Ultrasonic Testing Technique Research Articles

Characterization and Degradation of Ancient Architectural Red Sandstone in a Natural Erosion Environment

The properties and appearance of ancient architectural red sandstone will be damaged after being eroded by the natural environment for a long time. In order to investigate the weathering and erosion characteristics of the red sandstone structure of an existing ancient building, ultrasonic testing techniques, combined with scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray computed tomography (X-CT), were used to analyze a building in Ganzhou. The variation in chemical substances contained in the red sandstone specimens according to phenology was analyzed by X-ray diffraction (XRD). The characteristic parameters of the CT grayscale images of the red sandstone were extracted and combined with the ultrasonic wave velocity values to comprehensively analyze the degradation characteristics of the red sandstone specimens, and a method to characterize the degradation degree of the red sandstone as a whole plane is proposed. We use the gray model (GM (1, 1)) to predict the surface degradation degree of red sandstone specimens, and gray relation analysis (GRA) to further analyze the correlation between the characteristic parameters of CT grayscale images of red sandstone and its degradation degree. The results show that in the natural erosion environment, dolomite and chlorite are generated on the exposed surface of the red sandstone, which can protect the internal sandstone to a certain extent. The degradation degree of the red sandstone specimens in the horizontal X and Y directions varies, and the proposed method of calculating the overall plane degradation degree of the red sandstone is feasible. The minimum average relative error of the surface degradation degree obtained from the gray prediction GM (1, 1) model is 1.4591%. There is a good correlation between the characteristic parameters of the red sandstone CT grayscale images and the degradation degree.

Noncontact nondestructive ultrasonic techniques for manufacturing defects monitoring in composites: a review

Composite materials are widely used in most industries due to their high specific strength, specific stiffness, and their relatively lighter weight compared to other traditional materials. However, the presence of defects arising from manufacturing processes or during service loads can make these structures more susceptible to a diminished performance. Furthermore, the former defects are inevitable in composite structures, but they can be reduced. Each type of defect requires specific inspection techniques and configurations. In this work, a review of the different types of composites manufacturing processes and their corresponding resultant defects is presented with the various nondestructive evaluation techniques employed for these defects’ characterization. The emphasis of this paper is on ultrasonic inspection and detection techniques for they present high sensitivity to surface/subsurface discontinuities, superior depth of ultrasonic penetration for flaw detection, feasibility on large scales, and instantaneous and detailed images production. Notably, noncontact ultrasonic testing techniques are also reviewed, air-coupled techniques in specific, and highlighted as a fine alternative to conventional contact inspection systems as they reduce the restrictions that coexist with the use of couplants. Moreover, these ultrasonic testing techniques are summarized to show the latest research progress achieved in the field of air-coupled ultrasonic inspection systems for manufacturing defects’ monitoring in composite structures including delamination, porosity, dryness, waviness, and resin lack/excess. Finally, we highlight the type and central frequency of the transducers and experimental results present in literature and obtained in terms of both detection and size of the defects.

Quality verification of Cold spray protection of the weld root

Cold spray technology (CS) as an advanced surface treatment can also be applied in the field of energy. Depending on the type of spraying, the coating itself plays the role of protecting the surface from corrosion, abrasion and other operational influences. In the case of dissimilar metal welds (DMW), it can play the role of protection against stress corrosion cracking (SCC). The thickness of the applied spray can range from tens of microns to units of mm. The quality of NiCr and Ni protective coatings made by CS technology was tested by means of non-destructive (NDT) and destructive (DT) testing. NDT focused on measuring the attenuation of the ultrasonic signal, measuring the thickness of the applied coatings and the adhesion to the base material using pulsed echo (PEUT) and phased array (PAUT) ultrasonic testing techniques. Evaluation of the microstructure, porosity and corrosion stability of CS coatings before and after the salt spray test was performed metallographically.

