Abstract: A system for inspecting a conduit for undesirable characteristics. A transducer system induces guided acoustic waves onto said conduit. The transducer system detects the undesirable characteristics of the conduit by receiving guided acoustic waves that contain information about the undesirable characteristics. The conduit has at least two sides and the transducer system utilizes flexural modes of propagation to provide inspection using access from only the one side of the conduit. Cracking is detected with pulse-echo testing using one transducer to both send and receive the guided acoustic waves. Thinning is detected in through-transmission testing where one transducer sends and another transducer receives the guided acoustic waves.

Abstract: Detecting a defect in the sample is accomplished by photoacousticly exciting acoustic longitudinal, surface Rayleigh, and shear waves at a first point on a near surface of a sample; photoacoustically detecting acoustic waves at a second point spaced from the excitation first point for intercepting shear waves reflected from the far surface of the sample at approximately the angle of maximum shear wave propagation; and detecting the energy level of the intercepted reflected shear waves representative of the flaw in the sample.

Abstract: A method and apparatus is shown for implementing magnetostrictive sensor techniques for the nondestructive evaluation of pipes or tubes. A magnetostrictive sensor generates guided waves in a pipe or tube, which waves travel therethrough in a direction parallel to the longitudinal axis of the pipe or tube. This is achieved by using a magnetized ferromagnetic strip being pressed circumferentially against the pipe or tube. The guided waves are generated in the strip and coupled to the pipe or tube and propagate along the length of said pipe or tube. For detection, the guided waves in said pipe or tube are coupled to the thin ferromagnetic strip and are detected by receiving MsS coils. Reflected guided waves may represent defects in the pipe or tube.

Abstract: The disclosed invention mounts transmitting and receiving electrical coils (52, 54) within channels or chambers (48, 50) formed by the notched ends of magnets (24, 28) closest to the metallic structure under test (40) where said magnets (24, 28) are arranged to form annular arrays (20, 22) of an electromagnetic acoustic transducer (EMAT) pair applicable in non-destructive testing. The detection of one or more electromagnetically-induced resonant frequencies at shifted locations indicates the presence of one or more flaws (58, 60) in the metallic structure under test (40). The novel recessed mounting of the coils provided by the channels or chambers (48, 50) substantially reduces the observed electrical cross-talk between coils (52, 54) over the prior art and reduces the likelihood of the coils (52, 54) making contact with the subject metallic structure under test (40) as it is in longitudinal motion relative to the coils (52, 54).

Abstract: A method and system for implementing magnetostrictive sensor techniques for the nondestructive evaluation of pipeline structures. The system consists of a magnetostrictive sensor instrument unit, a data storage unit, and a plurality of magnetostrictive sensor probes are positioned on an in-line inspection vehicle. The instrumentation unit includes electronics for transmitting excitation pulses to a transmitting magnetostrictive sensor probe as well as electronics for amplifying and conditioning the signals detected by a receiving magnetostrictive sensor probe. The magnetostrictive sensor probes include both plate magnetostrictive sensors and permanent magnets which provide a DC bias magnetic field necessary for magnetostrictive sensor operation. The transmitting and receiving probes are attached to the in-line inspection vehicle by way of mechanical arms on opposing sides of the vehicle.

Abstract: The invention relates to a method and device for simultaneously measuring multiple properties of a sample composed of multiple layers of films. The measurement features several steps. First, at least one source of excitation radiation irradiates the sample's surface to excite an acoustic mode. A probe source of radiation irradiates the acoustic mode and is diffracted off the surface of the sample to form a signal beam. A detector detects the acoustic mode to generate a signal beam, which is then analyzed to determine an acoustic frequency and an amplitude, a depth of modulation, or a decay constant. These properties are then further analyzed to determine of at least two properties (e.g., a thickness of two layers) of the sample.

