CA1098172A - Needle type non-destructive metal inspection probe - Google Patents
Needle type non-destructive metal inspection probeInfo
- Publication number
- CA1098172A CA1098172A CA264,900A CA264900A CA1098172A CA 1098172 A CA1098172 A CA 1098172A CA 264900 A CA264900 A CA 264900A CA 1098172 A CA1098172 A CA 1098172A
- Authority
- CA
- Canada
- Prior art keywords
- tubular member
- inner tubular
- needle
- central
- hole
- 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
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
- G01B7/10—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a needle type non-destructive metal inspection probe comprising an outer tubular member having a central through hole of a larger diameter, an inner tubular member having a central through hole of a smaller diameter, each of the outer and inner tubular members respec-tively having a plain land portion at its rear end, a grooved land portion at its front end and an intermediate caved portion, said grooved land portions respectively having a plurality of grooves formed therein and arranged circumferencially and longi-tudinally therein, and an inspection needle core having a first conductor wound thereon and positioned within said central through hole formed in said inner tubular member, a first set of plural exciting needle cores respectively positioned in said grooves of said inner tubular member and having a second conduc-tor wound thereon, a second set of plural exciting needle cores respectively positioned in said longitudinal grooves of said outer tubular member and having another second conductor wound thereon, said first conductor being connectable to an AC power source to detect primarily wall thickness changes, said second conductors being connectable to a DC power source to induce eddy current in the material to be inspected and to magnetize it, and a cylindrical case containing said outer and inner tubular members.
The present invention provides a needle type non-destructive metal inspection probe comprising an outer tubular member having a central through hole of a larger diameter, an inner tubular member having a central through hole of a smaller diameter, each of the outer and inner tubular members respec-tively having a plain land portion at its rear end, a grooved land portion at its front end and an intermediate caved portion, said grooved land portions respectively having a plurality of grooves formed therein and arranged circumferencially and longi-tudinally therein, and an inspection needle core having a first conductor wound thereon and positioned within said central through hole formed in said inner tubular member, a first set of plural exciting needle cores respectively positioned in said grooves of said inner tubular member and having a second conduc-tor wound thereon, a second set of plural exciting needle cores respectively positioned in said longitudinal grooves of said outer tubular member and having another second conductor wound thereon, said first conductor being connectable to an AC power source to detect primarily wall thickness changes, said second conductors being connectable to a DC power source to induce eddy current in the material to be inspected and to magnetize it, and a cylindrical case containing said outer and inner tubular members.
Description
This invention relates generally to a non-destructive metal inspection apparatus and more particularly to a needle type non-destructive metal inspection probe adapted to be used in the inspect:ion apparatus for determining thickness of the material to be inspected.
Conventionally, there have been studied various kinds of non-destructive type metal inspection methods and apparatus for the same. These prior arts can be classified into a Roentgen or X-ray inspection method, an ultrasonic flaw detection method and a magnetic flaw detection method. Further the magnetic flaw detection method is divided into a magnetized power inspection method using magnetized iron powder to be sprayed on the metal and an eddy current inspection method inducing alternating current magnetic field in the metal. Especially, the eddy current type metallic flaw inspection apparatus of the prior art requires a strong and large-sized magnetizing apparatus, so that it is laborious and uneconomical to carry and handle the flaw inspec-tion apparatus and perform the inspection. Further, the material to be ir.spected by the eddy current type apparatus is limited to products made of non-magnetic material.
In case that the eddy current type metallic flaw inspec-tion method and the apparatus therefore and applied to a ferro-magnetic product such as a steel plate of a steel tube, stress-strain and magnetism diffusion is apt to be generated along the surface of the product, so that the material of the product must be fully magnetized in order to inspect the product effectively and precisely.
That is to say, in order to infiltrate alternating magnetic field into an inner portion of the ferromagnetic material to be inspected, it is necessary to fully magnetize a disturbed magnetic field in the material or effectively arrange in order the molecules in the material by passing a strong direct current ,~
.
.
magnetism through the material.
