Ultrasonic Testing Method Research Articles

Application of ultrasonic testing method for determining defects of hot-deformed powder materials

The article is devoted to the analysis of elastic and plastic characteristics of composite materials during hot stamping. The purpose of this work is to offer optimal conditions for hot plasticity of composite porous material with determination of temperature conditions of hot stamping excluding the appearance of defects in the structure. Production of details of the difficult form by method of hot stamping from preparations of the cylindrical form is followed by development of barrel on a peripheral surface. Sludge sintered porous blanks, and sediment compact material, accompanied by a nonuniform height lateral deformation. In connection with the action of friction forces on the contact surfaces, this leads to the formation of a “barrel”. The heterogeneity of the deformed state is associated with the appearance of tangential tensile stresses on the free surface of the workpiece. If they exceed some critical degree of transverse deformation, cracks appear on the side surface, which leads to gas saturation (oxidation) of the inner layers of the forging, to the ingress of grease into them and its pressing into the volume of the part during hot stamping. In the end, this significantly reduces the properties of hot-stamped parts. Conclusion: the methods of determining the elastic characteristics depending on the geometric parameters of the workpieces, the applied strain energy, body density and temperature dependence of the plasticity characteristics of the hot deformation of the powder material are сonsidered.

Mechanical Properties and Very High Cycle Fatigue Behavior of Peak-Aged AA7021 Alloy

The effect of heat treatment condition on non-Cu AA7021 alloy was investigated with respect to mechanical properties and very high cycle fatigue behavior. With a focus on the influence of heat treatment, AA7021 alloy was solution heat-treated at 470 °C for 4 h and aged at 124 °C. Comparing the results of solution-treated and peak-aged AA7021 alloy shows a significant increase in Vickers hardness and tensile strength. The hardness of AA7021 alloy was increased by 65% after aging treatment, and both tensile strength and yield strength were increased by 50~80 MPa in each case. In particular, this paper investigated the very high cycle fatigue behavior of AA7021 alloy with the ultrasonic fatigue testing method using a resonance frequency of 20 kHz. The fatigue results showed that the stress amplitude of peak-aged AA7021 alloy was about 50 MPa higher than the solution-treated alloy at the same fatigue cycles. Furthermore, it was confirmed that the size of the crack initiation site was larger after peak aging than after solution treatment.

APPROBATION AND ANALYSIS OF EXPERIMENTAL RESEARCHES'S RESULTS OF THE EXTENDED METHOD OF PHYSICAL-MECHANICAL CHARACTERISTICS STEELS'S CONTROL

Most of the oil and gas equipment complex is subjected to cyclic-variable, mechanical, thermal loads and corrosive-active environment. These effects causing a change in the structural statr of the metal contribute to the accelerated development of defects, especially in places with stress concentrators, which ultimately lead to the constructions destruction. Available ultrasonic, electromagnetic, and eddy-current non-destructive testing methods are currently aimed at solving defect detection problems. However, it is more important to timely identify the initial stage of the process of damage accumulation in a metal by determining changes in the structural state of the metal. The article proposes a methodology for studies of steel structural changes arising in the process of exploitation and their impact on mechanical characteristics. A reasonable choice of the optimal indicator characterizing the image of the acoustic structural noise of the material obtained by applying ultrasonic flaw detector in a complete set with piezoelectric converters with a phased array is substantiated. The complex of physical and mechanical parameters of the investigated samples are measured and the results obtained were analyzed. The modern methods of determination of mechanical characteristics of steels are considered, their deficiencies are determined and the methods of their optimization are proposed. The regression-correlation analysis of the experimental studies results was carried out, which resulted in the equation of dependence between a set of non-destructive control parameters and mechanical characteristics of steels was obtained. In order to verify the adequacy of the proposed model and to establish the possibility of controlling the casing and tubing on the samples made, series of experimental studies were carried out, which confirmed the reliability of the resulting calculation model for determining the mechanical characteristics of the steels by using two informative parameters, namely hardness and integral density of images of acoustic structural noise.

