tailieunhanh - Handbook of Lubrication Episode 1 Part 10

Tham khảo tài liệu 'handbook of lubrication episode 1 part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Volume II 219 Table 3 EFFECT OF WATER IN LUBRICANTS ON ROLLING CONTACT FATIGUE LIFE Lubricant Water content Fatigue life reduction Test equipment and Hertzian stress Ref. descriptiona of oil SAE 20 rust and oxidation inhibited mineral oil 48 Tapered roller bearing GPa X 106 psi 31 Mineral oil-based 45 Angular contact bearing Emulsifying hydraulic oil 56 GPa X 106 psi 32 SAE-10-based mineral oil 45 Unisteel bearing fatigue test GPa X 106 psi 33 SAE-10-based mineral oil 17 Rolling 4-ball GPa X 106 psi 34 Emulsifying hydraulic oil purged with Argon seawater 45 Rolling 4-ball GPa X 106 psi 35 a Water content of oil without added wafer given in parentheses. where C is the water content in ppm. The exponents of C are in good agreement with the in Equation 7. It follows that the Weibull slope increases with increasing water content suggesting that the lives of those bearings which run the longest before failure are affected most since the water will have a longer time to affect the crack initiation and crack propagation processes. Most industrial oils contain dissolved water in the range of 50 to 500 ppm and may become further contaminated with moisture from the operating environment. Water molecules being extremely small compared to the base lubricant and additive molecules readily diffuse to the tips of microcracks and decompose on the highly reactive newly formed surface to produce atomic hydrogen. The hydrogen diffuses into the metal ahead of the crack causing hydrogen embrittlement of the steel. The embrittlement not only allows the crack to propagate more readily but promotes crack Water-accelerated fatigue and its prevention by lubricant additives has been investigated using a rotating-beam fatigue The additives are considered to function by proton neutralization formation of hydrophobic film or water sequestration. Lubricant Type and .