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CN109323831B - Elongated rotating shaft modal test device based on preload sudden release excitation method - Google Patents

Elongated rotating shaft modal test device based on preload sudden release excitation method Download PDF

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Publication number
CN109323831B
CN109323831B CN201811033562.0A CN201811033562A CN109323831B CN 109323831 B CN109323831 B CN 109323831B CN 201811033562 A CN201811033562 A CN 201811033562A CN 109323831 B CN109323831 B CN 109323831B
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shaft
equivalent force
preload
slender
force hammer
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CN109323831A (en
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卢熙群
周帅宇
李玩幽
率志君
焦殿林
刘伟
鲁涵峰
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Harbin Engineering University
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Harbin Engineering University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M7/00Vibration-testing of structures; Shock-testing of structures
    • G01M7/02Vibration-testing by means of a shake table

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Abstract

The invention belongs to the technical field of modal testing, and particularly relates to a slender rotating shaft modal testing device based on a preload sudden release excitation method. The device comprises a motor, a sliding bearing, an equivalent force hammer, a slender shaft, a disc, a rope, a heavy object and a collecting instrument; the motor is connected with the slender shaft, the slender shaft is provided with two sliding bearings and a disc, the disc is positioned at the rightmost end of the slender shaft, the equivalent force hammer is positioned between the two sliding bearings, and the equivalent force hammer is connected with a heavy object through a rope. When the device works, the acquisition instrument is connected with the equivalent force hammer, the slender shaft is provided with two eddy current sensors, the two eddy current sensors are respectively positioned on two sides of the equivalent force hammer, the two eddy current sensors are also connected with the acquisition instrument, and the acquisition instrument is connected with a computer. The elongated rotating shaft modal test device based on the preload sudden release excitation method can accurately test the modal of the elongated shaft under the condition of ensuring the integrity of the oil film and the motion state, and has wide application prospect.

