A large number of experiments have shown that the formation of arc discharge in EDM is closely related to the transient arc and the arc discharge is caused by the short circuit, the transition arc, the short circuit and the transition arc.
A single pulse discharge is performed in the interelectrode gap in the magnetic field, and it is found that the magnetic field has an influence on the discharge pit. The extending direction of the discharge pit is perpendicular to the magnetic field, indicating that the moving direction of the discharge channel coincides with the direction of the Lorentz force, and there is a magnetic flux velocity that optimizes the etching speed.
Kunida et al. found that there are many smaller pits around the discharge pit after a single pulse discharge. It is analyzed that the arc moves at a high speed in a small area, and the reason for the motion is the difference in the work function of the cathode surface and the internal material and the difference in electric field force between the bottom and the upper edge of the discharge pit. However, until now, the physical and mathematical models of the electrical erosion process have not been fully established.
From the perspective of the world, the mechanical industry powers such as the United States, Britain, Germany, Japan, Austria and other countries have not thoroughly and systematically studied the phenomenon of gear erosion. For example, the Japan Mechanical Society has paid attention to gear erosion. This kind of gear failure method proposed measures such as gear shaft insulation and motor grounding, but scholars from various countries did not make theoretical analysis and experimental research, forming a certain research gap.
China's scientific research workers and production workers have noticed the phenomenon of gear erosion. For example, Xu Shuixiang and Ye Ping of the Shanghai Electric Power Repair General Factory have made detailed statistics and analysis on the electro-erosion phenomenon of the hydraulic coupling gear produced by the factory. Rendeqing and Zhou Tianwang of the Xixi Power Plant made a gear erosion analysis report on the gear of the variable speed feed pump coupling. Chen Xianfang of Sichuan Dongfang Motor Factory studied the damage of the motor shaft current to the bearing. Professor Zhu Xiaolu of Beijing University of Science and Technology and Associate Professor Pan Ziwei of East China Institute of Metallurgy Tianjin Steel Plant High Speed ​​Wire and Wire Plant Finishing Mill Gearbox Gear Damage and Bearing Erosion Failure and Electric Power Pump Set of Maanshan No. 2 Power Plant, Anhui Province, Electro-coupling Gear Erosion Failure from Gear (Bearing) Parts Quality, Lubrication System Pair Qualitative and quantitative theoretical analysis of the bearing capacity and lubrication condition was carried out. Combined with on-site investigation and sampling, the situation before and after the fault was accurately investigated, and the metallographic photograph was taken by electron microscope, which obtained a lot of credibility. Evidence and clear conclusions, based on this with the University of Chongqing Wei Yunlong
Understanding the gear erosion phenomenon The gear erosion system is a special tribological system. Through various statistical data and analysis data, the author believes that it may be considered that the gear erosion phenomenon is such that there is a lubrication condition between the friction surfaces of the gear device. A friction pair that is good (such as elastic hydrodynamic lubrication), under the action of a certain type of electric field, the extremely thin oil film is broken down to cause gear erosion (similar to electrical discharge machining) or an electrothermal effect (similar to electric welding) occurs between the contact points, resulting in The physicochemical properties of the friction surface change greatly during the friction process, which leads to a great increase in the wear rate, a drastic change in the quality of the friction surface, and even a change in the microstructure of the local contact point.
The difference between gear erosion and pitting, corrosion wear and gluing 1) The shape of the electric etch pit is smooth and has a molten discharge trace, and the edge of the pit is annealed. Electro-etching often occurs on multiple tooth faces to all gear teeth. Pitting pits often appear on the lower tooth surface of the section line slightly parallel to the section line, and the macroscopic appearance appears as a fan-shaped or shell-shaped etch pit; the etched topography is different from the pitting pit, and the etch pit is on The lower tooth surface is often evenly distributed, and the distribution position has no relationship with the pitch line, and the size is relatively uniform and small.
2) Corrosion wear is a type of gear damage that is dominated by chemical wear and is accompanied by mechanical wear. Its shape is characterized by corrosion pits on the teeth, and effective wear on the tooth surface. Since the entire tooth (including the working surface and the non-working part) is in the corrosive medium erosion range, not only the corrosion pit is uniformly distributed on the gear working surface, but also the corrosion pit and the corrosion pit are also visible in the non-working part. Differently, the etch pits only exist on the meshing work surface, and the etch pits are distributed not only on the working surface but also on the non-working surface.
3) Electro-erosion is different from thermal gluing: pressure is not necessarily required, and it still occurs under no-load conditions. The slip ratio between the tooth surfaces is not high. In fact, when the electric corrosion occurs, the tooth surface metal is not in direct contact. Instead, they are separated by lubricating oil, and the electric erosion is evenly distributed on the meshing tooth surface, which is insensitive to the distance of the pitch line, and the hot glue often occurs farther away from the pitch line on the tooth surface.
Similarly, electro-erosion is different from cold gluing: electro-erosion is the breakdown of the lubricating oil between the tooth surfaces caused by voltage, which does not require any contact stress, and cold gluing is generally caused by severe concentration of local loads.
The conclusion summarizes the research status of gear erosion in China and abroad. At the same time, it collects and collects typical cases of gear erosion in China, analyzes the complexity and interdisciplinary research of gear erosion system, and points out that the system is a special kind. The tribological system has led to the research methods of the gear erosion system and some principles and notable issues that should be followed.
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