JPH10142099A - Vibration experiment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically detect the reduction in vibration force while an object to be vibrated is being driven by a shaker. SOLUTION: A movable part 3 of a shaker 2 and a vibration object 1 are connected by a screw using a vibration force transfer rod 7 and a vibration force is detected by a pressure sensor 5 provided at an upper connection part and then measurement data are transfer to a measuring machine. The vibration object 1 and the vibration force transfer rod 7 are fixed by a screw via the pressure sensor 5 and are locked by a nut 6. The screw treated is crushed by a screw-fixing part 8a and the nut 6 is relaxed so that no vibration force cannot be transferred properly, which is detected from the change in the electric resistance of a screw-fixing part 8a. Similarly, the relaxation of screw is electrically detected from the change in electrical resistance at the screw-fixing part 8a between the movable part 3 of the shaker 2 and the vibration force transfer rod 7.

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, and more particularly, to transmitting a vibration force from a vibrator to a vibration test object via a vibration transmission rod and a vibration sensor. A vibration experiment device having a function of determining whether or not a vibration force from a vibration machine is correctly transmitted to a vibration test object in a vibration experiment vibration device that can be suitably used for an experimental modal analysis. Things.

[0002]

2. Description of the Related Art Recently, experimental modal analysis is often performed as a technique for analyzing the vibration characteristics of a vibration test object by experiments. In this method, an object to be excited is actually excited using an exciter, the transfer function of the entire object to be excited is measured, and the natural frequency of the object to be excited, damping and This is a method for obtaining vibration characteristics such as an amplitude ratio.
The transfer function of the object to be excited is obtained by measuring a response when an arbitrary exciting force is applied to the object to be excited, and calculating measurement data of the excitation input and the response. When the object to be excited is large, it is necessary to apply a sufficient exciting force using a plurality of exciters in order to measure an accurate transfer function.

FIG. 6 is a schematic configuration diagram for explaining a conventional vibration test apparatus. In FIG.
21 is a vibration target, 22 is a vibrator, 23 is a movable part of the vibrator, 24 is a fixed part of the vibrator, 25 is a pressure sensor, 26 is a nut, and 27 is a vibrating force of the vibrator 22. Is a vibration transmitting rod for transmitting the vibration to the vibration target 21, and 28 is a screw fixing portion.

[0006] A vibration object 22 shown in FIG.
Are mounted via a pressure sensor 25 for measuring the exciting force and an exciting force transmitting rod 27. In addition, the shaker 2
2 and the exciting force transmitting rod 27, the male screw of the exciting force transmitting rod 27 and the exciting force transmitting rod 2 formed on the movable portion 23 of the vibrator 22.
7 is screwed together with a screw fixing portion 28 formed of a coaxial female screw, and is locked with a nut 26. Further, the excitation object 21 and the excitation force transmission rod 27 are screwed together via a pressure sensor 25 at a screw fixing portion 28 composed of a female screw of the pressure sensor 25 and a male screw of the excitation force transmission rod 27. , And are locked and fixed by a nut 26.

The object 21 to be vibrated is vibrated in the axial direction of the vibrating force transmitting rod 27 by the vibrator 22 via the vibrating force transmitting rod 27, and the vibrating vibration is detected and detected by the pressure sensor 25. The measured data is transmitted to a measuring device (not shown). Further, when the vibrator 22 generates an unnecessarily large excitation force due to electric noise or the like, the excitation force transmission rod 27 breaks the excitation force transmission rod 27 from itself so that the excitation object 21 is excessively large. It has the function of protecting the vibrating force from being applied.

[0006]

In the case of this coupling method in which the exciting force of the vibrator 22 is transmitted to the object 21 to be excited by the exciting force transmitting rod 27 fixed by the screw fixing portion 28, the vibration is applied for a long time. When a vibration experiment is performed, the thread of the screw coupling portion 28 is crushed, and the vibration force may not be transmitted to the vibration target 21 according to the signal given to the vibration device 22. Conventionally, whether or not the exciting force according to the signal is transmitted to the exciting object 21 is determined by monitoring the data obtained by the pressure sensor 25. However, because of the above-mentioned monitor, it is necessary to display and confirm the vibrating force corresponding to each vibrator 22 at least after the measurement, and the work for confirmation is complicated.