Real-time monitoring of welding process using air-coupled ultrasonics and acoustic emission

The automated weld quality assurance can improve efficiency and productivity. This paper presents the development of real-time weld quality assurance approach for gas tungsten arc welding (GTAW) using acoustic emission (AE) and air-coupled ultrasonic testing (UT). The major weld defect of interest in this paper is burn through, that is, melting through the base metal during welding that creates a hole/gap. The in situ monitoring system evaluates the changes in weld size leading to burn through by changing the weld heat input. Different categories of burn through are defined that include melting of the back of the plate without any molten metal exiting to formation of a hole in the plate. It is demonstrated that complete air-coupled UT cannot be used simultaneously with welding due to the influence of the magnetic field that develops in the weld torch during welding, which weakens the ultrasonic signal. Consequently, a rolling UT transmitter is combined with air-coupled UT receiver to increase the signal/noise value. Wave dispersion is detected due to the different levels of burn through. While UT method provides quantitative information about the weld state, any localized surface discontinuity causes sudden surges in the AE energy indicating non-uniform welding qualitatively. It is concluded that passive and active nondestructive evaluation methods should be combined to monitor weld quality real time for qualitative and quantitative assessment.

Destructive and Nondestructive Evaluation of Dry Spots in Thick Glass Fiber Reinforced Composites

This article reports on the destructive and nondestructive evaluation of dry spots or patches in thick unidirectional glass/epoxy laminates. Dry spots in composites can act as weak regions potentially resulting in catastrophic failure if undetected. Composite samples with dry spots were fabricated and nondestructive evaluation was first carried out using non-contact air coupled ultrasonics. Two types of dryness were investigated: surface and mid-plane dryness. Both types were tested using two ultrasonic testing methods. The ultrasonic velocity was used to determine stiffness and dryness fraction maps. The results showed that the dryness could be detected and characterized using the ultrasonic nondestructive evaluation. To validate the results, a destructive analysis was carried out by cutting the sample into small pieces and burning them to obtain the weight of matrix and fibers. This was further used in micromechanics models to obtain void and dryness fractions. Both model and ultrasonic results show that dry spots result in spatial gradient of mechanical properties around the dry spot. Nondestructive characterization of dryness helps in deciding if the part must be scrapped or repaired based on the severity in terms of loss of stiffness.

Infrared Thermography for Weld Inspection: Feasibility and Application

Traditional ultrasonic testing (UT) techniques have been widely used to detect surface and sub-surface defects of welds. UT inspection is a contact method which burdens the manufacturer by storing hot specimens for inspection when the material is cool. Additionally, UT is only valid for 5 mm specimens or thicker and requires a highly skilled operator to perform the inspections and interpret the signals. Infrared thermography (IRT) has the potential to be implemented for weld inspections due to its non-contact nature. In this study, the feasibility of using IRT to overcome the limitations of UT inspection is investigated to detect inclusion, porosity, cracking, and lack of fusion in 38 weld specimens with thicknesses of 3, 8 and 13 mm. UT inspection was also performed to locate regions containing defects in the 8 mm and 13 mm specimens. Results showed that regions diagnosed with defects by the UT inspection lost heat faster than the sound weld. The IRT method was applied to six 3 mm specimens to detect their defects and successfully detected lack of fusion in one of them. All specimens were cut at the locations indicated by UT and IRT methods which proved the presence of a defect in 86% of the specimens. Despite the agreement with the UT inspection, the proposed IRT method had limited success in locating the defects in the 8 mm specimens. To fully implement in-line IRT-based weld inspections more investigations are required.

Development of the specular echoes estimator to predict relevant modes for Total Focusing Method imaging

Total Focusing Method imaging is an ultrasonic testing method which has emerged in recent years as an alternative to standard phased array inspection methods in non-destructive testing, due to its high resolution and the realistic images of defects that it provides.In the case of crack-like defects, it provides images where the profile and the tips of the defects are reconstructed. TFM imaging is a procedure which yields the spatial position of the reflectors from which the main transient signals observed in the data are originated from. Thereby, diffraction echoes are located at the tips of the defect, and specular echoes appear along the profile of the defect. This signature allows the characterization of the planar nature of the defect.However, a correct reconstruction requires the use of the relevant ultrasonic path to produce the echoes wanted among a large number of possible paths between the array transducer and the reflector.In this paper, we have developed a method based on physical considerations, for predicting relevant paths. The tool is applied in several inspection configurations involving notches nearby welds. Validation is achieved from a variety of synthetic and experimental results.

Assessment of uncertainty in damage evaluation by ultrasonic testing of composite structures

Ultrasonic testing (UT) is a commonly used non-destructive testing method of composite materials. UT enables determining a geometry of internal damage, its surface area and depth location. However, measurement uncertainty should be taken into consideration when interpreting UT results, which follows from various factors including the test material parameters and selection of the operating parameters, such as the scanning method and applied transducer’s characteristics. Moreover, uncertainty in the flaw size assessment is caused by signal or image processing methods applied to the obtained ultrasonic scans, which may return incorrect results. The article presents an overview of factors influencing on the measurement uncertainty depending on variable UT parameters, with reference to appropriate standards, as well as post-processing of the obtained scans. The experimental studies aimed at investigation on the measurement errors were performed on composite specimens made of CFRP with flat-bottom holes of various diameters using the Pulse-Echo and the Phased Array UT methods.

