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Circular spiral coils (left) vs trapezoidal spiral ones (right). An axial defect may not be detected by a conventional circular or rectangular spiral coil where both trapezoidal spiral coils would.
Source publication
A novel Eddy Current (EC) probe configurations were developed to detect millimeter defects with any orientation on inner or outer pipe surfaces. The probes were designed and experimentally validated in different materials where the defects tested were identified with a high sensitivity and good signal-to-noise ratio.
Contexts in source publication
Context 1
... trapezoidal shape of the coils was chosen instead of conventional EC probes with planar circular spiral coils because they present a common problem which is the existence of a blind zone in the interface between two consecutive sensitive coils. In this zone, the detection of defects can become compromised as shown in Figure 1. A second linear array with an offset from the first array is needed to ensure that all the tangential positions of the pipe are covered by the coil. ...
Context 2
... trapezoidal geometry allows a greater spatial resolution when compared to other coil geometries having the same number of coils in one array. There is an Area of Exclusive Sensitivity (AES) in which the spatial resolution is dispersed as depicted in Figure 1. In circular coils this area is much larger, while with a trapezoidal geometry the AES significantly reduces, diminishing the uncertainty and increasing the spatial resolution. ...
Context 3
... circular coils this area is much larger, while with a trapezoidal geometry the AES significantly reduces, diminishing the uncertainty and increasing the spatial resolution. Axial defects can pass undetected when scanned between two consecutive circular coils as shown in Figure 1. The trapezoidal coils not only avoid this but can also detect it with both coils and, with the signal amplitude proportion, its tangential position can be enhanced. ...
Context 4
... section probe has a great potential of application on in use pipes where its end is difficult to reach. Five artificial flaws were made in the outer surface and there are depicted in Figure 10 and the characteristics shown in Table 2 ...
Context 5
... probe experimental results on the aluminium tube are displayed in Figure 11 using a frequency of 750 kHz. The five defects were detected, marked from A to E, displaying a very good signal to noise ratio. ...
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Citations
... Moreover, the probes can have different configurations and operation modes. The most common probe configurations include axisymmetric and helical coils, matrix coils and planar coils; the operation modes include absolute operation mode or differential operation mode [9]. Concerning the connection mode, the simplest method to connect absolute probes is with a resistive-inductive (RL) circuit. ...
Non-Destructive Testing (NDT) by Eddy Currents (EC) allows for determining material properties and detecting surface and subsurface defects that can harm structural integrity of electrically conductive components. However, despite being a standard technique and with many years of accumulated experience, there are some conditions where difficulties persist, such as detecting small defects in complex components with small dimensions and conicity (e.g. endodontic files used in a clinical environment).
This work aimed to design, numerically simulate, produce, and experimentally validate different configurations of EC probes for defect detection in endodontic files. For the application of NDTs, an artificial defect was introduced in the apical region of a commercial endodontic file with 4% taper and a tip’s diameter equal to 0.20 mm. The experimental results showed that most of the methodologies developed for the inspection of files through NDTs proved unable to detect the defective region, primarily due to its taper and the special Pauli paramagnetic properties of the NiTi alloy. Nevertheless, the customized EC toroidal probe operating in differential bridge mode could detect the artificial defect in the endodontic file. In parallel, a thermographic inspection of the defective instrument was made. As a result, it was possible to detect the defect by thermography, although with low Signal-to-Noise Ratio (SNR) due to its small dimensions.
Finally, commercial endodontic files manufactured by Electrical Discharge Machining (EDM) were tested and compared with the results obtained for conventional manufactured endodontic files. The endodontic instruments were placed in rotation in an experimental setup designed to simulate a root canal with a radius of curvature equal to 5 mm applied along a 45° angle. The experimental results showed that the latest generation of endodontic files, manufactured using EDM process, are significantly more resistant to fatigue fracture when compared to the Controlled Memory (CM) machined files.
... This technique may be used to detect defects or inconsistencies in the channels. Eddy current testing (ECT) uses alternating electrical currents to characterize and/or detect defects in electrically conductive materials [8,9]. It is based on the principle that when a conductor is subjected to an alternating magnetic field, eddy currents are generated within the material, which can be used to evaluate the material [10,11]. ...
Friction Stir Channeling (FSC) is a recent and innovative solid state manufacturing technology that allows, in a single pass, the opening of continuous internal channels in monolithic components and can be used in the mold and heat exchanger industries. However, the development of reliable Non-Destructive Testing (NDT) for the characterization of the channels is a major challenge. The focus of this work is the non-destructive characterization of micro channels, and the main goal was to experimentally validate which NDT techniques can be used to identify the presence of microchannels, their regularity along the section, and also their location, size, and path. Five NDT techniques were studied: digital radiology; eddy currents; ultrasounds; thermography; and dye penetrants. These techniques were applied to specimens with linear and curvilinear channels. The specimens were produced using tool pins with 0.5 mm diameter which obtained channels with 0.4 mm width and depths of 0.53 mm. Digital radiology and ultrasounds were effective in detecting channels regardless of its dimensions. Eddy currents did not allow to confirm the exclusive presence of the channels due to microstructural changes caused by the FSC process. Thermography using cold fluid injection was not successful in the channel’s characterization due to the extremely low flow. The dye penetrants confirmed the presence of the channels of all dimensions due to the liquid having traveled along the entire path of the curvilinear channel without reaching the surface.
... However, the production process through additive manufacturing (AM) introduces new defects, making it crucial to ensure their quality through non-destructive testing (NDT) methods [2]. Non-contact inspection techniques are increasingly important in a variety of industries due to their ability to detect defects quickly and efficiently without causing damage to the test specimen [3,4]. Another key factor concerns the ability to be automated. ...
The production of Polymer Matrix Composites (PMCs) through Additive Manufacturing (AM) presents new defects, and the detection of these is crucial for proper functioning. Non-destructive testing (NDT) techniques such as terahertz (THz), air-coupled ultrasounds, and active thermography are fast, automatable, non-invasive, and noncontact inspection methods. The aim of this study is to investigate the use of NDT techniques for detecting defects in PMCs produced by AM. Six samples were produced using polylactic acid (PLA) as the base material and reinforced with continuous fibers of Kevlar, glass, and carbon. Two types of samples were created: one with a full-thickness reinforcement defect in a specific area and the other with a partial reinforcement defect, with a layer of fibers missing in the same area. The samples were then tested using three NDT techniques: THz, non-contact ultrasonic, and active thermography. The results showed that THz was only able to detect the defect in the carbon fiber sample with full-thickness reinforcement, ultrasonic testing was able to detect the defects in Kevlar and carbon fiber samples with missing three layers of fibers, and active thermography was the most reliable technique, detecting all samples with missing three layers of fibers as well as partial reinforcement defects.
... One of the main advantages of using ECT is its ability to detect surface and sub-surface defects in conductive materials [69]. This makes it an attractive option for inspecting WAAM parts, which are typically made of metals such as aluminum, steel, and titanium. ...
... One solution to these issues is the use of printed circuit board (PCB) technology the production of eddy current probes [69]. PCBs offer a number of advantages o manually wound probes, including a high degree of repeatability and reproducibility well as the ability to incorporate multiple layers and other advanced features. ...
... One solution to these issues is the use of printed circuit board (PCB) technology for the production of eddy current probes [69]. PCBs offer a number of advantages over manually wound probes, including a high degree of repeatability and reproducibility, as well as the ability to incorporate multiple layers and other advanced features. ...
The wire and arc additive manufacturing (WAAM) process enables the creation and repair of complex structures based on the successive deposition of fed metal in the form of a wire that is fused with an electric arc and then solidifies. The high number of depositions required to create or repair parts increases the likelihood of defect formation. If these are reliably detected during manufacturing, timely correction is possible. However, high temperatures and surface irregularity make inspection difficult. Furthermore, depending on the size, morphology, and location of the
defect, the part can be rejected. Recent studies have shown that non-destructive testing (NDT) based on different physical phenomena for the timely, reliable, and customized detection of defects can significantly reduce the rejection rate and allow in-line repair, which consequently reduces waste and rework. This paper presents the latest developments in NDT for WAAM and its limitations and potential.
... Components such as steam transportation pipelines must withstand high temperatures above 300 • C, requiring adapted in-service inspection and condition monitoring methods. There are several solutions for pipe inspection [4], but few application examples can be found for when high temperature conditions apply and where customized equipment is required [5][6][7][8]. ...
This paper presents an automated Non-Destructive Testing (NDT) system for the inservice
inspection of orbital welds on tubular components operating at temperatures as high as
200 ºC. The combination of two different NDT methods and respective inspection systems is here
proposed to cover the detection of all potential defective weld conditions. The proposed NDT system
combines ultrasounds and Eddy current techniques with dedicated approaches for dealing with high
temperature conditions. Phased array ultrasound was employed, searching for volumetric defects
within the weld bead volume while Eddy currents were used to look for surface and sub-surface
cracks. The results from the phased array ultrasound results showed the effectiveness of the cooling
mechanisms and that temperature effects on sound attenuation can be easily compensated for up
to 200 ºC. The Eddy current results showed almost no influence when temperatures were raised up
to 300 ºC.
... Currently, continuous and real-time SHM systems are assisted with the classical Non-Destructive Testing (NDT) techniques, such as ultrasounds [2], X-rays [3], infrared thermography [4], holographic interferometry [5], eddy currents [6,7], and terahertz [8], among others, which require highly specialised labour along with expensive procedures. Furthermore, periodic inspections, which are the most traditional form of structural monitoring, are unable to provide any information on accidents and failures that occur between two successive revisions. ...
... Damage changes materials' conductivity, thereby affecting eddy currents and modifying the secondary magnetic field. These techniques can be used to measure electrical conductivities and magnetic permeabilities, detect defects, detect and analyse corrosion in the material, and measure coating thicknesses [6,7,20,21,45]. ...