The present invention has been made in view of the above circumstances, and has as its object to eliminate the above-described confirmation step and improve the efficiency of a transfer function measurement experiment.

[0008]

According to a first aspect of the present invention, there is provided a vibrator, a vibrating force transmission rod for transmitting a vibrating force generated by the vibrator to an object to be vibrated, and a vibrating machine. An exciting force sensor for measuring the generated exciting force, an exciting force transmitting rod and the exciting force sensor, and a nut for screw-connecting and locking each of the exciting force transmitting rod and the exciting device; The apparatus has an electric resistance measuring means for measuring an electric resistance value between the nut and the vibrating force sensor, or between the nut and the vibrator, and the electric resistance is measured by the electric resistance measuring means. The vibration exciter detects that the screw thread of the screw-coupled portion is crushed from the fluctuation of the electric resistance value so that the vibration force is not correctly transmitted to the vibration object. A rod that transmits the generated excitation force to the object to be excited,
An apparatus having a vibration force sensor for measuring a vibration force generated from the vibrator, the rod and the vibratory force sensor, and a nut for screw-locking and locking the rod and the vibrator respectively. An electric resistance measuring means for measuring an electric resistance value between the nut and the vibrating force sensor or between the nut and the vibrator; and the screw connection based on a change in the electric resistance value measured by the electric resistance measuring means. It is characterized by detecting that the exciting force is not transmitted to the exciting object correctly due to the collapse of the screw thread of the portion,
The data of the excitation force sensor is monitored, and the process of confirming the excitation force is made more efficient.

According to a second aspect of the present invention, in the vibration test apparatus according to the first aspect, when the electric resistance value becomes equal to or more than a set value, the vibration generator setup abnormality determining means for generating an abnormality signal is provided. The present invention is characterized in that an abnormal setup of the shaker can be automatically determined.

According to a third aspect of the present invention, in the vibration test apparatus according to the second aspect, a shaker amplifier for operating the shaker based on the abnormal signal generated from the shaker setup abnormality determining means. And shuts off the driving voltage of the vibrator, thereby preventing vibration in an abnormal state.

According to a fourth aspect of the present invention, in the vibration test apparatus according to the second aspect, the measurement data from the vibrating force sensor is transmitted to the measuring machine by the abnormal signal generated from the vibrator setup abnormality determining means. An amplifier for inputting a vibrating force sensor is controlled, and the input of the measurement data to the measuring device is cut off, so that the vibrating force measuring device can detect an abnormal vibration. It is.

According to a fifth aspect of the present invention, in the vibration test apparatus according to the second aspect, the measuring machine is controlled by the abnormal signal generated from the shaker setup abnormality judging means to invalidate the measured data. This feature is intended to prevent erroneous use of measurement data whose vibration is inappropriate.

According to a sixth aspect of the present invention, in the vibration test apparatus according to the fifth aspect, the abnormal signal generated from the vibrator setup abnormality judging means is inputted to the measuring device, and the measuring device is provided with a plurality of measuring devices. It is characterized by having means for alerting a measurer of which shaker setup in the shaker setup has an abnormality, so that the measurer can concentrate on the shake experiment.

According to a seventh aspect of the present invention, there is provided the vibration test apparatus according to the first aspect, wherein the exciting force transmitting rod and the exciting force sensor are disposed between the exciting machine and the exciting force transmitting rod. A connector is provided between the vibrator and the vibrating force transmitting rod, and the vibrating force transmitting rod and the vibrating force sensor are screw-connected to each other via the connector, and each screw-connected portion is locked. Measuring the electrical resistance between the nut and the connector and between the nut and the connector to detect a change in the electrical resistance, and crushing the screw thread of the screw joint to apply the vibration to the object to be vibrated. The present invention is characterized in that it is determined that the vibration force has not been correctly transmitted, so that a special operation for attaching a cord to a vibrator or a vibration force sensor is omitted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(Invention of claim 1) The invention of claim 1 is based on the fact that the screw thread of the screw fixing portion is flattened, and the excitation force according to the signal given to the vibrator is not transmitted to the object to be excited. The detection is performed based on a change in the electric resistance value.

