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Bearings Failure Analysis And Solutions

Our highly skilled bearings engineers are dedicated to identifying and resolving bearings failure issues, offering cost-effective and actionable solutions to our valued customers. While variables may vary based on applications and environments, the history of a bearing is embedded in its metallurgy.

Preventing failures is paramount to safeguarding our reputation, minimizing costs and downtime, preserving lives, and avoiding inconveniences. Such shortcomings can encompass a combination of these factors, making comprehending the causes of failures and implementing preventive measures crucial.

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At TFL, our extensive experience speaks volumes, making us the preferred choice for bearing failure analysis across various industries and applications. We cater to diverse customers, including those in industrial sectors such as commercial airframes and power plants and advanced fields like space, nuclear, and cryogenics. When confronted with bearing failures, these businesses rely on TFL to identify the root cause and provide practical solutions to rectify the current issue and mitigate future occurrences. We offer our users comprehensive knowledge and expertise on failure modes, alongside access to our state-of-the-art testing facilities and specialized equipment. By partnering with us, customers can avoid inconveniences, unwanted expenses, or even more severe consequences from bearings failures.

Types And Causes Of Bearing Failures

1. Contact Fatigue Failure

Contact fatigue failure refers to the bearing working surface by the role of alternating stress and material fatigue failure. The standard form of contact fatigue failure is contact fatigue spalling. Contact fatigue spalling occurs in the bearing surface, often accompanied by fatigue cracks, first from the contact surface below the maximum alternating shear stress and then extended to the surface to form different spalling shapes, such as point for pitting or pitting spalling, spalling into a small piece of shallow spalling. Due to the gradual expansion of the spalling surface, it will slowly expand to the deeper layers, forming deep spalling. Deep spalling is the fatigue source of contact fatigue failure.

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2. Wear Failure

Wear failure refers to the relative sliding friction between surfaces, resulting in continuous wear of the metal on the working surfaces and loss.

Continuous wear will cause gradual damage to the bearing parts and eventually lead to the loss of dimensional bearing accuracy and other problems. The wear failure is one of the standard failure modes for all types of bearings, which can be categorized into abrasive wear and adhesive wear according to the form of wear.

 Abrasive wear refers to the bearing working surface between the extrusion of foreign hard particles or complex foreign matter or metal surface abrasive debris and contact surface relative movement caused by wear and tear, often in the bearing working surface caused by furrow-like abrasion.

Adhesive wear refers to the friction surface due to the friction surface of the microscopic bumps or foreign objects that the friction surface uneven force in the lubrication conditions deteriorates seriously due to local friction heat, easy to cause local deformation of the friction surface and friction micro-welding phenomenon, serious surface metal may be localized melting, the contact surface of the local friction force will be localized friction weld points from the substrate on the tearing and increasing plastic deformation.

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3. Fracture Failure

Bearing fracture failure is mainly due to defects and overload, two significant factors. When the applied load exceeds the material strength limit and causes parts to fracture is called overload fracture. Excess is mainly due to sudden Failure of the host or improper installation. Bearing elements of micro-cracks, shrinkage, bubbles, sizeable foreign debris, overheating organization and local burns, and other defects in the impact of overload or severe vibration will also cause a fracture at the fault, known as a defective fracture.

It should be noted that the bearing in the manufacturing process, the raw materials for the factory re-examination, forging and heat treatment quality control, and machining process control can be correctly analyzed through the instrumentation of the existence of the above defects. But in general, usually appear bearing fracture failure most for overload failure.

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4, Corrosion Failure

In some rolling bearings in the actual operation of the unavoidable contact with water, water vapour and corrosive media, these substances will cause rust and corrosion of rolling bearings. In addition, rolling bearings in the operation process will also be microcurrent and static electricity, resulting in rolling bearings of current decay.

Rolling bearing rust and corrosion will cause ring, rolling body surface pit rust, pear-shaped rust and rolling body interval the same pit rust, comprehensive rust and corrosion. Eventually, cause rolling bearing failure.

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5. Failure of Clearance Change

Rolling bearing in work, due to the influence of external or internal factors, makes the original fit clearance change, precision reduction, and even causes "bite dead", known as clearance change failure. External factors such as excessive surplus, installation is not in place, temperature rise caused by expansion, transient overload, etc.; Inherent factors such as residual austenite and residual stress in an unstable state, etc., are caused by changes in the clearance of the main reasons for Failure.

Rolling Bearing Common Failure Mode And Countermeasures

1. Unilateral Extreme Position Spalling Of The Channel

Single-side limit position spalling of the channel is mainly manifested in the junction of the track and the retaining edge with a severe spalling ring band. The reason is that the bearing is not installed in place or there is sudden axial overload during operation.

The countermeasures taken are to ensure that the bearing is installed in place or to change the outer ring of the free-side bearing into a clearance fit so that the bearing can be compensated for when the bearing is overloaded. Suppose it is not possible to ensure that the mounting is in place. In that case, you can increase the thickness of the lubricant film (increase the viscosity of the lubricant) or reduce the load on the bearing and other methods to reduce the direct contact of the bearing.

