EP0031049B1 - Akustischer Wandler - Google Patents

Akustischer Wandler Download PDF

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Publication number
EP0031049B1
EP0031049B1 EP80107438A EP80107438A EP0031049B1 EP 0031049 B1 EP0031049 B1 EP 0031049B1 EP 80107438 A EP80107438 A EP 80107438A EP 80107438 A EP80107438 A EP 80107438A EP 0031049 B1 EP0031049 B1 EP 0031049B1
Authority
EP
European Patent Office
Prior art keywords
acoustic transducer
sintered metal
transducer according
grain size
preliminary section
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80107438A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0031049A3 (en
EP0031049A2 (de
Inventor
Christian Göhlert
Peter Kanngiesser
Hansjakob Weiss
Werner Wilke
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Interatom T GmbH
Original Assignee
Interatom Internationale Atomreaktorbau GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Interatom Internationale Atomreaktorbau GmbH filed Critical Interatom Internationale Atomreaktorbau GmbH
Priority to AT80107438T priority Critical patent/ATE7429T1/de
Publication of EP0031049A2 publication Critical patent/EP0031049A2/de
Publication of EP0031049A3 publication Critical patent/EP0031049A3/de
Application granted granted Critical
Publication of EP0031049B1 publication Critical patent/EP0031049B1/de
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

