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SKF self-aligning ball bearing working surface failure analysis failure analysis on bearing surface is an important link to improve bearing reliability in systems engineering (bearing lost its function at work, resulting in a failure or is not working properly is called failure (FAG bearing failure in their life can be divided into normal and early failures in two ways.
1. causes of corrosion pitting corrosion of metal and slag, surface defects, osteoporosis results of micro-batteries. When the metal surface when there is a deficiency, osteoporosis, such as slag, electrochemical performance of these parts and other parts are different. These parts become a strong Anodic dissolved trends, other part becomes cathode, metals are good conductors, metals adsorbed water are ion conductors, like many short circuit galvanic cell with discharge of chemical reactions, Anodic dissolution and cathodic discharge speed, rate of metal corrosion.
2. causes of fatigue failure fatigue failure is all kinds of NSK bearing surface is one of the most common form of failure, metal under the long-term effect of alternating load resulting from failure, mainly for the process of fatigue crack initiation and the propagation and fracture.
Cracks in two ways:
① from surface produced, that in KOYO bearing of contact process in the, due to outside contains of role in work surface caused cyclical changes of contact stress, in surface produced plastic deformation and deformation hardened, last in work surface appeared tiny crack, by surface to in development, in the crack formed of two a surface Zhijian, due to lubricant of? into, make crack wall by force open, forced crack forward development;
② cracks from surface, that is, under the action of surface contact stress of repeated, crack first arose in the contact surfaces have some depth, and along with the surface at an angle of direction, reaching from the surface after a certain depth and come out to the surface, resulting in pitting flaking, left one by one on the contact surface.
3. factors influencing the surface fatigue and corrosion
material smelting quality as mentioned earlier, corrosion and fatigue failure in large part on smelting quality and materials relating to the advantages and disadvantages of surface defects, porosity and slag are the cause of pitting corrosion and fatigue failure on the main part. Study, effect of nonmetallic inclusions on TIMKEN bearing life with inclusion varies depending on the type, form and quantity of different, with spherical deformation of inclusions to the INA bearing life the most.
Heat treatment heat treatment State primary and State related to fatigue failure. Is sensitive to fatigue failure of metallic materials by organizations, such as the carbon content of Martensitic, carbide particle size and content, surface hardness and hardness gradient and center of carburized layer thickness and the transition layer thickness of surface residual stress distribution, have a considerable effect of carburizing on fatigue failure of steel smaller carbide particles distributed as evenly as possible fatigue failure-prone.
Surface machining precision parts machining precision influence of contact stress distribution on the surface. Surface machining accuracy, and surface contact area of load concentration the more serious the greater the contact stress, more prone to fatigue failure • smaller surface roughness value Ra, stress concentration is small, contact fatigue life of high. A study has found, when surface roughness increased from Ra=0.4mm to Ra=0.1mm, contact fatigue life up to 6~8 times.
4 measures to prevent surface corrosion and fatigue failure
(1) product structure design, increased safety as possible within the scope of the equivalent radius of contact and reduce contact stress.
(2) the choice of appropriate friction material, improving the yield limit and fatigue limit for example, Raceway and the spherical ball selects the same material, and its hardness.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 4T-32006X NTN | 30 | 55 | 17 |
| 4T-332/28 NTN | 28 | 58 | 24 |