JPS6222406B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention deals with stress occurring in magnetic metal materials such as buildings and bridge girders that have already been subjected to loads, or due to welding or gas switching. The present invention relates to a stress measurement method that accurately and reliably measures the absolute value of stress that has already occurred in the metal material itself, such as residual stress inside the magnetic metal material.

In general, the magnetic permeability of magnetic metal materials has a unique value depending on the material and composition, and even if the materials are the same and have the same composition, the magnetic permeability will be lower in places where tensile stress is generated when a load is applied. It has the property that it increases in proportion to the increase in stress, and conversely decreases in proportion to the increase in stress in areas where compressive stress is generated. It is known to take advantage of this property to apply magnetic force to a location where stress is acting, and to measure the generated stress value by measuring the amount of change in the magnetic flux passing through the metal magnetic body.

Conventional measurement methods applying this principle include, for example, Japanese Patent Publication No. 39-2178 and Japanese Patent Publication No. 51-44425. Two pairs of parallel through-holes are made in the core of the main body, and wires are wound in each to form an excitation coil and a measurement coil. When these cores are brought close to the surface of the material to be measured, the excited magnetic flux passes through the core and flows through the surface of the material being measured. The magnetic flux generated in the material to be measured is closed by closing the magnetic path flowing through the material to be measured, and detecting with the measuring coil the change in the magnetic flux flowing in the iron core, which is induced according to the load on the material to be measured. The purpose of this test was to measure stress, and in the latter case, when an excitation coil and a measurement coil are wound around the same horseshoe-shaped iron core, and the magnetic pole of the iron core is brought into contact with the surface of the material to be measured, the excitation coil is energized. The excitation flux closes the magnetic path passing through the core and inside the material to be measured, and changes in the magnetic flux flowing inside the core body, which is induced according to the load on the material to be measured, are reflected in the magnetic flux that is wound around a part of the same core. The purpose is to measure the stress generated inside the material to be measured by detecting it with a measuring coil.

However, as mentioned above, in all conventional stress measurement methods, both an excitation coil and a measurement coil are wound around the same core body, and the excitation flux energized by one excitation coil passes through the core to the measurement target. This measurement method uses a measurement coil to measure the difference in the amount of magnetic flux passing through the core when the magnetic path passing through the material is closed depending on the load, but unfortunately, the amount of magnetic flux flowing through the core at this time is Not only is the difference in the amount of change extremely small and difficult to detect, but even the slightest unevenness on the surface of the material to be measured creates a gap between the material and the magnetic pole, which in itself generates noise and causes the amount of magnetic flux to fluctuate drastically. This resulted in a situation where it was no longer even possible to measure it. Efforts have been made to improve the above technology in order to eliminate this drawback, but since the measurement principle itself remains the same, the problem has not been fundamentally resolved, and the current situation is that it has not yet been put into practical use.

The present invention was made with the aim of solving the above-mentioned drawbacks of the conventional technology. is the amount of excitation flux when the magnetic pole of the horseshoe-shaped excitation magnet comes into contact with the surface of the material to be measured, and the amount of magnetic flux flowing through the material to be measured via the excitation magnet body, and the amount of magnetic flux flowing through the material to be measured via the excitation magnet body. It is determined as the sum of the amount of magnetic flux flowing in the outside space and the space outside the material to be measured, and there is an inversely proportional relationship between them.Furthermore, the amount of magnetic flux flowing in the outside space is determined by noise, etc. Changes in the magnetic flux flowing through the space described above are based on the results of the inventor's experiments and research, which show that there is very little interference, that the value is stable, and that the difference is large depending on the load applied to the material. The feature is that the absolute value of the stress generated in the material can be accurately measured by measuring the amount.

Hereinafter, embodiments of the present invention will be described based on illustrative drawings. In the first embodiment shown in FIG. , a magnetic flux sensing element 4 made of an element that acts on lines of magnetic force, such as a Hall element or an SDME element, is provided. As shown in FIG.
It has the property of generating a voltage in the A-B direction in proportion to the amount of magnetic flux passing through it.

