JPH06308092A - Material deterioration inspection device - Google Patents

Abstract

PURPOSE:To inspect a specimen of a non-magnetic material which cannot be measured easily by measuring fatigue damage non-destructively without any contact. CONSTITUTION:The title device consists of an excitation part 2 for applying alternate magnetic field to a specimen 1 to be inspected by an excitation coil, a sensor part 3 consisting of a flux gate flux meter for detecting a small magnetic field generated in the specimen 1 to be inspected at the excitation part 2, a computer group 6 for judging the degree of fatigue damage of a material according to the data base indicating the relationship with the fatigue damage and then displaying the output result, and a measurement control device 7 for controlling excitation etc. For example, the degree of fatigue damage can be inspected non-destructively without any contact by capturing, with the flux crate flux meter, the magnetic properties generated by turning the degree of fatigue of the specimen to be inspected made of, for example, austenite steel into martensite by fatigue.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material deterioration inspection apparatus, and more particularly, to deterioration and damage caused to a specimen made of a non-magnetic material such as austenitic stainless steel or nickel-based alloy which is used under repeated stress. In particular, the present invention relates to a material deterioration inspection device capable of detecting fatigue damage.

[0002]

2. Description of the Related Art In a device / member (hereinafter referred to as an object to be inspected) that is used under repeated stress, stress acts on a discontinuity of shape or a stress concentration part, causing deterioration / damage due to fatigue. It is known.

Conventionally, as a method of inspecting a subject for fatigue damage, a hardness method and a method utilizing X-rays are known. In these inspection methods, the applicable inspection site is limited to the flat part,
In particular, it was difficult to apply it to complicated shapes and parts.

Further, a method of utilizing a change in magnetic properties of a material as a means of nondestructive inspection is disclosed in, for example, Japanese Patent Laid-Open No. 59-112.
No. 257 is disclosed.

[0005]

However, the conventional technique is a method of detecting an AE signal of an elastic wave generated in a magnetization process when a magnetic field is applied to an object made of a ferromagnetic material. It is only to associate the stress acting on the test object and the residual stress during manufacturing with the measured value,
The evaluation by fatigue damage is not performed qualitatively.

[0006] As described above, the conventional method of inspecting fatigue damage applying magnetism is used in the case of measuring and evaluating the fatigue damage generated in the subject composed of the ferromagnetic material used under repeated stress. Is suitable, but there is a difficult problem in measuring the degree of deterioration damage of a nonmagnetic material sample.

The present invention has been made in order to solve the above problems, and measures fatigue damage by a non-contact and non-destructive means with respect to an object of a non-magnetic material which is conventionally difficult to inspect. The purpose of the present invention is to provide a material deterioration inspection device that can inspect.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an exciting device for applying an alternating magnetic field to an object made of a non-magnetic material, a sensor section for detecting a minute magnetic field generated in the object by the exciting apparatus, and this sensor section. A non-contact holding mechanism with respect to the subject, a signal processing device for signal processing the detection signal of the sensor unit, a change in the characteristic value of the minute magnetic field previously obtained with a test material and the subject It comprises a deterioration degree judging means for judging the fatigue damage degree of the subject from a master curve showing a relationship with the fatigue damage degree and a display means for displaying the results thereof, and the sensor part is of an exciting coil by reverse excitation. It is characterized by comprising a fluxgate magnetometer capable of measuring the magnetic field in a state where the influence of the magnetic field on the sensor unit is canceled.

[0009]

According to the present invention, the degree of fatigue damage of a subject is inspected by measuring the change in the magnetic characteristics of the subject that changes with the fatigue damage of the non-magnetic material. That is, by imparting fatigue damage to a non-magnetic material specimen, the structure of the fatigue damage part transforms from a non-magnetic austenite phase to a magnetic martensite phase, and fatigue damage is exploited by having a minute magnetic field. Check the degree.