Abstract: A method and apparatus is shown for implementing magnetostrictive sensor techniques for the nondestructive short term inspection or long term monitoring of a structure. A plurality of magnetostrictive sensors are arranged in parallel on the structure and includes (a) a thin ferromagnetic strip that has residual magnetization, (b) that is coupled to the structure with a couplant, and (c) a coil located adjacent the thin ferromagnetic strip. By a transmitting coil, guided waves are generated in a transmitting strip and coupled to the structure and propagate along the length of the structure. For detection, the reflected guided waves in the structure are coupled to a receiving strip and are detected by a receiving magnetostrictive coil. Reflected guided waves may represent defects in the structure.

Abstract: The method of the invention identifies damage to an in-service conductor associated with the delivery (transmission and distribution) of electric power. Electro-magnetic acoustic energy is generated in an in-service conductor associated with the delivery of electric power. Corresponding return electro-magnetic acoustic energy is then measured. Features are then extracted from the return electro-magnetic acoustic energy to characterize damage to the in-service conductor. The features may be extracted through a variety of signal processing techniques, such as wavelet signal processing. The extracted features may be classified using a neural network, fuzzy logic, or a combination of both.

Abstract: A nondestructive bond testing system is implemented using a pulse laser that sends a single or multiple pulse(s) of controlled magnitude and bombards an object of interest causing a thermoelastic excitation response. This excitation in turn induces an ultrasonic propagation along or through the surface material. By detecting, capturing and interpreting these thermoelastic propagation signatures, the attachment condition of the joining materials is determined. The technique is a significant improvement over traditional mechanical pull, shear or contact type techniques. The techniques are implemented in automated high speed inspection systems suitable for real time manufacturing application. Particular applications include evaluating material joining in microelectronics manufacture (such as ball bonds) and thin coating processes.

Abstract: A method and apparatus is shown for implementing magnetostrictive sensor techniques for the nondestructive evaluation of plate type structures such as walls, vessels, enclosures, and the like. The system includes magnetostrictive sensors specifically designed for application in conjunction with plate type structures or pipes that generate guided waves in the plates or pipes which travel therethrough in a direction parallel to the surface of the plate or pipe. Similarly structured sensors are positioned to detect the guided waves (both incident and reflected) and generate signals representative of the characteristics of the guided waves detected that are reflected from anomalies in the structure such as corrosion pits and cracks. The sensor structure is longitudinal in nature and generates a guided wave having a wavefront parallel to the longitudinal axis of the sensor, and which propagates in a direction perpendicular to the longitudinal axis of the sensor.

Abstract: An apparatus and method for measuring the thickness of a coating adhered to a substrate. An electromagnetic acoustic transducer is used to induce surface waves into the coating. The surface waves have a selected frequency and a fixed wavelength. Interpolation is used to determine the frequency of surface waves that propagate through the coating with the least attenuation. The phase velocity of the surface waves having this frequency is then calculated. The phase velocity is compared to known phase velocity/thickness tables to determine the thickness of the coating.

Abstract: A method is disclosed for evaluating the physical properties of a sample, for example, the grain size in a polycrystalline material. An ultrasound field is generated in a local region of the sample with a non-contact source, such as a pulsed laser, such that the generated ultrasound diffuses away from said local region. After waiting until the generated ultrasound field has reached a diffusion regime, the resulting ultrasound field is measured with a non-contact detector. Parameters are adjusted in a mathematical model describing the predicted behavior of the ultrasound field in the diffusion regime to fit the detected ultrasound field to the mathematical model. In this way, parameters dependent on the physical properties of the sample, such as the diffusion coefficient and absorption coefficient, can be derived. The grain size, for example, can be estimated from these parameters preferably by calibrating the diffusion coefficient to grain size.

