JP2005345157A - Crack depth inspection method of metallic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate the lift amount of a coil without manufacturing a test piece by utilizing an electromagnetic analysis device, and to obtain a material constant directly from the testing material to dealing with the time sequential change of the metallic material or the material difference adjacent to a crack. <P>SOLUTION: Magnetic flux is generated (S1), the eddy current is introduced and the disturbance of eddy current caused by the existence of the crack is detected and measured (S2) as the actual measurement signal, and stored in the computer (S3). The magnetic material constant data base and the virtual crack depth are inputted (S4), and the virtual crack depth signal is calculated (S5) corresponding to the virtual crack depth by performing the electromagnetic analysis from the material constant. Then, the signal level of the actual measurement signal and that of the virtual crack depth are compared (S6), and determined whether the signal level of the former and that of the latter are coincident (S7) or not. If it is No, only the virtual crack depth is changed (S4), and if it is Yes in S7, the virtual crack depth signal used at the time of the calculation of the electromagnetic analysis is made the crack depth to be obtained (S8) and finalized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for evaluating the soundness and life of a metal material used in equipment, plants, etc., and in particular, a method for inspecting the crack depth of a metal material with high inspection accuracy without depending on the shape of the surface of the metal material. About.

  In the periodic inspection of metal structural members, if the presence of a crack is confirmed by direct visual inspection, indirect visual inspection with a CCD camera, etc., or by a liquid penetration test, etc., prediction of crack growth in the strength of the structure and operating conditions Therefore, it is necessary to evaluate the remaining life of the structure. For this purpose, it is essential to accurately measure and evaluate (inspect) the depth of the detected crack.

  Conventionally, inspection of metal materials for cracks has been performed mainly by ultrasonic flaw detection, but the conventional ultrasonic flaw detection method is effective when the crack is on the opposite side (back side) of the flaw detection surface. However, when a crack exists on the surface side, an eddy current flaw detection method and a leakage magnetic flux flaw detection method are effective in which an external magnetic field is applied to the surface of the metal material to obtain a change in an actual measurement signal depending on the presence or absence of the crack.

  As a method for obtaining information on cracks in the metal material, the eddy current flaw detection method is applied when the metal material is made of a nonmagnetic metal material, while the leakage magnetic flux flaw detection method is applied when the magnetic metal material is used.

  In the case of a nonmagnetic metal material, the leakage magnetic flux generated when an external magnetic field is applied to the surface of the nonmagnetic metal material is very small. Therefore, only information on a low S / N ratio can be obtained. Not suitable.

  On the other hand, in the case of a ferromagnetic metal material, the magnetic permeability due to the application of a magnetic field is remarkably high, so eddy currents occur due to output voltage fluctuations due to local fluctuations in the magnetic permeability and changes in the internal magnetization step due to the magnetic field. The flaw detection method is not suitable.

  In the eddy current flaw detection method, for example, a magnetic field is applied to the metal surface, turbulence of the eddy current is induced on the surface of the metal material by this magnetic field, and these are detected as impedance, thereby detecting a crack generated on the surface of the metal material. It is a method to do. The presence or absence of a crack on the surface of the metal material can be determined by an apparatus using this overflow flaw detection method (see, for example, “Patent Document 1”).

  In addition, if you want to know the depth of cracks in metallic materials in the eddy current testing method and the magnetic flux leakage testing method, artificially created cracks (artificial cracks) are provided on the contrast specimen (test specimen). Create a calibration curve of the relationship between the depth and the magnitude of the measured signal, and compare the output signal obtained by flaw detection of the metal material to be evaluated with the calibration curve created by the artificial crack, and check the actual metal material crack. The depth is inspected.

  In addition, specific material constants (conductivity / permeability) of various materials to be inspected (metal materials), the characteristics of the test object, the magnitude of the magnetic field to be applied, and the positional relationship between the test material and the test object (lifting amount, etc.) In addition, there is an electromagnetic analysis apparatus that performs electromagnetic analysis using an input component having a crack depth as a parameter. With this electromagnetic analysis apparatus, impedance and output voltage (virtual signal) can be obtained as output components.

  A representative example of an electromagnetic analysis apparatus using an electromagnetic analysis method is a trade name MAGNA-FIM of CRC Solutions Co., Ltd.

  Further, the welded portion in the structure may be machined or grinded to make the surface flat, but in reality, it is often used with a surplus of welding left for the purpose of reducing manufacturing costs.

  Finally, there are many places where the metal material is prone to crack in the vicinity of the welded portion, and different materials are mixed in the vicinity of the welded portion. When an external magnetic field is applied from the metal surface in this state and turbulence of the eddy current / leakage magnetic flux induced on the surface of the metal is obtained as an actual measurement signal, an error corresponding to different materials is known.

Alternatively, even when there is a change in material characteristics due to corrosion of the metal material surface (air surface) due to a time series change, the error is known.
JP 2001-349875 A

  The conventional ultrasonic flaw detection method is effective when a crack exists on the opposite side (back side) of the flaw detection surface, but the crack depth inspection when a crack occurs from the flaw detection surface side is a dead zone on the surface. There is a problem that the inspection accuracy deteriorates due to the presence of the probe, and there is a problem that the probe scanning of the ultrasonic flaw detection may not be performed depending on the shape of the structure.

  As in the case of a device using a conventional eddy current flaw detection method, if only the change in the actual measurement signal detected by the detection coil is measured, the presence or absence of a crack generated in the metal material can be determined. The crack depth cannot be inspected.

  When the crack depth is inspected by the eddy current flaw detection method or the leakage magnetic flux flaw detection method, a number of comparison test pieces provided with artificial cracks of various depths are provided on the test piece made of the same material as the metal material. It is necessary to manufacture each type and metal type, and the reliability of the calibration curve due to the manufacturing error of the test piece is lowered, and the inspection accuracy of the crack depth of the metal material is deteriorated.

  An artificial crack is provided by machining such as an EDM notch, but only a specimen with a crack that is 10 to 100 times larger than the width of a naturally occurring crack (natural crack). I can't make it. The reliability of the calibration curve decreases due to the large difference between the width of the artificial crack and the width of the natural crack, and the inspection accuracy of the natural crack depth of the metal material to be evaluated deteriorates.

  In addition, if the welded portion is left on the metal material surface, the test coil does not adhere to the crack surface in the inspection of the crack depth near the toe of the welded portion. A detection error corresponding to the amount of lift (lift-off) occurs. The greater the amount of lift, the lower the reliability of the measured signal and the worse the inspection accuracy of the crack depth of the metal material.

  Finally, if different materials are mixed, such as in the vicinity of the weld, the reliability of the measured signal that detects turbulence in eddy current and leakage flux induced when an external magnetic field is applied from the crack surface is reduced. In addition, the inspection accuracy of the crack depth of the metal material deteriorates.

  Alternatively, turbulence of eddy current and leakage magnetic flux induced when an external magnetic field is applied from the crack surface is detected even with changes in material properties due to corrosion of the metal material surface (air contact surface), etc. The reliability of the actual measurement signal is reduced, and the inspection accuracy of the crack depth of the metal material is deteriorated.