FIG. 1 is a view for explaining an embodiment of the first aspect of the present invention, and FIG.
FIG. 1B is an enlarged sectional view of a portion M in FIG. 1A, and FIG.
1 is an enlarged cross-sectional view of an N portion of FIG. 1 (A), where 1 is an object to be excited, 2 is a shaker, 3 is a movable portion of the shaker 2, and 4 is a fixed portion of the shaker 2. 5 is a pressure sensor, 6 is a nut, 7 is a vibrating force transmission rod, 8a and 8b are screw fixing parts, 9a and 9b are electric resistance measuring parts, and 10 is a vibrator set-up.

[0017] Exciter setup 10 of the exciter test equipment
A vibrator 2 having a vibration target 1 and a movable part 3 provided on a fixed part 4, a vibrating force transmission rod 7 for transmitting a vibrating force of the vibrator 2 to the vibration target 1; And a pressure sensor 5 for measuring a vibration force transmitted to the vibration object 1 and transmitting measurement data to a measuring machine (not shown). As shown in FIG. 1C, the vibrator 2 and the vibrating force transmission rod 7 are coaxially screwed together and further locked by a nut 6 to form a screw fixing portion 8b. An electric resistance measuring section 9b is connected between the movable section 3 and the shaker. Electric resistance measuring section 9b
For example, a constant current is applied to the screw fixing portion 8b, and it is determined whether or not the screw thread of the screw fixing portion 8b is crushed from the electric resistance according to the magnitude of the voltage value.

On the other hand, the vibration transmitting rod 7 and the vibration object 1 are screw-connected via a pressure sensor 5 for measuring the vibration force applied to the vibration object 1 as shown in FIG. ), The pressure sensor 5 and the exciting force transmitting rod 7 are screw-connected,
The screw fixing portion 8a is locked by the nut 6, and whether or not the thread of the screw fixing portion 8a is crushed is determined from the electric resistance value of the electric resistance measuring portion 9a. The signal of the pressure sensor 5 is an FFT (Fast Fo
urier Transforms (fast Fourier transform) transmitted to a measuring device (not shown) such as an analyzer.

While the object 1 is being vibrated, the screw fixing portion 8
When the threads a and 8b are crushed, the pressure sensor 5 or the nut 6 that has tightened the vibrator 2 is loosened via the vibrating force transmission rod 7, and the electric resistance value is increased. It is possible to know that the force is not being transmitted to the excitation object 1. In FIG. 1, the exciting force applied to the exciting object 1 is measured by the pressure sensor 5, but a sensor capable of measuring the exciting force such as a force sensor or a torsion sensor capable of converting the exciting force into an electric signal. Any type of vibration sensor may be used.

(Inventions of Claims 2 and 3) The invention of claim 2 is an abnormal setup of a vibrator for judging whether or not the electric resistance measurement results of the electric resistance measuring units 9a and 9b are equal to or larger than a set value. A judging means is provided so that the vibration test apparatus outputs an abnormal signal when the vibration value exceeds a set value. Automatically stop the machine amplifier,
The drive of the vibrator is stopped.

FIG. 2 is a block diagram for explaining an embodiment of the second and third aspects of the present invention. In the figure, 11 is a signal generator, 12 is a vibrator amplifier, and 13 is a vibrator setup. Parts which are the abnormality determination means and operate in the same manner as in FIG. 1 are given the same reference numerals as in FIG.

The vibrator set-up 10 is shown in FIG. 1, and the vibrator 2 is driven by a vibrator amplifier 12 for amplifying a signal of a signal generator 11 for generating a signal of a vibrating force. You. The nut 6 measured by the electric resistance measuring unit 9
The electrical resistance between the pressure sensor 5 and the nut or the exciter 2 is input to the exciter setup abnormality determining means 13 and the input electrical resistance is set to a predetermined electric resistance. When the resistance value, that is, the nut 6 is loosened due to the collapse of the screw threads of the screw fixing portions 8a and 8b, the electric resistance value increases and the vibration force reaches a value at which the vibration force cannot be transmitted to the vibration target 1 properly, An abnormality signal is output from the abnormality determination means 13. Further, the abnormal signal stops the amplifying function of the vibrator amplifier 12 and stops the driving of the vibrator 2 so that an abnormal vibration force is not applied to the vibration target 1.