The present invention overcomes the above-mentioned problems involved in the conventional technique by providing a mechan:ism which is developed in order to effectively determine the th:ickness of the product.
According to the present invention there is provided a needle type non-destructive metal inspection probe comprising an outer tubular member having a central through hole of a larger diameter, an inner tubular member having a central through hole of a smaller diameter, each of the outer and inner tubular mem-bers respectively having a plain land portion at its rear end, a grooved land portion at its front end and an intermediate caved portion, said grooved land portions respectively having a plura-lity of grooves formed therein and arranged circumferencially and longitudinally therein, and an inspection needle core having a first conductor wound thereon and positioned within said central through hole formed in said inner tubular member, a first set of plural exciting needle cores respectively positioned in said grooves of said inner tubular member and having a second conduc-tor wound thereon, a second set of plural exciting needle coresrespectively positioned in said longitudinal grooves of said outer tubular member and having another second conductor wound thereon, said first conductor being connectable to an AC power source to detect primarily wall thickness changes, said second conductors being connectable to a DC power source to induce eddy current in the material to be inspected and to magnetize it, and a cylindrical case containing said outer and inner tubular members.
The probe of the present invention is called absolute type and employed primarily to determine the thickness of steel plate and wall of steel pipe.
It will be apparent from the foregoing description that when the metal inspection apparatus according to the present ::. ` ,.
~9~172 invention is used, high voltage source and a large-scale electric apparatus are not required and an infiltration degree of the flux emitted from these needle cores is large, so that even if the inspection probe of inspection apparatus is separated consider-ably away from the product to be inspected, the purpose for inspecting the product can be completely accomplished. Conse-quently, even though this product is heated at high temperature in order to arrange in order the disturbed magnetic field of the inside of the material, such phenomena do not happen that the inspection apparatus is subjected to a damage due to high temper-ature and operators suffer from burns.
As apparent from the above description, the present invention provides a mechanism much more excellent in effective-ness than the conventional eddy current metallic flaw detector, so that it seems that the present invention exceedingly contri-butes to the industrial fields.
The present invention thus provides a needle type non-destructive metal inspection probe having a very simple structure and an excellent operational effect.
The present invention also provides a non-destructive metal inspection probe easy in carrying and adapted to function efficiently and effectively especially to an iron plate or a pipe of metal such as ferromagnetic materials.
The present invention still further provides a metal inspection probe adapted to infiltrate a flux focusingly into an internal portion of a metal product to be inspçcted by using needles around which coils are wound.
The present invention also provides a very economic and convenient metal inspection probe adapted to be used in a duel-typed output indication apparatus of simple in construction and small in size.
The present invention further provides a most effective thickness determination probe by providing one inspection needle and at least one set of plural needle cores arranged around the inspection core.
The present invention will be further described by way of the accompanying drawings in which:
Fig. 1 is a longitudinally sectional view showing one embodiment of a needle type non-destructive metal inspection probe, adapted to determine the thickness of metallic products.
Fig. 2 is a cross sectional view of the probe shown in Fig. 1.
Fig. 3 is an exploded perspective view of the embodiment.
Fig. 4 shows a chart of wall thickness change indica-tion obtained by the embodiment of the absolute type metal inspec-tion probe.
Fig. 5 is a block diagram of electric circuit of dual-typed output indication apparatus to which the absolute type metal inspection probe is operatively connected.
Referring to Figs. 1 to 3 showing embodiment of the present invention, an absolute type wall thickness determination probe of a needle type non-destructive metal inspection probe, as shown in Figs. 1 and 2, contains an outer tubular member 1, and inner member 2 inserted into the outer tubular member 1. On a center portion of the inner member, a through-hole 9 is opened through which an inspection or detecting needle core has a wind-ing wire around the needle and connected to an AC power source of so small as 0.003 volt.
