JP3223991U - Nondestructive inspection equipment - Google Patents

Abstract

A non-destructive inspection apparatus capable of inspecting a weak change in magnetic flux density is provided. A nondestructive inspection apparatus 10 includes a magnetic sensor 16 comprising an amorphous magnetic core 12 and a coil 14, a power supply circuit 18 for supplying an excitation current to the coil 14, and a differentiation circuit 22 for differentiating a voltage change from the coil 14 into direct current. Is provided. In the magnetic sensor 16, the length direction of the amorphous magnetic core 12 is inclined with respect to the surface of the object to be inspected. The power supply circuit 18 includes an AC power supply 36, a DC power supply 38, and an amplifier 40. A first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a capacitor C and an operational amplifier OP are provided, and the differentiating circuit 22 includes a capacitor C and a fourth resistor R4. [Selection] Figure 1

Description

  The present invention relates to a nondestructive inspection apparatus capable of inspecting abnormal parts such as scratches and thickness changes of an object to be inspected.

  Conventionally, various nondestructive inspection apparatuses have been developed and disclosed. For example, the nondestructive inspection device of Patent Document 1 below includes a magnet and a magnetic sensor. The inspection object is magnetized with a magnet, and the magnetic sensor is moved along the surface of the inspection object to measure the magnetic flux density on the surface. If there is an abnormal part such as a scratch or thinning in the inspection object, the magnetic flux density on the surface changes. By detecting the change in the magnetic flux density with a magnetic sensor, an abnormal location can be detected.

  However, since iron is a ferromagnetic material, the magnetic flux leaking from the abnormal part is small and it is difficult to detect a change in magnetic flux density. If there is an abnormal part on the back or inside of the inspection object, the leakage flux is small but changes appear. It is required to detect such a weak change in magnetic flux density.

JP 2010-151626 A

  The objective of this invention is providing the nondestructive inspection apparatus which can test | inspect the weak change of magnetic flux density.

  A nondestructive inspection apparatus of the present invention comprises a magnet for magnetizing an object to be inspected, an amorphous magnetic core, and a coil wound around the amorphous magnetic core, and the length direction of the amorphous magnetic core is the surface of the inspection object. A magnetic sensor arranged so as to be inclined with respect to the power source, a power supply circuit for supplying an excitation current superimposed with a direct current and an alternating current to the coil, and differentiating an output voltage obtained by converting the voltage change detected by the coil into a direct current And a differentiating circuit.

  In order to receive the output voltage of the coil, a first resistor, a second resistor connected in series to the first resistor, a third resistor connected in parallel to the first resistor, and a parallel connection to the third resistor And the operational amplifier in which the third resistor is connected to the non-inverting input terminal, the inverting input terminal is connected between the first resistor and the second resistor, and the non-inverting input terminal of the operational amplifier and the ground And a connected fourth resistor. The first resistor and the second resistor have the same resistance value, and the third resistor and the fourth resistor have the same resistance value. When a capacitor is connected in parallel to the third resistor R3 of this circuit, a differential circuit is configured by the capacitor and the fourth resistor R4.

  According to the present invention, since the magnetic sensor is inclined with respect to the object to be inspected, the sensitivity of the magnetic sensor is good and it is easy to detect an abnormal part. By providing a capacitor in the differentiating circuit, it is possible to output only those having a large voltage change rate caused by an abnormal location, and it is easy to detect the abnormal location.

It is a figure which shows the structure of the nondestructive inspection apparatus of this invention. It is a figure which shows a mode that a magnetic flux leak is detected with a sensor. (A) is a graph which shows the relationship between the detection voltage of a coil, and the position which carried out the scanning movement of the sensor, (b) is a graph which shows the relationship between the output of a differentiation circuit and the position which carried out the scanning movement of the sensor.

  A nondestructive inspection apparatus of the present invention will be described with reference to the drawings.

  A nondestructive inspection apparatus 10 of the present invention shown in FIG. 1 includes a magnetic sensor 16 comprising an amorphous magnetic core 12 and a coil 14, a power supply circuit 18 for supplying an exciting current to the coil 14, and rectifying and smoothing a change in amplitude of the voltage of the coil 14. And a smoothing circuit 20 that outputs a DC voltage change and a differentiation circuit 22 that differentiates the DC voltage change.

  The material of the object to be inspected may be a material magnetized by a magnet, and includes, for example, a ferromagnetic material such as iron, cobalt, nickel, and an alloy containing them. The inspection object 24 shown in FIG. 2 has a plate shape, but the inspection object 24 may have an arbitrary shape. The nondestructive inspection apparatus 10 detects an abnormal portion 26 such as a crack or a thickness change of the inspection object 24. The nondestructive inspection apparatus 10 detects not only the abnormal portion 26 on the surface of the inspection object 24 but also the abnormal portion 26 on the back surface and inside of the inspection object 24.

