Showing papers on "Ultrasonic testing published in 1991"

Ultrasonic inspection method and apparatus with audible output

Abstract: An ultrasonic inspection system and method having an audible signal output is shown which includes an ultrasonic transducer (10) for pulse insonification of an object (12) under control of pulser (14). Echo signals are converted to electrical signals at transducer (10) and the electrical signals are supplied to an A/D converter (30) through amplifiers (18 and 20). Signals from converter (30) are processed to provide for an A-scan or B-scan display at CRT (38). Digital ultrasonic return signals from A/D converter (30) are converted to an audio frequency signal at ultrasound-to-audio converter (50). The audio frequency signal from converter (50) is converted to analog signal form at D/A converter (54) and the analog audio signal is supplied to first and second variable gain amplifiers (58 and 60) the gain of one of which is ramped up while that of the other is simultaneously ramped down. Outputs from the variable gain amplifiers (58 and 60) are supplied to spaced electro-acoustic transducers (66L and 66R) to provide an audible presentation having a stereophonic spatial effect dependent upon distance of travel of the reflected ultrasonic wave pulses. A moving cursor (40) is provided at visual display (38), the movement of cursor which is synchronized with the audible presentation.

A Technique for Quantitatively Measuring Microstructurally Induced Ultrasonic Noise

Abstract: In ultrasonic inspections of aircraft engine components, the detectability of critical defects can be limited by grain noise. This is likely to be the case for subtle defects, such as hard-alpha-phase inclusions in titanium alloys, where the difference between the acoustic impedances of the defect and host is small. A sound quantitative description of grain noise in such alloys is essential for accurate estimates of flaw detection reliability. In this work we present a method for quantifying backscattered grain noise by using positional averaging to determine the root-mean-squared (rms) noise level. The measured noise level will depend on details of the measurement system, as well as on inherent material properties of the alloy. We present a preliminary model of the noise measurement process which accounts for system effects, and we compare its predictions with experiment. We then indicate how the rms noise data can be processed to extract a factor which parameterizes the inherent noise severity independent of the measurement process.

Ultrasonic analysis of nonlinear response and strength of adhesive bonds

Abstract: A theoretical investigation has been carried out to obtain information on the adhesive bond strength from ultrasonic test results. It is postulated that failure of an adhesive bond is preceded by n...

Performance evaluation of ultrasonic examination equipment

Abstract: A test system is disclosed for facilitating analysis and evaluation of medical performance of ultrasonic examination equipment, including ultrasonic imaging systems, Doppler ultrasonic systems and ultrasonic color flow mapping systems. The test system is employed while the ultrasonic examination system is operating. A test transducer apparatus is positioned at a location at which it receives incident ultrasonic energy from the examination system. Receiver and analyzer circuitry senses and identifies characteristics of the incident ultrasonic energy being produced by the examination system, and electronically produces signals representing these sensed characteristics. A storage device is provided to preserve representations of these characteristics. Synthesizer apparatus and circuitry utilizes the stored characteristic information to actuate the test transducer apparatus to propagate back to the transducer of the examination system apparent return echoes resembling ultrasonic echoes which would have been produced by the incidence of incident ultrasonic energy upon an acoustic image, had such an acoustic image been located within the examination system's field of view. The monitored characteristics of the incident ultrasound include wave shape, frequency, phase, signal duration, pulse duration and pulse rate. The location of the apparent acoustic interface represented by the false echoes returned can be adjusted by varying the time delay of the apparent return echoes relative to the occurrence of the corresponding incident ultrasonic energy. A moving acoustic image or point thereof can be simulated by changing the frequency of the apparent echoes relative to the frequency of the incident ultrasonic energy.

Means and method for ultrasonic measurement of material properties

Abstract: The system for field measurement of texture, stress and related material properties such as formability parameters using ultrasonic velocity measurements through crystalline plate or sheet. Electromagnetic acoustic transducers are utilized to generate, transmit, and receive ultrasonic bursts through the plate at different angular orientations with respect to the plane of the plate. Two of the transducers are driven in series when generating the ultrasonic bursts. Time measurements between transmission and reception of the bursts are precisely derived and converted into velocities. Information regarding stress, texture, and other related material properties such as formability parameters can be derived from these velocity measurements. The system is adjustable to be used for both ferrous and nonferrous crystalline plate. Alteration of the types of ultrasonic waves utilized, and the methods of generating the waves allows different properties such as texture and stress to be derived.

