Phased Array Inspection Research Articles

Ultrasonic phased array inspection using full matrix capture

Ultrasonic phased array inspection using full matrix capture

Post Signal Processing of Ultrasonic Phased Array Inspection Data for Non-destructive Testing

Abstract In ultrasonic phased array non-destructive testing, the amplitude of the grain noise can be smaller than that of the echoes, and the grain noise can totally mask echoes characterizing faults. Several algorithms such as band pass filter, low pass filter, wiener deconvolution and wavelet have been employed to reduce the grain noise. In this paper, an actual S-scan detection image was obtained from a real time UT acquisition system, and a comparison of the suppressing grain noise performances of low pass filter and wavelet de-noising algorithm was displayed. The results show that the wavelet de-noising algorithm is better than other algorithms listed in this paper, and it can suppress the amplitude of grain noise from 100% to 20%. This approach is shown to offer significant performance advantages for NDE.

Model Based Reliability Analysis of PA Ultrasonic Testing for Weld of Hydro Turbine Runner

Defects in the weld of hydro turbine runner are difficult to be detected by conventional ultrasonic testing because of the distorted surface and variational cross-section of blade. Ultrasonic phased array inspection technology was used to inspect the weld for its dynamic focusing. The testing procedure was created based on the ultrasonic testing numerical model and quantitative evaluated based on probability of detection model. The result shows that the testing procedure is feasible and effective.

The study on defects in aluminum 2219-T6 thick butt friction stir welds with the application of multiple non-destructive testing methods

The present study focused on the relationship between primary friction stir welding process parameters and varied types of weld-defect discovered in aluminum 2219-T6 friction stir butt-welds of thick plates, meanwhile, the weld-defect forming mechanisms were investigated. Besides a series of optical metallographic examinations for friction stir butt welds, multiple non-destructive testing methods including X-ray detection, ultrasonic C-scan testing, ultrasonic phased array inspection and fluorescent penetrating fluid inspection were successfully used aiming to examine the shapes and existence locations of different weld-defects. In addition, precipitated Al2Cu phase coarsening particles were found around a ‘kissing-bond’ defect within the weld stirred nugget zone by means of scanning electron microscope and energy dispersive X-ray analysis. On the basis of volume conservation law in material plastic deformation, a simple empirical criterion for estimating the existence of inner material-loss defects was proposed. Defect-free butt joints were obtained after process optimization of friction stir welding for aluminum 2219-T6 plates in 17–20mm thickness. Process experiments proved that besides of tool rotation speed and travel speed, more other appropriate process parameter variables played important roles at the formation of high-quality friction stir welds, such as tool-shoulder target depth, spindle tilt angle, and fixture clamping conditions on the work-pieces. Furthermore, the nonlinear correlation between weld tensile strengths and weld crack-like root-flaws of different lengths was briefly investigated.

Testing of welds, new international standards for innovative non-destructive examination

New non-destructive examination methods have been available for many years. These include time of flight diffraction and phased array methods. These are routinely used for inspection of welds. Work is ongoing at ISO and CEN for standardization of these methods. First the time of flight diffraction was drafted and now ISO and CEN are working on a standard for phased arrays. These drafts are used for welding inspections. The acceptance criteria is in draft form for time of flight diffraction which will be followed by that for phased array. Standards are already available for base material phased array inspection such as the ASTM document “Standard Guide for Evaluating Performance Characteristics of Phased Array Ultrasonic Examination Instruments and Systems”. Several ASME code-cases have been issued in recent years on weld inspection. Qualification for the ASME code is also planned for this novel technique.

Testing of welds, new international standards for innovative non-destructive examination

New non-destructive examination methods have been available for many years. These include time of flight diffraction and phased array methods. These are routinely used for inspection of welds. Work is ongoing at ISO and CEN for standardization of these methods. First the time of flight diffraction was drafted and now ISO and CEN are working on a standard for phased arrays. These drafts are used for welding inspections. The acceptance criteria is in draft form for time of flight diffraction which will be followed by that for phased array. Standards are already available for base material phased array inspection such as the ASTM document “Standard Guide for Evaluating Performance Characteristics of Phased Array Ultrasonic Examination Instruments and Systems”. Several ASME code-cases have been issued in recent years on weld inspection. Qualification for the ASME code is also planned for this novel technique.

