Phased Array Ultrasonic Technique Research Articles

Effect of blind-bolt repair method on vibration and compression characteristics of delaminated composite aircraft panels

The paper investigates the validity and reliability of the blind-bolt repair method for repairing delaminated composite aircraft panels. The delaminated specimens are prepared by inserting Teflon films during the manufacturing process to simulate interlayer damage. Subsequently, these specimens are repaired using the blind-bolt method. Modal and uniaxial compression tests are conducted to quantitatively evaluate the natural frequency, mode shape and load-bearing strength of both delaminated and bolt-repaired specimens. Digital image correlation and ultrasonic phased array techniques are employed to characterize buckling instability and damage evolution of specimens. The results reveal that the natural frequency and compressive buckling strength of delaminated specimens significantly decrease. The mode shape also changes nonlinearly with the stiffness reduction. This variation is proportional to the size and the quantity of delaminations. The blind-bolt repair method effectively restores the vibration and mechanical properties of the delaminated composite structure by reconnecting separated sub-laminates. A repair tolerance of 20 mm–60 mm is recommended for a single blind-bolt. When the delamination length is 35 mm, the repair efficiency for the critical buckling load and the ultimate load is the highest, at 58.3% and 64.4%, respectively.

Integrity assessment of a crack inside a pressure vessel wall in RHPP “Bajina Bašta”

The goal of this research was to combine non-destructive test methods, specifically modern ultrasound testing techniques with numerical simulations via finite element method, to determine the risk of failure of a pressure vessel in the reversible hydropower plant “Bajina Bašta”. Using Phased Array Ultrasonic Technique and Time of Flight Diffraction technique, a crack with a length of 75 mm and depth of 20 mm was detected inside the pressure vessel wall, in the vertical welded joint. Based on the exact position and size of the crack, a numerical model was made in ABAQUS. Two models were made, with and without the crack, for comparison purposes. Since the obtained results did not show difference, it was decided to make another model, with different boundary conditions, providing a more realistic insight into the behaviour of the pressure vessel, which still remained in the safe zone.

Implementation of Non Destructive Testing and in-line monitoring techniques on extra-large structures printed with WAAM technology

Grade2XL is a European project funded by the H2020 program that gathers 21 academic and industrial partners. Started in March 2020 for 4 years, the principal objective is to print extra-large structures using the WAAM (Wire Arc Additive Manufacturing) method with a complete control of the fabrication process. Since WAAM is a relatively new technology for printing large specimens, it is important to develop quality assurance methods that can be used during the fabrication and once the structure has been built, which is the focus of CEA List in the project. Regarding methods applied built structures, CEA List has investigated Resonant Ultrasound Spectroscopy (RUS) for the material characterization and more specifically the evaluation of the elastic constants or more conventional ones for the inspection with phased-array ultrasonic techniques (PAUT) or eddy current (EC) for the detection of indications are implemented and optimised them for the inspection of the final structures. Concerning the development of in-line monitoring methods, CEA List has been working on laser Doppler vibrometry (LDV) and X-ray fluorescence (XRF) spectrometry, in order to get structural information during the printing but also detect the appearance of abnormal events and correlate them to the appearance of defects generated during the WAAM process. This proceeding presents the advantages of those methods for the inspection of extra-large structures made by WAAM and discusses the first results obtained in the framework of the project. Keywords: Additive Manufacturing, NDT, Imaging techniques, Eddy current, In-line monitoring, laser vibrometry, X-ray fluorescence spectrometry, Resonant Ultrasound Spectroscopy.

Quality verification of Cold spray protection of the weld root

Cold spray technology (CS) as an advanced surface treatment can also be applied in the field of energy. Depending on the type of spraying, the coating itself plays the role of protecting the surface from corrosion, abrasion and other operational influences. In the case of dissimilar metal welds (DMW), it can play the role of protection against stress corrosion cracking (SCC). The thickness of the applied spray can range from tens of microns to units of mm. The quality of NiCr and Ni protective coatings made by CS technology was tested by means of non-destructive (NDT) and destructive (DT) testing. NDT focused on measuring the attenuation of the ultrasonic signal, measuring the thickness of the applied coatings and the adhesion to the base material using pulsed echo (PEUT) and phased array (PAUT) ultrasonic testing techniques. Evaluation of the microstructure, porosity and corrosion stability of CS coatings before and after the salt spray test was performed metallographically.

