CA2190520A1 - Method of judging plasticization of steel - Google Patents
Method of judging plasticization of steelInfo
- Publication number
- CA2190520A1 CA2190520A1 CA002190520A CA2190520A CA2190520A1 CA 2190520 A1 CA2190520 A1 CA 2190520A1 CA 002190520 A CA002190520 A CA 002190520A CA 2190520 A CA2190520 A CA 2190520A CA 2190520 A1 CA2190520 A1 CA 2190520A1
- Authority
- CA
- Canada
- Prior art keywords
- steel
- magnetic field
- magnetic
- plasticization
- plastic deformation
- 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.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/83—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
Abstract
To provide an effective method of nondestructively and easily judging plasticization of steel used in a real construction. A magnetic sensor 10 is made to scan along the surface of steel to detect a magnetic field caused by a magnetic anisotropy induced by plastic deformation of the steel, and the existence and position of the plasticization is judged from the state of distribution of the magnetic field. As a magnetic sensor, a differential type one comprised of detection coils 10a and 10b, the winding directions of which are opposite to each other, is used to compensate a magnetic field intrinsic to the steel.
Description
2 1 9 û 5 2 0 METHOD OF JUDGING PLASTICIZATION OF STEEL
BACKGROUND OF THE INVENTION
The present invention relates to a method of judging plasticization of steel.
When steel such as steel frames used in a construction as structural bodyis given an overload exceedinga yieldpoint, plastic deformation is caused. When the plastic deformation is large, it is possible to know the plasticization of the steel through macroscopic observation or dimensional measurement.
However, when the plastic deformation is small, since the amount of deformation as the structure is small, or the plastic deformation is concealed by interior materials or fireproof covering materials covering the steel (steel frame), it is difficult to know the existence of the plastic deformation.
In a construction having suffered damages by a big earthquake, it is important to judge whether the structural material was deformed within the range of elastic deformation, or whether it was given a load exceeding the yield point to be plasticized, when considering the continuous usage of the construction and such measures as necessity of reinforcement.
However, there was conventionally only a- method of indirect judgement from observation of a deformed state of the 2 ~ 9 0 5 2 0 construction or observation of damages of interior and exterior materials, that is, there were no effective and suitable technical methods which could directly measure the plasticization of the construction.
Incidentally, as metallurgical methods of judging the plasticization of steel, there are known methods in which the constitution of steel is observed to observe dislocations or slip lines generated in accordance with the plasticization, and oxidizing (etching) the surface of the steel is oxidized(etched) to macroscopically observe a distorted hardened region. However, in order to observe the constitution, it is necessary to pick a sample for observation from the steel and to grind the surface. In the case of observation through etching, after heating the steel to a temperature of 250-300 C, it is necessary to conduct etching by a corrosive liquid.
Accordingly, although both methods can be applied to a small test piece in a laboratory, both are difficult to be applied to a real construction. Further, there has been investigated a method in which a sample is arranged in a detection coil, an alternating voltage is applied to the coil, and the characteristics of alternate current magnetization is detected, whereby the plasticization of the sample is judged (for example, see Japanese Patent Unexamined Application No.
However, also in this case, it is impossible to apply the method to a real construction like the above described metallurgical methods.
In view of the above circumstances, an object of the present invention is to provide an effective method of capable of judging plasticization of steel used in a real construction in a nondestructive manner and with ease.
SUMMARY OF THE INVENTION
The present invention is characterized by comprising the steps of using a differential type magnetic sensor comprised of detection coils with winding directions opposite to each other; scanning along a surface of steel material with the magnetic sensori detecting a magnetic field caused by a magnetic anisotropyinducedby plastic deformation ofthe steel material, and judging existence and position of the plasticizat1on from a state of distribution of the magnetic field.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view showing an example of a magnetic sensor used in the present invention.
Fig. 2 is a perspective view showing another example of a magnetic sensor.
Fig. 3 is a perspective view showing still another example of a magnetic sensor.
Fig. 4 is a view showing a procedure of the present invention, and schematically showing the state in which a magnetic sensor scans the steel in one-dimension.