A minute magnetic field generated when an alternating magnetic field is applied to a subject by an exciting coil or the like is detected by a fluxgate magnetometer. The detected magnetic signal is processed by signal processing and arithmetic processing, and the change of the magnetic signal and the degree of deterioration / damage of the test object, which are obtained in advance by measurement and analysis using a test material,
That is, the fatigue damage degree of the subject is determined by the arithmetic processing device from the database representing the relationship with the fatigue damage degree, and various output results such as the arithmetic processing result and the deterioration degree determination result are displayed.

Here, a predetermined alternating magnetic field is applied to the subject,
Using a control means and a means for detecting a minute magnetic field generated when a magnetic field is applied, converting the obtained signal into a voltage signal, and processing the signal, a test material whose fatigue damage degree is known in advance is used. Measured using the obtained magnetic field signal, the characteristic value obtained by signal processing, for example, the relationship between the position and magnitude of the magnetic moment and the degree of fatigue damage is obtained, and the deterioration is evaluated as the deterioration evaluation curve (master curve) of the test material. Stored in the evaluation section. In the deterioration measurement of the subject, the degree of fatigue damage is detected by collating the measurement data of the subject with the deterioration degree evaluation curve.

A measuring head constituted by integrating an exciting unit and a sensor unit is properly installed at a predetermined position of a subject by a measuring head holding mechanism and an operating mechanism, and can be moved under appropriate conditions. The position information is displayed on a display or transmitted to a computer group such as a signal processing unit.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the material deterioration inspection apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a block system diagram showing an example of the configuration of a material deterioration detecting device according to the present invention.

The main constituent parts are an exciting part 2 for exciting a subject 1 made of, for example, an austenitic stainless steel non-magnetic material that has been damaged by fatigue, and a sensor part composed of a fluxgate magnetometer and an exciting magnetic field canceling coil. Three
A drive system 4 for positioning and moving the sensor unit 3, an excitation power source 5 connected to the excitation unit 2, and a sensor unit 3
On the other hand, a measurement control device 7 for controlling sensor signal recording, a signal processing device for processing the magnetic field intensity signal by the computer group 6, and excitation.

In the subject 1, that is, the metal material, the metal structure changes due to the repeated load of stress and the repeated heat load, and the strength of the material decreases. Inside the material, dislocations grow and the dislocation density increases with repeated loading.

On the other hand, a small crack is generated on the surface of the material.
Grows, these cracks connect and coalesce with adjacent cracks,
It becomes the main crack and reaches the final fracture. When an alternating magnetic field is applied to a fatigue-damaged subject, the damaged part transforms from the austenite phase to the martensite phase. The minute magnetic field on the surface of the subject generated by this is detected, and the characteristic value obtained by the signal processing device of this detection signal, for example, the magnitude of the magnetic moment is arithmetically processed.

The computer group 6 as a signal processing device is composed of a computer for processing the magnetic field intensity from the exciting magnetic field and the fluxgate magnetometer to calculate the magnitude of magnetic moment and position information, and cancels external geomagnetism and the like. The current for doing this can also be controlled.

In order to obtain the fatigue damage degree of the object from the magnetic moment obtained by signal processing, a deterioration degree evaluation curve (master curve) created from a measurement database previously obtained from a test material with a known fatigue damage degree And the deterioration degree is determined and evaluated.

The determination result is stored in the computer group 6 as data. The sensor unit 3 can be scanned by a drive system 4 at a predetermined position of a measurement site, and its control can be performed by a computer group 6.

The exciting unit 2 applies a magnetic field to the ferromagnetic phase (in this case, the martensite phase) in the subject 1 so that the magnetic moment of the ferromagnetic phase is aligned with the direction of the magnetic field and can be detected outside. Therefore, it is composed of a solenoid coil and the like.

The fluxgate magnetometer formed as a part of the sensor unit 3 has a first core 8 and a second core 8 which are excited by an AC magnetic field power source 10 as shown in FIG. 2A.
Core 9 is "0" if the saturation point on the AC time axis is non-magnetic due to reverse excitation due to an external magnetic field, but it changes when magnetized and the data is captured as magnetic field strength. . Note that FIG. 2B shows the relationship between the magnetic flux density and the magnetic field strength in FIG.

