Mechanical vibration refers to the reciprocating motion of an object or mass point near its equilibrium position. Mechanical equipment vibration is caused by repeated and regular movements of mechanical equipment. After the mechanical equipment vibrates, it will cause certain harm and reduce the working performance of the mechanical equipment. Generally, as long as the vibration of the machine (such as displacement, speed, acceleration, etc.) does not exceed the allowable standard range, the damage it suffers can be ignored. However, once the mechanical equipment exhibits abnormal vibration or the vibration amplitude exceeds the allowable range, the mechanical equipment will generate greater dynamic load and noise. Certain parts are subject to additional loads, abrasion, fatigue, rupture and other problems will be exacerbated, which will affect the working life and performance of mechanical equipment. In severe cases, it will also cause mechanical equipment parts to fail or fail prematurely. Collect vibration signals. Perform fault diagnosis based on vibration signals, accurately determine the cause and location of the fault, and take emergency measures to deal with abnormal vibration of mechanical equipment, so as to ensure the normal operation of mechanical equipment, improve the working quality and performance of mechanical equipment, and extend it Longevity, to maximize its economic value.

1. Abnormal vibration of the rotor

The rotor in the mechanical equipment is affected by the shape asymmetry, the uneven density of the materials used, and the errors generated during processing or installation, resulting in the imbalance in the radial section and the uneven mass distribution, resulting in the rotor and the shaft The loose separation between. When the rotor rotates, centrifugal force will be generated from the unbalanced amount on each radial section, and the direction of the centrifugal force will also be changed periodically with the rotation of the rotor, which will cause abnormal vibration and make the center of rotation of the rotor position Constant changes occur, causing vibration failures, which can easily cause great wear and deformation to the bearings that support the rotation of the rotor.

2. Motor vibration failure

Generally speaking, the main cause of motor vibration failure is the asymmetrical installation of the rotor during the assembly of the motor, or the uneven and unstable voltage between the rotor and the stator. When the motor runs for a long time, the rotor core and the shaft are prone to loosening. The rotor is prone to cracks between the two under the action of magnetic pulling force, causing the rotor to loosen the shaft system during the friction process of high-speed rotation, and the motor produces vibration failure. When the vibration intensity value exceeds the allowable range when the motor is running, the motor will vibrate strongly, accompanied by loud noise. If it is allowed to develop at this time, it will cause problems such as burning of the motor coil, short circuit of the motor, and serious bearing wear.

3. Vibration failure in gear drive

Gear transmission is the most commonly used transmission mechanism in mechanical equipment. In the transmission process of the gear, due to the high-speed rotation of the gear, once the fluctuation amplitude exceeds the allowable range load, the gear will accelerate wear in a short time. The wear and deformation of the gear will cause abnormal vibration of the gear and induce vibration failure. In severe cases, the tooth root will break and affect the normal operation of mechanical equipment.

4. Vibration failure of rolling bearings

Rolling bearings are commonly used transmission parts in mechanical equipment. When the rolling bearing is in operation, the passing frequency of the inner and outer rings must be kept consistent with the standard value. Once the passing frequency of the inner and outer rings is different from the standard value, it will cause abnormal vibration of the rolling bearing, and aggravate the degree of wear and deformation of the rolling bearing in a short time. Eventually induce mechanical equipment failure, affecting the safe use of mechanical equipment.

1. Waveform analysis method

The waveform analysis method analyzes the vibration signal in the time domain and the amplitude domain. By analyzing the shape of the signal spectrum curve, the parameters that characterize the curve shape are extracted, and the similarity of these parameters is used as a measure of the similarity of the spectrum. Compare these parameters with the judging criteria of mechanical vibration failures to identify the cause of the failure hidden in the vibration signal and locate the location of the failure.

The application process of the waveform analysis method in vibration diagnosis is as follows:

• Use testing instruments to collect the original vibration signals of mechanical equipment;

   

• Determine the distribution of vibration signal waveform parameters in the time domain and amplitude domain, and find the maximum amplitude;

• Analyze and determine the frequency value of each harmonic component;

   

• Calculate the phase lag and time lag of the vibration signal waveform;

   

• Perform inversion according to the distortion status of the waveform and calculate the true waveform;

   

• Calculate the attenuation coefficient of free vibration waveform and the damping value of the vibration system;

   

• Construct the correlation network between the waveform and the actual physical phenomenon, and construct the correlation network between the vibration wave and the waveform characteristics of the mechanical equipment in the normal operating state;

   

• Through correlation analysis, the similarity between the vibration waveform and the vibration waveform of the mechanical equipment in the normal operating state is calculated.Through correlation analysis, the similarity between the vibration waveform and the vibration waveform of the mechanical equipment in the normal operating state is calculated.

2. Spectrum analysis method

The spectrum analysis method is a method of transforming the time domain signal to the frequency domain and analyzing the dynamic signal in the frequency domain. It decomposes the complex time history waveform into a number of single harmonic components through Fourier transform to obtain the frequency structure of the signal and the information of each harmonic and phase. The analysis result is based on the frequency as the coordinate of each physical quantity Spectral lines and curves. The purpose is to provide conditions for solving problems such as vibration reduction, amplitude vibration, etc., to help identify the cause of the fault hidden in the vibration signal, and to locate the location of the fault.

The use process of spectrum analysis method in vibration diagnosis is as follows:

• Calculate each frequency distribution range in the dynamic vibration signal;

   

• Calculate the distribution of each frequency of the dynamic vibration signal in the amplitude domain and capacity distribution, and obtain the frequency value of the main amplitude and energy distribution;

   

• Analyze the test waveform and calculate its frequency components and amplitude to correct the test waveform;

• The frequency value, amplitude, phase angle, and various spectral densities are obtained by spectrum analysis as parameters to solve problems such as vibration elimination and amplitude vibration.

1. Data Collection

Mechanical vibration data is the basis and judgment basis for vibration fault diagnosis. The amount of data collected and the accuracy of the data determine the accuracy of fault diagnosis. Therefore, vibration data collection is a basic and indispensable link in the emergency treatment of mechanical equipment vibration. . In the actual collection of vibration data, the collection equipment used will limit the magnitude and accuracy of the collected data. When the magnitude and accuracy of the data increase, the total amount of data will also increase geometrically. This not only consumes a lot of storage space, but also greatly increases the workload of the fault diagnosis system. In order to improve the effectiveness of the collected vibration data, usually only the collection equipment is placed in the key parts where the fault often occurs, and then the industrial control computer monitoring system is used to automatically collect the data required for vibration fault diagnosis.

2. Data analysis

After collecting the fault vibration data with the collection equipment, the technicians need to sort, classify, and synthesize the data, and use spectrum analysis and other technical means to process, so as to realize the deep mining of the data and provide information for finding the cause and location of the fault. in accordance with.

3. Fault diagnosis

The ultimate goal of data collection and analysis is to realize the diagnosis of vibration faults. The diagnosis of faults requires a comprehensive judgment on the collected data. Comprehensive analysis of vibration failure data and failure judgment standards, so as to quickly and accurately determine the location and cause of the failure. Solve the problem of mechanical vibration failure at a lower cost, ensure the normal operation of mechanical equipment, and improve the efficiency of mechanical equipment.