Fig. 5 is a view schematically showing the one-dimensional distribution of magnetic field obtained by the scan.
Fig. 6 is a view schematically showing the state in which the magnetic sensor scans along the surface of the steel in a plane.
Fig. 7 is a view schematically showing the plane distribution of magnetic field intensity obtained by the scan.
Fig. 8 is a view schematically showing an equal magnetic line diagram depicted based on the distribution of the magnetic field intensity.
Fig. 9 is a view showing examples of real data of equal magnetic diagrams.
Fig. 10 is a view showing a stress-distortion line of the steel.
Fig. 11 is a view schematically showing the mechanism of plasticization of the steel and showing the state of generation .~
of Luders band.
Fig. 12 is a view schematically showing microscopical magnetic characteristics of the steel in an elastic region.
Fig. 13 is a view schematically showing microscopic magnetic characteristics of the steel in which plasticization is generated.
Fig. 14 is a view schematically showing microscopic magnetic characteristics of the steel in which a Luders band is generated.
EMBODIMENT OF THE INVENTION
Embodiments of the present invention will be described hereinafter. First, with reference to Figs. 10 to 14, the principle of the present invention will be described. Fig. 10 shows a curve of stress versus distortion of steel, and Figs.
11 to 14 schematically show the mechanism of plasticization of steel.
The plasticization of steel is caused by generation of dislocations or slip lines in the inside of a crystal. Since the dislocations or slip lines are lattice defects, an uneven stress is generated around them and a magnetic anisotropy induced by the stress is generated. In the present invention, an attention is paid to the magnetic anisotropy generated by plastic deformation, and the existence or position of the -plastic deformation is judged by detecting the magnetic field caused by the magnetic anisotropy.
That is, as shown in Fig. 12, steel 1 is microscopically formed of a number of magnetic domains, and a number of magnetic spins directed in the same direction exist in the respective magnetic domains. However, in an elastic region A, the directions of magnetization of the respective magnetic domains are random, so that the steel 1 shows isotropic magnetization characteristics in total.
When a load near a yield point is applied to the steel 1, as shown in Fig. 13, a dislocation 2 and a slip of a group of dislocations are generated in its constitution. A
microscoplc stress field is generated around the dislocation 2 or the slip, andin a ferromagneticsubstance such as the steel 1, a magnetlc anisotropyinducedbythe stress is generated near the stress field. Further, when a load exceeding a yield point is applied to the steel 1, the steel 1 is not uniformly plastically deformed, but as shown in Fig. 4, inhomogeneous plastic deformation called as Luders band 3 is generated. As shown in Fig. 11, such Luders band 3 gradually expands at lower yield point stress in yielding deformation regions B, C, and D. After the Luders band 3 develops into the entire of the steel 1, a state is put into a distorted hardened region E where the ,. ~
intensity increases as the distortion increases.
Since the Luders band 3 is a portion where slips are gathered, a remarkable magnetic anisotropy is induced in the vicinity thereof. As a result, a magnetic field is formed outside the steel 1. Then, if the magnetic field is detected, the existence and position of the Luders band 3 can be detected, so that plasticization can be judged. However, since the normal steel 1 is ferromagnetic substance, it has also a spontaneous magnetic field, and the magnetic field intrinsic to the steel 1 and the magnetic field caused by the plastic deformation are superimposed outside the steel 1. Accordingly, in order to judge the plasticization, it is necessary to measure only the magnetic field caused by the plastic deformation, that is, it is necessary to compensate the magnetic field intrinsic to the steel 1 to selectively take out only the magnetic field caused by the plastic deformation.