Quality Control Using Ultrasonic Phased Array Inspection of Components Produced by Directed Energy Deposition in Ti6Al4V Alloy

Additive manufacturing (AM) is rapidly becoming a viable manufacturing method for industrial metallic parts. This is related to the benefits achieved, such as reducing material wastage, an increase in design freedom and weight savings. But, to guarantee the highquality of the components produced, the non-destructive methods of inspection need to be optimised or developed. In this study, a Ti6Al4V 3D coupon was produced by the Laser Wire Directed Energy Deposition process (w-DED-LB), in which artificial holes of different diameters simulating defects were machined. To validate the quality control method after production by means of Ultrasonic Phased Array Techniques, the component was inspected using the Gekko equipment from Eddyfi Technologies, through the methodologies of the phased-array conventional mode and the Total Focusing Method (TFM). The probe used was a 5L64-64X7-NW1-P-5-OM, with a 5.0 MHz frequency system with 64 elements, with dimensions of length 64 mm, width 7 mm, and pitch of 1.0 mm. The results obtained showed that the TFM mode provides better detection of the defects, resolution, and measurement capabilities when compared with the conventional phased array mode.

Compressive sensing of ultrasonic array data with full matrix capture in nozzle welds inspection

The phased array ultrasonic technique (PAUT) with full matrix capture (FMC) exhibits the advantages of high imaging accuracy and great defect characterization ability, which play important roles in the nondestructive testing of welded structures. To address the problem of a large amount of signal acquisition, storage, and transmission data in nozzle weld defect monitoring, a PAUT with an FMC data compression method based on compressive sensing (CS) was proposed. To accomplish this, the detection of nozzle welds using PAUT with FMC was performed by simulation and experiment, and the obtained FMC data were compressed and reconstructed. A suitable sparse representation was found dedicated to the FMC data of nozzle welds, and the reconstruction performance was compared between the greedy theory-based orthogonal matching pursuit (OMP) algorithm and the convex optimization theory-based basis pursuit (BP). Also, an empirical mode decomposition (EMD)-based intrinsic mode function (IMF) circular matrix was constructed to provide another idea for the construction of the sensing matrix. Although the experimental results were not able to reach the ideal effect in the simulation, the image was restored accurately with a small number of measured values, and flaw identification could be guaranteed, indicating that the CS algorithm can effectively improve the defect detection efficiency of the phased array.

Phased Array Ultrasonic Imaging Of Damage In CFRP Laminates Under Low-Velocity Impact

In the last few decades, fibre-reinforced composites have seen significant growth in use in aircraft and automotive structures because of their superior properties such as high specific strength and stiffness, good fatigue and wear tolerance. During operation, these structures are subjected to different loading conditions including impact which may cause damage to them. Damage caused by lowvelocity impacts is more severe since it is undetectable in general visual inspections but it may reduce structural integrity significantly. In this work behavior of CFRP laminates under low-velocity impact is investigated. The effect of the impact energy on the damage is studied for the different stacking sequences of CFRP laminates. Composite laminates are fabricated with different stacking sequences and tested with a drop weight impact testing machine under different impact energies. Phased array ultrasonic technique is used to investigate the damage configuration of impacted specimens. A comparative study on damage shape and size as a function of the impact energy is done for different stacking sequences.

First lamina hybridization of high performance CFRP with Kevlar fibers: Effect on impact behavior and nondestructive evaluation

The impact behavior of a carbon-Kevlar hybrid composite, widely used in sport car manufacturing, was evaluated. To highlight the hybridization effect, comparative analyses were performed with the basic CFRP laminate having the same lay-up. Tensile, bending and low velocity impact tests, followed by nondestructive inspections, highlighted that Kevlar first lamina hybridization leads to an increment in specific impact strength, up to 55%. To assess the most reliable technique to detect the impact damage, nondestructive evaluation was performed by pulsed thermography, phased array ultrasonic technique, computed tomography and digital radiography. Phased array ultrasonic technique can be considered the most appropriate technique.

Effect of SWCNT-Tuball Paper on the Lightning Strike Protection of CFRPs and Their Selected Mechanical Properties.

The main aim of this work was the investigation of the possibility of replacing the heavy metallic meshes applied onto the composite structure in airplanes for lightning strike protection with a thin film of Tuball single-wall carbon nanotubes in the form of ultra-light, conductive paper. The Tuball paper studied contained 75 wt.% or 90 wt.% of carbon nanotubes and was applied on the top of carbon fibre reinforced polymer before fabrication of flat panels. First, the electrical conductivity, impact resistance and thermo-mechanical properties of modified laminates were measured and compared with the reference values. Then, flat panels with selected Tuball paper, expanded copper foil and reference panels were fabricated for lightning strike tests. The effectiveness of lightning strike protection was evaluated by using the ultrasonic phased-array technique. It was found that the introduction of Tuball paper on the laminates surface improved both the surface and the volume electrical conductivity by 8800% and 300%, respectively. The impact resistance was tested in two directions, perpendicular and parallel to the carbon fibres, and the values increased by 9.8% and 44%, respectively. The dynamic thermo-mechanical analysis showed higher stiffness and a slight increase in glass transition temperature of the modified laminates. Ultrasonic investigation after lightning strike tests showed that the effectiveness of Tuball paper is comparable to expanded copper foil.

