Phased Array Ultrasonic Technique Research Articles

Неразрушающий контроль углепластиков на наличие несплошностей с использованием ультразвуковых фазированных решеток

Неразрушающий контроль углепластиков на наличие несплошностей с использованием ультразвуковых фазированных решеток

Non-destructive Testing of Welds in Gas Pipelines Repairs with Phased Array Ultrasonic Technique

The work deals with non-destructive ultrasonic testing of butt and circumferential fillet welds in the repairing of gas pipelines. The new ultrasonic technique Phased Array was used for testing. The article compared the results of Phased Array ultrasonic inspection to X-ray inspection. Experimental samples were taken from real gas pipelines' repairs. It is a circumferential butt joint connecting 2 gas pipelines and 2 other types of circumferential fillet welds occurring during repairs of gas pipelines with pressure steel and steel patch. Experimental testing was conducted on ultrasonic flaw detector OmniScan MX2 by Olympus. Indications of defects in the weld joints obtained by ultrasonic testing are corresponding with the experimental results of X-ray inspection. Experimental results provided information for proposal of manufacture of artificial defects in these samples.

Steam generator small bore piping socket weld inspection using the phased array ultrasonic technique

As nuclear power plants age, the likelihood of failures in the small bore piping used in those plants caused by exposure to mechanical vibrations during plant operations increases. While small bore piping failures rarely cause plant shutdown, the management of small piping has been a keen area of interest since their repair or maintenance requires a reactor trip. Steam generator (SG) drain pipe socket welds are small diameter piping connections (nominal pipe schedule 3–4 inches) susceptible to mechanical vibration. SG drain pipe socket weld failures have caused coolant leakage. Therefore, more reliable inspection technologies for small bore piping need to be developed to detect problems at an early stage and prevent pipe failures. This research aims to improve the reliability and accuracy of small bore piping inspections through the design, manufacture and application of a new phased array ultrasonic testing technique and inspection system for SG drain line socket welds.

Ultrasonic phased array techniques for composite material evaluation

The increasing rate of composite materials usage in the industries and researches implies finding the suitable method for testing and evaluation of composite materials. The composites are susceptible to flaws during production and the inspection costs suggest the use of NDT methods. Non-destructive testing is an appropriate method to detect the flaws and anomalies in the materials, however, due to an-isotropic structure of the composite materials, it is required to modify the techniques to find the most appropriate and accurate process for detecting flaws and anomalies in composite materials. The objective of this paper is to evaluate the feasibility and accuracy of nondestructive testing methods with emphasis on ultrasonic phased array technique for the integrity and structural evaluation of composite materials. In this approach three different composite samples were used for testing including one carbon fiber and two glass fiber samples. ultrasound phased array technique evaluated to perform the testing on the composite materials to find the appropriate method and procedure to apply ultrasound phased array techniques on composite materials.