NEWSDESK: Phased array inspection system facilitates successful installation of bar finishing facility; Sustainable engineering – ECUKguides the profession; Online condition monitoring system helps manage remote pumping station; Development of an underwater radiography inspection system for inspection of flexible risers

NEWSDESK: Phased array inspection system facilitates successful installation of bar finishing facility; Sustainable engineering – EC^UKguides the profession; Online condition monitoring system helps manage remote pumping station; Development of an underwater radiography inspection system for inspection of flexible risers

Code inspection of welds using phased arrays

AbstractCritical welds need inspecting, because of either code requirements or structural integrity. Automated ultrasonics has proven more reliable than other techniques, such as radiography or manual techniques. Recently, portable phased arrays have become a dominant method of inspecting as they offer high speed, repeatable inspections. Techniques are available for a wide variety of vessels and pipes using commercial equipment. In addition, ASME section V now has five code cases available for phased array inspections of welds. One aspect of phased array inspections is that the coverage must be demonstrated using a scan plan, which can be a ray tracing programme showing the beam coverage, inspection angles, etc. This approach has big advantages for a flexible technology such as phased arrays; specifically, unusual weld profiles can be inspected using tailored scan plans. Unlike conventional ultrasonics or radiography, angles can be selected to optimise defect detection. Also, phased arrays can be adapted ...

Characterization of the system functions of ultrasonic linear phased array inspection systems

This work characterizes the electrical and electromechanical aspects of an ultrasonic linear phased array inspection system, using a matrix of system functions that are obtained from the measured response of individual array elements in a simple reference experiment. It is shown that for the arrays tested all these system functions are essentially identical, allowing one to use a single system function to characterize the entire array, as done for an ordinary single element transducer. The variation of this single system function with the number of elements firing in the array or with changes of the delay law used is examined. It is also demonstrated that once such a single system function is obtained for an array, it can be used in a complete ultrasonic measurement model to accurately predict the array response measured from a reference reflector in an immersion setup.

Ultrasonic phased array inspection of electrofusion joints in polyethylene pipes

The electrofusion technique for joining polyethylene pipe is one of the common joining methods used in the water and gas industries for distribution pipes. Common problems in manufacture of these joints are contamination, lack of fusion, lack of penetration and insufficient heat applied to the weld resulting in a sticking or weak bond. The latter flaws can result in a joint that, although apparently fused, does not have the same mechanical properties as a properly prepared joint. The phased array technique has been specifically designed to provide a rapid inspection method for field application and this paper presents an ultrasonic technique for detecting and monitoring flaws in the weld. The results of the extensive laboratory experiments and the field application of the prototype system are presented.

Enhancement of Flaw Detectability Using Time Reversal Techniques

Ultrasonic phased array inspection has been paid a great attention in ultrasonic nondestructive evaluation since it can provide a benefit of focusing and/or steering ultrasonic beams. A time reversal technique is claimed to be very robust to focus beams through inhomogeneous media, using the phased array transducers. In this paper, the performance and limitations of a D.O.R.T. method, which is one of the time reversal techniques, is considered based on the experimental studies. In addition, a variation of the D.O.R.T, namely a pre-focused D.O.R.T., is proposed in order to overcome the limitations of the current D.O.R.T. method. The results of the newly proposed method are compared to those obtained by conventional focusing methods.

Study on Scanner for Large-Diameter Tubular Joint Welds Based on Ultrasonic Phased Array

For the complexity of weld, the automatic inspecting for the tubular joints which are in working is difficult. Therefore the scanner which has three degrees of freedom for inspecting of large-diameter tubular joints was studied and manufactured based on the scanning principle of ultrasonic phased array. The following of probe to weld is realized by the simultaneous motion of two degrees of freedom and the pose between probe and weld is adjusted by the other degree of freedom. The control strategy of the scanner was provided. Experiments were made with scanner on reference blocks, the results indicate that the automatic ultrasonic phased array inspection is more excellent than the conventional ultrasonic inspection in reliability and repetition.

Development of Phased Array and Tofd Simultaneous Inspection System for Coke Drum

Development of Phased Array and Tofd Simultaneous Inspection System for Coke Drum

Ultrasonic phased array inspection technology for the evaluation of friction stir welds

This paper is based upon a project 'Qualistir' for the on-line quality control of friction stir welds (FSW) in aluminium ( 1 ) . Qualistir is a collaborative project lead by R/D-Tech with co-industrial partners Vermont, Isotest, Neos Robotics and Gatwick Fusion, and research partners TWI, GKSS and TUS. The objective of the project is to develop an on-line method for determining the quality of FSW in a butt-welded configuration. The inspection technique described in this paper detects conventional defects and supplies a method for determining whether the weld has been correctly forged which, in turn, safeguards against joint line remnant defects.

