In modern electric equipment, especially electric vehicles, inverter control systems can lead to complex shaft voltages and bearing currents. Within an electric motor, many parts have electrical failure problems, and among which bearings are the most sensitive and vulnerable components. In recent years, electrical failures in bearing have been frequently reported in electric vehicles, and the electrical failure of bearings has become a key issue that restricts the lifetime of all-electric motor-based power systems in a broader sense. The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles. The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents, as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures, have been discussed. The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed, and corresponding countermeasures have been proposed. Finally, a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.

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Electrical bearing failures in electric vehicles

Stress relaxation of nitrile rubber composites filled with a hybrid metakaolin/carbon black filler under tensile and compressive forces

An overview of the recurrent failures of duplex stainless steels

Titanium tubes generally exhibit superior resistance against electrochemical corrosions amid seawater for their passive films TiO2. However, hydrogen-assisted corrosion (HAC) is actually the Achilles' heel to titanium materials when the temperature exceeds near 70 °C. In this event, severe degradations like quick thinning and leakage were frequently detected on a large number of titanium tubes exposed to natural seawater environment within heat exchangers in a nuclear power plant, which caused serious safety problems. This paper is the Part I of totally two parts conducted for the whole failure analysis study, mainly focusing on electrochemical aspect of failure causes and their behaviors. By means of over ten kinds of characterization methods, the analysis results identified that the HAC induced by the interaction effects between galvanic corrosion and crevice corrosion led to local bulges of the inner walls of some titanium tubes, and then the bulges were quickly thinned and eventually ruptured under the eddy erosion from the seawater containing sediment particles. Finally, relevant mechanisms were addressed in detail and prevention methods were proposed as well.

Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant. Part I: Electrochemical corrosion

Tribological challenges and advancements in wind turbine bearings: A review

Failure analysis on abnormal corrosion of economizer tubes in a waste heat boiler

Failure analysis on abnormal wear of roller bearings in gearbox for wind turbine

The grease-lubricated roller bearing of an electric motor that drove a supply blower suddenly failed during operation. In order to identify the causes of the failure, a variety of characterizations were carried out. The failed surfaces of the bearing were observed visually and microscopically, and the characteristics of the lubricating grease were also investigated. Results showed that the surface of the inner ring of the bearing contained contact fatigue damage, and was covered with a multitude of debris and contact fatigue pits. What’s more, the lubricating grease was subjected to severe thermally induced degradation due to high service temperature, which consequently resulted in the decrease of the lubricating capacity of the grease. Thus, the lubricant film in the roller/raceway contacts was not formed effectively and the lubrication of the roller bearing was poor. As a result, serious local wear as well as contact fatigue damage were brought about on the roller and raceway and the wear finally led to the failure of the bearing.

http://jpkc.fudan.edu.cn/picture/article/348/82/c9/1dd4a6b341e6bad63a13e68835a5/cc5aa196-7ab5-4916-a6a5-6bda65fcc6d6.pdf

Zhen-Guo Yang

Papers

Failure analysis on abnormal corrosion of economizer tubes in a waste heat boiler

Failure analysis on abnormal wear of roller bearings in gearbox for wind turbine

Fatigue Failure Analysis of a Grease-Lubricated Roller Bearing from an Electric Motor

Failure analysis of O-ring gaskets of the electric hydraulic system in the nuclear power plant

Comparative study on degradation of ethylene-propylene rubber for nuclear cables from gamma and beta irradiation