Inspection of transverse flaws for railways using phased array ultrasonic technique

AbstractRail monitoring is an important activity which aims to preserve the safety and availability of railways. According to statistics, the primary cause of railway accidents is due to transverse defects that occur in the rail head. These special defects develop generally in a plane orthogonal to the rail running direction. The detection of these defects is a priority to increase the safety of rail transportation. Rail control monitoring techniques mostly rely on infrared thermography, eddy currents, air-coupled acoustic sensors, and ultrasounds. The present research studies the rail diagnosis by means of a non-contact device. The focus is on ultrasonic based methods where excitation is generated by thermal elastic coupling following laser irradiation of the rail head. For the reception of echoes, a special ultrasound sensor was used. In order to sense defects, phased array elements, which use multiple transducers and electronic time delays, are used to increase and to focalise the signal intensity. Flaws that have a moderate extension are better detected by the proposed method than with laser irradiation consisting of a single spot.

CFRP를 이용한 탄소강 평판 보수시 위상배열초음파검사(PAUT) 기법에 관한 연구

본 연구는 복합소재(CFRP/GFRP)가 적층된 탄소강평판 내부의 인공 감육 부위에 대해 위상배열 초음파탐상검사(PAUT) 기법을 이용한 검사기술을 개발하기 위하여 수행되었다. 실험은 복합소재와 탄소강 모재계면의 Debonding 시편과 탄소강 모재부 감육시편을 제작한 후 PAUT 장비를 이용하여 시편의 결함부를 검출하고 분석하였다. 그 결과, 복합소재부와 탄소강 모재부에 대한 초음파 속도가 매우 상이함에도 불구하고 다양한 깊이와 직경의 감육부 결함이 정량적으로 평가되었으며 PAUT 기법의 적용가능성을 확인하였다.

The application of ultrasonic phased array technology in wind turbine blade defect detection system

Start The working environment of wind turbines is complex and harsh. If the early damage of blades is not found in time, it may develop into mechanical failure under bad working conditions. Once an accident occurs, the consequences will be serious. In this paper, we study the non-destructive testing of ultrasonic phased array technique in the application of wind turbine blade defect detection, and analysis all kinds of common defects of blade production stage. According to these defects, the corresponding test device is selected, and the fault library is accumulated through defect test blocks. The original data of blade ultrasonic detection were identified, compared and finally the defect type was determined.

Comparative Study on Using Ultrasonic Array-Based Techniques for Detection of Flaws in Thick and Attenuating Materials

This paper reports the influence of thickness and material attenuation on volumetric inspection using conventional and advanced ultrasonic array-based techniques through suitable examples. The sensitivity achieved in conventional phased array ultrasonic testing technique with focusing at specific depth using delay laws and advanced array-based techniques for simultaneous focusing at all depths such as Full Matrix Capture-Total Focusing Method and plane wave imaging-TFM are compared in the present study. Finally, experimental results are discussed for advanced ultrasonic array-based techniques for detection and characterization of a 4 mm through wall dimension vertical planar defect (simulating a lack of side wall fusion in a thick narrow gap weld) in a nickel base alloy forging having fine and coarse grains. The sensitivities and signal-to-noise ratio achieved in the different techniques are discussed in detail.

Bending residual strength of damaged Al foam sandwiches through UT and IRT analyses

In the present work, the effect of low-speed impact on the static residual strength of aluminum foam sandwiches having GFRP skins has been evaluated. Two different configurations have been considered, which differs both for thickness and layup used for the manufacturing of GFRP skins. The detection and the quantification of the damage induced by impact have exploited the potentiality of pulsed thermography and phased array ultrasonic techniques, which gives the possibility to provide synergistic and complementary information. Mechanical strength has been evaluated through three-point bending tests carried out on undamaged and damaged specimens. Static tests allowed also evaluating the failure mode of panels and the changes induced by the presence of a low-speed impact zone.

