Measurement data and response characteristics of fatigue pitting corrosion test for spur gears with six million cycles

Figure 1 shows the profile deviation measurement curve of aa-1 gear working tooth surface (left tooth surface) after running for 6 million times. The measurement results show that the maximum total profile deviation is 10.2 μ m and the maximum profile shape deviation is 5.7 μ M. By observing the photos, the characteristics of the tooth surface at this time are recorded, and the obvious gray spot belt features occur near the pitch line, and there is a certain width region along the tooth profile direction. At the same time, slight pitting occurred at I in the figure. From the characteristics of the whole tooth surface, it shows that the tooth surface at this time has slight pitting, which is consistent with the tooth surface deviation measured by the gear measuring center. The micro pitting corrosion is mainly due to the increase of the contact stress with the increase of the load and the operation cycle, which leads to the aggravation of the characteristic wear of the tooth surface, the generation of micro cracks on the tooth surface, the contact pressure and the viscosity of the lubricating oil, which leads to the micro pitting corrosion characteristics of the tooth surface after the metal particles fall off. Due to the increase of load or uneven distribution and the effect of lubricating oil, the edge effect of speculating flow will occur near the two ends of the gear, which makes it easier to produce adverse conditions such as excessive local stress near the end face of the gear, resulting in the formation and expansion of pitting corrosion characteristics. This phenomenon is consistent with the initial pitting corrosion characteristics at I in the figure. According to the gear tooth surface morphology and measured data, after six million operation cycles, the tooth surface experienced a process or turning point from the original tooth surface and normal wear to micro pitting or normal pitting.

The dynamic response analysis of the measurement system signal is still carried out in three stages within one million cycles. The time domain signal of vibration acceleration in each stage is shown in Figure 2. From the macroscopic distribution of the vibration acceleration time domain signal in the figure, the vibration acceleration time domain spectrum along the X vector in each stage presents the characteristics of stationarity and integrity, which can indirectly show the stability of the vibration signal along the X vector in this stage. Similarly, the vibration amplitude of the time domain spectrum of vibration acceleration along the Y vector is slightly disturbed, and the overall vibration amplitude deviates from the equilibrium position slightly, which indicates that the time domain spectrum of the signal is basically stable. However, the amplitudes of the vibration acceleration along the Y vector in the stages of 500000-600000 and 900000-1000000 are larger than those in the stages of 100000-200000. It can be inferred that there may be a process of further wear aggravation or early pitting on the tooth surface in this single 1 million cycles. This inference is explained by the tooth surface characteristics recorded in Fig. 1, that is, the appearance of the tooth surface The diffusion characteristics and local early pitting characteristics of the gray spot zone.

In order to more intuitively characterize the change attribute of vibration acceleration amplitude in three stages, the statistical calculation results of time domain signals along different vectors in each stage are obtained. The average temperature values of the three stages in the table are basically the same, indicating that the whole gearbox system is in the state of heat balance temperature. According to the statistical index values along the X vector in each stage, the statistical indexes g, G2, G4, G3 and G7 are basically consistent. The difference is that the skewness index gig is negatively skewed within 100000-200000 times, and the latter two are positively skewed; however, the distribution of the vibration values of the index GII is relatively concentrated within 100000-200000 times, and the latter two are relatively scattered. In the same way, in the Y vector, the statistical index value of 100000-200000 times of internal vibration is less than the number of cycles in the latter two stages, which further verifies and indicates that the geometric characteristics of the tooth surface change obviously in this stage. The statistical index G10 shows negative skewness in the stage of 900000-1000000 times, and the absolute value of skewness is 0.218, which is significantly larger than the former two values of 0.006 and 0.038, reflecting that the trend of the overall probability distribution of vibration acceleration in this stage is more deviated from its standard distribution. The statistical index G11 is less than 0 in the three small cycle times, which indicates that the distribution of vibration acceleration amplitude data is relatively scattered, and the absolute value of kurtosis value in 500000-600000 and 900000-1000000 times is greater than that in 100000-200000 times. It can be seen that the distribution of vibration acceleration amplitude data in the latter two stages is more scattered, which can be seen from the vibration acceleration value in Figure 2 The time domain signal along the Y vector can also be shown, for example, in Fig. 2 (b) and Fig. 2 (c), the amplitude fluctuation of vibration acceleration along the Y vector is obviously larger than that in Fig. 2 (a). From the analysis of the increase percentage of vibration acceleration amplitude, the vibration acceleration values within 500000-600000 times and 900000-1000000 times are 2.019 and 2.072, which are 24.5% and 27.8% respectively compared with 1.621 within 100000-200000 times. At the same time, the amplitude increase of the average value index G3 can reach 25.2% and 27.7% respectively. It can be seen that the increase percentage of the vibration acceleration is basically the same whether from the maximum amplitude or the average amplitude, indicating that the dynamic response of the system is an overall increase.

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