Showing papers on "Ultrasonic testing published in 1995"

Ultrasonic diagnosis and treatment system

Abstract: An ultrasonic diagnosis and treatment system having a thin tube which is capable of being inserted into a body cavity, and which has at its extreme end an observing ultrasonic vibrator for emitting ultrasonic waves for observation and a treating ultrasonic vibrator for emitting strong ultrasonic waves for treatment. Observation and treatment are performed by using ultrasonic wave. The system further includes a processing device for performing an operation other than the ultrasonic treatment at least on a region observed by using ultrasonic waves. A guide for enabling the processing device to reach the region observed by using ultrasonic waves is provided on the thin tube.

Frequency-Dependent Stress Wave Attenuation in Cement-Based Materials

Abstract: Ultrasonic techniques are widely used, reliable form of nondestructive testing of materials. The nature of concrete as a heterogeneous mixture make it somewhat ill-suited as a conductor of stress waves, and therefore makes the interpretation of ultrasonic data difficult. In order to quantify the attenuation of ultrasonic waves in concrete, a point source/point receiver (PS/PR) ultrasonic test system was set up, and the individual components were evaluated. PS/PR can be used to quantify (among other things) the ultrasonic attenuation in the materials. The technique was applied to a series of four portland-cement-based test specimens. These specimens ranged from a fine cement paste to concrete sample with a maximum aggregate size of 10 mm. The frequency-dependent attenuation was evaluated for each specimen. The results of this investigation showed that the wave-propagation characteristics of the materials can be quantified with this technique, and that certain characteristics of the attenuation curves can linked to the degree of inhomogeniety in the material.

Portable laser/ultrasonic method for nondestructive inspection of complex structures

Abstract: A method and apparatus for non-destructive inspection of complex structures employs a portable laser based ultrasonic transducer 600 output to rapidly detect and size flaws in such structures, including the radii of composites, laminates, and complex skin/substructure assemblies, such as airplane wings. A fiber optic delivery system 610A is employed with the laser based ultrasonic transducer 600 and a thermoelastic medium to rapidly and accurately access the radii of complex structures in the field without the need for liquid or gel couplants, with the thermoelastic expansion of the test piece 680 producing mechanical stresses that initiate detectable sound waves regardless of the angle of the laser based ultrasonic transducer 600 output with respect to the test piece 680. A MAUS III scanning device may be employed to detect these sound waves and provide accurate information as to the detected flaws.

Ultrasonic probe modeling and nondestructive crack detection

Abstract: The mathematical modeling of a typical situation in ultrasonic nondestructive testing for defects is considered. The first objective is the modeling of a reasonably general type of ultrasonic probe. This is performed by prescribing the traction vector on the surface of an elastic half‐space. The effective probe area may be rectangular or elliptic and the traction may or may not include the tangential part (glued or fluid‐coupled probe, respectively). The probe can be of P, SV, or SH type and of any angle. The traction is either constant across the probe (piston‐type source) or it may taper off toward the edges. Numerical results for some representative cases are given showing snapshots of the field beneath the probe. The second objective of the paper is to include the presented probe model into a complete model of the ultrasonic testing situation. To this end the probe field is, via a series of transformations, expressed in spherical vector waves centered at the defect. The influence of the defect is give...

Ultrasonic signal-processing techniques for the measurement of damage growth in structural materials

Abstract: In recent years, the ultrasonic signal-processing technique, which has been enormously successful in material testing, has found few applications in the analysis of concrete damage because of the heterogeneous nature of this material. In the present study, frequency-domain analysis of the ultrasonic signals, based on the Segmented Chirp Z-Transform, has been used to both detect and monitor the crack growth in structural materials. In comparison with the usual methods of pulse velocity or attenuation measurement, a very sensitive and accurate testing method was obtained. The experimental setup is described and the preliminary results, relating to uniaxial compression tests carried out on cubic concrete specimens and bricks, discussed. >

Ultrasonic printing apparatus and method in which the phases of the ultrasonic oscillators are controlled to prevent unwanted phase cancellations

Abstract: An ultrasonic printing method by which recording of a high resolution can be achieved. In the ultrasonic printing method, some or all of a plurality of ultrasonic oscillators are selectively driven in such phases that a difference in phase at a predetermined point between a reference ultrasonic wave from one of the selected ultrasonic oscillators and another ultrasonic wave from any other one of the selected ultrasonic oscillators is equal to or less than one-fourth a wavelength of the ultrasonic waves in a transmission medium for the ultrasonic waves from the selected ultrasonic waves to the predetermined point. The ultrasonic printing method can be applied to various printing apparatus for which recording of a high resolution is required.

