CA1186735A - Instrument for testing materials - Google Patents
Instrument for testing materialsInfo
- Publication number
- CA1186735A CA1186735A CA000382873A CA382873A CA1186735A CA 1186735 A CA1186735 A CA 1186735A CA 000382873 A CA000382873 A CA 000382873A CA 382873 A CA382873 A CA 382873A CA 1186735 A CA1186735 A CA 1186735A
- Authority
- CA
- Canada
- Prior art keywords
- test piece
- pole shoe
- instrument according
- pole
- eddy current
- 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
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2412—Probes using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02854—Length, thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0421—Longitudinal waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves
Landscapes
- Physics & Mathematics (AREA)
- Biochemistry (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Electromagnetism (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
INSTRUMENT FOR TESTING MATERIALS
ABSTRACT OF THE DISCLOSURE
An instrument for testing of test pieces made of paramagnetic or diamagnetic material as well as of ferromagnetic materials above their Curie point for material defects and/or dimensional accuracy, especially for testing of tubes and slabs above 1000°C. The instrument comprises an electrodynamic instrument transformer having magnetic pole shoes and eddy current exciting and receiving windings; and an electronic signal processing unit. The pole shoes are designed in such a manner as to develop a magnetic field parallel to the test piece, and the eddy current exciting and receiving windings are heat-insulated with respect to the test piece.
ABSTRACT OF THE DISCLOSURE
An instrument for testing of test pieces made of paramagnetic or diamagnetic material as well as of ferromagnetic materials above their Curie point for material defects and/or dimensional accuracy, especially for testing of tubes and slabs above 1000°C. The instrument comprises an electrodynamic instrument transformer having magnetic pole shoes and eddy current exciting and receiving windings; and an electronic signal processing unit. The pole shoes are designed in such a manner as to develop a magnetic field parallel to the test piece, and the eddy current exciting and receiving windings are heat-insulated with respect to the test piece.
Description
35i ~STRUMENT FOR TESTING M~r~ERIALS
BACKGROUND OF THE INVENTION
... _ .
This invention provides an instr~ment for testing paramagnetic and diamagnetic metallic ma~erials~ as well as ~erromagnetic materials above their Curie points, for material defects and dim ~.sional accuracy~ It is particularly useful for testing tubes and slabs above 1000C. I'he instrument essentially comprises an electrodynamic instrument transformer having two magnetic pole shoes~ an eddy current exciting winding, a recei~ing winding, and an electronic signal processing unit for prccessing signals ~rom the receiving winding.
In the pursuit of quality control and optimum production efficiency, it is advantageous to test the quality of a product at an early stage of its manufac-ture so that~ in the event that a defect is detected9 correction ~an be made and product will not be wastedO For example, in the manufacture of seamless tubes, especially steel tubes, it is important to test tolerance accuracy while the tube is hot in order to detect erroneous settings of production line equipment while there is still surficient time to control the roll stands further down the line.
From literature on this subjectJ it is apparent that many different techniques are known for measuring hot test pieces. These known techniques can be c~assiied into ~ontacting measuring techniques and non-contactlng measuring techniques~
One such technique uses an ultrasonic pie~oelectr.ic oscillator with a high-pressure flow water coupling. At high pressure a stretch of water i5 generate~ between the test piece and the ult~asonic ~136~3~i oscillator. The test results achieved with such an arrangement are highly dependent upon khe surface quality of the test piece. The test procedure is relatively slow and requires a relativel~ large quantity of water~ Furthermore~ the coupling water causes local cooling of the test piece which can cause strains and cracks in the test pieceO
Another technique uses piezoelectric oscillators with pressure couplings. Such arrange-ments permit the direct coupling of the ossillator at high pressure within the range of a roll body~
However~ such arrangements limit the positioning of the measuring apparatus since measurements cannot be made at any desired point of the train of rollers~
Also, it is impossible to take a measurement for tolerance accuracy.
It is also known to excite u~trasonic pulses by using a high capacity pulse laser to locally heat the test piece. However, the use of this instrument for industrial testing is limited.
In addition to the ultrasonic arrangements, it is also known to test materials in prod~ction using radiological methods. These methods require working with X-raysl beta rays or gamma rays and therefore present problems of protection from the radiation.
Also~ radiological testing requires a relatively long measuring time to obtain the accuracy of measurement normally requiredO
Another known technique is the electrodynamic excitation of ultrasonics. This technique is based on the principle that a force is exerted on a current-carrying body in a magnetic field, acting vertically on the plane that is charged by the magnetic field vector and the current vector. A solenoid g~nerates the magnetic field via a pole shoe configuration while :l~B~35 an eddy current pulse is excited in the test piece using a transformer coil.
The intensity of the power pulse generated in such a manner and thus the force oE the ultrasonic pulse is a function of the magnitude of the eddy current and on the strength oE the magnetic field.
