New Non-destructive Testing Research Articles

Advances in NDT and Materials Characterization by Eddy Currents

New materials and production technologies demand improved non-destructive techniques for inspection and defect evaluation, especially when critical safety applications are involved. In this paper a new non-destructive testing (NDT) system is presented. The innovative system is composed by a new type of eddy currents probe, electronic devices for signal generation, conditioning and conversion, automated mechanized scanning and analysis software. This new probe provides enhanced lift-off immunity and improved sensitivity for defects detection. The IOnic system was developed mostly to be used for the defects detection on aluminum solid state processed alloys as Friction Stir Welding (FSW) and Friction Spot Welding (FSpW), however recent studies revealed IOnic probe good capacities on other applications.This study evaluates the capacity of the IOnic probe on detecting buried defects under the surface of Graphite and Stainless steel AISI 304 alloys extending the probe application to other materials and defect morphologies. In order to evaluate its performance results, a comparison with results from conventional EC probes is discussed.

The Development of Neutron Radiography and Tomography on a SLOWPOKE-2 Reactor

Abstract Development of neutron radiography at the Royal Military College of Canada (RMC) started by trying to interest the Royal Canadian Air Force (RCAF) in this new non-destructive testing (NDT) technique. A Californium-252 based device was ordered and then installed at RMC for development of applicable techniques for aircraft by the first author. A second and transportable device was then designed, modified and used in trials at RCAF Bases and other locations for one year. This activity was the only foreign loan of the U.S. Californium Loan Program. Around this time, SLOWPOKE-2 reactors were being installed at four Canadian universities, while a new science and engineering building was being built at RMC. A reactor pool was incorporated and efforts to procure a reactor succeeded a decade later with a SLOWPOKE-2 reactor being installed at RMC. The only modification by the vendor for RMC was a thermal column replacing an irradiation site inside the reactor container for a later installation of a neutron beam tube (NBT). Development of a working NBT took several years, starting with the second author. A demonstration of the actual worth of neutron radiography took place with a CF-18 Hornet aircraft being neutron and X-radiographed at McClellan Air Force Base, Sacramento, CA. This inspection was followed by one of the rudders that had indications of water ingress being radiographed successfully at RMC just after the NBT became functional. The next step was to develop a neutron radioscopy system (NRS), initially employing film and then digital imaging, and is in use today for all flight control surfaces (FCS). With the third author, a technique capable of removing water from affected FCS was developed at RMC. Heating equipment and a vacuum system were utilized to carefully remove the water. This technique was proven using a sequence of near real time neutron images obtained during the drying process. The results of the drying process were correlated with a relative humidity gauge and an NDT technique that could be performed at Canadian Forces (CF) Bases was developed. In order to determine the structural integrity of the component having undergone this water removal, further research was required into the effect of water inside composite honeycomb structures. This need has led to the present development of neutron tomography on the reactor at RMC, which is capable of determining the exact location of water ingress inside composite components. This technique has been successfully applied to coupons as well as to complete rudders.

A Non-Destructive Testing Based on Electromagnetic Measurements and Neural Networks for the Inspection of Concrete Structures

This paper presents a new non-destructive testing (NDT) for reinforced concrete structures, in order to identify the components of their reinforcement. A time varying electromagnetic field is generated close to the structure by electromagnetic devices specially designed for this purpose. The presence of ferromagnetic materials (the steel bars of the reinforcement) immersed in the concrete disturbs the magnetic field at the surface of the structure. These field alterations are detected by sensors coils placed on the concrete surface. Variations in position and cross section (the size) of steel bars immersed in concrete originate slightly different values for the induced voltages at the coils.. The values ​​for the induced voltages were obtained in laboratory tests, and multi-layer perceptron artificial neural networks with Levemberg-Marquardt training algorithm were used to identify the location and size of the bar. Preliminary results can be considered very good.

