Showing papers on "Time-of-flight diffraction ultrasonics published in 2003"

Time of flight diffraction (tofd) technique for accurate sizing of surface breaking cracks

Abstract: This paper deals with an experimental study for evaluation of TOFD technique for determination of size of the surface breaking cracks. The study was confined to simulated cracks. The steel test blocks used for the study contained 0.5mm wide vertical slits of various heights ranging from 0.91mm to 30mm. Another set of blocks contained inclined slits (10°, 15°) inclination of various heights ranging from 2.56mm to 19.82mm. Both the vertical and inclined slits were opened to the top surface. TOFD equipment Model MICROPLUS of M/S AEA Technology, UK with manual scanner along with longitudinal angle beam probes of 45° - 4MHz were used for the study. The blocks were scanned along the slits / defects and across the slits. The scanned images were analysed for the sizing. The results of the study indicated an average error of ±0.13 for depth in vertical slits and ±0.05 for inclined slits whereas the average error in length measured was ±0.36mm for vertical slits and ±0.29mm for inclined slits. However difficulty was experienced using TOFD to size defects extending less than about 2mm depth. This is due to the presence of the lateral wave, which obscures the tip-diffracted signals from the defects close to the surface and also due to the inherent lack of time resolution near the surface.

Method for ultrasonic control of weld joints

Abstract: The invention concerns a method for non-destructive ultrasonic control, combining time-of-flight diffraction (TOFD) and inclined longitudinal wave techniques, of weld joints assembling two abutted parts. The method consists of using the time-of-flight diffraction technique, displacing in the longitudinal or circumferential direction, along the weld joint to be controlled, at least one pair consisting of a first transducer and of a second transducer, one transmitting and the other receiving ultrasonic waves, these transducers being laterally positioned on either side of the joint to be controlled, these transducers comprising piezoelectric ceramics or crystals. Furthermore, it consists of displacing along the welded joint to be controlled, using the inclined longitudinal wave technique, at least a third transducer, so as to detect any defect of the joint located at a thickness ranging between 0.5 mm and 15 mm.

Configurations and methods for ultrasonic time of flight diffraction analysis

Abstract: An ultrasound test apparatus for polymeric materials (e.g., plastic pipes) includes a low-absorption housing that at least partially encloses an ultrasound transducer, wherein the transducer emits a low frequency wide angle ultrasound beam with a narrow bandwidth. In especially preferred configurations and methods, the apparatus will detect flaws in polymeric pipes, and especially in welds or stressed zones of such pipes, wherein defects of less than 4% of the wall thickness (up to 4 inches) are detected. Further disclosed are configurations and methods for non-destructive detection of lack-of-fusion defects in polymeric pipes.

Time-of-flight diffraction (TOFD) technique for accurate sizing of cracks embedded in sub-cladding

Abstract: This paper deals with an experimental study for evaluation of the TOFD technique for determination of size of cracks embedded in sub-cladding. It extends the results presented in the previous papers ( 1 , 2 ) . The studywas confined to simulated cracks (machined slits) underneath the cladding. It was found that crack heights ranging from 1.68 mm to 19.04 mm underneath stainless steel, Inconel and ferritic cladding could be sized with an accuracy of ′0.2 mm. Difficulty was experienced using TOFD to size cracks starting from the interface between Inconel/stainless steel cladding and the ferritic base ie (5 mm/6 mm below the scanning surface). However, these cracks could be detected and sized by scanning through the cladding from the opposite surface of the blocks. Even the small cracks of the order of 1.9 mm could be detected as long as they are not influenced by the lateral wave. Experimental errors are presented.

