Nondestructive Testing Research Articles

Research on Rapid Detection Method of Cavitation State of Water jet Propulsion Pump Based on Multi-source and Multi-feature of Acoustic Emission Signal and Bayesian Network

Abstract Cavitation prevents the conversion of internal dynamic and pressure energy in a water jet propulsion pump and causes erosion of flow passage components. Acoustic emission is a non-destructive test method for instability signals. Based on the incipient mechanism and development process of cavitation, three acoustic emission signal feature parameters (ring counting rate, energy release rate, Hurst index) are proposed to define the cavitation state utilizing the waveform pattern and signal self-similarity. The multi-source and multi-feature cavitation identification model of acoustic emission signals is established through cavitation simulation, multi-monitoring point acoustic emission signal testing, and feature parameter extraction, and a large number of probabilistic trainings are carried out using Bayesian network, resulting in a fast cavitation state identification method based on acoustic emission signals. The research results have important practical engineering application significance for the prediction of cavitation resistance, real-time dynamic monitoring of cavitation phenomenon and prevention of cavitation damage.

Developing flaw sizing methodology in Total Focusing Method (TFM) by EDM calibration blocks

The Total Focusing Method (TFM) represents a significant advancement in ultrasonic inspection, delivering high-resolution imaging by leveraging phased array technology combined with sophisticated data processing algorithms. This synergy enables detailed visualization of flaws in various materials, thereby improving flaw detection and characterization. Despite TFM's capabilities, the lack of a standardized methodology for flaw sizing limits its potential for flaw evaluation. This paper seeks to establish a new paradigm in flaw sizing by introducing a custom methodology specifically designed for TFM, using electrical discharge machined (EDM) calibration blocks that reflect a range of flaw shapes. The research highlights the limitations of conventional side-drilled holes (SDH) for capturing realistic flaw nuances and emphasizes the superior ability of EDM notches to simulate the complex geometries inherent in typical flaws. By investigating the influence of different TFM modes, the study provides insight into their effectiveness in improving the accuracy of flaw characterization. Our approach addresses the challenges of existing TFM practices, with EDM notches serving as an essential tool in methodological advancement. This work contributes to the continued development of best practices in TFM application, paving the way for more accurate, reliable, and versatile nondestructive testing.

Monitoring of a fatigue test on a full-size railway steel bridge with acoustic emission

Within the frame of the Rail4Future project (https://www.rail4future.com) co-funded by the Austrian Research Promotion Agency, a railway steel bridge was removed from the track and transported to a workshop in one piece. Artificial defects were introduced at different sections of the bridge structure as per advice of the scientific project partners in order to initiate fatigue cracks in the course of the subsequent fatigue test. One objective of the fatigue test was to identify suitable measurement and testing techniques for monitoring of fatigue crack growth. Among other techniques utilised by different project partners, acoustic emission monitoring was applied by TÜV AUSTRIA. This contribution describes the preparation as well as the performance of the acoustic emission monitoring and the results obtained. It is shown that this non-destructive testing technique is suitable for fatigue crack monitoring.

Application of metal additive testing and thermal conductivity technology in optimizing product appearance design in intelligent manufacturing industry

Metal additive manufacturing technology has the advantages of rapid manufacturing and personalized production, but due to the complexity of the manufacturing process and differences in material characteristics, products made with metal additives often have appearance defects and process performance issues. Therefore, the purpose of this study is to explore the application of metal additive detection technology in product appearance design and process performance optimization. This study proposes a comprehensive detection and optimization method that utilizes non-destructive testing techniques to comprehensively inspect metal components. By identifying and locating these issues, the quality status of the components can be accurately understood. Based on the test results, a series of appropriate optimization measures have been taken to improve the appearance and process performance of the product, adjust process parameters, improve the forming quality and surface smoothness of the components, thereby achieving better appearance effects. Metal additive testing technology can effectively detect and locate appearance defects in products, and by optimizing process parameters and material selection, it can significantly improve the appearance quality and process performance of products, providing support for improving the reliability and production efficiency of industrial manufacturing.

