roof trusses supported over Reinforced Cement Concrete (RCC) frame, located at Kolkata, suffered one of such severe fire-induced damage; and the roof truss system along with some portions of the brick masonry walls got totally collapsed. The information about the structure including its design data is presented along with the site observations after the fire incident, and the results of various Non-Destructive Tests (NDTs) performed over RCC frame elements. A severe fire of 8-hour duration led to a huge increase in temperature, which is considered to be the main reason of the progressive collapse of the entire warehouse structure. To better understand the failure of members due to temperature load, the present study aims to analyse a numerical model of the damaged structure in the Finite Element (FE) Framework. The roof truss, RCC frames and brick masonry walls are modelled; and temperature load is applied along with self-weight load to check the effect of incremental temperature on various structural responses of the warehouse. The temperature-dependent material properties are considered in the analyses; as applicable. Results have shown that there is a significant effect of temperature load, which gets worse with increasing temperature. The connection between roof truss and columns also contributes to the extent of damage in the truss supported over RCC frames; as evident from the numerical analysis. The present study seems to present a clear view about the fire-induced structural collapse of a real-life warehouse structure

Research on the manufactured Technology of High-precision Load Connecting Frame Structure with Special-shaped Variable Shaped Cross-section

Aiming at the research and development technology of high-precision load connecting frame structure with special-shaped variable cross-section reinforced by internal cross bars, the two-step weaving and stitching fiber preform forming process scheme and the general RTM product forming process scheme of load connecting frame are discussed by using the comparison method; The virtual simulation of RTM glue injection process is studied by using ESI Group software, and the results show that the completion time of the glue injection process with four sprues is about 29.4% of that of the glue injection process with only one sprue, which guides the design of RTM molding design; The key process of product manufacturing, such as the glue injection and curing process of the product and the quality control process during the technological process, are analyzed, and the performance of the final product is evaluated. Through the research on the manufacturing process, we have overcomed the major constraints on several molding technologies, such as the two-step fiber preform molding technology of weaving and stitching, the RTM molding design and processing technology of complex and special-shaped composite products, the split molding technology, and combination finishing processing technology after secondary bonding. The results prove that the formed products have better forming quality, dimensional accuracy and thermal cycle dimensional stability. The nondestructive testing results of composite parts show that the internal structure of the product is good. The fiber volume fraction is controlled at (55 ± 3)%, the flatness of the important surface of the product is 0.05 mm and 0.03mm respectively, and the dimensional accuracy of the important interface is controlled within ± 0.02 mm. The dimensional stability after the thermal cycle test is good, and all indicators of the product meet the user’s requirements, which achieved expected goals. The success on the manufacturing of these products provides a technical basis for the design and manufacture of high-precision and high stiffness composite structures for deep space exploration and manned spaceflight.

Evaluation of compressive strength of concrete durability degradation in dry and wet environments using destructive and non-destructive testing

To develop an effective non-destructive testing (NDT) method to assess the strength of concrete in dry and wet cyclic environments, concrete compressive strengths were evaluated of six different mix ratios in this study using ultrasonic method, rebound method and quasi-static compression tests indoors. Firstly, the results of concrete indoor quasi-static compressive strength tests were compared with the NDT results and the optimum NDT methods applicable to different concrete strength classes were determined. Subsequently, an in-situ NDT evaluation of concrete gates exposed to dry and wet environments for a long-term period was carried out based on the results of the laboratory indoor tests, and the degradation mechanism of concrete strength under dry and wet cyclic conditions was revealed by rebound method testing, borehole coring, and industrial computerized tomography (CT) scanning. The results show that the concrete strength obtained by the ultrasonic rebound method is closer to the actual value when the initial strength of concrete is less than 30 MPa; When the initial strength of concrete is between 30 and 40 MPa, the concrete strength obtained by the rebound method is closer to the actual value; When the initial strength of concrete is greater than 40 MPa, the concrete strength obtained by the rebound and ultrasonic rebound methods differ greatly from the quasi-static compressive strength. In addition, the compressive strength of concrete increases and then decreases with the number of dry and wet cycles increases. In the early stage of the dry and wet cycle, the main reason for the increase of the concrete strength is that the filling of the pores by the hydration products reduces the porosity of the concrete; As the number of dry and wet cycles increases, the hydration products absorb water to expand and lose water to shrinkage, which leads to microcracks, and this is the main reason for the decrease of the concrete strength in the late stage of the dry and wet cycle.

Ni-based coating on 5083 aluminum alloy with Cu-Ni interlayer fabricated by ultra-high-speed laser directed energy deposition

Through the innovative design of interlayer connection materials, a high-performance wear-resistant and corrosion-resistant composite protective coating was successfully prepared on the surface of 5083 aluminum alloy using ultra-high-speed (0.5 m/s) laser energy deposition technology. By conducting orthogonal experiments and analyzing the coating morphology and non-destructive testing results, the optimal process parameters for preparing the Cu-Ni25 alloy interlayer and nickel-based alloy surface protection layer were determined. The bond strength and friction resistance of the composite coating and the substrate were tested by shearing and scratch tests. Furthermore, the wear and corrosion resistance of the nickel-based alloy protective layer and substrate were comparatively assessed using an abrasive wear tester, electrochemical workstation, and salt spray test chamber. The results show that the Cu-Ni25 alloy interlayer plays a good bridge role and realizes metallurgical bonding with the aluminum alloy matrix. Additionally, the addition of the nickel-based alloy surface protection layer yields a significant improvement in deformation resistance, wear resistance, and seawater corrosion resistance compared to the aluminum alloy substrate.

The assessment of concrete subjected to compressive and flexural preloading using nondestructive testing methods, correlation between concrete strength and combined method (SonReb)

The objective of the research study is to investigate the influence of stress conditions on Non-destructive testing (NDT) methods. The experimental campaign was conducted on the aged concrete using both destructive tests (DT) and non-destructive tests (NDT) simultaneously. Two type of concrete were prepared, the first with 350 kg/m3 cement dosage, and the second with 400 kg/m3 cement dosage. The samples were tested unloaded and loaded at 20 %, 40 %, 60 %, and 80 % of the maximum compressive or flexural strength to predict these mechanical properties of concrete. The NDT tests were applied on concrete cubes to study the effect of a compressive load, while for a flexural load; reinforced and unreinforced concrete beams were formed and tested in different zones (compressed, tensioned, and neutral axis). The results of this study indicate that the stress conditions affect the NDT results, it was found that the reduction in RN and UPV of concrete subjected to 80 % compressive load was 9.4 % and 8.1 % respectively, while when subjected to 80 % flexural load the reduction was 2.5 % and 1.4 %. In addition, the results show a good relationship between the destructive test and the non-destructive test obtained by UPV and RN.