In the first embodiment of the absolute type wall thickness determination probe, the exciting system for exciting and magnetizing the material of product to be inspected in order to arrange in order the magnetic domains therein consists of an inner tubular member and an outer tubular member respectively having a set of exciting needle cores buried therein. As appar-ently shown in Fig. 3, tubular member 2 has a plain land portionat its rear end, a grooved land portion at its front end, and an intermediate caved portion formed between them. The front land portion has a number of grooves formed therein so as to extend longitudinally on the land portion from a side to another side. A primary set of exciting needle core are so placed on the bottom of grooves as to extend longitudinally along the length of the front land portion. The length of the exciting needle core respectively are determined so as to contact its base or thick end with the front side of the rear plain land portion and to place its pointed end at the front side of the grooved land portion.
In order to securely hold the primary set of plural exciting needle within the respective groove and on the bottom of intermediate caved portion, a second conductor is wound around the set of needle so as to contact with outer sides of the needles from a front side of the plain land portion to a rear side of the grooved land portion. The wound number of the conductor is so determined as to effectively function the absolute type probe.
Genérally speaking, there is no difference between the inner tubular member 2 and the outer tubular member 1 in shape, in construction and consequently in function, except for the size. Another second conductor is wound around the set of exciting needles respectively positioned in the grooves of the outer tubular member 1. The second conductors each applied to the intermediate caved portions respectively formed in the inner and outer tubular members 1 and 2 are electrically connected to a DC power source of about 0.003 V. As clearly understood from the drawings of FIGS. 1-3, the inner tubular member 2 is adapted to be inserted into the central through-hole of the outer tubular member 1. The outer diameter of the inner tubular member 2 corresponds to the inner diameter of the outer tubular member 1 and consequently the former is closely fitted into the latter.
The length of the inner tubular member is the same as that of the outer tubular member, and, in assembling, the front edges of both the tubular members are almost matched or levelled to each other.
According to the present invention, the absolute type metal inspection probes are effectively and conveniently operated when it is electrically connected, to the dual-typed output indi-cation apparatus having an electric circuit shown in Fig. 5. As apparently shown in Fig. 5, the absolute type probe is electri-cally changed over by an A - D switch and other electric parts such as a balancer, a tuning amplifier, a modulator are used as a common function parts of both the probes. The DC stabilizer is connected to the parts necessary to be electrically stabilized.
The duel-typed output indication apparatus is manufactured by assembling various conventional electric parts.
The resulting data of changing of wall thickness of metallic material is shown in the osciloscope installed in the indication apparatus. The data is recorded in a pen-writing oscilograph recorder in a form of curved line graph of Fig. 4.
Also, the resulting data can be indicated in a digital display device. The oscilograph recorder and the digital display device are driven by a Da amplifier connected to them.
According to the present invention, the needle type ~non-destructive metal inspection probe has generally a standard frequency range including 4 hz and 16 hz. The proper frequency is selected according to the material to be inspected and the wall thickness.
The inspection probe employs a very thin needle as detection cores and exciting cores. Consequently, a small and low-power source is sufficient to effectively operate the detec-tion cores and the exciting cores and, by reason of small and lower electric power and employment of thin needles used for this ~9~
needle cores, the magnetic flux penetrates in depth.
In the preferred embodiments, the respective needle has a diameter of about 0.25 mm, a length of about 40 mm and a pointed end. The whole weight of the probe is only about 100 g.
~ 7 -,. ~.
, :
Conventionally, there have been studied various kinds of non-destructive type metal inspection methods and apparatus for the same. These prior arts can be classified into a Roentgen or X-ray inspection method, an ultrasonic flaw detection method and a magnetic flaw detection method. Further the magnetic flaw detection method is divided into a magnetized power inspection method using magnetized iron powder to be sprayed on the metal and an eddy current inspection method inducing alternating current magnetic field in the metal. Especially, the eddy current type metallic flaw inspection apparatus of the prior art requires a strong and large-sized magnetizing apparatus, so that it is laborious and uneconomical to carry and handle the flaw inspec-tion apparatus and perform the inspection. Further, the material to be ir.spected by the eddy current type apparatus is limited to products made of non-magnetic material.