Description

Elongated rotating shaft modal test device based on preload sudden release excitation method
Technical Field
The invention belongs to the technical field of modal testing, and particularly relates to a slender rotating shaft modal testing device based on a preload sudden release excitation method.
Technical Field
The modal test is an important means for obtaining the vibration characteristics of the structural member, has a great effect on predicting and diagnosing the faults of the structural member, and needs to test the mode of the slender rotating shaft in order to analyze the vibration characteristics of the slender rotating shaft. The conventional mode test generally adopts a hammering excitation mode test method, namely: and knocking the shaft section by using a force hammer, collecting vibration responses at different positions by using a sensor, and obtaining a test method of a shafting mode based on software analysis. However, if the conventional hammering excitation method is adopted in the modal test experiment of the slender rotating shaft, phenomena such as poor coherence and double hammering can occur during data acquisition, so that the experimental result of the modal test is not ideal. Through analysis, the following problems exist if the mode of the slender rotating shaft is tested by adopting a hammering excitation mode method:
1. each tap has poor coherence. Because the shaft is a slender shaft, the diameter of the shaft is close to the size of the hammer head of the force hammer, and excitation at the same angle and the same knocking point cannot be guaranteed during each knocking; and the shaft can freely rotate in the sliding bearing, the shaft can deflect along with the knocking, and the direction of the acceleration sensor fixed on the shaft section can change. The above factors result in particularly poor tap coherence of the force spectrum during the test.
2. Double-click is easy to occur. The shaft is a slender shaft, is equivalent to a shaft with large span, and has smaller rigidity in the direction vertical to the axis; meanwhile, the force hammer used in the test is a 'large' force hammer relative to a shafting. Therefore, the frequency double-click condition is generated in the test process, so that the test efficiency is low.
3. No oil film is formed at the bearing. Because the traditional hammering excitation mode measurement method is carried out in a static state, an oil film is not formed at the bearing. In the working process, the oil film provides a supporting function for the shafting. Therefore, the oil film stiffness should be considered in the modal test, and the oil film stiffness has a significant effect on the low-order modes. And only if the system mode after the oil film is established is obtained, accurate system response calculation can be carried out.
Disclosure of Invention
The invention aims to provide a slender rotating shaft modal testing device based on a preload sudden release excitation method, which can accurately test the modal of a slender rotating shaft.
A long and thin rotating shaft modal test device based on a preload sudden release excitation method comprises a motor, a sliding bearing, an equivalent force hammer, a long and thin shaft, a disc, a rope, a weight and a collecting instrument; the motor is connected with the slender shaft, the slender shaft is provided with two sliding bearings and a disc, the disc is positioned at the rightmost end of the slender shaft, the equivalent force hammer is positioned between the two sliding bearings, and the equivalent force hammer is connected with a heavy object through a rope.
The equivalent force hammer comprises a nut, a force sensor, a balance weight, a bearing bush, a nylon pad and a spring, wherein the force sensor is located at the left end of the balance weight, the force sensor is fixed through the nut, the equivalent force hammer is fixed on an elongated shaft through a balance weight right drag hook, the bearing bush and the nylon pad are arranged between the elongated shaft and the drag hook, and the drag hook right is connected with the spring.
According to the device for testing the long and thin rotating shaft modal based on the preload sudden release excitation method, when the device works, the acquisition instrument is connected with the equivalent force hammer, the long and thin shaft is provided with the two eddy current sensors, the two eddy current sensors are respectively positioned on two sides of the equivalent force hammer, the two eddy current sensors are also connected with the acquisition instrument, and the acquisition instrument is connected with the computer.
The invention has the beneficial effects that:
the invention takes the difference between the static state and the motion of the shafting into consideration, designs the equivalent force hammer, and ensures that the excitation can be provided under the condition that the shafting rotates to carry out modal test. Considering the influence of oil film rigidity on modal testing, the testing device designed by the invention can perform modal testing on the shafting under the condition of ensuring that the oil film is not damaged. Meanwhile, the equivalent force hammer action principle ensures that the slender shaft can be freely rotated in the sliding bearing when being excited at the same angle and at the same knocking point in each knocking process, the slender shaft cannot deflect due to the excitation, and the direction of the fixed acceleration sensor cannot be changed, so that the knocking coherence of the force hammer is improved. The elongated rotating shaft modal test device based on the preload sudden release excitation method can more accurately test the elongated shaft modal under the condition of ensuring the integrity of an oil film and a motion state.
Drawings
FIG. 1 is a schematic diagram of the principles of the present invention;
FIG. 2 is a schematic diagram of an equivalent force hammer of the present invention;
FIG. 3 is a schematic diagram of the connection of the present invention;
fig. 4 is a schematic diagram of the position of the equivalent force hammer at the end of the test according to the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a principle of a slender rotating shaft modal testing device based on a preload sudden release excitation method, which is designed for the invention; the device comprises a motor 1, a sliding bearing 2, an equivalent force hammer 3, a slender shaft 4, a sliding bearing 5, a disc 6, a rope 7, a rope 8, a weight 9 and an acquisition instrument 16; the motor 1 is connected with a slender shaft 4, sliding bearings 2 and 5 and a disc 6 are arranged on the slender shaft, the disc is positioned at the rightmost end of the slender shaft, an equivalent force hammer 3 is positioned between the two sliding bearings, and the equivalent force hammer is connected with a heavy object 9 through a rope 8.
As shown in fig. 2, an equivalent force hammer principle diagram of a slender rotating shaft modal testing device based on a preload sudden release excitation method is designed for the invention; FIG. 4 is a schematic diagram of an equivalent force hammer experiment end position of a slender rotating shaft modal testing device based on a preload sudden release excitation method. The equivalent force hammer 3 comprises a nut 10, a force sensor 11, a balance weight 12, a bearing bush 13, a nylon pad 14 and a spring 15, wherein the force sensor 11 is located at the left end of the balance weight 12, the force sensor is fixed through the nut 10, the equivalent force hammer is fixed on the slender shaft 4 through a balance weight right drag hook, the bearing bush 13 and the nylon pad 14 are arranged between the slender shaft and the drag hook, and the drag hook right is connected with the spring 15.
FIG. 3 is a schematic connection diagram of a modal testing device for an elongated rotating shaft based on a preload sudden release excitation method, which is designed for the invention; when the device works, the acquisition instrument 16 is connected with the equivalent force hammer 3, the slender shaft 4 is provided with two eddy current sensors 18 which are respectively positioned at two sides of the equivalent force hammer, the two eddy current sensors are also connected with the acquisition instrument 16, and the acquisition instrument is connected with the computer 17.
The weight 9 is used as the preload of the shaft system, when the rope 8 for pulling the weight is suddenly cut off or burnt by fire in the test, the preload of the shaft system is suddenly released at the moment, and the preload is used as the excitation of the shaft system for carrying out the modal test. The equivalent force hammer 3 is the most critical component in the whole test equipment, wherein the counterweight 12 determines the amplitude of impact force, the counterweight 12 can adopt various specifications, when the counterweight 12 is large, the input force amplitude of the equivalent force hammer 3 is large, and vice versa; the force sensor 11 can measure the force fluctuation quantity acting on the shafting when the F2 is equal to 0, and the force signal is collected by the collector 16 for modal calculation; f2 is the weight of the weight 9 as the preload of the shafting; the magnitude of F1 is the gravity of the equivalent force hammer 3, and the action line of the F1 passes through the gravity center position of the equivalent force hammer 3; the bearing bush 13 is attached to the surface of the slender shaft 4, and the bearing bush 13 and the slender shaft 4 have small friction and can slide smoothly; the nylon cushion 14 influences the pulse width of the knocking force, and materials with different materials and different hardness can be selected to obtain ideal impact input force; the spring 15 is initially in a stretched state, and the spring 15 is used for preventing the equivalent weight 3 from knocking the shafting multiple times by restoring the original length after the rope 8 is sheared when F2 is equal to 0.
And selecting a weight with proper weight, and connecting the weight with a test instrument. After the instrument connection is completed and the debugging test system can normally work, the test can be started:
the first step is as follows: checking the power supply condition of a test site; after the parameters such as the channel, the sensor sensitivity, the trigger and the like are set on the testing computer, a second step can be carried out after a testing model is established;
secondly, the following steps: starting the motor, and when the rotating speed of the motor is increased to a proper rotating speed and waiting for a stable oil film to be established at the sliding bearing, performing the second step;
the third step: and checking whether the test system is in a normal state again, if so, cutting off the rope 8 for lifting the heavy object by using scissors or burning off the rope by using fire, and at the moment, suddenly releasing the load loaded on the shafting to excite the shafting mode under the support of the oil film rigidity. After the rope 8 is cut off, the equivalent force hammer 3 is completely separated from the rotating shaft under the action of the spring 15, and multiple times of knocking on a shaft system cannot be formed;
the fourth step: checking the reasonability of the test result on the test site, and carrying out the next measurement or finishing the test if no problem exists;
the fifth step: recovering the test instrument and tidying the test site;
the invention provides an innovative idea of the mode test of the slender rotating shaft, and the idea of the mode test and the similar method are all covered by the patent.