An excitation canceling coil is placed around the fluxgate magnetometer, and the magnetic field is measured while the influence of the magnetic field of the exciting coil on the sensor unit 3 is canceled.

Next, the metallic material sample 1 which is the principle of the present invention
The relationship between the degree of fatigue damage and the magnetic field strength obtained by the sensor unit will be described with reference to FIG. INDUSTRIAL APPLICABILITY The present invention relates to the generation of a magnetic field, that is, the influence of the magnitude of this magnetic field strength due to excitation, with respect to the metallurgical structure change accompanying fatigue damage of austenitic stainless steel or austenitic nickel-based alloy which is a non-magnetic material Is paying attention to.

In general, when a metallic material is subjected to fatigue, dislocations multiply inside the material, the generation and increase of slip lines occur in the crystal grains, the metal structure of the damaged portion changes from the austenite phase to the martensite phase, and the magnetism changes. Take on.

FIG. 3 shows an example in which an austenitic stainless steel (SUS304) is subjected to a fatigue test under strain control and the fatigue test piece is used as an object to be measured (inspected) by the material deterioration inspection apparatus of the present invention.

In FIG. 3, the horizontal axis represents the number of repetitions when the fatigue test is stopped halfway through the fatigue test in the fatigue test at 1.2 × 10 ⁵ cycles, and the vertical axis represents the measured magnetic field strength (magnetic flux density). It was organized in. It can be seen from FIG. 3 that the measured magnetic field strength increases as the fatigue damage degree increases.

The present invention can be applied by appropriately changing the shape and size of the measuring head, so that the non-magnetic material is a non-magnetic material regardless of the composition of the metal material, and the shape of the measuring portion is a curved surface, a flat surface, or the like. With respect to the above structure, it is possible to measure the degree of fatigue damage at the measurement site by using the above method and apparatus.

Further, the detection sensor used in the present invention is non-contact, and has the effect of being able to measure the degree of deterioration of the measurement site regardless of the surface condition of the measurement site.

[0029]

According to the present invention, it is possible to inspect and evaluate the fatigue damage degree of a non-magnetic material specimen used under repeated stresses in a non-contact and non-destructive manner.
It is possible to ensure the soundness and safety of equipment and members.

[Brief description of drawings]

FIG. 1 is a block system diagram showing an embodiment of a material deterioration inspection device of the present invention.

2A is a configuration diagram for explaining the principle of the sensor unit in FIG. 1, and FIG. 2B is a characteristic diagram showing the relationship between the magnetic flux density and the magnetic field strength in FIG.

3 is a characteristic diagram showing a change in magnetic field strength during a fatigue process when an object is inspected by the material deterioration inspection apparatus according to FIG.

[Explanation of symbols]

1 ... Subject, 2 ... Excitation part, 3 ... Sensor part, 4 ... Driving system,
5 ... Excitation power supply, 6 ... Computer group (signal processing unit), 7
... Measurement control device, 8 ... First core, 9 ... Second core, 10
… AC magnetic field power supply.

Claims (1)

[Claims] 1. An exciting device for applying an alternating magnetic field to a subject made of a non-magnetic material, a sensor unit for detecting a minute magnetic field generated in the subject by the exciting device, and the sensor unit for the subject. A mechanism unit for holding in a non-contact manner, a signal processing device for signal processing a detection signal of the sensor unit, and a relationship between a change in the characteristic value of a minute magnetic field previously obtained in a test material and the fatigue damage degree of the subject. A deterioration degree determination means for determining the degree of fatigue damage of the subject from the master curve shown and a display means for displaying the results thereof are provided, and the sensor portion is directed to the sensor portion of the magnetic field of the exciting coil by reverse excitation. A material deterioration inspecting device comprising a fluxgate magnetometer capable of measuring a magnetic field in a state where the influence is cancelled.