Showing papers on "Time-of-flight diffraction ultrasonics published in 2009"

Preliminary Assessment of NDE Methods on Inspection of HDPE Butt Fusion Piping Joints for Lack of Fusion

Abstract: Studies at the Pacific Northwest National Laboratory in Richland, Washington, are being conducted to evaluate nondestructive examination approaches for inspecting butt fusion joints in high density polyethylene (HDPE) pipe for lack of fusion (LOF). The work provides information to the United States Nuclear Regulatory Commission on the effectiveness and need for volumetric inspection techniques of HDPE butt fusion joints in Section III, Division 1, Class 3, buried piping systems in nuclear power plants. This paper describes results from preliminary assessments using ultrasonic nondestructive techniques and high-speed tensile impact testing for determining joint integrity. A series of butt joints were fabricated in 3408, 12-inch IPS DR-11 material by varying the fusion parameters in attempts to provide good joints and joints containing LOF. These butt joints were visually examined and volumetrically examined with time-of-flight diffraction (TOFD) and phased-array (PA) ultrasound. A limited subset of pipe joint material was destructively analyzed by either slicing through the joint and visually examining the surface or by employing a standard high-speed tensile impact test. Initial correlation of the fusion parameters, nondestructive, and destructive evaluations have shown that areas with gross LOF were detected with both TOFD and PA ultrasound and that the tensile impact test showed a brittle failure at the joint. There is still some ambiguity in results from the less obvious LOF conditions. Current work is targeted on assessing the sensitivity of the ultrasonic volumetric examinations and validating the results with a destructive analysis. It is expected that on-going and future work will lead to quantifying the ultrasonic responses in terms of joint integrity.Copyright © 2009 by ASME

An Ultrasonic Time of Flight Diffraction Technique for Characterization of Surface-Breaking Inclined Cracks

Abstract: This paper presents the development of a testing technique for measuring the angle of inclination and depth of surface-breaking inclined cracks in simple geometry components using a manual ultrasonic time of flight diffraction system. The testing technique in this work can be useful in risk based test planning for simple geometry components such as pipelines and boiler headers.

Detection and Sizing of Defects in Complex Geometry Weld by Manual Ultrasonic Time of Flight Diffraction Inspection

Abstract: The basic aim of this current research is to reliably detect and size defects in complex geometry welds using the well-known ultrasonic time of flight diffraction (TOFD) technique. A complex geometry weld specimen with various artificial defects was designed and fabricated. Different combinations of probe angles and probe center spacings were used in experiments for determining the optimum one. TOFD models were also developed for sizing the defects and experimentally verified.

Devices And Methods Of Ultrasound Time Of Flight Diffraction Sensitivity Demonstration

Abstract: An ultrasound time-of-flight diffraction reference block has a plurality of notches that extend into the block to simulate cracks, wherein the notches have a normal and transverse orientation with respect to a test path formed on the block.

Wideband ultrasonic time of flight diffraction combining b-scans and cross-sectional imaging

Abstract: Time of Flight Diffraction and Imaging (ToFDI) is a new technique utilizing a sparse array of transducers and signal processing to improve B‐Scan output and create a cross‐sectional image of a sample. This paper describes preliminary work demonstrating the concept, including; Finite Element Modelling (FEM), basic processing, likely applications. The eventual aim is for fast and automated detection, identification, positioning and sizing for all defects in a sample with known basic characteristics, such as bulk and shear elastic moduli.

Towards automatic analysis of ultrasonic time-of-flight diffraction data using genetic-based Inverse Hough Transform

Abstract: Ultrasonic Time-of-Flight Diffraction (TOFD) is a non-destructive inspection technique that has proved to be very effective for the detection, localisation and sizing of buried crack defects in steel structures. However, it produces a huge amount of data that are manually processed and interpreted. This process is time consuming and painstaking. Moreover, it requires the skill, alertness and experience of the operator. Consequently, it is subject to human errors. In order to save time, effort and inspection cost while at the same time increasing the detection rate, automatic analysis tools need to be developed. This paper presents thus an application of image processing techniques to the B-scan image representation of ultrasonic TOFD data so as to take advantage of the power of image representation of information. In a B-scan image, crack defects are characterised by multiple arcs of diffraction. In order to detect these multiple arcs of diffraction and thus reveal the presence of a crack in the structure under inspection, some methods based on conventional Hough Transform (HT) were proposed in the literature. The main problems related to conventional HT are its large data storage requirements and expensive computation times. To cope with these problems, we propose the use of the Inverse Hough Transform (IHT) where the voting process is performed in the image space rather than the parameter space. With the IHT, the local peak detection problem in the parameter space is converted to a parameter optimisation problem that is solved using Genetic Algorithms. The proposed Genetic-Based Inverse Voting Hough Transform 'GBIVHT' algorithm allows thus the automatic detection of the arcs of diffraction, and therefore the crack defects, while avoiding the computational complexity as well as the huge storage requirement of conventional HT.

Reliability Analysis of Time of Flight Diffraction Characterization of Inclined Cracks

Abstract: This paper presents the reliability analysis of a manual ultrasonic time of flight diffraction test system for characterization of surface breaking inclined cracks. Probability of detection (POD) and probability of sizing (POS) curves for the detection and sizing of such cracks have been developed from experimental data. In the development of POD and POS curves, it has been assumed and subsequently verified that the signal responses (â values for an angle of inclination of the crack 0) have a normal distribution. The effects of probe angle and probe center spacing on both POD and POS have been investigated. The curves obtained in this work can be useful in risk based test planning for simple geometry components, such as pipelines and boiler headers, using a manual/automated time of flight diffraction system.