  The present invention has been proposed in order to solve such a problem, and it is possible to avoid deterioration of inspection accuracy when manufacturing a test piece. Further, by using an electromagnetic analysis apparatus, actual measurement from a crack is possible. It is an object of the present invention to provide a method for inspecting a crack depth of a metal material that can accurately inspect the crack depth by directly calculating the signal level of a crack depth virtual signal equivalent to the signal level of the signal.

  Another object of the present invention is to accurately evaluate the amount of lift of the test coil due to the surface shape of the metal material on which the crack has occurred, thereby correcting the decrease in the reliability of the measured signal, and An object of the present invention is to provide a method for inspecting the crack depth of a metal material capable of inspecting the depth with high accuracy.

  A third object of the present invention is to obtain an actual measurement signal by directly obtaining a material constant from a material to be inspected in order to cope with a difference in material near a crack or a change in material characteristics of a metal material in time series. It is an object of the present invention to provide a method for inspecting a crack depth of a metal material that corrects a decrease in reliability of the metal material and can accurately inspect the crack depth in the metal material.

  The method for inspecting the crack depth of a metal material according to the present invention provides a method for inspecting the crack depth of a nonmagnetic metal material as described in claim 1 in order to solve the above-described problem. Applying an external magnetic field from the crack surface of the material to obtain an actual measurement signal correlated with the magnitude of the eddy current disturbance induced in the crack surface layer, and using the known material constants of the nonmagnetic metal material Performing an electromagnetic analysis to obtain a crack depth virtual signal corresponding to the virtual crack depth, and a virtual crack so that the signal level of the crack depth virtual signal approaches the signal level of the actual measurement signal. It is characterized by having a step of repetitively scanning the depth to match both signal levels and obtaining the crack depth of the non-magnetic metal material from the crack depth virtual signal when they match.

  Further, according to the method for inspecting a crack depth of a metal material according to the present invention, when the crack depth of the nonmagnetic metal material is inspected, the shape of the crack surface portion is uneven. Is a calibration that expresses the eddy current output ratio that is induced when a magnetic field is applied from an arbitrary height in the vicinity of a crack that does not include a crack, because the test coil has a lift relative to the nonmagnetic metal material. A curve is created, and the eddy current output ratio is obtained by comparing the lift amount with the calibration curve, thereby correcting the lift amount of the test coil.

  Furthermore, according to the method for inspecting the crack depth of a metal material of the present invention, when inspecting the crack depth of a nonmagnetic metal material, the material constant (conductivity) of the nonmagnetic metal material is defined. When the permeability is unknown, an external magnetic field is applied in advance from a relatively flat crack-proximal portion that does not include a crack of the nonmagnetic metal material, and is induced in the surface layer of the nonmagnetic metal material. Obtaining an actual measurement signal having a correlation with the magnitude of eddy current disturbance and electromagnetic analysis using crack depth = 0 and permeability = α to obtain an electrical conductivity virtual signal corresponding to the virtual electrical conductivity Step, the virtual conductivity is repeatedly scanned so that the signal level of the conductivity virtual signal approaches the signal level of the actual measurement signal to match both signal levels, and from the conductivity virtual signal when they match, The step of obtaining the material constant of the non-magnetic metal material and the previous Applying an external magnetic field from the crack surface of a non-magnetic metal material to obtain an actual measurement signal correlated with the magnitude of the eddy current disturbance induced in the crack surface layer, and electromagnetic analysis using the material constants And obtaining a virtual crack depth signal corresponding to the virtual crack depth, and repeating the virtual crack depth so that the signal level of the virtual crack depth signal approaches the signal level of the actual measurement signal. The method includes a step of scanning and matching both signal levels, and obtaining a crack depth of the nonmagnetic metal material from the virtual crack depth signal when the signal levels match.

  In addition, according to the crack depth inspection method for a metal material of the present invention, when the crack depth of the nonmagnetic metal material is inspected, the shape of the crack surface portion is uneven. In this case, since the test coil has a lift relative to the nonmagnetic metal material, it represents the eddy current output ratio induced when a magnetic field is applied from an arbitrary height in the vicinity of the crack not including the crack. A calibration curve is prepared, and the eddy current output ratio is obtained by comparing the lift amount with the calibration curve, thereby correcting the lift amount of the test coil.

  According to the method for inspecting a crack depth of a metal material according to the present invention, when inspecting the crack depth of a magnetic metal material, an external magnetic field is applied from the crack surface of the magnetic metal material. Applying an electromagnetic wave analysis by using the material constants of the magnetic metal material, and obtaining a measured signal by detecting disturbance of leakage magnetic flux induced in the crack surface layer portion of the magnetic metal material A step of obtaining a virtual crack depth signal corresponding to the crack depth, and repeatedly scanning the virtual crack depth so that the signal level of the virtual crack depth signal approaches the signal level of the actual measurement signal. It has the process of making the signal level match and obtaining the crack depth of the magnetic metal material from the crack depth virtual signal when they match.

  Further, according to the method for inspecting a crack depth of a metal material according to the present invention, when the crack depth of the magnetic metal material is inspected as described in claim 6, Because the test coil has a lift relative to the magnetic metal material, a calibration curve representing the leakage flux output ratio induced when a magnetic field is applied from an arbitrary height in the vicinity of the crack not including the crack is shown. It is characterized in that the amount of lift of the test coil is corrected by calculating the leakage magnetic flux output ratio by comparing the amount of lift with the calibration curve.

  In addition, according to the method for inspecting the crack depth of a metal material according to the present invention, when the crack depth of the magnetic metal material is inspected, the material constant (conductivity · If the magnetic permeability is unknown, an external magnetic field is applied in advance from a relatively flat crack-proximal portion that does not include a crack of the magnetic metal material, and the leakage magnetic flux induced in the surface of the magnetic metal material is reduced. A step of obtaining an actual measurement signal having a correlation with the magnitude of disturbance, a step of performing an electromagnetic analysis using crack depth = 0 and permeability = β, and obtaining a conductivity virtual signal corresponding to the virtual conductivity, The virtual conductivity is repeatedly scanned so that the signal level of the conductivity virtual signal approaches the signal level of the actual measurement signal to match both signal levels, and from the conductivity virtual signal when they match, the magnetic metal material And obtaining the material constant of the magnetic metal material An external magnetic field is applied from the crack surface of the crack to obtain a measured signal having a correlation with the magnitude of the leakage magnetic flux disturbance induced in the crack surface layer portion, and an electromagnetic analysis using the material constants is performed. A step of obtaining a virtual crack depth signal corresponding to the crack depth, and repeatedly scanning the virtual crack depth so that the signal level of the virtual crack depth signal approaches the signal level of the actual measurement signal. It has the process of making the signal level match and obtaining the crack depth of the magnetic metal material from the crack depth virtual signal when they match.

  Further, according to the method for inspecting a crack depth of a metal material according to the present invention, when the crack depth of the magnetic metal material is inspected as described in claim 8, Because the test coil has a lift relative to the magnetic metal material, a calibration curve representing the leakage flux output ratio induced when a magnetic field is applied from an arbitrary height in the vicinity of the crack not including the crack is shown. It is characterized in that the amount of lift of the test coil is corrected by calculating the leakage magnetic flux output ratio by comparing the amount of lift with the calibration curve.