Comparative Study of Mechanical Properties of Self Compacting Concrete Using Binary Pozzolanic Materials

Abstract: The study examined the viability of using waste supplementary cementing materials (SCMs), such as fly ash (FA) and silica fume (SF), as partial replacement of Ordinary Portland cement. The way SCC's fresh properties and hardened were impacted by FA and SF. The study examined the fresh characteristics and hardened characteristics of various distinct SCC mixes using SCC with partial replacement of Ordinary Portland Cement with FA (class F) and SF. First, the cement was replaced by percentages in the mixes 0%, 10%, 15%, 20%, 25%, and 30% by FA and constant replacement of 10% by SF. Then cement was replaced by percentages in the mix with 25% FA constant and 4%, 6%, 8%, 10%, and 12% by SF. For every combination, the water/binder (w/b) ratio was set at 0.43. The EFNARC (Specification and Guidelines for Self-Compacting Concrete) standards were met by the slump flow, T50, and viscosity of the SCC. After 28 days of curing, the blend consisting of 65% PC, 25% FA, and 10% SF had a maximum compressive strength of 41.22 MPa which is 12.07% greater than the compressive strength of the control specimen which is 36.78 MPa. The Split Tensile Strength of the same blend is 4.37% is greater than the control specimen. Non-destructive tests were also performed after 28 days of curing and the regression equations give the excellent relationship between Rebound Number, Ultrasonic Pulse Velocity, and Compressive Strength. This is due to the formation of the proper matrix as the particle size of SF and FA is less than that of cement and the free lime of cement reacts with FA and SF to form C-S-H gel which provides strength.

NON-DESTRUCTIVE METHOD OF IDENTIFICATION OF STEEL GRADES OF ROLLING PRODUCTS

This article presents the results of coercive force dependence study of on the chemical composition and geometric parameters for the purpose of identifying the steel grade in a non-destructive manner. The paper proposes to identify the steel grade by the coercive force, using a correlation with the carbon equivalent and the diameter of the rolled product. As a result of the work, the possibility of identifying steel grades by the carbon equivalent associated with the coercive force and the diameter of the product was established. The ranges of the carbon equivalent for steels St3, 18Mn2Si and 30CrMn2Si were determined. The results of the work established that the coercive force depends on the chemical composition and geometric parameters of the controlled product. Thus, the solutions proposed in this paper are of great practical importance for industrial enterprises for the purpose of steel products prompt identification. The obtained values ​​of the carbon equivalent derived from the proposed dependence correspond to the values ​​of the carbon equivalent calculated according to the standard GOST R 55020-2012. This method of non-destructive determination of steel grade by carbon equivalent through magnetic parameters can be applied to products made of tool and other structural steel grades. Keywords: non-destructive testing, coercive force, carbon equivalent, regression, magnetic properties.

Tunable Luminescent Properties and Multifunctional Imaging Applications of (Gd1-xRx)2O2S:Tb3+ (R = Y, La) Phosphor and Screen.

Gd2O2S:Tb3+ phosphor screens are widely used in image intensifiers, computed tomography, and neutron imaging. To improve the luminescent properties and thermal stability, (Gd1-xRx)2O2S:yTb3+ (R = Y, La) (x = 0, 0.05, 0.15, 0.25, and 0.35; y = 0.02, 0.04, 0.06, 0.08, and 0.10) phosphors were successfully prepared by the carbothermal reduction method. The luminescent spectra showed that the optimum concentrations of Tb3+ ions were 6 and 4 mol % when excited by 292 nm UV light and cathode ray, respectively. The emission wavelengths mainly peaked at 489 and 544 nm. It was found that the introduction of Y3+ ions could improve the luminescent intensity, and the luminescent intensity of (Gd1-xYx)2O2S:0.06Tb3+ was the highest at x = 0.25, while La3+ ions played the opposite role. Then, the thermal stability also improved, and the emission intensities of Gd2O2S:0.06Tb3+, (Gd0.75Y0.25)2O2S:0.06Tb3+, and (Gd0.75La0.25)2O2S:0.06Tb3+ phosphors at 423 K decreased to 66.22%, 68.23%, and 76.10% of the emission intensities at 303 K, respectively. Finally, the (Gd0.75Y0.25)2O2S:0.06Tb3+ phosphor screen was successfully prepared by the gravity deposition method and could be well imaged under UV light and cathode ray excitation with a CMOS camera. In summary, this study demonstrates that (Gd1-xRx)2O2S:Tb3+ (R = Y, La) is a phosphor with excellent luminescent and thermal stability properties and has great potential for application in the field of low-level-light night vision, nondestructive testing, and medical imaging.