Sensing Technology (ST) plays a key role in Structural Health-Monitoring (SHM) systems. ST focuses on developing sensors, sensory systems, or smart materials that monitor a wide variety of materials’ properties aiming to create smart structures and smart materials, using Embedded Sensors (ESs), and enabling continuous and permanent measurements of their structural integrity. The integration of ESs is limited to the processing technology used to embed the sensor due to its high-temperature sensitivity and the possibility of damage during its insertion into the structure. In addition, the technological process selection is dependent on the base material’s composition, which comprises either metallic or composite parts. The selection of smart sensors or the technology underlying them is fundamental to the monitoring mode. This paper presents a critical review of the fundaments and applications of sensing technologies for SHM systems employing ESs, focusing on their actual developments and innovation, as well as analysing the challenges that these technologies present, in order to build a path that allows for a connected world through distributed measurement systems.
... Currently, continuous and real-time SHM are assisted with the classical Non-Destructive Testing (NDT) techniques, such as ultrasounds [2], X-ray [3], infrared thermography [4], holographic interferometry [5], eddy currents [6,7], terahertz [8], among others, which require highly specialized labour along with expensive procedures. Furthermore, periodic inspections, that are the most traditional form of structural monitoring, are unable to provide any information on accidents and failures that occur between two successive revisions. ...
... Damage changes materials conductivity affecting eddy currents and modifying the secondary magnetic field. These techniques can be used to measure electrical conductivities and magnetic permeabilities, detect defects, detect and analyse corrosion in the material, and measure coating thicknesses [6,7,20,21,46]. ...
Sensing Technology (ST) plays a key role in Structural Health Monitoring (SHM) systems. ST focuses on developing sensors, sensory systems or smart materials that monitor a wide variety of materials properties aiming to create smart structures and smart materials, using Embedded Sensors (ESs), and allowing continuous and permanent measurements of the structural integrity. The integration of ESs is limited to the processing technology to embed the sensor due to its high-temperature sensitivity and the possibility of damage during its insertion into the structure. In addition, the technological process selection is dependent on the base material composition, either metallic or composite parts. The selection of smart sensors or the technology underlying them is fundamental to the monitoring mode. This paper presents a critical review of the fundaments and applications of sensing technologies for SHM employing ESs, focusing on the actual developments and innovation of these, as well as analysing the challenges that these technologies present, to build a path that allows a connected world through distributed measurement systems.
... Together with those, variations of the sensing coils are included to increase the ability to readout the EC modifications. The literature reports many examples of ECT probes employing complex geometries including: circular spiral coils [3][4][5], parallelogram and rectangle coils [6,7], double-excitation coils [8,9], d-shaped differential coils [10,11], rosette-like windings [12][13][14], meandering windings [15,16], gradient windings [17], mesh-windings [18], fractal windings [19,20], rotating magnetic fields [21][22][23], amongst many other. ...
The orientation of the induced eddy currents is an important parameter for eddy currents testing probes used in Non-destructive Testing (NDT). In general, the eddy currents distribution is chosen to promote path changes when a defect is present, being preferentially set perpendicular to the target defects orientation. This usually requires complex geometry excitation coils and the consequent production difficulties. A new approach on the design of eddy currents testing probes is here presented, employing high magnetic permeability pattern substrates to shape the eddy currents distribution. This simulated and experimentally validated approach shift’s the excitation coils production complexity to the magnetic substrate, whose production can be easily tackled with additive manufacturing technologies.
... Industrial inline quality control systems are highly desired to answer laser-brazed welding quality requirements and overcome offline inspection efficiency limitations [8][9][10][11][12][13]. For this purpose, several commercially available NDT inspection technologies may be considered. ...
An innovative pilot installation and eddy current testing (ECT) inspection system for laser-brazed joints is presented. The proposed system detects both surface and sub-surface welding defects operating autonomously and integrated with a robotized arm. Customized eddy current probes were designed and experimentally validated detecting pore defects with 0.13 mm diameter and sub-surface defects buried 1 mm deep. The integration of the system and the manufacturing process towards an Industry 4.0 quality control paradigm is also discussed.
... Despite some low conductivity polymeric composite parts may be inspected without contact by eddy currents [5,6], a faster and an image producer NDT technique should be target for such kind of inspections [1,[7][8][9]. ...
This paper presents an innovative variant of the Active Transient Thermography (ATT), designated Double Active Transient Thermography (DATT), where the component inspected is excited by one heat and one cold sources. The goal is to speed up and improve the temperature contrast, namely for polymer matrix composites parts produced by Additive Manufacturing. Finite element analysis of the thermal phenomena involved in DATT were performed to assist the definition of the experimental setups and confirm the high potential of the technique. Experimental results prove that the introduction of the cold flow increases the temperature contrast up to 100 %, comparing with ATT, and mid thickness defects are the ones that benefits the most from this technique. Therefore, the improvement of the inspection procedure is achieved by two means: enhancing the thermal contrast of the defects, and/or anticipating the instant when the maximum contrasts occur.
