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/*728*90 created on 2018/5/16*/ var cpro_id = "u3440131"; Home>Bearing knowledge> Bearing failure mechanism and cause Bearing failure mechanism and cause
Bearings are fine mechanical roots. Because of the rapid development of science and technology; the demand for the quality of bearing products is getting higher and higher. It is of course important for the manufacturer to supply high-quality products that meet the specifications and satisfy the performance of the main engine; but the correct use of bearings In the past few years, the author has been engaged in the skills of motorcycle-specific bearings; often encountered such a problem; that is, the bearing is tested and qualified; but after the installation, the bearing appears stuck or the early stop-turn failure when used. It reflects the gradual change of the stuck card and the severe leakage of the working surface; the frame is severely worn and even distorted and cracked. The failure results are analyzed and marked; the quality problems of the bearing itself are not many; most of them are due to the improper use of the device. To this end; It is necessary to make some shallow general descriptions about the common failure modes and mechanisms of bearings; in order to play a role in attracting jade. /*250*250 was created on 2017/12/25*/ var cpro_id = 'u3171089';
First, the failure mechanism of the bearing 1. Touch fatigue failure Touch fatigue failure refers to the failure of the bearing work surface to be affected by alternating stress. Touch fatigue occurs in the bearing work appearance; often accompanied by fatigue cracks; firstly from the touch surface appearance below the maximum alternating shear stress Then expand to the appearance of a different shape of the shedding; if the point is pitting or pitting off; the small piece is called the shallow layer shedding. Because of the gradual expansion of the shedding surface; and often to the deeper; {TodayHot} Forming deep detachment. Deep detachment is the source of fatigue that touches fatigue failure. Wear and failure Wear and tear refers to the failure of the relative sliding between the appearances to cause the wear and tear of the working exterior metal. The continued wear will lead to the gradual damage of the bearing parts; and the end will lead to bearing dimensional accuracy loss and other related problems. Wear can affect To the shape change; the cooperative open space is enlarged and the operation appearance is modified; the smoothing agent can be affected or the pollution reaches a certain extent, and the smooth function is completely lost; thus the bearing loses the rotation precision and can not work normally. The wear failure is various types of bearings. One of the common failure modes; the wear mode is usually divided into the most common abrasive wear and adhesive wear.
Abrasive wear refers to the wear and tear caused by the extrusion of foreign solid particles or hard foreign objects or metal appearance between the outer surface of the bearing work, and the wear caused by the relative movement of the touch surface; often the furry-like scratch on the outer surface of the bearing work. Hard Particles or foreign matter can come from inside the host or other adjacent parts from the host system are fed into the bearing by the smooth medium. Adhesive wear means that the conflicting surface is unevenly affected by the microscopic bulging or foreign matter of the conflicting surface; the smooth condition deteriorates severely. Time; heat generated by partial conflict; easy to form part of the conflict surface and conflict micro-welding; when the surface is severe, the surface metal can be partially melted; the force on the touch surface tears part of the conflicting joint from the substrate to increase plastic deformation This cyclical process of adhesive tear adhesion constitutes adhesive wear; in general; fine adhesive wear is called abrasion; severe adhesive wear is called bite. Cracking failure bearing cracking failure is the primary cause of shortcomings and overload. When the applied load exceeds the data strength limit, the component cracking is called overload cracking. The overload is caused by the host's sudden fault or the device is not properly. The micro-crack of the bearing parts, Shrinkage, air bubbles, large foreign objects, overheating arrangements and partial burns will also cause cracking in the shortcomings during impact overload or severe oscillation; called fault cracking. It should be pointed out; the bearing is in the process of production; The re-inspection of the factory, the quality control of the casting and heat treatment, and the processing of the processing process can be correctly analyzed by the instrument to determine whether the above-mentioned shortcomings can exist; in the future, the control must be strengthened. However, in general, the bearing cracking failure usually occurs is mostly overload failure. .
4. The clearance changes the failed bearing in the operation; because of the influence of the external or connotation elements; the original cooperative vacant land is changed; the precision is reduced; and even the "biting death" is called the clearance modification failure. The external factors such as excessive interference are excessive; Insufficient position; large amount of expansion caused by temperature rise, instantaneous overload, etc.; connotation elements such as residual austenite and residual stress are unstable, which are the primary reasons for the failure of the play change.
Second, the common failure mode of the bearing and countermeasures 1. One-side limit azimuth loss channel single-side limit azimuth drop primary body now has a severe off-loop zone at the interface between the channel and the rib. The cause is that the bearing device is not in place or sudden axial overload during the operation. It is to ensure that the bearing device is in place or that the outer bearing outer ring cooperation is changed to open space cooperation; in order to make the bearing compensated when the bearing is overloaded.
