Showing papers on "Ultrasonic testing published in 2003"

Acousto-ultrasonic sensing using fiber Bragg gratings

Abstract: This paper describes a fiber-optic system which is able to detect ultrasound in structures. The aim of the sensing system is to monitor structures, in particular aircraft structures, by detecting ultrasonic Lamb waves. This type of monitoring technique has recently become a key topic in structural health monitoring. Most common approaches use piezoceramic devices to launch and receive the ultrasound. A new way of fiber-optic detection of Lamb waves is based on fiber Bragg grating sensors. In addition to the well known advantages of fiber-optic sensors, this new interrogation scheme allows the use of Bragg gratings for both high-resolution strain and high-speed ultrasound detection. The focus of the paper is on the ultrasonic part of the system. The theoretical approach and the implementation into a laboratory set-up are elaborated. Experiments have been carried out to calibrate the system and first results on simple structures show the feasibility of the system for sensing ultrasonic Lamb waves.

Disposable ultrasonic soft tissue cutting and coagulation systems

Abstract: An ultrasonic surgical system is presented that is economical to produce and utilize, by including at least one disposable component. The ultrasonic surgical system includes an ultrasonic transducer for converting electric signals into ultrasonic vibrations. An ultrasonic transmission coupler is connected to the transducer, so as to receive the ultrasonic vibrations from the transducer. An ultrasonic vibration element is coupled to the distal end of the ultrasonic transmission coupler. At least one of the ultrasonic transducer, the ultrasonic transmission coupler, and the ultrasonic vibration element is disposable. The components of the ultrasonic surgical system are not precision-cut, and are adapted to be press-fit onto each other. The ultrasonic surgical system may be tuned to a desired resonant frequency by varying the lengths of the disposable components.

Nondestructive measurement of concrete strength gain by an ultrasonic wave reflection method

Abstract: A one-sided, nondestructive, ultrasonic technique for monitoring the setting and hardening process of concrete has recently been developed. The technique is based on monitoring the reflection coefficient of ultrasonic transverse waves at the surface of a laboratory scale hardening concrete in steel molds. The technique has been shown to reliably estimate the rate of strength gain of concrete under isothermal and outdoor conditions. Results of an experimental study to investigate the influence of curing temperature and mix design on the rate of strength gain and the ultrasonic transverse wave reflection loss are presented in this paper. Simultaneous measurements of wave reflection loss and compressive strength have been performed on various concrete compositions under different curing conditions. The ultrasonic technique is shown to produce reliable estimates of the rate of strength gain at early ages.

Guided wave helical ultrasonic tomography of pipes

Abstract: Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT) that uses guided ultrasonic waves along with tomographic reconstruction algorithms that have been developed by seismologists for what they call "cross borehole" tomography. In HUT, the Lamb-like guided waves travel the various helical criss-cross paths between two parallel circumferential transducer arrays instead of the planar criss-cross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. In this paper we demonstrate HUT via laboratory scans on steel pipe segments into which controlled thinnings have been introduced.

Grain size influence on ultrasonic velocities and attenuation

Abstract: During the last two decades, ultrasonic testing was developed as an efficient tool for materials characterization Acoustical waves by their passage through materials, carry out a multitude of information contained in the signal on the mechanical and physical properties of the material under inspection In this paper, an experimental study on steel samples has been performed to study the evolution of some ultrasonic parameters such as wave velocities and attenuation coefficients as function of the steel grains size The experimental results obtained are discussed and analyzed in order to develop an ultrasonic non-destructive technique to grains size determination

Laser-air, hybrid, ultrasonic testing of railroad wheels

Abstract: A remote, non-contact system for detecting a defect in a railroad wheel as the wheel is stationary or moving along a railroad track includes; (1) a pulsed, laser light source for generating an ultrasonic wave in the wheel, the ultrasonic wave having a direct portion and reflected and transmitted portions if the direct portion encounters a defect in the wheel, (2) an optical component in the path of the light from the light source for forming the light into a specified illumination pattern so that the generated ultrasonic wave has a specified wavefront, (3) an air-coupled transducer or a group of transducers for sensing the acoustic signal emanating from the wheel that results from the ultrasonic wave traveling through the wheel, and (4) a signal processor, responsive to the sensed acoustic signal, capable of distinguishing whether the sensed signal has a component that indicates the existence of a reflected portion in the ultrasonic wave, wherein the presence of such a component in the acoustic signal indicates the existence of a defect in the railroad wheel.

