Showing papers on "Ultrasonic testing published in 2023"

Research Progress in Nonlinear Ultrasonic Testing for Early Damage in Metal Materials

Abstract: There are some limitations when conventional ultrasonic testing methods are used for testing early damage in metal parts. With the continuous development of acoustics and materials science, nonlinear ultrasonic nondestructive testing technology has been used for testing of early damage in metal materials. In order to better understand the basic theory and research progress of the nonlinear ultrasonic testing technology, the classical nonlinear ultrasonic theoretical models, including the dislocation monopole model, dislocation dipole model, precipitate-dislocation pinning model, and contact nonlinear ultrasonic theory-microcrack model, are analyzed in depth. This paper introduces the application and research progress of nonlinear ultrasonic detection technology, which is derived from different acoustic nonlinear effects, such as higher harmonic, wave mixing and modulation, sub-harmonic, resonance frequency spectrum analysis, and non-linear ultrasonic phased array imaging. The key technologies and problems are summarized to provide a reference for the further development and promotion of nonlinear ultrasonic non-destructive testing technology.

Automatic defect depth estimation for ultrasonic testing in carbon fiber reinforced composites using deep learning

Abstract: Ultrasonic testing (UT) is commonly used to inspect the geometric shape of internal damage in composite materials and the test results need to be interpreted by trained experts. In this work, an automatic signal classification method based on deep learning is proposed for depth estimation of the detects introduced by low-velocity impact (LVI) in carbon fiber reinforced plastics (CFRPs). Three kinds of neural networks, LSTM, CNN, and CNN-LSTM are used to analyze the attributes with different depths. Then, trained models are applied to identify the depth information of impact damage. The results show that the CNN-LSTM model is a more accurate in-depth classification for LVI defects in CFRP based on A-scan signals than the other two structures.

Assessment of Laser-Generated Ultrasonic Total Focusing Method for Battery Cell Foil Weld Inspection

Abstract: ABSTRACT The feasibility of using laser-generated ultrasonic Total Focusing Method (TFM) was assessed for guided ultrasonic waves in finite plates. The application under consideration is for inspection of ultrasonically welded battery tab-to-electrode foil stack joints. The testing constraints for this weld necessitate couplant-free, remote, guided-wave conditions making laser ultrasonic TFM an ideal inspection technique. It was determined that laser-generated guided wave TFM can be used to remotely assess defects in a finite plate when the defects are strong reflectors in the plane of wave propagation. The finite dimensions of the tab require a strong understanding of the edge reflection effects on the TFM image. The guided wave modes used in this study were strongly affected by scattering due to the complex weld geometry, which most resembles that of a periodic triangular grated wave guide. Future work will investigate methods to compensate for the strong scattering/guided wave effects, the use of other guided wave geometries, out of plane TFM reconstruction for other weld defect types, as well as apodization effects.

A novel ultrasonic inspection method of the heat exchangers based on circumferential waves and deep neural networks

Abstract: The heat exchanger (HE) is an important component of almost every energy generation system. Periodic inspection of the HEs is particularly important to keep high efficiency of the entire system. In this paper, a novel ultrasonic water immersion inspection method is presented based on circumferential wave (CW) propagation to detect defective HE. Thin patch-type piezoelectric elements with multiple resonance frequencies were adopted for the ultrasonic inspection of narrow-spaced HE in an immersion test. Water-filled HE was used to simulate defective HE because water is the most reliable indicator of the defect. The HE will leak water no matter what the defect pattern is. Furthermore, continuous wavelet transform (CWT) was used to investigate the received CW, and inverse CWT was applied to separate frequency bands corresponding to the thickness and lateral resonance modes of the piezoelectric element. Different arrangements of intact and leaky HE were tested with several pairs of thin piezoelectric patch probes in various instrumental setups. Also, direct waveforms in the water without HE were used as reference signals, to indicate instrumental gain and probe sensitivity. Moreover, all filtered CW corresponding to resonance modes together with the direct waveforms in the water were used to train the deep neural networks (DNNs). As a result, an automatic HE state classification method was obtained, and the accuracy of the applied DNN was estimated as 99.99%.

