Development Of Non-destructive Testing Research Articles

Non-Destructive Testing Inspection for Metal Components Produced Using Wire and Arc Additive Manufacturing

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.

Development of non-destructive testing (NDT) technique for HIPed interface by Compton scattering X-ray spectroscopy

• HIPed interface of F82H steel was analyzed using high energy X-rays (115.56 keV). • The analysis revealed the presence of SiO x and TaO x at the HIP interface and W accumulation near the HIP interface. • The high energy X-ray spectra can be a non-destructive testing (NDT) technique for a HIPed interface of F82H steel. High energy X-rays (115.56 keV) were used to measure the HIPed interface of F82H steel. The X-ray energy spectra of the samples were analyzed focusing on W and Ta fluorescence X-rays, Compton scattering and elastic scattering X-rays. The results suggest the presence of SiO x and TaO x at the HIP interface and the accumulation of W near the HIP interface. These results indicate that high-energy X-ray spectrum analysis can be a non-destructive testing technique (NDT) to evaluate precipitates at the HIP interface of F82H steel.

Transient Acoustic Wave Propagation Problems in Multilayered Pavement Using a Time Discontinuous Galerkin Finite Element Method

This paper presents a modified time discontinuous Galerkin finite element method (MDGFEM) for transient acoustic wave propagation problem of multilayered pavement. The pavement consists of cement concrete pavement, semi-rigid base, and natural soil. The multilayered pavement is modeled as poroelastic mediums and assumed to be water-saturated. The well-known generalized Biot’s theory is employed to describe the wave propagation problem. The present MDGFEM, based on the artificial damping scheme, employs the Hermite (P3) functions and the linear (P1) shape functions to interpolate the global nodal vector and its temporal gradient respectively in a time step. Numerical results of 1D and 2D problems show that the MDGFEM can filter out spurious numerical oscillations before and after waves, boundaries of the hole, and the interface between the layers more effectively for the propagation of acoustic waves in multilayered pavement. Compared with widely used time-continuous methods such as the Newmark method, the method proposed in this paper presents better capabilities in the fluid–structure interaction behavior of multilayer pavements and provides a more accurate solution, which contributes to the further development of non-destructive testing of multilayer pavement structures.

Structural health assessment techniques for in-service timber poles

Timber utility poles are widely used in power distribution and telecommunication networks. Wood is subjected to deterioration with time, and routine condition assessment works are carried out for in-service timber poles to identify potential defects and their extent for renewal planning. These condition assessment methods need to be reliable and accurate to represent the actual status of poles. Incorrect interpretations regarding the structural integrity of poles may lead to premature pole replacements due to misdiagnosed defects or pole failures due to overlooked defects. The aim of this paper is to provide a state-of-the-art review of various condition assessment techniques for in-service timber poles. The paper reviews the conventional pole inspection methods, semi-destructive techniques and recent developments in non-destructive testing (NDT) techniques. The performance of these techniques is compared and their relative advantages and shortcomings are discussed. Further, the timber deterioration modelling techniques are outlined along with the probabilistic approaches for the condition assessment of timber poles. Finally, potential research gaps that need to be addressed in the future to overcome the issues related to the condition assessment of timber poles are discussed.

Experimental Research on the Detection of Inner Defects of Bellows Based on Ground Penetrating Radar

With the development of science and technology, the development of non-destructive testing is more and more mature, and Ground penetrating radar (GPR) has been widely used because of its advantages of fast detection speed, continuous detection process, high resolution, convenient and flexible operation, and low detection cost. However, it is rarely used in the detection of bellows defects. Therefore, the validity and applicability of GPR needs to be verified for detecting grouting defects of bellows in box girders. The box girder slab is simulated by placing bellows in the reinforced concrete slab. Ground penetrating radar (GPR) profiling method is used to detect grouting defects of bellows in reinforced concrete slabs. The two-dimensional and three-dimensional images of ground penetrating radar detection results are analysed. The results show that: Combining the X and Y direction detection images of ground penetrating radar, the specific location of the cavity defects in the bellows can be known. The three-dimensional slice of ground penetrating radar can roughly reflect the size of the internal cavity defect in the bellows. The two-dimensional and three-dimensional images of ground penetrating radar (GPR) can verify each other and complement each other when detecting the internal void defects of reinforced concrete plate corrugated pipe, which is helpful to grasp the internal defects of corrugated pipe in depth. The experiment proves that the ground penetrating radar is effective and promising for the detection of reinforced concrete plate bellows, and can be used for the detection of box girders in bridge engineering.

