Test device and fault settings The test device used in this paper is a hydraulic test bench, the number is a 75kW AC motor, the hydraulic pump is driven, and the speed is 1480r/min; the relief valve plays a safety role; the remote pressure regulating valve controls the pressure regulating valve to adjust the hydraulic pressure to be tested.
The loading pressure of the pump and the working pressure of other test components; the throttle valve adjusts the opening of the oil inlet of the tested pump to form a certain vacuum degree to simulate the cavitation generated by the tested pump; a large number of experimental results show that the vibration intensity of the vibration sensor is relatively large , the signal analysis effect is better; while the vibration sensor is seriously polluted by oil pressure noise, and the diagnosis effect is not ideal.
The signal of the vibration sensor is the object of analysis. In order to study the variation of the vibration parameters of the pump casing under different fault conditions, four types of faults, including cavitation fault, gear wear, side plate wear, and bearing wear, were set up in the experiment. Cavitation failure By adjusting the throttle valve to make its opening smaller, and loosening the oil inlet of the gear pump, artificially causes the oil inlet to inhale air and form cavitation. Gear wear failure is caused by grinding a tooth meshing surface of the driving gear to make its meshing curve out of shape. The side plate wear failure is caused by grinding the side plate of the oil outlet end, resulting in eccentric wear of the side plate. Bearing wear faults Bearing wear occurs by grinding a roller surface in a rolling bearing.
Wavelet packet band energy eigenvector extraction For the five working conditions of the gear pump, which are normal state, bearing wear, cavitation fault, side plate wear, and gear wear, the vibration acceleration signal of the pump casing is collected under the condition of the outlet pressure of 5MPa. Take 40 groups of 200 groups of data. First, the original sampled data is decomposed with 3-layer wavelet packets, the wavelet base is db5, each sampled data is decomposed into 8 frequency bands, the energy characteristics of each frequency band are calculated and normalized, and then the energy of 8 frequency bands is normalized to construct 8 dimensional feature vector. After the training of the SVDD model is completed, the test samples are input into the above model to check its performance.
Common load-bearing calculation methods for rolling bearings
Rolling bearings are commonly used types of bearings. In general, rolling bearings are divided into rated dynamic load and rated static load. The load that can be endured when the rated life is 1 million revolutions is the rated dynamic load C. When the sum of the plastic deformation at the contact of the rolling element with the largest load and the raceway reaches 1/10,000 of the rolling element diameter, the load that can be supported is the rated static load C0. Relatively speaking, the load capacity of rolling bearings is superior to that of plain bearings. How to calculate the rolling bearing load? Are there any calculation methods?
Calculation method of rolling bearing load:
1. Determine the component forces in the circumferential, radial and axial directions of the main engine drive system as an external load;
2. Integrate these component forces into two forces parallel to the axis direction and perpendicular to the axis direction, namely axial force and centripetal force;
3. According to the balance condition of the fulcrum of the shaft, find the support reaction force of each fulcrum, that is, the external load on the bearing;
4. According to the size and proportion of the centripetal force and axial force on the support, determine the type of bearing suitable for bearing this external force;
5. Convert these external forces into the equivalent dynamic load applied to the bearing according to a certain law, for the calculation of bearing fatigue life;
6. Sometimes these external forces should be converted into the equivalent static load applied to the bearing according to another law, so as to check whether the bearing is permanently deformed.
Assembly method of sliding bearing and shaft
Bearings are the components used to support and the parts used to support the rotation on the shaft. The types of bearings are divided according to friction properties: sliding bearings and rolling bearings; according to the direction of load: radial bearings, push bearings, radial thrust bearings, etc.
Assembly of plain bearings
Sliding bearing is a kind of sliding friction bearing, which is characterized by stable operation, reliability and low noise, and can withstand heavy loads and large impact loads.
Assembly of integral plain bearings
Integral sliding bearings, commonly known as bushings, are also the simplest form of sliding bearings. They are mainly assembled by pressing and hammering. Hot-loading is used in special occasions. Most bushings are made of copper or cast iron. Care should be taken when installing, and it can be assembled by hitting with a wooden hammer or a hammer block. Whether it is knocked in or pressed in, it must be prevented from tilting. After assembly, the oil groove and oil hole should be in the required position.
Bearings deformed after assembly should be trimmed for inner holes. Smaller ones can be cut with a reamer, while larger ones can be scraped. At the same time, pay attention to control the matching clearance with the shaft within the tolerance range. In order to prevent the shaft sleeve from rotating during operation, the contact surface between the shaft sleeve and the box body is equipped with positioning pins or seam screws. Due to the different hardness of the box body and the shaft sleeve material, when drilling, it is easy to make the drill bit bias to the side of the soft material.
Solution: First, use a sample punch to punch against the hard material before drilling, and second, use a short drill bit to increase the rigidity of the drill bit when drilling.