Heavy duty gear is the core component of large equipment transmission, which is widely used in many industries such as mining, metallurgy, building materials, petroleum, chemical industry, power station, forging, lifting and transportation machinery. If the gear has high performance, it will play an important role in extending the overall service life of Mechanical equipment. In the actual working environment, the service condition of heavy duty gear is bad and complex, It is necessary to bear not only the alternating load with high stress level, but also the large shear stress and instantaneous impact stress. The root bending stress has become an important factor leading to the failure of low-speed and heavy-duty gears.
In the process manufacturing industry, low-speed and heavy-duty gear often plays a very important role, and its normal operation directly affects the production efficiency of the whole production line. For example, once the deep-sea drilling equipment, converter dumping mechanism and other metallurgical mining equipment are shut down due to gear damage, in addition to the losses caused by the damage to the equipment, it will also disrupt the production rhythm of the whole production line, and the resulting economic losses will be immeasurable.
Due to the abnormal vibration of the system caused by the derivation and development of mechanical faults, vibration detection technology plays an increasingly important role in the fault diagnosis and life prediction of high-speed equipment such as water / steam turbine rotor and wire rod finishing mill. However, for the ultra-low speed structures such as large slewing bearing and converter tilting mechanism, the “power” of vibration test can not be exerted. Most of the reasons are due to the complex structure and poor operation conditions of the equipment. The acquisition performance of the test system and the time-frequency resolution of the signal need to meet higher requirements. The difficulty of feature extraction is far greater than that of ordinary equipment. However, compared with signal acquisition and analysis, the root cause of ultra-low speed equipment diagnosis is that the fault mechanism under ultra-low speed condition is not clear, that is, a series of problems such as how the fault is generated and why it is extended are not clear. Throughout the literature at home and abroad, the fault diagnosis of low speed equipment mainly focuses on the algorithm research of feature extraction, or the analysis of failure causes, and the systematic elaboration of mechanism problems is rare.
At present, the research of fault mechanism lags far behind the research of feature extraction algorithm. In the age when computers are not developed, it is the core of “fault mechanism research” to use simple and easy mathematical model to describe the nature of fault occurrence. In today’s increasingly developed technology, the research focus should focus on the complex conditions, especially the dynamic response of equipment under extreme conditions such as variable speed and variable load impact, random disturbance and so on. The research object of this project is large gear under low speed, heavy load and extreme service conditions. The fatigue crack initiation and small crack growth behavior of large gear are studied by the combination of experiment and numerical simulation, The research has important theoretical and practical significance for establishing a set of high reliability fatigue life prediction method and improving the service life of low-speed and heavy-duty gears.