CN109323831B - A modal test device for slender rotating shafts based on the sudden release excitation method of preload - Google Patents

Abstract

The invention belongs to the technical field of modal testing, and in particular relates to a modal testing device for an elongated rotating shaft based on a preloaded sudden release excitation method. Including motor, sliding bearing, equal force hammer, slender shaft, disc, rope, weight, collector; the motor is connected to the slender shaft, there are two sliding bearings and a disc on the slender shaft, and the disc is located in the slender shaft At the far right end of the shaft, the equal-force hammer is located between two sliding bearings, and the equal-force hammer is connected to the weight by a rope. When the device is working, the acquisition instrument is connected to the equivalent force hammer, and two eddy current sensors are installed on the slender shaft. The two eddy current sensors are located on both sides of the equivalent force hammer. The two eddy current sensors are also connected to the acquisition instrument, which is connected to the computer. The slender rotating shaft modal test device based on the preload sudden release excitation method designed by the invention can more accurately measure the modal of the slender shaft under the condition of ensuring oil film integrity and motion, and has broad application prospects.

Description

A modal test of a slender rotating shaft based on a sudden release excitation method of preload device

technical field

The invention belongs to the technical field of modal testing, and in particular relates to a modal testing device for an elongated rotating shaft based on a preloaded sudden release excitation method.

technical background

Modal testing is an important means to obtain the vibration characteristics of structural parts, which plays a great role in predicting and diagnosing the faults of structural parts. In order to analyze the vibration characteristics of the slender rotating shaft, the modal test of the slender rotating shaft is required . The traditional modal testing method is the hammering excitation modal testing method, that is, the shaft segment is hit with a force hammer, the vibration responses at different positions are collected by the sensor, and the testing method of the shaft system modal is obtained based on the software analysis. However, if the traditional hammering excitation method is used in the modal test experiment of the slender rotating shaft, the phenomenon of poor coherence and double-click will occur during data acquisition, resulting in unsatisfactory experimental results of the modal test. After analysis, if the hammer excitation modal method is used to test the modal of the slender rotating shaft, the following problems will exist:

1. Poor coherence per tap. Since the shaft is a slender shaft, and the diameter of the shaft is similar to the size of the hammer head of the force hammer, the excitation at the same angle and striking point cannot be guaranteed for each stroke; and the shaft can rotate freely in the sliding bearing, with The shaft is deflected and the orientation of the accelerometer fixed to the shaft segment changes. The above factors lead to particularly poor percussion coherence of the force spectrum during the test.

2. It is easy to double-click. The shaft is a slender shaft, which is equivalent to a shaft with a large span, and its rigidity is small in the direction perpendicular to the axis. Therefore, double-clicks occur frequently during the test, resulting in low test efficiency.

3. No oil film is formed on the bearing. Since the traditional hammer excitation modal method is carried out under static conditions, no oil film is formed on the bearing. During the working process, the oil film provides support for the shaft system. 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. Only when the system mode after the oil film is established can the accurate system response calculation be performed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a slender rotating shaft modal test device based on the preload sudden release excitation method capable of accurately testing the slender rotating shaft mode.

A modal test device for a slender rotating shaft based on a sudden release excitation method of preload, including a motor, a sliding bearing, an equal-force hammer, a slender shaft, a disc, a rope, a weight, and a collector; the motor is connected to the slender shaft , There are two sliding bearings and a disc on the slender shaft, the disc is located at the far right end of the slender shaft, the equivalent force hammer is located between the two sliding bearings, and the equivalent force hammer is connected to the weight by a rope.

The modal test device for a slender rotating shaft based on a sudden release excitation method of preload, the equivalent force hammer includes a nut, a force sensor, a counterweight, a bearing bush, a nylon pad, a spring, the force sensor is located at the left end of the counterweight, and the force sensor is located at the left end of the counterweight. Fixed by nut, the equal force hammer is fixed on the slender shaft through the right hook of the counterweight, there are bearing bushes and nylon pads between the slender shaft and the hook, and the right side of the hook is connected with a spring.