Then, in the present invention, providing that the steel 1 is not magnetized in a specific direction, an attention is paid to a fact that a spatial distribution of the magnetic field intrinsic to the steel 1 is gentle, while a spatial distribution of the magnetic field caused by the plastic deformation causing the Luders band 3 has a large variation since the Luders band 3 is locally generated in the inside of the steel 1. Thus, a ~;~
differential typemagneticsensor, thatis, themagneticsensor of the type in which a local variation of the magnetic field intensity can be detected with high precision, is used to scan the surface of the steel 1, so that the spontaneous magnetic field near the surface of the steel 1 is obtained and from the state of plane distri~ution, the existence and position of the Luders band 3 are detected. That is, if the magnetic fields along the surface of the steel 1 are obtained, and the state ofplane distribution thereof is expressedby an equalmagnetic line diagram = a contour diagram of magnetic field, at the stages where the Luders band 3 is locally generated (yielding deformation regions B, C, and D), the magnetic field abruptly changes at the portion corresponding to the Luders band 3, whereas at the stages where the Luders band 3 is generated in the entire surface of the steel 1 (distorted hardened region E), the plane distribution of the magnetic field has a small variation, whereby the existence, position and degree of plasticization can be judged.
An embodiment of the present invention based on the above-mentioned principle will be described concretely. Fig.
1 shows a magnetic sensor 10 used in this embodiment. This magnetic sensorlOisofa differentialtype andincludes double detection coils lOa and lOb. The respective detection coils lOa 2 ~ 9 0 5 2 0 and lOb have a minute area less than about 1 mm , are arranged concentrically and on the same plane, the numbers of winding are ad~usted so that the areas of which both coils are equal to each other, and the directions of winding are opposite to each other. In this embodiment, when the areas of the detection coils lOa and lOb are S1 and S2, and the numbers of winding are N1 and N2, the numbers and areas are set so as to satisfy the equation ofS1 N1= S2 N2. With the differentialtype magnetic sensor 10 comprisedof the detection coilslOa andlOb with such a minute area, a locally changing magnetic flux can be detected with high precision, and a magnetic flux from a remote magnetic source and a magnetic flux with a gentle variation can be compensated. As the magnetic sensor 10, it is preferable to adopt a high sensibility magnetic flux sensor using, for example, a superconductive quantum interference element, and an area of detected portion of magnetic field can be sufficiently made small so that spatial resolving power can be sufficiently heightened thereby. The detection coils lOa and lOb of the magnetic sensor 10 are not limited to the above described circular ones which are concentrically arranged on the same plane. Forexample, as shown in Fig. 2, detectioncoils llOa and lOb may be arranged with an interval in a vertical direction. Alternatively, as shown in Fig. 3, rectangular or 2 ~ 9 0 5 2 0 polygonal detection coils lOa and lOb may be arranged side by side.
As shown in Fig. 4, since the magnetic field generated by magnetization in the inside of the steel 1 as an objective sample is distributed to the outside of the steel 1, when the above-mentionedmagneticsensorlOis arrangednearthesurface of the steel 1, the magnetic sensor detects the vertical component of the magnetic field. When the magnetic sensor 10 is made to scan in parallel to the surface of the steel, a one-dimensional distribution of magnetic field intensity as shown in Fig. 5 is obtained. Further, as shown in Fig. 6, when the magnetic sensor 10 is made to scan along a rectangular wave-like path over the entire surface of the steel, a plane distribution of magnetic field intensity as shown in Fig. 7 is obtained. Then, scanning points are s~t on the respective scanning lines in accordance with a sampling frequency, the magnetic field intensity at each of the scanning points is converted into digital values through an A/D convertor, and points among the respective scanning points equal in magnetic field intensity are jointed to prepare an equal magnetic line diagram as shown in Fig. 8. Fig. 9(a) shows an example of the equal magneticlinediagraminan elastic regionbasedonactual data. It should be noted that the invention is not limited to ~, 10 't 2~90520 the above described case in which a magnetic field vertical to the steel is measured, but a magnetic field parallel to the surface of the steel may be measured. However, in the case where the magnetic field in the vertical direction is measured, since the directionality of the magnetic field can be neglected, it is more preferable.
If the steel 1 is subject to plastic deformation to generate the magnetic anisotropy in the inside thereof, the distribution of magnetic field caused by the magnetic anisotropy is generated outside the steel 1, which is reflected to the equal magnetic line diagram obtained as described above.