Locating cracks in isotropic plates using nonlinear guided waves

Guided waves are gaining popularity in the NDT (Nondestructive Testing) industry due to their potential for cost and time savings when inspecting structures and their high sensitivity in detecting micro-defects over large areas. Cracks caused by various issues are one of the most common causes of material failure, severely affecting the structure’s durability and serviceability. The significance of small cracks may vary across different applications. As a result, detecting and classifying damages is a challenging process limited by the current detection techniques. This makes the damage detection process challenging and sets the limit on the range of damage detection techniques that can be used. This study uses experimental and numerical approaches for detecting and locating cracks in isotropic plates using the second harmonic of the symmetric guided wave (S0) induced by cracks. This article analyzes a range of numerical models with varying orientations and dimensions. The second harmonic of the (S0) guided wave is used for detecting and locating the crack. The results show that the second harmonic of the (S0) guided wave induced by crack can detect and locate cracks in plates. The proposed technique is accurate, reliable, and does not require baseline data, providing an advantage over conventional ultrasonic testing techniques.

Energy Transfer Efficiency Based Nonlinear Ultrasonic Testing Technique for Debonding Defects of Aluminum Alloy Foam Sandwich Panels

In order to improve the accuracy of detection results of debonding defects of aluminum alloy thin plate, the nonlinear ultrasonic technology is used to detect the simulated defect samples, aiming at problems such as near surface blind region caused by the interaction of incident wave, reflected wave and even second harmonic wave in a short time due to the small thickness of thin plates. An integral method based on energy transfer efficiency is proposed to calculate the nonlinear ultrasonic coefficient to characterize the debonding defects of thin plates. A series of simulated debonding defects of different sizes were made using aluminum alloy plates with four thicknesses of 1 mm, 2 mm, 3 mm and 10 mm. By comparing the traditional nonlinear coefficient with the integral nonlinear coefficient proposed in this paper, it is verified that both methods can quantitatively characterize the size of debonding defects. The nonlinear ultrasonic testing technology based on energy transfer efficiency has higher testing accuracy for thin plates.

Internal defect detection and characterization of samarium-cobalt sintered magnets by ultrasonic testing technique

Excessive quantities of samarium-cobalt (Sm-Co) magnet material are being scrapped needlessly due to a lack of understanding of inhomogeneity distribution and unacceptable internal defects. If there is a way to identify, locate, characterize and when needed separate the defective portions of magnet material, utilization can be increased and product quality improved. Further, the magnets’ magnetic and mechanical performance can be improved by reducing the occurrence of internal defects. This paper reports on a cost-effective and efficient nondestructive evaluation method based on an ultrasonic testing (UT) technique applied for detecting and characterizing internal defects in Sm-Co sintered magnets. Applying the UT technique will allow users to comprehensively analyze internal defects, such as inclusions, porosity, microcracks, and other structural irregularities, check for homogeneity and anomalous regions and give the locations of these internal anomalies and defects within the Sm-Co sintered magnets. The UT technique can also be applied to other rare-earth permanent magnets, such as sintered or die-upset neodymium-iron-boron (Nd-Fe-B) magnets. The UT technique can effectively guide quality control and acceptable product selection, in addition to optimizing the magnet alloy design and production processes. Thus, it can facilitate the improvement of magnet manufacturing efficiency and machinability, reduce scrap, prolong service life, increase the use of what would be post-production waste, and enhance product reuse and recycling at end-of-life disposition.

Acoustic Path Filtering for Improved Multimode Total Focusing Method Inspection

Total focusing method (TFM) is an ultrasonic testing (UT) technique that provides nondestructive testing (NDT) inspectors with new imaging modes, enabling more accurate detection, sizing, and representation of challenging defects. While TFM may offer convenient, nearly true-to-geometry imagery as the inspection result, it is often detrimentally affected by mode conversion artifacts. Current standards, such as ASME Section V, place the burden on the inspector to explain the origins of those artifacts, impacting the productivity and reliability of the inspection. A method enabling direct control of the ultrasonic wave propagation modes—that is, transverse wave (T) or longitudinal wave (L)—through each interface of the acoustic path is proposed and evaluated in this paper. This control is achieved after the full matrix capture acquisition by modulating, according to the desired propagation mode, the gain applied on the individual paths within the summation process. This leads to the formation of a Path-Filtered Total Focusing Method image. Empirical results on various use cases show considerable improvement of the signal-to-noise ratio through the almost complete elimination of signals originating from undesired paths.

