Ultrasonic Thickness Measurement Research Articles

Accurate Ultrasonic Thickness Measurement for Arbitrary Time-Variant Thermal Profile.

Ultrasonic thickness measurement of mechanical structures is one of the most popular and commonly used nondestructive methods for various kinds of process control and corrosion monitoring. With ultrasonic propagation speed being temperature-dependent, the thickness measurement can be performed reliably only when the thermal profile is completely known. Most conventional techniques assume the temperature of the test structure is uniform and at room temperature across its thickness. Such assumptions may lead to large errors in the thickness measurement, especially when there are significant temperature variations across the thickness. State-of-the-art techniques use external temperature measurements or implement iterative methods to compensate for the unknown thermal profiles. However, such techniques produce unsatisfactory results when the heat distribution is complex or varies rapidly with time. In this work, we propose a two-sensors technique, using both compressive and shear excitations, with a non-iterative rapid data processing method for accurate thickness measurement under arbitrary time-variant thermal profile. The independent behavior of shear and compressive waves is used to formulate a real-time thickness estimation technique. The developed technique is experimentally validated on a steel plate with fixed acoustic sensors. Test results show that the error in thickness estimation can be reduced by up to 98% compared to conventional thickness gauging methods.

Metallurgical insight of premature failure of a Blast Furnace copper stave

Present study investigates the premature failure (leakage) of copper (Cu) cooling staves placed at the lower stack region of a Blast Furnace (BF). This failure resulted in an increased frequency of make-up/ reserve water compensation every 10 h instead of average 24hrs. Detailed macro and microstructural analysis were carried out to understand the mechanism of failure in the Cu stave using phenomena observations, dial gauge measurements, metallographic investigation, and chemical analysis. Directional accretion of burden fines and puncture (leakage) profile were observed macroscopically. Puncture occurred from outer surface to inner surface of the channels of the stave. Micrographs of puncture location revealed non-uniform microstructure and grain deformation. Analysis suggested surface wear of the Cu stave due to a combined effect of continuous accretion of burden along with hot gas flow. Wear led to reduction in thickness and subsequent puncture/ leakage took place at the channel locations having a minimum cross-sectional thickness. With the help of this study, a failure mechanism of BF Cu Stave, a process critical component, has been explored. Recommendations such as insert modification, using more wear-resistant material or protective layer and conducting intermittent ultrasonic thickness measurements have been proposed to get an early warning of any untoward damages and process delays.

An integration method of a hybrid genetic algorithm and the Levenberg–Marquardt algorithm for ultrasonic testing

The accurate measurement of time-of-flight (TOF) is essential in ultrasonic testing. Further, noise interference is the key factor affecting the measurement accuracy. Therefore, to develop a reliable computational method of TOF for test pieces working in noisy environments, an integration method of a hybrid genetic algorithm and the Levenberg–Marquardt algorithm (GA–LM) for ultrasonic thickness measurement is proposed in the present research. A Gaussian model is first established for an echo signal. Further, the model-based parameter estimation is converted into a nonlinear optimization problem by applying the least square method. As the parameter estimation methods are easily affected by the initial value, an integrating innovation of the GA–LM algorithm is proposed. The initial values of the model parameters are selected by GA to obtain an approximate global optimal solution. Subsequently, this approximate solution is used as the initial value for the LM algorithm to perform iterations. The accurate global optimal solution of the Gaussian model is obtained through these iterations. Finally, the measuring accuracy and robustness of the GA–LM algorithm for TOF computation are verified by both numerical simulation and experiment data

A novel laser-EMAT ultrasonic longitudinal wave resonance method for wall thickness measurement at high temperatures