Ultrasonic flaw detecting method and device

Abstract: PROBLEM TO BE SOLVED: To solve the problem that there is no ultrasonic flaw detecting device which can easily determine a defect, in the case where the inspection result, in ultrasonic flaw detection by TOFD method, is evaluated. SOLUTION: The device comprises a measuring instrument comprising a bottom surface reflected wave removing device 13 which removes a bottom surface reflected wave to accentuate a defective signal; an ultrasonic signal correcting device 14 which amplifies an ultrasonic echo to amplify the defective signal; a synthetic aperture device 15 which amplifies the defective signal by synthetic aperture processing; a lateral wave removing device 16 which removes a lateral wave to accentuate the defective signal; and a wavelet processor 17 which reconstructs the ultrasonic echo using a wavelet analysis order to accentuate the defective signal, the measuring instrument having the function of accentuating the defective signal using any one of, or a combination of two or more of, the bottom surface reflected wave removing device 13, ultrasonic signal correcting device 14, synthetic aperture device 15 and lateral wave removing device 16, and accentuating this accentuated defective signal with the wavelet processor 17. COPYRIGHT: (C)2005,JPO&NCIPI

Automatic ultrasonic flaw detection method and apparatus of welded section

Abstract: PROBLEM TO BE SOLVED: To obtain an automatic ultrasonic flaw detection method and an automatic ultrasonic flaw detection apparatus of welded sections for surely detecting flaws and reducing the flaw detection time by combining a pulse reflection method and a TOFD method. SOLUTION: In the automatic ultrasonic flaw detection method of a welded section, the pulse reflection method for performing the vertical square scanning of a probe, in a direction along a welded line and a direction at right angles to the welded line, and the TOFD system for scanning the probe in a direction along the welded line are combined so as to be compound flaw detection. In the automatic ultrasonic flaw detection apparatus of the welded section, a rail is installed in parallel with the welded line, a body that can drive while being guided by the rail is installed, a movable shaft that can slide at right angles to the driving direction of the body, a fixed shaft that is extended in the same direction are provided, a probe for pulse reflection is fitted to the movable shaft, and the probe for TOFD is fitted to the fixed shaft.

'Time-Frequency Techniques applied To TOFD for the automation of Rail-track Inspection'

Abstract: Time-Of-Flight Diffraction (TOFD) is a recent innovation in the non-destructive testing field and has proved a highly versatile and valuable technique for the automatic inspection of welds. TOFD can be used for automatic inspection of rail-track particularly the fishplate and welds areas of the track, which are considered high failure-rate places. Novel Time-Frequency analysis is applied to characterise the TOFD signals and classify defect type. Combining these features with an artificial neural network classifier can provide full automation of the defect detection process. The results of a preliminary study are presented and discussed. For the covering abstract see ITRD E123761.

Quality control enhancement via nondestructive testing for green ceramic tiles

Abstract: Quality control in ceramic tile manufacturing is hard, labor intensive and it is performed in a harsh industrial environment with noise, extreme temperature and humidity It can be divided into color analysis, dimension verification, and surface defect detection which is the main purpose of our research Defects detection is still based on the judgment of human operators while most of the other manufacturing activities are automated so, our work is a quality control enhancement by implementing a nondestructive testing for the green ceramic tiles using noncontact ultrasonic sensors enables on-line process control, which is a test configuration for the green ceramic tiles Ultrasonic testing is extensively utilized for integrity verification of composite materials The design presented here in the research is a low cost on-line measurement system using noncontact ultrasonic transducer based on the time of flight diffraction (TOFD) technique, which is one of the nondestructive testing techniques TOFD is rapidly gaining importance as a powerful stand alone inspection technique that can simultaneously detect and size defect This paper, presents the results of an experimental investigation for a nondestructive test on real green ceramic tiles including manufacturing defects which will be reported in the research

Laser Ultrasonic Study of Crack Tip Diffraction

Abstract: Ultrasonic diffraction pattern at a crack tip and crack depth sizing based on the diffraction are studied by using laser‐generated bulk waves Directivity patterns oriented essentially along the normal for the diffracted longitudinal wave and essentially at 45 (deg) for the diffracted shear wave for any incident angles is obtained A laser‐ultrasonic system combined with time‐of‐flight (TOFD) analysis is produced and demonstrates accurate crack sizing on an artificial slot having a variable depth from 0 mm to 10 mm An improvement of signal‐to‐noise ratio by split spectrum processing (SSP) is also suggested