Multimodal Non-Destructive In Situ Observation of Crystallinity Changes in High-Density Polyethylene Samples with Relation to Optical Parameters during Tensile Deformation

Abstract: Many non-destructive optical testing methods are currently used for material research, providing various information about material parameters. At RECENDT, a multimodal experimental setup has been designed that combines terahertz (THz) spectroscopy, optical coherence tomography (OCT), infrared (IR), and Raman spectroscopy with a tensile test stage. This setup aims to gather material information such as crystallinity and optical parameters of high-density polyethylene (HDPE) during a tensile test. The setup compares common IR and Raman spectroscopy and the less common optical methods THz and OCT. Complementarity is achieved through different frequency ranges and measurement approaches, resulting in different measured optical material parameters and depths. During tensile testing, HDPE samples with varying crystallinity were analysed, and the determined optical parameters such as refractive index, birefringence, scattering coefficient of decay, and penetration depth can be correlated with the change in crystallinity. These findings demonstrate that the optical methods and their outcomes can be interconnected. With further optimization of the experimental setup, it would be possible to observe the alignment of fibres in fibre composite panels and the stress distribution of polymers effectively. This opens interesting possibilities for polymer characterization in the future, including quality control during moulding processes and material testing.

Iterative Numerical Approximation Technique for 3D Eddy Current Models in Harmonic Regime Based on the Electromagnetic T-Formulation and the Finite Element Method

In this paper, an iterative numerical approximation technique is used for analyzing the distribution of eddy currents density in conductive materials plates by using the electromagnetic T-formulation and the Biot-Savart law, solved by the finite element method. The proposed approach allows for the meshing of the different parts of the studied system separately, including the sensor and the conductive plate, without the need for an air region. Firstly, this approach reduces the number of unknown variables by avoiding the air region of the system's mesh. Secondly, it simplifies the consideration of the sensor's motion without the need to remesh the system. For this purpose, a calculation code has been developed for solving an electromagnetic three-dimensional non-destructive testing model. This latter permits the resolution of JSEAM # 6 Benchmark problem to validate the proposed method. The impedance variation due to the presence of a defect are evaluated. The obtained results are compared with the experimental ones found in the literature. These results reveal a good agreement, which proves the validity of the proposed method.

Evaluation of Physico-Static and Dynamic Elastic Properties of Eucalyptus pellita in Various Thinning Intensities

Acoustic velocity (AV) offers a non-destructive means of reliably measuring wood properties, presenting a valuable alternative to the traditional method known for its destructiveness, costliness, and time consumption. This technique is widely used in the timber industry to predict the bending strength of standing trees and logs. Hence, a study was conducted to assess the dynamic and static elastic properties of Eucalyptus pellita in various thinning intensities using the AV technique and laboratory testing. The selected 11-year-old E. pellita wood was obtained from thinning trials in Sabah Softwood Berhad, Brumas, Sabah. This investigation collected samples from three distinct thinning intensities (0%, 40%, and 60%). Dynamic modulus of elasticity (MOE), which relies on the time of flight (TOF) principle, was measured using an acoustic velocity approach, and physical and static testing was conducted according to standard ISO 13061. Results from this study show that thinning treatments significantly affect the physical and mechanical properties of E. pellita. The study also found that the static modulus of elasticity (MOE) value may be predicted using the acoustic velocity approach, with R2 = 0.46, R2 = 0.60, and R2 = 0.53 on standing trees, billets, and wood slabs, respectively. The application of non-destructive tests in forest plantations can help the foresters assess the wood properties efficiently, and specific parameters can be measured on a tree stand without falling the tree. Besides, thinning at a moderate intensity also helped to enhance the mechanical properties and dynamic MOE value of the E. pellita wood.