Then, by analyzing the diagram, it is possible to judge the plasticization. That is, as described above, when the Luders band 3 is generated in the yielding deformation regions B, C, and D in the steel 1, the magnetic field abruptly changes at that position, while at the stage where the state of the steel 1 reaches the distorted hardened region E so that the Luders band 3 is generated over the entire surface of the steel 1, the plane distribution of the magnetic field has a small variation.
From the above, it is possible to judge the existence and position of the plasticization, as well as whether the plasticization reaches the distorted hardened region E from the yielding deformation region D, and the like. Figs. 9~b) and (C) 2~90520 show examples of equal magnetic line diagrams in the yielding deformation regions based on actual data, and Fig. 9(d) shows an example of equal magnetic line diagram in the distorted hardened region.
According to the above-described method, by only making the magnetic sensor 10 scan along the surface of the steel 1 of an object to be inspected in a noncontact manner, the spontaneous magnetic field near the surface of the steel 1 is measured and the plasticization can be judged from the state of the plane distribution of the magnetic field. Accordingly, the plasticization of the steel 1 can be judged in a nondestructive manner, and the invention can be easily applied to a realconstructionwithoutanytroublethereby.Especially, in the above-mentioned method, by using the differential type magnetic sensor 10, the magnetic field having a gentle spatial distribution and intrinsic to the steel is compensated, and only steep magnetic field change caused by the plasticization can be effectively detected. Also, using the minute size magnetic sensorlOsuperiorinspatial resolutionpowerenables to measure a local magnetic field caused by the plasticization with high precision.
As described above, according to the present invention, the differential type magnetic sensor is made to scan along the 2~90520 surface of the steel so that the magnetic field caused by the magnetic anisotropy induced by the plastic deformation of the steel is detected and the existence and position of the plasticization is judged from the state of distribution of the magnetic field. Accordingly, without breaking or damaging the steel of an object to be inspected, and without requiring labor such as a specific pretreatment or application of a voltage to a sample, it is possible to effectively judge the existence, position and degree of the plasticization of the steel material.
Therefore, the invention can be applied to a real construction.
As a result, it becomes possible to judge the existence of minute plastic deformation of a real construction which can not be judged by macroscopic observation or dimensional measurement, being extremely effective.
BACKGROUND OF THE INVENTION
The present invention relates to a method of judging plasticization of steel.
When steel such as steel frames used in a construction as structural bodyis given an overload exceedinga yieldpoint, plastic deformation is caused. When the plastic deformation is large, it is possible to know the plasticization of the steel through macroscopic observation or dimensional measurement.
However, when the plastic deformation is small, since the amount of deformation as the structure is small, or the plastic deformation is concealed by interior materials or fireproof covering materials covering the steel (steel frame), it is difficult to know the existence of the plastic deformation.
In a construction having suffered damages by a big earthquake, it is important to judge whether the structural material was deformed within the range of elastic deformation, or whether it was given a load exceeding the yield point to be plasticized, when considering the continuous usage of the construction and such measures as necessity of reinforcement.
However, there was conventionally only a- method of indirect judgement from observation of a deformed state of the 2 ~ 9 0 5 2 0 construction or observation of damages of interior and exterior materials, that is, there were no effective and suitable technical methods which could directly measure the plasticization of the construction.
Incidentally, as metallurgical methods of judging the plasticization of steel, there are known methods in which the constitution of steel is observed to observe dislocations or slip lines generated in accordance with the plasticization, and oxidizing (etching) the surface of the steel is oxidized(etched) to macroscopically observe a distorted hardened region. However, in order to observe the constitution, it is necessary to pick a sample for observation from the steel and to grind the surface. In the case of observation through etching, after heating the steel to a temperature of 250-300 C, it is necessary to conduct etching by a corrosive liquid.
Accordingly, although both methods can be applied to a small test piece in a laboratory, both are difficult to be applied to a real construction. Further, there has been investigated a method in which a sample is arranged in a detection coil, an alternating voltage is applied to the coil, and the characteristics of alternate current magnetization is detected, whereby the plasticization of the sample is judged (for example, see Japanese Patent Unexamined Application No.