Desenvolvimento de metodologia e estudo do potencial da técnica TOFD visando a inspeção e o monitoramento de equipamentos

Abstract: With the constant growth of the domestic industry, the demand for the development of efficient tools for inspection and monitoring of structural integrity of equipment and structures also grows. Among these, non-destructive testing have been used. Considering to the non-destructive techniques applied to inspection of components used in oil industries, the use of the conventional ultra-sound technique for location and sizing of defects has proved to be important. However, in the field inspections, due to the frequent lack of orientation of defects, are utilized methodologies that use many incident angles and systems analysis of signals, resulting in a slow and subjective inspection. With the increasing of demand for online inspection, the necessity for faster and more reliable processes has been raised, among these, the use of the time of flight diffraction. This work presents TOFD technique as an efficient tool to determine the height of artificials reflectors machined in samples of SAE 1022 steel, from calibration according to British Standard 7706:1993. For this, it was elaborated a methodology using four different variations (frequency / angle) of inspection, verifying the potential of the method in analysis of different heights, in order to apply in inspection and monitoring of equipments. Results show that as for notches breaking in the surface inspected as for notches breaking in the inside surface, opposite the scanned surface, sizing can be precise, if the correct variation (frequency / angle) for each case was chosen.

Material Damage Ultrasonic Assessment by Time-of-Flight Estimation with an Adaptive Wavelet Filter

Abstract: In this paper, a new digital signal processing method for ultrasonic time-of-flight diffraction (TOFD) estimation is presented. This method is based on wavelet analysis using the Morlet mother wavelet and the least mean squares (LMS) filter. It is designed to remove noise and identify the echo starting point of the ultrasonic signal reflected from the tip of a crack. Both simulated data and experimental data obtained from a steel plate with a crack are used to demonstrate the performance of the proposed method. This method is especially useful when the properties of the ultrasonic crack signal are unknown and the noise is heavy.

Application of Tofd Detection Technology to Periodical Inspection of Pressure Vessels

Abstract: TOFD detection technology is applied to the verification of excessive defects in the spherical tank periodical survey.A defect is determined to a suspected crack by analysis of defect map and the conventional test results,and the determination is proved to be true by the on-site grinding results.Compared with the three kinds of test results and the actual crack,the effect of TOFD detection is better than the conventional detection methods which the risk defects are easily undetected in the spherical tank.

Design and construction of a system for non-destructive inspection of faults and defects in metals using ultrasonic signals

Abstract: The present paper describes the design and construction of an electronic system for non-destructive inspection with ultrasound (NDTU), which is one of the most used techniques to evaluate without deteriorating metallic parts in several areas of the industry. The evaluation techniques that appear in this document are Time of Flight Diffraction (TOFD) and pulse-echo, for which, defects in welded metallic unions were incorporated deliberately (test plates). The implemented system consists of two angular transducers according to the technique used in each case, a pulser that suitably feeds the transducer, the methodologies of acquisition and digital processing of the information. In the document, A-Scan and D-Scan graphs that illustrate a typical case of analysis as example are included. Finally, the developed system has demonstrated to be effective, compared with examinations made using a commercial equipment of the same nature, and with another technique of inspection like radiography.

POD generator project: A numerical assessment of the inspection of fatigue cracks using TOFD

Abstract: Risk based inspection strategies rely on detailed knowledge of the performance of inspection techniques. The objective of the "POD generator" project is to develop a numerical modeling approach to assess the effectiveness of specific inspection techniques. Simulation offers flexibility and reliability at acceptable costs. Therefore numerical models have been developed and validated for accurately simulating the physics of inspection techniques. These numerical models are then used to generate quantitative probability of detection (POD) curves. In the case of ultrasonic time-of-flight-diffraction (TOFD) inspections, the human factor is included on two levels. First in the way a TOFD scan is carried out (positioning variations). And secondly, in the fact that simulated inspection results are interpreted by real operators. This paper shows the assessment of the inspection of fatigue cracks using TOFD using this numerical approach. The influence of high-low and the human interpretation on the performance of the inspection was investigated by generating multiple POD-curves under different circumstances. This way we show that the numerical modeling approach is an efficient and reliable way of determining the sensitivity of inspection techniques for complex influencing factors.

Device and method for the non-destructive testing of a test object by way of ultrasound TOFD technology

Abstract: The invention relates to a device for the non-destructive ultrasound testing of a test object, said device comprising: at least one ultrasound transmitter (1, 19) with at least one radiating surface (30) facing the test object for the production of an ultrasound field that at least partially penetrates the test object (3), at least one ultrasound receiver (2) for at least partial detection of the ultrasound field and for conversion to an electric measurement signal, an evaluation unit for the evaluation of the measurement signal in TOFD technology. The device is characterized in that the radiating surface (30) is curved in at least one direction or the radiating surfaces define a surface that is curved in at least one direction. The invention further relates to an associated method.

Crack Size Estimation Using a Combination of Cross Correlation and Phase Shift Correction in Ultrasonic Time-of-Flight Diffraction Method

Abstract: The ultrasonic time-of-flight-diffraction (TOFD) detection method has been widely used in crack size assessment. The key issue in TOFD is to determine the arrival time of crack tip diffracted signal. In the traditional cross correlation method, the resulting maximum peak of cross correlation function between two signals indicates the time of flight between them. In practical ultrasonic measurement, the transmission wave may be distorted and phase shift may be introduced. This paper presents a method using cross correlation and phase shift correction to improve the accuracy of crack sizing in the TOFD framework. The resulting maximum peak of the cross correlation function between two signals combining with time delay introduced by phase shift determine the arrival time of diffracted signal. Experimental results are used to demonstrate the advantage of the proposed method.