Simulation and Experimental Research of V-Crack Testing of Rail Surfaces Based on Laser Ultrasound

Rail surface cracks are widespread damage that can lead to uneven surfaces of railheads and affect traveling safety. Non-destructive testing is needed to inspect rails regularly to ensure the normal operation of railroads. This paper proposes a laser ultrasonic testing method combining variational mode decomposition and diffractive Rayleigh wave time-of-flight to detect tiny cracks on the rail surface quantitatively. The finite element method was combined with experiments to simulate and experimentally investigate cracks of different sizes numerically. In the numerical simulation, the location of the crack was determined by B-scan. Afterward, the interaction between various types of ultrasound and cracks was comparatively analyzed, and the crack size was quantitatively characterized using useful information from the ultrasound signals. The results show that the time-of-flight method can detect arbitrary cracks with low error. Therefore, the experimentally acquired ultrasound signals used the time difference between the diffracted Rayleigh wave and other ultrasound waves to detect the crack information quantitatively. The variational mode decomposition method was used to separate the ultrasonic signals and extract the best surface wave modes to improve the signal-to-noise ratio. The results show that the combination of variational mode decomposition and time-of-flight method can effectively detect the size of cracks.

Hoop tensile properties and crack propagation investigation of 2D braided SiCf/SiC composite tubes: Experiments and simulations

SiCf/SiC composites are promising candidates for advanced pressurized water reactors (PWRs) fuel cladding materials due to their enhanced accident tolerance. Their mechanical properties are strongly influenced by the braided structure of continuous SiC fibers. This study fabricated SiCf/SiC composite tubes with braid angles ranging from 30° to 50°, evaluating their hoop tensile properties through expansion-due-to-compression (EDC) experiments and analyzing the damage process using finite element method simulation. Results indicate that variations in braid angles significantly affect structural density, thereby impacting mechanical strength under hoop tensile stress. Increased braid angles result in smaller pore units and higher pore density, leading to local stress concentrations and varied deflections at overlapping regions. The dynamic propagation behavior of cracks was investigated through acoustic and structural nondestructive testing methods. Finite element analysis of different braid configurations highlights the pivotal role of pore units in the initiation and propagation of hoop tensile cracks. This study enhances the understanding of toughening structures in 2D braided composites and provides a theoretical basis for future accident-tolerant fuel cladding design.

Resistance Welding of Thermoplastic Composites, Including Welding to Thermosets and Metals: A Review.

This review paper presents the current progress in the development of resistance welding techniques for thermoplastic composites, with a particular emphasis on their application in hybrid joints, such as those involving thermosetting composites and metals. Resistance welding, a fusion bonding method, offers significant advantages over adhesive bonding and mechanical joining by eliminating the need for additional adhesive materials and enabling integration into automated manufacturing processes. The study highlights the unique benefits of resistance welding, including lower energy consumption compared to other methods and its compatibility with automated manufacturing, which can reduce production costs by up to 40%. Key findings from the literature indicate that resistance welding is particularly effective in achieving strong, durable joints for complex and large structures, such as those used in the aerospace industry. The review also identifies the main challenges associated with resistance welding, including temperature control, current leakage in carbon-fiber-reinforced polymers, and potential corrosion when using metal meshes. To address these challenges, various strategies are discussed, including surface treatments, the use of nanocomposites, and the integration of carbon nanotubes. The review concludes by emphasizing the need for further research to optimize welding parameters and to develop non-destructive testing methods for industrial applications, ensuring the reliability and long-term performance of welded joints.

Non-destructive ultrasonic testing for identifying concealed weapons and analyzing internal chemical substances

The management of unknown weapons obtained from warfare, military operations, and terrorist situations requires a series of nondestructive testing processes. This management process, which is aimed at collecting information on the nature of the weapons, encompasses identification, processing, transportation, and storage of the obtained weapons. A lack of identification marks in acquired ammunition may indicate the potential presence of a chemical weapon. Therefore, nondestructive evaluation methods have been employed to identify unknown weapons. However, these methods rely on neutron- and radiation-based analyses, which require radiation-handling experts and specific protective facilities. Consequently, their application in this field is challenging. Herein, a nondestructive ultrasonic testing method, which can identify substances inside unknown weapons and optimize the verifiability of the state of the ammunition, was employed as an alternative method to overcome these limitations. The experimental system enabled quantitative and qualitative analyses of the internal chemicals by analyzing the time difference in acquiring the signals, particularly when the results indicate that the internal substance is a liquid. The results of this study can serve as a basis for advancing the application of ultrasonic testing as a viable and efficient approach for managing unknown weapons.