In this paper we propose a novel ultrasonic longitudinal wave resonance method for measuring the thickness of metal walls using a laser-electromagnetic acoustic transducer (Laser-EMAT). The method is based on the surface constraint mechanism (SCM) of the material and is expected to be capable of accurately detecting local thinning of metal walls in a non-contact manner and at high temperatures. Based on finite element analysis of laser-EMAT ultrasonic resonance measurement of aluminum alloy thickness, we investigated the effects of such key factors as SCM, irradiation parameters of laser source, and the size of EMAT receiving coil on the accuracy of thickness measurement (resonance frequency position) and on the amplitude of the resonance wave. Both numerical simulations and experiments are conducted to demonstrate that the measurement accuracy of the proposed method is not affected by SCM, irradiation laser source parameters, and EMAT receiving coil size, and that accurate detection of stepped aluminum plates with thickness thinning from 3.0 mm to 0.5 mm is achieved. Furthermore, we were able to perform rapid detection of aluminum thin plate thickness at 500 °C temperature with an EMAT lift-off of 5.0 mm and achieved a relative experimental error as small as 3.40 %. The results obtained in this study showed that the proposed method performed well in non-contact measurement of metal thinning in harsh environment of high temperature.

Experimental Analysis of Pre-Forming Parameters on Abnormalities, Thickness, and Void Content of Glass/Epoxy Composite In VBO-Oven Cure Manufacturing

Autoclave-based production of composite laminates leads to extended time requirements, increased manufacturing expenses, and the accumulation of significant residual stress. These limitations have spurred research and innovation in seeking alternative out-of-autoclave (OOA) processing methods. The present study aimed to measure the impact of distinct and combined pre-forming parameters within the pre-forming process of vacuum bagging with oven curing (VBO-oven curing) on thickness, abnormalities, and void content in cured laminates of conventional, cost-effective glass/epoxy autoclave composite material. The abnormalities were analyzed using ultrasonic C-scan and thickness measurement was done to determine thickness variations. A burn-off test was employed to measure the void content. The relationship between processing parameters was subsequently investigated via analysis of variance (ANOVA). Higher thickness standard deviation was yielded at higher abnormality percentages in the C-scan results, resembling total discontinuities and non-uniformities. Voids were highest in the laminate produced via the standard pre-forming process. Edge breather, release wax, and intensifier reduced the void content by approximately 11.87%, 12.93% and 6.85%, respectively.

Sensitivity Improvements for Picosecond Ultrasonic Thickness Measurements in Gold and Tungsten Nanoscale Films

Picosecond ultrasonics, as a nondestructive and noncontact method, can be employed for nanoscale metallic film thickness measurements. The sensitivity of the system, which determines the measurement precision and practicability of this technique, is often limited by the weak intensity of the ultrasonic signal. To solve this problem, we investigate the distinct mechanisms involved in picosecond ultrasonic thickness measurement for two types of metals, namely tungsten (W) and gold (Au). For thickness measurement in W films, theory and simulation show that optimizing the pump and probe laser wavelengths, which determine the intensity and shape of the ultrasonic signal, is critical to improving measurement sensitivity, while for Au film measurements, where acoustic-induced beam distortion is dominant, the signal intensity can be optimized by selecting an appropriate aperture size and sample position. The above approaches are validated in experiments. A dual-wavelength pump–probe system is constructed based on a passively mode-locked ytterbium-doped fiber laser. The smoothing method and multipeak Gaussian fitting are employed for the extraction of ultrasonic time-of-flight. Subnanometer measurement precision is achieved in a series of W and Au films with thicknesses of 43–750 nm. This work can be applied to various high-precision, noncontact measurements of metal film thickness in the semiconductor industry.