  According to the present invention, it is possible to avoid deterioration of inspection accuracy when manufacturing a test piece, and further, by using an electromagnetic analysis device, a crack depth virtual signal equivalent to the signal level of an actual measurement signal from a crack is obtained. By directly calculating the signal level, it is possible to provide a crack depth inspection method for a metal material that can accurately inspect the crack depth.

  In addition, by accurately evaluating the amount of test coil lift due to the surface shape of the metal material with cracks, the reliability of the measured signal is corrected and the crack depth in the metal material is accurately inspected. It is possible to provide a method for inspecting the crack depth of a metal material.

  In addition, in order to respond to differences in the material near the crack or changes in the material properties of the metal material in time series, the decrease in the reliability of the measured signal is corrected by obtaining the material constant directly from the material to be inspected. In addition, it is possible to provide a method for inspecting the crack depth of a metal material that can accurately inspect the crack depth in the metal material.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a crack depth inspection method for a metal material according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a schematic view of an eddy current flaw detector as a crack depth inspection apparatus that inspects the crack depth of a metal material using an eddy current flaw detection method. The eddy current flaw detector 1 has a configuration in which a computer 2 such as a personal computer and a flaw detection probe 3 are connected via a connection cable 4.

  The computer 2 of the eddy current flaw detector 1 has a transmitter, a frequency setter, etc. as a magnetic flux generating function, and a bridge circuit, an AC amplifier, a phase detector, a phase shifter, etc. for measuring impedance and output voltage. Is built in.

  Furthermore, the computer 2 of the eddy current flaw detector 1 includes a material database unit, an electromagnetic analysis unit, and a comparison unit that inspect the crack depth based on the detected impedance / output voltage.

  Further, the flaw detection probe 3 of the eddy current flaw detector 1 includes a test coil 5 at the tip thereof. The test coil 5 has an excitation coil (primary coil) for generating magnetic flux and a detection coil (two coils) for detecting eddy current. Secondary coils). In addition, the detection coil provided in the test coil 5 is electrically connected to a bridge circuit inside the computer 2 of the eddy current flaw detector 1 and constitutes a part of the bridge circuit.

  Further, the connection cable 4 can freely set the distance between the computer 2 and the flaw detection probe 3, and electrically connects the computer 2 and the flaw detection probe 3.

  When a magnetic field is applied to the surface of a nonmagnetic metal material including a crack by the eddy current flaw detector 1 of FIG. 1, the eddy current is disturbed due to the presence of the crack, thereby causing a change in impedance in a bridge circuit provided in the computer 2. A voltmeter can be provided in the bridge circuit, and the presence or absence of cracks and the crack depth can be measured.

  FIG. 2 shows a first example of a crack depth inspection method for a metal material according to the present invention.

  A crack 13 having a crack depth D is generated in a nonmagnetic metal material 11 such as stainless steel or manganese steel, and the test coil 5 at the tip of the flaw detection probe 3 is formed on the metal surface of the nonmagnetic metal material 11. set.

  Here, a current is supplied to the bridge circuit from the power source provided in the computer 2 of FIG. An eddy current is induced in the surface layer of the nonmagnetic metal material 11 by the magnetic flux generated from the exciting coil of the test coil 5 constituting a part of the bridge circuit, and the eddy current disturbance due to the crack depth D is detected by the test coil 5. Detect with a coil.

  FIG. 3 is a flowchart showing a first embodiment of a crack depth inspection method for a metal material.

  The flow chart of FIG. 3 applies to the inspection of the crack depth D of the metal material when the material constant (conductivity / permeability) is known for the non-magnetic metal material 11 as the metal material as shown in FIG. Is done.

  First, a current is supplied to the bridge circuit by the power supply inside the computer 2, and a magnetic flux is generated from the excitation coil of the test coil 5 that constitutes a part of the bridge circuit (S1).

  Next, an eddy current is induced in the surface layer portion of the nonmagnetic metal material 11 by this magnetic flux, and the eddy current is disturbed due to the presence of the crack 13. This eddy current disturbance is detected by the detection coil of the test coil 5, and the detected value is measured as an actual measurement signal (impedance and output voltage) by the bridge circuit (S2). Further, the obtained actual measurement signal is stored in the computer 2 (S3).

  In addition, the electromagnetic material constant database is input to the computer 2, and an arbitrarily set crack depth (virtual crack depth) is input (S4).

  Here, the electromagnetic material constant database refers to the material constant of the material to be inspected (here, nonmagnetic metal material), the characteristics of the inspection object (here, the test coil), and the positional relationship between the inspection material and the inspection object (lifting amount, etc.) ) And a set of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S4, a crack depth virtual signal corresponding to the virtual crack depth is calculated (S5).

  Next, the signal level of the crack depth virtual signal is compared with the signal level of the actually measured signal by a comparison unit inside the computer 2 (S6), and it is determined whether the signal level of the crack depth virtual signal matches the signal level of the actually measured signal. (S7).

  In the case of No in S7, that is, if the signal level of the actually measured signal and the signal level of the crack depth virtual signal do not match, only the virtual crack depth is changed (S4).

  In addition, in the case of Yes in S7, that is, if the signal level of the actual measurement signal matches the signal level of the crack depth virtual signal, the virtual crack depth used when the crack depth virtual signal was obtained by electromagnetic analysis, The desired crack depth is determined (S8), and the process ends.

  According to the flowchart of FIG. 3, when the material constant (conductivity / permeability) is known for a non-magnetic metal material, it is possible to avoid deterioration of inspection accuracy when manufacturing a test piece. The crack depth can be inspected with high accuracy by directly calculating the signal level of the crack virtual signal equivalent to the signal level of the actual measurement signal from the crack.

  In addition, even when there is a test coil lift due to the surface shape of the metal material where the crack has occurred, an electromagnetic analysis that takes the lift into account is performed by accurately evaluating the lift, and the measured signal It is possible to correct the decrease in reliability and accurately inspect the crack depth in the metal material.

  FIG. 4 shows a second example of the crack depth inspection method for a metal material according to the present invention.

  There is a welded portion 15 in the nonmagnetic metal material 11, and the test coil 5 at the tip of the flaw detection probe 3 cannot be brought into close contact with the surface of the nonmagnetic metal material 11 due to the surplus of the welded portion 15, The test coil 5 is provided in a lifted state with a desired lift amount H.

  In FIG. 4, the same members as those shown in FIG.

  Here, a current is supplied to the bridge circuit from the power source provided in the computer 2 of FIG. An eddy current is induced in the surface layer of the nonmagnetic metal material 11 by the magnetic flux generated from the exciting coil of the test coil 5 constituting a part of the bridge circuit, and the eddy current disturbance due to the crack depth D is detected by the test coil 5. Detect with a coil.

  Moreover, what causes the test coil 5 to have the lifting amount H is not limited to the surplus of the welded portion 15.

  FIG. 5 is a flowchart showing a second embodiment of a crack depth inspection method for a metal material.