In order to be able to generate a sufficiently strong magnetic fielcl and a large eddy current to permit ultrasonic evalllation of the test piece, the electrodynamic transformer head must be positioned very close to the test piece. Depending upon the design of the transformer head itself, different types of ultrasonic waves can be generated. Known instruments have an operational disadvantage. Depending on its specific design, an electrodyn-amic transformer head is suitable only for generating transverse waves, guided waves or Lamb-waves, which at high temperatures in the test piece are strongly damped since the shearing module is highly decreasing and th~ls they cannot be exploited technically. In addition thereto, all of above-mentioned arrange-ments have the disadvantage that they are restricted to the use of ferritic materials or to such geometries of test pieces that fit between the pole shoes of the electrodynamic transformer. This means that the thickness of the test piece is limited to some millimeters.
The longitudinal wave transformers required for measurements taken on hot test pieces or such made of paramagnetic or diamagnetic metals are de-scribed, e.g., in the British Journal of Non-Destructive Testing, 20, 1978, No. 5, September, pages 242 to 247, in Material Evaluation, 34, 1976, No. 4, April,pages ~3-i735 81 to 90; and in Ultrasonics~ 16~ 1978~ No~ 7~ July~
pages 151 to 155~ HoweverJ these publications describe only transformers that are not suitable for use at high temperatures and within small distances of the test piece, as they permit only a maximum tes~
piece temperature of 1000Co SUMMARY OF THE INVENTI_ It is therefore the object of the present invention to provide an instrument for testing of paramagneti~ and diamagnetic metallic materials, as well as of ferromagnetic materials above their Curie points for material defects and dim ~ sional accuracy7 and especially for testing tubes and slabs above 1000C. The test instrument essentially comprises an electrodynamic instrument transformer having two magnetic pole shoes~ an edd~ current exciting winding, an eddy current receiving winding, and c~ electronic signal processing unit for processing signals from the eddy current receiving winding. The transformer according to the present invention overcomes the ma~or operational problems associated with prior art devices. Speciically, it generates longitudinal waves 7 it can be moved within 1 mm of the test piece, and is insensitive to high temperat~resO
~ primary feature of ~e transformer is that the pole shoes are designed so as to produce a magnetic field parallel to the test piece. As an additional featuret the eddy current exc.iting and receiving windings are heat-insulated on their respective sides facing the test piece~These windings~
on their respective sides facing the test piece, are embedded in a heat-insulating ceramic layer, and on ~heir respective sides facîng away from the test piece are embedded in a heat-conducting ceramic layer.
Thus, in accordance with a broad aspect of the invention, there is provided an instrument for testing a test piece made of paramagnetic or diamagnetic metallic material or a ferromagnetic material above its Curie pOillt for materi.al defects and/or dimensional accuracy, comprising:
an electrodynamic transducer for nondestructive testing of said test piece by means of ultrasonic energy said electrodynamic transducer having a face adapted to be brought into close proximity with the test piece and having 1~ first and second magnetic pole shoes for providing a magnetic field have sub-stantial components parallel to said test piece, a heat-insulated eddy current exciting winding and a heat-insulated eddy current receiving winding close ~o said face;
an electronic signal processing unit, coupled to the eddy current receiving winding of said transducer, for analyzing signals received therefrom a.nd generating data indicative thereof, and means for displaying said data in human readable form.
BRrEF DESCRrPT~ON OF T~IE DRAWINGS
:
The invention will be further described with reference to the following figures, wherein:
F~URE 1 is a schematic block diagram of the test instrument accord-ing -to the present inventlon;
PIGURE 2 is a more detailed schematic diagram of adapter member 4, shown in block diagram form in FIGURE l;
FIGURE 3 is a cross-sectional view of transformer 1 shown schematic-ally in FIGURE l;
FIGURE 4 is an expanded view of a portion of the transormer shown in FIGURE 3;
FIGURE 5 is a f~rther expanded view of a portion of the transformer 5a 3~ `
an eddy current exciting winding 5 and an eddy current receiving winding 3; and an electronic signal processing unit 23.
Eddy current exciting winding 5 and receiving winding 3 are made heat-resistant thereby permitting their placement within a mm of a hot test piece 2. To provide this heat resistance, there is provided a heat-insulating protective ceramic layer 6 Ishown in FIGURE 3) of, e.g., a thickness of approximately O.S
mmt preferably of aluminum oxide, on the side~ of windings 3 and 5 facing the test piece~ Even in the extreme case of a test piece temperature of 1300C, the temperature on the transformer will not exceed approximately 350C. The insulated wire, e~g., copper wire, used for the windings 3 and 5, can withstand a continuous heat load up to approximately ~OO~C. A
heat-conducting ceramic layer 7 i5 applied to that side of each winding facing the transformer ~facing away from hot test piece 2), to further cool the windings so that the continuous heat loading capacity will not be exceeded. Ceramic layer 7 provides heat conduction and preferably seals the gap to pole shoes 8 and 11 that is required by the expansiveness of heat--insulating ceramic layer 6~ In the preferred embodiment~ layer 7 is formed by a heat-conducting ceramic bonding agent. The surface of windings 3 and 5 facing the transformer is preferably additionally cooled by means of a cooling liquid flowing thrcugh a cooling liquid passage 24 tsee FIGURE 3).
