JP2000356565A - Vibration test equipment - Google Patents

Abstract

(57) [Problem] To provide a vibration test apparatus which can cope with a vibration test for a high frequency exceeding 50 kHz, can easily execute the test, and can easily cope with automation. SOLUTION: This is a vibration test apparatus in which a target T placed on a support part 1 is vibrated by a vibrating part 2, and a response of the target T is detected by a signal detecting part 3. The vibrating unit 2 includes a discharge probe 20 arranged close to and a discharge controller 22 for generating a discharge by applying a potential difference between the discharge probe 20 and the object T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration test apparatus that vibrates an object placed on a support by a vibrator and detects a response of the object by a signal detector.

[0002]

2. Description of the Related Art In a gas turbine engine for an aircraft, for example, rotating parts such as rotor blades and turbine rotor blades of a high-pressure compressor are subjected to repetitive high-frequency stress due to rotational motion.
For example, such a moving blade receives aerodynamic stress (excitation force) by a stationary blade arranged immediately upstream, and in this case, the vibration frequency of the excitation force is obtained by multiplying the number of rotations by the number of stationary blades. . If the vibration frequency matches the natural frequency of the moving blade, resonance occurs in the moving blade and a large stress acts. The design is made so that they do not match.

[0003] A vibration test device is used for the purpose of actually confirming the natural frequency of a rotor blade manufactured based on such a design or examining variations during manufacture. The vibration test apparatus includes a support for installing the object, a vibration unit for vibrating the object, and a signal detection unit for detecting a response of the object. Various methods have been proposed according to the characteristics and test contents.

[0004] Of these, the vibration section is often obtained by a hitting test. The impact test is a method in which the object is vibrated by hitting the object with a hammer.There is no need to attach the vibration system to the object, and a spectrum from low frequency to a certain high frequency can be obtained at once, and it can be performed in a short time. It has the advantage that it can be performed in a wide variety of applications. Particularly, it is widely used in a vibration test of a relatively small structure such as the above-mentioned rotor blade.

[0005]

However, the impact test has the following problems.・ It is extremely difficult to respond to high-frequency vibration tests exceeding 50 kHz. FIG. 5 shows a striking excitation force by a striking hammer. The energy continuously applied for Tp seconds on the time axis has a frequency spectrum having a shape close to, for example, a half sine wave. As shown in (b), the upper limit Fmax of the target frequency must be smaller than the zero crossing point P indicated by the groove between the valleys of the spectrum. The frequency of the zero-crossing point P is inversely proportional to the duration Tp of the wave, and the zero-crossing point P has a higher frequency as the waveform is sharper and Tp is smaller. However, in the impact test, a shock wave is applied to the target object by an actual impact, so that it is difficult to make the duration Tp less than a predetermined value. For this reason, the target frequency upper limit Fmax is limited to 50 kHz. In practice, when the frequency exceeds 32 kHz, considerable skill and time are required for the impact and test. In recent years, among the above-mentioned gas turbine engines, in many cases, the vibration frequency received by rotating parts such as the moving blades exceeds 50 kHz, mainly small and high-powered ones, and it is difficult to obtain the characteristics of vibration in a high frequency region in the impact test. .

The accuracy greatly depends on the skill and skill of the practitioner. The impact test uses a human as a part of the vibration system because the implementer hits the target with an impact hammer. For this reason, the degree of the quality of the vibration depends on the skill and experience of the practitioner, which is relatively large, and beginners often fail. Also, in an actual test, an average of several tests excluding failures is often taken as the result, which is often troublesome.

The apparatus becomes complicated when the impact test is automated. In order to automate the impact test, a mechanism for precisely controlling mechanical movement such as impact is required. Therefore, the apparatus becomes complicated, and it is difficult to realize automation.

The present invention has been made in view of the above-mentioned circumstances, and can cope with a vibration test for a high frequency exceeding 50 kHz, can easily execute the test, and can be easily automated. It is an object of the present invention to provide a vibration test apparatus that can respond.

[0009]

According to a first aspect of the present invention, an object mounted on a supporting portion is vibrated by a vibrating portion, and a response of the object is detected by a signal detecting portion. A vibration testing device, wherein the vibrating unit comprises a discharge probe arranged with the tip close to the object, and a discharge controller for generating a discharge by applying a potential difference between the discharge probe and the object. Provided technology is adopted. In this vibration test apparatus, the vibrating unit includes a discharge probe and a discharge controller, so that a discharge is generated between the discharge probe and the object to give a shock wave having a very short duration to the object, thereby generating a shock wave. The object can be vibrated. Therefore, it is possible to cope with a high frequency vibration test.