The Research of Non-Uniformity Correction of Infrared Image in Thermal Wave Testing Based on Homomorphism Technology

The infrared thermal wave technology is a new nondestructive testing (NDT) method with a kind of advantage, including non-contact, intuitionistic, fast et al. But the infrared images always have defects that the low-contrast and high-noise due to uneven brightness and calefaction in the testing process, which enhance the difficulty of following quantitative distinguishment of defects. Therefore, the improved homomorphic filtering is given in this article. The detailed processes of the method and testing results are given. The results of the experiments show that the method has higher peak signal to noise ratio (PSNR), can improve image quality, which establish basis for future research of image segmentation.

Welded Joint Nonpenetration and Slag Inclusion Evaluation Based on MMM Signal Characteristic

The metal magnetic memory (MMM) technology, a new nondestructive testing (NDT), has potentials of quantitative evaluation on welded joint defects. This paper investigates MMM signal quantitative characteristic of welded joint defects. Steel Q235 welded joint specimens, prefabricated with nonpenetration and slag inclusion, have been scanned by MMM testing instrument at 0kN, 150kN and 230kN tension loads on tensile machinery. For the nonpenetration specimens, MMM peak amplitude ΔHp and the peak width D adds with the increasing of tensile load, but gradient K varies a little. As for the slag inclusion specimens, the ΔHp and K enhances along with tensile load increasing, but the D varies a little. The X-ray testing results at 0kN, 150kN and 230kN tension loads show the validity of MMM signal characteristic. This means the feasibility of the weld qualitative and quantitative evaluation based on MMM method.

Cracks Detection in Mg Alloy by Electro-Ultrasonic Spectroscopy

New non-destructive testing (NDT) method is based on the effect of the ultrasonic vibrations on the electron transport in samples with macroscopic defects as cracks or defect centers affecting electrical conductivity. On the frequency given by the subtraction of exciting frequencies new intermodulation signal appears. Its value is given by electric resistance modulation by the defects and un-homogeneities in the sample structure. In our experiment we used the ultrasonic actuator with frequency fU when the period of wave is longer than the dielectric relaxation time in analyzed sample. In this case the effects of electron bunching by ultrasonic wave are negligible. The ultrasonic wave length is much larger than the electrons mean free path and the wave period is much longer than the mean free time among the electrons collision with scattering centers and defects. Then the electron transport is described by the quasi-steady state transport equation in one-electron approximation. Because of the requirement of charge neutrality, no net AC electric current with the ultrasonic wave frequency fU can be carried by the wave. Similar situation exists for samples excited by standing ultrasonic waves. The electrical conductivity varies with time due to that the cracks geometry is changed with frequency of the ultrasonic vibration. The sample conductivity is affected mainly by the presence of cracks and defects boundaries perpendicular to the electric current density vector. In our experiment the amplitude of ultrasonic vibration is so low that no new cracks are generated and then the proposed testing method belongs to NDT.

Virtual Prototyping Process Supported by New Diagnostic Method -Method of Metal Magnetic Memory

The aim of this work is to implement a new nondestructive testing (NDT) method based on the metal magnetic memory (MMM) effect into comprehensive diagnostic approach for power-line connectors, which is of great practical importance. Essence of this method lies in detection of stress concentration zones (SCZs) in material of the considered element during its operation (before micro-cracks and fracture occurs). If to compare with the traditional NDT methods, which indicate SCZs after the failure (post factum), this method provides major progress in the field of NDT. In this paper an approach of connection of numerical structural simulation (static and dynamic) with MMM-based testing method is also proposed. SCZs in power-line mechanical connector were evaluated and dynamic analysis of a complete power line, which included the analyzed connector, was carried out by means of MSC.ADAMS. Uniqueness of this analysis consist in integration of FEM analysis, MSC.ADAMS multibody system analysis (for testing of working conditions in advance - during virtual prototyping) and verification using MMM method. This hybrid approach enables to accomplish diagnostic analysis of selected construction elements and provides the possibility to take into consideration actual working conditions (e.g. vibrations) of the element. Proposed diagnostics method can substantially increase operational safety of electrical connectors and lines.