Nondestructive Inspection of Underwater Coating Layers Using Ultrasonic Lamb Waves

Abstract: Coatings play a crucial role in protecting ships and marine structures from corrosion and extending their service life. The reliability of these coatings depends on their proper maintenance, which in turn, relies on the application of reliable diagnostic techniques. Non-destructive testing (NDT) techniques are useful in material diagnostics, such as detecting debonded zone in water. However, the challenging access environment in the ocean, and the high attenuation characteristics of the material itself add too many technical challenges. In this paper, we propose a guided wave-based technique for characterizing the bonded zone state of coatings, which uses FFT analysis in different bonded zone states. The proposed technique has been demonstrated to be effective in characterizing the bonded zone state of water coatings through numerical and experimental results.

Sizing-Based Flaw Acceptability in Weldments Using Phased Array Ultrasonic Testing and Neural Networks

Abstract: Liquefied Natural Gas (LNG) is one of the major renewable energy sources and is stored and carried in a storage tank that is designed following international standards. Since LNG becomes highly unstable when it encounters oxygen in the air, a leakage from an LNG storage tank can cause a catastrophic industrial accident. Thus, the inspection of LNG storage tanks is one of the priorities to be completed before LNG is stored in a storage tank. Recently, the usage of Phased Array Ultrasonic Testing (PAUT) has been gradually increasing as the risks of RT emerge. PAUT has some obstacles to overcome in order to substitute RT, such as efficiency and accuracy. Specifically, the cost issue must be addressed. Therefore, many attempts to combine PAUT with Artificial Neural Networks (ANN) have been made. PAUT provides many types of 2D images of the inspected weldment. The S-scan is one of the 2D images provided by PAUT, and it displays the cross-sectional view of the specimen with a single transducer. The inspectors examine the S-scan image and other provided images of PAUT to detect, classify and size the flaw that exists in the weldment so that the decision of whether the inspected weldment with the flaw is acceptable can be made. Nowadays, most of the previous research on PAUT and ANN focuses on detecting and classifying the flaws in B-scan or S-scan images. However, the last step to determine the flaws’ acceptability is not yet covered. In this study, the flaw acceptance criteria of PAUT in various international standards are listed. EXTENDE CIVA is used to create the PAUT S-scan images. The S-scan images are labeled with the listed acceptance criteria. Then, they are used in Mask R-CNN training. After the training, some new S-scan images with flaws are used to test the performance, and this showed 96% precision and 87% recall. With the algorithm, the acceptability of a flaw in a weldment can be determined efficiently and it will reduce the burden of PAUT usage and reduce the time required for a full-length inspection.

Development and Investigation of High-Temperature Ultrasonic Measurement Transducers Resistant to Multiple Heating–Cooling Cycles

Abstract: Usually for non-destructive testing at high temperatures, ultrasonic transducers made of PZT and silver electrodes are used, but this could lead to damage to or malfunction of the ultrasonic transducer due to poor adhesion between PZT and silver. Soldering is one of the most common types of bonding used for individual parts of ultrasonic transducers (protector, backing, matching layer, etc.), but silver should be protected using additional metal layers (copper) due to its solubility in solder. A mathematical modelling could help to predict if an ultrasonic transducer was manufactured well and if it could operate up to 225 °C. The observed von Mises stresses were very high and concentrated in metal layers (silver and copper), which could lead to disbonding under long-term cyclic temperature loads. This paper presents a multilayer ultrasonic transducer (PZT, silver electrodes, copper layers, backing), which was heated evenly from room temperature to 225 °C and then cooled down. In the B-scan, it was observed that the amplitude of the reflected signal from the bottom of the sample decreased with an increase in temperature. However, after six heating–cooling cycles, the results repeated themselves and no signs of fatigue were noticed. This ultrasonic transducer was well manufactured and could be used for non-destructive testing when the environment temperature changes in cycles up to 225 °C.

Double piezoelectric defects in phononic crystals for ultrasonic transducers

Abstract: Significant prior research has explored elastic wave-energy localization via defect modes of phononic crystals (PnCs). The integration of defect-introduced PnCs and piezoelectric materials has paved the way for the development of new conceptual products for applications in energy harvesters, wave filters, and ultrasonic sensors. Recently, an attempt has been made to deviate from this paradigm and design an ultrasonic transducer that generates elastic waves. Unfortunately, previous work has been limited to a single-defect situation. Therefore, as an advanced approach, the present work aims to expand the PnC design space into double defects, which will make ultrasonic transducers useful at several frequencies. As a first step, this study targets longitudinal wave generation. To predict the wave-generation performance, a previous analytical model that was built for energy-harvesting purposes under a single-defect situation is modified to be suitable for the present wave-generation purpose under a double-defect situation. Moreover, two parametric studies are executed to analyze how the output responses change based on changes to the input voltage setting and the spacing between the double defects. We hope that these ultrasonic transducers could be potentially applicable for nondestructive testing in structural health monitoring and ultrasonic imaging in medical science.