Application of the LCR ultrasonic technique for evaluation of post-weld heat treatment in steel plates

Abstract: Ultrasonic travel times obtained with the LcR wave are able to distinguish between stress relieved and non-stress relieved 13 mm ( 1 2 in ) thick, steel plates. Two 1.22 m (48 in) square plates were patch welded in the centre to create a residual stress field, and one of the plates was stress relieved. The LcR ultrasonic technique sends a critically refracted longitudinal wave travelling beneath the plate surface, and the stresses in the plate affect the travel times through the acoustoelastic relationship. The LCR travel-time measurements not only distinguished between residual stress states in the plate, but also gave some information on their distribution and magnitude. Neither texture nor localized residual stresses affect the results. These findings demonstrate the potential usefulness of the technique for evaluating the state of post-weld heat treatment in structural steels.

Measurement of physical characteristics of materials by ultrasonic methods

Abstract: A method is described for determining and evaluating physical characteristics of a material. In particular, the present invention provides for determining and evaluating the anisotropic characteristics of materials, especially those resulting from such manufacturing processes as rolling, forming, extruding, drawing, forging, etc. In operation, a complex ultrasonic wave is created in the material of interest by any method. The wave form may be any combination of wave types and modes and is not limited to fundamental plate modes. The velocity of propagation of selected components which make up the complex ultrasonic wave are measured and evaluated to determine the physical characteristics of the material including, texture, strain/stress, grain size, crystal structure, etc.

In situ thin film thickness measurement with acoustic Lamb waves

Abstract: In situ thin film thickness measurement is an important problem in semiconductor processing, which is currently limited by the lack of adequate sensors. Most of today’s available techniques are restricted to certain type of films and many have difficulties in performing the measurement in situ. The fact that the velocity of an ultrasonic Lamb wave traveling in a silicon wafer is changed by the thin film coating on the wafer surface can be used as a monitoring method for basically any type of film—opaque, transparent, metal, or insulator. The acoustic sensors are easily implemented into plasma or CVD environments. We have demonstrated the technique in an aluminum sputtering system in which we measure Al film thickness with a resolution of ±100 A. Even better resolution can be achieved for SiO2, copper, and tungsten films. This system has a variety of potential applications, not only in film thickness measurement, but also in characterization of film properties and multilayer deposition process control.

Electroacoustic model for electrostatic ultrasonic transducers with V-grooved backplates

Abstract: Capacitive ultrasonic transducers are widely used to generate airborne ultrasound. This paper presents an equivalent circuit for an electrostatic transducer with a V-grooved backplate. The comparison between simulation results and measurements on a prototype transducer shows that the model gives reliable results. This model is useful in many applications, for example to simulate sensors in a robot and to design ultrasonic transducer systems. >

Narrow-Band Hybrid Pulsed Laser/EMAT System for Non-Contact Ultrasonic Inspection Using Angled Shear Waves

Abstract: Conventional ultrasonic testing (UT) using angled shear waves to locate and size potentially critical cracks and flaws in power generation and refinery equipment has become a widely utilized industrial tool. Because this technique uses piezoelectric transducers it requires intimate surface contact and fluid couplants. Therefore, conventional UT has the important drawback that it is difficult to use on surfaces at elevated temperature and, as a result, may require costly plant shut downs to implement. The development of non-contact techniques for angled shear wave UT would represent a significant improvement in the ability to test hot vessels and pipes.

Rationale and summary of methods for determining ultrasonic properties of materials at Lawrence Livermore National Laboratory

Abstract: This report is a summary of the methods used to determine ultrasonic velocities through the many materials tested at the Acoustic Properties of Materials Laboratory. Ultrasonic velocity techniques enable the determination of material properties, including elastic moduli, without harming the materials being tested, an advantage some over mechanical methods. Ultrasonic modulus determination has other advantages as well: (1) relative ease and low cost of material preparation; and (2) comparative analysis to physical testing as a function of material loading rate dependence. In addition, ultrasonic measurement provides clues to determine grain size and orientation, and provides a relative indication of material anisotropy with respect to the material geometry. The authors usually perform ultrasonic measurements on materials in ambient atmospheric conditions, and in a relatively free-free condition. However, the authors can perform them in other environments, as required. This paper describes some of the techniques used in this laboratory and shows how ultrasonic velocities are used to establish elastic constants. It also includes a sample test report for a homogeneous isotropic solid, along with a list of references.