In case that the eddy current type metallic flaw inspec-tion method and the apparatus therefore and applied to a ferro-magnetic product such as a steel plate of a steel tube, stress-strain and magnetism diffusion is apt to be generated along the surface of the product, so that the material of the product must be fully magnetized in order to inspect the product effectively and precisely.
That is to say, in order to infiltrate alternating magnetic field into an inner portion of the ferromagnetic material to be inspected, it is necessary to fully magnetize a disturbed magnetic field in the material or effectively arrange in order the molecules in the material by passing a strong direct current ,~
.
.
magnetism through the material.
The present invention overcomes the above-mentioned problems involved in the conventional technique by providing a mechan:ism which is developed in order to effectively determine the th:ickness of the product.
According to the present invention there is provided a needle type non-destructive metal inspection probe comprising an outer tubular member having a central through hole of a larger diameter, an inner tubular member having a central through hole of a smaller diameter, each of the outer and inner tubular mem-bers respectively having a plain land portion at its rear end, a grooved land portion at its front end and an intermediate caved portion, said grooved land portions respectively having a plura-lity of grooves formed therein and arranged circumferencially and longitudinally therein, and an inspection needle core having a first conductor wound thereon and positioned within said central through hole formed in said inner tubular member, a first set of plural exciting needle cores respectively positioned in said grooves of said inner tubular member and having a second conduc-tor wound thereon, a second set of plural exciting needle coresrespectively positioned in said longitudinal grooves of said outer tubular member and having another second conductor wound thereon, said first conductor being connectable to an AC power source to detect primarily wall thickness changes, said second conductors being connectable to a DC power source to induce eddy current in the material to be inspected and to magnetize it, and a cylindrical case containing said outer and inner tubular members.
The probe of the present invention is called absolute type and employed primarily to determine the thickness of steel plate and wall of steel pipe.
It will be apparent from the foregoing description that when the metal inspection apparatus according to the present ::. ` ,.
~9~172 invention is used, high voltage source and a large-scale electric apparatus are not required and an infiltration degree of the flux emitted from these needle cores is large, so that even if the inspection probe of inspection apparatus is separated consider-ably away from the product to be inspected, the purpose for inspecting the product can be completely accomplished. Conse-quently, even though this product is heated at high temperature in order to arrange in order the disturbed magnetic field of the inside of the material, such phenomena do not happen that the inspection apparatus is subjected to a damage due to high temper-ature and operators suffer from burns.
As apparent from the above description, the present invention provides a mechanism much more excellent in effective-ness than the conventional eddy current metallic flaw detector, so that it seems that the present invention exceedingly contri-butes to the industrial fields.
The present invention thus provides a needle type non-destructive metal inspection probe having a very simple structure and an excellent operational effect.
The present invention also provides a non-destructive metal inspection probe easy in carrying and adapted to function efficiently and effectively especially to an iron plate or a pipe of metal such as ferromagnetic materials.
The present invention still further provides a metal inspection probe adapted to infiltrate a flux focusingly into an internal portion of a metal product to be inspçcted by using needles around which coils are wound.
The present invention also provides a very economic and convenient metal inspection probe adapted to be used in a duel-typed output indication apparatus of simple in construction and small in size.
The present invention further provides a most effective thickness determination probe by providing one inspection needle and at least one set of plural needle cores arranged around the inspection core.
The present invention will be further described by way of the accompanying drawings in which:
Fig. 1 is a longitudinally sectional view showing one embodiment of a needle type non-destructive metal inspection probe, adapted to determine the thickness of metallic products.
Fig. 2 is a cross sectional view of the probe shown in Fig. 1.
Fig. 3 is an exploded perspective view of the embodiment.
Fig. 4 shows a chart of wall thickness change indica-tion obtained by the embodiment of the absolute type metal inspec-tion probe.
Fig. 5 is a block diagram of electric circuit of dual-typed output indication apparatus to which the absolute type metal inspection probe is operatively connected.