  As shown in FIG. 2, the nondestructive inspection apparatus 10 includes a magnet 28. The magnet 28 is brought into contact with or close to the inspection object 24 with an N-pole and S-pole spaced at an arbitrary interval. The magnet 28 may be a permanent magnet or an electromagnet. The magnetic flux density of the magnet 28 may be about 1000 G or less. The magnetic flux 30 passes through the inspection object 24 by the magnet 28, and the inspection object 24 is magnetized. This magnetic flux 30 generates N-pole and S-pole magnetic poles on both sides of the abnormal portion 26, resulting in leakage flux 32. The leakage magnetic flux 32 appears on the surface of the inspection object 24 although it is weak even if the abnormal part 26 is inside and on the back surface of the inspection object 24.

  A stray magnetic field from the magnet 28 may affect the coil 14. In order to prevent this, a magnetic shield 34 as shown in FIG. 2 may be required. The magnetic shield 34 is a plate made of a ferromagnetic material such as iron. The magnetic shield 34 is disposed at least between the coil 14 and the magnet 28.

  The magnetic sensor 16 includes a rod-shaped amorphous magnetic core 12 and a coil 14 wound around the amorphous magnetic core 12. The amorphous magnetic core 12 is a bundle of a plurality of amorphous wires. For example, one amorphous strand is bundled with about 5 to 10 amorphous strands having a diameter of about 0.05 to 0.1 mm and a length of about 15 to 20 mm to form an amorphous core 12. If the diameter of the amorphous magnetic core 12 is 1 mm or less, the local leakage magnetic flux 32 can be detected. The coil 14 is formed by winding a copper wire around the amorphous magnetic core 12 a plurality of times. For example, a copper wire of about 0.07 mm is wound around the amorphous magnetic core 12 150 to 200 times. One end of the coil 14 is connected from the power supply circuit 18 through the resistor Ra, and the other end is connected to the ground. The magnetic sensor 16 moves while being close to the surface of the inspection object 24.

  The magnetic sensor 16 is disposed between the south pole and the north pole of the magnet 28. In the magnetic sensor 16, the length direction of the amorphous magnetic core 12 is inclined with respect to the surface of the inspection object 24 (FIG. 2). The inclination angle is about 10 to 20 °. The leakage magnetic flux 32 from the abnormal portion 26 on the surface of the inspection object 24 is relatively large, but the leakage magnetic flux 32 due to the abnormal portion 26 on the back surface or inside is weak, so in order to detect the leakage magnetic flux 32 efficiently, It is necessary to bring the coil 14 close to a direction parallel to the leakage magnetic flux 32. Note that if the length direction of the amorphous magnetic core 12 is parallel to the surface of the inspection object 24, the leakage magnetic flux 32 influences the both sides of the amorphous magnetic core 12, making it difficult to distinguish the abnormality. If the length direction of the amorphous magnetic core 12 is inclined with respect to the surface of the inspection object 24, the amorphous magnetic core 12 is affected by the leakage magnetic flux 32 from the side closer to the inspection object 24 and the sensitivity of the magnetic sensor 16. Will be better. The magnetic sensor 16 is scanned along the surface of the inspection object 24 back and forth, and left and right at a certain speed (about 10 to 20 cm / sec). At this time, the leakage magnetic flux 32 is detected on the abnormal part 26. If it is too late, it will be difficult to distinguish it from noise due to non-uniform remanence of the inspection object 24, and if it is too early, the signal will be weakened by a circuit for reducing electrical noise. Considering these, the scanning speed and circuit design are performed. It represents the response to a step-like input faster than the time constant τ = C × R.

  The power supply circuit 18 includes an AC power supply 36, a DC power supply 38, and an amplifier 40. The AC power source 36 is a power source that generates an AC current having a variable frequency and a variable amount of current. The DC power source 38 is a power source that variably divides a constant voltage to generate a DC current. The amplifier 40 receives the alternating current and the direct current simultaneously, amplifies the amount of current, and outputs an exciting current. From the above, the power supply circuit 18 generates an excitation current in which a direct current and an alternating current are superimposed.

  A resistor Ra is provided between the power supply circuit 18 and the coil 14. The exciting current is passed through the coil 14 through the resistor Ra. A change in the amplitude of the voltage of the coil 14 appears due to the resistor Ra. The change in the amplitude of the voltage of the coil 14 is amplified by the amplifier 42, and is rectified and smoothed by the diode D and the smoothing circuit 20 to become a DC voltage change. The smoothing circuit 20 includes a resistor Rb and a capacitor Ca.