Ultrasonic transducer with reduced acoustic cross coupling

Abstract: A continuous wave driven ultrasonic transducer for determining doppler frequency shift in reflected ultrasonic pressure waves in which the transmitter and receiver sections are constructed of a composite core having a plurality of segments of piezoelectric material separated by acoustic suppression material. Also disclosed is a method of reducing acoustic and mechanical cross coupling between piezoelectric transmitter and receiver sections of an ultrasonic transducer by arranging segments of piezoelectric material in a lateral array, and separating the piezoelectric segments with ultrasonic acoustic suppression material to produce a composite transducer core of reduced acoustic and mechanical cross coupling.

A method of and an apparatus for frequency selective ultrasonic inspection of multi-layered structures

Abstract: A method of and an apparatus for ultrasonic inspection of multi-layered structures having transmission (I, III, V and VII) and reflection (II, IV, VI and VIII) frequency bands are provided. Variations in one or more parameters of specific layers are largely restricted to the transmission bands of said layers. By analyzing transmitted or reflected signals with respect to the frequency bands of the structure, interpretation of signals due to parameter variations as caused by voids, inclusions or delaminations can be effectively eliminated. The method is preferably used for the inspection of laminated structures consisting of metal layers bonded by fibre reinforced resin layers.

Ultrasonic probe and method for operating the same

Abstract: An ultrasonic probe for ultrasonically testing screws includes an ultrasonic transducer array having a plurality of ultrasonic transducers. The ultrasonic transducers selectively operate as transmitters and receivers. Coupling bodies of solid material are each acoustically coupled to a respective one of the ultrasonic transducers. Each of the coupling bodies have a free coupling surface facing away from the respective ultrasonic transducer. The coupling surfaces are adapted to the shape of the surface of a head of a screw to be tested. The coupling surfaces are centered on the head of the screw. A method for operating an ultrasonic probe includes placing and centering the coupling surfaces on the surface of the head of the screw. Different ultrasonic transducers are operated in at least one of transmission and reception modes in each of a plurality of measuring steps, for locating and characterizing a flaw in the material of the screw.

Laser ultrasonic detection method and apparatus therefor

Abstract: A reflector/vibrator plate is irradiated with an ultrasonic generation laser beam to generate an ultrasonic wave therein, and the thus generated ultrasonic wave is transmitted into an object to be inspected. The ultrasonic wave transmitted into the inspection object returns to the reflector/vibrator plate by being reflected by a defect such as a flaw present inside the inspection object, if any, thereby causing a vibration in the reflector/vibrator plate. By detecting this vibration with an ultrasonic detection laser beam, the presence of the defect is detected and located in the inspection object. The ultrasonic flaw detection method can be applied to a variety of inspection objects including reflectors having irregularities on the surface or a poor reflectivity, inspection objects having on the surface thereof an opaque liquid which will not allow transmission of the laser beam therethrough, and inspection objects which do not permit generation of ultrasonic waves with a laser beam.

Crack detection using resonant ultrasound spectroscopy

Abstract: Method and apparatus are provided for detecting crack-like flaws in components. A plurality of exciting frequencies are generated and applied to a component in a dry condition to obtain a first ultrasonic spectrum of the component. The component is then wet with a selected liquid to penetrate any crack-like flaws in the component. The plurality of exciting frequencies are again applied to the component and a second ultrasonic spectrum of the component is obtained. The wet and dry ultrasonic spectra are then analyzed to determine the second harmonic components in each of the ultrasonic resonance spectra and the second harmonic components are compared to ascertain the presence of crack-like flaws in the component.

Ultrasonic tomography for in-process measurements of temperature in a multi-phase medium

Abstract: A method and apparatus for the in-process measurement of internal particulate temperature utilizing ultrasonic tomography techniques to determine the speed of sound through a specimen material. Ultrasonic pulses are transmitted through a material, which can be a multi-phase material, over known flight paths and the ultrasonic pulse transit times through all sectors of the specimen are measured to determine the speed of sound. The speed of sound being a function of temperature, it is possible to establish the correlation between speed of sound and temperature, throughout a cross-section of the material, which correlation is programmed into a computer to provide for a continuous in-process measurement of temperature throughout the specimen.

Ultrasonic inspection and imaging instrument

Abstract: An ultrasonic inspection and imaging instrument is characterized by storing reduced image examples (images by means of reduced image display data obtained by scaling down picture display data) of an ultrasonic measurement picture beforehand, together with measurement conditions at the time the measurement picture is obtained prior to a scale-down imaging process When the measurement is started or the measurement conditions are otherwise changed, the measurement conditions are set as those obtained from the measurement picture prior to the scale-down processing with one of the reduced image examples thus selected as an index while a list of image examples is indicated on a display and read from a memory unit for ultrasonic measuring purposes When a reduced image example or what is similar to the example desired by an operator is selected, proper measurement conditions are automatically set in the ultrasonic inspection and imaging instrument When the operator wants to change or switch the measurement picture, moreover, he/she is able to make ultrasonic measurement on confirming what the subsequent image is like or what an image is desired to be selected by means of the reduced image example beforehand

Ultrasonic log grading

Abstract: A log harvesting system is disclosed in which the log is graded automatically in the field by ultrasonic testing of the log. Pulses of utlrasonic waves are transmitted into the log to detect internal defects within the log by measuring changes in the transient time of the ultrasonic wave pulses through at least a portion of the log. A computer is used to determine the grade of the log and produce a grade output signal from transient time data and signals related to the length and diameter of the log. The log is marked with a different colored paint to indicate its grade by an automatic marking device in response to the receipt of the grade output signal. Ultrasonic testing apparatus may be added to a tree harvesting head with a saw for felling the tree and cutting the log to the proper length and delimber knives for removing limbs, in order to test the log for defects as the log is conveyed through such head. In one embodiment, a pair of ultrasonic transducer wheels are mounted on opposite sides of the log and pairs of transmitting and receiving transducers are selectively coupled to the log through liquid coupling chambers provided on the outer surface of such wheels as the wheels rotate along the length of the log.

Through air transmission for ultrasonic nondestructive testing

Abstract: The theoretical design and experimental evaluation of a prototype through air ultrasonic inspection system are described. It is based around a ceramic-epoxy composite transducer configuration that is tailored specifically for through transmission scanning in air. A simulation model is used for the design of transmission and reception devices and the main factors influencing transduction performance are discussed with respect to the air and test specimen interface. Through transmission results are presented for inspection of solid test samples, including carbon-fiber composites plates, typical of those encountered in the aerospace industry. >

Ultrasonic spectroscopy of composite materials

Abstract: Composite materials are more and more used in high technology industries owing to their unique mechanical properties. For such heterogeneous and quasi-periodic materials, classical non-destructive evaluation (NDE) methods prove very unsatisfactory, and even often inapplicable. Our aim here is to investigate the particular case of ultrasonic NDE of fibre-reinforced composite materials. When using the classical A-scan echography method, it is difficult to interpret time diagrams. This is mainly due to the heterogeneous nature of the materials, the complexity of the diagrams being especially increased by the occurrence of distributed defects (like porosities). Using spectral analysis techniques (ultrasonic spectroscopy), information may be extracted from these intricate time diagrams, In particular, the occurrence of a selective absorption frequency in both the transmitted and reflected energy spectra is evident. This absorption phenomenon is clearly related to the material structure and periodicity and advantage may then be taken of its characteristics (centre frequency, bandwidth and relative depth of the absorption dip in the spectrum) to characterize the material and identify the presence of defects of porosities.