Rapid inspection of composite skin-honeycomb core structures with ultrasonic guided waves

Abstract: Guided wave inspection of composite skin-honeycomb core structures is an efficient and sensitive alternative to other common inspection methods. This paper shows that sweeping experimentally through the dispersion curves is an effective way to experimentally locate guided wave modes sensitive to skin-core delamination. Composite skin-Nomex honeycomb core specimens were developed with simulated delaminated areas. The delaminated areas were detected with guided waves and confirmed with conventional ultrasonic testing methods. Calculated phase velocity dispersion curves are given to define the practical phase velocity and frequency ranges. Example wave structures in this range are given to illustrate the change in sensitivity as frequency is swept for a given mode.

Reconstruction of the Normal Velocity Distribution on the Surface of an Ultrasonic Transducer from the Acoustic Pressure Measured on a Reference Surface

Abstract: In piezoceramic ultrasonic transducers, the thickness vibrations are usually accompanied by the excitation of Lamb waves, which are difficult to control. Therefore, the normal velocity distribution over the radiating surface is unknown. As a result, the ultrasonic field generated by the transducer cannot be predicted with the desired accuracy. The purpose of this study is to develop and experimentally validate a new method for evaluating the normal velocity distribution over the surface of an ultrasonic transducer. The method consists in measuring the amplitude and phase of the acoustic pressure field over a certain reference surface and then calculating the acoustic field at the transducer by using the Rayleigh integral. The accuracy and stability of the method are illustrated numerically. The method is tested experimentally with a focused piezoceramic transducer. In the experiment, the reference surface is represented by a plane perpendicular to the axis of the acoustic beam. The ultrasonic field is scanned by a needle hydrophone, which is moved by a micropositioner. The measurements show that the method provides an accurate prediction of the acoustic field generated by a source with an unknown nonuniform normal velocity distribution.

Ultrasonic leaky-lamb wave imaging through a highly contrasting layer

Abstract: This article presents an innovative and effective ultrasonic technique to image through a steel layer with immersion transducers. The purpose is to detect scatterers and external interfaces and evaluate the acoustic properties of materials bonded to the steel layer. The technique is based on the lowest-order antisymmetric leaky lamb wave propagating in the steel layer and is implemented through a pitch-catch transmitter-receiver arrangement. The main application presented herein is for a measurement that takes place in an oilfield well to evaluate the quality of the cement sheath that fills the annular region between steel casing and a rock formation. Current ultrasonic imaging techniques for such an application are based on the pulse-echo mode with a single trans-receiver. Because of the large acoustic impedance contrast between the steel and its surrounding media: fluid on the side of the transducers and cement, or fluid/mud on the other, pulse-echo techniques have proven to be limited to probing only the region adjacent to the casing-cement interface. Using field data acquired with an experimental device, we show that the proposed leaky-lamb wave-based imaging technique provides reflection echoes that allow for probing of the entire cement sheath and in particular of the imaging of the external cement-rock interface geometry.

Nondestructive measurement of porosity in thermal barrier coatings

Abstract: Porosity is an integral part of thermal barrier coatings (TBC) and is required to provide thermal insulation and to accommodate operational thermal stresses. The effective use of TBC in hot-section components of aircraft engines requires nondestructive testing (NDT) methods to detect porosity variations and measure thickness changes to reduce the risk of damage to the coating due to such variations. The eddy current method has been used to measure the thickness of a plasma-sprayed TBC coating and either ultrasonic or capacitance techniques have been applied to assess porosity content based on thickness values obtained using the eddy current tests. The porosity values estimated by the NDT methods have been confirmed by destructive testing, which included metallography and vacuum volumetric measurement using nitrogen absorption.

Single mode extraction from multiple modes of lamb wave and its application to defect detection

Abstract: Lamb waves generally consist of many dispersive modes, which makes mode identification difficult. This study describes the extraction of a single mode from multiple modes. The single mode extraction is based on two-dimensional Fast Fourier Transform (2D FFT) in time and space, signal filtering, and 2D inverse FFT. An air-coupled ultrasonic technique was adopted for non-contact fast measurements. Using this technique, the A0 and S0 mode were clearly detected in preliminary tests of intact plates. Furthermore, multiple reflections of the A0 mode, which were shown only in the computer simulation, were experimentally confirmed in reflection tests of plates with a rectangular notch. In the reflection tests, two reflected waves were extracted in the intervals corresponding to notch widths.