Imaging Concrete Structures with Ultrasonic Shear Waves—Technology Development and Demonstration of Capabilities

Abstract: Since 1987 when dry-point-contact (DPC) transducers were invented in the USSR, ultrasonic shear wave devices based on those transducers have been commercialized and have become one of the most effective technologies for imaging concrete. That said, the objectives of this paper are (1) to provide a brief review of the historical development of these powerful devices and (2) to provide a comprehensive assessment of their capabilities in imaging internal entities and structural defects. Regarding the former, the paper presents the context that gave birth to DPC technology and different generations of ultrasonic shear wave devices for concrete inspection. For the latter, one of the state-of-the-art ultrasonic shear wave devices (MIRA 3D) was used to collect data on concrete specimens with different built-in flaws/defects. Those data are then visualized with a commonly used data processing algorithm, the so-called synthetic aperture focusing technique (SAFT). Finally, based on the resulting images, the capabilities of the device are discussed in detail for each concrete imaging problem. A main limitation of ultrasonic shear wave technique for concrete inspection is that it requires a significant amount of time and effort for data collection.

Interaction analysis of different defects with laser ultrasonic sound waves and defect characterization

Abstract: The paper presented a novel approach for characterization of defects based on laser ultrasonic nondestructive testing. Both flat materials and curved materials are used as experimental samples, and crack-type defects and circular defects with different depths are applied as experimental objects. Through analyzing the interaction between different defects and acoustic waves, a novel characterization algorithm is proposed based on the energy loss theory to realize the characterization of defects. In more specific details, the defects are firstly scanned by laser ultrasonic test platform to obtain the wave field diagram. Then, the interaction between defects and the sound waves is analyzed, and the type of defects is determined based on the shape of the reflected waves. Finally, the interaction analysis and quantitative characterization are carried out through the reflection energy coefficient, and compared with other characterization methods. It was found that for circular defects in materials with different shapes, the reflection energy coefficient increases with the increases of defect depth. But for crack-type defects, when the depth is greater than 0.5 mm, the reflection energy coefficient increases first and then reaches a stable value. Through the study, not only the interaction between defects and sound waves is analyzed and verified, but also the proposed approach can be adopted for qualitative and quantitative characterization of defects.

Estimation of Flexural Strength of Plain Concrete from Ultrasonic Pulse Velocity

Abstract: The aim of this study is to propose mathematical expressions for estimation of the flexural strength of plain concrete members from ultrasonic pulse velocity (UPV) measurements. More than two hundredpieces of precast concrete kerb units were subjected to a scheduled test program. The tests were divided into two categories; non-destructive ultrasonic and bending or rupture tests. For each precast unit, direct and indirect (surface) ultrasonic pulses were subjected to the concrete media to measure their travel velocities. The results of the tests were mointered in two graphs so that two mathematical relationships can be drawn. Direct pulse velocity versus the flexural strength was given in the first relationship while the second equation describes the flexural strength as a function of indirect (surface) pulse velocity. The application of these equations may be extended to cover the assessment of flexural strength of constructed concrete kerb units or in-situ concreting kerbstone and any other precast concrete units. Finally, a relation between direct and indirect pulse velocities of the a given concrete was predicted and suggested to be employed in case when one of the velocities is notavailable can be measured for other ultrasonic pulse test applications

Design and test of a small high frequency ultrasonic cleaning transducer

Abstract: In order to solve the problem of cleaning of complex surfaces and micro blind holes in industrial products, a small high frequency ultrasonic cleaning transducer was designed and tested. Firstly, the finite element model of the transducer was established, and the influence of structural parameters on the first order longitudinal vibration frequency was analyzed. By adjusting the structural parameters of the transducer, the first order longitudinal vibration frequency of the transducer was determined to be 58716hz.The harmonic response of the transducer was analyzed. The results showed that when the voltage amplitude applied on the piezoelectric ceramic sheet was 80V, the transducer produced resonance at 58716 Hz, and the end face of the front cover of the transducer produced an axial displacement of about 3.34 µm . The transducer was made according to the theoretical analysis results, and the frequency sweep test was carried out on the transducer. The theoretical analysis results were consistent with the test results, which showed that the designed small high frequency ultrasonic cleaning transducer could meet the requirements of high frequency cleaning.