Corrosion Monitoring Techniques in Subcritical and Supercritical Water Environments

A series of advanced equipment exposed to sub-/supercritical water environments at high temperatures, high pressures, and extreme water chemistry with high salt and dissolved oxygen content faces serious corrosion problems. Obtaining on-site corrosion data for typical materials in harsh environments is crucial for operating and maintaining related equipment and optimizing various corrosion prediction models. First, this article introduces the advantages and disadvantages, usage scenarios, and future development potential of several in situ monitoring technologies, including ultrasonic thickness measurement, the infrared thermography method, microwave imaging, eddy current detection, and acoustic emission. Considering the importance of electrochemical corrosion data in revealing microscale and nanoscale corrosion mechanisms, in situ testing techniques such as electrical resistance probes, electrochemical corrosion potential, electrochemical impedance spectroscopy, and electrochemical noise that can be applied to sub-/supercritical water systems were systematically discussed. The testing platform and typical data obtained were discussed with thick and heavy colors to establish a mechanical prediction model for corrosion behavior. It is of great significance to promote the development of corrosion monitoring techniques, such as breaking through testing temperature limitations and broadening the industrial application scenarios and maturity.

Pipeline thickness estimation using the dispersion of higher-order SH guided waves

Abstract Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal (SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than 1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.

Design of submarine pipeline inspection system based on ultrasound

A design of a non-destructive testing system for underwater pipelines based on ultrasound has been proposed, consisting of a three-axis control system and an ultrasonic thickness measurement system. This can achieve full coverage testing and real-time data transmission of pipeline wall thickness through integrated composite rotating mechanisms, travel driving mechanisms, pipeline surface preprocessing mechanisms, data acquisition systems, etc., with high automation and the ability to achieve pipeline based testing. Among them, the pipeline surface pretreatment mechanism includes a polishing mechanism and a circulating immersion system, which are used to improve the coupling effect between the pipeline wall and the ultrasonic probe. This non-destructive testing system can achieve high detection efficiency and testing accuracy, effectively solving the current problems of undersea pipeline leakage and inaccurate positioning of corrosion damage. At present, the problem of global and efficient scanning still needs to be solved, as otherwise it will be difficult to further improve work efficiency. Highlights A design of a non-destructive testing system for underwater pipelines based on ultrasound has been proposed, consisting of a three-axis control system and an ultrasonic thickness measurement system The system can realize scanning detection with high efficiency and automation The system is equipped with an automatic coupling mechanism to ensure the stability and reliability of the work

Ultrasonic Thickness Measurement Method and System Implementation Based on Sampling Reconstruction and Phase Feature Extraction.

The existing ultrasonic thickness measurement systems require high sampling frequencies for echo signal acquisition, leading to complex circuit designs and high costs. Moreover, extracting the characteristics of ultrasonic echo signals for accurate thickness measurement poses significant challenges. To address these issues, this paper proposes a method that utilizes conventional sampling frequencies to acquire high-frequency ultrasonic echo signals, overcoming the limitations of high-frequency data acquisition imposed by the Nyquist-Shannon sampling theorem. By employing an improved sampling reconstruction technique, the multi-cycle sampling signals are reconstructed and rearranged within a single cycle, effectively increasing the equivalent sampling frequency. Additionally, a combination of coarse estimation using fast Fourier transform (FFT) and precise phase extraction using the moving sine fitting algorithm is proposed for accurate thickness measurement, resolving the limitations of common thickness measurement methods such as peak detection, envelope detection, and Hilbert autocorrelation in terms of low measurement accuracy. Experimental results obtained from thickness measurements on 45 steel ultrasonic test blocks within the range of 3 mm to 20 mm indicate a measurement error of ±0.01 mm, while for thicknesses ranging from 1 mm to 50 mm, the measurement error is ±0.05 mm.