In addition to the heat-insulation of the windings 3 and 5, the design of pole shoes 8 arld 11 is very important~ In order to be able to excite longitudinal waves in the test piece, one must generate a rather strong magnetic field 25 (shown in FI~U~E 5) parallel to the surface of the test piece~
~36'73~
Within the range of the eddy current.s only hori~ontal components are desired. Vertical components excite transverse waves which in hot test pieces do not propagate and cause disturbing echoes when cold para~agn2tic and diamagnetic materials are used.
Therefore, in order to obtain a field as shown in FIGURE 5~ it is especially preferably to make one pole shoe 8 (pole shoe 8) of conical designY The angle of conical surace 35 is determined by the wldth required for eddy current exciting winding 5 and eddy current receiving winding 3. In order to obtain a symmetric magnetic field independent of the distance bet~en transEormer 1 and test piece 2, it is desirable that the surface 9 of pole shoe 8 be positioned parallel to the test piece~ and be approximately of the same size as the corresponding surface 10 of the counter~pole shoe 11~ It is also desirable to incline the pole shoe 11 against the plane of the pole shoe surfaces 9 and lQ at an angle of at least 20.
The inclination of the edge surEace 12 of pole shoe 11 should preferably correspond to approxi-mately the angle of the conical surface 35 oE pole shoe 8. In order to prevent a substantial loss of field stren~th, the edge formed by the surface 13 (see FIGU~E 4) of pole shoe 11 and it edge surEace 1~ is broken 50 as to deEine an edge surface 34~ U~iny this designr it is possible to avoid an especiall.y powerfully developed magnetic field at this place that would otherwise be formed due to the point effect (by reducin~ the distance)~
Special importance must be attached to the construction and inclination of the pole shoes 8 and 11 for another reason. In order to avoid the eddy currents induced by the windings 3 and 5 in the pole shoes 8 and 11~ that could lead to ultrasonic pulses in the pole shoes that could return again and ~ ain to their places of origin by multiple reflection or appear as set noise in the receiver, it is preferable to choose the inclination angle of pole shoe ll in such a manner that these interfering impulses will flow outwardly along pole shoe 11. Pole shoe 8 is preferably ormed from sheets insulated toward each othern This also results in an expansion o the tolerance range for the distance between transformer 1 and test piece 2.
To protect pole shoes 8 and 11 frcm heat so that the pole shoe material will keep its functional properties below its Curie point, the pole shoes are cooled3 Pole shoe 11 pre~erably has a cooler 14 (see FIGURE 3) of non-ferritic material, through which a cooling agent flows. Pole shoe B~ on the other hand, is prov;ded with a cooling channel 26 (see ~GURE 3)~
passing a cooling agent also along heat-cond~cting ceramic layer 7 and magnetic field exciting winding 22, and in that manner providing for the cooling of these members. The cooling agent is pumped in a closed or open loop system by a pump ~7 (see FIGURE 1~ 1 through transformer 1.
Referring now specifically to FIGU~E 1, there is shown in schematic and block diagram orm the el~ctrical construction of the instrument according tG
the invention~ To generate the ultrasonic pulses, a transmitter 28 via an adapter means 29 supplies a signal to eddy current exciting winding 5~ E ~oes from test piece 2 are received via receiving winding 3. Through an active adapter means 4 the signals are coupled to a display amplifier 30 and then to .a display 31. The total operation is activated by a control 32. The magnetic field is controlled via a direct current source 33.
73~
Referring ncw specifically to FIGU~E 2 active adapter means 4 of el.ectronîc signal prccessing unit 23 preferably comprises an electronically controllab~l damping means 16, adapter means 17, a ~ransmit~r~eive switch 18, a 4and-pass filter 1~, a pre-amplifier 20 and a line driver 21~ Adapter means 17 comprises one or more matching capacitors*
The signals from receiving winding 3 are scanned by adapter means 17~ transferred via the pre-amplifier 20 and thereafter via a line driver 21 to a line~ which can be of any length in -~his configurationO To protect pre-amplifier 20 from overmodulating, there is provided a transmit-receive switch 18, essentially comprising an analog switch and di.verse protective diodes.
The electronically controllable damping means 16 located in the input circuit forms a resonant circuit winding 3 and adapter means 17. Transmission can be damped to such an extent that there will be no inadmissibly long dead time during which echoes cannot be received. If for tolerance reasons the distance between transformer 1 and test piece 2 is changed, this may require a variation of the damping of the oscillatory circuit resul~ing in a longer transmitting dead time and a broadening of the echo pulses. A
broadening of the echo pulses, however, would decrease resolution capacityO On the other hand, active adapter means 4 according to the invention provides an adequate damping of the tr~ smit and echo signals~
Th:is is realized by electronically controllable damping means 16 and band-pass filter 19.