Two dimensional phased arrays for volumetric ultrasonic inspection and methods of use

Abstract: The present disclosure provides for the application of a two-dimensional ultrasonic phased array ( 100 ), formed of a plurality of transducers ( 102 ) arranged in a rectilinear pattern, for material and volumetric component testing. The two-dimensional array enables electronic adjustment of the focal properties and size of the aperture in both the azimuthal and elevational directions such that uniform and/or specified sound field characteristics can be obtained at any or all locations in the component being tested.

Ultrasonic inspection method and device

Abstract: PROBLEM TO BE SOLVED: To provide an ultrasonic inspection method and device that, in inspecting an inspection object having a complicated shape part such as a rotor blade implanting part of a turbine rotor, clarify a correspondence between the shape of the inspection object and an echo on a flaw detection image and facilitate identification of a defective echo appearing at a defect-assumed position without requiring a highly precise probe scanning tool or position detection means.SOLUTION: An ultrasonic inspection method for detecting a defect generated in an inspection object while electronically scanning an ultrasonic beam with an array type probe, comprises: associating a reflection source position on a shape diagram of the inspection object with a shape echo on a flaw detection image; generating a corrected flaw detection image in which correction is performed to the flaw detection image so that the display position of the shape echo matches the reflection source position on the basis of a positional relation between the reflection source position and the shape echo; and displaying the corrected flaw detection image in such a manner as to superimpose the corrected flaw detection image on the shape diagram.

Thermal imaging system for detecting defects

Abstract: A thermal imaging system for detecting cracks and defects in a structure. An ultrasonic transducer is coupled to the structure through a malleable coupler. Ultrasonic energy from the transducer causes the defects to heat up, which is detected by a thermal camera. A control unit is employed to provide timing and control for the operation of the ultrasonic transducer and the camera.

Method for producing homogeneous fine grain titanium materials suitable for ultrasonic inspection

Abstract: A titanium material production method for producing homogeneous fine grain titanium material in which the titanium material has a grain size in a range from about 5 μm to about 20 μm. The method comprises providing a titanium material blank; conducting a first heat treatment on the titanium material blank to heat the titanium material blank to a β-range; quenching the titanium material blank from the β-region to the α+β-region; forging the titanium material blank; and conducting a second heat treatment on the titanium material blank. The titanium material production method subjects the titanium material blank to superplasticity conditions during part of the titanium material production method.

Ultrasonic NDE of railroad tracks: air-coupled cross-sectional inspection and long-range inspection

Abstract: Two methods for the detection of structural defects in railroad tracks are discussed. The first method employs air-coupled ultrasonic testing for non-contact probing and ease of transducer positioning. It is shown that resonant standing waves can be successfully generated in the rail cross-section to alleviate the challenges associated with the large acoustic impedance mismatch between air and steel. The cross-sectional inspection is particularly well-suited for the detection of longitudinal defects. The second method uses structural vibrations of the track for long-range detection of transverse and oblique defects. In the presence of various defect types and sizes, the reflection coefficient spectra of broadband longitudinal, vertical and lateral vibrations are extracted by a joint time-frequency analysis based on the wavelet transform. These results can be useful for the development of a rail defect detection system based on automatic pattern recognition.

MEMS ultrasonic transducers for the testing of solids

Abstract: Arrays of capacitive diaphragm ultrasonic transducers could potentially be used for non-destructive ultrasonic testing and structural monitoring. In this paper, we consider the efficiency of coupling of these transducers to solid media. We show that efficient coupling can be realized by using a silicone coating as a coupling medium. We present the results of experimental characterization of ultrasonic transducers coupled to solids in this way. We show that these transducers can be used with piezoelectric emitting transducers within the range from 1 to 5 MHz, and we demonstrate the use of several transducers as a phased array to determine the direction and distance of an ultrasonic source.