Claims (1)

1. A long and thin rotating shaft modal test device based on a preload sudden release excitation method comprises a motor, a sliding bearing, an equivalent force hammer, a long and thin shaft, a disc, a rope, a weight and a collecting instrument; the method is characterized in that: the motor is connected with the slender shaft, the slender shaft is provided with two sliding bearings and a disc, the disc is positioned at the rightmost end of the slender shaft, the equivalent force hammer is positioned between the two sliding bearings, and the equivalent force hammer is connected with a heavy object through a rope;
the equivalent force hammer comprises a nut, a force sensor, a balance weight, a bearing bush, a nylon pad and a spring, wherein the force sensor is positioned at the left end of the balance weight, the force sensor is fixed through the nut, the equivalent force hammer is fixed on the slender shaft through a right drag hook of the balance weight, the bearing bush and the nylon pad are arranged between the slender shaft and the drag hook, and the right side of the drag hook is connected with the spring;
when the device works, the acquisition instrument is connected with the equivalent force hammer, two eddy current sensors are arranged on the slender shaft and are respectively positioned at two sides of the equivalent force hammer, the two eddy current sensors are also connected with the acquisition instrument, and the acquisition instrument is connected with a computer;
the weight is used as the preload of the shaft system, when the rope for pulling the weight is suddenly cut off or burned off by fire in the test, the preload of the shaft system is suddenly released at the moment, and the preload is used as the excitation of the shaft system for modal test; the equivalent force hammer is the most key component in the whole test equipment, wherein the balance weight determines the amplitude of impact force, the balance weight is in various specifications, the force sensor measures the force fluctuation quantity acting on a shaft system when F2=0, and a force signal is collected by the collection instrument and used for modal calculation; f2 is the weight of the weight and is used as the preload of the shafting; f1 is the gravity of the equivalent force hammer, and the action line passes through the gravity center position of the equivalent force hammer; the bearing bush is attached to the surface of the slender shaft, and the bearing bush and the slender shaft have small friction and can slide smoothly; the nylon cushion influences the pulse width of the knocking force, and materials with different materials and different hardness are selected to obtain ideal impact input force; the spring is stretched in the initial state, and after the rope is cut off, the spring recovers the original length to prevent the equivalent force hammer from knocking the shafting for multiple times.
CN201811033562.0A 2018-09-05 2018-09-05 Elongated rotating shaft modal test device based on preload sudden release excitation method Active CN109323831B (en)

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CN101907523B (en) * 2010-01-08 2012-02-08 浙江吉利汽车研究院有限公司 Rigid body mode testing method for powertrain suspension system under loading condition
CN103308263B (en) * 2013-05-16 2016-03-09 哈尔滨工程大学 Large-sized structural parts mould measurement exciting bank
CN203732234U (en) * 2014-01-16 2014-07-23 海洋化工研究院有限公司 Drop-hammer impact testing machine of coating sheet material
CN103994869B (en) * 2014-05-21 2016-08-31 东北大学 A kind of method of testing of thin wall cylindrical hull structure component experimental bench
CN108072488A (en) * 2016-11-17 2018-05-25 华晨汽车集团控股有限公司 The device and test method of a kind of indirectly testing shafting torsion stiffness and mode
CN106895971B (en) * 2017-04-12 2018-04-06 北京航空航天大学 A kind of method for measuring slender axles rotor internal damping
CN107036813A (en) * 2017-05-31 2017-08-11 哈尔滨工程大学 A kind of multi-functional shafting experimental rig based on Gear Planet Transmission
CN107356419B (en) * 2017-07-18 2019-08-02 厦门大学 It is a kind of for measuring the experimental method of rope damping parameter
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