Increasing the efficiency of the surface-mounted ultrasonic electromagnetic-acoustic transducer on account of the magnetic field source

Abstract: Model studies were carried out using the COMSOL Multiphysics package, aimed at ensuring the forming of a permanent magnet magnetic field at a considerable distance to a ferromagnetic product from its pole, which is necessary to create efficient portable ultrasonic electromagnetic-acoustic transducers of thickness gauges and testing and diagnostic devices. It is theoretically shown and experimentally confirmed that for portable measuring ultrasonic devices it is expedient to set the height of the permanent magnet at about 60 mm and the cross section of the magnet pole 50x50 mm2. At the same time, with a gap between the magnet pole and the product of about 30 mm, the value of the normal component of the magnetic field induction near the surface of the object is about 0.3...0.4 T, which is sufficient for thickness gauging or diagnostics of ferromagnetic products using the ultrasonic pitch-and-catch method. References 19, figures 8.

Development and study of ultrasonic immersion testing system for industrial and metrological application

Abstract: Abstract Ultrasonic non-destructive testing (NDT) is one of the prominent field involving inspection to evaluate defects, cracks, deposition or fusion of welding materials and dimensional measurements of the test piece(s). Ultrasonic immersion scanning systems are useful for various industrial and metrological applications. The conventional immersion system uses a dedicated pulser receiver module for the excitation and detection of signal from transducer and a fast analog data acquisition card (DAQ) to acquire the raw data into computer. Rigorous digital signal processing and filtering is used to extract desired information from the raw data. In the present work, development of an ultrasonic immersion C-scan testing system, intended for industrial and metrological applications, is described. The developed system uses a commercial ultrasonic flaw detector (UFD) for the data acquisition rather than using pulser receiver and DAQ card to acquire ultrasonic information. The software for the same has been developed in Visual Basic .NET framework to control all five servo motor based axes of the ultrasonic immersion scanning tank. The developed software scans the sample automatically with parameters specified by the user. The parameters include echo amplitude, echo location, separation between two echoes, and ultrasonic attenuation. The developed software generates the data files that can later be used for further analysis using suitable data analysis software such as Origin or MS excel. The functionality of the developed system has been tested for the detection of flaws present in the material, testing for thickness variation and ultrasonic attenuation. The developed system is capable of detecting the location of defects within the resolution of ±0.01 mm. Ultrasonic transducer movement resolution of ±0.01 mm over the sample, results in to generation of a high quality image.

Study of the attenuation of ultrasonic oscilliations in 3D-orthogonal woven composite

Abstract: The particularities of 3D-woven composite’s defects are observed. Automated ultrasonic immersion through-transmission technique for their non-destructive testing is offered. X-ray computed tomography (X-ray CT) application for the definition of the reasons of ultrasonic waves high attenuation in 3D-orthogonal woven composite sample is described. The analysis of defects detected with X-ray CT is shown. The suggestion about connection between quantity of projection of defects total area at the plane which is perpendicular to ultrasonic wave propagation and ultrasonic wave attenuation has been made.

Comparison of Ultrasonic Phased Array and Film Radiography in Detection of Artificially Embedded Defects in Welded Plates

Abstract: Ultrasonic and radiographic testing are generally two basic methods for volumetric (internal) defect detection in non-destructive testing. Since both methods are commonly used for the same thing, the question arises as to whether both are equally capable of detecting some commonly occurring defects in manufacturing. Commonly occurring defects are generally considered to be fusion defects, drilled holes (which act as pores), etc. To prove or disprove the hypothesis that both methods can generally be used to detect these defects, an experiment was conducted using three welded plates with artificially inserted defects. The welded plates had multiple defects that were intentionally placed close to each other to further complicate the interpretation of the UT results. UT investigation was based on phased-array technology with a multi-element probe. RT investigation was performed with an X-ray machine. Both investigations were based on the respective European standards: for UT, EN ISO 17640, and for RT, EN ISO 17636-1. The results and conclusions from the experiment are presented in this paper.