Influence of Columnar Microstructure on Ultrasonic Backscattering

Abstract: Most structural materials are polycrystalline, that is, they are composed of numerous discrete grains, each having a regular, crystalline atomic structure The elastic properties of the grains are anisotropic and their crystallographic axes are differently oriented When an ultrasonic wave propagates through such a polycrystalline aggregate, it is scattered at the grain boundaries The fraction of sound energy thus removed from the main beam is responsible for important phenomenons like attenuation and dispersion of the main beam, and background “noise” associated with a given ultrasonic inspection system The amount of sound energy removed from the main beam depends on the size, shape, and orientation distributions of the grains If the grains are equiaxed and randomly oriented, propagation direction of the ultrasonic wave has no effect upon the magnitude of the scattered energy Such is not the case when an acoustic wave travels through materials like centrifugally cast stainless steel and austenitic stainless steel welds, which are used extensively in nuclear power plants The microstructures of these stainless steels vary from randomly oriented, equiaxed grains to highly oriented, columnar grains1,2 Since the backscattered signals tend to mask the signals from small and subtle defects, the estimation of probability of detection of such defects requires quantitative description of these signals Consequently, an effort has been undertaken in this research to quantify the backscattered signals from microstructures with favored grain orientation and grain elongation

Ultrasonic characterization of elastic anisotropy in plasma-sprayed alumina coatings

Abstract: An ultrasonic, nondestructive contact measurement technique was employed to detect and characterize the elastic anisotropy of a free-standing, plasma-sprayed alumina coating. Following this initial evalu-ation, a computer-assisted, ultrasonic anisotropic test bed was used to determine the anisotropic elastic stiffness constants of coatings produced by plasma gun currents of 600 and 400 A. The results showed that the plasma-sprayed alumina coatings are transversely isotropic; i.e., isotropic in the spraying direction. These coatings were characterized by five independent elastic stiffness constants. Coatings produced at 600 A plasma gun current showed higher elastic stiffness constants than those produced at 400 A plasma gun current. This increase appeared to be related to a decrease in the porosity content of the coatings pro-duced at the higher plasma gun current.

Passive acoustic method of measuring the effective internal diameter of a pipe containing flowing fluids

Abstract: Changes in the internal diameter of a fluid handling pipes are measured by measuring the vibrational characteristics by a non-invasive, passive acoustic technique. Deviations from the normal vibrational characteristics are sensed and used to determine changes of increase or decrease in the pipe's internal diameter.

Ultrasonic testing apparatus and method for multiple diameter oilfield tubulars

Abstract: Ultrasonic testing apparatus 10 and method for ultrasonically scanning an oilfield tubular 42,56. The apparatus includes four ultrasonic arrays 12, 14, 16, 18 each containing a plurality of individual watertight ultrasonic transducers 20. Axially adjustable ultrasonic arrays 100, 121 include axially spaced sockets 102, 106, and 122, 124, 126, respectively, for controlling an axial movement thereof to preferably discrete positions associated with each selected range of diameters of oilfield tubulars to be tested. Within that range of diameters, the ultrasonic testing apparatus 10 reliably provides for a constant 100% coverage of the tubular to be tested. During scanning, the tubular 56 is moved axially and rotationally with respect to an ultrasonic testing apparatus 50 to provide a helical scan pattern along the length of the tubular 56.

Laser-Ultrasonic Inspection of the Composite Structure of an Aircraft in a Maintenance Hangar

Abstract: Composite materials used in aerospace structures can be affected by a variety of defects, such as delaminations and disbonds, which may occur during fabrication or may be caused by impact during use. Such defects, which cannot usually be detected by simple visual inspection, may severely affect the mechanical integrity of components. Ultrasonics offers the best possibility for detection of flaws in composite components. However, ultrasonics as conventionally applied using piezoelectric transducers for generation and detection of the probing pulse has several limitations. Namely, the need for an acoustic coupling media or direct contact with the surface, and the requirement of near-normal incidence to the component’s surface. Laser-ultrasonics represents a practical means of avoiding the inherent difficulties with conventional ultrasonics [1–2].