According to a second aspect of the present invention, in the vibration test device of the first aspect, a technique is employed in which the discharge controller includes a transformer for changing a potential difference between the discharge probe and the object. Since this vibration test apparatus has a transformer for changing the potential difference between the discharge probe and the target, various characteristics can be obtained by generating a discharge with an energy amount suitable for the target according to the characteristics. It is possible to reliably perform a vibration test on the target object.

The invention according to claim 3 is the invention according to claim 1 or 2
In this vibration test apparatus, a technique is employed in which a vibrating unit includes a probe guide mechanism that holds a discharge probe and changes a distance between the discharge probe and an object. In this vibration test device, the probe guide mechanism changes the distance between the discharge probe and the object, so that it is possible to easily cope with a change in the size of the object, and according to the characteristics of the object. It is possible to set the optimal distance between the discharge probe and the object, and efficiently vibrate the object.

According to a fourth aspect of the present invention, there is provided the vibration test apparatus according to any one of the first to third aspects, wherein the signal detection unit includes a non-contact type response converter for detecting a response of the object in a non-contact manner. Adopted. In this vibration test apparatus, since the signal detection unit includes the non-contact type response converter, the attachment / detachment of the object can be more easily performed.

According to a fifth aspect of the present invention, in the vibration test apparatus according to any one of the first to fourth aspects, a technique is employed in which the support section has an exchange mechanism for automatically exchanging and installing an object. In this vibration test apparatus, since the exchange mechanism automatically replaces and installs the objects, it is possible to continuously test a plurality of objects.

According to a sixth aspect of the present invention, in the vibration test apparatus according to any one of the first to fifth aspects, the support portion includes a support mechanism in which a groove is formed for fitting a part of the object and installing the object. Technology is adopted. In this vibration test device,
Since a groove is formed for fitting a part of the object into the support mechanism for installation, the object can be easily attached and detached.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vibration test apparatus according to the present invention will be described below with reference to FIGS.
FIG. 2 shows the overall system configuration of the present embodiment. As shown in FIG.
It comprises a vibration unit 2, a signal detection unit 3, a signal processing unit 4, and a control unit 5. In the present embodiment, a vibration test is performed on a moving blade T for a gas turbine engine (for example, a moving blade of a high-pressure compressor).

As shown in FIG. 1, the support section 1 supports an object (moving blade) T to be tested by a support mechanism 10. Further, an exchange mechanism 11 is provided, and the attachment / detachment of the moving blade T to / from the support mechanism 10 is automatically performed. The support mechanism 10 is composed of a structure having sufficient mass and rigidity. Here, a tab tail-shaped groove 10a is formed on the installation surface so that the moving blade T is installed. Further, the moving blade T mounted in the groove 10a is held and fixed with a predetermined force using, for example, hydraulic pressure or air pressure. Furthermore, the support mechanism 10 is always grounded (grounded), and grounds the moving blade T to be supported. On the other hand, the exchange mechanism 11 has driving means (not shown), automatically transports the moving blade T supplied from the outside to the supporting mechanism 10, mounts the moving blade T in the groove 10 a of the supporting mechanism 10, and performs a test. The trailing blade T is inserted into the groove 10a.
It is configured to be extracted from and sent to the outside.

The vibrating section 2 applies a shock wave to the rotor blade T using discharge, and includes a discharge probe 20, a probe guide mechanism 21, and a discharge controller 22. The discharge probe 20 has a conductor 20a having a substantially spherical or pointed tip, and is held by a probe guide mechanism 21 via an insulator 20b. Discharge probe 2
In the case of 0, a plurality of objects having different tip shapes are prepared, and are properly used depending on the material and surface characteristics of the object. The probe guide mechanism 21 has a driving unit (not shown),
Upon receiving the instruction, the discharge probe 20 is moved so that the tip of the discharge probe 20 and the rotor blade T are at a predetermined distance (gap) G. Further, the location where the shock wave is generated by the discharge is a location close to, for example, the root of the blade T, and the location of the discharge is determined according to, for example, the output response of the target mode to be acquired.

The discharge controller 22 includes a discharge probe 2
It is configured to apply a predetermined potential to the leading end of the zero.
FIG. 3 shows a basic equivalent circuit for discharging. If the capacitor C is raised to the voltage E while the gap G is set at a predetermined distance, the gas insulation in the gap G is broken and discharge occurs. Discharge controller 22 of the present embodiment
Has a transformer (not shown) composed of a plurality of capacitors having different electric capacities, and a capacitor to be charged is selected in accordance with the size and material of the object. Further, a switching circuit (not shown) for starting is provided, and a discharge in the gap G is generated by starting in this switching circuit. As a starting mechanism in the switching circuit, for example, a starting gap using creeping discharge by a needle electrode and a Teflon tube is used.