Referring to Figs. 1 to 3 showing embodiment of the present invention, an absolute type wall thickness determination probe of a needle type non-destructive metal inspection probe, as shown in Figs. 1 and 2, contains an outer tubular member 1, and inner member 2 inserted into the outer tubular member 1. On a center portion of the inner member, a through-hole 9 is opened through which an inspection or detecting needle core has a wind-ing wire around the needle and connected to an AC power source of so small as 0.003 volt.
In the first embodiment of the absolute type wall thickness determination probe, the exciting system for exciting and magnetizing the material of product to be inspected in order to arrange in order the magnetic domains therein consists of an inner tubular member and an outer tubular member respectively having a set of exciting needle cores buried therein. As appar-ently shown in Fig. 3, tubular member 2 has a plain land portionat its rear end, a grooved land portion at its front end, and an intermediate caved portion formed between them. The front land portion has a number of grooves formed therein so as to extend longitudinally on the land portion from a side to another side. A primary set of exciting needle core are so placed on the bottom of grooves as to extend longitudinally along the length of the front land portion. The length of the exciting needle core respectively are determined so as to contact its base or thick end with the front side of the rear plain land portion and to place its pointed end at the front side of the grooved land portion.
In order to securely hold the primary set of plural exciting needle within the respective groove and on the bottom of intermediate caved portion, a second conductor is wound around the set of needle so as to contact with outer sides of the needles from a front side of the plain land portion to a rear side of the grooved land portion. The wound number of the conductor is so determined as to effectively function the absolute type probe.
Genérally speaking, there is no difference between the inner tubular member 2 and the outer tubular member 1 in shape, in construction and consequently in function, except for the size. Another second conductor is wound around the set of exciting needles respectively positioned in the grooves of the outer tubular member 1. The second conductors each applied to the intermediate caved portions respectively formed in the inner and outer tubular members 1 and 2 are electrically connected to a DC power source of about 0.003 V. As clearly understood from the drawings of FIGS. 1-3, the inner tubular member 2 is adapted to be inserted into the central through-hole of the outer tubular member 1. The outer diameter of the inner tubular member 2 corresponds to the inner diameter of the outer tubular member 1 and consequently the former is closely fitted into the latter.
The length of the inner tubular member is the same as that of the outer tubular member, and, in assembling, the front edges of both the tubular members are almost matched or levelled to each other.
According to the present invention, the absolute type metal inspection probes are effectively and conveniently operated when it is electrically connected, to the dual-typed output indi-cation apparatus having an electric circuit shown in Fig. 5. As apparently shown in Fig. 5, the absolute type probe is electri-cally changed over by an A - D switch and other electric parts such as a balancer, a tuning amplifier, a modulator are used as a common function parts of both the probes. The DC stabilizer is connected to the parts necessary to be electrically stabilized.
The duel-typed output indication apparatus is manufactured by assembling various conventional electric parts.
The resulting data of changing of wall thickness of metallic material is shown in the osciloscope installed in the indication apparatus. The data is recorded in a pen-writing oscilograph recorder in a form of curved line graph of Fig. 4.
Also, the resulting data can be indicated in a digital display device. The oscilograph recorder and the digital display device are driven by a Da amplifier connected to them.
According to the present invention, the needle type ~non-destructive metal inspection probe has generally a standard frequency range including 4 hz and 16 hz. The proper frequency is selected according to the material to be inspected and the wall thickness.
The inspection probe employs a very thin needle as detection cores and exciting cores. Consequently, a small and low-power source is sufficient to effectively operate the detec-tion cores and the exciting cores and, by reason of small and lower electric power and employment of thin needles used for this ~9~
needle cores, the magnetic flux penetrates in depth.
In the preferred embodiments, the respective needle has a diameter of about 0.25 mm, a length of about 40 mm and a pointed end. The whole weight of the probe is only about 100 g.
~ 7 -,. ~.