Abstract: At least one parameter of at least one fluid in a pipe 12 is measured using a spatial array of acoustic pressure sensors 14,16,18 placed at predetermined axial locations x1,x2,x3 along the pipe 12. The pressure sensors 14,16,18 provide acoustic pressure signals P1(t), P2(t), P3(t) on lines 20,22,24 which are provided to signal processing logic 60 which determines the speed of sound amix of the fluid (or mixture) in the pipe 12 using acoustic spatial array signal processing techniques with the direction of propagation of the acoustic signals along the longitudinal axis of the pipe 12. Numerous spatial array processing techniques may be employed to determined the speed of sound amix. The speed of sound amix is provided to logic 48 which calculates the percent composition of the mixture, e.g., water fraction, or any other parameter of the mixture or fluid which is related to the sound speed amix. The logic 60 may also determine the Mach number Mx of the fluid.

Abstract: An improved photoacoustic vessel and method of photoacoustic analysis. The photoacoustic sample vessel comprises an acoustic detector, an acoustic couplant, and an acoustic coupler having a chamber for holding the acoustic couplant and a sample. The acoustic couplant is selected from the group consisting of liquid, solid, and combinations thereof. Passing electromagnetic energy through the sample generates an acoustic signal within the sample, whereby the acoustic signal propagates through the sample to and through the acoustic couplant to the acoustic detector.

Abstract: A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system includes a transducer, spaced from the medium to be inspected, for introducing to and sensing from the medium an acoustic signal that propagates in the medium at a predetermined frequency; and a detector, responsive to the sensed propagating acoustic signal, for detecting in the sensed acoustic signal the Doppler shifted frequency representative of a flaw in the medium.

Abstract: A method for measurement of stress in a specimen utilizing a motorized electromagnetic acoustic transducer (EMAT). Stress causes a rotation of the pure-mode polarization directions of SH-waves and a change in the phase of waves polarized along these certain directions. The method utilizes a rotating small-aperture EMAT, connected to a processor, to measure phase and amplitude data as a function of angle. The EMAT is placed on a workpiece at the location where the stress is to be measured. The acoustic birefringence B is determined from the normalized difference of these phases. From these data, an algorithm calculates values of B. and &phgr;. The workpiece is then stressed or its stress state is changed. The values are measured again at the same location. Stress is determined from the change in B and &phgr;.

Abstract: A method and apparatus is shown for implementing magnetostrictive sensor techniques for the nondestructive evaluation of plate type structures such as walls, vessels, enclosures, and the like. The system includes magnetostrictive sensors specifically designed for application in conjunction with plate type structures or pipes that generate guided waves in the plates or pipes which travel threrethrough in a direction parallel to the surface of the plate or pipe. Similarly structured sensors are positioned to detect the guided waves (both incident and reflected) and generate signals representative of the characteristics of the guided waves detected that are reflected from anomalies in the structure such as corrosion pits and cracks. The sensor structure is longitudinal in nature and generates a guided wave having a wavefront parallel to the longitudinal axis of the sensor, and which propagates in a direction perpendicular to the longitudinal axis of the sensor.

Abstract: A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system includes a transducer, spaced from the medium to be inspected, for introducing to and sensing from the medium an acoustic signal that propagates in the medium at a predetermined frequency; and a detector, responsive to the sensed propagating acoustic signal, for detecting in the sensed acoustic signal the Doppler shifted frequency representative of a flaw in the medium.

Abstract: An EMAT apparatus which non-destructively tests spot welds between two sheets of metal. The apparatus includes a first EMAT coil on one sheet that acts as a transmitter for generating and transmitting an acoustic wave signal toward the spot weld, and a second EMAT coil on the other sheet for receiving the acoustic wave signal and converting the received acoustic wave signal to an electronic signal having a waveform. Electronics and a PC are used to measure at least one parameter of the waveform which is indicative of a characteristic of the spot weld.

Abstract: An EMAT arrangement utilizes separate transmitter and receiver EMATs which may each be connected to a tuning capacitor by a stripline cable. An electrostatic shield may also be provided between the coils and the coils can be offset from each other by ½ the pitch distance of sections in the coil. This reduces the duration of main bang, thus making it possible for the EMAT arrangement to detect structures which are very close to the coils.

Abstract: The invention provides an apparatus and method for fill level monitoring in which the height of contents in a container (10) is monitored. The apparatus comprises an ultrasound reciever (30) and signal processing means (50-56) adapted to receive signals from the receiver, the arrangement being such that the signal processing means (50-56) identifies a first signal (32), in use, which is representative of a wavefront (26) transmitted through the contents of the container (10) independently of the height of the contents in the container (10), and a second signal (34) that is representative of a wavefront (24) that is reflected from the interface (22) between the surface of the contents in the container (10) and the environment above the contents, and in which the signal processing means (50-56) uses the difference in travel time for the two wavefronts (24, 26) to provide a measurement of the level of the contents in the container (10).

Abstract: A drive line vibration sensor includes an emitter, a receiver, and a controller. The emitter and receiver are mounted in a differential manner such that drive line vibrations cause the emitter to vibrate at a different frequency than the receiver. In operation the emitter transmits a signal to the receiver such that the differential movement of the transmitter relative to the receiver produces a variation in the signal received by the receiver which is identifiable by the controller. In another embodiment, the emitter pulses the signal such that the frequency of the vibration can be determined. A recording device is preferably in communication with the controller to record the variation in the signal to provide an inexpensive diagnostic and maintenance system which can record the overall operation of a drive line under actual operational conditions.

Abstract: A transmitting and receiving switch assembly for an electromagnetic acoustic transducer (EMAT) and a method for selectively switching an EMAT between transmit mode and receive mode both use a particular circuit. This circuit contains an EMAT coil coupled to a tuning capacitor, which allows the EMAT to be operated at a desired frequency when transmitting. A set of capacitors separates the EMAT coil from a set of diode strings (preferably containing at least one fast switching silicon diode), which are joined by a resistive connection. A transformer, which is center tapped at its primary winding, is coupled to the other end of the diode strings. Finally, a receiver input is connected to the transformer. In operation, the frequency of the EMAT is set by appropriately energizing and tuning the tuning capacitor. A voltage is then applied in the center tapped transformer and in the resistive link between the diode strings.

Abstract: A system and method for generating a desired acoustic frequency content in a laser-generated ultrasonic wave emitted from a target in response to a laser pulse. The method includes generating a generation laser pulse using a laser source. An optimal wavelength &lgr;0 for the generation laser pulse is determined using a computer. The optimal wavelength data is determined from material-specific, empirically calculated data stored in a storage device that is accessible to the computer. An optimal laser pulse is generated by shifting the generation laser pulse to the optimal wavelength &lgr;0. The optimal laser pulse is directed to the target to generate the laser-generated ultrasonic wave with the desired frequency content.

Abstract: An electromagnetic acoustic transducer for inducing and sensing vibrations in a cylindrical object and methods of using an electromagnetic acoustic transducer to determine resonant frequencies and physical properties of cylindrical objects. The electromagnetic acoustic transducers produce specific modes of vibration in cylindrical objects including axial shear vibrations, torsional vibrations, radial vibrations and plane strain vibrations. The methods of determining physical properties of a cylindrical objects include comparing sensed resonant frequencies of the cylindrical object to known relationships between resonant frequency and the physical properties of interest. The methods can be used to determine the temperature, dimensions, elastic constants, and damping coefficients of cylindrical objects, the magnitude of a load applied to a cylindrical object, or the texture or grain orientation of the material forming a cylindrical object.

Abstract: An EMAT testing device for nondestructively testing tubes for surface defects and displaying the results has a EMAT transmitter arranged collinear with a pair of EMAT receivers. The EMAT receivers each receive a pair of oppositely propagating circumferential acoustic surface waves from the transmitter at different times and the relative amplitudes of the received waves are compared to located defects adjacent the receivers in the tube.