However, also in this case, it is impossible to apply the method to a real construction like the above described metallurgical methods.
In view of the above circumstances, an object of the present invention is to provide an effective method of capable of judging plasticization of steel used in a real construction in a nondestructive manner and with ease.
SUMMARY OF THE INVENTION
The present invention is characterized by comprising the steps of using a differential type magnetic sensor comprised of detection coils with winding directions opposite to each other; scanning along a surface of steel material with the magnetic sensori detecting a magnetic field caused by a magnetic anisotropyinducedby plastic deformation ofthe steel material, and judging existence and position of the plasticizat1on from a state of distribution of the magnetic field.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view showing an example of a magnetic sensor used in the present invention.
Fig. 2 is a perspective view showing another example of a magnetic sensor.
Fig. 3 is a perspective view showing still another example of a magnetic sensor.
Fig. 4 is a view showing a procedure of the present invention, and schematically showing the state in which a magnetic sensor scans the steel in one-dimension.
Fig. 5 is a view schematically showing the one-dimensional distribution of magnetic field obtained by the scan.
Fig. 6 is a view schematically showing the state in which the magnetic sensor scans along the surface of the steel in a plane.
Fig. 7 is a view schematically showing the plane distribution of magnetic field intensity obtained by the scan.
Fig. 8 is a view schematically showing an equal magnetic line diagram depicted based on the distribution of the magnetic field intensity.
Fig. 9 is a view showing examples of real data of equal magnetic diagrams.
Fig. 10 is a view showing a stress-distortion line of the steel.
Fig. 11 is a view schematically showing the mechanism of plasticization of the steel and showing the state of generation .~
of Luders band.
Fig. 12 is a view schematically showing microscopical magnetic characteristics of the steel in an elastic region.
Fig. 13 is a view schematically showing microscopic magnetic characteristics of the steel in which plasticization is generated.
Fig. 14 is a view schematically showing microscopic magnetic characteristics of the steel in which a Luders band is generated.
EMBODIMENT OF THE INVENTION
Embodiments of the present invention will be described hereinafter. First, with reference to Figs. 10 to 14, the principle of the present invention will be described. Fig. 10 shows a curve of stress versus distortion of steel, and Figs.
11 to 14 schematically show the mechanism of plasticization of steel.
The plasticization of steel is caused by generation of dislocations or slip lines in the inside of a crystal. Since the dislocations or slip lines are lattice defects, an uneven stress is generated around them and a magnetic anisotropy induced by the stress is generated. In the present invention, an attention is paid to the magnetic anisotropy generated by plastic deformation, and the existence or position of the -plastic deformation is judged by detecting the magnetic field caused by the magnetic anisotropy.
That is, as shown in Fig. 12, steel 1 is microscopically formed of a number of magnetic domains, and a number of magnetic spins directed in the same direction exist in the respective magnetic domains. However, in an elastic region A, the directions of magnetization of the respective magnetic domains are random, so that the steel 1 shows isotropic magnetization characteristics in total.
When a load near a yield point is applied to the steel 1, as shown in Fig. 13, a dislocation 2 and a slip of a group of dislocations are generated in its constitution. A
microscoplc stress field is generated around the dislocation 2 or the slip, andin a ferromagneticsubstance such as the steel 1, a magnetlc anisotropyinducedbythe stress is generated near the stress field. Further, when a load exceeding a yield point is applied to the steel 1, the steel 1 is not uniformly plastically deformed, but as shown in Fig. 4, inhomogeneous plastic deformation called as Luders band 3 is generated. As shown in Fig. 11, such Luders band 3 gradually expands at lower yield point stress in yielding deformation regions B, C, and D. After the Luders band 3 develops into the entire of the steel 1, a state is put into a distorted hardened region E where the ,. ~
intensity increases as the distortion increases.