Separation of multi-echo overlapping ultrasonic signals for increasing the axial resolution using a neural network

Abstract The ultrasonic pulse-echo method plays a significant role in ultrasonic thickness measurement. However, when the measured thickness is relatively thin, it is universal for the reflected ultrasonic echoes to overlap in the time domain which constrains the achievable resolution using the conventional pulse-echo method. A deep learning network for multi-echo overlapping ultrasonic signals separation under the constraint of an ultrasonic transducer with specific center frequency and bandwidth was proposed to enhance the axial resolution. With this model, the adaptive separation of overlapping signals with an unknown number of echoes is achieved by extracting detailed features of the overlapping signals. An overlapping signal training dataset based on truncated Nakagami functions is constructed to train the network. Simulation experiments under different degrees of overlap and noise levels were conducted for the performance analysis. Simulation results manifested the performance advantage of proposed separation method over some traditional separation methods. Further, ultrasonic thickness measurement experiments were performed on thin-walled aluminum alloy plates with various thicknesses, demonstrating feasibility and practicability of the network over traditional separation methods.

Autonomous Ultrasonic Thickness Measurement of Steel Bridge Members Using a Climbing Bicycle Robot

This paper presents the development of a steel-climbing bicycle robot integrated with an ultrasonic sensing device towards autonomous thickness measurement of steel bridge members. The bicycle-like robot has two magnetic wheels controlled by two independent steering actuators, which navigates on various steel surfaces (flat, curved, rough, concave, and convex). The compact ultrasonic sensing device is capable of high-voltage pulse excitation, filtering/amplification of the received ultrasonic signal, and high-speed analog-to-digital conversions (up to 80 MHz). Along with the ultrasonic sensing device, the robot carries a dual element transducer, an automatic gel couplant dispenser, a position tracking sensor, and a camera. A mounting/retrieving mechanism of the transducer is designed to ensure the reliable contact of the transducer on steel surfaces. The camera view assists an operator to safely navigate the robot to measurement locations, properly dispense gel couplant, and firmly press the transducer on a measurement surface. The automated robot localization provides accurate thickness measurement locations, which are mapped real-time in three-dimensional (3D) space together with the robot’s travel path. We validate the performance of the developed system in several indoor and outdoor tests. Weblink to a supplementary video demonstrating the robot’s maneuverability and ultrasonic thickness measurements is available in the Data Availability Statement of this article.

Assessing the possibility of changing the monitoring frequency of the residual thicknesses of the navigation locks gates elements

One of the main methods for monitoring the technical condition of the navigation locks gates is to determine the amount of corrosion wear of their elements using ultrasonic thickness measurement. This diagnostic operation is performed at least once every five years. In accordance with the methodology, the control requires the removal of the protective coating in the measurement area. At the same time, there is no possibility of a full restoration of the coating. The specified frequency of measurements is adopted based on the peculiarities of the maintenance of locks and the durability of protective coatings, the service life of which does not exceed 5 years. It is noted that recently, the cases of measurements with a satisfactory technical condition of the protective coating on the elements of the structures, which are being examined, have been more frequent. This circumstance indicates an increase in the service life of protective coatings and, consequently, the possibility of revising the established frequency of measurements of the residual thickness of the gates elements. In this regard, the purpose of the study is to assess the possibility of changing the timing of ultrasonic thickness measurement during primary and periodic measurements of the residual thicknesses of the gate elements, taking into account the state of the protective coating. To achieve this goal, the collection and analysis of the range of protective coatings used in the anticorrosion protection of the main and emergency repair gates of navigation locks, their service life, as well as permissible deviations in thickness for the supplied rolled metal, are carried out. It has been established that epoxy-based protective coatings are most often used as primer and top coats. The thickness of the applied coatings has increased by 2–3 times and averages 200–350 µm. Damage to coatings in the period from 5 to 10 years of operation averages about 6 % of the total surface area. In the course of the study, it has been also found that the permissible minus limit values for deviations in the thickness of the supplied rolled products can range from 0.8 to 4.2 mm, depending on the thickness of the sheet and the accuracy of its manufacture. The presence of such deviations has a particularly negative effect on the resource of small thicknesses. Additionally, the maximum average value of the corrosion rate of metal structure elements in operation is determined. The totality of the information obtained makes it possible to develop recommendations for changing the timing of the residual thicknesses measurement, ensuring the safe operation of the considered elements of mechanical equipment.