Generally, when a discharge is generated in the atmosphere, the gap G and the electrode shape (discharge probe 20
A predetermined voltage corresponding to the tip and the object T) is required. For example, discharge between parallel plates requires a higher voltage than discharge between spheres. In this embodiment,
Returning to FIG. 1, the gap G between the tip of the discharge probe 20 and the rotor blade T is predetermined to a predetermined value of about several mm, and the discharge controller 22 determines that the voltage between the gaps G is slightly higher than the voltage required for discharge. So that the discharge probe 20
To give a potential. It has been previously confirmed that the discharge generated by this potential does not cause damage or deterioration of the material on the surface or the like of the rotor blade T.

The signal detector 3 converts the physical response of the rotor blade T into an electrical signal and detects the electrical signal.
0 and an amplifier 31. The amplifier 31 amplifies and adjusts the electric signal from the response converter 30 until subsequent signal processing becomes possible. In the response converter 30,
A non-contact type is applied. Here, a laser Doppler velocimeter 30 which irradiates an object with laser light and obtains a time response of a velocity from a Doppler shift frequency of reflected light is used. In addition, this laser Doppler velocimeter 30
The laser beam is emitted and the reflected light is received from a slightly distant place that does not interfere with other movable mechanisms to a place suitable for detecting a response, for example, the free end side of the object. As the response converter 30, in addition to the laser Doppler velocimeter, a displacement meter using eddy current, laser light, capacitance, or the like is used.

Here, the signal processing unit 4 has an FFT (Fast
Fourier Transform) analyzer is used. F
The FT analyzer 4 converts the electric signal from the signal detection unit 3 into a digital signal and performs necessary calculations, and then displays the result on the frequency axis.
Is output to As the signal processing unit 4, a computer incorporating signal processing software is used in addition to the FFT analyzer.

The control unit 5 controls the entire system described above, and instructs each unit to automatically and continuously perform the vibration test of the moving blade T.

In the vibration test apparatus having the above structure, the moving blade T
The flow of the operation when performing a vibration test for measuring the natural frequency of the device will be described below. The exchange mechanism 11 mounts and sets the blade T received from the outside in the tab tail groove 10a of the support mechanism 10. When the installation of the rotor blade T is confirmed, the probe guide mechanism 21 is driven to bring the discharge probe 20 closer to the rotor blade T so as to have a predetermined gap G. When the discharge controller 22 applies a predetermined potential to the discharge probe 20, a discharge occurs in the gap G.

At this time, the rotor blade T receives a minute and extremely short shock wave due to the discharge. The laser Doppler velocimeter 30 detects the velocity response of the rotor blade T excited by the shock wave as a time history analog signal. The FFT analyzer 4 converts the vibration received through the amplifier 31 into a digital signal, performs necessary calculations, and outputs a result expressed in a frequency axis to the control unit 5. When such a series of vibration tests is completed, the replacement mechanism 11 replaces the next turbine blade T and sets the support mechanism 10 to perform the next vibration test. Such a series of flows is repeated, and the vibration inspection of the rotor blade T is automatically and continuously performed.

FIG. 4 shows the measurement results of the natural frequency of the moving blade T using the discharge as described above. From the waveform diagram, it can be seen that the natural frequency is reliably detected even in a frequency region exceeding 50 kHz.

That is, according to the present embodiment, by generating a discharge between the discharge probe 20 and the moving blade T, a shock wave having a very short duration is given to the moving blade T to vibrate the moving blade T. Can be. As a result, a high-frequency spectrum can be obtained, and it is possible to cope with a high-frequency vibration test exceeding 50 kHz, which is difficult in a hit test. In addition, since the excitation by discharge has less noise and is easy to detect the natural frequency even with a small excitation energy compared to the excitation by impact, it is possible to sufficiently excite the rotor blade T without damaging the surface or the like. it can. In addition, in the present embodiment, since the transformer is provided with the transformer for changing the potential difference between the discharge probe 20 and the rotor blade T, it is possible to reliably perform the vibration test even on an object having various characteristics. Further, by changing the distance between the discharge probe 20 and the moving blade T by the probe guide mechanism 21, it is possible to easily cope with a change in the size of the target object.

In this embodiment, since the object is vibrated by an electric signal, the accuracy does not greatly depend on the skill and skill of the practitioner. Therefore, a highly accurate test can be performed with a small number of times, and the labor required for the test can be reduced. Furthermore, in order to vibrate the tip of the discharge probe 20 close to the rotor blade T,
The excitation point can be easily specified, and the target position can be reliably excited.

Further, in this embodiment, both the excitation and the response detection are made non-contact by using the laser Doppler velocimeter 30,
With the configuration in which the moving blades T are automatically replaced and installed by the exchange mechanism 11, a continuous vibration test of a plurality of moving blades T is realized by a simple mechanism.
Further, the support mechanism 10 is formed with a tab tail-shaped groove 10a for fitting and installing the moving blade T.
Can be easily attached and detached, and the moving blade T can be reliably held.