원전 소구경 배관 소켓용접부 위상배열 초음파검사 기술 개발

소구경 배관 용접부 손상은 원자력발전소에서 빈번하게 발생되고 있는 문제이며, 이러한 손상은 보수를 위한 불시정지를 야기하고 결과적으로 발전소에 경제적인 손실을 초래한다. 따라서 소켓용접부의 제작결함 검출과 초기 성장 결함의 검출은 매우 중요하다고 할 수 있다. 지금까지 해당부위에 대한 검사는 ASME Code Section XI 요건에 의하여 표면검사를 적용하여 왔으나 강화검사로 체적검사기법인 초음파검사를 병행하여 수행하고 있다. 그러나 가동중에 발생되는 피로균열을 검출하기 위하여 적용되고 있는 일반 수동 초음파검사는 소켓용접부의 접근성과 초음파 탐촉자의 접촉 문제 등으로 인하여 검사 결과의 신뢰성에 문제가 있어 왔다. 본 연구에서는 위상배열 초음파검사 기술을 적용하여 소구경 배관 소켓용접부의 검사 신뢰성과 속도를 향상하고자 하였다. 이를 위하여 소구경 배관 소켓용접부 검사를 위한 3.5 MHz 위상배열 초음파 탐촉자를 제작하고 탐촉자의 접촉 조건과 일정한 신호 품질을 유지하기 위하여 수동 엔코더 스캐너를 개발하였다. 또한 검사 시스템을 구성하고 현장 검사를 위한 절차서도 개발하였다. Failure of small bore piping welds is a recurring problem at nuclear power plants. And the socket weld cracking in small bore piping has caused unplanned plant shutdowns for repair and high economic impact on the plants. Consequently, early crack detection, including the detection of manufacturing defects, is of the utmost importance. Until now, the surface inspection methods has been applied according to ASME Section XI requirements. But the ultrasonic inspection as a volumetric method is also applying to enforce the inspection requirement. However, the conventional manual ultrasonic inspection techniques are used to detect service induced fatigue cracks. And there was uncertainty on manual ultrasonic inspection because of limited access to the welds and difficulties with contact between the ultrasonic probe and the OD(outer diameter) surface of small bore piping. In this study, phased array ultrasonic inspection technique is applied to increase inspection speed and reliability. To achieve this object, the 3.5 MHz phased array ultrasonic transducer are designed and fabricated. The manually encoded scanner was also developed to enhance contact conditions and maintain constant signal quality. Additionally inspection system is configured and inspection procedure is developed.

Simulation studies for optimisation of phased array parameters for examination of roll-joints in pressurised heavy water reactor coolant channels

The roll-joint area in the pressure tubes of pressurised heavy water reactors (PHWRs) is prone to delayed hydride cracking (DHC). This region is monitored during in-service inspection to avoid any catastrophic failure. The in-service inspection involves ultrasonic angle beam examination using a single-crystal high-frequency immersion probe. The inspection is limited to a region of 30-40 mm just ahead of the roll-joint where DHC is expected to occur. An ultrasonic phased array technique has been developed to replace the conventional approach. Using phased array, it is possible to examine the roll-joint region for DHC in a single rotation of the inspection head without axial movement. As a result, there is a huge saving in the inspection time. Moreover, the focusing of the sound beam provided by the phased array helps to achieve enhanced sensitivity and resolution. This paper describes the simulation studies carried out for optimisation of the aperture size and focal laws for the phased array examination of the roll-joints of coolant channels of PHWRs. The results of the simulation are validated by carrying out experiments on a sample piece with reference EDM notches 6 mm long, 0.2 mm wide and 0.15 mm deep.

Inspection of anisotropic composites using ultrasonic phased arrays

An approach, referred to as Velocity Variation Compensation (VVC), used to improve the inspection sensitivity of composites utilizing an ultrasonic phased array technique is described. This approach uses an ultrasonic immersion through-transmission technique to measure the velocity variation within an anisotropic composite material as the incident angle varies. Delay laws for phased array inspection were then modified using the measured velocity, and applied to a 5 MHz 32 elements phased array probe. Both methods were performed on the same sample, and the results showed that the detectability of defects was significantly increased.

Evaluation of ultrasonic phased array and laser optical techniques for the intermediate inspection of the root and hot pass in girth welds for clad pipelines

Evaluation of ultrasonic phased array and laser optical techniques for the intermediate inspection of the root and hot pass in girth welds for clad pipelines

횡파 위상배열 초음파 탐촉자 설계 및 성능 평가

일반적으로 위상배열 초음파검사 기법을 이용한 배관 용접부검사에서는 높은 검사 각도를 효과적으로 발생하기 위하여 ��지를 사용하게 된다. 그러나 용접부 또는 접근이 제한된 부위에 대한 검사는 위상 배열 초음파 탐촉자에 ��지를 부착하게 되면 ��지의 전단 길이로 인하여 검사체적을 포함하지 못하는 등의 문제점이 발생하게 된다. 따라서 ��지를 사용하지 않고 높은 검사 각도를 발생할 수 있는 횡파 위상배열 초음파 탐촉자를 적용해야 할 필요성이 있다. 본 연구에서는 굴절각도가 높은 횡파를 발생할 수 있는 위상배열 초음파 탐촉자를 설계하고 제작하여 다양한 깊이의 EDM 노치가 가공된 시험편에서 결함이 정확하게 검출되고 평가될 수 있는 지를 확인하였다. 결과적으로 본 연구에서 설계된 횡파 위상배열 초음파 탐촉자는 다양한 깊이의 결함을 검출하고 신뢰성 있는 정밀도를 나타내었으므로 향후 접근제한이 예상되는 발전설비 구조물의 검사에 적용된다면 효과적인 검사 결과를 보여줄 것으로 기대된다. Typically, a wedge is involved to generate effectively high inspection angle in pipe weld inspection using phased array ultrasonic technique. But the usage of this wedge for weld or access limited area can cause coverage limitation for the examination volume because of the wedge front length. Therefore, the shear wave phased array probe which can generate high inspection angle without wedge is essentially necessary. In this paper, the shear wave phased array ultrasonic probe which can generate high inspection angle designed by modeling and manufactured from the modelling result. And this shear wave probe tested whether it can detect and sizing for EDM test block that contains various depth. As results, the experimental results show that the designed shear wave phased array probe can detect and size with reliable accuracy. Therefore if this phased array probe apply in field inspection, it is expected that it show more reliable inspection result for plant structure having access limitation.

Field Inspection of Phase-Array Ultrasonic for PolyEthylene Electrofusion Joints

Welding and/or fusion in polyethylene(PE) system made on site is focused on the control of the welding or fusion process to follow proper procedure. The process control is important, but it is not sufficient for the long term reliability of a pipe system. To achieve the rate of failure close to zero, Non Destructive Testing(NDT) is necessary in addition to joining process control. For electrofusion joints several non-destructive testing methods are available. The ultrasonic phased array technique is possible to detect various defects including wire deviations and regions with lack of fusion. In this studies, testing was carried to detect the defect after electrofusion joining of polyethylene piping is utilized by the ultrasonic phased array technique. From testing data, ultrasonic phased array technique is recommended as a reliable non-destructive testing method.

Application of Neuro-Wavelet Algorithm in Ultrasonic-Phased Array Nondestructive Testing of Polyethylene Pipelines

Polyethylene (PE) pipelines with electrofusion (EF) joining is an essential method of transportation of gas energy. EF joints are weak points for leakage and therefore, Nondestructive testing (NDT) methods including ultrasonic array technology are necessary. This paper presents a practical NDT method of fusion joints of polyethylene piping using intelligent ultrasonic image processing techniques. In the proposed method, to detect the defects of electrofusion joints, the NDT is applied based on an ANN-Wavelet method as a digital image processing technique. The proposed approach includes four steps. First an ultrasonic-phased array technique is used to provide real time images of high resolution. In the second step, the images are preprocessed by digital image processing techniques for noise reduction and detection of ROI (Region of Interest). Furthermore, to make more improvement on the images, mathematical morphology techniques such as dilation and erosion are applied. In the 3rd step, a wavelet transform is used to develop a feature vector containing 3-dimensional information on various types of defects. In the final step, all the feature vectors are classified through a backpropagation-based ANN algorithm. The obtained results show that the proposed algorithms are highly reliable and also precise for NDT monitoring.

Ultrasonic inspection of AA6013 laser welded joints

Interest in laser beam welding for aerospace applications is continuously growing, mainly for aluminum alloys. The joints quality is usually assessed by non-destructive inspection (NDI). In this work, bead on plate laser welds on 1.6 mm thick AA6013 alloy sheets, using a 2 kW Yb-fiber laser were obtained and inspected by pulse/echo ultrasonic phased-array technique. Good and poor quality welds were inspected in order to verify the limits of inspection, comparing also to X-ray radiography and metallographic inspections. The results showed that ultrasonic phased array technique was able to identify the presence of grouped porosity, through the attenuation of the amplitude of the echo signal. This attenuation is attributed to the scattering of the waves caused by micro pores, with individual size below the resolution limit of the equipment, but when grouped, can cause a perceptive effect on the reflection spectra.