Ultrasonic medical treatment device and ultrasonic wave irradiation device

Abstract: PURPOSE: To provide the ultrasonic medical treatment device which forcibly breaks a cavitation. CONSTITUTION: The ultrasonic medical treatment device is equipped with an ultrasonic wave generation source 402 which generates an ultrasonic wave for medical treatment, and driving means 411 and 412 which drive the ultrasonic wave generation source 402 so that the frequency of the ultrasonic wave for medical treatment generated by the ultrasonic wave generation source 402 varies with the lapse of time.

The Practical Application of Grain Noise Models in Titanium Billets and Forgings

Abstract: For pulse/echo ultrasonic inspections of metal components, mathematical models have been developed which can be be used to assess the likelihood of flaw detection. For example, for various classes of simple defects (e.g., flat cracks, spheroidal inclusions), measurement models [1] based on Auld’s reciprocity relationship can predict the RF echo seen on an oscilloscope when the defect is present at some given location in the component. Other models can predict the average level of backscattered microstructural noise that is seen when no defect is present [2]. Together, the models can be used to estimate signal-to-noise ratios for defects of various types, sizes, and locations [3]. Even when all model assumptions are satisfied, accurate predictions require accurate knowledge of transducer characteristics and pertinent properties of the metal specimen. For the prediction of grain noise levels using the Independent-Scatterer Noise Model [2], for example, the required material properties are the density, wave speed, attenuation coefficient, and Figure-of-Merit (FOM) describing the contribution of the metal microstructure to the backscattered noise. In addition to the above metal properties, the geometrical focal length and effective diameter of the transducer must also be be known. All of these model inputs must be deduced by auxilary measurements.

A multizone technique for billet inspection

Abstract: An ultrasonic inspection system has been developed in response to FAA recommendations for improved inspection of titanium billet [1]. This prototype system — called Multizone — has been transitioned to the factory floor and has inspected 1,000,000+ pounds of Ti billet in 1993–94. It is a real-time, PC based platform that employs custom built analog electronics using up to 8 parallel (non-multiplexed) channels, each with a remote pulser/receiver matched to the ultrasonic transducer. Scanned helically, the billet is divided into concentric zones with a focused transducer used to acquire peak detected C-Scan image data for each zone. The depth of each zone is established by the depth of focus of that transducer. C-Scan image data from all channels are displayed simultaneously on a 1024×1280 CRT and scroll as the inspection advances along the billet length. The data are written to optical storage upon completion of the inspection. The analog electronics are fully synchronous and could provide a baseline system for the acquisition of full waveforms. Custom post scan analysis software has been developed to detect flaws using signal to noise based algorithms. This software provides more reproducible results than conventional systems and greatly reduces operator fatigue and the chance for error. This paper will discuss the system architecture and operation. A companion paper in this volume discusses inspection results. [2]

Ultrasonic technique for measuring the thickness of cladding on the inside surface of vessels from the outside diameter surface

Abstract: An ultrasonic inspection method for measuring the thickness of non-welded (non-metallurgically bonded) cladding on the inside surface of a vessel from an outside diameter surface of the vessel relies upon the occurrence of a phase change at an interface between the base metal and cladding layers to precisely determine its presence and location. By measuring the length of time for the ultrasonic pulse to propagate through the cladding material, suitable predetermined calibration standards for the cladding material in question can be used to convert the time of flight of the ultrasonic pulses through the cladding into a thickness of the cladding. The cladding thickness can be measured from an outside surface of the vessel whether or not it is empty and/or without stopping the process and/or draining it, and the method can even be employed at elevated temperatures through the use of known delay lines. Alternatively, if safe access to the interior portion of the vessel is available, an internal direct inspection can be performed to determine the thickness of the non-welded cladding using a modification of the technique in which a first multiple or second reflection signal from the base metal/cladding layer interface is used.

