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Analysis of the fundamental failure mode of nsk bearing
Source: Bearing network time: 2014-10-19
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(1) Brittle fracture nsk bearing parts are in operation; because the environmental conditions are not appropriate, the data may become brittle; then it will cause brittle cracking; constitute a hazard.
There is a cracking "source" in the cracking of the data; that is, the starting point of the crack.
The "source" of brittle cracking is the microcrack (0. 1 ^-1 mm) inside the data; this microcrack occurs in the process of making and processing parts, using the running process; and the stress gathering in the layout.
The characteristic of brittle cracking is that the working stress received during cracking is low; it usually does not exceed the yield limit of the data; it does not even exceed the allowable stress; it is also called low stress brittle fracture; the medium and low carbon steel is at lower temperature. (100C ^ -15 0C) will change from the resistant condition to the brittle cracking; the high-strength steel has no significant temperature effect; the brittle cracking of the fracture is flush; the fracture section is shortened very much. Page S腥腥治治èšèšèš; Fragile cracking is usually a sudden attack; many fragments will occur.
(2) Excessive cracking of nsk bearing parts under the effect of alternating load; called fatigue cracking. Exhaustive cracking is the most common part failure mode in engineering; accounting for 40%-90% of engineering cracking problems.
Common types of fatigue cracking include high weekly fatigue, low weekly fatigue, fatigue, fatigue, and heat exhaustion.
The nsk bearing data is under the effect of alternating stress below the yield limit; the fatigue damage with longer life is called high cycle fatigue. Conversely; under the large stress effect; the data part stress exceeds the yield limit; and the total number of cycles is not at the time of cracking Exceeding 104's fatigue damage; called low-week fatigue. The data is under the effect of high touch pressure; making the part of the touch appearance attack the nsk bearing off; then inducing the appearance of the part failure; called touch fatigue. nsk bearing The data is combined with the effect of alternating stress and corrosive medium; the appearance of the data constitutes a corrosion pit or microcrack; then the appearance of cracking failure is called; it is called corrosion fatigue. The fatigue failure caused by temperature fluctuation or thermal cycle effect is called heat. exhausted.
The fatigue fracture can be roughly divided into three regions; namely, the fatigue crack source region, the crack expansion region and the instantaneous cracking region.
(3) Overload cracking When the external load exceeds the ultimate stress of the mechanical component risk section; the attack is called overload cracking.
The microscopic features of the fracture of the overload crack are the same as the tensile fracture of the data; when the data plasticity is good; the fracture shows a large plastic deformation; and when the data is brittle; the new mouth of the part shows the brittleness.
One of the most common ways of overload cracking is tensile cracking; the fracture is gray-fibrous; it is microscopically divided into a flat surface (planar) and a shear plane (bevel).
(4) Stress corrosion cracking nsk bearing in corrosive medium; the effect of tensile stress (or residual stress); together with electrochemical corrosion, causing the appearance of normal ductility data agile cracking and early brittle I win damage; called stress corrosion Cracking.
The characteristics of stress corrosion cracking are: the moment of stress corrosion failure is shorter than the failure time of stress and corrosion alone; the magnitude and direction of stress directly affect the source of stress corrosion cracking and the crack expansion speed; and the greater the stress; The shorter the cracking time of the part; the stress corrosion cracking attack often has no obvious signs; it is abrupt; the nsk bearing data will only cause stress corrosion cracking in special environmental medium; the impurity element is sensitive to the stress corrosion cracking of nsk bearing data. Sexual influence is great.
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