Phased array ultrasonic inspection of low-pressure steam turbine rotors - curved axial entry fir tree roots

The last stage blades of low-pressure steam turbine rotors are among the most highly-stressed components in modern power generating plants. The ongoing drive for increased efficiency has seen a proliferation in the number of designs incorporating larger last stage blades with curved axial entry fir tree roots (CAEFTR); the curvature of the root attachment allows more flexibility in the aerodynamic design of the aerofoil with improved inter-blade spacing. The tendency of CAEFTRs to suffer failure induced by stress corrosion cracking, high-cycle fatigue cracking or low-cycle high-strain fatigue is well documented and can be shown to be most likely to occur in the first two serrations of the blade root. Finite element analysis and actual failures confirm the regions under highest risk and have driven developments in ultrasonic phased array techniques to achieve detection of defects in these regions whilst in situ, in turn avoiding the huge costs associated in decommissioning and dismantling rotors to perform alternative NDE surface inspections. Due to the complexity of the root geometry, there are many difficulties in applying ultrasonic techniques due to limited scanning surfaces, inter-blade spacing and disorientation of the active ultrasound trajectory and the region under test. In this presentation the author will show that the application of novel phased array techniques and unique inspection design has led to increased sensitivity to smaller defects and comprehensive coverage of CAEFTR rotor designs in situ. It will also be shown how the application of these techniques has negated the need to upgrade both equipment and resources to the use of2D arrays, thereby reducing inspection costs significantly whilst achieving higher repeatability and sensitivity. Novel inspection design has led to the ability to reduce the number of scans required, enabled single scan encoded data recording over the whole blade root, increased sensitivity, improved detectability and increased coverage, whilst reducing inspection costs and time.

OS0310 フェイズドアレイ探触子を用いたTOFD法の測定娯差に関する研究(OS3-2 超音波,OS-3 非破壊評価と構造モニタリング1)

Ultrasonic flaw detection and sizing are important issues for ensuring structural reliability of industrial plants. The ultrasonic phased array technique is one of the most effective tools for visualizing the flaws in structural components. However, in the case of flaw size measurement, only an A-scope signal is used for calculation usually. On the other hand, the Time-of-Flight Diffraction method is known as the most accurate flaw sizing method. However, TOFD method is applicable only if the flaw exists on the perpendicular bisector of the ultrasonic probe pair. In this study, new flaw sizing method by using many ultrasonic oscillators was introduced. Through this process, dilution of precision (DOP) was introduced to evaluate measurement error of flaw tip position. By using numerical calculation, the relationship between the DOP and the flaw tip position measurement accuracy was investigated.

Development of Flaw Visualization Technique at Near Field of Phased Array Probe

Ultrasonic flaw detection and sizing is an important issue for ensuring structural reliability of industrial plants. The ultrasonic phased array technique is one of the most effective tools for visualizing the flaws in structural components. It is important to enhance the spatial resolution of phased array images to clearly visualize flaws; however, the spatial resolution of phased array images needs more research. A high spatial resolution phased array probe was designed as the first stage of this study. To investigate the spatial resolution of the phased array probe, acoustic analysis was conducted utilizing the Rayleigh-Sommerfeld Integral. The spatial resolution was investigated by changing the total aperture of the probe. As a result, the large-aperture phased array probe achieved high spatial resolution. Next, ultrasonic testing was simulated by the finite differential method using conventional and specially designed phased array probes. For the conventional probe, the flaw could be visualized but the shape was not clear enough. On the other hand, for the specially designed large-aperture probe, extensive noise appeared in the image and the flaws could not be visualized. Because of mode conversion, Rayleigh waves are generated at the contact surface between the transducer and testing material. The amplitude of Rayleigh waves are much higher than the diffraction echoes, hence the Rayleigh waves disturb the visualized image at the near field of the probe. Consequently a new technique for flaw visualization at the near field of the phased array probe was developed by eliminating detrimental waves. As a result the flaws could be clearly visualized using this technique.