Analysis of Guided Wave Propagation in a Multi-Layered Structure in View of Structural Health Monitoring

Guided waves (GW) are of great interest for non-destructive testing (NDT) and structural health monitoring (SHM) of engineering structures such as for oil and gas pipelines, rails, aircraft components, adhesive bonds and possibly much more. Development of a technique based on GWs requires careful understanding obtained through modelling and analysis of wave propagation and mode-damage interaction due to the dispersion and multimodal character of GWs. The Scaled Boundary Finite Element Method (SBFEM) is a suitable numerical approach for this purpose allowing calculation of dispersion curves, mode shapes and GW propagation analysis. In this article, the SBFEM is used to analyse wave propagation in a plate consisting of an isotropic aluminium layer bonded as a hybrid to an anisotropic carbon fibre reinforced plastics layer. This hybrid composite corresponds to one of those considered in a Type III composite pressure vessel used for storing gases, e.g., hydrogen in automotive and aerospace applications. The results show that most of the wave energy can be concentrated in a certain layer depending on the mode used, and by that damage present in this layer can be detected. The results obtained help to understand the wave propagation in multi-layered structures and are important for further development of NDT and SHM for engineering structures consisting of multiple layers.

Non-destructive testing for wire + arc additive manufacturing of aluminium parts

Wire + Arc Additive Manufacturing (WAAM) has already proven to be successful for the production of large metal parts. However, there are still no specific standards available to label the quality requirements of the parts produced by WAAM and this is preventing a more widespread adoption of the technique.A crucial step towards the quality assurance of WAAM parts will be the development of Non-Destructive Testing (NDT) systems capable of identifying defects while parts are being produced. In this regard, Eddy Current Testing (ECT) can play a significant role, by allowing the inspection of both ferromagnetic and non-ferromagnetic materials, with high speeds and without contact with the material surface. The limitation here is that commercial ECT targets only the inspection of surface and subsurface defects.This study is focused on the development of a NDT system which includes customized ECT probes for the inline layer-by-layer detection of defects in aluminium WAAM samples. Results revealed that the developed EC probes were able to locate artificial defects: at depths up to 5 mm; with a thickness as small as 350 μm; with the probe up to 5 mm away from the inspected sample surface.The developed ECT probes proved to surpass the limitation of commercial ones. Also, these probes were able to overcome the limitations caused by the surface roughness of the samples and the high temperatures involved in the deposition process. These preliminary results represent an important step for the development of NDT systems for WAAM.

Experimental investigation by Laser Ultrasonics for train wheelset flaw detection

The transport safety is a key factor in the rail field and to ensure it the monitoring of train components structural integrity must be performed regularly and following strict regulations. Consequently, the development of Non-Destructive Testing (NDT) procedures is a topic of great interest and impact, it aiming at the early identification of cracks and inhomogeneities on train axle and wheels which propagation can causes faults and accidents undermining the passenger and crew safety. Ultrasound based nondestructive testing is currently applied in ordinary maintenance procedures, although they are applied to axle and wheels dismounted from the train wheelset. In fact, the technique requires ultrasonic probes to be in contact with the object under test and therefore the fretting surface between wheel and axle, where fatigue phenomenon induces cracks enucleation and propagation, cannot be monitored. The possibility of applying NDT systems to the whole wheelset, without dismounting it in its components, will allow drastically reducing the inspection time and increasing the inspection frequency. The present paper proposes a feasibility study for the development of a Laser-Ultrasonic Testing (LUT) procedure to improve performances of train wheelset ultrasonic inspection. The method exploits one or an array of air-coupled ultrasonic probes, which detects ultrasonic waves generated by a high-energy pulsed laser. Thanks to the non-contact nature of both the response measurement sensor and the excitation system, the experimental set-up is extremely flexible and it allows extremely speeding up the inspection time.