Ultrasonic inspection method

Abstract: An ultrasonic inspection method includes exciting a first set of transducers in an array to introduce ultrasonic energy into a component, generating a number of echo signals using a second set of transducers in the array as receive elements, and processing the echo signals. The first and second sets of transducers are exclusive of one another, and the first and second sets of transducers are interleaved.

Investigation of Centreline Segregation and Centreline Porosity in CC - Slabs

Abstract: Improvements of solidification processing in conventional or near net shape casting depend on sophisticated methods of macroscopic examination of central unsoundness and inhomogeneity of the cast material. As long as remarkable deviations referring to the quality features exist between the slab centre and the bulk material such methods should be looked after. Two semi-macroscopic methods of segregation analysis are discussed in this paper: firstly, the potential of the emission spectral analysis combined with sectioning of a sample and secondly, the computer aided micro-probe analysis. Both methods are restricted to small local areas. The proneness of elements and steel grades with respect to micro- and macrosegregation as well as distribution- and segregation coefficients are determined. The effect of a diffusion anneal on homogenisation of segregation is studied. Last not least the precipitation of sulphides, phosphides or carbonitrides is estimated. Ultrasonic detection of the central unsoundness of conventional slabs or thin slabs is a new approach towards a quantitative macroscopic examination. The sample size is 400 mm x 300 mm x 30 mm. To achieve a low ultrasonic noise using a 5 MHz-transducer the samples are heat treated for grain refinement. Dog bone porosity, macroscopic topographical misfit between the upper and lower solidifying shells, periodical corner cracks or systematic transverse centre cracks are detected. Obviously, segregations do not reflect the ultrasonic beam. However, it can be presumed that an interrelation exists between porosity and segregation, although these might be locally apart from each other. This new ultrasonic test of the central unsoundness of continuous cast (c.c.) slabs gives valuable arguments to machine builders and maintenance people to decide on the right concepts for strand guidance, support rollers and secondary cooling. Soft reduction can be optimized and variations in casting speed counteracted by dynamic means. R&D service of this kind can help steelmakers when decisions are impending to build new casting machines or revamp old ones.

New techniques for the design of advanced ultrasonic transducers for wire bonding

Abstract: A new high-frequency ultrasonic transducer, in particular for the application wire-bonding, has been conceived, designed, prototyped, and tested. In the design phase an advanced approach was used and established. The method is based on the two basic principles of modularity and iteration. The transducer is decomposed in its elementary components. For each component an initial draft is obtained with finite-elements-method simulations (FEM). The simulated ultrasonic modules are then built and characterized experimentally through laser-interferometry measurements and electrical resonance spectra. The comparison of simulation results with experimental data allows the parameters of FEM models to be iteratively adjusted and optimized. The achieved FEM simulations exhibit a remarkably high predictive potential and allow full control on the vibration behavior of the ultrasonic modules and of the whole transducer. The new transducer is fixed on the welding device with a flange whose special geometry was calculated by means of FEM simulations. This flange allows the converter to be attached on the welding device not only in longitudinal nodes but also in radial nodes of the ultrasonic field excited in the horn. This leads to a total decoupling of the transducer to the welding device, which has so far been unheard of. The new approach to mount ultrasonic transducers on a welding-device is of major importance not only for wire-bonding but also for all high-power ultrasound applications.

Nonlinear Laser Ultrasonic Measurements of Localized Fatigue Damage

Abstract: A nonlinear laser ultrasonic system was developed and used to characterize the fatigue state of a fractured Ti‐6Al‐4V sample with high spatial‐resolution and sensitivity. The measurement system is built around a scanning heterodyne interferometer, which allows detailed displacement field images to be created and visualized for propagating surface and bulk acoustic fields on a material surface. An assessment of the local fatigue damage of the material was made using nonlinear ultrasonic interaction principles, where the local amplitudes of the fundamental and second harmonic displacement fields are monitored simultaneously. This provides a means for evaluating the local acoustical nonlinearity parameter, β, which can be related to the accumulation of fatigue damage in a material. A large increase in β was observed between the unfatigued area (near the grip section) and the heavily fatigued area (gauge section) for a fractured dogbone specimen. The measurements show the potential for spatially‐resolving the local fatigue state of a material using laser ultrasonics.