According to a fourth aspect of the present invention, an abnormal signal output from the vibrator setup abnormality judging means 13 is transmitted to a pressure sensor amplifier, and the vibration signal detected by the pressure sensor 5 is detected. The input to the vibration measuring device is cut.

FIG. 3 is a block diagram for explaining an embodiment of the fourth aspect of the present invention. In FIG. 3, reference numeral 14 denotes an amplifier for a pressure sensor, and 15 denotes a measuring instrument.

In the exciter setup 10, the exciter signal detected by the pressure sensor 5 is input to the pressure sensor amplifier 14 and amplified, and the amplified exciter signal is input to the measuring device 15 and Although the processing is performed, when an abnormal signal is output from the shaker setup abnormality determining means 13, the abnormal signal is transmitted to the pressure sensor amplifier 14. In accordance with this, the pressure sensor amplifier 14 cuts the exciting force data during the measurement. That is, by stopping the transmission of the excitation force signal to the measuring device 15, it is possible to detect that an abnormality has occurred in the excitation force at the time of measurement on the measuring device 15 side.

(Inventions of claims 5 and 6) The invention of claim 5 is directed to a measuring device 15 which is sampling the measurement data of the pressure sensor 5 during measurement of an abnormal signal generated from the vibrator setup abnormality judging means. In this case, the measurement data is invalidated. The invention according to claim 6 is a measuring instrument 1
Numeral 5 indicates the number of the shaker setup 10 in which an abnormality has occurred when the abnormality signal is received, and notifies the measurer of the occurrence of the abnormality.

FIG. 4 is a block diagram for explaining an embodiment of the present invention according to the fifth and sixth aspects. Parts having the same functions as those in FIG. 1 are denoted by the same reference numerals as in FIG. It is.

In the block diagram shown in FIG. 4, a signal measured by the pressure sensor 5 is amplified by a pressure sensor amplifier 14 and input to a measuring device 15. At this time, an abnormality occurs in which the electric resistance value between the nut 6 and the pressure sensor 5 or the electric resistance value between the nut 6 and the vibrator 2 increases, and the vibrator setup abnormality determining means 13 detects this. Is detected and an abnormal signal is issued, the measuring device 15 such as an FFT analyzer receives the abnormal signal and invalidates the data being measured.

As described above, since an abnormal signal is generated from the vibrator setup abnormality judging unit 13 to invalidate the data being measured, the measurer does not notice the abnormality of the vibrator setup 10 and the It is possible to prevent measurement data from being erroneously adopted depending on the state.

When a plurality of shaker setups 10 are provided, the abnormal signal output from the shaker setup abnormality determination means 13 and input to the measuring machine 15 is
The shaker setup 10 in which the abnormality has occurred in step 5 is displayed with the number of the shaker setup 10 set in advance to inform the measurer. For this reason, conventionally, the excitation state of the excitation force has been checked during or after the measurement. However, according to the present invention, the measuring device 15 directly informs the measurer of the abnormality. And the operator can concentrate on the measurement of the transfer function, so that the vibration experiment can be performed efficiently.

According to a seventh aspect of the present invention, there is provided an exciting force transmitting apparatus for transmitting an exciting force generated by a vibrating machine 2 of an exciting experimental device according to the first aspect to an object 1 to be excited. Rod 7 and shaker 2
And connectors between the vibrating force transmission rod 7 and the pressure sensor are provided so as to eliminate wiring work between the vibrator 2 or the pressure sensor 5 and the electric resistance measuring units 9a and 9b. Things.

FIG. 5 is a view for explaining an embodiment of the invention according to claim 7, wherein FIG. 5 (A) is an enlarged sectional view of a portion M in FIG. 1 (A), and FIG. FIG. 2A is an enlarged cross-sectional view of the portion N, in which 16a and 16b are connectors, and portions having the same functions as those in FIG. 1 are denoted by the same reference numerals as in FIG.