Nondestructive ultrasonic testing of materials

Abstract: Reflection waveforms obtained from aged and unaged material samples can be compared in order to indicate trends toward age-related flaws. Statistical comparison of a large number of data points from such waveforms can indicate changes in the microstructure of the material due to aging. The process is useful for predicting when flaws may occur in structural elements of high risk structures such as nuclear power plants, airplanes, and bridges.

One-sided ultrasonic inspection technique for the elastic constant determination of advanced anisotropic materials

Abstract: The subject of anisotropic elastic constant determination with a practical one-sided, multi-mode ultrasonic technique is presented along with comparisons with a more traditional cube cutting technique. Results are presented for destructive static compression tests as well. The Young's Moduli calculated from the measured ultrasonic velocity measurements are shown to compare favorably with those obtained from destructive static compression tests. Limitations of the one-sided method are discussed and further research efforts are also suggested.

Process and device for the ultrasonic testing of welds between plastics packaging and cover foils

Abstract: A process and an apparatus for the ultrasonic testing of welds between plastic packaging like food trays and cover foils. The welded joint between the tray and cover foil is periodically exposed to pulses of ultrasonic radiation. The pulses pass through the weld and are picked up or received by a receiver. The amplitude of the received pulses is evaluated. The cross-section of the beam of ultrasonic radiation is so small that the radiation only passes through the weld itself. The packages and the ultrasonic tester are moved relative to each other in order to examine the whole circuit of the weld. The pulse rate is such that the weld areas covered by successive pulses overlap.

Ultrasonic test device

Abstract: The invention is directed to a u/s test device for nondestructive testing of a workpiece moving relative thereto by the pulse echo method, having a fluid coupling between the ultrasonic oscillator and the surface of the work material. At least two test heads are provided whose sound beam axes intersect at a point in the region of the workpiece and a travel path in the form of a chamber is provided for guiding the fluid medium. To reduce susceptibility to interference and to achieve high test performance, a separately guided travel path extending along a determined length of the chamber and forming a duct (12-20) is associated with each test head (1-9), the axes of the travel path being aligned with the respective sound beam axis.

Ultrasonic unipolar pulse/echo instrument

Abstract: An ultrasonic unipolar pulse/echo instrument uses active switches and a timing and drive circuitry to control electrical energy to a transducer, the discharging of the transducer, and the opening of an electrical pathway to the receiving circuitry for the returning echoes. The active switches utilize MOSFET devices along with decoupling circuitry to insure the preservation of the unipolar nature of the pulses, insure fast transition times, and maintain broad band width and time resolution. A housing contains the various circuitry and switches and allows connection to a power supply and a movable ultrasonic transducer. The circuitry maintains low impedance input to the transducer during transmitting cycles, and high impedance between the transducer and the receiving circuit during receive cycles to maintain the unipolar pulse shape. A unipolar pulse is valuable for nondestructive evaluation, a prime use for the present instrument.

Mechanical characterization of a unidirectional composite by ultrasonic methods

Abstract: The anisotropy of fibrous composite materials makes it difficult to determine their elastic constants nondestructively. Quantitative ultrasonic methods were studied to determine elastic constants of a transversely isotropic laminate. Comprehensive relationships of the measured ultrasonic data and material properties were developed. The mode conversion phenomenon at the specimen–liquid interface with oblique incidence ultrasonic immersion testing provided all the necessary information. Determination of elastic constants was possible by measuring wave speeds and critical angles. Phase velocities were determined by the multiple reflection technique utilizing ultrasonic spectroscopy. A special scanning technique was developed to determine the phase velocities and wave propagation angles in the anisotropic plane from the measured group velocities. The method developed was applied to the characterization of a unidirectional graphite/epoxy composite.

Method of and an apparatus for the ultrasonic identification of materials and equipment

Abstract: A METHOD OF AND AN APPARATUS FOR THE ULTRASONIC IDENTIFICATION OF MATERIALS AND EQUIPMENT ABSTRACT A system of identifying materials and equipment consisting of small metal plates applied to them on their concealed surface and in which identifying means are provided consisting of incisions or blind holes which are detected under scanning or by multiplex technology using ultrasonic transducers which emit ultrasonic waves and which detect the ultrasonic signals reflected by the concealed surface, which set up a different binary coded sequence of return signals as a function of the markings made on the concealed surface of the small plate which is applied to the material.