2. The channel is symmetrically oriented in the circumferential direction and the symmetrical azimuth is off. The inner ring is now the outer ring is detached; the outer ring is circumferentially symmetrically asymmetrical (ie, the short axis direction of the ellipse); the origin is due to the ellipse of the outer shell. Large or two halves of the outer casing hole layout; this is particularly evident in camshaft bearings for motorcycles. When the bearing is pressed into the outer shell hole of the elliptical ellipse or when the two halves are fastened, the outer ring of the bearing is elliptical. The clearance in the short axis direction is obviously reduced or even negative. The bearing is under the action of the load; the inner ring rotates and the circumferential detachment marks occur; the outer ring only shows signs of detachment in the symmetrical orientation of the short axis direction. This is the early bearing The primary cause of failure; marked by the failure of the bearing; the roundness of the outer diameter of the bearing has changed from 0. 8μm controlled by the original process to 27μm. This value is much larger than the radial clearance value. Therefore; It is operated under severe deformation and negative clearance; the working surface is easy to form abnormal abnormal wear and fall at the early stage. The countermeasure adopted is to improve the machining accuracy of the outer casing hole or to use the outer casing hole instead of the two. .
3. The raceway is slanted off on the bearing working surface with a skewed off-belt; it clarifies that the bearing is working under the skew condition; when the slant angle reaches or exceeds the critical condition; it is easy to form an abnormally sharp wear and fall at the early stage. Because the device is not good; the shaft has deflection, the accuracy of the journal and the shell hole is lower; the countermeasures are adopted to ensure the quality of the bearing device and improve the axial runout accuracy of the shoulder and the shoulder.
4. Cracking of the ferrule cracking ring is usually less common; it is often caused by sudden overload. The cause is more messy; such as bearing raw material defects (bubbles, shrinkage holes), casting defects (overburning), heat treatment defects (overheating) Disadvantages of processing (partial burns or micro-cracks on the surface), host defects (poor device, lack of smoothness, instantaneous overload), etc.; Select the right amount of interference, improve the accuracy of the device, improve the operating conditions and enhance the quality control in the bearing production process.
5. The cracking of the cage cracking cage is attributed to the sporadic abnormal failure mode. The main reasons for its occurrence are as follows:
a. Abnormal load of the cage. If the device is not in place, skewed, excessive interference, etc., it is easy to form clearance; increase conflict heat; appearance softening; prematurely appear abnormal shedding; follow the expansion of the shedding; In the case of the cage operation and additional load; the wear of the cage is aggravated; such a deteriorating cycle; the cage can be cracked.
b. The poor smoothness mainly means that the bearing operation is in a poor oil condition; it is easy to form adhesive wear; the appearance of the work is deteriorated; the tearing material caused by adhesive wear is easy to enter the cage; the cage is subjected to an abnormal load; and the cage can be cracked.
c. The intrusion of foreign objects is a common way to prevent the cracking of the cage. The intrusion of foreign hard foreign objects increases the wear of the cage and the abnormal additional load; it can also cause the cage to crack.
d. The creep appearance is also one of the reasons for the cracking of the cage. The so-called creep multi-finger slewing surface; in the case of lack of interference in the cooperation surface; the load point moves in the surrounding direction because of the sliding; The appearance of the shaft or the casing facing away from the circumferential direction. Once the creep occurs, the cooperating surface is obviously worn; the wear powder has the ability to enter the inside of the bearing; the process of forming the abnormal wear raceway off the cage wear and the additional load; so that the cage can be cracked .
e. Disadvantages of cage data (such as cracks, large foreign metal inclusions, shrinkage cavities, air bubbles) and riveting defects (nails, studs or two halves of the cage contact surface; severe riveting) can constitute cage cracking Adopting countermeasures is to strictly control the production process.
Third, the conclusion is summarized; from the common failure mechanism and failure mode of the bearing; although the rolling bearing is a fine and solid tissue root substrate; but improper use will also lead to early failure. Under normal circumstances; if the bearing can be used correctly; The application to the exhaustion of life stops. The early failure of the bearing is caused by the production precision, device quality, operating conditions, smoothing effect, external foreign body intrusion, heat influence and host sudden failure. The use of bearings is a systematic project; in the process of bearing layout design, fabrication and installation; alignment of the early failures; adoption of corresponding methods; can effectively improve the service life of bearings and mainframes; this is the manufacturer and The customer should have a responsibility together.
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Source: Bearing network time: 2018-02-17