Since the Luders band 3 is a portion where slips are gathered, a remarkable magnetic anisotropy is induced in the vicinity thereof. As a result, a magnetic field is formed outside the steel 1. Then, if the magnetic field is detected, the existence and position of the Luders band 3 can be detected, so that plasticization can be judged. However, since the normal steel 1 is ferromagnetic substance, it has also a spontaneous magnetic field, and the magnetic field intrinsic to the steel 1 and the magnetic field caused by the plastic deformation are superimposed outside the steel 1. Accordingly, in order to judge the plasticization, it is necessary to measure only the magnetic field caused by the plastic deformation, that is, it is necessary to compensate the magnetic field intrinsic to the steel 1 to selectively take out only the magnetic field caused by the plastic deformation.
Then, in the present invention, providing that the steel 1 is not magnetized in a specific direction, an attention is paid to a fact that a spatial distribution of the magnetic field intrinsic to the steel 1 is gentle, while a spatial distribution of the magnetic field caused by the plastic deformation causing the Luders band 3 has a large variation since the Luders band 3 is locally generated in the inside of the steel 1. Thus, a ~;~
differential typemagneticsensor, thatis, themagneticsensor of the type in which a local variation of the magnetic field intensity can be detected with high precision, is used to scan the surface of the steel 1, so that the spontaneous magnetic field near the surface of the steel 1 is obtained and from the state of plane distri~ution, the existence and position of the Luders band 3 are detected. That is, if the magnetic fields along the surface of the steel 1 are obtained, and the state ofplane distribution thereof is expressedby an equalmagnetic line diagram = a contour diagram of magnetic field, at the stages where the Luders band 3 is locally generated (yielding deformation regions B, C, and D), the magnetic field abruptly changes at the portion corresponding to the Luders band 3, whereas at the stages where the Luders band 3 is generated in the entire surface of the steel 1 (distorted hardened region E), the plane distribution of the magnetic field has a small variation, whereby the existence, position and degree of plasticization can be judged.
An embodiment of the present invention based on the above-mentioned principle will be described concretely. Fig.
1 shows a magnetic sensor 10 used in this embodiment. This magnetic sensorlOisofa differentialtype andincludes double detection coils lOa and lOb. The respective detection coils lOa 2 ~ 9 0 5 2 0 and lOb have a minute area less than about 1 mm , are arranged concentrically and on the same plane, the numbers of winding are ad~usted so that the areas of which both coils are equal to each other, and the directions of winding are opposite to each other. In this embodiment, when the areas of the detection coils lOa and lOb are S1 and S2, and the numbers of winding are N1 and N2, the numbers and areas are set so as to satisfy the equation ofS1 N1= S2 N2. With the differentialtype magnetic sensor 10 comprisedof the detection coilslOa andlOb with such a minute area, a locally changing magnetic flux can be detected with high precision, and a magnetic flux from a remote magnetic source and a magnetic flux with a gentle variation can be compensated. As the magnetic sensor 10, it is preferable to adopt a high sensibility magnetic flux sensor using, for example, a superconductive quantum interference element, and an area of detected portion of magnetic field can be sufficiently made small so that spatial resolving power can be sufficiently heightened thereby. The detection coils lOa and lOb of the magnetic sensor 10 are not limited to the above described circular ones which are concentrically arranged on the same plane. Forexample, as shown in Fig. 2, detectioncoils llOa and lOb may be arranged with an interval in a vertical direction. Alternatively, as shown in Fig. 3, rectangular or 2 ~ 9 0 5 2 0 polygonal detection coils lOa and lOb may be arranged side by side.