Comparative analysis on thermal non-destructive testing imagery applying Candid Covariance-Free Incremental Principal Component Thermography (CCIPCT)

Thermal and infrared imagery creates considerable developments in Non-Destructive Testing (NDT) area. Here, a thermography method for NDT specimens inspection is addressed by applying a technique for computation of eigen-decomposition which refers as Candid Covariance-Free Incremental Principal Component Thermography (CCIPCT). The proposed approach uses a shorter computational alternative to estimate covariance matrix and Singular Value Decomposition (SVD) to obtain the result of Principal Component Thermography (PCT) and ultimately segments the defects in the specimens applying color based K-medoids clustering approach. The problem of computational expenses for high-dimensional thermal image acquisition is also investigated. Three types of specimens (CFRP, Plexiglas and Aluminium) have been used for comparative benchmarking. The results conclusively indicate the promising performance and demonstrate a confirmation for the outlined properties.

Nondestructive testing in microfabrication using bacteria

Micromanufacturing has increased rapidly at scientific, technological and industrial levels. However, this evolution has not been followed by a parallel development of Non Destructive Testing (NDT) techniques. The available techniques are, generally, unable to detect microdefects. In this work, two types of microgeometries were produced by Micro Powder Injection Molding (μPIM) of stainless steel AISI316L: specimens for tensile tests (simple geometry) and microscrews (complex geometry). During the process optimization, different injection conditions of temperature and pressure were tested, as well as various temperatures for thermal debinding and sintering. Throughout the process, detectable and undetectable defects by NDT techniques were produced, which were used in the assays to assess the role of bacteria in the detection of defects. After adding bacterial suspensions of Staphylococcus aureus or Rhodococcus erythropolis cells, the microcomponents were subjected to magnetic or electric fields to facilitate mobility of bacteria towards the defects. This new methodology to detect defects produced during microfabrication can be a good solution for inspection of microdefects.

Nondestructive Testing of the Wire Rope Fault Detection

With the development of nondestructive testing (NDT) technology for wire ropes, various detection methods are constantly refined and improved. The primary and representative NDT methods are suitable for the detection of wire ropes including manual inspection, acoustic emission method,acoustic-ultrasonic method,eddy current method,electromagnetic method and metal magnetic memory method. Meanwhile, the research results of our laboratory based on the theory of the magnetic flux leakage to detect wire rope’s fault detection will be displayed. Through comparisons of methods’ merits and weaknesses,it also has brought forward the new trends about adopting metal magnetic memory to predict the lifetime of the steel wire ropes,which has greater value in theory and application for improving the precise detection of the in-service ropes.

Determination of the Embedded Lengths of Electricity Timber Poles Utilising Flexural Wave Generated From impactí

Round timbers are extensively used as utility poles in Australia for electricity distribution and communication. Lack of information on their conditions results in great difficulties on asset management for industries. Despite the development of various non-destructive testing (NDT) techniques for evaluating the condition of piles, few NDTs are reported for applications on timber poles. This paper addresses challenges and issues on development of NDTs for condition assessment and embedded length of timber poles. For this paper, it is mainly focusing on determining the embedded length of the pole considering loss of the sufficient embedment length is a main factor compromising capacity and safety of timber poles. Since it is impractical for generating longitudinal waves by impacting from the top of poles, utilising flexural wave from side impact on poles becomes attractive. However, the flexural wave is known by its highly dispersive nature. In this paper, one dimensional wave theory, guided wave theory and advanced signal processing techniques have been introduced in order to provide a solution for the problem. Two signal processing techniques, namely short kernel method and continuous wavelet transform, have been investigated for processing flexural wave signals to evaluate wave velocity and embedment length of timber poles in service.