  The flow chart of FIG. 5 targets the non-magnetic metal material 11 as the metal material as shown in FIG. 4, and the metal in the case where the material constant (conductivity / permeability) is known when the lift amount of the test coil 5 exists. Applies to inspection of crack depth D of material.

  First, the shape of the crack surface of the non-magnetic metal material 11 is cast, or the distance of the test coil 5 from the surface of the non-magnetic metal material 11 is measured by a laser displacement meter or the like, whereby the lift amount H of the test coil 5 is measured. Is measured (S10).

  Next, a current is supplied to the bridge circuit by the power supply inside the computer 2, and a magnetic flux is generated from the excitation coil of the test coil 5 constituting a part of the bridge circuit (S11).

  Next, an eddy current is induced in the surface layer portion of the nonmagnetic metal material 11 by this magnetic flux, and the eddy current is disturbed due to the presence of the crack 13. This eddy current disturbance is detected by the detection coil of the test coil 5, and the detected value is measured as an actual measurement signal (impedance and output voltage) by the bridge circuit (S12). Further, the obtained actual measurement signal is stored in the computer 2 (S13).

  Further, the electromagnetic material constant database is input to the computer 2, and in addition, the lift amount H obtained in S10 and the arbitrarily set crack depth (virtual crack depth) are input (S14).

  Here, the electromagnetic material constant database refers to the material constant of the material to be inspected (here, nonmagnetic metal material), the characteristics of the inspection object (here, the test coil), and the positional relationship between the inspection material and the inspection object (lifting amount, etc.) ) And a set of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S14, a crack depth virtual signal corresponding to the virtual crack depth is calculated (S15).

  Next, the signal level of the crack depth virtual signal is compared with the signal level of the actually measured signal by a comparison unit in the computer 2 (S16), and it is determined whether the signal level of the crack depth virtual signal matches the signal level of the actually measured signal. (S17).

  In the case of No in S17, that is, if the signal level of the actual measurement signal does not match the signal level of the crack depth virtual signal, only the virtual crack depth is changed (S14).

  In addition, in the case of Yes in S17, that is, if the signal level of the actual measurement signal and the signal level of the crack depth virtual signal match, the virtual crack depth used when the crack depth virtual signal was obtained by electromagnetic analysis, The desired crack depth is determined (S18), and the process ends.

  According to the flowchart of FIG. 5, the test piece is for a non-magnetic metal material, where the test coil is lifted and cannot be in close contact with the non-magnetic metal material, and the material constant (conductivity / permeability) is known. By using an electromagnetic analysis device, the signal level of the virtual crack depth signal can be directly calculated using the electromagnetic analysis device. The crack depth can be inspected with high accuracy.

  In addition, by accurately evaluating the amount of lift of the test coil, electromagnetic analysis can be performed in consideration of the amount of lift, and the decrease in the reliability of the measured signal can be corrected, and the crack depth in the metal material can be accurately inspected.

  FIG. 6 is a flowchart showing a third embodiment of a crack depth inspection method for a metal material.

  The flow chart of FIG. 6 targets the non-magnetic metal material 11 as the metal material as shown in FIG. 4, and when the test coil 5 is lifted up, the metal constant when the material constant (conductivity / permeability) is known is shown. Applies to inspection of crack depth D. That is, the same conditions as in the flowchart of FIG.

  First, the shape of the crack surface of the non-magnetic metal material 11 is cast, or the distance of the test coil 5 from the surface of the non-magnetic metal material 11 is measured by a laser displacement meter or the like, whereby the lift amount H of the test coil 5 is measured. Is measured (S20).

  Next, a current is supplied to the bridge circuit by the power source inside the computer 2, and a magnetic flux is generated from the excitation coil of the test coil 5 constituting a part of the bridge circuit (S21).

  Next, an eddy current is induced in the surface layer portion of the nonmagnetic metal material 11 by this magnetic flux, and the eddy current is disturbed due to the presence of the crack 13. This eddy current disturbance is detected by the detection coil of the test coil 5, and the detected value is measured as an actual measurement signal (impedance and output voltage) by the bridge circuit (S22). Further, the obtained actual measurement signal is stored in the computer 2 (S23).

  In addition, the electromagnetic material constant database is input to the computer 2, and an arbitrarily set crack depth (virtual crack depth) is input (S24).

  Here, the electromagnetic material constant database refers to the material constant of the material to be inspected (here, nonmagnetic metal material), the characteristics of the inspection object (here, test coil), and the positional relationship between the inspection material and the inspection object (lifting amount). This is an aggregate of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S24, a virtual crack depth signal corresponding to the virtual crack depth is calculated (S25).

  Next, the signal level of the actual measurement signal and the level of the crack depth virtual signal are compared by the comparator in the computer 2 (S26), and it is determined whether the signal level of the actual measurement signal and the signal level of the crack depth virtual signal match. (S27).

  In the case of No in S27, that is, if the signal level of the actual measurement signal does not match the signal level of the crack depth virtual signal, only the virtual crack depth is changed (S24).

  In the case of Yes in S27, that is, if the signal level of the actual measurement signal and the signal level of the crack depth virtual signal match, the virtual crack depth used when the crack depth virtual signal is obtained by electromagnetic analysis is determined. (S28).

Then, in the vicinity of the non-magnetic metal material 11 Crack 13, a nonmagnetic metal material 11 surface without the relatively flat Without crack 13, intentionally to have a floating amount H _n to the test coil 5, the test coil 5 to generate a magnetic flux, determine the eddy current output value in each of the floating amount H _n.

In the eddy current output value obtained above, the eddy current output value generated when the test coil 5 is brought into close contact with the surface of the non-magnetic metal material 11 and the lift amount H ₀ is defined as an eddy current output ratio of 100%. It represents the eddy current output value produced when having a floating amount H _n eddy current output ratio as (%), to create a calibration curve of the lift amount H _n and the eddy current power ratio (S29).

  Finally, the calibration curve created in S29 is compared with the lifting amount obtained in S20 to obtain the eddy current output ratio, and this eddy current output ratio is multiplied by the virtual crack depth determined in S28 to obtain the crack. The depth is finished (S30).

  According to the flowchart of FIG. 6, the test piece is for a non-magnetic metal material, where the test coil is lifted up and cannot be in close contact with the non-magnetic metal material, and the material constant (conductivity / permeability) is known. By using an electromagnetic analysis device, the signal level of the virtual crack depth signal can be directly calculated using the electromagnetic analysis device. The crack depth can be inspected with high accuracy.

  In addition, by accurately evaluating the amount of lift of the test coil, it is possible to correct a decrease in the reliability of the actual measurement signal and accurately inspect the crack depth in the metal material.

Figure 7 shows an example of a calibration curve of the lift amount H _n and the eddy current power ratio of the test coil 5.

In the case of stainless steel non-magnetic metal material 11 and to, for example, stainless 304, as shown in FIG. 7, there is a strong correlation and lift amount H _n and the eddy current power ratio of the test coil. By using this calibration curve, it is possible to easily obtain a highly reliable eddy current output ratio (%) from the lift amount H _n (mm) of an arbitrary test coil.

  FIG. 8 shows a third example of the crack depth inspection method for a metal material according to the present invention.

  In the vicinity of the crack 13 of the nonmagnetic metal material 11, the test coil 5 is brought into close contact with the surface of the nonmagnetic metal material 11 that does not include the relatively flat crack 13.

  In FIG. 8, the same members as those shown in FIG.

  FIG. 9 is a flowchart showing a fourth embodiment of the method for inspecting the crack depth of a metal material.

  The flowchart of FIG. 9 is a flowchart for determining an unknown material constant (conductivity / magnetic permeability) for a non-magnetic metal material 11 as a metal material as shown in FIG. This is applied when the material constant of the nonmagnetic metal material to be inspected is unknown, and is performed prior to any one of the flowcharts of FIGS.

  First, a current is supplied to the bridge circuit by the power supply inside the computer 2, and a magnetic flux is generated from the excitation coil of the test coil 5 constituting a part of the bridge circuit (S31).

  Next, an eddy current is induced in the surface layer portion of the nonmagnetic metal material 11 by this magnetic flux, and the eddy current is disturbed due to the presence of the crack 13. This eddy current disturbance is detected by the detection coil of the test coil 5, and the detected value is measured as an actual measurement signal (impedance and output voltage) by the bridge circuit (S32). Further, the obtained actual measurement signal is stored in the computer 2 (S33).

  In addition, an electromagnetic material constant database is input to the computer 2, and in addition, magnetic permeability = α (for example, α = 1) and arbitrarily set conductivity (virtual conductivity) are input (S34).

  Here, the electromagnetic material constant database is the material constant of the material to be inspected (here, non-magnetic metal material), the characteristics of the inspection object (here, the test coil), and the positional relationship between the inspection material and the inspection object (lifting amount). This is an aggregate of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S34, a conductivity virtual signal corresponding to the virtual conductivity is calculated (S35).

  Next, the signal level of the actual measurement signal and the signal level of the electrical conductivity virtual signal are compared with each other in the comparison unit inside the computer 2 (S36), and it is determined whether the signal level of the actual measurement signal and the signal level of the electrical conductivity virtual signal match (S36). S37).

  In the case of No in S37, that is, if the signal level of the actual measurement signal does not match the signal level of the conductivity virtual signal, only the virtual crack depth is changed (S34).

  In the case of Yes in S37, that is, if the signal level of the actual measurement signal matches the signal level of the conductivity virtual signal, the virtual conductivity used when the conductivity virtual signal is obtained by electromagnetic analysis is set as the obtained conductivity. (S38).

  Next, when obtaining S38, it is determined whether or not there is a lifting amount H between the nonmagnetic metal material 11 and the test coil 5 (S39).

  In the case of No in S39, that is, when there is no lifting amount H between the nonmagnetic metal material 11 and the test coil 5, the material constant obtained in S38 is used to start the nonmagnetic metal material 11 from S1 in FIG. The crack depth D is determined.

  On the other hand, in the case of Yes in S39, that is, when there is a lifting amount H between the non-magnetic metal material 11 and the test coil 5, the material constant obtained in S38 is used from S10 in FIG. 5 or in FIG. The crack depth D of the nonmagnetic metal material 11 is obtained from S20.

  According to the flowchart of FIG. 9, when the material constant (conductivity / permeability) is unknown for a non-magnetic metal material, the difference in the material near the crack or the change in the material characteristics of the metal material in time series In order to cope with this, by obtaining the material constant directly from the material to be inspected, it is possible to correct the decrease in the reliability of the measured signal and to accurately inspect the crack depth in the metal material.

  In addition, the crack depth of the nonmagnetic metal material can be accurately inspected by continuously performing the processing shown in FIG. 3, FIG. 5 or FIG. 6 from the material constant of the material to be inspected obtained in FIG.

  FIG. 10 shows a schematic view of a leakage flux flaw detector as a crack analysis device for inspecting the crack depth of a metal material using a leakage flux flaw detection method. In the leakage flux flaw detector 21, a computer 22 such as a personal computer and a flaw detection probe 23 are connected via a connection cable 24.

  The computer 22 of the leakage flux flaw detector 21 has a transmitter, a frequency setter, etc. as a magnetic flux generation function, and an AC amplifier, a phase detector, a phase shifter, etc. for measuring impedance and output voltage are incorporated. Configured.

  Furthermore, the computer 22 of the leakage flux flaw detector 21 includes a material database unit, an electromagnetic analysis unit, and a comparison unit that inspect the crack depth based on the detected impedance / output voltage.

  Further, the flaw detection probe 23 of the leakage flux flaw detector 21 is provided with a test coil 25 at its tip, and the test coil 25 is provided with an excitation coil for generating magnetic flux and a detector for detecting leakage flux. .

  Further, the connection cable 24 can freely set the distance between the computer 22 and the flaw detection probe 23 and electrically connects the computer 22 and the flaw detection probe 23.

  When a magnetic field is applied to the surface of the magnetic metal material including the crack by the leakage flux flaw detector 21 of FIG. 10, the leakage flux is disturbed due to the presence of the crack, thereby causing a change in impedance. The computer 22 can be provided with a voltmeter, and the presence or absence of a crack and the depth of the crack can be measured.

  FIG. 11 shows a fourth example of the crack depth inspection method for a metal material according to the present invention.

  A crack 33 having a crack depth D is generated in the magnetic metal material 31, for example, iron, cobalt, or nickel, and the test coil 25 at the tip of the flaw detection probe 23 is set on the metal surface of the magnetic metal material 31. .

  Here, a current is supplied from the power source provided in the computer 22 of FIG. The magnetic flux generated from the exciting coil of the test coil 25 induces a leakage magnetic flux in the surface layer portion of the magnetic metal material 31, and the disturbance of the leakage magnetic flux due to the crack depth D is detected by the detector of the test coil 25.

  FIG. 12 is a flowchart showing a fifth embodiment of a crack depth inspection method for a metal material.

  The flowchart of FIG. 12 is applied to the inspection of the crack depth D of the metal material when the magnetic material 31 is a target metal material as shown in FIG. 11 and the material constant (conductivity / permeability) is known. The

  First, a current is supplied from the power source inside the computer 22 and a magnetic flux is generated from the exciting coil of the test coil 25 (S41).

  Next, a leakage magnetic flux is induced in the surface layer portion of the magnetic metal material 31 by this magnetic flux, and the leakage magnetic flux is disturbed by the presence of the crack 33. The disturbance of the leakage magnetic flux is detected by the detector of the test coil 25, and the detected value is measured as an actual measurement signal (impedance and output voltage) (S42). Further, the obtained actual measurement signal is stored in the computer 22 (S43).

  In addition, the electromagnetic material constant database is input to the computer 22, and an arbitrarily set crack depth (virtual crack depth) is input (S44).

  Here, the electromagnetic material constant database is a material constant of a material to be inspected (here, a magnetic metal material), characteristics of an inspection object (here, a test coil), and a positional relationship between the inspection material and the inspection object (lifting amount, etc.) This is an aggregate of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S44, a virtual crack depth signal corresponding to the virtual crack depth is calculated (S45).

  Next, the signal level of the actual measurement signal and the signal level of the virtual crack depth signal are compared by a comparison unit inside the computer 22 (S46), and it is determined whether the signal level of the actual measurement signal and the signal level of the virtual crack depth signal match. (S47).

  In the case of No in S47, that is, if the signal level of the actual measurement signal does not match the signal level of the crack depth virtual signal, only the virtual crack depth is changed (S44).

  In addition, in the case of Yes in S47, that is, if the signal level of the actual measurement signal matches the signal level of the crack depth virtual signal, the virtual crack depth used when the crack depth virtual signal was obtained by electromagnetic analysis, The desired crack depth is determined (S48), and the process ends.

  According to the flowchart of FIG. 12, when a magnetic metal material is a target and the material constants (conductivity / permeability) are known, it is possible to avoid deterioration of inspection accuracy when manufacturing a test piece, and further use an electromagnetic analysis device. Then, by directly calculating the signal level of the crack depth virtual signal equivalent to the signal level of the actual measurement signal from the crack, the crack depth can be inspected with high accuracy.

  In addition, even when there is a test coil lift amount due to the surface shape of the metal material where the crack has occurred, an electromagnetic analysis that takes the lift amount into account is performed by accurately evaluating the lift amount. It is possible to correct the decrease in reliability and accurately inspect the crack depth in the metal material.

  FIG. 13 shows a fifth example of the crack depth inspection method for a metal material according to the present invention.

  There is a welded portion 35 in the magnetic metal material 31, and the test coil 25 at the tip of the flaw detection probe 23 cannot be brought into close contact with the surface of the nonmagnetic metal material 31 due to the surplus of the welded portion 35. The test coil 25 is provided in a lifted state having a lift amount H of.

  In FIG. 13, the same members as those shown in FIG.

  Here, a current is supplied from the power source provided in the computer 22 of FIG. The magnetic flux generated from the exciting coil of the test coil 25 induces a leakage magnetic flux in the surface layer portion of the magnetic metal material 31, and the disturbance of the leakage magnetic flux due to the crack depth D is detected by the detector of the test coil 25.

  Further, what causes the test coil 25 to have the lifting amount H is not limited to the extra welding of the welded portion 35.

  FIG. 14 is a flowchart showing a sixth embodiment of the crack depth inspection method for a metal material.

  The flow chart of FIG. 14 targets the magnetic metal material 31 as the metal material as shown in FIG. 13, and when the test coil 25 has a lift amount, the metal constant when the material constant (conductivity / permeability) is known is shown in FIG. Applies to inspection of crack depth D.

  First, the shape of the crack surface of the magnetic metal material 31 is formed, or the distance H of the test coil 25 from the surface of the magnetic metal material 31 is measured by a laser displacement meter or the like, thereby measuring the lift amount H of the test coil 25. (S50).

  Next, a current is supplied from the power supply inside the computer 22 and a magnetic flux is generated from the exciting coil of the test coil 25 (S51).

  Next, a leakage magnetic flux is induced in the surface layer portion of the magnetic metal material 31 by this magnetic flux, and the leakage magnetic flux is disturbed by the presence of the crack 33. The disturbance of the leakage magnetic flux is detected by the detection coil of the test coil 25, and the detected value is measured as an actual measurement signal (impedance and output voltage) (S52). Further, the obtained actual measurement signal is stored in the computer 22 (S53).

  Further, the electromagnetic material constant database is input to the computer 22 and, in addition, the lifting amount H obtained in S50 and the arbitrarily set crack depth (virtual crack depth) are input (S54).

  Here, the electromagnetic material constant database is a material constant of a material to be inspected (here, a magnetic metal material), characteristics of an inspection object (here, a test coil), and a positional relationship between the inspection material and the inspection object (lifting amount, etc.) This is an aggregate of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S54, a virtual crack depth signal corresponding to the virtual crack depth is calculated (S55).

  Next, the signal level of the crack depth virtual signal is compared with the signal level of the actually measured signal by the comparison unit inside the computer 2 (S56), and it is determined whether the signal level of the crack depth virtual signal matches the signal level of the actually measured signal. (S57).

  In the case of No in S57, that is, if the signal level of the actual measurement signal and the signal level of the crack depth virtual signal do not match, only the virtual crack depth is changed (S54).

  In addition, in the case of Yes in S57, that is, if the signal level of the actual measurement signal matches the signal level of the crack depth virtual signal, the virtual crack depth used when the crack depth virtual signal was obtained by electromagnetic analysis, The desired crack depth is determined (S58), and the process ends.

  According to the flowchart of FIG. 14, a test piece is manufactured when a magnetic metal material is the target and the test coil is lifted up and cannot be in close contact with the magnetic metal material, and the material constant (conductivity / permeability) is known. In addition, it is possible to avoid deterioration of the inspection accuracy when performing the inspection, and by directly calculating the signal level of the virtual crack depth signal equivalent to the signal level of the actual measurement signal from the crack using an electromagnetic analyzer. The crack depth can be accurately inspected.

  In addition, by accurately evaluating the amount of lift of the test coil, electromagnetic analysis can be performed in consideration of the amount of lift, and the decrease in the reliability of the measured signal can be corrected, and the crack depth in the metal material can be accurately inspected.

  FIG. 15 is a flowchart showing a seventh embodiment of the method for inspecting the crack depth of a metal material.

  The flow chart of FIG. 15 targets the magnetic metal material 31 as the metal material as shown in FIG. 14, and when the lifting amount of the test coil 25 exists, the metal material when the material constant (conductivity / magnetic permeability) is known It is applied to the inspection of crack depth D. That is, the same conditions as in the flowchart of FIG. 14 are shown, but the operation is different.

  First, the shape of the crack surface of the magnetic metal material 31 is formed, or the distance H of the test coil 25 from the surface of the magnetic metal material 31 is measured by a laser displacement meter or the like, thereby measuring the lift amount H of the test coil 25. (S60).

  Next, a current is supplied from the power source inside the computer 22 and a magnetic flux is generated from the exciting coil of the test coil 25 (S61).

  Next, a leakage magnetic flux is induced in the surface layer portion of the magnetic metal material 31 by this magnetic flux, and the leakage magnetic flux is disturbed by the presence of the crack 33. The disturbance of the leakage magnetic flux is detected by the detector of the test coil 25, and the detected value is measured as an actual measurement signal (impedance and output voltage) (S62). Furthermore, the obtained actual measurement signal is stored in the computer 22 (S63).

  In addition, the electromagnetic material constant database is input to the computer 22, and in addition, an arbitrarily set crack depth (virtual crack depth) is input (S64).

  Here, the electromagnetic material constant database refers to the material constant of the material to be inspected (here, a magnetic metal material), the characteristics of the inspection object (here, the test coil), and the positional relationship between the inspection material and the inspection object (lifting amount). This is an aggregate of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S64, a crack depth virtual signal corresponding to the virtual crack depth is calculated (S65).

  Next, the signal level of the crack depth virtual signal is compared with the signal level of the actually measured signal by a comparison unit inside the computer 2 (S66), and it is determined whether the signal level of the crack depth virtual signal matches the signal level of the actually measured signal. (S67).

  In the case of No in S67, that is, if the signal level of the actual measurement signal does not match the signal level of the crack depth virtual signal, only the virtual crack depth is changed (S64).

  Further, in the case of Yes in S67, that is, if the signal level of the actual measurement signal and the signal level of the crack depth virtual signal match, the virtual crack depth used when the crack depth virtual signal is obtained by electromagnetic analysis is determined. (S68).

Next, on the surface of the magnetic metal material 31 that does not include the relatively flat crack 33 in the vicinity of the crack 33 of the magnetic metal material 31, the test coil 25 is intentionally given a lift amount H _n , and a magnetic flux is applied to the test coil 25. It is generated, determining the leakage flux output value in each of the floating amount H _n.

In the leakage magnetic flux output value obtained above, the leakage magnetic flux output value generated when the test coil 25 is brought into close contact with the surface of the magnetic metal material 31 and the floating amount H ₀ is defined as a leakage magnetic flux output ratio of 100%. leakage flux output value produced when having a quantity H _n expressed as leakage flux output ratio (%), to create a calibration curve of the lift amount H _n leakage flux output ratio (S69).

Finally, the calibration curve prepared in S69, obtains a leakage flux output ratio against the floating amount H _n determined at S60, by multiplying the leakage flux output ratio in Virtual Crack裂深is determined in S68, obtains Finish the crack depth (S70).

  According to the flowchart of FIG. 15, a test piece is manufactured for a magnetic metal material, where the test coil is lifted up and cannot be in close contact with the magnetic metal material, and the material constant (conductivity / permeability) is known. In addition, it is possible to avoid deterioration of the inspection accuracy when performing the inspection, and by directly calculating the signal level of the virtual crack depth signal equivalent to the signal level of the actual measurement signal from the crack using an electromagnetic analyzer. The crack depth can be accurately inspected.

  In addition, by accurately evaluating the amount of lift of the test coil, it is possible to correct a decrease in the reliability of the actual measurement signal and accurately inspect the crack depth in the metal material.

  FIG. 16 shows a sixth example of the crack depth inspection method for a metal material according to the present invention.

  The test coil 5 is in close contact with the surface of the magnetic metal material 31 that does not include the relatively flat crack 33 in the vicinity of the crack 33 of the magnetic metal material 31.

  In FIG. 16, the same members as those shown in FIG.

  FIG. 17 is a flowchart showing an eighth embodiment of a crack depth inspection method for a metal material.

  The flowchart in FIG. 17 is a flowchart for determining an unknown material constant (conductivity / magnetic permeability) for the magnetic metal material 31 as a metal material as shown in FIG. This is applied when the material constant of the magnetic material to be inspected is unknown, and is performed prior to any one of the flowcharts of FIGS.

  First, a current is supplied from the power source inside the computer 22, and a magnetic flux is generated from the exciting coil of the test coil 25 (S71).

  Next, a leakage magnetic flux is induced in the surface layer portion of the magnetic metal material 31 by this magnetic flux, and the leakage magnetic flux is disturbed by the presence of the crack 33. The disturbance of the leakage magnetic flux is detected by the detector of the test coil 25, and the detected value is measured as an actual measurement signal (impedance and output voltage) (S72). Further, the obtained actual measurement signal is stored in the computer 22 (S73).

  Further, an electromagnetic material constant database is input to the computer 22 and, in addition, magnetic permeability = β (for example, β = 1) and arbitrarily set conductivity (virtual conductivity) are input (S74).

  Here, the electromagnetic material constant database is a material constant of a material to be inspected (here, a magnetic metal material), characteristics of an inspection object (here, a test coil), and a positional relationship between the inspection material and the inspection object (lifting amount, etc.) This is an aggregate of material constants for setting parameters necessary for electromagnetic analysis to arbitrary values.

  Next, when electromagnetic analysis is performed from the material constants in S74, a conductivity virtual signal corresponding to the virtual conductivity is calculated (S75).

  Next, the signal level of the actual measurement signal and the signal level of the electrical conductivity virtual signal are compared with each other in the comparison unit inside the computer 22 (S76), and it is determined whether the signal level of the actual measurement signal and the signal level of the electrical conductivity virtual signal match (S76). S77).

  In the case of No in S77, that is, if the signal level of the actual measurement signal does not match the signal level of the conductivity virtual signal, only the virtual crack depth is changed (S74).

  In the case of Yes in S77, that is, if the signal level of the actual measurement signal matches the signal level of the conductivity virtual signal, the virtual conductivity used when the conductivity virtual signal is obtained by electromagnetic analysis is set as the obtained conductivity. (S78).

  Next, when S78 is obtained, it is determined whether or not there is a lifting amount H between the magnetic metal material 31 and the test coil 25 (S79).

  In the case of No in S79, that is, when the lifting amount H does not exist between the magnetic metal material 31 and the test coil 25, the material constant obtained in S78 is used to start the magnetic metal material 31 from S41 in FIG. The crack depth D is obtained.

  On the other hand, in the case of Yes in S79, that is, when the lifting amount H exists between the magnetic metal material 31 and the test coil 25, the material constant obtained in S78 is used to start from S50 of FIG. 14 or S60 of FIG. From this, the crack depth D of the magnetic metal material 31 is obtained.

  According to the flowchart of FIG. 17, when the material constant (conductivity / permeability) is unknown for the magnetic metal material, the difference in the material near the crack or the change in the material characteristics of the metal material in time series In order to cope with this, by obtaining the material constant directly from the material to be inspected, it is possible to correct the decrease in the reliability of the measured signal and to accurately inspect the crack depth in the metal material.

  In addition, the crack depth of the metal material can be accurately inspected by continuously performing FIG. 12, FIG. 14 or FIG. 15 from the material constant of the material to be inspected obtained in FIG.

The schematic of the eddy current flaw detector which inspects the crack depth using the eddy current flaw detection method. The figure which shows the 1st example of the crack depth inspection method of the metal material which concerns on this invention. The flowchart which shows 1st Embodiment of the crack depth inspection method of the metallic material which concerns on this invention. The figure which shows the 2nd example of the crack depth test | inspection method of the metal material which concerns on this invention. The flowchart which shows 2nd Embodiment of the crack depth inspection method of the metal material which concerns on this invention. The flowchart which shows 3rd Embodiment of the crack depth inspection method of the metal material which concerns on this invention. The correlation diagram which shows an example of the relationship between the amount of lifting of a test coil, and an eddy current output ratio. The figure which shows the 3rd example of the crack depth test | inspection method of the metal material which concerns on this invention. The flowchart which shows 4th Embodiment of the crack depth inspection method of the metal material which concerns on this invention. Schematic diagram of a leakage flux flaw detector that uses a leakage flux flaw detection method to inspect the crack depth. The figure which shows the 4th example of the crack depth test | inspection method of the metal material which concerns on this invention. The flowchart which shows 5th Embodiment of the crack depth inspection method of the metal material which concerns on this invention. The figure which shows the 5th example of the crack depth test | inspection method of the metal material which concerns on this invention. The flowchart which shows 6th Embodiment of the crack depth inspection method of the metal material which concerns on this invention. The flowchart which shows 7th Embodiment of the crack depth inspection method of the metal material which concerns on this invention. The figure which shows the 6th example of the crack depth inspection method of the metal material which concerns on this invention. The flowchart which shows 8th Embodiment of the crack depth inspection method of the metal material which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Eddy current flaw detector, 2 ... Computer, 3 ... Probe for flaw detection, 4 ... Connection cable, 11 ... Nonmagnetic metal material, 13 ... Crack, 15 ... Welding part, 21 ... Leakage magnetic flux flaw detector, 22 ... Computer, 23 DESCRIPTION OF SYMBOLS ... Probe for flaw detection, 24 ... Connection cable, 25 ... Test coil, 31 ... Magnetic metal material, 33 ... Crack, 35 ... Welded part, D ... Crack depth, H ... Lifting amount, S1, S11, S21, S31 , S41, S51, S61, S71 ... Magnetic flux generation S2, S12, S22, S32, S42, S52, S62, S72 ... Measurement of measured signals, S3, S13, S23, S33, S43, S53, S63, S73 ... Computer S4, S14, S24, S34, S44, S54, S64, S74 ... Electromagnetic analysis, S5, S15, S25, S35, S45, S55, S65, S7 ... Comparison, S6, S16, S26, S36, S46, S56, S66, S76 ... Judgment, S8, S18, S48, S58 ... Determination of crack depth, S39, S79 ... Judgment, S10, S20, S50, S60 ... Measurement of lifting amount, S30, S70 ... Creation of calibration curve.