The M of the shaker setup 10 shown in FIG.
5A, the pressure sensor 5 and the exciting force transmission rod 7 are screw-connected at two places via a connector 16a and locked with a nut 6, as shown in an enlarged cross-sectional view of a portion M in FIG. The two screw coupling portions are between the pressure sensor 5 and the connector 16a and between the connector 16a and the vibrating force transmission rod 7, and thus have two screw fixing portions 8a and the electric resistance measuring portion 9a. Is connected between the connector 16a and the nut 6. Also, as shown in the enlarged cross-sectional view of the portion N in FIG.
The exciting force transmitting rod 7 and the exciter 2 are also connected via the connector 16b. That is, between the vibrating force transmission rod 7 and the connector 16b, and between the connector 16b and the vibrator movable unit 3
The screw fixing portion 8b is provided at two places between
The electric resistance measuring section 9b is connected with the connector 1
6b and the nut 6 are connected.

As shown in FIG. 5, between the connector 16a and the nut 6, an electric resistance measuring section 9a is connected to the connector 16b.
Since the electric resistance measuring unit 9b is connected between the nut 6 and the nut 6, when the screw threads of the screw fixing units 8a and 8b are crushed, the nut 6 and the vibrator movable unit 3 tightened to the pressure sensor 5 are moved. It is possible to detect that the tightened nut 6 is loosened, the electrical resistance is increased, and the vibration force of the vibration exciter 2 is not transmitted to the vibration target 1 correctly.

As described above, the connector 16a is provided between the pressure sensor 5 and the rod 7, and the connector 16a is provided between the vibrator 2 and the rod 7.
b to form a screw fixing portion, and the connector 16
a, the nut 6 connects to the electrical resistance measuring unit 9a, the connector 16b, and the nut 6 connect to the electrical resistance measuring unit 9b. Therefore, a cord is attached to the pressure sensor 5 and the vibrator 2 and connected to the electrical resistance measuring units 9a, 9b. The exciter set-up 10 can be assembled without requiring any special processing to perform.

[0036]

【The invention's effect】

Advantageous Effects Corresponding to Claim 1: A vibrator, a vibrating force transmission rod for transmitting a vibrating force generated by the vibrator to a vibration target, and a vibrating force generated by the vibrator are measured. An excitation force sensor,
In an apparatus having a nut for locking the exciting force transmitting rod and the exciting force sensor, and the exciting force transmitting rod and the vibrating machine by screwing, respectively, a gap between the nut and the exciting force sensor is provided. Or an electric resistance measuring means for measuring an electric resistance value between the nut and the vibrator, and a thread of the screw-connected portion is obtained from a change in the electric resistance value measured by the electric resistance measuring means. It is detected that the vibrating force is not correctly transmitted to the object to be vibrated due to the collapse of the vibrator. When the exciting force is not correctly transmitted to the object to be excited according to the signal, this can be known by monitoring the electric resistance value. For this reason, the step of monitoring the data of the excitation force sensor and confirming the excitation force as in the related art is eliminated, and the efficiency of the experiment can be improved.

According to a second aspect of the present invention, in the vibration test apparatus according to the first aspect, when the electric resistance value becomes equal to or more than a set value, a vibration generator setup abnormality judging means for generating an abnormality signal. Is provided, it is possible to automatically determine an abnormal setup of the shaker.

According to a third aspect of the present invention, in the vibration test apparatus according to the second aspect, for the vibration exciter that operates the vibration exciter based on the abnormal signal generated from the vibration exciter setup abnormality determining means. Since the drive voltage of the vibrator is controlled by controlling the amplifier, vibration in an abnormal state can be eliminated.

According to a fourth aspect of the present invention, in the vibration test apparatus according to the second aspect, the measurement data of the vibration force sensor is measured by the abnormality signal generated by the vibration apparatus setup abnormality determination means. The control unit controls the vibration sensor amplifier to be input to the measurement device, and cuts off the input of the measurement data to the measurement device. Therefore, the measurement device can detect the vibration abnormality.

According to a fifth aspect of the present invention, in the vibration test apparatus according to the second aspect, the measuring device is controlled by the abnormal signal generated by the shaker setup abnormality determining means to invalidate the measured data. Therefore, erroneous use of measurement data that is inappropriate for excitation is eliminated, and only accurate measurement data can be extracted.