Reducing pipeline construction costs: New technologies

Abstract: The Oil and Gas industry is constantly looking for ways to reduce capital investment for new projects while maintaining performance and quality standards. As the demand for oil and natural gas increases, so does the need for an expanded network of onshore and offshore transmission pipelines. However, the capital investment associated with new pipelines is enormous. There are a number of materials joining technologies that are being investigated to reduce pipeline construction costs. This document presents three technologies showing particular promise: laser pipeline welding, the use of high strength pipeline materials, and advanced automatic inspection. Test have shown that the HLAW process, which combines the LBW and GMAW processes, is felt to offer a number of benefits in terms of higher potential productivity, ability to produce welds with excellent material properties and a reasonable tolerance for fit-up variations. For existing laser power levels, a viable scenario for implementation of lasers for pipeline welding applications is the use of HLAW for root bead welding, followed by joint filling with conventional mechanised GMAW-P. Concerning the use of high strength pipeline materials, results of a project are presented. The primary objective of this study was to evaluate the mechanical properties of weld metals deposited using a number of commercially available welding consumables and welding processes. This work included characterization of weld metal microstructure, HAC susceptibility of the GMA weld metal and X100 base metal, and solidification cracking of selected welding consumables. The project evaluated commercially available consumables using several welding processes and shielding gases. The third part of the document covers results of a project aiming to collect third-party independent data and statistically characterise the systematic and random errors in girth weld defect sizing, as measured by mechanised ultrasonic testing P/E, TOFD methods and PA ultrasonic technology, in support of pipeline reliability assessments. The defect sizing accuracy of the automated ultrasonic testing (AUT) of girth welds was evaluated using zonal discrimination with focused and non-focused search units arranged for P/E and TOFD methods and PA technology. The objectives were achieved by conducting “open” and “blind” UT trials. NDE flaw verification and destructive testing for flaw size validation were performed. AUT data were collected and statistically analysed.

Ultrasonic signal processing system, method, program, and storage medium and ultrasonic flaw detection apparatus

Abstract: PROBLEM TO BE SOLVED: To provide an ultrasonic signal processing system capable of easily and accurately detecting a flaw by using a TOFD(time of flight diffraction) method. SOLUTION: In a system for processing an ultrasonic signal due to a defect 4 existing in a specimen 1 based on the TOFD method by receiving an ultrasonic wave transmitted from a transmission oblique probe 2 disposed in the specimen 1 by using a reception oblique probe 3, a signal processing program 7 is carried out, a circular pattern indicated on a B scope is automatically detected based on the ultrasonic signal, and the existence of the defect 4 is indicated and displayed based on the detected circular pattern. COPYRIGHT: (C)2004,JPO&NCIPI

An automated ultrasonic inspection method for thickness checking of dryer cylinders for paper making machines

Abstract: Paper machine dryer cylinders are steam heated cast iron cylinders typically 7.2 m long by 1.5 m diameter with a wall thickness of between 25 and 35 mm. In-service inspection requirements specify that dryer non-destructive testing is performed to the standard document TIS-0402-16: 'Guidelines for the Inspection and Not Destructive Examination of Paper Machine Dryers'. This Standard requires periodic thickness surveys to be conducted to assure that the shell thickness is consistent with the maximum allowable working pressure. Ultrasonic thickness readings can determine the worn or thin spots that threaten the integrity of the dryer, but a problem exists in using conventional pulse echo techniques. Accurate ultrasonic thickness measurement depends on consistency in the material properties between the calibration test-piece and the work-piece. On any given dryer cylinder the material properties of the cast iron and therefore the velocity of sound varies over the length and around the circumference. Therefore, reliable and accurate thickness measurements cannot he made from a single point calibration and it is physically impossible to obtain multi-calibration points on a dryer cylinder using a conventional pulse echo technique. This paper describes the development and application of a self-calibrating ultrasonic imaging system using aspects of the time-of-flight diffraction (TOFD) method to provide a cross section image and accurate point readings along the whole length of a dryer cylinder. This enables accurate, rapid monitoring of the vessel thickness and a reliable ongoing hard-copy record of the test.

Development of an Inspection Robot for Spherical Storage Tanks

Abstract: Recently new ultrasonic flaw detection system called TOFD method is utilized to externally inspect the inner and outer surfaces of weld seams on spherical storage tanks while tanks are in use. In this system, the robot mounted the sensors is not only permitted to travel along the weld seam rapidly but also required to follow the weld seam precisely. In this paper, the development of a magnetic-wheeled robot that can follow the weld seam within 5 mm based on feedback control is described. Since October 1999, this robot has been in experimental operation on an actual spherical tank. Practical introduction of this robot will shorten inspection time by about one week from the conventional 23 days, and will reduce the conventional number of inspectors required from 4 to 2-3.