Baseline offset correction technique for terahertz signals based on improved wavelet multiresolution analysis

During the terahertz nondestructive testing of bonded structures, the incomplete discharge of the capacitance in the photoconductive antenna within the terahertz time-domain spectroscopy system results in a shift of the terahertz baseline produced by the antenna. This baseline shift causes variations in the amplitude information of the detected signals. Consequently, when feature imaging of the detection waveforms is performed, the baseline shift can lead to erroneous detection results. In this study, an improved wavelet multiresolution analysis method was used to eliminate high-frequency noise and baseline offset in terahertz detection. The method is based on the frequency characteristics of the detection waveforms, setting thresholds and using similarity as a measurement standard to determine the number of decomposition layers. Ultimately, this achieves the correction of the baseline offset in terahertz signals. Compared with other baseline correction methods, the method presented in this paper achieves the lowest root mean square error of 0.57%, the highest signal-to-noise ratio of 12.64%, and a defect identification accuracy of 96.27% in two-dimensional visualization results.

Evaluation of Residual Stress in Stir-squeeze Cast Aluminium – Fly Ash Composites Using X-Ray Diffraction Method

Determination of residual stresses in metals, subjected to secondary processing, is necessary from the point of view of their applications and is widely studied in literature. However, residual stresses induced during service is generally ignored when evaluating the performance of the component. The residual stress in a component could be tensile or compressive in nature and eventually affects its service life under external loading. In this regard, industries demand rapid, efficient, and easier methods of non-destructive testing to identify and control the residual stress in such components. The present work aims at evaluation of residual stress in an LM-25 aluminium alloy/fly Ash Metal Matrix Composites (AMC) after subjecting the specimen to dry sliding wear tests. X-ray diffraction technique was used to measure the residual stress in the “pin” specimen of the pin-on-disc set-up. The residual stress was ~ 24 % higher in the composite compared to the un-reinforced alloy after the wear test while the wear rate, measured in terms of weight loss of the pin, was lower by about 50%, under similar test conditions.

Study of the State Primary Measurement Standard of the Unit of Phase Shift Angle Between Two Voltages

Phase measurements are necessary for determining main parameters of the oscillatory process in complex electrical networks. Most often, it is precisely the phase shift angle (PSA) between two oscillatory processes of the same frequency that is measured. An essential indicator of the quality of electrical energy is the coefficient of asymmetry in a three-phase electrical network, which depends on the load of consumers in this network. This indicator is affected by a short circuit between two phase voltages. Phase measurement standards, phase meters, and phase converters are included in the measuring equipment for phase measurements. They are widely used in such fields as radiolocation, radio navigation, non-destructive testing, radio engineering, telecommunications, acoustics, metallurgy, machine and aircraft industry, space industry, as well as in scientific research and defence. The State Measurement Standard of Ukraine of the PSA unit between two voltages in the frequency range from 0.01 Hz to 10 MHz is maintained at the State Enterprise “UKRMETRTESTSTANDARD”, Kyiv. It provides metrological traceability of phases measured in the country. The main components of the standard were calibrated at the PTB, the National Metrology Institute of Germany. In Ukraine, numerous measurement standards and measurement instruments for phase measurements (more than 500.000 units) are used, in particular, phase calibrators, phase meters, phase shifters, synchronoscopes etc. Regular study of metrological characteristics of the DETU 09-07-11 measurement standard is conducted both in the main (from 5 Hz to 200 kHz) and in the extended (from 0.01 Hz to 10 MHz) frequency range. The PSA values obtained as a result of the research in the main frequency range do not exceed 0.001° (which is maximum according to measurements at all calibration points 0.00015°), and in the extended frequency range – 0.01° (which is maximum according to measurements at all calibration points 0.0053°). To eliminate the systematic measurement uncertainty component of the phase measurement standard, a special calibration is regularly performed using a set of resistive and capacitive phase bridges.