Improved Imaging of Fatigue Crack Profile in Thick Cruciform Samples Using Ultrasonic Phased Array Models

The determination of depth profile of vertical fatigue cracks generated in thick cruciform samples using an ultrasonic phased array is investigated in this paper. The cracks were formed by conducting fatigue fracture test on two mild steel cruciform specimens of 135 mm thickness: one under room temperature and the other under subzero temperature (−70°C). A semi-elliptical surface starter notch of 2 mm width and more than 400 mm length was initially created in the specimens. Alternating current potential drop technique and phased array ultrasonic technique were attempted in order to determine the depth profiles of the starter notch as well as that of the crack. Virtual experiments carried out with a finite-difference time domain based numerical model were found to be advantageous in reducing actual experimental trials, facilitate an understanding of the echo signatures, and help assess the crack depth. The profiles of the crack and the notch were verified through destructive assay of the samples and subsequent dye penetrant assisted physical measurements.

Using phased array ultrasonic technique for the inspection of straddle mount-type low-pressure turbine disc

Discovery of stress corrosion cracking (SCC) in the blade attachment region of nuclear power plant low-pressure steam turbine discs leads to industry concern about this problem. Reliable inspection methods for the detection of SCC in steam turbine blade attachment area are essential to the rotor run/repair/retire decision making process. The conventional broad beam ultrasonic inspection technique usually has inadequate resolution for flaw sizing and tendency for false calls. But the phased array technique by improved detection capability and resolution could increase coverage of the examination areas with less scanning required. Using phased array ultrasonic technique to straddle mount-type low-pressure turbine disc in nuclear power plant located in Korea was studied in this paper.

Ultrasonic detection of surface-breaking railhead defects

On the UK rail network, changing usage patterns have led to rolling contact fatigue (RCF) on the railhead being an increasing problem and frequent testing for such defects is essential. Existing systems for detecting defects are limited in speed ( 5 mm). We are currently working on novel ultrasonic methods of detecting RCF, designed to lift many of the speed limitations and/ or significantly improve accuracy and resolution. A noncontact pitch-catch pulsed ultrasonic system comprising two electromagnetic acoustic transducers (EMATs) generating and detecting Rayleigh-like waves has the potential to operate at high speed, thus improving network inspection coverage. Phased array ultrasonic techniques are being designed to improve imaging and characterisation of the defects. A set of simulated defects on sections of rail have been machined, including half-face slots machined normal to the railhead surface, clusters of angled slots, and pocket defects more typical of real defects. The techniques have been tested on these rails and their potential for use on the rail network is discussed.

Inverse method for detection and sizing of cracks in thin sections using a hybrid genetic algorithm based signal parametrisation

A hybrid-GA method, based on signal parameterization, has been reported here for the improved detection and sizing of surface cracks of small sizes/depths in thin sections. The method relies on parameterizing the composite reference from the defect into its individual components i.e., the crack tip diffracted echo and the corner trap echo and subsequently use the relative arrival time technique (RATT). The phased array ultrasonic technique was employed in the investigation. Both experimental and simulated signals were used in the study. It is shown through both simulations and experiments that the hybrid-GA is successful in parameterizing both non-overlapping and overlapping echoes encountered in thin sections. It is additionally shown that the hybrid-GA improves the signal to noise ratio and correct for under-sampling of data.

Simulation of ultrasonic phased array technique for imaging and sizing of defects using longitudinal waves

Phased array ultrasonics can be used as a rapid tool for imaging and sizing crack-like defects. This paper reports the simulation of phased array ultrasonic wave interaction with the defects using the finite-difference time domain (FDTD) method. Experiments were conducted to validate modeling results for pulse–echo simulations of the phased array transducer on a mild-steel (MS) pipe sample with circumferential internal surface notches of three different sizes. Experiments were carried out on the MS pipe specimen using a conventional ultrasonic technique with a 5 MHz transducer at 45° refracted angle within the specimen and the defects were imaged and sized using the relative arrival time technique (RATT). The experimental B-scans obtained using the conventional ultrasonic techniques were compared with the experimental B-scans obtained using the phased array instrument. Simulation studies were also carried out by steering the beam to the requisite angles by the phased array transducer to study the effect of various angles of incidence on the defect definition, i.e., with respect to imaging and sizing, using the RATT.