Independent qualification of phased array inspection of fillet welds

Magnox Generation has investigated whether it is feasible to carry out ultrasonic inspection of welds associated with boiler beam support brackets at various Magnox power stations. The welds are small, with a leg length typically of 6 to 15 mm, and they could not be properly inspected using conventional ultrasonic probes. A technique was therefore developed using a phased array system. This allowed the ultrasonic beam to be focussed electronically, thereby obtaining the required spatial resolution, and also allowed the beam angle to be varied in order to direct the beam into the weld volume between the cap and root. Following the development work, it was decided to apply the technique to some boiler beam support bracket welds at Sizewell A power station. This paper addresses the qualification of the inspection procedure, which TWI managed on behalf of Magnox Generation following the ENIQ methodology. The comprehensive technical justification document was supported by practical trials of the procedure, equipment and individual data analysts. The qualification was completed successfully and confirmed that the procedure was capable of reliably detecting crack-like defects in the weld or heat affected zone greater than 1.5 mm wide by 10 mm long. It also confirmed that, subject to certain provisos, the defect width would not be underestimated by more than 1.5 mm. This qualification involved a novel technique with particular challenges and this paper describes the way in which these were overcome.

Development of phased array techniques to improve characterization of defect located in a component of complex geometry

Ultrasonic inspection of complex geometry components has to cope with different problems: limited access of the area assumed to be insonified, beam misorientation and distortions, loss of sensitivity. Those harmful effects can lead to inspection performance degradations, especially in terms of defect detection and characterization. Phased array techniques may be used to overcome such difficulties, as they can provide an optimal mastering of the ultrasonic beam radiated through the inspected component. This paper presents some applications of phased array inspections carried out by the French Atomic Energy Commission (CEA) and the French Company of Electricity (EDF) in the framework of R&D studies. Inspections of components with varying profile (of planar and cylindrical parts, misalignment and local depression), and containing artificial reflectors have been carried out with pulse echo immersion techniques, using standard and phased arrays transducers. Optimal delay laws have been applied to preserve the beam characteristics in spite of the varying profile geometry encountered as the phased array transducer was moved over the component. Those delay laws allow to efficiently compensate the beam distortions generated by the profile geometry. They were computed using a specific model and compared to experimental delays obtained using through transmission tests. Experimental and simulation results showed that the defect detection and characterization performances were greatly enhanced using phased array techniques. In the presented examples, with standard transducers, defects located below the irregular parts of the specimen were partially detected, inaccurately located or even missed, whereas phased array inspections enabled to detect and locate all of these defects.

Crack detection and sizing technique by ultrasonic and electromagnetic methods

Improvements in defect detection and sizing capabilities for non-destructive inspection techniques have been required in order to ensure the reliable operation and life extension of nuclear power plants. For the volumetric inspection, the phased array UT technique has superior capabilities for beam steering and focusing to objective regions, and real-time B-scan imaging without mechanical scanning. In contrast to the conventional UT method, high-speed inspection is realized by the unique feature of the phased array technique. A 256-channel array system has developed for the inspection of weldment of BWR internal components such as core shrouds. The TOFD crack sizing technique also can be applied using this system. For the surface inspection, potential drop techniques and eddy current techniques have been improved, which combined the theoretical analysis. These techniques have the crack sizing capability for surface breaking cracks to which UT method is difficult to apply. This paper provides the recent progress of these phased array and electromagnetic inspection techniques.

New applications using phased array techniques

In general, the application of phased array techniques used to be limited to heavy components with large wall thicknesses, such as those in the nuclear power industry. With the improvement of the phased array equipment, including phased array search units, other application areas are now accessible for the phased array inspection technique, e.g. the inspection of turbine blade roots, weld inspection with a wall thickness ranging from 12 to 40 mm, inspection of aircraft components, inspection of spot welds and the inspection of concrete building components. The objective for the use of phased array techniques has not significantly changed since their first application, e.g. instant adjustment of the sound beam to the geometry of the test object by steering incidence angle, skew angle and/or sound field focusing. Because some new phased array technique applications are still in the experimental (laboratory) stage, this article will focus on some examples for practical, real-weld applications.

Improvement of SH-wave EMAT phased array inspection by new eight segment probes

This paper presents a newly developed electromagnetic acoustic transducers (EMAT) probe with eight transmitter and eight receiver segments aiming to improve performance of a phased array EMAT probe with four transmitter and four receiver segments. Results of tests on artificial flaws in HAZ in a 6 inch diameter austenitic mock-up pipe were shown for characterizing its performance. The UT result with a conventional Piezo transducer was also referred for comparison.

Apparative developments for inservice inspections of reactor pressure vessels

Inservice inspections of primary circuit components are important preventive measures to guarantee nuclear power plant integrity, satisfying simultaneously reactor safety and economy in plant operation. Emphasizing pressurized water reactor pressure vessel (RPV) inspections, recent developments of new generations of automated and mechanized ultrasonic inspection equipment are presented. Starting from general equipment design and inservice implementation criteria, specific examples are given. Main attention is directed to equipment realization of phased array and ALOK inspection techniques, especially in their combination. Refined aspects of subsequent computer processing and evaluation of defect detection data are described. Analytical features and potential for further developments become evident. Remote controlled RPV inspections are stressed by describing a new generation of central mast manipulators, forming an integral part of total inservice inspection system.