Advanced technique for non-destructive testing of friction stir welding of metals

In this paper a new non-destructive testing (NDT) system focusing on micro size superficial defects in metallic joints is presented. The innovative system is composed by a new type of eddy currents probe, electronic devices for signal generation, conditioning and conversion, automated mechanized scanning and analysis software. The key original aspect of this system is the new type of eddy currents probe. This new probe provides enhanced lift-off immunity and improved sensitivity for micro size imperfections. The probe concept was studied using a Finite Element Method (FEM) tool and experimental verified using a standard defect. The testing results on some friction stir welding (FSW) specimens clearly show that the system is able to detect superficial defects less than 60 μm deep, which significantly increases the actual state of the art in NDT reliability for micro imperfections detection. The system can be applied to a broad range of industries which include manufacturing, maintenance and engineering companies.

The Quantitative Measurement Model of ACFM Based on Swept Frequency Method

The alternative current field measurement (ACFM) technique is a new non-destructive testing (NDT) method to evaluate the surface flaws, and in contract to other methods it has advantages of non-contacting and non-calibrating. Precise locating and crack length measurement can be easily achieved. But it is rather difficult to measure the crack depth with the complicated mathematic model. Its application is thus limited. On this ground, the swept frequency method is introduced to make up of this shortage. The penetration depth of eddy current that is theoretically different for different operational frequencies is the principle of crack depth measurement of the swept frequency method. By means of measuring the switching-frequency of the characteristic curve, the information of flaw depth is achieved by sweeping frequency. The paper introduced the physical model of ACFM and assayed the errors of measurement. Some methods were introduced to decrease the errors. The crack depth is proportional to the interval of the switching-frequency of flaw and of no-flaw, which is detected at the position of minimum value of Bz.

A new non-contacting non-destructive testing method for defect detection in concrete

A new non-destructive testing (NDT) method for defect detection in concrete structures is presented. The method is based on the dynamic response of flawed concrete structures subjected to impact loading. Conversely to similar NDT techniques, such as the impact-echo method, the present method uses non-contacting devices for both impact generation (a shock tube producing shock waves) and response monitoring (laser vibrometers measuring concrete surface velocity). Experimental and numerical (finite element) studies have been carried out for concrete specimens containing artificial defects (penny-shaped cracks parallel to the free surface) with varying length and depth. According to the experimental and numerical results, it appears that the present method enables an effective detection of defects, particularly in the range of shallow defects.

Modified electrochemical emission spectroscopy (MEES) As technique of NDT for detection localized corrosion of copper alloys in seawater

An early stage of localized corrosion, i.e., pitting and crevice corrosion, of a pure copper and a brass in uncoated and coated conditions in seawater was investigated in situ by a new non-destructive testing (NDT) method. The new method of localized corrosion detection is based on the optical corrosion-meter for measuring the corrosion current density ( J) and on a modified electrochemical noise technique for determining the corrosion admittance ( A c) at the open-circuit potential of the alloys in solutions. The observations of localized corrosion were basically interferometric perturbations detected by the optical corrosion-meter only on the uncoated copper and the coated brass at the beginning of the tests. The interferometic perturbations interpreted as a localized corrosion in the form of an early pitting and crevice corrosion, of a depth ranging from 0.3 μm to several micrometers, of the uncoated copper and the coated brass, respectively. Also, the early stage of localized corrosion of the same alloys in the same conditions was determined in situ by a modified electrochemical noise (EN) technique, called the modified electrochemical emission spectroscopy (MEES) technique, simultaneously during the optical interferometry measurements. Determinations of localized corrosion by the MEES technique were electrochemical noise spectra detected on corrosion admittance ( A c)-time plots of the alloys in solutions. The corrosion admittance parameter, A c=(d J/d V), which defined the MEES technique, is capable of indicating localized corrosion and uniform corrosion activities. In this investigation, the parameter A c was modified in which the change of the corrosion current density (d J) was measured by the optical corrosion-meter rather than by the zero resistance ammeter, which is usually used for measuring the d J in electrochemical noise technique. Consequently, results of the present work indicate that optical corrosion-meter as an electromagnetic method of measuring the corrosion current density, and MEES technique, as an electronic method for determining the A c, are very useful techniques as non-destructive methods for the detection of localized corrosion at the initiation stage of the phenomenon.