Definitions

  • the present invention relates to an acoustic transducer for transmitting and receiving sound, in particular ultrasound signals, consisting of a piezoelectric element, a lead section and a damping body.
  • this acoustic transducer can be made entirely of metal and is therefore particularly suitable at high temperatures and / or with radioactive radiation.
  • These transducers can be used in opaque media such as liquid sodium, metallic materials tested or surfaces scanned without contact.
  • the so-called lead section protects the piezo-electric element from wear and tear or from contact with an aggressive medium and can change the direction of the sound if it is of the appropriate shape.
  • plastic wedges are used as the lead sections, which have a wave resistance suitable for this purpose.
  • the wave resistance of two adjacent media or bodies determines the reflection at the interface of these media and is in each case the product of the density and speed of sound of a medium.
  • a lead section should have a wave resistance that lies between that of the two adjacent media.
  • a leading section should have a wave resistance that represents the geometric mean between the wave resistances of the two adjacent media.
  • German laid-open specification DE-A-2 614 376 describes an ultrasonic transducer for high temperatures, for example for a nuclear reactor cooled with liquid metal.
  • the coupling wedge proposed there consists of a multiplicity of thin metal plates which are held together under pressure and which have an optically smooth surface towards the piezoelectric element.
  • a wedge made of numerous thin sheets of metal can only be produced with considerable effort and must be pressed together under considerable pressure so that the liquid metal does not creep through the gaps and attack the piezoelectric element.
  • such a wedge constructed from numerous thin sheets has the disadvantage that the transmission of the sound depends on the direction of these sheets.
  • a damping body which can consist of a loose wire mesh or a mixture of rubber and tungsten powder. But rubber is neither temperature nor radiation resistant and the wire mesh is not mechanically strong.
  • US-A-3 663 842 is a leading section for an ultrasound transducer, which consists of a plastic in which metal powders of different grain sizes are integrated in order to continuously change the wave resistance to match the medium to be examined.
  • the basic properties are determined by the plastic and are only changed by adding metal powder.
  • This lead section is also not resistant to high temperatures and radiation.
  • FR-A-2 097 451 a temperature- and radiation-resistant ultrasound transducer is known, which, however, has no lead section for coupling to another medium. From this document, however, it can be seen that as a damping body for damping echoes on the back of the piezoelectric element, a porous metallic body, e.g. made of sintered metal can be used.
  • the object of the present invention is an acoustic transducer which avoids the disadvantages mentioned and can be used at high temperatures and / or radioactive radiation and in aggressive media.
  • the ultrasonic transducer should have a temperature-resistant and radiation-resistant lead section, which brings about a favorable adaptation of the wave resistances and, if appropriate, also enables irradiation at a predetermined angle.
  • an acoustic Proposed converter according to the main claim.
  • a porous metallic body for example made of pressed metal powder or sintered metal, can be greatly influenced in its acoustic properties by suitable selection of the number and size of the grains or pores.
  • the speed of sound can be influenced, which is of great importance for the irradiation at certain angles.
  • the wave resistance can be kept in a favorable range between the wave resistances of the two adjacent media, which leads to good ultrasound transmission.
  • the total pore volume which can be set within wide limits in the production of a porous metallic body is decisive for the acoustic properties. It can be practically influenced by the grain size of the metal powder used and, for example, by appropriate pressing. If the pore dimensions are chosen to be smaller than the ultrasonic wavelengths, the sound attenuation caused by scattering in the porous body becomes small compared to the material-related sound attenuation. All of this means that, for most applications, good compromises regarding damping, speed of sound and wave resistance can be found reproducibly with a porous metallic body.
  • the sintered metal bodies proposed in the second claim as a leading section represent a particularly stable design. They can be produced from corrosion-resistant, heat-resistant material under high pressure and high temperature from metal powder of small grain size. Such lead sections made of sintered metal are not only resistant to temperature and radiation, but also have advantages over the known plastics at room temperature. They are not only more wear-resistant, but also less sensitive to minor damage to their surface. It has been found that the porous sintered metal surface can be coupled with the usual oil to a rough workpiece surface much more reliably than the smooth plastic surface.
  • Sintered metals also have further advantages at the temperatures that are still permissible for plastics, because their expansion coefficients correspond approximately to those of the piezoelectric elements and those of the workpieces to be tested, and therefore the reflection at interfaces is not changed significantly even with temperature fluctuations.
  • the wave resistance of the lead section has approximately the size of the geometric mean between the wave resistances of the adjacent media. This is the optimal design for a loss-free coupling of the ultrasonic transducer. It has been shown that this condition can be met simultaneously with a low speed of sound and with tolerable damping properties.
  • Claim 4 proposes a special embodiment of the invention, in particular for material testing.
  • a test in the material testing e.g. from DE-A-1 648 361 known arrangement with two wedge-shaped lead sections, each with two inclined sound passage surfaces for use at high temperatures and radiation exposure.
  • the wedge-shaped lead lines are made in different areas from sintered metal of different grain size, the space between the two sound passage surfaces each containing a lead section of sintered metal of small grain size and arranged near the other surfaces of sintered metal of larger grain size. This arrangement avoids disturbing reflections within the lead section on the surfaces which are not used for the passage of the sound.
  • sintered metal of different grain sizes the sound can be damped differently locally.
  • the sintered metal body has essentially a small grain size between the two sound passage surfaces, so that the sound is passed from one surface to the other with little attenuation. In the vicinity of the other surfaces, the sintered metal has a larger grain size and a correspondingly larger pore volume, so that the sound in this area is weakened more by higher absorption.
  • the acoustic transducer proposed in the fifth claim can be largely adapted to the adjacent materials or media on both sides.
  • a larger wave size of approx. 50 to 100 J tm enables a low wave resistance and on the side of the piezoelectric element a smaller size of approx. 20 J can be used tm set a higher wave resistance.
  • the reflections occurring at a boundary layer between two media are largely reduced and the performance of the converter is thus increased.