Evaluation of material degradation using phased array ultrasonic technique with full matrix capture

This paper presents a new approach based on phased array ultrasonic technique (PAUT) with full matrix capture (FMC) to effectively measure acoustic properties such as ultrasonic wave velocity and attenuation coefficient and to evaluate material degradation. This paper also proposes the use of PAUT with FMC, to simultaneously generate and detect ultrasonic waves such as longitudinal, shear, and Rayleigh waves in the material. A theoretical model is developed to derive the analytical solution of ultrasonic waves induced in the material by an ultrasonic phased array probe. Based on the theoretical prediction, experiments are carried out on AISI 316L stainless steel specimen of 3 mm thickness, and a 2D finite element model is built to verify the generation and detection of these waves. Furthermore, measurements of acoustic properties are carried out on the specimen using the proposed approach as well as the conventional ultrasonic testing (CUT) technique and their sensitivities are compared. The measurements of time-of-flight and back-wall echo amplitude are more accurate with the proposed approach than the CUT technique, which makes the former technique better than the latter for the evaluation of material degradation. Finally, experiments are performed on AISI 316L specimen degraded with different levels of tensile stress to verify the capability of PAUT with FMC. The results show that the velocities and attenuation coefficient increase with an increase in tensile stress until material fracture. This phenomenon is interpreted as resulting from microstructural changes such as dislocations during material degradation. From the experimental results, it is proposed that PAUT with FMC can potentially be used to evaluate early-stage materials degradation.

Experimental Investigation of Impactor Diameter Effect on Low-Velocity Impact Response of CFRP Laminates in a Drop-Weight Impact Event.

The present study delved into the effect of impactor diameter on low velocity impact response and damage characteristics of CFRP. Moreover, the phased array ultrasonic technique (PAUT) was adopted to identify the impact damages based on double-sided scanning. Low-velocity impact tests were carried out using three hemispherical impactors with different diameters. The relationship of impact response and impactor diameters was analyzed by ultrasonic C-scans and S-scans, combined with impact response parameters. Subsequently, the damage characteristics were assessed in terms of dent depth, delamination area and extension shape via the thickness, and the relationships between absorbed energy, impactor displacement, dent depth and delamination area were elucidated. As revealed from experiment results, double-sided PAUT is capable of representing the internal damage characteristics more accurately. Moreover, the impactor diameter slightly affects the impact response under small impact energy, whereas it significantly affects the impact response under large impact energy.

Ultrasonic Phased Array Techniques for Industrial Applications

Ultrasonic Phased Array Techniques for Industrial Applications

Phased array ultrasonic imaging using angle beam virtual source full matrix capture-total focusing method

Full matrix capture coupled with total focusing method (FMC-TFM) is one of the most advanced and popular phased array ultrasonic techniques used to achieve simultaneous focusing at all depths in a specimen. In case of conventional FMC-TFM technique, a single element is used for transmission that limits the transmitted energy. This leads to reduced sensitivity at larger depths particularly in attenuating materials such as austenitic alloys. An Angle Beam Virtual Source FMC (ABVSFMC) method is proposed in the present paper to enhance the sensitivity by increasing the transmitted energy with specific directivity. The methodology utilizes apertures of a few elements to obtain a diverging beam by focusing very near to the top surface (virtual source). Further, as a group of elements is used in transmission, a divergent beam with specific directivity can be achieved without using a wedge. In reception, all the available channels are used and an algorithm similar to the Total Focusing Method (TFM) is used to reconstruct the image. The methodology is demonstrated by imaging the tip diffracted signals obtained from slot type planar defects at various depths in the range of 25–175 mm in a 200 mm thick nickel base alloy forging.

Finite Element Analysis Model on Ultrasonic Phased Array Technique for Material Defect Time of Flight Diffraction Detection

In this study, the finite element method (FEM) for phased array technology in ultrasonic time of flight diffraction (TOFD) for the defect detection of two-dimensional (2-D) geometric materials was researched. The phased array technology generated the FEM model for the TOFD signal. We have established the finite element model by the FEM software ANSYS based on the ultrasonic mechanism about the defects and the phased array transducer. A plane strain elements have simulated the reflected signal of the defect. We can compare the error ratio between simulation and experiment by using the theoretical calculation value as the benchmark, and find the feasibility of the FEM detection.

Experimental and Numerical Investigation of Swirling Flow on Triple Elbow Pipe Layout

The secondary flow downstream of a triple elbow layout was studied experimentally and numerically to visualize the flow behavior under swirling inlet flow conditions. The inlet swirling condition was generated by a swirl generator, consisting of a rotary pipe and honeycomb assembly. The experiments were carried out in turbulent water flow condition at Reynolds number Re = 1 × 104 and inlet swirl intensity S = 1. Ultrasonic measurements were taken at four locations downstream of the third elbow. The two-dimensional velocity field of the flow field was measured using the phased array ultrasonic velocity profiler technique to evaluate the flow field with separation. Furthermore, a numerical simulation was performed and its results were compared with the experimental data. The numerical result was obtained by solving three-dimensional, Reynolds-averaged Navier-Stokes equations with the renormalization group k-ε turbulence model. The experimental results confirmed that the swirling flow condition modified the size of the separation region downstream of the third elbow. A qualitative comparison between the experimental and CFD simulation results of the averaged velocity field downstream of the third elbow showed similar tendency on reverse flow.