Homogeneity of Bored Piles According to Results of Four-Channel Cross-Well Ultrasonic Monitoring

Abstract: The homogeneity of the structure of the boired pile shaft has been studied based on the results of four-channel inter-well ultrasonic (US) monitoring. The actual lengthy of the piles has been determined with the detection of defragmentation of the pile shaft, the compressive defects have been determined, and continuity defects have been identified based on a joint analysis of data from the method of interwell ultrasonic monitoring. The use of four channels allows to control separately the peripheral and central areas of the pile in six directions. The data of the seismoacoustic method coincided with the parameters of ultrasonic monitoring in terms of identifying zones of concrete heterogeneity, reducing the pile cross section, etc. For all of the listed piles, data are not registered by the named test methods indicating defragmentation of the pile shaft – the presence of sections in the cross sections of which there is no concrete at all. These test methods for all piles confirmed the compliance of their actual length with the design values. A significant defect in the continuity of the concrete of the 40op pile, according to the data of ultrasonic monitoring and seismoacoustic method, was registered in the interval of marks – (17.5–18) m, manifesting itself a sa decrease in the propagation velocity of the ultrasonic pulse from 25 to 50 % in two sounding directions, inclu-ding diametrical. This defect can be interpreted as a decrease in the effective section of the pile to 25–50 % of the average value. Defective sections of piles were found in their upper part at depth marks from 0 to –1.5 m, counting from the end surface of the head. At the same time, differences in the physical and mechanical parameters of concrete at these marks were also observed within the cross section of piles [1–5].

Study on ultrasonic detection method of a honeycomb sandwich panel

Abstract: A new material for the structure of the honeycomb sandwiched XinBi board has been in active service. In this paper, structural defects are embedded in the easily damaged parts of this new material, and the ultrasonic method is used to detect the easily damaged parts, and the acoustic signals and defect echo signals of the easily damaged parts are obtained, which provides a reference for damage evaluation of this kind of structures in site detection.

Ultrasonic non-destructive testing measures: regulation of technical requirements

Abstract: The current regulatory documents for measures in the form of standard samples CO-2, CO-1 used in ultrasonic non-destructive testing are analyzed. The normalized metrological characteristics of measures are considered. It is shown that the normalized metrological characteristics do not ensure the reliability of the control in the proper volume. Differences in the normalized characteristics of measures of the same type produced by different organizations and shortcomings in the normalization of acoustic characteristics are noted, leading to different values of instrument parameters on measures of the same type and a significant error in the evaluation of control results. The necessity of normalizing the ultrasound velocity for the types of waves actually used in the measures and reducing the permissible error of measuring the velocity in the measures to ±(0.2–0.5) % is shown. It is noted that the attenuation of ultrasound in the measures is normalized only for a longitudinal wave at one frequency of 2.5 MHz and does not provide the claimed error of ± 1 dB when adjusting to the sensitivity of the devices and assessing the size of the detected defect. It is proposed to determine the attenuation of ultrasound in measures by comparing the amplitudes of ultrasonic echo signals in these measures with the amplitude of the ultrasonic echo signal in the initial measure. At the same time, the initial measure should have a simple geometric shape that allows it to be certified according to the absolute value of the attenuation coefficient. It is noted that the current State verification scheme for measuring the propagation velocities and attenuation coefficient of ultrasonic waves in solid media requires improvement, since it does not provide for the transfer of a unit of attenuation coefficient for shear waves and it does not fully take into account the real state of affairs with the measuring instruments already used in practice. To ensure the comparability and reliability of measurement results with the help of measures in full, it is proposed to develop a unified regulatory document for the general requirements for the standardized metrological characteristics of measures, methods of their measurement and a local verification scheme for transmitting units of speed and attenuation of ultrasound.

Electromagnetic Ultrasonic Shear-Horizontal Wave to Detect Corrosion Defect of Flat Steel for Grounding Device of Transmission Pole Tower