Abstract: A method for inspecting welds uses a single EMAT tranducer operated in pulse-echo mode that sends and receives Rayleigh waves to detect defects in a weld between sheet plates of dissimilar thicknesses.

Abstract: A method for detecting the location of an edge, interface, seam or other structure of a workpiece uses one or two electromagnetic acoustic transducers (EMATs) to transmit an ultrasonic wave along the workpiece toward the edge and to receive a reflected wave. The velocity of the wave in the material is used in conjunction with the round trip time-of-flight (TOF) of the transmitted and reflected wave, to calculate the location of the edge. This is done by placing the transducer or transducers at known locations on the workpiece. A surface wave or 90 degree shear wave can be utilized and no contact is needed between the transducer and the surface of the workpiece. Rough and/or dirty surfaces and hostile environments can be accommodated while practicing the invention.

Abstract: An improved high temperature electromagnetic acoustic transducer (EMAT) for conducting inspections of materials with elevated temperatures, which has cooling means using gas cooling, such as air or nitrogen, for cooling the transducer RF coil, the onboard circuitry and magnets, while also providing for the easy removal of the coil and onboard circuitry. Prior art EMAT's are susceptible to failure since high temperatures reduces the signal quality of the electronics components, degrades the insulation of the RF coils, and permanent magnets can loose field strength.

Abstract: An EMAT arrangement utilizes separate transmitter and receiver EMATs which may each be connected to a tuning capacitor by a stripline cable. An electrostatic shield may also be provided between the coils and the coils can be offset from each other by 1/2 the pitch distance of sections in the coil. This reduces the duration of main bang, thus making it possible for the EMAT arrangement to detect structures which are very close to the coils.

Abstract: An electromagnetic acoustic transducer for inducing and sensing vibrations n a cylindrical object and methods of using an electromagnetic acoustic transducer to determine resonant frequencies and physical properties of cylindrical objects. The electromagnetic acoustic transducers produce specific modes of vibration in cylindrical objects including axial shear vibrations. The electromagnetic acoustic transducers are used to determine the temperature, dimensions, elastic constants, and damping coefficients of cylindrical objects, the magnitude of a load applied to a cylindrical object, or the texture or grain orientation of the material forming a cylindrical object.

Abstract: An electromagnetic acoustic transducer is provided which includes magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can accomplish evaluating the absolute value of ultrasonic attenuation.

Abstract: A method for non-destructively testing closely-spaced objects, such as header tube stubs for a furnace or boiler using electromagnetic acoustic transducers (EMATs) having meander coil sensors. The small size of the sensor combined with the need to move the sensor only a small fraction of the circumference of a tube to scan the entire circumference of the tube under test permits easy and accurate testing of an entire tube, even when the tube is one of a closely-spaced bundle.

Abstract: The present invention allows for the fabrication of an EMAT system that eliminates static charge impulse noise. The EMAT system includes an EMAT, wear layer, and magnet. If the wear layer is made slightly conductive, the static charges slowly bleed off rather than build up to cause impulse discharges. This semiconductive wear layer does not attenuate the EMAT signals by introducing any additional distance between the EMAT coil and the conductive piping or by introducing any conductive material between the EMAT coil and the conductive piping. In the preferred embodiment, a wear layer of UHMW (ultra high molecular weight) polyethylene with a surface resistivity of about 10,000 ohms per square is utilized. The conductive UHMW polyethylene still acts as a wear layer, but now also acts as a semi-conductive static-dissipative interface between the EMAT coil and the piping.

Abstract: The apparatus for ultrasonic tissue investigation comprises an ultrasonic transducer (1) adapted to emit pulsed emissions into tissue and means (2) to move the transducer to scan an area of tissue to be investigated. Signals reflected from interfaces between acoustically different tissue components are received and converted into a representation of the tissue, which may be visually displayed. The emissions of ultrasonic radiation are so pulsed that each pulse has a very rapid fall back period, enabling better discrimination. Interpretation of the images may be facilitated by use of such techniques as fractal analysis.