Dual-tandem phased array method for imaging of near-vertical defects in narrow-gap welds

Near-vertical flaws in thick-section narrow-gap welds are notoriously difficult to detect and size using traditional Phased Array Ultrasonic Testing (PAUT) techniques. Self-tandem shear inspection has been considered for detection but lacks appropriate full weld sensitivity. The dual-tandem phased array inspection method is proposed to enable multi-mode Total Focusing Method (TFM) pulse-echo imaging with longitudinal through-transmission inspection, by introducing a second, opposite-facing probe on the far weld side. Pulse-echo and through-transmission datasets are obtained in a single Full Matrix Capture (FMC) acquisition, for each weld side. Analysis of the optimum Probe Centre Spacing (PCS) based upon image sensitivity suggests that a spacing corresponding to a longitudinal beam crossover at 2/3 sample thickness provides greatest weld coverage. Testing on near-vertical EDM notches in a 120 mm thick mock narrow-gap carbon steel sample has shown high sensitivity TFM imaging, at notch depths of 27.5 mm, 60 mm and 92.5 mm. Pitch-catch through-weld transmission imaging has exhibited tip-diffraction images with a Signal-to-Noise Ratio (SNR) of up to 17.3 dB. Pulse-echo imaging using multi-mode TFM has shown tip-diffraction and reflection with up to 19.2 dB and 34.8 dB SNR respectively. The possibility of image mixing by considering image defect response type has provided full 2D notch reconstruction. These results demonstrate the strength of the dual-tandem method in enhancing the detection reliability and detection of near-vertical defects in thick-section narrow-gap welds.

Effect of thermal fatigue on mechanical properties and microstructure of concrete in constant ambient humidity

The daily and annual temperature differences in mid and high latitudes areas vary greatly, which leads to thermal fatigue deterioration of concrete. The deterioration of concrete properties can also be generated by the cyclic change of humidity in concrete. In the experiment, the thermal fatigue tests of concrete with two strength grades were carried out at the temperature difference of 20 °C, 30 °C, and 40 °C (the initial temperature is 20 °C) under the condition of constant ambient humidity. The macroscopic properties change of concrete such as compressive strength and splitting tensile strength were measured. The microstructure changes of concrete were determined by ultrasonic nondestructive testing technique and mercury intrusion test. The results indicated that thermal fatigue has obvious deterioration effect on concrete. With the increase of temperature difference and cycle number, the strength of concrete decreased dramatically and the decrease of C40 concrete was greater than that of C25 concrete. The splitting tensile strength was more sensitive to thermal fatigue than compressive strength. The ultrasonic wave velocity gradually decreased and the damage factor increased, indicating the internal crack defects of concrete increased. At the same temperature difference, the porosity, total pore volume, average pore diameter, medium pore diameter, and the most probable pore diameter of concrete increased gradually with the increase of the cycle number, while the total pore surface area decreased. The pore structure showed the characteristics of coarsening and the trend of deterioration. The porosity of C40 concrete was less than that of C25 concrete, but the relative change value of porosity was larger, which reveals the internal reason for the strength damage of concrete under thermal fatigue at the microscopic level.