The following non limitative exam?les represent typical embodiments of the instrument according to the invention~
.le 1 Test Pi~ e : Tube with a wall thickness of 40 mm Ma terial O Ferritic steel Temperature : 1200C
~easurement : Wall thickness Transmitter Length of pulse 1 s at 300 V on 12 ohms Trc~nsformer distance : 1 mm (tolerance -~0,5 mm) Transformer windings ~ Transmitter 20~ 0.1 mm copper wire Receiver 50~ O~OS r¢n copper wire Accuracy of measurement : +0.1 mm le 2 Test piece : Aluminum band with a thickness of ~0 n~
Temperature : Ambient temperature Measurement : Thickness of band Transmitt r o Pulse length 1 s at 300 V on 12 ohms Transformer distance : 0.85 r~ ~tolerance +0.3 mm) Transformer windings Transmitter 29, 0~1 mm copper enamelled wire Receiver 50, 0.05 mm copper enamelled wire Accuracy o~ measurement +0~05 mm The invention is not restricted to air as a working energy, and is also operating f-~lnder a heavy radial load, e.gO, in hot cells of nuclear plants.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment~ it is to be unlderstood that the invention is nfot to be limited to t'ne disclosed embodiments but on ~he contr~ryf, is intended to cover various modificatiolls and equfivalent arrangements included within the spirit and scope of ~ the appended claims which scope it to be accorded the f s broadest inte rpretation so as to encompass all such mf3difications and equivalent structures.
BACKGROUND OF THE INVENTION
... _ .
This invention provides an instr~ment for testing paramagnetic and diamagnetic metallic ma~erials~ as well as ~erromagnetic materials above their Curie points, for material defects and dim ~.sional accuracy~ It is particularly useful for testing tubes and slabs above 1000C. I'he instrument essentially comprises an electrodynamic instrument transformer having two magnetic pole shoes~ an eddy current exciting winding, a recei~ing winding, and an electronic signal processing unit for prccessing signals ~rom the receiving winding.
In the pursuit of quality control and optimum production efficiency, it is advantageous to test the quality of a product at an early stage of its manufac-ture so that~ in the event that a defect is detected9 correction ~an be made and product will not be wastedO For example, in the manufacture of seamless tubes, especially steel tubes, it is important to test tolerance accuracy while the tube is hot in order to detect erroneous settings of production line equipment while there is still surficient time to control the roll stands further down the line.
From literature on this subjectJ it is apparent that many different techniques are known for measuring hot test pieces. These known techniques can be c~assiied into ~ontacting measuring techniques and non-contactlng measuring techniques~
One such technique uses an ultrasonic pie~oelectr.ic oscillator with a high-pressure flow water coupling. At high pressure a stretch of water i5 generate~ between the test piece and the ult~asonic ~136~3~i oscillator. The test results achieved with such an arrangement are highly dependent upon khe surface quality of the test piece. The test procedure is relatively slow and requires a relativel~ large quantity of water~ Furthermore~ the coupling water causes local cooling of the test piece which can cause strains and cracks in the test pieceO
Another technique uses piezoelectric oscillators with pressure couplings. Such arrange-ments permit the direct coupling of the ossillator at high pressure within the range of a roll body~
However~ such arrangements limit the positioning of the measuring apparatus since measurements cannot be made at any desired point of the train of rollers~
Also, it is impossible to take a measurement for tolerance accuracy.
It is also known to excite u~trasonic pulses by using a high capacity pulse laser to locally heat the test piece. However, the use of this instrument for industrial testing is limited.
In addition to the ultrasonic arrangements, it is also known to test materials in prod~ction using radiological methods. These methods require working with X-raysl beta rays or gamma rays and therefore present problems of protection from the radiation.
Also~ radiological testing requires a relatively long measuring time to obtain the accuracy of measurement normally requiredO
Another known technique is the electrodynamic excitation of ultrasonics. This technique is based on the principle that a force is exerted on a current-carrying body in a magnetic field, acting vertically on the plane that is charged by the magnetic field vector and the current vector. A solenoid g~nerates the magnetic field via a pole shoe configuration while :l~B~35 an eddy current pulse is excited in the test piece using a transformer coil.
The intensity of the power pulse generated in such a manner and thus the force oE the ultrasonic pulse is a function of the magnitude of the eddy current and on the strength oE the magnetic field.
In order to be able to generate a sufficiently strong magnetic fielcl and a large eddy current to permit ultrasonic evalllation of the test piece, the electrodynamic transformer head must be positioned very close to the test piece. Depending upon the design of the transformer head itself, different types of ultrasonic waves can be generated. Known instruments have an operational disadvantage. Depending on its specific design, an electrodyn-amic transformer head is suitable only for generating transverse waves, guided waves or Lamb-waves, which at high temperatures in the test piece are strongly damped since the shearing module is highly decreasing and th~ls they cannot be exploited technically. In addition thereto, all of above-mentioned arrange-ments have the disadvantage that they are restricted to the use of ferritic materials or to such geometries of test pieces that fit between the pole shoes of the electrodynamic transformer. This means that the thickness of the test piece is limited to some millimeters.
The longitudinal wave transformers required for measurements taken on hot test pieces or such made of paramagnetic or diamagnetic metals are de-scribed, e.g., in the British Journal of Non-Destructive Testing, 20, 1978, No. 5, September, pages 242 to 247, in Material Evaluation, 34, 1976, No. 4, April,pages ~3-i735 81 to 90; and in Ultrasonics~ 16~ 1978~ No~ 7~ July~
pages 151 to 155~ HoweverJ these publications describe only transformers that are not suitable for use at high temperatures and within small distances of the test piece, as they permit only a maximum tes~
piece temperature of 1000Co SUMMARY OF THE INVENTI_ It is therefore the object of the present invention to provide an instrument for testing of paramagneti~ and diamagnetic metallic materials, as well as of ferromagnetic materials above their Curie points for material defects and dim ~ sional accuracy7 and especially for testing tubes and slabs above 1000C. The test instrument essentially comprises an electrodynamic instrument transformer having two magnetic pole shoes~ an edd~ current exciting winding, an eddy current receiving winding, and c~ electronic signal processing unit for processing signals from the eddy current receiving winding. The transformer according to the present invention overcomes the ma~or operational problems associated with prior art devices. Speciically, it generates longitudinal waves 7 it can be moved within 1 mm of the test piece, and is insensitive to high temperat~resO
~ primary feature of ~e transformer is that the pole shoes are designed so as to produce a magnetic field parallel to the test piece. As an additional featuret the eddy current exc.iting and receiving windings are heat-insulated on their respective sides facing the test piece~These windings~
on their respective sides facing the test piece, are embedded in a heat-insulating ceramic layer, and on ~heir respective sides facîng away from the test piece are embedded in a heat-conducting ceramic layer.
Thus, in accordance with a broad aspect of the invention, there is provided an instrument for testing a test piece made of paramagnetic or diamagnetic metallic material or a ferromagnetic material above its Curie pOillt for materi.al defects and/or dimensional accuracy, comprising:
an electrodynamic transducer for nondestructive testing of said test piece by means of ultrasonic energy said electrodynamic transducer having a face adapted to be brought into close proximity with the test piece and having 1~ first and second magnetic pole shoes for providing a magnetic field have sub-stantial components parallel to said test piece, a heat-insulated eddy current exciting winding and a heat-insulated eddy current receiving winding close ~o said face;
an electronic signal processing unit, coupled to the eddy current receiving winding of said transducer, for analyzing signals received therefrom a.nd generating data indicative thereof, and means for displaying said data in human readable form.
BRrEF DESCRrPT~ON OF T~IE DRAWINGS
:
The invention will be further described with reference to the following figures, wherein:
F~URE 1 is a schematic block diagram of the test instrument accord-ing -to the present inventlon;
PIGURE 2 is a more detailed schematic diagram of adapter member 4, shown in block diagram form in FIGURE l;
FIGURE 3 is a cross-sectional view of transformer 1 shown schematic-ally in FIGURE l;
FIGURE 4 is an expanded view of a portion of the transormer shown in FIGURE 3;
FIGURE 5 is a f~rther expanded view of a portion of the transformer 5a 3~ `
an eddy current exciting winding 5 and an eddy current receiving winding 3; and an electronic signal processing unit 23.
Eddy current exciting winding 5 and receiving winding 3 are made heat-resistant thereby permitting their placement within a mm of a hot test piece 2. To provide this heat resistance, there is provided a heat-insulating protective ceramic layer 6 Ishown in FIGURE 3) of, e.g., a thickness of approximately O.S
mmt preferably of aluminum oxide, on the side~ of windings 3 and 5 facing the test piece~ Even in the extreme case of a test piece temperature of 1300C, the temperature on the transformer will not exceed approximately 350C. The insulated wire, e~g., copper wire, used for the windings 3 and 5, can withstand a continuous heat load up to approximately ~OO~C. A
heat-conducting ceramic layer 7 i5 applied to that side of each winding facing the transformer ~facing away from hot test piece 2), to further cool the windings so that the continuous heat loading capacity will not be exceeded. Ceramic layer 7 provides heat conduction and preferably seals the gap to pole shoes 8 and 11 that is required by the expansiveness of heat--insulating ceramic layer 6~ In the preferred embodiment~ layer 7 is formed by a heat-conducting ceramic bonding agent. The surface of windings 3 and 5 facing the transformer is preferably additionally cooled by means of a cooling liquid flowing thrcugh a cooling liquid passage 24 tsee FIGURE 3).