Abstract: Detecting defects in grounded flat steel is essential for ensuring the safety and reliability of transmission tower grounding devices. However, traditional inspection methods, such as physical excavation and verification, are costly and time-consuming. This paper proposes a corrosion defect detection method for flat steel transmission tower grounding devices based on electromagnetic ultrasonic SH waves. In addition, using commercial software, a three-dimensional finite element simulation model of grounded flat steel with simulated pitting corrosion defects is constructed. The specified displacements applied to multiple surface sources mimic the horizontal shear vibrations generated by the electromagnetic ultrasonic transducer on the surface of the grounded flat steel during actual inspection. A simulation was used to investigate the propagation and attenuation characteristics of shear-horizontal ultrasonic SH0guided waves for simulated corrosion defects with various geometric configurations in grounded flat steel. The simulation investigated the propagation and attenuation characteristics of the SH0 wave in grounded flat steel and the detection of various defects for linear analysis of the results. The simulation results show that the attenuation of the electromagnetic ultrasonic guided wave is small, at only 0.0016 dB/mm, and the displacement amplitude of the echo signal decreases with the increase of the SH0 wave propagation distance. Increasing the depth and length of corrosion defects increases the echo signal amplitude. At the same time, the width of corrosion defects has little effect on the echo amplitude. Finally, a flat steel defect detection experiment was conducted, and the experimental results fit with the simulation to verify the accuracy of the simulation model. This detection method introduces a new idea for the on-site detection and quantitative identification of corrosion defects in grounded flat steel, which has significant reference value and can provide a more effective and economical method for ensuring the safety and dependability of transmission tower grounding devices.

Generation and Detection of Zero-Group-Velocity Lamb Waves with Direct-Write Piezoelectric Transducers for Nondestructive Evaluation

Abstract: Zero-group-velocity (ZGV) Lamb waves are usually excited and detected using non-contact laser ultrasonic systems, as contact techniques such as using conventional bulky discrete piezoelectric transducer may cause interferences and errors in identifying the ZGV Lamb waves due to the large mass and stiffness introduced. Nevertheless, contact transducers have many advantages over the laser ultrasonic method, including cost, sensitivity, safety, and efficiency. Here, a contact technique is explored by using lightweight and low-profile direct-write piezoelectric ultrasonic transducer (DWT) made of piezoelectric polymer coating to generate and detect the ZGV Lamb waves. The frequency shift and wave attenuation of the ZGV Lamb waves, and their ability for monitoring adhesive bonded structure are investigated with both numerical modeling and experimental testing, with comparison between the DWT and discrete piezoelectric transducer. The potential of the DWT for generating and detecting ZGV Lamb waves for ultrasonic nondestructive evaluation is demonstrated by overcoming the drawbacks of discrete piezoelectric transducers.

Design of an Ultrasonic Transducer Encapsulation for High-Temperature Applications

Abstract: A novel approach to designing the encapsulation for a high-temperature ultrasonic transducer to be capable of continuous operation over a temperature range of 25 to 650 °C is proposed. The transducer’s active element is a heavily damped lithium niobate disc of 3 MHz resonance frequency, operating in pulse-echo mode. The initial encapsulation design is developed based on the geometrical, thermal, mechanical, electrical, and ultrasonic requirements. Two finite element modeling systems are developed to analyze the thermal-induced stresses in the transducer at low and high temperatures as well as its ultrasonic performance. The simulation results are used to optimize the design before manufacturing a transducer prototype. The prototype is tested at room and elevated temperatures to verify performance.

Continuous caster final electromagnetic stirrers position optimization using genetic programming

Abstract: In January 2022 final electromagnetic stirrers were installed to improve billets’ macrostructure and to reduce defects in ŠTORE STEEL, Slovenia. From January to September 2022 the material from 1121 batches, out of 2284 batches produced, was examined using ultrasonic testing. Among these 1121 batches, 270 batches were detected with defects larger than 2.5 mm. Based on various metallurgical reports made from samples taken after an ultrasonic inspection, the root causes were found to be shrinkage porosity and segregations. Based on the gathered parameters from this period (chemical composition, casting parameters, cooling or heating parameters of billets), the occurrence of inner defects was predicted using logistic regression and genetic programming. The genetic programming proved to be better than logistic regression. Based on modeling results, optimization of the final electromagnetic stirrers position for 51CrV4 spring steel was conducted. Consequently, out of 41 examined batches, only 2 were detected with defects larger than 2.5 mm.

Phased Array Ultrasonic Testing of Stainless Steel Pipe Welds

Abstract: Weld inspection of stainless steel pipes and pressure vessels is one of the most challenging and difficult inspections for ultrasonic testing. This is due to variations in grain structure and associated anisotropy. Anisotropy causes grain scattering and adversely affects propagation of sound waves. The effect is more telling for shear waves, which, in many cases, have almost no ability to penetrate the weld volume. Longitudinal waves are affected to a lesser degree by anisotropy and can be applied for such tests. Angle beam or refracted longitudinal waves are, therefore, the accepted method for stainless steel weld inspections.