Underwater Inspection of Highway Bridges - Recent Trends and Technologies

Underwater engineering evaluations of transportation assets have historically relied largely upon conventional, crewed commercial diving operations, using visual testing (VT) and tactile examination methods to detect surface discontinuities and evaluate site conditions. In practical application, this approach alone is often found to be suboptimal, due to multiple challenges inherent in conducting inspections in the underwater environment. Modern underwater inspections are increasingly reliant upon new technologies, and nondestructive testing methods beyond VT are used during conventional diving inspection to gain a broader picture of the asset and its condition, increasing efficiency while lowering risk in the process. Underwater engineering inspectors today employ traditional nondestructive technologies, including VT, ultrasonic testing (UT), and magnetic particle testing (MT) techniques, in concert with acoustic (sonar) imaging techniques and remotely operated vehicles (ROVs) to obtain more detailed information about the asset and adjacent waterway conditions. This approach enhances the inspection’s safety and efficiency and reduces risk to the bridge owner and end user. This article discusses today’s underwater bridge inspection approach, emphasizing the NDT technologies utilized and their benefits.

Ultrasonic non-destructive evaluation of composites: A review

Ultrasonics is an NDT (Non-Destructive Testing) technique used to detect faults in structural components by applying a set of techniques and classifying them accordingly. This paper aims to bring together the most relevant published work on different types of techniques for Non-Destructive Evaluation (NDE) of various defects using Ultrasonic. The Ultrasonic testing techniques are relatively simple, highly sensitive and less time-consuming hence have been approved for use on various domains like composite testing, aerospace, automotive and transport. The fundamentals, their applications and constraints of various techniques are covered, along with motions to assess the performance of the techniques. Ultrasonic testing became popular, and with the progress made, new methods were discovered and corrected which resulted in defect detection and improving various material properties.

A novel two-level approach to defect detection in braided CFRP using air-coupled ultrasonic testing

Air-coupled ultrasonic testing and C-scan technique has been increasingly applied to the braided CFRP structures owing to its non-destruction, non-contact and high visualization characteristics. Due to the noise, structural vibration, and airflow in the process of detection, the accuracy of defect identification is easily deteriorated. To address this issue and further determine the relationship between the ultrasonic acoustical pressure attenuation and structural parameters, a novel two-level identification method based on the modified two-dimensional variational mode decomposition (2D-VMD) has been proposed. In the first level, C-scan images have been sparsely decomposed into ensembles of modes by 2D-VMD method. Then, the modes have been screened by mutual information method to realize the reconstruction of new image in the second level. Experimental results have shown that the proposed method has the good ability to identify defects with a minimum detectable diameter of 1–2 mm. It has been noted that the ultrasonic acoustical pressure attenuation has become remarkably higher in the twill weave CFRP than the plain weave CFRP and the ratio of pressure attenuation between two weave types of CFRP has decreased with the defect depth increase. Meanwhile, shadows around defects in C-scan images have been suppressed to a great extent. It has been demonstrated that the capability of denoising has enabled the developed method with the accurate detection in terms of the shape, size, depth and weave type. With these advantages, the proposed method has provided valuable insights into the development of an effective method for defect detection of braided CFRP structures.

In-Motion Railroad Tie Deflection Measurement via Ultrasonic Airborne Sonar and Computer Vision Techniques

ABSTRACT It is known in the railroad maintenance engineering community that the deflection of railroad ties is an indicator of the quality of the tie–ballast interface, whose deterioration may cause dangerous train derailments. A new technology is proposed to reconstruct the full-field deflection profile of railroad ties in-motion by means of non-contact ultrasonic testing and computer vision techniques. The sensing layout consists of an array of air-coupled capacitive transducers (operated in pulse-echo sonar-based ranging mode) and a high frame-rate camera, rigidly connected to the main frame of a moving train car. The acquisition system is programmed such that the synchronized waveforms and images are collected and saved as train car moves. In the processing stage, a supervised machine learning-based image classification approach is developed to demarcate the tie boundaries. For this purpose, the Speeded-Up Robust Features (SURF) and Bag of Visual Words (BOVW) algorithms are employed to encode images into condensed feature vectors, which are subsequently fed into the Support Vector Machine (SVM) to train a classifier. The relative deflections of the identified ties are eventually computed by tracking the time-of-flight of the reflected waves from the surfaces flagged as tie. An image processing technique is also developed to estimate the spatial resolution of the tracking system, required to reconstruct the full-field deflection profile of the scanned ties. The importance of such a technique is stressed if the test run is performed without any dedicated positioning system. The proposed ‘tie sonar’ system was prototyped and used to reconstruct the deflection profile of the ties scanned during a series of test runs conducted at slow (walking) speed at the Rail Defect Testing Facility (RDTF) of UC San Diego as well as a BNSF yard in San Diego, CA, with a realistic train load. Further developments of this system should include a performance evaluation at higher speeds (e.g., revenue speed).