Acquisition of Time of Flight Diffraction Data by Mobile Robots

Abstract: It is shown that Time of Flight Diffraction (TOFD) data acquired with 6 and 7 axes robot scanning arms (that are carried by mobile wall climbing vehicles which can travel on curved surface) is of a much better quality than that acquired by manual deployment. The robotic devices are able to operate in remote and hazardous locations while maintaining more constant contact forces and obtaining repeatable data unaffected by fatigue which manual operators find very difficult to match.

Linear Scanning Ultrasonic Inspection Developments with TOFD in Brazil, for the Replacement of Radiography and Manual Ultrasonic Inspection.

Abstract: A rapid detection technique has been developed using a computerized ultrasonic system with a multi-probe array. The technique allows rapid detection of flaws, precise sizing capabilities and a safe and economical replacement for radiography and manual ultrasonic. This combination of TOFD and Pulse-Echo techniques allow conformance to AMSE Code Case 2235. Examples of 4 significantly different projects carried out in Brazil will be provided.

High resolution defect detection for thermoplastic butt-welds in operating pipelines by ultrasonic tofd

Abstract: The paper discusses high resolution ultrasonic time of flight diffraction method that provides an unprecedented, fast inspection and assessment method for both shop and field. It also provides pipeline operators with immediate results for risk assessments of weld integrity. The UT-TOFD method allows 2-person crews to set up, inspect, analyze, and categorize weld defects quickly - for example, 15 minutes per weld for a 32 inch diameter pipe. The method has been tested and proven effective in large scale field pipeline applications.

Ultrasonic Imaging of Material Condition Using Advanced Simplified Ultrasonic CT

Abstract: In this research, as a new measurement method to estimate the infinitesimal change of material condition, the simplified ultrasonic CT system, which uses the information of three directions, that is, 90°, +45° and −45° direction about inspection plane is proposed. Use of simplified ultrasonic CT system has two merits: Firstly, the measurement time is very short comparing with general CT. Secondly, it can detect sensitively very infinitesimal defect in vertical or slant direction about inspection plane because the obtained image is not C scan image but CT image calculated from three directions. From these merits, this method can be considered as a very effective method for the evaluation of material condition. In order to know the applicability of actual NDT, several kinds of welded specimens are investigated. The result showed that the CT images obtained were very similar to actual defect of specimens. Also, in order to confirm the performance of simplified ultrasonic CT, the D scan image by TOFD method was obtained for the same specimen. The C scan or CT image gave better information than the D scan image obtained from TOFD method.

Pressure Vessels Inspections Using Ultrasonic Phased Arrays

Abstract: Phased arrays offer significant technical advantages for weld inspections over conventional ultrasonics The phased array beams can be steered, scanned, swept and focused electronically Beam steering permits the selected beam angles to be optimized ultrasonically by orienting them perpendicular to the predicted defects, especially Lack of Fusion Electronic (linear) scanning permits very rapid coverage of the welds Beam steering (usually called sectorial or azimuthal scanning) can be used for mapping welds at appropriate angles to optimize Probability of Detection of defects Electronic focusing permits optimizing the beam shape and size at the expected defect location, also to optimize Probability of Detection Overall, the use of phased arrays permits optimizing defect detection while minimizing inspection time The paper describes the application of phased arrays for inspecting pressure vessel welds Phased arrays offer significant practical advantages over conventional automated inspections Thick section weld inspections typically use the established “top, side, end” or “top, side, TOFD” views of the weld Other displays can be used, eg strip charts for zone discrimination scanning of narrow gap welds Special inspections can be easily performed with phased arrays, eg additional beams for extra coverage, multiple angles or inspection set-ups simultaneously, or special scans such as tandem probes Different delivery systems and instrumentation can be assembled for any required scan Fitness-For-Service inspections requiring high PoD and accurate sizing can be performed using upscale systems These phased array inspections can be tailored to any known code requirementsCopyright © 2003 by ASME