Pipe Maintenance Tooling development for the ITER Divertor Remote Handling System

The ITER Divertor’s 316L stainless steel cooling water pipe connections are to be remotely maintained by the first-of-a-kind Divertor Remote Handling System (DRHS) and its suite of cutting, welding and inspection tools. The requirement for welding of the highest quality in a radioactive, magnetic and high temperature environment, places significant technical risks on the technologies selected for use. This paper reports the R&D activities undertaken to mitigate these risks and concludes with the key findings and recommendations for the ongoing design.Gas Tungsten Arc Welding (GTAW) trials demonstrated that a code compliant, autogenous butt weld of 3 mm wall thickness is possible, but requires precise process control, novel techniques, and tight tolerances on material composition. The most significant findings were that vertically-offset filler-rings could be employed to positive effect, and a controlled Sulphur content of 100–150 ppm for the stainless-steel pipework was found to be necessary.The galvanic cell technology selected for the welding back-purge oxygen sensor was tested and verified for use in operating environments of 300 Gy/h gamma dose rate, 3mT magnetic field, and 60 °C ambient temperature. Cutting trials developed optimum parameters for lathe-based orbital cutting with regards to the required tool longevity, the vacuum-clean environment and the need to re-weld the joint. Finally, Volumetric Inspection trials investigated the effectiveness of Electro Magnetic Transducer (EMAT) and Phased Array Ultrasonic Testing (PAUT) methods at detecting a range of manufactured surface and volumetric defects in the weld. EMAT was found better suited to the application, but the work highlighted the need for a deeper understanding of the detection needs and their relationship to potential failure modes.

Artificial Neural Network Modelling for Prediction of SNR Effected by Probe Properties on Ultrasonic Inspection of Austenitic Stainless Steel Weldments

Abstract Many austenitic stainless steel components are used in the construction of nuclear power plants. These components are joined by different welding processes, and radiation damages occur in the welds during the service life of the plant. The plants are inspected periodically with ultrasonic test methods. Many ultrasonic inspection problems arise due to the weld metal microstructure of austenitic stainless steel weldments. The present research was conducted in order to describe the affects of probe angle and probe frequency of both transversal and longitudinal wave probes on detecting the defects of austenitic stainless steel weldments. Feed forward back propagation artificial neural network (ANN) models have been developed for predicting signal to noise ratio (SNR) of transversal and longitudinal wave probes. Input variables that affect SNR output in these models are welding angle, probe angle, probe frequency and sound path. Of the experimental data, 80% is used for a training dataset and 20% is used for a testing dataset with 10 neurons in hidden layers in developed ANN models. Mean absolute error (MAE) and mean absolute percentage error (MAPE) types are calculated as 0.0656 and 16.28%, respectively, to predict performance of ANN models in a transversal wave probe. In addition, MAE and MAPE are calculated as 0.0478 and 18.01%, respectively, for performance in a longitudinal wave probe.

Adhesive debonding inspection with a small EMAT in resonant mode

In this paper, a noncontact ultrasonic testing method with using a small electromagnetic acoustic transducer (EMAT) in resonant mode is proposed for metal-based adhesive debonding inspection. The small EMAT with a new magnet configuration and a small coil is developed firstly to improve the spatial resolution and detecting ability for minute defects. Different from conventional pulse echo method using short pulse excitation for debonding inspection, a new method based on power spectrum estimation of the resonant ultrasonic signal with long burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting ability of the small EMAT. Finally, ultrasonic C-scan images of specimens with various adhesive bonding are obtained to demonstrate the capability of this technique.

Testing an FSW Welded Joint of AA2024 and AA6082 Aluminium Plate using Ultrasonic and Penetrant Testing Method

Testing an FSW Welded Joint of AA2024 and AA6082 Aluminium Plate using Ultrasonic and Penetrant Testing Method

New Method for Testing the Grouting Compactness in Pre-Stressed Concrete Girder

Background: The post-tensioned pre-stressed concrete girder is widely used in modern bridge construction. Grouting compactness has a great influence on the safety, reliability and durability of pre-stressed concrete girders. So, it is important to test the grouting compactness of the pre-stressed girder to ensure the construction quality and meet the design requirements. However, there are some defects in the existing method for testing the grouting quality of post-tensioned pre-stressed concrete girders. Therefore, a new method should be invented. Methods: In this paper, the recent research status and patents on grouting compactness testing are summarized, and the principles of grouting quality testing methods (ultrasonic testing method, impact-echo method, radiographic testing method, endoscope testing method, infrared radiometry method, and ground penetrating radar testing method) that are commonly used are compared and analyzed. Results: Based on the advantages, disadvantages and applicability of these testing methods, by refining the current patents relating to grouting compactness testing, new intelligent testing equipment is integrated, and new method is proposed. Conclusion: This new method is more efficient and accurate and it has good applicability in engineering. Keywords: Post-tensioning method, pre-stressed concrete girder, grouting compactness, testing, new method, duct grouting.