According to the above configuration, the two magnetic poles 2 and 3 of the permanent magnet 1 are brought into contact with the surface of the material to be measured 5. Since the amount of change in the magnetic flux flowing through the material to be measured 5 is proportional to the magnitude of the stress generated, for example, if tensile stress is generated in the material to be measured 5, the magnetic permeability is high at that location, making it difficult for the magnetic flux to pass through. On the other hand, the amount of magnetic flux passing through the space outside the material to be measured 5, that is, the magnetic flux sensing element 4, decreases due to an inverse correlation.
The voltage generated in the -B direction decreases. The magnetic permeability of the material to be measured 5 made of a magnetic substance has a unique value depending on its material and composition. Conversely, if the voltage value corresponding to the magnitude is measured in advance, the stress value can be determined based on the voltage value generated in the magnetic flux sensing element 4 described above.

Further, as shown in FIG. 2 as a second embodiment of the present invention, the excitation magnet 1 is constructed by winding an input coil 6 around a horseshoe-shaped iron core made of a material with almost no residual magnetism. It can also be implemented in a configuration in which an oscillator (not shown) is connected to the input coil 6 to provide an alternating voltage of a constant intensity at an appropriate frequency. As in the first embodiment, by measuring the voltage value generated in the magnetic flux sensing element 4, the stress value generated in the material to be measured 5 can be measured.

Furthermore, as a third embodiment of the present invention, as shown in FIG. It is also possible to implement a configuration in which the output coil 7 is wound around a preferably ring-shaped iron core made of a material that hardly retains magnetism, and a detector (not shown) is connected to the output coil 7. The arrangement of the excitation magnet 1 and the magnetic flux sensing element 4 is the same as in the first and second embodiments.

In summary, the present invention provides an excitation horseshoe-shaped magnet 1
The excitation magnetic poles 2 and 3 configured at both ends of the excitation magnet 1 are brought into contact with the surface of the material to be measured 5, and of the magnetic flux excited by this, the amount of magnetic flux that is outside the material to be measured 5 and outside the body of the excitation horseshoe magnet 1 is A magnetic flux sensing element 4 is arranged between the excitation magnetic poles 2 and 3 to measure the amount of magnetic flux flowing in the space between the excitation magnetic poles 2 and 3, and the magnetic flux detection element 4 measures the amount of magnetic flux flowing in the space between the excitation magnetic poles 2 and 3. It is characterized by measuring the stress generated inside the measurement material 5.

Therefore, according to the measuring method of the present invention, since the difference in the change in magnetic flux is large, easy-to-read and highly accurate measurement is possible.

In addition, stable measurement can be performed because it is not inhibited by external factors such as noise.

Furthermore, it can be said that it is an industrially useful stress measuring method because it has a simple configuration and the equipment cost is low.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention; FIG. 1 is a perspective view showing the first embodiment, FIG. 2 is a front view showing the second embodiment, and FIG. 3 is a front view showing the third embodiment. FIG. 1... Horseshoe magnet for excitation, 2, 3... Magnetic pole for excitation, 4... Magnetic flux detection element, 5... Material to be measured.

Claims (1)

[Claims] 1 The excitation magnetic poles 2 and 3 configured at both ends of the excitation horseshoe magnet 1 are brought into contact with the surface of the material to be measured 5, and of the magnetic flux excited thereby, the amount of magnetic flux that is outside the material to be measured 5 and is A magnetic flux sensing element 4 is disposed between the excitation magnetic poles 2 and 3 to measure the amount of magnetic flux flowing in the space between the excitation magnetic poles 2 and 3 outside the excitation horseshoe-shaped magnet 1 body, and the magnetic flux flowing in the space is arranged between the excitation magnetic poles 2 and 3. A magnetic permeability stress measurement method characterized by measuring the stress generated inside the material to be measured 5 based on the amount of change in magnetic flux.