Wave velocity measurement in the through-thickness direction of the anisotropic material plate with ultrasonic polar scan

Ultrasonic polar scan (UPS) records the amplitude in transmission for a wide range of incidence angles, providing a UPS image with characteristic contours reflecting the acoustic parameters of the material. This study focused on a newly developed wave velocity measurement of the DD6 single-crystal material plate by analyzing the UPS image to realize the ultrasonic thickness measurement of the DD6 single-crystal material plate accordingly. Firstly, considering transducer contour size compensation, the UPS images are obtained by numerical simulation on the DD6 single-crystal material plates with different crystal orientations. Secondly, the fitting equations are obtained by analyzing the UPS images to calculate wave velocity in the thickness direction. Finally, a 5-joint UPS scanner is designed to validate the accuracy of wave velocity simulation results experimentally, and it indicates a good agreement with conventional ultrasonic velocity measurement. The measurement results demonstrated that the UPS method could evaluate the wave velocity in the through-thickness direction of the DD6 single-crystal material plate with high precision.

Research on Identification and Detection of Aluminum Plate Thickness Step Change Based on Electromagnetic Acoustic Resonance

The conventional ultrasonic thickness measurement method is ineffective in detecting the measured specimen with a step change in thickness as it is easy to cause multimode acoustic mixing in the ultrasonic detection process. To solve this problem, this paper presented an electromagnetic acoustic resonance (EMAR) moving scan identification method based on a frequency–frequency energy density precipitation (FFEDP) algorithm, which uses a standing wave resonance mode to accurately extract step thickness information and employs the algorithm to separate step thickness information. According to the simulation results, the ratio of the highest energy density of the spectrum signal on both sides of the step area to the total energy density had an opposite linear change rule with the equidistant movement of the transducer coil. The thickness step area can be identified by analyzing the crossover point of the contrast value change. The experimental results showed that the proposed method can accurately extract the thickness information under millimeter-level stepping distance for sector-notched specimens with step surfaces of different thicknesses, and at the same time realize the effective identification of the step surface.

Ultrasonic measurement of thickness of carotid arterial wall using its natural longitudinal displacement

The thickness of the carotid arterial wall obtained from B-mode imaging using ultrasonic diagnostic devices is widely used for the diagnosis of atherosclerosis. However, the measurement interval in the lateral direction of the B-mode image depended on the beam interval (>100 μm). Therefore, the B-mode image is discrete in the lateral direction and cannot reflect changes in local and minute thicknesses. A method for measuring the roughness of the luminal surface of the wall was proposed using the displacement of the carotid arterial wall in the lateral direction during one heartbeat. In this method, the lateral measurement interval is much shorter than the beam interval, enabling a smooth measurement of the luminal surface. By simultaneously applying the method to the lumen-intima and medial-adventitia boundaries of the wall, we propose a novel method to measure the local and minute thicknesses of the carotid arterial wall.

A method to determine the uncertainties of solid particle erosion measurements utilizing machine learning techniques

The ability to predict solid particle erosion is a vital task for the integrity management of pipelines carrying solid particles in many industries. Usually, the accuracy of predicted values is assessed by comparing them with the measured erosion of some cases where data is available. Thus, defining the uncertainties of the experimental data of erosion is crucial to evaluate the reliability of the predictions of solid particle erosion and consequently, the decisions made based on these predictions. The databases gathered by many investigators that include erosion data of various test cases have been considered for this uncertainty investigation. These cases include erosion rate data collected using the ultrasonic thickness measurement technique for gas-sand flows in 0.0508, 0.0762, and 0.1016-m elbow geometries with various particle sizes (75,150,300,550 μm) and air velocities vary in the range between 11 up to 202 m per seconds. This study aims to develop a framework for defining the uncertainties of erosion experiments. For this purpose, first, the uncertainties of repeated experiments were estimated and then analytical analysis was used to generalize these results to cases where repeated results were unavailable. Based on this idea, a correlation between erosion and the most effective parameters was developed. Then, machine learning algorithms were used to determine a correlation between the erosion rate and chosen parameters including material hardness, pipe size, particle size, and flow velocity. The framework of the current model/method is based on the combined results of analytical analysis and machine learning procedure, and the estimated uncertainties are presented by lower and upper bounds curves of erosion data.