In this embodiment, the discharge is generated by using the capacitor in the discharge control. However, the present invention includes a configuration in which the discharge is generated by using the piezoelectric element or the static electricity. In particular, when a piezoelectric element is used, a power source for discharging is not required, and the discharge can be generated by a simpler mechanism, and the device can be made compact.

Also, the flow of the discharge current grounded from the object may be controlled by, for example, a variable resistor or the like, so that the discharge time is controlled to some extent. By controlling the discharge time, it becomes possible to change the target frequency range according to the target.

[0031]

As described above, according to the present invention, the following effects can be obtained. In the vibration test apparatus according to the first aspect, since the vibrating unit includes the discharge probe and the discharge controller, the discharge between the discharge probe and the object causes the shock wave having a very short duration to the object. To vibrate the object. It is difficult to use a shock test because it uses a shock wave of extremely short duration.
It is possible to cope with a high frequency vibration test exceeding 0 kHz. In addition, since this device vibrates the target object by an electric signal, the accuracy does not greatly depend on the skill and skill of the practitioner. Therefore, a highly accurate test can be performed with a small number of times, and the labor required for the test can be reduced. Further, since the vibration can be performed with a simple mechanism, an apparatus for automation can be easily configured.

Further, since the vibration is generated by using the discharge, it is suitable for a vibration test of a relatively small object. In other words, even a small structure (object) in which the location of the impact with the impact hammer is difficult to determine can be easily excited using the discharge. Similarly, the present invention can be easily applied to a vibration test of a component in an assembled state, and can be widely applied to various structures.

In the vibration test apparatus according to the second aspect of the present invention, since the voltage change means for changing the potential difference between the discharge probe and the object is provided, a discharge of an energy amount suitable for the object is generated according to the characteristics. By doing so, it is possible to reliably perform a vibration test on an object having various characteristics. Also,
By changing the potential difference, it is possible to easily prevent the target from being damaged by the discharge.

In the vibration test apparatus according to the third aspect, since the probe guide mechanism changes the distance between the discharge probe and the object, it can easily cope with a change in the size of the object. Moreover, the object can be efficiently vibrated by setting the discharge probe and the object at an optimal distance for the discharge in accordance with the characteristics of the object. Further, by moving the discharge probe, attachment / detachment of the object can be easily performed.

In the vibration test apparatus according to the fourth aspect, since the signal detecting section is provided with the non-contact type response converter, the attachment / detachment of the object can be more easily performed and the automation can be facilitated. It can be realized.

In the vibration test apparatus according to the fifth aspect, since the replacement mechanism automatically replaces and installs the objects, a plurality of objects can be continuously tested. Therefore, the labor required for the test can be greatly reduced.

In the vibration test apparatus according to the sixth aspect, since a groove is formed in the support mechanism for fitting and installing a part of the object, the object can be easily attached and detached. For this reason, automation can be realized more easily.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment according to the present invention.

FIG. 2 is a block diagram showing an overall system configuration of an embodiment according to the present invention.

FIG. 3 is a circuit diagram showing a basic equivalent circuit for discharging.

FIG. 4 is a waveform diagram showing a measurement result of a natural frequency of a moving blade using discharge.

FIGS. 5A and 5B are waveform diagrams showing a striking excitation force by a striking hammer, where FIG. 5A shows a time history waveform and FIG. 5B shows a frequency spectrum.

[Explanation of symbols]

 T rotor blade (object) G gap 1 support unit 2 vibration unit 3 signal detection unit 4 FFT analyzer (signal processing unit) 5 control unit 10 support mechanism 11 exchange mechanism 10a groove 20 discharge probe 21 probe guide mechanism 22 discharge controller 30 Laser Doppler velocimeter (response converter) 31 Amplifier

Claims (6)

[Claims] 1. A vibration test apparatus for vibrating an object placed on a support by a vibrator and detecting a response of the object by a signal detector, wherein the vibrator has a tip A vibration test apparatus, comprising: a discharge probe arranged close to the object; and a discharge controller for generating a discharge by applying a potential difference between the discharge probe and the object. 2. The vibration test apparatus according to claim 1, wherein the discharge controller includes a transformer for changing a potential difference between the discharge probe and the object. 3. The apparatus according to claim 1, wherein the vibrating section includes a probe guide mechanism for holding the discharge probe and changing a distance between the discharge probe and the object.
Or the vibration test apparatus according to 2. 4. The vibration test apparatus according to claim 1, wherein the signal detection unit includes a non-contact type response converter that detects a response of the object in a non-contact manner. . 5. The vibration test apparatus according to claim 1, wherein the support section includes an exchange mechanism for automatically exchanging and installing the object. 6. The vibration test according to claim 1, wherein the support unit includes a support mechanism having a groove for fitting and installing a part of the object. apparatus.