Improvement of the ultrasonic testing method for materials with significant attenuaton

We present a phase method for ultrasonic thickness measurement of materials with significant attenuation and variants for its improvement in order to increase the efficiency of detection of informative signals and the accuracy of determining their time position. At present, composite materials have become widespread in various technical fields. Various methods, including acoustic, are used for their non-destructive testing. It should be noted that a large part of such materials has significant coefficients of attenuation of acoustic oscillations. Therefore, extending the capabilities of methods for ultrasonic thickness measurement of articles made from such materials is an important task. There are two ways that are proposed to improve the method: by using a combination of procedures for preliminary filtering of the investigated signals based on empirical mode decomposition and subsequent adaptive median filtering of r-statistics, as well as applying weight processing of r-statistics. We carried out computerized measurement experiments, which allowed the justification of choosing the aperture of a sliding window in the devised methods; we obtained dependences of signal/noise values of the initial informative characteristics on signal/noise values of the investigated signals. It is shown that the error in determining a time position of the detected echo impulses, when using the improved methods, is 1.5–2 times less than the error when the basic method is applied. The results obtained could be used for the development of new ultrasonic echo impulse thickness measurement devices with improved metrological characteristics.

Local damage evaluation of a laminate composite plate using ultrasonic birefringence of shear wave

Abstract This paper presents an ultrasonic non-destructive testing method to locally characterize composite material damage through the analysis of the anisotropy behavior variation induced by damage. The approach is based on shear wave contact measurements and analyses shear wave birefringence to estimate variation of the attenuation coefficient and shear moduli ratio between warp and weft directions. The method only requires a single piezo-electric contact sensor and thus, is easy to implement for practical applications. Moreover, unlike other methods, it does not require any reference measurement in a calibrated medium such as water to evaluate attenuation coefficient variation and shear moduli ratio. It is shown that the proposed method allows to locally qualify damage with good repeatability and robustness.

PECULIARITY OF ULTRASONIC METHODS CONTROL OF EQUIPMENT FILLED WITH TRANSPORTING OR STORING FLUIDS

The paper considers the issue of the difference in the results of ultrasonic testing of newly installed equipment and equipment in the process of operation. In most defects located directly in the cavity of the metal, there is a vacuum, the acoustic properties of which are significantly different from the acoustic properties of the base metal. Therefore, defects in the weld cavity or in metal are well reflected, and are easy to be identified and make it possible to estimate their equivalent area by amplitude. All existing ultrasonic testing methods provide device setup taking into account the absence of technological fluid in defect. This is true only for new equipment that is not in practice yet. In practice, it is often necessary to control equipment that is under operation already. It is often not adequately prepared for the survey, because of presence of transporting or storing fluids in it. If in the weld or in the base metal there is a defect with opening into the inner cavity, then it can be filled with the technological fluid under the action of capillary forces. Thus, under standard setting of the flaw detector the fluid will mask the defect, influencing the magnitude of the amplitude of the reflected signal. So not all defects are fully rejected, especially flat ones, which are the most dangerous from the point of view of equipment operation. The simulation of the studied equipment diagnostics issue using two different models of flaw detectors and the filling of the cavity of a bulk defect by various substances is performed in the work. The authors obtained the results of the influence of chemical and physical properties of fluids on indications of a defect detection.

A Novel of Internal Corrosion Assessment Methods on Drinking Water Distribution Pipelines

Various methods of corrosion assessment on drinking water distribution pipelines have been reviewed in this paper. Five methods of corrosion assessment consisting of sampling method, scanning method, ultrasonic testing method, electromagnetic inspection method and corrosion index assessments described provide valuable information regarding their implementation mechanisms. Since each method has its advantages and limitations, the application of methods on the pipeline must consider the environmental conditions of the pipeline to be inspected, as well as the equipment and resources available.