  • the transducer proposed in the sixth claim is initially to be mechanically damped in order to achieve the shortest possible transmission pulses, so that the piezoelectric element can not only emit or record as little loss as possible, ie without reflections, sound waves, or on the side facing the object to be examined, but also its damped back can absorb sound waves as far as possible and without reflections.
  • a material at this point whose wave resistance corresponds as closely as possible to that of the piezoelectric element.
  • damping body made of such a material would, however, have to have considerable dimensions in the direction of sound in order to achieve sufficient damping.
  • the greatest attenuation with the least reflection is achieved in a damping body in which the grain size of the sintered metal increases continuously in the direction from the piezoelectric element to the rear of the damping body. In practice, however, it appears sufficient to arrange two or three different grain sizes in one damping body.
  • porous metallic bodies with different seals proposed in the eighth, ninth and tenth claims are suitable for contact with such aggressive substances which are able to attack the piezoelectric element. It has been found that such a surface seal, in particular a sintered metal body, does not interfere with the desired acoustic properties.
  • a galvanic coating or the application of solder to the surface has proven to be unsuitable because in the one case the galvanic liquid in the other rall remains of solder in the free pores of the sintered metal and causes corrosion there.
  • a sintered metal made of stainless steel can be sealed by grinding with a diamond tool. The numerous small protrusions of the sintered metal are pressed into the adjacent depressions and cavities and seal them. Also by boriding, i.e. Coating with a boron-containing material, followed by a longer annealing at approx. 900 ° C, you can temper and seal machined steel surfaces with iron boride that occurs during structural transformation.
  • the lead section 1 made of a porous metallic body consists of two separate wedge halves 1 a and 1 b.
  • the angle a of the lead section is selected for the material test so that, depending on the sound velocities in the lead section of the wedge and in the material to be tested, the angle of incidence in the material has a fixed value that lies between 45 ° and 70 °.
  • Executed lead sections have wedge angles between 24 ° and 35 ° for longitudinal waves.
  • the surfaces set up to accommodate the piezoelectric transducers 2 are lapped optically smooth to less than 1 micron ripple.
  • the pressing device 3 made of stainless steel contains an adjustable pressure piece 4 for receiving disc springs 5 made of temperature-resistant material.
  • the contact pressure is 40 - 60 kp / cm 2 .
  • the pressing device 3 is fastened on the lead section 1 by a screw 6 and a bolt 7.
  • the pressure force of the disc springs 5 is transmitted to a metallic damping body 8 of high specific damping. Due to the mechanically stable damping body 8, the compressive force is transmitted uniformly to the piezoelectric element 2.
  • the contact surface of the damping body 8 is also machined by lapping to an accuracy of less than 1 micron.
  • FIG. 2 shows a cross section through the transducer according to the invention from FIG. 1. The inclination of both front wedge halves 1 a and 1 b can be seen in order to be able to focus the piezoelectric elements 2 for material testing.
  • the pressing device 3 for the defined application of the contact pressure contains a fine thread for receiving an adjusting screw 15.
  • the adjusting screw 15 has a conical bearing surface for the pressure piece 4, which applies the compressive force to the damping body 8 via the plate springs 5 and the disk 16 made of insulating material.
  • the pin 17 is also made of insulating material and is used to hold the damping body 8 during assembly.
  • the defined contact pressure is applied to the pressure piece 4 from the outside.
  • the set screw 15 is then tightened tight. Since the pressing device 3 has no inherent elasticity through suitable shaping, the force of the setter springs 5 can be applied to it support. There is a gap between the two wedge halves 1 a and 1 b, which prevents the sound waves from passing through.
  • FIG. 3 A possible embodiment of the fastening and mounting of the damping body is described with reference to FIG. 3, the transducer shown here not having a lead section. It consists of a housing 18, one side of which is designed as a sound membrane 19. The piezoelectric element 2 is applied to the inside of the sound membrane 19. In the same way, the damping body 20, which can be made of sintered metal, is connected to the back of the element 2. The connection technology is adapted to the respective operating temperatures.
  • the disc springs 5 prevent the damping body 20 from being detached from the element 2 in the event of vibrations occurring in an unfavorable manner.
  • the damping body 20 also serves as an electrical connecting element and is conductively connected to a temperature-resistant coaxial line 21.
  • a galvanic separation between the damping body 20 and the housing 18 is achieved via the ceramic insulating parts 22 and 23.
  • the housing 18 is sealed with the cover 24, which also serves as a counter bearing for the plate springs 5, which are centered by the bolt 25.
  • Fig. 4 shows a schematic representation of a wedge 1 as a leading section of an ultrasonic transducer according to claim 4.
  • the piezoelectric element 2 is applied on the top of the wedge.
  • the wave fronts emanating from element 2 spread out as straight waves in a wedge.
  • a metal powder of larger grain size for example grain size 200 to 300 microns, is arranged in the area B, which causes increased sound absorption.
  • the other areas of the wedge contain a homogeneous material with metal powder of, for example, 100 to 200 micron grain size with a constant and low sound attenuation. May g Rössen the transition surface between different grain at a defined angle to the surface B are applied. The transition from coarse-grained to fine-grained material through a mixing process during production is fluid, so that there is no sharply defined interface with disruptive reflection behavior.
  • the lead section 27 is formed in the area of the piezoelectric element 2 with a homogeneous layer C of smaller grain size, the area D consists of material of coarser grain size and the area E is in turn characterized by a layer of even larger grain size.
  • Fig. 6 shows a damping body 28 made of sintered metal of different grain size according to claim 6.
  • the grain size is selected so that an acoustic wave resistance is achieved that is as close as possible to that of the piezo material.
  • the grain size of the sintered metal is chosen so large that a sufficiently high damping is achieved and rear wall echoes from the surface H are no longer reflected to the piezoelectric element 2.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Surgical Instruments (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Electrophonic Musical Instruments (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
EP80107438A 1979-12-19 1980-11-27 Akustischer Wandler Expired EP0031049B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT80107438T ATE7429T1 (de) 1979-12-19 1980-11-27 Akustischer wandler.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2951075A DE2951075C2 (de) 1979-12-19 1979-12-19 Akustischer Wandler mit piezoelektrischem Element
DE2951075 1979-12-19