As shown in Fig. 4, since the magnetic field generated by magnetization in the inside of the steel 1 as an objective sample is distributed to the outside of the steel 1, when the above-mentionedmagneticsensorlOis arrangednearthesurface of the steel 1, the magnetic sensor detects the vertical component of the magnetic field. When the magnetic sensor 10 is made to scan in parallel to the surface of the steel, a one-dimensional distribution of magnetic field intensity as shown in Fig. 5 is obtained. Further, as shown in Fig. 6, when the magnetic sensor 10 is made to scan along a rectangular wave-like path over the entire surface of the steel, a plane distribution of magnetic field intensity as shown in Fig. 7 is obtained. Then, scanning points are s~t on the respective scanning lines in accordance with a sampling frequency, the magnetic field intensity at each of the scanning points is converted into digital values through an A/D convertor, and points among the respective scanning points equal in magnetic field intensity are jointed to prepare an equal magnetic line diagram as shown in Fig. 8. Fig. 9(a) shows an example of the equal magneticlinediagraminan elastic regionbasedonactual data. It should be noted that the invention is not limited to ~, 10 't 2~90520 the above described case in which a magnetic field vertical to the steel is measured, but a magnetic field parallel to the surface of the steel may be measured. However, in the case where the magnetic field in the vertical direction is measured, since the directionality of the magnetic field can be neglected, it is more preferable.
If the steel 1 is subject to plastic deformation to generate the magnetic anisotropy in the inside thereof, the distribution of magnetic field caused by the magnetic anisotropy is generated outside the steel 1, which is reflected to the equal magnetic line diagram obtained as described above.
Then, by analyzing the diagram, it is possible to judge the plasticization. That is, as described above, when the Luders band 3 is generated in the yielding deformation regions B, C, and D in the steel 1, the magnetic field abruptly changes at that position, while at the stage where the state of the steel 1 reaches the distorted hardened region E so that the Luders band 3 is generated over the entire surface of the steel 1, the plane distribution of the magnetic field has a small variation.
From the above, it is possible to judge the existence and position of the plasticization, as well as whether the plasticization reaches the distorted hardened region E from the yielding deformation region D, and the like. Figs. 9~b) and (C) 2~90520 show examples of equal magnetic line diagrams in the yielding deformation regions based on actual data, and Fig. 9(d) shows an example of equal magnetic line diagram in the distorted hardened region.
According to the above-described method, by only making the magnetic sensor 10 scan along the surface of the steel 1 of an object to be inspected in a noncontact manner, the spontaneous magnetic field near the surface of the steel 1 is measured and the plasticization can be judged from the state of the plane distribution of the magnetic field. Accordingly, the plasticization of the steel 1 can be judged in a nondestructive manner, and the invention can be easily applied to a realconstructionwithoutanytroublethereby.Especially, in the above-mentioned method, by using the differential type magnetic sensor 10, the magnetic field having a gentle spatial distribution and intrinsic to the steel is compensated, and only steep magnetic field change caused by the plasticization can be effectively detected. Also, using the minute size magnetic sensorlOsuperiorinspatial resolutionpowerenables to measure a local magnetic field caused by the plasticization with high precision.
As described above, according to the present invention, the differential type magnetic sensor is made to scan along the 2~90520 surface of the steel so that the magnetic field caused by the magnetic anisotropy induced by the plastic deformation of the steel is detected and the existence and position of the plasticization is judged from the state of distribution of the magnetic field. Accordingly, without breaking or damaging the steel of an object to be inspected, and without requiring labor such as a specific pretreatment or application of a voltage to a sample, it is possible to effectively judge the existence, position and degree of the plasticization of the steel material.
Therefore, the invention can be applied to a real construction.
As a result, it becomes possible to judge the existence of minute plastic deformation of a real construction which can not be judged by macroscopic observation or dimensional measurement, being extremely effective.