The slender rotating shaft modal test device based on the sudden release excitation method of preloading, when the device is working, the acquisition instrument is connected to the equivalent force hammer, and two eddy current sensors are installed on the slender shaft, and the two eddy current sensors are respectively Located on both sides of the equal force hammer, two eddy current sensors are also connected to the collector, and the collector is connected to the computer.

The beneficial effects of the present invention are:

The present invention takes into account the difference between the shaft system at rest and when it moves, and designs an equivalent force hammer to ensure that excitation can be provided and modal testing can be performed when the shaft system rotates. Considering the influence of the oil film stiffness on the modal test, the test device designed in the present invention can perform the modal test on the shafting under the condition that the oil film is not damaged. At the same time, the principle of equivalent force hammer ensures that each knock is excited at the same angle and tapping point, the slender shaft can rotate freely in the sliding bearing, the slender shaft will not be deflected due to excitation, and the fixed acceleration sensor The direction does not change, thus improving the coherence of hammer strikes. A slender rotating shaft modal test device based on the preload sudden release excitation method designed in the present invention can more accurately measure the slender shaft modal under the condition of ensuring the integrity of the oil film and the motion state.

Description of drawings

Fig. 1 is the principle schematic diagram of the present invention;

Fig. 2 is the principle diagram of the equal effect hammer of the present invention;

Fig. 3 is the connection schematic diagram of the present invention;

FIG. 4 is a schematic diagram of the position at the end of the equal-effect hammer experiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in FIG. 1, it is a schematic diagram of the principle of a modal testing device for an elongated rotating shaft based on a preloaded sudden release excitation method designed in the present invention; it includes a motor 1, a sliding bearing 2, an equivalent force hammer 3, an elongated shaft 4. Sliding bearing 5, disc 6, rope 7, rope 8, weight 9, collecting instrument 16; motor 1 is connected to slender shaft 4, there are sliding bearings 2, 5 and disc 6 on the slender shaft, and the disc is located in the At the rightmost end of the elongated shaft, the equal-force hammer 3 is located between the two sliding bearings, and the equal-force hammer is connected to the weight 9 through a rope 8 .

As shown in FIG. 2, it is a schematic diagram of the equivalent effect hammer of a slender rotating shaft modal test device based on a preloaded sudden release excitation method designed by the present invention; FIG. 4 is a preload-based design of the present invention Schematic diagram of the position at the end of the equivalent force hammer experiment of the slender rotating shaft modal test device using the sudden load release excitation method. The equivalent force hammer 3 includes a nut 10, a force sensor 11, a counterweight 12, a bearing bush 13, a nylon pad 14, a spring 15, the force sensor 11 is located at the left end of the counterweight 12, the force sensor is fixed by the nut 10, and the equivalent force hammer passes through the right hook of the counterweight It is fixed on the slender shaft 4, there is a bearing bush 13 and a nylon pad 14 between the slender shaft and the draw hook, and a spring 15 is connected to the right side of the draw hook.

As shown in FIG. 3, it is a schematic diagram of the connection of a slender rotating shaft modal testing device based on the preload sudden release excitation method designed by the present invention; when the device is in operation, the collector 16 is connected to the equivalent force hammer 3, and the elongated shaft Two eddy current sensors 18 are installed on the 4, and the two eddy current sensors are respectively located on both sides of the equivalent force hammer. The two eddy current sensors are also connected to the acquisition instrument 16, and the acquisition instrument is connected to 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 during the test or the rope 8 for pulling the weight is broken by fire, the preload of the shaft system is suddenly released at this time, which is used as the excitation of the shaft system to carry out the modal. test. Equivalent force hammer 3 is the most critical component in the whole test equipment. The counterweight 12 determines the magnitude of the impact force. The counterweight 12 can be selected in various specifications. When the counterweight 12 is large, the input force amplitude of the equivalent force hammer 3 The value is large, and vice versa; the force sensor 11 can measure the force fluctuation amount acting on the shaft system when F2=0 instantaneously, and the force signal is collected by the acquisition device 16 for modal calculation; F2 is the weight of the weight 9 , as the preload of the shaft system; the size of F1 is the gravity of the equivalent force hammer 3, and its action line passes through the center of gravity of the equivalent force hammer 3; The friction between them is small and can slide smoothly; the nylon pad 14 affects the pulse width of the knocking force, and materials of different materials and different hardness can be selected to obtain the ideal impact input force; the initial state of the spring 15 is stretched, and its function is to prevent When F2=0, that is, after the rope 8 is cut, the spring 15 is restored to its original length to prevent the equal-force hammer 3 from striking the shaft for many times.