In addition to the heat-insulation of the windings 3 and 5, the design of pole shoes 8 arld 11 is very important~ In order to be able to excite longitudinal waves in the test piece, one must generate a rather strong magnetic field 25 (shown in FI~U~E 5) parallel to the surface of the test piece~
~36'73~
Within the range of the eddy current.s only hori~ontal components are desired. Vertical components excite transverse waves which in hot test pieces do not propagate and cause disturbing echoes when cold para~agn2tic and diamagnetic materials are used.
Therefore, in order to obtain a field as shown in FIGURE 5~ it is especially preferably to make one pole shoe 8 (pole shoe 8) of conical designY The angle of conical surace 35 is determined by the wldth required for eddy current exciting winding 5 and eddy current receiving winding 3. In order to obtain a symmetric magnetic field independent of the distance bet~en transEormer 1 and test piece 2, it is desirable that the surface 9 of pole shoe 8 be positioned parallel to the test piece~ and be approximately of the same size as the corresponding surface 10 of the counter~pole shoe 11~ It is also desirable to incline the pole shoe 11 against the plane of the pole shoe surfaces 9 and lQ at an angle of at least 20.
The inclination of the edge surEace 12 of pole shoe 11 should preferably correspond to approxi-mately the angle of the conical surface 35 oE pole shoe 8. In order to prevent a substantial loss of field stren~th, the edge formed by the surface 13 (see FIGU~E 4) of pole shoe 11 and it edge surEace 1~ is broken 50 as to deEine an edge surface 34~ U~iny this designr it is possible to avoid an especiall.y powerfully developed magnetic field at this place that would otherwise be formed due to the point effect (by reducin~ the distance)~
Special importance must be attached to the construction and inclination of the pole shoes 8 and 11 for another reason. In order to avoid the eddy currents induced by the windings 3 and 5 in the pole shoes 8 and 11~ that could lead to ultrasonic pulses in the pole shoes that could return again and ~ ain to their places of origin by multiple reflection or appear as set noise in the receiver, it is preferable to choose the inclination angle of pole shoe ll in such a manner that these interfering impulses will flow outwardly along pole shoe 11. Pole shoe 8 is preferably ormed from sheets insulated toward each othern This also results in an expansion o the tolerance range for the distance between transformer 1 and test piece 2.
To protect pole shoes 8 and 11 frcm heat so that the pole shoe material will keep its functional properties below its Curie point, the pole shoes are cooled3 Pole shoe 11 pre~erably has a cooler 14 (see FIGURE 3) of non-ferritic material, through which a cooling agent flows. Pole shoe B~ on the other hand, is prov;ded with a cooling channel 26 (see ~GURE 3)~
passing a cooling agent also along heat-cond~cting ceramic layer 7 and magnetic field exciting winding 22, and in that manner providing for the cooling of these members. The cooling agent is pumped in a closed or open loop system by a pump ~7 (see FIGURE 1~ 1 through transformer 1.
Referring now specifically to FIGU~E 1, there is shown in schematic and block diagram orm the el~ctrical construction of the instrument according tG
the invention~ To generate the ultrasonic pulses, a transmitter 28 via an adapter means 29 supplies a signal to eddy current exciting winding 5~ E ~oes from test piece 2 are received via receiving winding 3. Through an active adapter means 4 the signals are coupled to a display amplifier 30 and then to .a display 31. The total operation is activated by a control 32. The magnetic field is controlled via a direct current source 33.
73~
Referring ncw specifically to FIGU~E 2 active adapter means 4 of el.ectronîc signal prccessing unit 23 preferably comprises an electronically controllab~l damping means 16, adapter means 17, a ~ransmit~r~eive switch 18, a 4and-pass filter 1~, a pre-amplifier 20 and a line driver 21~ Adapter means 17 comprises one or more matching capacitors*
The signals from receiving winding 3 are scanned by adapter means 17~ transferred via the pre-amplifier 20 and thereafter via a line driver 21 to a line~ which can be of any length in -~his configurationO To protect pre-amplifier 20 from overmodulating, there is provided a transmit-receive switch 18, essentially comprising an analog switch and di.verse protective diodes.
The electronically controllable damping means 16 located in the input circuit forms a resonant circuit winding 3 and adapter means 17. Transmission can be damped to such an extent that there will be no inadmissibly long dead time during which echoes cannot be received. If for tolerance reasons the distance between transformer 1 and test piece 2 is changed, this may require a variation of the damping of the oscillatory circuit resul~ing in a longer transmitting dead time and a broadening of the echo pulses. A
broadening of the echo pulses, however, would decrease resolution capacityO On the other hand, active adapter means 4 according to the invention provides an adequate damping of the tr~ smit and echo signals~
Th:is is realized by electronically controllable damping means 16 and band-pass filter 19.