Dry-contact technique for high-resolution ultrasonic imaging

Abstract: To accomplish a high-resolution ultrasonic imaging without wetting a sample, the efficiency of the dry-contact ultrasonic transmission is discussed. In this study, a dry-contact interface is formed on a sample by inserting a thin film between water and a sample, and the pressure is working on the interface by evacuating the air between the film and the sample. A model of dry-contact ultrasonic transmission is presented to assess the signal loss accompanied with the transmission. From the determination of the signal loss caused by the transmission using various films, it was found that the higher frequency ultrasound is transmitted effectively into the sample by selecting an optimum film, which can keep the displacement continuity between the film and the sample during ultrasonic transmission. Finally, ultrasonic imaging with the sufficient signal-to-noise ratio (SNR) and high lateral resolution was performed on the delamination in a package and the jointing interface of the ball-grid-array package without wetting the packages.

Ultra-low noise front-end electronics for air-coupled ultrasonic non-destructive evaluation

Abstract: Air-coupled ultrasonic inspection has been demonstrated to be a non-contact method of great interest in non-destructive evaluation (NDE) applications. The absence of direct contact or a liquid couplant provides this technique very attractive benefits in front of the well-known and well-developed liquid-coupled ultrasonic inspection systems. A wide range of defects can be detected by means of ultrasound coupled to and harvested from the specimen in absence of contact when using appropriate transducers designed for their operation in air. This paper presents an easy way to integrate air-coupled piezoelectric transducers in conventional ultrasonic NDE equipment. The design of a specific front-end electronics by using an ultra-low noise amplifier enables existing inspection systems to be used for the dry-coupled ultrasonic test of materials and structures. The amplifier provides the receiver with a signal-to-noise ratio large enough for good quality signal processing and imaging. System dynamic ranges of more than 100 dB are achieved.

A system for high-resolution, nondestructive, ultrasonic imaging of weld grains

Abstract: The purpose of nondestructive evaluation is to detect degradation so that corrective action can be taken before the degradation challenges the structural integrity of an industrial system or one of its components. Accurate characterization is required to distinguish progressive degradation from benign material conditions. In nondestructive evaluation, characterization includes quantification and description of location, dimensions, shape, orientation, and composition of an indication of degradation. An imaging system that uses synthetic aperture focusing is one choice for detection and characterization of degradation in welded assemblies. In this paper, the ultrasonic imaging of the intended weld microstructure is reported. New technology invented for this purpose is described. This paper reviews how an ultrasonic imaging system that uses a synthetic lens can have a resolution that approaches the diffraction limit. A constrained solution to the coherent summation problem is presented for near real-time performance in high-resolution synthetic aperture focusing. Data are included to show that nondestructive, ultrasonic imaging of weld grains is practical.

Method and apparatus for airborne ultrasonic testing of package and container seals

Abstract: A method for testing or inspecting the integrity of package closure seals using contact and non-contact ultrasonic systems wherein a relative movement is created between a package seal and at least one ultrasonic transmitting transducer and at least one receiving transducer such that ultrasonic energy is focused so as to be transmitted toward and along a length of the seal from the transmitting transducer to the receiving transducer in a gaseous environment to thereby monitor energy signals which are analyzed to provide an indication of the seal integrity.

Ultrasonic flowmeter and ultrasonic flowmetering method

Abstract: An ultrasonic flowmeter (10) comprises a trigger oscillating apparatus (14); a pulser receiver (16); a transducer (20) responsive to an electric signal from the pulser receiver (16) for emitting ultrasonic pulses toward a measurement line (ML) within a fluid pipe (22); signal processing means (27) for processing an ultrasonic echo signal that is a reflected wave from the transducer (20); flow velocity distribution calculating means (28) for analyzing the processed ultrasonic echo signal to determine the position and velocity of the ultrasonic reflecting body along the measurement line (ML); and flow rate calculating means (29). The signal processing means (27) comprises a filtering part (21) for filtering the ultrasonic echo signal, and an AD converter (17) for performing AD conversion. The trigger oscillating apparatus (14) is adapted to control the timings of signal transmission/reception between the pulser receiver (16) and the AD converter (17), and also adapted to have a predetermined wait time after causing the ultrasonic pulse oscillation and ultrasonic echo signal reception to successively occur a plurality of times. This structure can precisely flowmeter not only fluids that could be conventionally flowmetered but also fluids that are relatively clean and hence conventionally difficult to flowmeter.