Abstract: In order to explore the reliability of outer spherical bearings in wide applications, a life testing machine for outer bearings units was developed. This article elaborates on the main structure of the testing machine, the working principle of the loading system, and the main functions of the measurement and control system.

Keywords: bearing unit ; Testing machine; Load spectrum; Hydraulic loading; Measurement and control system

The external bearings unit has a compact structure, reliable sealing, and easy assembly and disassembly, mainly suitable for low-speed and heavy-duty applications. It has a wide range of applications in fields such as agriculture, textiles, mining, metallurgy, chemical engineering, and transportation machinery. At present, with the continuous expansion of demand and application scope for outer spherical bearings, the reliability requirements for the service life of outer spherical bearings are becoming increasingly strict for manufacturers and bearing users. Conducting service life tests for outer spherical bearings has become a necessity in the industry. For this purpose, we have designed an automatic measurement and control testing device - a seat outer spherical bearing life testing machine - that can apply load spectrum and velocity spectrum to the test bearings.

1 Main technical parameters of the testing machine

The testing machine is designed according to the following parameters:

1) Test bearing inner diameter: Φ50—Φ100mm。

2) The Z-large radial load of the testing machine is 100KN, with an error of ≤± 2% FS.

3) Testing machine Z high speed: 3500r/min, error ≤ ± 2% FS.

4) Measurement and control methods: microcomputer automatic control, automatic monitoring, automatic alarm shutdown, and automatic recording.

5) Measurement parameters: temperature, speed, host current, vibration, and radial load.

2 Characteristics of the main structure of the testing machine

The main structure is shown in Figure 1, and the shaft system is the core part of the entire test device. The test spindle adopts a simply supported beam structure, and two sets of test bearings are symmetrically arranged at both ends of the spindle. Temperature sensors and vibration sensors are installed on the bearing seat to monitor the temperature of the outer ring of the bearing and the vibration state of the shaft system, respectively. In order to improve the stiffness of the test spindle, it is necessary to design the span l between the two bearings reasonably. Taking the test bearing UCP213 as an example: its rated dynamic load Cr is 44kN. According to the rolling bearing life and reliability test regulations, the test equivalent load Pr is taken as 20kN, and the elastic modulus E of the shaft is 210GPa. Based on the deformation formula and design principle of the simply supported beam (as shown in Figure 2), the Z-deflection of its main shaft can be obtained; Where I is the moment of inertia of the main axis,, Take 65mm for D. Then; Considering the width and adjustability of the outer spherical bearing, as well as the interchangeability of testing with other specifications of bearings, a span of 240mm was selected between the two test bearings.

The power source of the test machine is an AC variable frequency motor, which drives the transmission shaft (transmission device) to rotate. The transmission shaft then drives the test spindle through a coupling, which uses high-strength nylon rope connection to greatly reduce the external interference caused by the misalignment between the spindle and the transmission device. According to the technical parameters of the testing machine, the radial load of Z is 100kN. The hydraulic cylinder FA-150-R60-S50-70k is selected, and the force of the hydraulic cylinder is applied to the bearing sleeve through a force sensor. The load is applied to the outer spherical bearing through the bearing bearing and main shaft. The load size is determined by the computer load spectrum command, and closed-loop control is achieved through the force sensor and proportional pressure reducing valve in the hydraulic system. When testing other specifications of bearings, simply replace the adjustment pad, main shaft, and parts that fit with the shaft system to conduct the test.

The main structure of this testing machine meets the working requirements of external spherical bearings, with high reliability, simple operation, and convenience.

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1. Variable frequency motor; 2. Hydraulic cylinder; 3. Force sensor; 4. Workbench; 5. Adjust the cushion block; 6. Spindle; 7. Vibration sensors (two sets); 8. Bearing sleeve; 9. Temperature sensors (four sets); 10. Load bearings; 11. Outer bearings unit; 12. Couplings; 13. Transmission device

Figure 1 Structural diagram of the experimental subject

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Figure 2: A simply supported beam

3 Loading System

The loading system adopts proportional hydraulic technology for loading, and the hydraulic principle is shown in Figure 3. The hydraulic loading system consists of components such as oil pump, filter, relief valve, proportional pressure reducing valve, cooler, and reversing valve. During operation, two pressure gauges display the oil pressure behind the pump and the hydraulic cylinder, respectively. The load size is controlled by a proportional pressure reducing valve. According to the load requirements of the tested bearing, the load size, loading time, and speed are input into the load spectrum. Through automatic control by the computer, loading can be achieved. The load spectrum can be compiled according to different experimental requirements.

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1. Oil pump; 2. Filter; 3. Overflow valve; 4. Proportional valve; 5. Electromagnetic directional valve; 6. Load the oil cylinder; 7. Pressure gauge; 8. Cooler

Figure 3 Hydraulic schematic diagram

4 Measurement and Control System

The measurement and control system is an important part of the entire testing machine, consisting of a computer system, an electrical control system, a loading control system, a variable frequency drive system, and a sensor measurement system. Through measurement and control software and RS-485 communication module, parameters such as host speed, current, and voltage can be monitored. By using temperature, vibration, and pressure sensors, signals such as bearing temperature, vibration, and load can be monitored. The entire measurement and control system can automatically control the operation program of the testing machine, accurately conduct tests according to the preset test speed spectrum and load spectrum, and automatically measure and record the test parameters. If any abnormal situation occurs during the experiment, it will automatically sound an alarm, shut down, and record the reason and time of the alarm.

5 Conclusion

The testing machine has a simple structure and is easy to assemble and disassemble; Loading sensitivity and high accuracy; All are automatically controlled by computers and do not require personnel supervision. Its main function is to assess the service life of the outer bearings unit, simulate the main performance of the bearing under load and operating conditions, identify the defects and deficiencies of the bearing through analysis of the test results, improve processing technology and design parameters, thereby enhancing the quality and reliability of the bearing application.

2025 April 2nd Week FK Product Recommendation:

Flange Cartridge Units:

They are units of rigid cast iron housings with piloted flange cartridge and wider inner ring bearing inserts.

Standard painting in green (other colors are available for choices).

Standard duty (FC200) and medium duty (FCX) are available for this series.

End caps by pressed steel are capable of protecting against external polution and dusts.

The self-aligning ability of the ball bearings can compensate for slight static mis-alignemnt of the shaft. The bearing inserts are locked onto the shaft by means of set screws, eccentric locking collars, adapter sleeves and concentric locking collars etc.

Lubricants filled inside the spherical ball bearing inserts can be standard grease, low/hight temperature grease and food grade grease.

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