Abstract: Device for testing ferromagnetic materials, such as pipelines and the like, for faults, cracks, corrosion, etc. An one electromagnetic ultrasonic transducer includes at least one high frequency current coil and an arraay of permanent magnets which create a magnetic field for exciting and/or detecting ultrasonic waves in the wall of the ferromagnetic material. The ultrasonic transducer is located between the pole pieces of an additional magnet arrangement that produces a magnetic prefield in the material wall.

Abstract: The average wall thickness and the wall-thickness variation of a liquid-carrying pipe are determined. An elastic wave is generated and is measured after traveling a distance along the pipe. From the received wave, the average radius of the pipe, the average inside diameter of the pipe, and the inside diameter variation of the pipe are determined. From the average radius of the pipe and the average inside diameter of the pipe, the average wall thickness of the pipe is determined. From the variations in the average radius of the pipe and the inside diameter variation of the pipe, the wall-thickness variation of the pipe is determined. To determine the average inside diameter of the pipe, the invention relies upon the coupling between the elastic wave modes propagating in the wall of the pipe and the modes propagating in the liquid within the pipe.

Abstract: The test apparatus for nondestructive material testing using electrodynamically generated ultrasonic waves. A high-frequency coil assembly has an end face perpendicular to a surface of the workpiece and it is disposed between at least two magnets. Efficient generation and reception of ultrasonic waves is thereby assured.

Abstract: The invention features a method for detecting a subsurface defect in a thin film structure. The method includes: optically generating an acoustic wave in a first spatial region of the film; optically measuring a time-dependent reflection of the acoustic wave from subsurface features in the film to produce a time-dependent signal; and analyzing the signal to detect an existence of the defect. The optically measuring step can include measuring the diffraction of a probe beam from the reflected acoustic wave. The analyzing step can include comparing the measured signal to a reference signal for defect-free structure.

Abstract: A method for the production of ultrasound waves for nondestructive materials testing of a workpiece. The method includes providing at least one radio frequency coil disposed in an essentially uniform magnetic field. The at least one radio frequency coil has a longitudinal axis disposed parallel to a surface of a workpiece. The method also includes producing horizontally polarized transverse ultrasound waves in the workpiece due to an interaction of the magnetic field with eddy currents in the workpiece. The eddy currents are supplied by the at least one radio frequency coil. The invention also teaches a device for implementing the method.

Abstract: A non-contact apparatus for monitoring the contents of a container, especially but not exclusively for quality control monitoring purposes associated with high speed packaging processes, comprises a non-contact ultrasound generation member, adapted so as to generate an ultrasound signal within the container (1). A non-contact detection scheme is employed to enable the contents of the container to be monitored by analysing ultrasound signals that have propagated through or round the container (1) either transmitted through or reflected from the containers contents. In use, the apparatus may be adapted to provide information about container fill level (h) or the presence or absence of an insert (14) such as a head forming device by analysing the measured signal profiles generated by a ultrasound detection member (3).

Abstract: A detection and imaging system 10 is provided for locating defects in pipes using electromagnetic acoustical transducer (EMAT) sensors. The system includes an ultrasonic generator 22 (FIG. 2) configured to transmit a pulse signal to the EMAT transmitter 16 (FIG. 1). The transmitter 16, in turn, sends an ultrasonic wave through a pipe 13. The EMAT receiver 18 (FIG. 1) is configured to detect the transmitted ultrasonic signal 24 and receive a reflected ultrasonic signal that is reflected by a defect in the pipe. A processor is configured to generate a filter signal based upon the transmitted ultrasonic signal 24, to correlate the filter signal and the rejected ultrasonic signal to derive the location of the defect relative to the receiver, and to display the profile of the defect.