Full focal imaging of ultrasonic Lamb waves using diffuse field information

In this paper, a method is presented in which that the diffuse field information of Lamb waves is used to realize the full focal imaging of the defect that is near the transducer array. The near distance means that the defect is located in the near field of ultrasonic phased array and satisfies the near field calculation formula. Near field acoustic information of the defect is obscured by the nonlinear effects of early time saturation present in a directly acquired ultrasonic inspection. The approach proposed here is to recover near filed information through cross-correlation of diffuse fields. The diffuse field is generated through multiple scattering and reflection effects after sufficiently long time transmission of ultrasonic signal in a bounded medium. The near field information is implicitly contained throughout the diffuse field. By cross-correlating the diffuse fields of ultrasonic responses recorded at two monitoring points, the Green's functions between the two points is recovered and the direct response between them is obtained. This idea is applied to the full matrix capture of ultrasonic phased array in which the full matrix is formed by sequential acquisition of responses for each transmitter-receiver pair. A virtual array of emitters and receivers is therefore established. Typically, phase delays are used in post-processing to achieve advanced imaging. Here an undelayed full matrix of inter-element responses is reconstructed through cross-correlation of a later time diffuse full matrix. In order to evaluate the applicability of the method for ultrasonic non-destructive testing, the process of full matrix reconstruction is demonstrated experimentally on an aluminium plate containing the near field defect. Combining the full focal imaging, it is shown that a hybrid full matrix formed through a temporally weighted sum of coherent and reconstructed matrices reduces the background noise and allows the effective imaging of near field defect by direct contact experimental measurements. However, the near field defect is hidden by the region of artificial noise in conventional coherent capture images. The proposed imaging method presents a theoretical guidance for detecting and imaging near field defect in plate-like configurations by using the Lamb wave nondestructive testing method.

Измерение коэффициента затухания ультразвуковых волн в неоднородных материалах при одностороннем доступе

The article considers an improved method for measuring the ultrasonic wave attenuation coefficient in objects made of materials with a heterogeneous structure under the conditions of unilateral access to objects. The method is primarily aimed at assessing the structural condition of critical bulky objects made of concrete, cast iron, and other intricately structured materials with a view to prevent possible accidents and disasters. The ultrasonic wave attenuation coefficient is determined by processing the realizations of structural noise resulting from the reflection of a probing signal from numerous heterogeneities in the object. The article suggests an improved algorithm for processing the realizations of structural noise, the use of which makes it possible to obtain better accuracy of measurements, to expand the applicability limits of the method, and to simplify the received signals processing procedure. Matters concerned with optimizing the probing signal parameters and the transducer characteristics are studied. A number of experiments were carried out for checking the efficiency of the proposed method and of the new algorithm for processing structural noise realizations. Measurements of the longitudinal ultrasonic wave attenuation coefficient in a specially fabricated concrete block were carried out. The measurements were carried out using two methods: the classic shadow method and the proposed method based on processing the structural noise realizations. The experiments showed good results: the measurement accuracy has been improved by almost 10 times compared with the previous version of the proposed method. The most appropriate application field of the proposed method is monitoring the structural state of critical bulky objects made of materials with a heterogeneous structure like dams and bridge supports under the conditions in which it is impossible to apply other ultrasonic non-destructive testing methods, e.g., those based on ultrasonic wave velocity measurements.

Perhitungan laju korosi dan perancangan sistem proteksi katodik anoda korban di lambung kapal tugboat Bontang o4 PT Badak NGL Bontang

Corrosion happens differently for each point of hull plate which caused of corrosion rate differences. So that is very important to measure it for each point, which is calculated using Weight Gain Loss Method. The measurement of plate thickness that used is Ultrasonic Test Method conducted by PT BKI. To determine the condition of ship protection, then the coating and sacrificial anode system is evaluated by testing the composition and current and voltage of anode as well. Furthermore, the number and position of anode is also analyzed. So that the re-design of cathode protection is needed by referring to the PT BKI’s standards. Then the prediction of corrosion rate is calculated by using the design of cathode protection. The largest corrosion rates are in the amidships and portside for each plate lane, they are on the keel plate point K3 is 0.37 mm/years, pedestal plate point A4 is 1.05 mm/years, bilge plate point B4 is 0.62 mm/years and side plate point C5 is 0.39 mm/years. But the number of installed anode is 31 anodes with an irregular position. So in this study, done the redesign system of cathode protection based on regulations issued by PT BKI, with the result of the number of the anode is 56 units. Using the design, then carried a prediction by the result is lower, that on the keel plate is 0.073 mm/years, pedestal plate is 0.021 mm/years, bilge plate is 0.013 mm/years and the side plate is 0.014 mm/years.