Determination of the embedded lengths of electricity timber poles utilising flexural wave generated from impacts

Round timbers are extensively used as utility poles in Australia for electricity distribution and communication. Lack of information on their conditions results in great difficulties on asset management for industries. Despite the development of various non-destructive testing (NDT) techniques for evaluating the condition of piles, few NDTs are reported for applications on timber poles. This paper addresses challenges and issues on development of NDTs for condition assessment and embedded length of timber poles. For this paper, it is mainly focusing on determining the embedded length of the pole considering loss of the sufficient embedment length is a main factor compromising capacity and safety of timber poles. Since it is impractical for generating longitudinal waves by impacting from the top of poles, utilising flexural wave from side impact on poles becomes attractive. However, the flexural wave is known by its highly dispersive nature. In this paper, one dimensional wave theory, guided wave theory and advanced signal processing techniques have been introduced in order to provide a solution for the problem. Two signal processing techniques, namely short kernel method and continuous wavelet transform, have been investigated for processing flexural wave signals to evaluate wave velocity and embedment length of timber poles in service.

Preliminary Practice of Cloud Non-destructive Testing

Based on the progress of cloud computing technology and the actual situation of the development of nondestructive testing(NDT) technology, some useful exploration and practice are made in the development and application of the integrated technology of cloud non-destructive testing(CNDT). The principle of CNDT is that all the data collected by sensors/transducers are sent into cloud-side, where the data to be analyzed, stored, processed, evaluated, information forecasted and fed back; the cloud-side bringing together a series of hardware and software resources of nondestructive testing technology, is a cloud computing services platform obeyed by related nondestructive testing standards and regulations. The client-side can share all the resources in the cloud and perform remote control and information sharing in the detection process, enjoy the convenient service and high efficiency brought by the cloud detection. An established simulation platform of CNDT is introduced. It uses X3 electromagnetic detection prototype customer-side / U3 ultrasonic detection prototype client-side. And there are two cloud service nodes / centers established in Xiamen and Beijing respectively. Taking advantage of this CNDT model, some main aspects, such as the superiority, technical points of CNDT and it's further development direction are discussed and demonstrated.

Special Issue on Nondestructive Testing in Civil Engineering

This special issue of the Journal of Infrastructure Systems aims to provide an overview on advances of advanced nondestructive testing (NDT) applied to civil engineering structures. Indeed, a stage has been reached in which a substantial part of the infrastructure is entering a critical age. Dams, bridges, tunnels, pavements, and nuclear power plants require sustainable maintenance to qualify for extension of their service life in good condition and safely with appropriate service level. NDT methods have their places aside more widespread visual inspections and destructive tests within this process even though few standardized procedures exist. Because of their nonintrusive nature, NDT methods will play a prominent role in the future as more and more challenges specific to civil engineering problems, such as very large investigation zones and low cost requirements, have recently started to be tackled by researchers and companies involved in this field (automation, imaging, optimized data acquisition procedures, signal processing, and miniaturization of the equipment). Today, a wide range of NDT methods are available, including electromagnetic methods, ultrasonic methods, electrical methods, optical methods, eddy current, infrared thermography, and gammagraphy. A combination of several methods is often judicious taking into account that, on the one hand, the structures surveyed are often complex and in an open varying environment and that, on the other hand, NDT observables are usually not in direct link with engineering information needs (porosity, density, residual stress, and bounding). NDT development is ineluctable but should rely on an improved understanding of its underlying physical principles. Also, standards, education, and training need to be addressed. Nondestructive evaluation also concerns structural health monitoring with the design of cost efficient permanent instrumentations to survey modifications over time and space, not to mention the use of NDT data as input and output controls for residual time life prediction models. Because of previous international symposia on NDT in civil engineering, the interest in such techniques has grown, induced by an increase in their confidence, reliability, and user-friendliness. Nevertheless, some elements have to be improved, including their cost effectiveness through high acquisition rates, and the knowledge of the links between ND measurements and the durability indicators of the surveyed structures. Thus, the following papers highlight some particular results presented during the International Symposium on NDT in Civil Engineering (NDTCE’09), coorganized in Nantes, France, by IFSTTAR (former LCPC), the Research Institute in Civil and Mechanical Engineering (UMR CNRS GeM—Nantes Univ.) and COFREND (the French Association for Nondestructive Testing). The first paper by Kruschwitz et al. is on the application of spectral induced polarization (SIP), a well-known test method in geophysics on flooded masonry. Gucunski et al. propose a three-dimensional approach by using the Impact-Echo technique to survey a bridge deck. The associated interpretation methodology allows both the overall assessment of the condition of the deck and the identification of deteriorated zones of the deck for repair or rehabilitation. In the next paper, Felicetti tends to limit the destructive approach by using the analysis of cores for the assessment of deteriorated cover-concretes, although, taking into account the information from drilling monitoring. Then a small hole realized by a hammer-drilling method gives faster and reliable information of the variability of the mechanical properties versus depth. The fourth paper (Arosio et al.) deals with radar and sonic NDT techniques used for the quality control of concrete masonries. For that, an automatic specific procedure has been designed, and it tested as well on laboratory test structures as on-site. The last paper (Pinto et al.) is devoted to the determination of load-deflection curves of as-built drilled shafts of a case study. The testing program consisted of monitoring accelerations generated at the top of the shaft by means of a dynamic-force transducer. A numerical approach has been developed to extrapolate the load-deflection curve into the service load range, thus defining load-deflection curves.