Abstract: An electromagnetic acoustic transducer for inducing and sensing vibrations in a cylindrical object and methods of using an electromagnetic acoustic transducer to determine resonant frequencies and physical properties of cylindrical objects. The electromagnetic acoustic transducers produce specific modes of vibration in cylindrical objects including axial shear vibrations, torsional vibrations, radial vibrations and plane strain vibrations. The methods of determining physical properties of a cylindrical objects include comparing sensed resonant frequencies of the cylindrical object to known relationships between resonant frequency and the physical properties of interest. The methods can be used to determine the temperature, dimensions, elastic constants, and damping coefficients of cylindrical objects, the magnitude of a load applied to a cylindrical object, or the texture or grain orientation of the material forming a cylindrical object.

Abstract: An acoustic monitor assembly for monitoring the particulate content of a liquid, comprising, a body having an electrically conductive portion, the body contacting a liquid whose content is to be monitored in use, a magnetic field generator for generating a magnetic field to which the electrically conductive portion of the body is exposed, the magnetic field generator being positioned such that magnetic particulates in the liquid are drawn on to said body, and a signal generator for inducing eddy currents which oscillate at an acoustic frequency in the electrically conductive portion of the body and in response to which the body is caused to vibrate, and a monitoring for observing the vibration condition of the body so as to provide an indication of the content of said particulates which are drawn onto the body in the liquid.

Abstract: A EMAT inspection system is utiliized on sheet metal prior to it being formed or rolled to identify surface defects and sub-surface defects such as pencil pipe inclusions by using ultrasonic Lamb waves with the results being displayed on a remote screen of a display and control system which also records the inspection results and controls the EMAT system.

Abstract: An ultrasonic inspection technique using a specially designed electromagnetic acoustic transducer (EMAT) launches and receives longitudinal ultrasonic waves into a thin metal wall or thin metal foil seal of a container, causing it to vibrate and launch ultrasonic compressional waves into liquid contained therein. The contents of plastic containers having a metal foil seal forming one wall are easily inspected. The EMAT establishes a magnetic field in the surface of the metal parallel to the surface. Radio frequency (RF) eddy currents are also induced by the EMAT in the surface of the metal. A Lorentz force is generated in the metal surface according the vector product of J, the current density, and H, the magnetic field, and the force generated by the interaction of the perpendicular components of the magnetic field H and the eddy currents J is directed normally to the surface of the metal.

Abstract: A force sensor including a cylindrical body having a central section and two distal sections wherein selected acoustic resonant modes are trapped in the central section and decays exponentially in the distal sections. An electromechanical acoustic transducer (EMAT) can be used to excite and detect the selected resonant modes in the central section. Force applied to the distal sections, including axial stress and torque, alter the resonant frequencies of the selected modes.

Abstract: A non-destructive, non-contact testing apparatus and method which generally includes an ultrasonic signal generator for inducing one or more ultrasonic signals in a material and an optical interferometer that includes a laser for illuminating a section of the material and for detecting beat frequencies resulting from reflected light from the material. Deformations in the material as a result of the ultrasonic signal cause the beat frequency to be shifted as a result of the Doppler effect. Such differences in the beat frequency are detected by the system and used as an indication of a characteristic of the material.

Abstract: An electromagnetic acoustic transducer for magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can evaluates the absolute value of ultrasonic attenuation.

Abstract: The subject invention is a method and apparatus for detecting a flaw in a metallic structure which utilizes a plurality of electromagnetic acoustic transducers located in close proximity to, but spaced from, the metallic structure. Each transducer includes a plurality of magnets located in a spaced apart arrangement. The magnets of one transducer are not aligned, thereby angularly displaced, with the magnets of a directly adjacent transducer. The position of the north and south poles of the magnets of each transducer alternate. The metallic structure is to be moved relative to those transducers. The detection of a resonant frequency at a shifted location indicates the presence of a flaw in the metallic structure the position of which is marked by a marking device.