Elastic characterization of orthotropic composite materials from ultrasonic inspection through non­ principal planes

Abstract: Transmission of bulk ultrasonic waves through materials immersed in water is a well appropriated method to measure the stiffness matrix of anisotropic composite materials. This matrix can be deduced from velocities measurements by simple [1,2,3] or double transmission [4,5] or from amplitudes of double reflected bulk waves [4]. All these methods are working very well for unidirectional composites when transverse isotropy is assumed and the stiffness matrix has only five independent elastic constants.

The influence of multiple scattering in incoherent ultrasonic inspection of coarse grain stainless steel

Abstract: Ultrasonic nondestructive testing (NDT) of cast stainless steel is known to be difficult due to a huge loss of focusing of the ultrasonic beam and to a high level of speckle noise generated by the coarse grain structure. It is shown that a multiple scattering process is generated by these materials. A method to characterize the incoherent component of the echographic signal is proposed. >

Capacitance devices for the controlled generation of ultrasonic fields in liquids

Abstract: Capacitance devices capable of efficiently radiating ultrasonic waves into liquids and air are described. Several designs have been characterized by examining the amplitude variations of the emerging beams, in both the near-field and far-field regions, and by determining their pulse responses using an interferometer. Although many aspects of their construction affect their bandwidth and beam profiles, the most influential appears to be the sizes and distribution of the air pockets trapped within the metallic backplate surface features. Techniques based upon conventional IC manufacturing could allow careful control over these backplate characteristics and hint at a new generation of water and air coupled standard ultrasonic transducers. >

Ultrasonic testing apparatus and method for rapidly inspecting a large number of gas cylinders of similar design for internal neck-shoulder defects

Abstract: The present invention provides an apparatus and method for ultrasonically testing the internal neck-shoulder region of a large number of gas cylinders for radially oriented defects. The apparatus and method includes housing an ultrasonic transducer within a shoe in a predetermined orientation wherein the transducer is wedged at a wedge angle so that ultrasonic pulses travel directly through the shoulder region to the top and bottom of the internal neck-shoulder region and is also outwardly skewed within the shoe at a skew angle such that the radially oriented defects reflect the ultrasonic pulses and produce return echoes. An automated scanner moves the shoe and therefore, the transducer in a predetermined pattern such that the entire internal neck-shoulder region of the gas cylinder is scanned. The scanner is supported by a stand that allows the automated scanner to be rapidly set up on the gas cylinders being tested. A processor activates the transducer to produce ultrasonic pulses, controls the automated scanner and responds to the return echoes for indicating the presence of the radial defects that require the removal of a particular one of the gas cylinders from service.

Ultrasonic testing to identify alkali-silica reaction in concrete

Abstract: This paper outlines a relatively small scale «pilot» programme to consider the feasibility and possible value of ultrasonic measurements for assessing and monitoring the condition of concrete in structures known to be affected by the problem or in which it is suspected

Probe and ultrasonic diagnosing apparatus using the same

Abstract: PURPOSE:To enable the measuring of the position and direction of an ultrasonic beam transmitted from or received to an object to be inspected by providing in the apparatus a means to detect a moving angle and a moving distance when a probe is moved along the surface of the object to be inspected by manual operation. CONSTITUTION:This apparatus is made up of an ultrasonic vibrator 12 which comprises a piezo-electric material to transmit an ultrasonic wave to or receive it from an object to be inspected, a sound absorbing material 13 which is provided on the rear side of the ultrasonic vibrator 12 to absorb an ultrasonic wave to be released on the rear side, an acoustic lens 14 which is provided on the front side of the ultrasonic vibrator 12 to focus an ultrasonic beam and an angle sensor 15 to detect a moving angle of the ultrasonic vibrator 12 with respect the surface of the object to be inspected and a distance sensor 16 to detect a moving distance of the ultrasonic vibrator 12 with respect to the surface of the object to be inspected. This enables the detecting of the moving angle and moving distance with a probe 10 itself.