Developments in NDT for Detecting Imperfections in Friction Stir Welds in Aluminium Alloys

Friction stir welding (FSW) has dramatically changed how aluminium alloys can be welded. The quality of FS welds is usually excellent, but some imperfections periodically occur. The geometry, location, and microstructural nature of these imperfections bear no resemblance to the imperfections typically found in aluminium fusion welds. Consequently, it has been difficult to identify FS weld imperfections with common non-destructive testing (NDT) techniques. Therefore, further development of NDT techniques must be done to enable the detection of FS weld imperfections. This paper presents an integrated, on-line, NDT inspection system for FS welds, which employs a data fusion algorithm with fuzzy logic and fuzzy inference functions. It works by analyzing complementary and redundant data acquired from several NDT techniques (ultrasonic, Time of Flight Diffraction (ToFD), and eddy currents) to generate a synergistic effect that is used by the software to improve the confidence of detecting imperfections. The system was tested on friction stir welded AA5083-H111 specimens. The results indicate that by combining the output from various NDT processes, an improvement in finding imperfections can be obtained compared to using each NDT process individually. The methodology implemented in the QNDT_FSW system has given good results and improved reliability in the NDT of friction stir welds.

Briefing: Sounding it out—advances in ultrasonic testing

A new generation of ultrasonic equipment could enable us to ‘see’ reinforcing bars in concrete without even touching the surface. Phil Purnell and Dave Hutchins of Warwick University report on the latest developments in non-destructive testing.

Sounding it out?advances in ultrasonic testing

A new generation of ultrasonic equipment could enable us to ‘see’ reinforcing bars in concrete without even touching the surface. Phil Purnell and Dave Hutchins of Warwick University report on the latest developments in non-destructive testing.

Propagation of Pressure Waves Inside a Fluid Channel with an irregular Floor

The BEM has been used to compute the variations in the pressure field caused when a dilatational point load is placed inside a confined fluid channel. The channel was assumed to be filled with a homogeneous fluid and the presence of irregularities in its floor was considered. The width of the channel was fixed, and the influence of the walls was analyzed. This paper extends previous work by the authors1,2 in which the fluid channel was considered to have infinite width. The Green's functions are defined in the frequency domain. They are obtained by superposing virtual acoustic sources, combined so as to generate the boundary conditions of both the free surface of the channel and the rigid surfaces of the floor and side walls. The responses in the time domain are obtained by means of Fourier transforms, making use of complex frequencies. The main features and spectral representation of the signals scattered by irregular floors are then described and used to elucidate some important aspects of wave acoustics, which may provide the basis for the development of non-destructive testing and imaging methods.

ACOUSTIC SCATTERING FROM A 2-D FLUID WAVEGUIDE WITH AN IRREGULAR FLOOR VIA THE BEM

This work focuses on the way the pressure field generated by a dilatational load changes inside a channel waveguide filled with a homogeneous fluid, in the presence of an irregular floor. The problem is solved in the frequency domain using the boundary element method. The Green's functions used are obtained by superposing virtual acoustic sources defined so as to generate the free or rigid surfaces of the fluid channel. The responses in the time domain are obtained by means of Fourier transforms, using complex frequencies. Irregular floors of varying sizes are modeled. The main features and spectral representation of the signals scattered by these inclusions are described. They are used to elucidate the most important aspect of wave acoustics, which can be used as the basis for the development of nondestructive testing and imaging methods.