  When the voltage of the coil 14 is amplified and the coil 14 is moved along the surface to be inspected, the presence / absence of the abnormal portion 26 can be determined from the change in the voltage converted to direct current in proportion to the amplitude of the voltage. Even if the change in the amplitude of the voltage of the coil 14 is used as it is, the abnormal part 26 of the inspection object 24 can be determined. However, when the abnormal part 26 is cracked, the voltage change is steep, so that the voltage change rate is further increased. By adding a differentiating circuit 22 that outputs a proportional voltage, it can be determined as a clear signal.

  In order to receive the output voltage of the coil 14, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a capacitor C, and an operational amplifier OP are provided. The first resistor R1 and the second resistor R2 are connected in series. The first resistor R1 is connected to the inverting input, and the third resistor R3 and the capacitor C are connected in parallel and connected to the non-inverting input. The inverting input terminal of the operational amplifier OP is connected between the first resistor R1 and the second resistor R2, and the non-inverting input terminal of the operational amplifier OP is connected to the third resistor R3. A fourth resistor R4 is connected between the non-inverting input terminal of the operational amplifier OP and the ground. The output of the operational amplifier OP is connected to the second resistor R2. In the circuit including these resistors R1, R2, R3, and R4, the output side voltage does not change with respect to the input side voltage change. By connecting a capacitor C in parallel to the third resistor R3, the capacitor C and the fourth resistor R4 become the differentiating circuit 22, and the change of the cycle shorter than the differentiation time constant τ (= CR4) or a short time. When a change voltage is input, an output voltage corresponding to the change speed is generated. That is, almost no slow change is canceled and output, and only a rapid voltage change due to the crack is output.

  The resistance values of the first resistor R1 and the second resistor R2 are equal, and the resistance values of the third resistor R3 and the fourth resistor R4 are equal. Although the voltage change output becomes zero by setting the resistance value in this way, the differentiation circuit 22 composed of the capacitor C and the resistor R4 causes the input voltage to be changed by the capacitor C connected in parallel to the third resistor R3. Outputs a voltage proportional to the differentiated rate of change. A voltage with a fast change in a shorter time than the time constant τ = CR4 is output. Therefore, only when the change in the detection voltage of the coil 14 is fast, the differentiating circuit 22 outputs a steep mountain as shown in FIG. 3B. When the change in the detection voltage of the coil 14 is small or slow and the DC component, the output of the differentiation circuit 22 becomes zero.

  The nondestructive inspection apparatus 10 may include a monitor that displays the output of the differentiation circuit 22. By displaying as shown in FIG. 3B on the monitor, the abnormal part 26 can be recognized.

  As described above, in the present application, the sensitivity of the magnetic sensor 16 is improved by tilting the magnetic sensor 16 with respect to the inspection object 24, and the abnormal portion 26 is easily detected. By providing the capacitor C in the differentiating circuit 20, it is possible to output only those having a fast voltage change caused by the abnormal part 26, and it is easy to detect the abnormal part 26.

  In addition, the present invention can be implemented in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

10: Non-destructive inspection device 12: Amorphous magnetic core 14: Coil 16: Magnetic sensor 18: Power supply circuit 20: Smoothing circuit 22: Differentiation circuit 24: Inspected object 26: Abnormal point 28: Magnet 30: Magnetic flux 32: Leakage magnetic flux 34 : Shield 36: AC power supply 38: DC power supply 40, 42: Amplifier resistance: R1, R2, R3, R4, R1, R2
Capacitors: C, Ca
Diode: D
Operational amplifier: OP

Claims (4)

A non-destructive inspection device for an inspection object,
A magnet for magnetizing the object to be inspected;
A magnetic sensor comprising an amorphous magnetic core and a coil wound around the amorphous magnetic core, the magnetic sensor being arranged such that the length direction of the amorphous magnetic core is inclined with respect to the surface of the inspection object;
A power supply circuit for supplying the coil with an exciting current in which a direct current and an alternating current are superimposed;
A differentiating circuit for differentiating the output voltage of the coil;
Non-destructive inspection device with In order to receive the output voltage of the coil,
The first resistor,
A second resistor connected in series to the first resistor;
A third resistor connected in parallel with the first resistor;
A capacitor connected in parallel with the third resistor;
An operational amplifier in which the third resistor is connected to a non-inverting input terminal, and the inverting input terminal is connected between a first resistor and a second resistor;
A fourth resistor connected between the non-inverting input terminal of the operational amplifier and ground;
The nondestructive inspection apparatus of Claim 1 provided with. The nondestructive inspection apparatus according to claim 2, wherein the first resistance and the second resistance have the same resistance value, and the third resistance and the fourth resistance have the same resistance value. The nondestructive inspection apparatus according to claim 2 or 3, wherein the differentiating circuit includes the capacitor and a fourth resistor.

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