National Research Council of Canada

Other

Canadian Patents & Development Ltd.

Queen's University at Kingston

Canadian Patents and Development Limited - Societe Canadienne Des

Cheng-Kuei Jen

Jean F Bussiere

Makiko Kobayashi

Michael Sayer

Ahmad Safaai-Jazi

John J Jonas

Zhigang Sun

Gerald W Farnell

Guanghua Yi

Irina D Makarow

Chee Ang Loong

Jacques Tatibouet

Hao Wang

Bin Cao

Ky Thanh Nguyen

Philippe H Lequeu

Brigitte Bacroix

A piezoelectric film having a porosity between 20 and 40%, a thickness ranging from tens of microns to less than a few millimeters can be used to form an ultrasonic transducer UT for operation in elevated temperature ranges, that emit pulses having a high bandwidth. Such piezoelectric films exhibit greater flexibility allowing for conformation of the UT to a surface, and obviate the need for couplings or backings. Furthermore, a method of fabricating an UT having these advantages as well as better bonding between the piezoelectric film and electrodes involves controlling porosity within the piezoelectric film.

Porosity control in piezoelectric films

Ultrasonic apparatus and associated methods for the in-line monitoring of melting, mixing and chemical reaction processes of materials inside an enclosed chamber having rotating elements associated therewith are presented. The chamber may be heated and the rotating elements may be blades and/or screws. The chamber may be a heating barrel and the materials may be polymer and polymer composites pellets, metal pellets and chemical compounds. Ultrasonic sensors, which are preferably coupled to a wall of the chamber, may be high temperature ultrasonic transducers attached to the external surface of the chamber or ultrasonic buffer rods embedded into the chamber and coupled to cooled ultrasonic transducers. These sensors are operated in the reflection mode and are placed over the rotating elements. The number and locations of the sensors depend on applications. The synchronization of the transmission of the ultrasonic signals and the associated data acquisition with the position of the rotating element may be accomplished by using a high speed multiple-record data acquisition system. The ultrasonic speed and attenuation in the material being processed, or the traveling time in the material and the amplitude of the ultrasonic signals reflected by the rotating element, the ultrasonic reflection coefficient or the amplitude of the ultrasonic signals reflected at the chamber-material interface or the buffer rod probing end-material interface, and the ultrasonic signals scattered by the material within the chamber, can provide information on the melting, mixing and chemical reaction of the materials.

Ultrasonic apparatus and methods for the monitoring of melting, mixing and chemical reaction processes

Ultrasonic sensors and associated methods for on-line monitoring of material properties for die casting, molding and extrusion processes at elevated temperatures are disclosed. The sensors include the use of ultrasonic waveguides embedded in the processing machines and piezoelectric ultrasonic transducers. The sensors are operated in the reflection geometry in which one side access of the processing machines is required. The monitoring parameters are the flow front, gap development and temperature of the materials being processed and filled in the cavities of the die in casting processes and the mold in injection molding, and the temperature and viscosity of the molten polymers in the polymer extrusion machines. Piezoelectric ultrasonic transducers made of high Curie temperature materials, fabricated by sol-gel techniques and directly deposited on top of the ultrasonic waveguides or the external walls of the shot sleeve of the die caster, die of the die caster, mold of the injection molding machine or barrel of the extruder are also used.

Ultrasonic sensors for on-line monitoring of castings and molding

Acoustic buffer rods are useful in the nondestructive ultrasonic evaluation of materials. In order to reduce the occurrence of spurious signals in the reflected acoustic waves forming an acoustic 'image' of a sample, it is proposed to design buffer rods such that their radial acoustic velocity profile is graded, preferably having a parabolic shape. The lowest acoustic velocity of the buffer rod is in its center, i.e. at the longitudinal axis of the rod. This design is applicable to both uncladded buffer rods as well as to the core of cladded ones.