, :
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A needle type non-destructive metal inspection probe comprising an outer tubular member having a central through hole of a larger diameter, an inner tubular member having a central through hole of a smaller diameter, each of the outer and inner tubular members respectively having a plain land por-tion at its rear end, a grooved land portion at its front end and an intermediate caved portion, said grooved land portions respectively having a plurality of grooves formed therein and arranged circumferencially and longitudinally therein, and an inspection needle core having a first conductor wound thereon and positioned within said central through hole formed in said inner tubular member, a first set of plural exciting needle cores respectively positioned in said grooves of said inner tubular member and having a second conductor wound thereon, a second set of plural exciting needle cores respectively positioned in said longitudinal grooves of said outer tubular member and having another second conductor wound thereon, said first conduc-tor being connectable to an AC power source to detect primarily wall thickness changes, said second conductors being connectable to a DC power source to induce eddy current in the material to be inspected and to magnetize it, and a cylindrical case contain-ing said outer and inner tubular members.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA349,374A CA1100186A (en) | 1976-03-26 | 1980-04-08 | Needle type non-destructive metal inspection probe |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US67097276A | 1976-03-26 | 1976-03-26 | |
| US670,972 | 1976-03-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1098172A true CA1098172A (en) | 1981-03-24 |
Family
ID=24692639
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA264,900A Expired CA1098172A (en) | 1976-03-26 | 1976-11-04 | Needle type non-destructive metal inspection probe |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1098172A (en) |
| GB (1) | GB1559524A (en) |
-
1976
- 1976-07-21 GB GB3031376A patent/GB1559524A/en not_active Expired
- 1976-11-04 CA CA264,900A patent/CA1098172A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1559524A (en) | 1980-01-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| AU595748B2 (en) | Magnetic flux leakage probe with radially offset coils for use in nondestructives testing of pipes and tubes | |
| US4855676A (en) | Ferromagnetic eddy current probe having transmit and receive coil assemblies | |
| US4528856A (en) | Eddy current stress-strain gauge | |
| RU2364860C2 (en) | Detector for definition of internal and external diametres, for device of magnetic flux dispersion control | |
| JP5522699B2 (en) | Nondestructive inspection apparatus and nondestructive inspection method using pulse magnetism | |
| JPH06331602A (en) | Method and equipment for checking structural defect of long magnetic material nondestructively | |
| CA2043694A1 (en) | Eddy current probe, incorporating multi-bracelets of different pancake coil diameters, for detecting internal defects in ferromagnetic tubes | |
| Cheng | Magnetic flux leakage testing of reverse side wall-thinning by using very low strength magnetization | |
| GB2262346A (en) | Detecting defects in steel material | |
| GB2071331A (en) | Non-destructive Testing of Ferromagnetic Articles | |
| US3976936A (en) | Non-destructive metal inspection apparatus using a sharp-pointed pin and coil for producing eddy currents in the inspected article | |
| US2964699A (en) | Probe device for flaw detection | |
| CA1098172A (en) | Needle type non-destructive metal inspection probe | |
| Hartmann et al. | A system for measurement of AC Barkhausen noise in electrical steels | |
| US4675605A (en) | Eddy current probe and method for flaw detection in metals | |
| CA1100186A (en) | Needle type non-destructive metal inspection probe | |
| US5122743A (en) | Apparatus and method of non-destructively testing ferromagnetic materials including flux density measurement and ambient field cancellation | |
| JPH09507294A (en) | Method and apparatus for magnetically testing metal products | |
| GB1070859A (en) | Apparatus for the measurement of changes in diameter of wire or tubular metal and a method for the determination of the corrosion of such metal | |
| CA1203008A (en) | Eddy current flaw detector | |
| JP3223991U (en) | Nondestructive inspection equipment | |
| SU1567964A1 (en) | Method of magnetic inspection of articles | |
| JP2519501Y2 (en) | Magnetic flaw detector | |
| Barbosa et al. | Measurements of surface-breaking flaws in steel pipes using a SQUID susceptometer in an unshielded environment | |
| RU1797031C (en) | Device for inspecting plane-stressed state in the items made of ferromagnetic material |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |