JP2002039932A - Method and apparatus for diagnosis of durability of metal component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for the diagnosis of the durability of a metal component, where the durability of a work under test can be diagnosed easily and quickly and the durable load of the work under test can be estimated easily. SOLUTION: This method includes a process where the work under test 8 is loaded repeatedly with a load and a magnetometric sensor 12 is scanned so as to measure electromagnetic parameter is performed; a step wherein a part whose electromagnetic parameter is maximum is specified as a maximum stress concentration part is performed; a step where the magnetometric sensor 12 is situated in the maximum stress concentration part, the work 8 is loaded repeatedly with the load, while the load is being increased at prescribed intervals from P1 to P2 and the mechanical Barkhausen noise of the electromagnetic parameter is measured by the magnetometric sensor 12 is performed; a step where the load which can obtain the maximum value of the mechanical Barkhausen noise is estimated as the durable load Pw is performed; and a durable load Pw is compared with a design allowable load Pt, and the durability of the work 8 is diagnosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a durability diagnostic method and a durability diagnostic apparatus capable of determining the fatigue durability of a ferromagnetic metal component without destroying the metal component.

[0002]

2. Description of the Related Art In the development stage of a new component, it is indispensable at the development stage to diagnose the durability of the component to determine whether or not the component sufficiently satisfies a desired design allowable load (design allowable load). It is. There are two types of durability diagnostic methods: destructive testing and nondestructive testing.

In a conventional destructive inspection method, a prototype component in a development stage is used as a test object, and the above design allowable load is repeatedly applied to the test object a predetermined number of times to observe whether or not a fatigue crack is observed. If fatigue cracks are found, the design is rejected as rejected, and if not found, the design is accepted.

[0004] Conventional nondestructive inspection methods include an X-ray diffraction method and an electromagnetic method. In the X-ray diffraction method, durability is diagnosed by measuring a change in an X-ray diffraction profile of a part to which a load is repeatedly applied and estimating the damage degree from a damage degree obtained in advance and a test line of the profile change. In the electromagnetic method, a test object is deteriorated under predetermined conditions under a predetermined condition, a magnetic field is applied from the outside, and an electromagnetic signal generated thereby is measured for each time-dependent deterioration.

[0005]

However, the above conventional durability diagnosis method has the following problems. That is, in the above-described destructive inspection method, since a predetermined number of repetitive loads is indispensable, the period until the durability is diagnosed is very long. For example, when a test is performed with the number of repetitions set to 1 × 10 7 times and the repetition rate 5 set to Hz, and then the presence or absence of a crack is determined by color check, it takes about one month. Therefore, the cost is high. Furthermore, in this method, it cannot be determined at all whether the quality of the acceptable product is excessive quality, and it is difficult to achieve an optimal design.

Further, in the X-ray diffraction method of the nondestructive inspection method, an apparatus for performing X-ray diffraction becomes very large,
Inspection at the development site of metal parts is difficult. In addition, the inspection result is easily influenced by the cleanliness of the outermost surface of the test object and other conditions. In the above electromagnetic method,
Excitation is performed externally, but the absolute value of the parameter that can be measured by this method is not reliable because the absolute value of the parameter is strongly affected by the shape of the DUT. For this reason, the change with time of the parameter due to the deterioration of the test object is measured, and the durability is estimated from the change. Therefore, the period until the determination of the durability becomes longer. In addition, since the value of the durability limit cannot be estimated, it is difficult to lead to an optimal design.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and makes it possible to easily and quickly diagnose the durability of a test object and easily estimate the durability load of the test object.
An object of the present invention is to provide a durability diagnosis method and a durability diagnosis device for metal parts.

[0008]

According to the first aspect of the present invention, there is provided a method for diagnosing the durability of a ferromagnetic metal part. The method comprises the steps of: An electromagnetic parameter measuring step of measuring an electromagnetic parameter by scanning a magnetic sensor in the vicinity of the surface of the test piece; a stress concentration section identifying step of identifying a portion where the electromagnetic parameter is maximum as a maximum stress concentration section; With the magnetic sensor positioned in the section, a desired design allowable load P
from the minimum load P1 lower than t to the design allowable load P
a mechanical Barkhausen noise measuring step of repeatedly applying a load while increasing the load at predetermined intervals up to a maximum load P2 higher than t, and measuring a mechanical Barkhausen noise of an electromagnetic parameter by a magnetic sensor for each load; Performing a durable load estimating step of estimating a load at which the maximum value of the mechanical Barkhausen noise is obtained as a durable load Pw, and comparing the durable load Pw with the design allowable load Pt to determine the durability of the test object. A method for diagnosing the durability of a metal part, characterized by performing a diagnosis.

The most notable point of the present invention is that the maximum stress concentration portion is specified by performing the electromagnetic parameter measuring step and the stress concentration portion specifying step, and thereafter, the mechanical bulk is applied to the maximum stress concentration portion. Performing the Hausen noise measuring process and the durable load estimating process to obtain the durable load Pw
Is estimated, and the durability of the test object is diagnosed by comparing the endurable load Pw with the design allowable load Pt.

In the present invention, first, the electromagnetic parameter measuring step is performed. In this process, as described above,
A magnetic sensor is used. This magnetic sensor is a sensor capable of measuring magnetism generated from a device under test in the vicinity of the surface of the device as an electromagnetic parameter (for example, voltage output). For example, there is an electromagnetic induction type magnetic sensor.
Then, in this step, scanning is performed by the magnetic sensor in a state in which the test object is repeatedly loaded with a constant load. As a result, electromagnetic parameters corresponding to the part of the test object are obtained.

The electromagnetic parameters correspond to the magnitude of the stress applied to the test object by the repetitive load. Therefore, by specifying a portion where the electromagnetic parameter is maximum in the stress concentration portion specifying step, the maximum stress concentration portion in the test object is specified. The maximum stress concentration site is a site serving as a fracture starting point.

In the mechanical Barkhausen noise measuring step, the magnetic sensor is positioned in a stationary state with respect to the maximum stress concentration portion, and a load is repeatedly applied to the test object again. The repetitive load at this time is
As described above, from the minimum load P1 lower than the design allowable load Pt to the maximum load P higher than the design allowable load Pt.
It is applied while increasing at predetermined intervals up to 2. The magnetic sensor measures the mechanical Barkhausen noise of the electromagnetic parameter for each load.

The mechanical Barkhausen noise of the electromagnetic parameter is a high-frequency signal that is superimposed on the electromagnetic parameter. This mechanical Barkhausen noise corresponds to a strain component in a test object to which a load is repeatedly applied. That is, when a stress is applied to a ferromagnetic material, a magnetic domain structure changes due to a magnetostrictive effect. When the domain wall moves discontinuously in the process, the mechanical Barkhausen noise is generated.

What is important here is that when the load is repeatedly applied to the test object while the mechanical load is gradually increased, and the mechanical Barkhausen noise is measured for each load, this value increases as the load increases. Eventually, it was found that a phenomenon occurs in which a maximum value (peak) appears and then decreases, and that a durability limit of fatigue fracture exists near a load value at which the maximum value occurs. Therefore, in the present invention, the mechanical Barkhausen noise is measured in the above-described mechanical Barkhausen noise measurement step, and the load at which the maximum value is obtained in the subsequent durable load estimation step is estimated as the durable load Pw.

However, the appearance of this maximum value is caused by the above P1
It may not appear when the repetitive load up to P2 is applied only for one cycle, and may appear when the repetitive load from P1 to P2 in a plurality of cycles is applied. Therefore, as described later, it is preferable to repeat the mechanical Barkhausen noise measurement step a plurality of times to generate a stable peak, and then proceed to the endurance load estimation step.

If the values of the minimum load P1 and the maximum load P2 are inappropriate, the maximum value may not appear between them. In this case, it is preferable to review the values of P1 and P2. However, if it is only necessary to simply determine whether the durability limit is higher or lower than the design allowable load Pt, the determination may be made under the condition of P2 = Pt. That is, if no maximum point is recognized between P1 and Pt, the durability limit can be determined to be higher than Pt, and if a maximum point is recognized, the durability limit can be determined to be lower than Pt.

In the present invention, the durable load Pw estimated in the durable load estimating step is replaced by the design allowable load Pw.
The durability of the test object is diagnosed in comparison with t. The diagnosis is performed by, for example, a method of determining whether or not the endurable load Pw exceeds the design allowable load Pt, a method of determining whether or not the endurance is determined in consideration of the safety factor, or a method of determining the endurance load Pw.
When w is higher than a predetermined value, various determination methods such as a method of determining that the quality is excessive can be performed.

Next, the operation and effect of the present invention will be described.
In the present invention, as described above, the maximum stress concentration portion is specified by performing the electromagnetic parameter measuring step and the stress concentration portion specifying step. Therefore, the maximum stress concentration portion can be specified accurately by scanning the magnetic sensor once in the vicinity of the surface of the test object in a very short time.

Further, the estimation of the durable load Pw in the mechanical Barkhausen noise measuring step and the durable load estimating step can be accurately performed in a short time by obtaining the maximum value of the mechanical Barkhausen noise.
Furthermore, the above-mentioned electromagnetic parameter measurement step and mechanical Barkhausen noise measurement step can be performed using a magnetic sensor, and a large-scale apparatus such as an X-ray diffraction apparatus is not required.

Further, since the endurable load Pw can be easily estimated, it is possible to determine whether or not the quality is excessive as described above, which can lead to an optimal design of a metal part.

As described above, according to the present invention, there is provided a method for diagnosing the durability of a metal part, which can easily and quickly diagnose the durability of the DUT and can easily estimate the durable load of the DUT. can do. The use of this durability diagnosis method can shorten the development period and cost of new metal parts.

Next, the mechanical Barkhausen noise measuring step is performed a plurality of times, and the maximum value in the last mechanical Barkhausen noise measuring step is determined in the endurance load estimating step. It is preferable to estimate it as the durable load Pw. In this case, the reliability of the maximum value is increased, and the reliability of the estimated endurance load Pw can be improved.

Next, a third aspect of the present invention is an apparatus for diagnosing the durability of a ferromagnetic metal component, comprising: a load applying means for repeatedly applying a load to a test object made of the metal component; A magnetic sensor for measuring an electromagnetic parameter in the vicinity of the surface of a test body, a mechanical Barkhausen noise output means for analyzing an electromagnetic parameter obtained from the magnetic sensor to obtain a mechanical Barkhausen noise, the electromagnetic parameter and the mechanical Barkhausen noise And a general control means for taking in the data and outputting it to an output means.

The most remarkable point in the present invention is that it has the load applying means, the magnetic sensor, the mechanical Barkhausen noise output means, the output means, and the general control means. By having these, the diagnostic apparatus of the present invention can implement the above excellent diagnostic method.

That is, the load applying means applies a repetitive load to the specimen under a constant load, scans the magnetic sensor to measure the electromagnetic parameters, and outputs the electromagnetic parameters to, for example, a display. Output to printer etc.
Next, with the magnetic sensor set at a position where the obtained electromagnetic parameter is the maximum, the load applying means applies a desired design allowable load Pt to the device under test.
From the minimum load P1 lower than the design allowable load Pt
The load is repeatedly applied while gradually increasing the load to a maximum load P2 higher than the maximum load P2. The magnetic sensor measures electromagnetic parameters for each load, and the mechanical Barkhausen noise output means obtains mechanical Barkhausen noise. This mechanical Barkhausen noise is also output to a display, a printer or the like by the output means.

Thus, the maximum value of the obtained mechanical Barkhausen noise can be specified. In addition,
As described above, when the maximum value does not occur, the measurement of the mechanical Barkhausen noise can be repeated a plurality of times. Then, by estimating the load at which the maximum value of the mechanical Barkhausen noise is obtained as the durable load Pw, the durable load Pw can be estimated. Therefore, based on the durability load Pw, the durability of the metal component can be diagnosed by various methods.

As described above, by using the present diagnostic apparatus, the above excellent diagnostic method can be easily implemented, the durability of the DUT can be easily and quickly diagnosed, and the durable load of the DUT can be improved. Can be easily estimated. The use of the durability diagnostic apparatus can shorten the development period of new metal parts and reduce costs.

According to a fourth aspect of the present invention, the durability diagnostic device includes a sensor moving device for moving or fixing the magnetic sensor and a load control device for controlling the load applying means. It is preferable that the sensor moving device and the load control device are configured to be controlled by the comprehensive control means. In this case, for example, scanning or fixing of the magnetic sensor, setting and changing of the load condition of the repetitive load, and the like can be easily and accurately performed by the instruction of the comprehensive control means.

Further, by inputting the design allowable load Pt, the minimum load P1, the maximum load P2, and the like to the general control means, the respective steps of the durability diagnosis method described above are automatically advanced. It is also possible to do.
Therefore, the operation for determining the durability can be simplified.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A durability diagnosis method and a durability diagnosis apparatus for metal parts according to an embodiment of the present invention will be described with reference to FIGS. In this example, the metal part 8 for diagnosing durability is shown in FIG.
This is an automobile part having a shape as shown in FIG. The metal component 8 is a component that receives a repeated load for a long period of time, and its durability is a problem.

As shown in FIG. 1, the diagnostic device 1 for diagnosing the durability of the metal component (test object) 8 includes a load applying means 11 for repeatedly applying a load to the test object 8, A magnetic sensor 12 for measuring an electromagnetic parameter near the surface, a mechanical Barkhausen noise output means 15 for analyzing the electromagnetic parameter obtained from the magnetic sensor 12 to obtain a mechanical Barkhausen noise, and taking in the electromagnetic parameter and the mechanical Barkhausen noise Control means 1 for outputting to output means 17 by means of
6.

As the magnetic sensor 12, an electromagnetic induction sensor was used, and a sensor capable of obtaining a voltage output as an electromagnetic parameter was used. The magnetic sensor 12 was connected to the mechanical Barkhausen noise output means 15 composed of an FFT analyzer via an amplifier 13 and a filter 14. Further, it was connected to a general control means 16 comprising a personal computer. As the output device 17, a display and a printer of the personal computer were used. As an output method of this example, an electromagnetic parameter or mechanical Barkhausen noise is plotted on a chart with a horizontal axis representing a time axis.

As the load applying means 11, a conventional durability tester was used. In this example, as shown in FIG. 2, the fixed part 81 was fixed to the load applying means 11, and the test piece 8 was set so that the load (P) was repeatedly applied from the tip 82.

Next, the magnetic sensor 12 is set so that it can be scanned on the surface of the test object 8 and a constant load (in this example, design allowable load Pt = 3200 N in this example) is applied to the test object 8 by the load applying means 11. Was loaded. Then, an electromagnetic parameter measuring step of measuring the electromagnetic parameters by scanning the magnetic sensor 12 near the surface of the test object 8 was performed.

FIG. 3 shows an example of the output state of the electromagnetic parameters obtained from the magnetic sensor 12. The horizontal axis represents time (ms), the left vertical axis represents voltage output (Induced voltage, V) as an electromagnetic parameter, and its value Vp
Is plotted as a solid line. In the same figure, the load fluctuation (Stress signal, V) of the repeated load is plotted on the right vertical axis, and the load fluctuation S taken in from the load cell output of the load load means 11 is plotted by a broken line.

A brief explanation of mechanical Barkhausen noise, which will be described later, with reference to this figure, shows that a high-frequency signal that fluctuates up and down is on the electromagnetic parameter Vp. This signal is mechanical Barkhausen noise. Therefore, the mechanical Barkhausen noise can be measured by removing the low frequency components from the electromagnetic parameter signal.

In the electromagnetic parameter measuring step, the electromagnetic parameters obtained from the magnetic sensor 11 are passed through the filter 14 and the mechanical Barkhausen noise output means 15 to the general control means 16, and output from the output means 17. . In the present example, while observing this output, a mark is made on the surface of the device under test 8 where the magnetic sensor 11 is located when the electromagnetic parameter is maximized, thereby finding a portion where the electromagnetic parameter is maximized. The part was specified as the maximum stress concentration part (stress concentration part specification step).

In this embodiment, the relationship between the applied load P and the stress σ at the maximum stress concentration portion is as follows. σ = (Pl / Z) × α 1: distance between maximum stressed part and load part, Z: section modulus, α:
Shape factor Actually, the functions of σ and P are as follows. P = 12.8 × σ

Next, in a state where the magnetic sensor is positioned at the maximum stress concentration portion, a minimum load P1 = 2180N lower than a desired design allowable load Pt is applied to the test piece 8.
(Σ = 175 MPa in the maximum stress portion) to a maximum load P2 = 5120 W (σ = 400 MPa in the maximum stress portion) higher than the design allowable load Pt. 12, a mechanical Barkhausen noise measuring step of measuring mechanical Barkhausen noise of an electromagnetic parameter for each load was performed.

As described above, the measured value of the mechanical Barkhausen noise is removed through the mechanical Barkhausen noise output means 15 including the magnetic sensor 12, the amplifier 13, the filter 14, and the FFT analyzer to remove low-frequency components and perform FFT processing (high-speed processing). Fourier transform) and 0.5
The effective value voltage generated in the region of -2.0 kHz was measured. This measured value was taken into the general control means 16 and output from the output means 17.

In this example, a clear mechanical Barkhausen noise maximal value did not appear with a one-cycle load change in the range of P1 to P2. Therefore, the above-described mechanical Barkhausen noise measurement process was repeated up to 16 times. FIG. 4 shows a graph of the result.
The figure shows the stress amplitude σa (Stress amplitude, MPa) applied to the specimen 8 from the repeated load applied to the horizontal axis.
And the vertical axis indicates the mechanical Barkhausen noise (Mec.BHN
voltaage, mV).

As shown in the figure, in this example, the maximum value stably appeared by repeating the above-described mechanical Barkhausen noise measurement process. In this example, in the endurance load estimation step, the stress amplitude σam at which the last 16th maximum value is obtained is estimated as the endurance load Pw.

As a result, the durable load Pw in this example is:
4350N (σ = 340 Mpa at the maximum stress portion,
It can be diagnosed that the durability is much higher than the design permissible load Pt of 3200 N, and the durability is good. Further, it was found that the safety factor of the endurance load Pw was 1.36, and it was not particularly excessive quality and no design change was required. If the durable load Pw is further increased, the design can be changed so that the durable load Pw is slightly reduced from the viewpoint of weight reduction of parts. If the endurable load Pw is smaller than the design allowable load Pt,
We will proceed with design changes to improve this.

As described above, in this example, the test object 8
The durability of the test piece can be easily and quickly diagnosed, and
Can be easily estimated. As a result, it is possible to shorten the development period and cost of new metal parts.

Embodiment 2 In this embodiment, as shown in FIG. 5, the durability diagnostic device 1 includes a sensor moving device 121 for moving or fixing the magnetic sensor 12 and a load control device for controlling the load applying means 11. 111. The sensor moving device 121 and the load control device 111 are configured to be controlled by the general control means 16.

The integrated control means 16 is configured to take in the control information such as the position information of the magnetic sensor 12 and the load condition of the load applying means 11. The integrated control means 16 includes a design allowable load Pt and a minimum load load Pt.
1, the maximum load P2 is input in advance, and the electromagnetic parameter measuring step, the stress concentration portion specifying step,
The mechanical Barkhausen noise measurement process and the endurance load estimation process are automatically performed.

That is, the test object 8 is connected to the load applying means 11.
, And controlled by the general control means 16 to
An electromagnetic parameter measuring step of applying a repetitive load of a fixed value (design allowable load Pt) to the test object 8 from the load applying means 11 and scanning the magnetic sensor 12 near the surface to measure an electromagnetic parameter is performed. The measured electromagnetic parameters are taken into the general control means 16 together with the position information of the magnetic sensor 12.

After the scanning of the magnetic sensor 12 is completed,
The integrated control means 16 performs a stress concentration portion specifying step of specifying the position of the magnetic sensor 12 at which the electromagnetic parameter has the maximum value, and specifying the position of the test object 8 corresponding to this position as the maximum stress concentration portion.

Next, the integrated control means 16 moves and fixes the magnetic sensor 12 to the specified maximum stress concentration portion. Then, the comprehensive control means 16 includes the load applying means 1.
1 is controlled in advance to P
The load is repeatedly applied while increasing the load at predetermined intervals from 1 to P2. Then, a mechanical Barkhausen noise measuring step of measuring the mechanical Barkhausen noise of the electromagnetic parameter for each load by the magnetic sensor 12 is performed.

After the completion of the mechanical Barkhausen noise measurement step, the integrated control means 16 determines whether or not there is a maximum value of the mechanical Barkhausen noise, and if not, repeats the mechanical Barkhausen noise measurement step again. Control. Then, the comprehensive control means 16 performs a durable load estimation step of estimating a load at which a maximum value is obtained in the mechanical Barkhausen noise measurement step as a durable load Pw.

Next, the comprehensive control means 16 diagnoses the durability of the test object by comparing the obtained durable load Pw with the design allowable load Pt. In this example, when the durable load Pw is larger than the design allowable load Pt, it is judged as pass, and in other cases, it is rejected and it is judged that the design change is necessary, and this is output. Other configurations are the same as those of the first embodiment.

As described above, in the case of the present embodiment, the operation of the durability judgment can be simplified by adding various automatic control means to the durability diagnostic apparatus 1 of the first embodiment. it can. Otherwise, the same operation and effect as those of the first embodiment can be obtained.

Embodiment 3 In this embodiment, steel parts of a plurality of types of materials were prepared using the same apparatus and method as in Embodiment 1, and their durability was diagnosed. Then, the reliability of the obtained endurance load Pw was verified.

The prepared components (test pieces) are the same as the medium-carbon steel S55C tempered material (E1) of the first embodiment, as well as the S15C annealed material (E2) and the S15C normalized material (E3). And S55C normalizing material (E4) were prepared. Each of these shapes had the same shape as that of the first embodiment.

The reliability of the durability load Pw obtained by executing the same durability diagnosis method as that of the first embodiment was verified by comparing it with the actual durability limit. The actual endurance limit is JIS
It was determined by a plane drawing fatigue test with a stress ratio R (ratio of maximum stress to minimum stress) = -1 according to Z2275.

FIG. 6 shows the relationship between the actual endurance limit and the estimated endurance load Pw. In the figure, the horizontal axis represents the actual durability limit σw (MPa), and the vertical axis represents the stress amplitude value σ of the durability load Pw.
am (MPa). As is known from the figure, the stress amplitude value σam of each estimated endurance load Pw
Is within ± 10% of the actual endurance limit, which proved to be extremely reliable.

[0057]

As described above, according to the present invention, a method for diagnosing the durability of a metal part can easily and quickly diagnose the durability of the DUT and easily estimate the durable load of the DUT. And a durability diagnostic apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a durability diagnostic apparatus according to a first embodiment.

FIG. 2 is an explanatory diagram showing an appearance of a test object in the first embodiment.

FIG. 3 is an explanatory diagram showing an output example of an electromagnetic parameter in the first embodiment.

FIG. 4 is an explanatory diagram showing measurement results of mechanical Barkhausen noise in the first embodiment.

FIG. 5 is an explanatory diagram illustrating a configuration of a durability diagnostic apparatus according to a second embodiment.

FIG. 6 is an explanatory diagram showing a relationship between an actual durability limit and a durability load Pw in a third embodiment.

[Explanation of Codes] . . 10. Durability diagnostic device, . . Loading means, 111. . . Load control device, 12. . . Magnetic sensor, 121. . . 12. Sensor moving device, . . Amplifier, 14. . . Filter, 15. . . 15. mechanical barkhausen noise output means; . . Comprehensive control means, 17. . . Output means,

Claims (4)

[Claims] 1. A method for diagnosing the durability of a ferromagnetic metal part, wherein a repetitive load of a constant load is applied to a test piece made of the metal part, and a magnetic sensor is provided near a surface of the test piece. An electromagnetic parameter measuring step of scanning and measuring an electromagnetic parameter; a stress concentration section identifying step of identifying a portion where the electromagnetic parameter is maximum as a maximum stress concentration section; and positioning the magnetic sensor at the maximum stress concentration section. In this state, while repeatedly increasing the load at predetermined intervals from the minimum load P1 lower than the desired design allowable load Pt to the maximum load P2 higher than the design allowable load Pt, the load is repeatedly applied to the test object. And a mechanical sensor that measures the mechanical Barkhausen noise of the electromagnetic parameter for each load with a magnetic sensor A Luckhausen noise measurement step and a durable load estimation step of estimating a load at which the maximum value of the mechanical Barkhausen noise is obtained as a durable load Pw are performed. By comparing the durable load Pw with the design allowable load Pt, A method for diagnosing the durability of a metal part, comprising diagnosing the durability of a test object. 2. The mechanical Barkhausen noise measurement step according to claim 1, wherein the mechanical Barkhausen noise measurement step is performed a plurality of times.
A method for diagnosing durability of a metal part, wherein the method is performed as w. 3. An apparatus for diagnosing the durability of a ferromagnetic metal part, comprising: a load applying means for repeatedly applying a load to a test piece made of the metal part; and an electromagnetic parameter near a surface of the test piece. A magnetic sensor for measuring
Mechanical barkhausen noise output means for analyzing the electromagnetic parameters obtained from the magnetic sensor to obtain mechanical barkhausen noise; and comprehensive control means for taking in the electromagnetic parameters and the mechanical barkhausen noise and outputting to the output means. A durability diagnostic apparatus for metal parts characterized by the following. 4. The durability diagnostic apparatus according to claim 3, further comprising: a sensor moving device for moving or fixing the magnetic sensor; and a load control device for controlling the load applying means. The said load control apparatus is comprised so that it may be controlled by the said general control means, The durability diagnostic apparatus of a metal part characterized by the above-mentioned.