Acoustic waveguides having a varying velocity distribution with reduced

A flexural acoustic wave sensing method and efficient, simple, miniature and economical ultrasonic devices using thin rods are presented. The diameter of the thin rod is less than one acoustic wavelength. The lowest order flexural acoustic wave, F.sub.11 mode, propagating along such thin rods is used. The thin rod materials can be metals, glasses, ceramics, polymers and single crystals. Any external disturbance which can alter the propagation characteristics of F.sub.11 mode may be monitored by recording such variation. Fiber acoustic interferometers, which are built by jointing two thin rods, can offer high sensitivity. These devices are primarily used for sensors.

Thin rod flexural acoustic wave sensors

Optical fibers comprising a core region surrounding by a cladding region, and having a high stimulated backward Brillouin scattering threshold, P.sub.TH, for telecommunication transmission line application, or a low P.sub.TH for distributor sensor application are disclosed. By controlling the longitudinal and shear acoustic wave velocity profiles of an optical fiber such that V.sub.L,core &gt;1.03 V.sub.L,cladding and V.sub.S,core &gt;1.03 V.sub.S,cladding, where V.sub.L,core and V.sub.S,core are respectively the longitudinal and shear acoustic wave velocities of the core region, and V.sub.S,core and V.sub.S,cladding the longitudinal and shear acoustic wave velocities of the cladding region, the optical fiber will have a P.sub.TH higher than 20 milliwatts. For low P.sub.TH optical fibers, that is, with a P.sub.TH lower than 1 milliwatt, the longitudinal and shear acoustic wave velocity profiles of the fiber must be such that V.sub.L,core &lt;0.97 V.sub.L,cladding and V.sub.S,core &lt;0.97 V.sub.S,cladding. In both high and low P.sub.TH optical fibers, the refractive index of the core region is higher than that of the cladding region for optical wave guidance.

Optical fibers with preset stimulated backward Brillouin scattering

Efficient, simple, miniature and economical piezoelectric and ultrasonic devices employing optical fibers coated with lead-zirconate-titanate (PZT) thin piezoelectric and ferroelectric films are described. The PZT thin films are fabricated chemically by a sol-gel method. Optical fibers can be dipped into the PZT solution, and followed by an annealing and an electric poling process in order to achieve good piezoelectricity in the coated PZT films. This coating process can be devised as an on-line method and thus coating length can be larger than meters. Due to the long coating length, high piezoelectricity, miniature and flexible nature, devices using optical fibers may be used for medical, telecommunication and sensor applications.

Fiber-optic piezoelectric devices

A method of, and apparatus for, evaluating forming capabilities of metal plate by means of ultrasonic waves where the rolling direction and the density of the plate are known. The method comprises the steps of launching acoustic waves into the plate and detecting acoustic waves propagating in the plate to establish acoustic velocities in the plate along at least two different directions. Then the value of a certain plastic strain characteristic, like the average plastic strain ratio R or the planar strain ratio .DELTA.R, is determined from a previously established empirical relationship between the velocities and the value of the plastic strain ratio R(.alpha.).

Method of, and an apparatus for, evaluating forming capabilities of

A birefringent single-mode acoustic fiber for propagating linearly polarized shear acoustic waves while preserving linear polarization, comprises an elongated core region of a solid material in which acoustic waves can be propagated in two orthogonal shear mode components, and a cladding region enclosing all surfaces of the core region except end surfaces thereof, the cladding region being also of a solid material in which acoustic waves can be propagated in two orthogonal shear mode components. The core and cladding regions have different shear wave velocities with the shear wave velocity of the core region being lower than that of the cladding region, the core or cladding region being characterized by at least one birefringence causing factor selected from the group consisting of (a) noncircular geometry of the core region, (b) asymmetry of shear wave velocity distribution in the core region and (c) asymmetrical stress induced in the cladding region, whereby to strongly break degeneracy between the two orthogonal shear mode components and preserve linear polarization thereof throughout the fiber. The birefringent single-mode acoustic fiber according to the invention is particularly useful in acoustic fiber sensor systems for monitoring environmental changes in pressure, temperature, strain, stress, etc.

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Brossard, Canada

Cheng-Kuei Jen