The following non limitative exam?les represent typical embodiments of the instrument according to the invention~
.le 1 Test Pi~ e : Tube with a wall thickness of 40 mm Ma terial O Ferritic steel Temperature : 1200C
~easurement : Wall thickness Transmitter Length of pulse 1 s at 300 V on 12 ohms Trc~nsformer distance : 1 mm (tolerance -~0,5 mm) Transformer windings ~ Transmitter 20~ 0.1 mm copper wire Receiver 50~ O~OS r¢n copper wire Accuracy of measurement : +0.1 mm le 2 Test piece : Aluminum band with a thickness of ~0 n~
Temperature : Ambient temperature Measurement : Thickness of band Transmitt r o Pulse length 1 s at 300 V on 12 ohms Transformer distance : 0.85 r~ ~tolerance +0.3 mm) Transformer windings Transmitter 29, 0~1 mm copper enamelled wire Receiver 50, 0.05 mm copper enamelled wire Accuracy o~ measurement +0~05 mm The invention is not restricted to air as a working energy, and is also operating f-~lnder a heavy radial load, e.gO, in hot cells of nuclear plants.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment~ it is to be unlderstood that the invention is nfot to be limited to t'ne disclosed embodiments but on ~he contr~ryf, is intended to cover various modificatiolls and equfivalent arrangements included within the spirit and scope of ~ the appended claims which scope it to be accorded the f s broadest inte rpretation so as to encompass all such mf3difications and equivalent structures.
Claims (14)
- THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. An instrument for testing a test piece made of a paramagnetic or diamagnetic metallic material or a ferromagnetic material above its Curie point for material defects and/or dimensional accuracy, comprising:
an electrodynamic transducer for nondestructive testing of said test piece by means of ultrasonic energy said electrodynamic transducer having a face adapted to be brought into close proximity with the test piece and having first and second magnetic pole shoes for providing a magnetic field have substantial components parallel to said test piece, a heat-insulated eddy current exciting winding and a heat-insulated eddy current receiving winding close to said face;
an electronic signal processing unit, coupled to the eddy current receiving winding of said transducer, for analyzing signals received therefrom and generating data indicative thereof, and means for displaying said data in human readable form. - 2. An instrument according to claim l wherein said instrument is positioned with respect to said test piece and arranged such that said eddy current exciting and receiving windings each have a side facing said test piece and a side facing away from said test piece, their respective sides facing the test piece being embedded in a heat-insulating ceramic layer and their respective sides facing away from said test piece being embedded in a heat-conducting ceramic layer.
- 3. An instrument according to claim 2 wherein said heat-insulating ceramic layer is made of aluminum oxide and wherein said heat-conductive coating is made of a ceramic adhesive.
- 4. An instrument according to claim 1 wherein said first pole shoe is coniform.
- 5. An instrument according to claim 1 wherein said first pole shoe comprises sheets that are insulated from one another.
- 6. An instrument according to claim 1 wherein said first and second pole shoes include respective pole shoe surfaces facing said test piece and wherein said second pole shoe is inclined at an angle of at least 25° toward a plane defined by said pole shoe surfaces.
- 7. An instrument according to claim 6 wherein said first and second pole shoes include respective pole shoe surfaces and wherein said second pole shoe is inclined at an angle of at least 25°
toward a plane defined by said pole shoe surfaces. - 8. An instrument according to claim 6 wherein said pole shoe surfaces are substantially at the same level and have the same surface dimensions.
- 9. An instrument according to claim 7 wherein said pole shoe surfaces are substantially at the same level and have the same surface dimensions.
- 10. An instrument according to claim 4 wherein said second pole has an edge surface and wherein the conical inclination of said first pole is substantially equal to the inclination of said edge surface of said second pole.
- 11. An instrument according to claim 10 wherein said second pole shoe further includes a jacket surface and another edge surface.
- 12. An instrument according to claim 1 further including a cooler arranged at a lower face of said second pole shoe.
- 13. An instrument according to claim 1 further including a pole shoe support for said first pole shoe, said support including a cooling groove formed therein.
