Reliability test-bed to ensure the reliability of

  • Detail

Wanshan Special vehicle manufacturer undertakes the research and production of special heavy-duty wheels and axle assembly components, as well as the re inspection bench test of externally purchased wheels and axle assemblies. Since the establishment of br2.5 wheel axle car room in our factory in 2002, serious quality problems such as overheating of wheels, wheel locking, cracking of axle housing and so on have been found. In order to ensure the assembly quality of subsequent products and stabilize the production process, we carry out reliability tests on special heavy-duty wheels and axles according to the requirements of the technical conditions of this type of main reducer. The test method refers to the current China's automotive industry standard qc/t vehicle drive bridge bench test method, but this standard is only applicable to small vehicles with axle load of less than 8t, while the product payload produced by our factory is heavy-duty axles of more than t, Therefore, this standard cannot be directly applied to the life test of our products. We must find a method that can adapt to the life test of heavy axle products produced by our factory to ensure the service life of existing wheels and axles, ensure product quality, and provide a scientific basis for the performance and fatigue life test of newly developed wheels and axles in the future. To this end, we have developed a set of reliability test-bed for heavy-duty axle and used it in the actual inspection work, and achieved good results

system composition

this system uses secondary hydraulic adjusting elements to drive and load special vehicles. The system includes four parts: constant pressure oil source and pipeline unit (primary element), loading unit (secondary element), control system, mechanical support and test platform (the system structure of the test platform is shown in Figure 1). The function of primary element is to provide constant voltage circuit for the whole loading secondary element, including high voltage circuit and low voltage circuit. The secondary element realizes the simulation of driving and loading of the transmission system, in which the power shaft analog driving unit (analog diesel engine) is generally in the speed control mode, and it is only switched to torque control when simulating downhill operation, and other analog loading units are generally in the torque control mode. The control system completes the control of the whole system, including speed and torque control of secondary components, system state overrun and protection, system logic control, system state detection and parameter measurement. The mechanical support and test platform provide the support and connection of the loading test object, transmission and driving and loading secondary elements

test process

since the working efficiency of all transmissions on the test bench and the working efficiency of the second axle reducer are unknown, the empirical value of 0.96 is considered in the theoretical calculation process. In the actual loading process, there is a great error between the torque meter display value and the theoretical calculation value. At the same time, because the specimen is damaged many times in the test, it is difficult to believe the accuracy of the test results. However, there is no ready-made standard for the loading test of heavy-duty axle in our country, so we collect the test data of each time, and grasp its change law through statistical analysis and prediction of the test data, Finally, the reliability test of heavy-duty vehicle and axle was completed. Finally, the reliability test of heavy-duty wheel hub was successfully completed by using the mastered test law (the schematic diagram of heavy-duty wheel hub and axle test is shown in Figure 2 and figure 3, and the input power flows in the direction of the arrow in the figure)

Figure 3 Schematic diagram of heavy-duty axle experiment

grams of technical problems

because the actual torque of each port of the test piece is very large, it is difficult to connect and measure. Therefore, we add a gearbox between the measurement sensor (measuring point) and the test piece, and use the gearbox to carry out torque transformation to complete the loading test

the biggest technical problems in the innovation process include: the determination of the transmission efficiency of the loading gearbox and the test piece; Determination of the functional relationship between the displayed value of the measuring point and the actual load at each port of the tested piece; How to analyze and sort out the test data and predict the change trend; Whether the test method can meet the requirements of technical conditions

at the beginning of the test, because we didn't have a deep understanding of the axle, we only selected the parameters according to the qc/t automobile drive bridge test method of the steam standard. During the test, serious faults such as axle housing cracking twice and driving cylindrical helical gear tooth breakage five times occurred. After careful analysis and repeated exploration, and constantly learning lessons from failures, we finally explored a set of reliability test methods suitable for heavy wheels and axles

measures and solutions

in order to solve the problem that the above technology is difficult to polish and hone for too long, we collected the test data of the secondary loading test while expanding the design freedom of the portable speaker gasket and shell, consulted a lot of data, and finally carried out a lot of practical verification

for example, in the test with the second axle reducer as the experimental object, the test parameter is that the maximum torque at the input end is 12000n · m; The input speed is 160r/min, and the whole life test is divided into two stages: running in test and formal test. The running in test is carried out under three loads of 0.25 MPa, 0.5 MPa and 0.75 MPa respectively, and each load gradually increases from small to large to the set load (i.e. 0.25MPa, 0.5 MPa or 0.75 MPa); The test speed is 160r/min; Each load requires the driving wheel to run 10000 times. The formal test is carried out according to the load MPa, and the test speed is 160r/min. Under this condition, the driving wheel is required to run 500000 times

after the regression analysis of the collected test data of the second axle reducer, the relationship between the actual load at the input end of the heavy-duty axle and the displayed value of the measuring point, and the transmission efficiency of each component in the system can be predicted and analyzed by using the regression analysis results

research results and experimental significance

in the actual detection, through the analysis of a series of experimental conclusions, we draw the following conclusions:

1. Using the relationship curve between loss efficiency and input power, find out the loss efficiency of the specimen under a certain power, and calculate the loss power of the driving unit under this power according to the working principle of the system; Then use the curve to calculate the working efficiency of each loaded gearbox and the working efficiency of the test piece under this load, and accurately determine the load size of each port of the test piece; Finally, the display value is accurately determined according to the load size of each port of the test piece. The test shows that its accuracy is more than 95%, and the operation is convenient, flexible and easy to grasp

We will continue to launch customized products

2. From the perspective of the test process, this test can accurately determine the equipment efficiency and specimen working efficiency under various loads, reduce the test preparation time, and improve the test efficiency; From the test data, it can accurately determine the load size of each port of the test piece and accurately predict the displayed value of the measuring point

3. The test conditions should be the same as the actual use conditions of the test piece as far as possible, and comply with the energy transfer process. In order to ensure that the test piece is not damaged by overload, the load of each port should be equal to the calculated value

4. There are no national standards and relevant industry standards for heavy-duty vehicle axle loading test, so the determination of loading parameters and test methods are difficult, and there is no relevant data for reference. Through the analysis of the test process and test parameters, we can determine the best parameters and the best working state of the test piece, and achieve a breakthrough in the detection ability of performance parameters such as the service life and reliability of the main transmission system of the vehicle, which provides a favorable technical guarantee for the research of heavy vehicles in China. (end)

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