Ultrasonic and phased-array inspection in titanium-based alloys: A review

Ultrasonic testing procedures are among the most extensively used techniques in non-destructive testing and non-destructive evaluation systems. Meanwhile, phased array inspection or phased-array ultrasonic testing techniques as a well-known type of ultrasonic testing in advanced non-destructive testing systems are utilized in numerous applications, including oil and gas, medical imaging applications, railway, automotive, marine, and aviation industries. Phased-array ultrasonic testing-based methods can also be used in a variety of weld inspections, bond testing, thickness profiling, flaw detections, corrosion inspections, and in-service crack detection. The rapidity, safety, easiness, affordable price, and accurate visualization of phased array in measuring the defect characteristics such as size, shape, depth, and orientation allow its wide usage and even as a substitute for other inspection methods like radiographic methods. In phased array methods, more than one sound wave is employed to enhance the reliability and flexibility of inspection through the operation of several transducer assemblies, involving 16 to 256 small individual elements. Titanium having many desirable properties like high strength to weight ratio found many industrial applications, which highly necessitates its persistent inspection. For this aim, the present study focuses on the application of the phased-array ultrasonic testing technique for inspecting Ti components specifically in additive manufacturing, welding inspections, and defect detection of complex geometries and composites. Moreover, modern applications and improved computation methods are discussed. The development of phased-array ultrasonic testing inspection systems, particularly high throughput and efficient in situ and mobile equipment, and new computation methods will open new horizons toward the highly sophisticated inspection procedures.

Ultrasonic monitoring of the VVER-1000 FA form change

A procedure has been developed to determine the geometrical parameters of fuel assemblies (FA) by an ultrasonic pulse-echo technique used for all types of light-water reactor FAs. The measurement of geometrical parameters is achieved through the pairwise installation of ultrasonic transducers opposite the FA spacer grid faces at a distance of not more than a half of the transducer acoustic field near-region length such that the acoustic axes of the pairwise transducers are parallel to each other. The advantages of the presented technique is that it enables monitoring of any FA modifications, including the VVER reactor assemblies with a different number of spacer grids. The paper presents a mathematical model of the acoustic path developed in a geometrical acoustics approximation and its verification results. The model was used for computational and experimental studies of the ultrasonic test technique, and engineering formulas have been developed to calculate the errors of the transducer-measured distance to the FA surface. A code has been developed to simulate the FA form change monitoring and can be used to design new monitoring systems. The developed technique to determine the VVER-1000 FA geometrical parameters was introduced at units 1 and 2 of the Temelin NPP, the Czech Republic, for the TVSA-T FA form change monitoring. The successful use of the proposed technique makes it possible to recommend it for use in inspection benches at other NPPs.

Simulation-Based Investigation of a Probability of Detection (POD) Model Using Phased Array Ultrasonic Testing (PAUT) Technique