Publications (3)

Publication Number Publication Date
EP0031049A2 EP0031049A2 (de) 1981-07-01
EP0031049A3 EP0031049A3 (en) 1981-07-15
EP0031049B1 true EP0031049B1 (de) 1984-05-09

Family

ID=6088896

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80107438A Expired EP0031049B1 (de) 1979-12-19 1980-11-27 Akustischer Wandler

Country Status (5)

Country Link
US (1) US4430593A (ja)
EP (1) EP0031049B1 (ja)
JP (2) JPS5698651A (ja)
AT (1) ATE7429T1 (ja)
DE (2) DE2951075C2 (ja)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3219447A1 (de) * 1982-05-24 1983-11-24 Interatom Internationale Atomreaktorbau Gmbh, 5060 Bergisch Gladbach Koppelmedium zur akustischen ankopplung bei hohen temperaturen und verfahren zu seiner anwendung
US4556813A (en) * 1983-10-17 1985-12-03 Joseph Baumoel Cast metal sonic transducer housing
JPS6199860A (ja) * 1984-10-19 1986-05-17 Tokyo Keiki Co Ltd 超音波探触子
US4728844A (en) * 1985-03-23 1988-03-01 Cogent Limited Piezoelectric transducer and components therefor
SE455538B (sv) * 1985-12-06 1988-07-18 Tekniska Roentgencentralen Ab Ultraljudssond for provning av ett slitsat eller halforsett materialstycke
GB2225426B (en) * 1988-09-29 1993-05-26 Michael John Gill A transducer
ATE174445T1 (de) * 1992-09-28 1998-12-15 Siemens Ag Ultraschall-wandleranordnung mit einer akustischen anpassungsschicht
JP3926448B2 (ja) * 1997-12-01 2007-06-06 株式会社日立メディコ 超音波探触子及びこれを用いた超音波診断装置
AUPQ615000A0 (en) * 2000-03-09 2000-03-30 Tele-Ip Limited Acoustic sounding
US6788620B2 (en) * 2002-05-15 2004-09-07 Matsushita Electric Ind Co Ltd Acoustic matching member, ultrasound transducer, ultrasonic flowmeter and method for manufacturing the same
DE102006012114A1 (de) * 2006-03-14 2007-09-20 Endress + Hauser Flowtec Ag Vorrichtung zur Bestimmung und/oder Überwachung des Volumen- oder des Massedurchflusses eines Mediums in einer Rohrleitung
US20080195003A1 (en) * 2007-02-08 2008-08-14 Sliwa John W High intensity focused ultrasound transducer with acoustic lens
DE102007042663A1 (de) * 2007-09-10 2009-03-12 Krohne Ag Ultraschallsonde
US9078063B2 (en) 2012-08-10 2015-07-07 Knowles Electronics, Llc Microphone assembly with barrier to prevent contaminant infiltration
CN105101882B (zh) * 2013-03-29 2017-11-07 富士胶片株式会社 穿刺针用超声波探头以及使用它的超声波诊断装置
FR3016045B1 (fr) * 2014-01-02 2017-09-29 Aircelle Sa Dispositif et ensemble pour le controle non-destructif d’une piece composite, et procede de controle non-destructif d’une piece composite par ultrasons en transmission
GB2573305A (en) * 2018-05-01 2019-11-06 Tribosonics Ltd An ultrasonic transducer

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE533571A (ja) * 1954-10-27
US3325781A (en) * 1966-07-07 1967-06-13 Branson Instr Dual transducer probe for ultrasonic testing
FR2097451A5 (ja) * 1970-07-07 1972-03-03 Commissariat Energie Atomique
US3663842A (en) * 1970-09-14 1972-05-16 North American Rockwell Elastomeric graded acoustic impedance coupling device
US3989965A (en) * 1973-07-27 1976-11-02 Westinghouse Electric Corporation Acoustic transducer with damping means
US3973152A (en) * 1975-04-03 1976-08-03 The United States Of America As Represented By The United States Energy Research And Development Administration Ultrasonic transducer with laminated coupling wedge
JPS51140782A (en) * 1975-05-30 1976-12-03 Yokogawa Hewlett Packard Ltd Wide band ultrasonic senser and manufacturing method

Also Published As

Publication number Publication date
JPS5698651A (en) 1981-08-08
EP0031049A3 (en) 1981-07-15
DE2951075C2 (de) 1982-04-15
DE3067783D1 (en) 1984-06-14
DE2951075A1 (de) 1981-07-02
US4430593A (en) 1984-02-07
EP0031049A2 (de) 1981-07-01
JPH0167562U (ja) 1989-05-01
ATE7429T1 (de) 1984-05-15

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