Study of Structural Defects Evolution in Fine-Grained Concrete Using Computed Tomography Methods

Introduction. When studying composite materials for construction purposes, it is needed to consider the mechanisms of formation of the structure and properties of modern concretes in the process of strength development. In studies of modern composite materials based on cement binder, there is no information about the development of structural defects and destruction of the material at the initial stages of strength development. This information can be obtained using X-ray computed tomography, a promising method of nondestructive testing of the state of the material. Therefore, the objective of this work was to study the formation and propagation of cracks in samples of fine-grained concrete with different fractional composition of sand due to natural processes of cement shrinkage, as well as the mechanics of destruction of samples of modified fine-grained concrete when applying a compressive load at the early stages of strength development. Materials and Methods. The study used fine-grained concrete mixtures of three compositions with different sand gradation. The tomography samples were made by placing fresh mixtures in polymer cylindrical containers. Tomography of the samples immediately after manufacture, as well as after 8 and 51 days, was performed in a YXLON Cheetah microfocus X-ray machine. The composition with two-fraction sand was modified by mechanical activation of the components, 20×20×20 mm cube samples were made. Further, compression tests were performed at the Instron installation after 3 and 7.5 hours, and then — tomography of the destroyed samples.Results. It was established that the destruction of contact zones depended on the ratio of the size of the fractions. In the presence of a bulk of coarse sand grains in concrete, the destruction of contact zones was more pronounced and had a main mode. When using fine or polyfraction sand, contact zones were destroyed locally and had a visually smaller area. The images of the destroyed modified sample, tested 3 hours after manufacturing, showed clear cracks and indents on the edges, which indicated the elastic-plastic nature of the destruction. In 7.5 hours, the edges of the sample upon destruction were covered with a network of small cracks; inside the sample there were also numerous cracks and microcracks, which indicated brittle fracture. Based on the obtained images of the deformed structure of modified concrete, the mechanism of transition from elastic-plastic destruction of the material to brittle one was clearly visible.Discussion and Conclusion. The studied dependences of the influence of the size of fine aggregate on the mechanisms of formation and propagation of structural defects contribute to the theory of the processes of destruction of fine-grained concretes. The results obtained prove the prospects of using X-ray computed tomography as a method of nondestructive testing of the internal structure of fine-grained concrete, including at the early stages of strength development.

Design of eddy current and capacitance dual-mode sensor for thickness detection of thermal barrier coatings

Abstract Thermal barrier coatings (TBCs) can markedly enhance the service temperature of high-temperature alloys, thereby enhancing the engine thrust-to-weight ratio. However, TBCs must be capable of withstanding a multitude of harsh environments, including high temperatures, high pressures, and high-speed particle impacts, which can potentially lead to damage and failure. Consequently, nondestructive testing of TBCs is of particular importance for the assessment of structural health. As eddy current detection is applicable to conductive materials and capacitive detection is applicable to non-conductive materials, this paper proposes a novel, eddy current/capacitance detection, dual-mode sensor, which combines the advantages of the two detection modes. This study examines the structural configuration and excitation characteristics of the eddy current and capacitance dual-mode sensor. Furthermore, the interaction between the capacitive electrode and the eddy current coil is examined, and the viability of the dual-mode sensor is demonstrated through experimentation. The experimental results demonstrate that the dual-mode sensor exhibits a sensitivity of 2.67 mΩ mm−1 for bond coating thickness detection in eddy current mode with an excitation frequency of 5 MHz, and a maximum sensitivity of 80.31 pF mm−1 for top coating thickness detection in capacitive mode.

Mechanical Characterisation of Gypsum-Based Passive Fire Protection Mortars with Micro and Nano Silica Particles

Steel structures are vulnerable to fire due to the degradation of their mechanical properties at high temperatures, making it necessary to protect them when exposed to high temperatures. This paper presents the results of an experimental research work to characterise the mechanical properties of gypsum-based fire-resistant mortars with and without nano and micro silica particles by destructive and non-destructive tests at ambient temperature. Five compositions were studied: one commercial composition was used as a reference and four were developed in the laboratory. Two were based on gypsum with perlite or vermiculite, and the other two included nano and micro silica particles. Twenty specimens underwent ultrasonic pulse velocity, flexural, and compression tests, while five specimens were tested by the impulse excitation of vibration. Young’s modulus, shear modulus, and Poisson’s ratio were assessed by non-destructive tests, and the flexural and compression strengths were assessed by destructive tests. Additional tests included density and porosity assessments, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Results indicated that adding nano and micro silica particles posed challenges to the mechanical and physical properties. Despite this, vermiculite compositions showcased superior or similar properties to the commercial composition, while perlite compositions exhibited slightly lower properties.