Nondestructive testing by ESPI and quasi phase shift gradient technique

A new nondestructive testing (NDT) technique, which is based on Electronic Speckle Pattern Interferometry (ESPI) and digital image processing with quasi phase shift and gradient technique, is presented. A simple phase reduction algorithm is developed, which replaced an accurate phase shifter. Compared with other phase shift techniques, this method is insensitive to environmental vibration and air disturbance, has visible procedures and results allows the object to move slowly during the inspection procedure, does not need phase unwrapping, and has a quick image processing speed. As an application, this NDT technique is used to detect defects in composite materials and the resulting deformation phase gradient image shows a better visual effect than normal ESPI.

A New Nondestructive Testing (NDT): Torsion Test to Evaluate Compressive Strength in Concrete Structures

Abstract A new nondestructive test (NDT) for the in-situ compressive strength evaluation of concrete has been developed. Using a torque meter, the failure torsional moment is determined on a small cylinder formed in the structure. Test background, methodology, and results obtained in mortar and concrete are discussed. The effects of w-c ratio, particle shape, maximum size, and types of the coarse aggregates, test age, and curing conditions on the correlation relationship are also reported. Test results (up to 90 days) showed that correlation curves between compressive strength (fc) and ultimate torsional moment (Mt) depend mainly on the size, shape, and surface texture of the coarse aggregate.

Rotational magnetic flux sensor with neural network for non-destructive testing

A new non-destructive testing (NDT) method which utilizes rotational magnetic flux is presented. In this system, the magnitude and phase value are measured and used to obtain information about defects. These values include the information about the shape or position of an unknown defect. The neural network technique is employed for estimation of a defect shape. The experimental results show the validity of the authors' method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Non-Destructive Testing with Magnetic Sensor Using Rotational Magnetic Flux

This paper presents a new nondestructive testing (NDT) method which utilizes rotational magnetic flux. In conventional eddy current NDT, the magnetic sensor is driven by an ac or dc current. Consequently, the magnetic field generated in the magnetic material is aligned in a single direction. However, in order to estimate the shape or position of an unknown defect, a two-dimensional alternating magnetic flux density vector is necessary. An NDT system utilizing rotational magnetic flux is proposed. In this system, the magnitude and phase value are measured and used to obtain information about the defect.

回転磁束型磁気センサーによる磁気探傷

This paper presents a new non-destructive testing (NDT) method using rotational magnetic flux. In conventional eddy current NDT, the magnetic sensor has been driven by dc or alternative current. Therefore. the genarated magnetic field in the magnetic material is arranged in one direction. However, in order to estimate shape or position of an unknown defect, a two-dimensional alternating magnetic flux density vector is necessary. The NDT system using rotational magnetic flux is proposed. In this system, the magnitude and phase value are obtained as the signals of defect.

MAGNETIC PERTURBATION SCANNING A NEW NONDESTRUCTIVE TESTING METHOD

Naval Engineers JournalVolume 78, Issue 6 p. 1068-1072 MAGNETIC PERTURBATION SCANNING A NEW NONDESTRUCTIVE TESTING METHOD First published: December 1966 https://doi.org/10.1111/j.1559-3584.1966.tb04133.xAboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume78, Issue6December 1966Pages 1068-1072 RelatedInformation