- 14. An instrument according to claim 1 wherein said electronic signal processing unit includes an active adaption means comprising:
damping means for damping a signal received from said eddy current receiving winding;
a capacitor for filtering said signal received from said eddy current receiving winding;
a filter for filtering said signal from said receiving winding;
a transmit/receive switch for selectively passing a signal from said filter;
a pre-amplifier for amplifying a signal passed by said switch; and a line driver for further amplifying a signal passed by said switch and amplified by said pre-amplifier.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3029036.9 | 1980-07-31 | ||
| DE19803029036 DE3029036A1 (en) | 1980-07-31 | 1980-07-31 | DEVICE FOR TESTING MATERIALS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1186735A true CA1186735A (en) | 1985-05-07 |
Family
ID=6108558
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382873A Expired CA1186735A (en) | 1980-07-31 | 1981-07-30 | Instrument for testing materials |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0045412A3 (en) |
| JP (1) | JPS5753654A (en) |
| CA (1) | CA1186735A (en) |
| DE (1) | DE3029036A1 (en) |
| ZA (1) | ZA814966B (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3123935C2 (en) * | 1981-06-16 | 1985-03-28 | Nukem Gmbh, 6450 Hanau | Electrodynamic converter |
| DE3401072C2 (en) * | 1984-01-13 | 1986-04-10 | Nukem Gmbh, 6450 Hanau | Electrodynamic transducer head |
| DE3414071C1 (en) * | 1984-04-13 | 1985-04-11 | Nukem Gmbh, 6450 Hanau | Electrodynamic converter |
| DE3448080A1 (en) * | 1984-04-13 | 1986-08-07 | Nukem Gmbh, 6450 Hanau | Electrodynamic transducer |
| DE3425386C1 (en) * | 1984-07-10 | 1985-11-14 | Nukem Gmbh, 6450 Hanau | Electrodynamic converter |
| IT1199159B (en) * | 1984-07-13 | 1988-12-30 | Centro Speriment Metallurg | PROBE FOR THE CONTROL OF SURFACE DEFECTS OF HIGH TEMPERATURE METAL BODIES |
| DE3502751A1 (en) * | 1985-01-28 | 1986-07-31 | Siemens AG, 1000 Berlin und 8000 München | SHOCK SHAFT PIPE WITH A LONG LIFETIME |
| FR2608765A1 (en) * | 1986-03-19 | 1988-06-24 | Unimetal Sa | Probe for detecting defects in metal profiled sections at high temperature using eddy currents |
| JPH02144856U (en) * | 1989-05-10 | 1990-12-07 | ||
| DE3935432A1 (en) * | 1989-10-20 | 1991-04-25 | Mannesmann Ag | Non-destructive tester for conductive workpieces - has electromagnet system movable over workpiece and cooling system |
| DE4130935A1 (en) * | 1991-09-13 | 1993-03-25 | Mannesmann Ag | METHOD AND DEVICE FOR TESTING FERROMAGNETIC WORKPIECES BY MEANS OF ULTRASONIC WAVES |
| DE102008028711B4 (en) * | 2007-10-15 | 2009-07-09 | V&M Deutschland Gmbh | Method and device for measuring the eccentricity of a hot-finished, seamless tube during manufacture |
| CN108008007A (en) * | 2017-12-26 | 2018-05-08 | 天津忠旺铝业有限公司 | Aluminium alloy cast ingot defect-detecting equipment and method of detection |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3141952A (en) * | 1961-02-01 | 1964-07-21 | United Aircraft Corp | Electronic seam follower |
| GB1425201A (en) * | 1973-06-19 | 1976-02-18 | British Steel Corp | Ultrasonic testing of articles |
| US3963980A (en) * | 1973-08-29 | 1976-06-15 | Jury Mikhailovich Shkarlet | Ultrasonic instrument for non-destructive testing of articles with current-conducting surface |
| DE2722475A1 (en) * | 1976-05-20 | 1977-12-08 | Atomenergi Ab | COIL ARRANGEMENT FOR ELECTROMAGNETIC MEASUREMENTS |
| DE2657957C2 (en) * | 1976-12-21 | 1986-01-02 | T.I. (Group Services) Ltd., Edgbaston, Birmingham | Device for ultrasonic testing of workpieces |
| LU76692A1 (en) * | 1977-02-02 | 1978-09-13 | ||
| GB2006433B (en) | 1977-10-20 | 1982-03-24 | Ti Group Services Ltd | Ultrasonic testing |
| SE445614B (en) * | 1978-11-07 | 1986-07-07 | Studsvik Energiteknik Ab | PROCEDURE AND DEVICE FOR TRANSMISSION AND RECEPTION OF ELECTROMAGNETIC ALTERNATED AND RECEIVED PULSES OF ULTRA SOUND, PRIOR TO THE UNDERGRADUATE TESTING OF ELECTRICALLY CONDUCTIVE MATERIALS |
-
1980
- 1980-07-31 DE DE19803029036 patent/DE3029036A1/en not_active Withdrawn
-
1981
- 1981-07-15 EP EP81105568A patent/EP0045412A3/en not_active Withdrawn
- 1981-07-21 ZA ZA814966A patent/ZA814966B/en unknown
- 1981-07-30 CA CA000382873A patent/CA1186735A/en not_active Expired
- 1981-07-31 JP JP56119387A patent/JPS5753654A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5753654A (en) | 1982-03-30 |
| EP0045412A2 (en) | 1982-02-10 |
| DE3029036A1 (en) | 1982-03-04 |
| ZA814966B (en) | 1982-07-28 |
| EP0045412A3 (en) | 1984-04-18 |
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