Environmental aspects of metal corrosion at oil and gas chemical enterprises

Metal corrosion of technological equipment not only has a significant impact on industry, but also has serious consequences for the environment, being one of the causes of environmental problems. The object of research in this paper is the issue of corrosion damage to the metal of technological equipment, types of corrosion and corrosion damage, and methods of protection against corrosion. On the example of a shell and tube heat exchanger with the help of nondestructive methods of control (external and internal inspection, ultrasonic thickness measurement) the research of corrosion rate of its main elements has been carried out. According to the results of researches the calculation of corrosion rate of the main elements of the heat exchanger was carried out. The corrosion rate for the heat exchanger shell was found to be 0.37 mm/year, which exceeds the value of 0.1 mm/year, which is accepted in the design of this heat exchanger. The obtained results allowed to identify the most vulnerable places of the research object and to choose the most effective ways to protect the base metal of the heat exchanger from corrosion.

Application of Pulse Compression Technology in Electromagnetic Ultrasonic Thickness Measurement of High-Temperature Continuous Casting

Application of Pulse Compression Technology in Electromagnetic Ultrasonic Thickness Measurement of High-Temperature Continuous Casting

Dry Coupled Ultrasonic Non-Destructive Evaluation Using an Over-Actuated Unmanned Aerial Vehicle

Unmanned aerial vehicles (UAVs) are seeing increasing adoption to automated remote and in situ inspection of industrial assets, removing the need for hazardous manned access. Aerial manipulator architectures supporting pose-decoupled exertion of force and torque would further enable UAV deployment of contact-based transducers for sub-surface structural health assessment. Herein, for the first time, we introduce an over-actuated multirotor deploying a dry-coupled ultrasonic wheel probe as a novel means of wall thickness mapping. Using bi-axial tilting propellers in a unique tricopter layout, this system performs direct thrust vectoring for efficient omnidirectional flight and application of interaction forces. In laboratory testing, we demonstrate stable and repeatable probe deployment in a variety of representative asset inspection operations. We obtain a mean absolute error (MAE) in measured thickness of under 0.10 mm when measuring an aluminum sample with varying wall thickness. This is maintained over repeated exit and reentry of surface contact and when the sample is mounted vertically or on the underside of a 45° overhang. Furthermore, when rolling the probe dynamically across the sample surface in an area scanning modality, an MAE in wall thickness below 0.28 mm is recorded. Multi-modal operational confidence bounds of the system are thereby quantitatively defined. Note to Practitioners—Motivation for this article stems from the desire to enhance the speed and level of insight into structural health currently offered through remote aerial inspection processes. We approach this by integration of a thrust vectoring multirotor platform with a dry-coupling wheel probe for aerial ultrasonic thickness measurement. This system reliably presses the probe into the target surface and obtains point measurements across various surface orientations without a stabilizing frame. This broadens applicability and permits novel inspections where couplant gel would otherwise contaminate the surface and require manual cleaning. We profile thickness along a scanned linear section, a mode suited to corrosion mapping of large surface areas such as petrochemical storage tanks, pipework, or similar assets. We also make detailed consideration toward measurement accuracy, repeatability, and localization, an aspect commonly overlooked in literature. Future work to characterize variable friction effects currently limiting rolling scan speed and measurement coverage density may be beneficial. Quantitative study of the effectiveness of dry-couplant in the presence of any uncommon surface contaminants specific to a desired use-case is also advised.