System for measuring ultrasonically the elastic properties of a moving paper web

Abstract: The invention relates to a system for measuring ultrasonically the elastic properties of a moving paper web. A noise type ultrasonic sound wave is generated by an ultrasonic sound generating means (4) in the web at an excitation point. A reference ultrasonic wave reradiated into the air from the excitation point is indicated. Pick-up means (M2; Mic2A, Mic2B; Mic3A, Mic3B) is provided for receiving ultrasonic sound reradiated from the paper web at a predetermined distance from the location of the sound generating means (4). The ultrasonic sound generating means (4) and the reference ultrasonic receiving means (M1,5) are provided on the same side of the paper web. At least one of these two kind of means comprises a number of elements provided symmetrically in relation to the other means.

Method for ultrasonic evaluation of materials using time of flight measurements

Abstract: A nondestructive evaluation method is described for ultrasonic evaluation and detection of features in polycrystalline materials, such as grain orientation (e.g. texturing) or grain boundary orientation. The method may, for example, be employed to detect diffusion bonds that contain undesirable planar grain boundary arrays. The method utilizes time of flight statistics gathered from reflections associated with incident ultrasonic signals directed into a plurality of locations within the material.

Calibration method using a Pitch-Catch arrangement for ultrasonic inspection of acoustically noisy materials

Abstract: A method for the ultrasonic inspection of acoustically "noisy" specimens, such as those having intrinsically coarse or variable grain structure (e.g., turbine rotor parts made of superalloy compositions), employs a "Pitch-Catch" analysis wherein a "through-transmitted" sound wave is first acquired for a plurality of reference locations on the specimen and used as a calibration standard to normalize ultrasonic inspection test data for that specimen prior to flaw/defect detection and processing. The through transmitted sound wave is also used for accurately equating the amplitude of "indications" (i.e., significant detected ultrasonic reflections)to that of a standardized theoretical reflector of known size (e.g., an equivalent "flat bottom hole" or EFBH reflector) so that the test sensitivity or "size of indications" can be uniquely determined for each specimen on which the test is performed.

Ultrasonic testing method

Abstract: A single operation, multi-task, non-destructive testing technique of ultrasonic examination for defect detection, analysis and sizing. The technique utilizes the same angle, mode of propagation, calibration, set-up, and scanning patterns, for all materials, thickness of materials, and configuration of components for which it is applicable. The technique is used to detect, analyze and size planar flaws, such as fatigue cracks, which are connected to the surface opposite that from which the ultrasound is propagated. The technique relies on the fact that specular reflections received from flaws that have penetration into materials will return to the transducer before reflections which are associated with geometric features of the surface to which the flaw is connected. It also relies on the properties of the longitudinal mode of sound propagation at a 65-75 degree angle resulting in reduced specular reflections from opposite wall geometric reflectors such as weld roots and counterbores.

The Ultrasonic Field of Focused Transducers Through a Liquid-Solid Interface

Abstract: This paper presents theoretical and experimental results on the ultrasonic field of focused immersion transducers. The French Atomic Energy Commission (C.E.A.) has developed a software which calculates the ultrasonic field produced by a focused (or unfocused) transducer through a liquid-solid interface at normal or oblique incidence. The radiation of the transducer is formulated by the method of the Rayleigh integral, extended to take into account the liquid-solid interface. Firstly we describe this model, then we present measurements of the ultrasonic field produced by focused transducers in steel blocks. Experiments have been made using, at low frequencies, an electrodynamic probe, and, at high frequencies, an optical probe.

Nondestructive evaluation of fatigue-induced changes in the structure of composites by an ultrasonic method using a laser

Abstract: Studies were conducted to nondestructively evaluate the damage to a glass-fiber-reinforced plastic during cyclic and static loading. The evaluation was made by an ultrasonic method employing a laser. In both the unloaded and loaded specimens, the ultrasound attenuation spectrum has a resonance peak attributable to the periodic nature of the structure of the composite. This peak is shifted to the low-frequency region during static loading, due to a decrease in the elastic modulus. The spectra obtained after cyclic loading have no resonance peaks, due to attenuation of the ultrasound over a broad range of frequencies by a large number of fatigue cracks. Additional static loading results in concentration of the cracks near the boundary between the glass fibers and the polymer matrix, which leads to the formation of a resonance peak in the high-frequency region of the spectrum.

An Ultrasonic Wheel Probe Alternative to Liquid Coupling

Abstract: Ultrasonic testing involves the generation of waves in a transmitting transducer, the passage of the waves from this transducer into the testpiece, passage through the testpiece often involving one or more reflections, and return to either the transmitting transducer (pulse-echo mode) or a separate receiving transducer (pitch-catch mode).