According to a sixth aspect of the present invention, in the vibration test apparatus according to the fifth aspect, the abnormal signal generated from the shaker setup abnormality determining means is input to the measuring machine, and the measuring machine is provided with a plurality of measuring machines. Since there is a means to warn the measurer of which of the shaker setups in the shaker setup has an abnormality, the vibration force, which has been conventionally performed, is displayed during or after the measurement to display the vibration state. Without confirmation
Since the measurer can concentrate on the measurement of the transfer function, the vibration experiment can be performed efficiently.

According to a seventh aspect of the present invention, in the vibration test apparatus according to the first aspect, between the vibrator and the vibrating force transmitting rod, and between the vibrating force transmitting rod and the vibrating force sensor. A connector is provided between the vibrator and the vibrating force transmitting rod, and the vibrating force transmitting rod and the vibrating force sensor are screw-connected to each other via the connector. The electric resistance between the nut and the connector to be locked and between the nut and the connector is measured to detect a change in the electric resistance. Since it is determined that the vibrating force is no longer transmitted properly, the vibrator set-up can be set up without requiring special processing such as attaching a cord to the vibrator or the vibrating force sensor.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the invention of claim 1;

FIG. 2 is a diagram for explaining an embodiment of the second and third aspects of the invention;

FIG. 3 is a block diagram for explaining an embodiment of the invention of claim 4;

FIG. 4 is a block diagram for explaining an embodiment of the invention according to claims 5 and 6;

FIG. 5 is a view for explaining an embodiment of the invention of claim 7;

FIG. 6 is a schematic configuration diagram for explaining a conventional vibration test apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Excitation object, 2 ... Exciter, 3 ... Movable part of exciter, 4
... Fixed part of shaker, 5 ... Pressure sensor, 6 ... Nut, 7 ...
Rod, 8a, 8b: Screw fixing part, 9a, 9b: Electric resistance measuring part, 10: Excitation setup, 11: Signal generating part, 1
2: shaker amplifier, 13: shaker setup abnormality determination unit, 14: pressure sensor amplifier, 15: measuring machine, 16
a, 16b ... connectors.

Claims (7)

[Claims] 1. A vibrator, a vibrating force transmission rod for transmitting a vibrating force generated by the vibrator to an object to be vibrated, and a vibrating force for measuring a vibrating force generated by the vibrator. An apparatus having a sensor, a nut for locking the vibration transmitting rod and the vibration sensor, and a screw for coupling the vibration transmitting rod and the vibrator together by screwing, the nut and the vibration sensor Between
Or, it has an electric resistance measuring means for measuring an electric resistance value between the nut and the vibrator, and the thread of the screw-coupled portion is obtained from the fluctuation of the electric resistance value measured by the electric resistance measuring means. A vibration test apparatus, which detects that the vibration force does not correctly transmit to the vibration target object due to collapse. 2. The vibration test apparatus according to claim 1, further comprising a shaker setup abnormality determination unit that generates an abnormality signal when the electric resistance value becomes equal to or greater than a set value. 3. An exciter amplifier for operating the exciter is controlled by the abnormality signal generated from the exciter setup abnormality judging means, and a drive voltage of the exciter is cut off. The vibration experiment apparatus according to claim 2, wherein 4. A vibrating force sensor amplifier that inputs measurement data from the vibrating force sensor to a measuring machine based on the abnormality signal generated from the vibrator setup abnormality determination means, and The vibration test apparatus according to claim 2, wherein an input to the measuring machine is cut off. 5. The vibration test apparatus according to claim 2, wherein the measuring device is controlled by the abnormal signal generated from the vibrating machine setup abnormality determining means to invalidate the measured data. 6. An abnormal signal generated from the shaker setup abnormality determining means is input to the measuring machine, and the measuring machine has an abnormality in any one of a plurality of shaker setups. 6. The vibration experiment apparatus according to claim 5, further comprising a warning unit. 7. A connector is provided between the vibrator and the vibrating force transmitting rod and between the vibrating force transmitting rod and the vibrating force sensor, respectively. The exciting force transmitting rod and the exciting force transmitting rod and the exciting force sensor are each screw-coupled to each other, and between the nut and the connector and between the nut and the connector for locking each screw coupling portion. Measuring a change in the electric resistance by detecting the change in the electric resistance, and judging that the excitation force is not correctly transmitted to the excitation object due to the collapse of the screw thread of the screw connection portion. Item 2. The vibration test apparatus according to Item 1.