Probability of detection (POD) as a metric for quantifying the capability of inspection procedures in nondestructive evaluation (NDE), has been applied and evolved in industries since 1970s. Progress had been noted when certain statistical functions were brought up to model POD behavior, including log-normal model (also referred as Probit model). This model had been concluded to be the best fit and therefore has been widely used in many studies, while the involved assumptions and conditions were not carefully addressed and explored. To make flexible POD datasets available for specific inspection procedures and reduce the number of expensive experiments needed, model-assisted POD (MAPOD) is an alternative. This paper addresses a pure simulation-based POD procedure of an inspection scenario involving phased array ultrasonic testing (PAUT) on lack-of-fusion defects in additive manufactured (AM) components. The mathematical simulations are performed by an ultrasonic testing (UT) simulation software, simSUNDT, developed at Chalmers University of Technology in Sweden. Resulted inspection datasets with the proposed data processing steps are evaluated in terms of the assumptions and conditions of log-normal POD model, with the purpose of discussing the POD model validity under different circumstances. Simulation-based POD curves are finally compared with several discrete POD values at some defect sizes, calculated through massive computations from physics-model based metamodel. Comparisons and observations confirm satisfactory application of log-normal POD model despite some violations in model hypotheses.

TA15 and inconel 625 bimetallic structures additive manufacturing and phased array ultrasonic testing

Additive manufacturing of bimetallic structures has become a hotspot in recent years. However, the interfaces of bimetallic structures are always the weaknesses, and cracks always occur at the interfaces. Three bimetallic samples of TA15 and Inconel 625 were manufactured by laser metal deposition, and the effect of laser power on the manufacturing quality was analyzed. Then phased array ultrasonic testing (PAUT) technique was applied for crack detection for the three samples, and metallographic analysis was employed to verify detection results. The results showed that the increase of laser power can eliminate macro-cracks at the interface of the bimetallic sample, and micro-cracks at the interface can be detected by PAUT.

Fatigue properties of wood at different load ratios tested at 50 Hz and 20 kHz

AbstractFatigue properties of sycamore maple (Acer pseudoplatanus) under cyclic tension, cyclic compression and tension‐compression loading at 50 Hz are investigated. Furthermore, for the first time, fatigue test results of wood generated with the ultrasonic fatigue testing technique at 20 kHz under tension‐compression loading are presented. Cyclic properties are in line with the static properties – with the tensile strength being more than two times the compressive strength. Mean lifetimes of 106 cycles are found if the maximum tensile stress for cyclic tension is 69 %±8 % of the tensile strength and if the maximum compressive stresses for cyclic compression and tension‐compression are 75 %±7 % and 54 %±4 % of the compressive strength, respectively. Tension‐compression loading at 20 kHz delivers lifetimes comparable to servo‐hydraulic tests at 50 Hz, and no pronounced frequency effect on fatigue lifetime is found. Ultrasonic fatigue testing is therefore, in principle, appropriate for accelerated fatigue testing of wood up to the very high cycle fatigue regime. Tests up to 109 cycles show no evidence of a fatigue limit for sycamore maple.

Discrimination of Poor Electrode Junctions within Lithium-Ion Batteries by Ultrasonic Measurement and Deep Learning

Lithium-ion batteries, which have high energy density, are the most suitable batteries for use in high-tech electromechanical applications requiring high performance. Because one of the important components that determines the efficiency of lithium-ion batteries is the electrode, the manufacturing process for this junction plays an important role in the entire production process. In particular, the process related to the resistance spot welding of the electrode is very important, directly affecting the safety of users, and greatly affecting the performance of the batteries. However, because the electrode tab is spot-welded onto the inner surface of the case, it is impossible to verify with visual testing (using the naked eye) whether the junction is well bonded. Therefore, it is very important to perform quality evaluation of the resistance welding of electrodes after completing the manufacturing process, using non-destructive testing methods. In this paper, a non-destructive ultrasonic testing technique was applied to examine the quality of lithium-ion batteries in which the negative electrode tabs were welded to the inner surface of the cell cans. The status of resistance spot welding between the electrode and the can was verified using deep-learning techniques with the experimentally acquired ultrasonic signal database.

Internal Defect Detection and Characterization of Sm-Co Sintered Magnetsby Ultrasonic Testing Technique

Internal Defect Detection and Characterization of Sm-Co Sintered Magnetsby Ultrasonic Testing Technique