Claims (8)

When inspecting the crack depth of a nonmagnetic metal material, an external magnetic field is applied from the crack surface of the nonmagnetic metal material, and the measurement is correlated with the magnitude of the eddy current disturbance induced in the crack surface layer. Obtaining a signal;
Performing electromagnetic analysis using known material constants of the non-magnetic metal material to obtain a crack depth virtual signal corresponding to the virtual crack depth;
The virtual crack depth is repeatedly scanned so that the signal level of the crack depth virtual signal approaches the signal level of the actual measurement signal to match both signal levels. A method for inspecting a crack depth of a metal material, comprising: obtaining a crack depth of the nonmagnetic metal material. When inspecting the crack depth of the non-magnetic metal material, if the shape of the crack surface is uneven, the test coil has a lift relative to the non-magnetic metal material. By creating a calibration curve that represents the eddy current output ratio induced when a magnetic field is applied from an arbitrary height in the vicinity, and calculating the eddy current output ratio by comparing the amount of lift with the calibration curve. The method for inspecting a crack depth of a metal material according to claim 1, wherein the amount of lift of the test coil is corrected. When inspecting the crack depth of a nonmagnetic metal material, if the material constant (conductivity / permeability) of the nonmagnetic metal material is unknown, a comparison that does not include a crack of the nonmagnetic metal material is required in advance. A step of applying an external magnetic field from a portion near the target flat crack to obtain an actual measurement signal having a correlation with the magnitude of eddy current disturbance induced in the surface portion of the nonmagnetic metal material;
Performing electromagnetic analysis using crack depth = 0 and permeability = α to obtain a conductivity virtual signal according to the virtual conductivity;
The virtual conductivity is repeatedly scanned so that the signal level of the electrical conductivity virtual signal approaches the signal level of the actual measurement signal to match both signal levels, and from the electrical conductivity virtual signal when they match, the nonmagnetic metal Obtaining a material constant of the material;
Applying an external magnetic field from the crack surface of the nonmagnetic metal material to obtain an actual measurement signal having a correlation with the magnitude of eddy current disturbance induced in the crack surface layer portion;
Performing electromagnetic analysis using the material constants to obtain a crack depth virtual signal corresponding to the virtual crack depth;
The virtual crack depth is repeatedly scanned so that the signal level of the crack depth virtual signal approaches the signal level of the actual measurement signal to match both signal levels. A method for inspecting a crack depth of a metal material, comprising: obtaining a crack depth of the nonmagnetic metal material. When inspecting the crack depth of the non-magnetic metal material, if the shape of the crack surface is uneven, the test coil has a lift relative to the non-magnetic metal material. By creating a calibration curve that represents the eddy current output ratio induced when a magnetic field is applied from an arbitrary height in the vicinity, and calculating the eddy current output ratio by comparing the amount of lift with the calibration curve. 4. The method for inspecting a crack depth of a metal material according to claim 3, wherein the amount of lift of the test coil is corrected. When inspecting the crack depth of the magnetic metal material, an external magnetic field is applied from the crack surface of the magnetic metal material to detect the leakage magnetic flux disturbance induced in the crack surface layer of the magnetic metal material. Obtaining an actual measurement signal with
Performing electromagnetic analysis using material constants of the magnetic metal material to obtain a crack depth virtual signal corresponding to the virtual crack depth;
The virtual crack depth is repeatedly scanned so that the signal level of the crack depth virtual signal approaches the signal level of the actual measurement signal to match both signal levels. A method for inspecting the crack depth of a metal material, comprising: obtaining a crack depth of the magnetic metal material. When inspecting the crack depth of the magnetic metal material, if the shape of the crack surface is uneven, the test coil has a lift relative to the magnetic metal material, so the crack vicinity does not include a crack. In this test coil, a calibration curve representing the leakage flux output ratio induced when a magnetic field is applied from an arbitrary height is created, and the leakage flux output ratio is obtained by comparing the amount of lifting with the calibration curve. 6. The method for inspecting a crack depth of a metal material according to claim 5, wherein an amount of the lift of the metal material is corrected. When inspecting the crack depth of a magnetic metal material, if the material constant (conductivity / permeability) of the magnetic metal material is unknown, it should be a relatively flat plate that does not contain a crack of the magnetic metal material. Applying an external magnetic field from a portion near the crack to obtain an actual measurement signal having a correlation with the magnitude of the leakage magnetic flux disturbance induced in the magnetic metal material surface layer portion;
Performing an electromagnetic analysis using crack depth = 0 and permeability = β to obtain a conductivity virtual signal according to the virtual conductivity;
The virtual conductivity is repeatedly scanned so that the signal level of the conductivity virtual signal approaches the signal level of the actual measurement signal to match both signal levels, and from the conductivity virtual signal when they match, the magnetic metal material Obtaining a material constant of
Applying an external magnetic field from the crack surface of the magnetic metal material to obtain an actual measurement signal having a correlation with the magnitude of disturbance of leakage magnetic flux induced in the crack surface layer portion;
Performing electromagnetic analysis using the material constants to obtain a crack depth virtual signal corresponding to the virtual crack depth;
The virtual crack depth is repeatedly scanned so that the signal level of the crack depth virtual signal approaches the signal level of the actual measurement signal to match both signal levels. A method for inspecting a crack depth of a metal material, comprising: obtaining a crack depth of the magnetic metal material. When inspecting the crack depth of the magnetic metal material, if the shape of the crack surface is uneven, the test coil has a lift relative to the magnetic metal material, so the crack vicinity does not include a crack. In this test coil, a calibration curve representing the leakage flux output ratio induced when a magnetic field is applied from an arbitrary height is created, and the leakage flux output ratio is obtained by comparing the amount of lifting with the calibration curve. The method for inspecting the crack depth of a metal material according to claim 7, wherein the amount of lifting is corrected.

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