Select a weight of appropriate weight and connect the test instrument. After the instrument is connected and the debugging and testing system can work normally, you can start the test:

Step 1: Check the power supply of the test site; after setting parameters such as channel, sensor sensitivity, trigger, etc. on the test computer, the second step can be performed after the test model is established;

The second step: start the motor, let the motor speed rise to a suitable speed, and wait for a stable oil film to be established at the sliding bearing, then proceed to the second step;

Step 3: Check again whether the test system is in a normal state. If it is normal, use scissors to cut or burn the rope 8 for lifting heavy objects with fire. At this time, the load on the shaft system will be released suddenly, and the stiffness of the oil film will be stimulated. Shafting mode under support. After cutting the rope 8, the equal-force hammer 3 is completely separated from the rotating shaft under the action of the spring 15, and will not cause multiple knocks on the shaft system;

Step 4: Check the rationality of the test results at the test site, if there is no problem, perform the next measurement or end the test;

Step 5: Take back the test equipment and organize the test site;

The above invention provides innovative ideas for modal testing of slender rotating shafts, and the proposed ideas and similar methods all belong to the scope of coverage of this patent.

Claims (1)

1. A slender rotating shaft modal test device based on the sudden release excitation method of preloading, comprising a motor, a sliding bearing, an equal force hammer, an elongated shaft, a disc, a rope, a heavy object, a collector; it is characterized in that : The motor is connected to the slender shaft, there are two sliding bearings and a disc on the slender shaft, the disc is located at the far right end of the slender shaft, the equivalent force hammer is located between the two sliding bearings, and the equivalent force hammer is connected to the heavy objects by ropes; The equivalent force hammer includes a nut, a force sensor, a counterweight, a bearing bush, a nylon pad, and a spring. The force sensor is located at the left end of the counterweight, and the force sensor is fixed by the nut. The equivalent force hammer is fixed on the slender shaft by the hook on the right side of the counterweight. There are bearing bushes and nylon pads between the long shaft and the hook, and the right side of the hook is connected to a spring; When the device is in operation, the collector is connected to the equivalent force hammer, two eddy current sensors are installed on the slender shaft, the two eddy current sensors are located on both sides of the equivalent force hammer, and the two eddy current sensors are also connected to the collector. connect computer; The heavy object is used as the preload of the shaft system. When the rope is suddenly cut or burned by fire during the test, the preload of the shaft system is suddenly released, and the modal test is carried out as the excitation of the shaft system; Equivalent impact hammer is the most critical component in the whole test equipment. The counterweight determines the magnitude of the impact force. The counterweight adopts various specifications. The force sensor measures the amount of force fluctuation acting on the shaft system when F2=0 instantaneously. , the force signal is collected by the acquisition instrument for modal calculation; F2 is the weight of the heavy object, which is used as the preload of the shaft system; the size of F1 is the gravity of the equivalent force hammer, and its action line passes through the center of gravity of the equivalent force hammer; Fitted with the surface of the slender shaft, the friction between the bearing bush and the slender shaft is small and can slide smoothly; the nylon pad affects the pulse width of the knocking force, and materials with different materials and different hardnesses are used to obtain the ideal impact input force; the initial state of the spring In order to stretch, when the rope is cut, the spring returns to its original length to prevent the shaft from being struck repeatedly by the equal force hammer.

Images