Claims
1. A method of judging plasticization of steel characterized by comprising the steps of: using a differential type magnetic sensor comprised of detection coils with winding directions opposite to each other; scanning along the surface of the steel with the magnetic sensor; detecting a magnetic field caused by a magnetic anisotropy induced by plastic deformation of the steel; and judging existence and position of the plasticization from a state of distribution of the magnetic field.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7-300276 | 1995-11-17 | ||
| JP30027695A JP3459506B2 (en) | 1995-11-17 | 1995-11-17 | Method for determining plasticity of steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2190520A1 true CA2190520A1 (en) | 1997-05-18 |
Family
ID=17882847
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002190520A Abandoned CA2190520A1 (en) | 1995-11-17 | 1996-11-15 | Method of judging plasticization of steel |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5982172A (en) |
| EP (1) | EP0774664A1 (en) |
| JP (1) | JP3459506B2 (en) |
| CA (1) | CA2190520A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3160711B2 (en) * | 1997-06-05 | 2001-04-25 | 清水建設株式会社 | Method for determining plasticity of steel |
| JPH1137976A (en) * | 1997-07-18 | 1999-02-12 | Shimizu Corp | Non-destructive quantitative evaluation method for plasticity of steel product |
| JP2002221513A (en) * | 2001-01-25 | 2002-08-09 | Seiji Motojima | Micro sensor and its use |
| FR3057069B1 (en) | 2016-10-03 | 2018-10-26 | Environnement Sa | GAS ANALYZER |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2417525A1 (en) * | 1974-04-10 | 1975-10-30 | Foerster Friedrich Dr | TEST COIL ARRANGEMENT AND PROCEDURE FOR DETERMINING CERTAIN PROPERTIES OF TEST PARTS |
| US4503393A (en) * | 1981-10-05 | 1985-03-05 | Exxon Production Research Co. | Method and apparatus for detecting flaws in the threaded end of an elongate member using electromagnetic excitation and an automated scanning sensor |
| US4528856A (en) * | 1984-01-17 | 1985-07-16 | Westinghouse Electric Corp. | Eddy current stress-strain gauge |
| US4755753A (en) * | 1986-07-23 | 1988-07-05 | General Electric Company | Eddy current surface mapping system for flaw detection |
| JPH0648261B2 (en) * | 1986-11-18 | 1994-06-22 | 大同ほくさん株式会社 | Excitation type thin film pickup coil |
| JP2624828B2 (en) * | 1988-04-06 | 1997-06-25 | 株式会社日立製作所 | Magnetometer and method for detecting deterioration of metal material using the same |
| JPH076950B2 (en) * | 1988-09-14 | 1995-01-30 | 株式会社日立製作所 | Device and method for detecting deterioration of metallic material |
| JP2893714B2 (en) * | 1989-05-25 | 1999-05-24 | 株式会社日立製作所 | Thin film type SQUID magnetometer and biomagnetism measuring device using the same |
| US5331278A (en) * | 1990-09-11 | 1994-07-19 | Hitachi, Ltd. | Apparatus for inspecting degradation/damage of a material using an AC magnet, a superconducting DC magnet and a SQUID sensor |
| US5293119A (en) * | 1992-02-20 | 1994-03-08 | Sqm Technology, Inc. | Electromagnetic microscope for evaluation of electrically conductive and magnetic materials |
| US5308974B1 (en) * | 1992-11-30 | 1998-01-06 | Digital Instr Inc | Scanning probe microscope using stored data for vertical probe positioning |
| US5423223A (en) * | 1993-02-12 | 1995-06-13 | The United States Of America As Represented By The Secretary Of The Air Force | Fatigue detection in steel using squid magnetometry |
| JPH07120436A (en) * | 1993-10-20 | 1995-05-12 | Seiko Instr Inc | Nondestructive examination device |
| DE4342100A1 (en) * | 1993-12-10 | 1995-07-20 | Forschungszentrum Juelich Gmbh | Non-destructive testing of concrete by confocal magnetic tomography |
| GB2417525A (en) * | 2004-08-24 | 2006-03-01 | Kai Shyun Entpr Co Ltd | Caulking gun with push plate angle adjustment |
-
1995
- 1995-11-17 JP JP30027695A patent/JP3459506B2/en not_active Expired - Fee Related
-
1996
- 1996-11-15 CA CA002190520A patent/CA2190520A1/en not_active Abandoned
- 1996-11-15 US US08/746,794 patent/US5982172A/en not_active Expired - Fee Related
- 1996-11-18 EP EP96308322A patent/EP0774664A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09145677A (en) | 1997-06-06 |
| EP0774664A1 (en) | 1997-05-21 |
| JP3459506B2 (en) | 2003-10-20 |
| US5982172A (en) | 1999-11-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |
Effective date: 20011115 |