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2. Channel Spalling In The Circumferential Direction In A Symmetrical Position

Symmetric position spalling performance in the inner ring for the surrounding ring strip spalling, and the outer ring was circumferential symmetric position spalling (i.e., elliptic short-axis direction), the reason is mainly because of the shell hole ellipse is too prominent or two halves of the separated shell hole structure, which is particularly obvious in the motorcycle camshaft bearings. When the path is pressed into the elliptical shell hole or two halves of the separated shell fastening, the bearing outer ring produces elliptic, in the short-axis direction of the clearance is significantly reduced or even negative support. Bearing under the action of the load, the inner circle rotates to produce circumferential spalling marks, the outer ring only in the short axis direction of the symmetrical position of the spalling effects. This is the main reason for the early Failure of the bearing; the bearing failure parts inspection shows that the bearing outer diameter roundness has changed from the original process control 0.8um to 27um. This value is much larger than the radial clearance value. Therefore, it can be affirmed that the bearing is in severe deformation and negative clearance under the work; the work surface can quickly form early abnormal sharp wear and spalling.

The countermeasure is to improve the shell hole processing accuracy or, as far as possible, not to use the shell hole two halves of the separation structure.

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3. Tilted Raceway Spalling

A tilted spalling ring on the bearing surface indicates that the bearing is working in a tilted state; when the tilt angle reaches or exceeds the critical condition is easy to form an abnormal early sharp wear and spalling. The reason is mainly due to poor installation, shaft deflection, and low journal and shell hole precision.

Take countermeasures to ensure the bearing installation quality and improve the axial runout precision of the shaft shoulder and hole shoulder, or improve the lubricant's viscosity to obtain a thicker lubricant film.

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4. Ring Breakage

Ring fracture failure is relatively rare, usually caused by sudden overload. Complex causes, such as bearing raw material defects (bubble shrinkage), forging defects (overheating), heat treatment defects (overheating), processing defects (localized burns or surface microcracks), host defects (poor installation, poor lubrication, transient overload) and so on. Subjected to overload shock load or severe vibration may make the ring fracture.

 Countermeasures taken to avoid overload impact load, select the appropriate amount of surplus, improve the installation accuracy, improve the conditions of use and strengthen the quality control of the bearing manufacturing process.

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5. Cage Fracture

Cage fracture is an episodic and abnormal failure mode. Its causes are mainly the following five aspects:

a. Cage abnormal load. Such as, installation is not in place, tilt, excessive surplus, etc., easy to cause a reduction in clearance, exacerbate the friction heat, surface softening, and premature abnormal spalling. With the expansion of spalling, spalling foreign objects into the cage pocket hole, resulting in cage operation stall and generating additional load, intensifying the wear of the cage, so the deterioration of the cyclic effect may cause cage fracture.

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b. Poor lubrication mainly refers to the bearing running in a poor oil state, easy to form adhesive wear, so that the working surface state deterioration, adhesive wear produced by the tear is easy to enter the cage, so that the cage to produce abnormal load, may cause the cage fracture.


c. The intrusion of foreign objects is a common mode of cage fracture failure. The intrusion of foreign hard foreign matter exacerbates the wear of the cage and produces abnormal additional load, which may also lead to cage fracture.


d. Creep phenomenon is also one of the causes of cage fracture. The so-called creep refers to the sliding phenomenon of the collar, in the case of insufficient surface surplus, due to sliding and the load point to the surrounding direction, resulting in the collar relative to the axis or shell to the circumferential direction of the position of the phenomenon of deviation. Creep once produced, with the surface of significant wear; wear powder may enter the bearing inside, the formation of abnormal wear - raceway spalling - cage wear and additional load process, and may even cause cage fracture.


e. Cage material defects (such as cracks, large foreign metal inclusions, shrinkage, bubbles) and riveting defects (lack of nails, nails or two halves of the cage bonding surface gap, serious riveting injuries) and so on may cause cage fracture.

Take countermeasures in the manufacturing process to be strictly controlled.

6. Jamming

The so-called card injury is due to damage in the sliding surface damage produced by the part of the tiny burns summary and surface damage. Slideway surface, the rolling surface of the circumference of the square sentence of the line scar. The roller end face of the pendulum line scar, near the roller end face of the collar surface of the jamming. The main reasons for the jamming are: excessive load, excessive preload, poor lubrication, foreign body bite, tilting of the inner ring and outer ring, shaft deflection, shaft bearing box precision is poor.

It can be solved by appropriate preload, improving lubricant and lubrication methods, and improving the precision of the shaft and bearing box.


7. Wear And Tear

 The wear failure is caused by the relative sliding friction between surfaces resulting in the constant wear of the metal on the working surface. The leading causes of wear failure are lubricant failure or lack of lubricant, incorrect lubrication method, entry of abrasive particles into the bearing, excessive loads, etc. 

The solution can be found by improving the oil or the lubrication method. The answer can be to improve the lubricant or the lubrication method, enhance the sealing mechanism, etc.

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8. Scuffing

The so-called abrasion is in the raceway surface and rolling surface; with the slipping and oil film rolling, thermal cracking is produced by the aggregation of minor burns, and surface damage occurs. Produce a rough surface with adhesion. Causes of abrasion are mainly high-speed light load, rapid acceleration and deceleration, inappropriate lubricant, water intrusion, etc.

Solution: Improve the preload, improve the bearing clearance, use the lubricant with a good oil film, improve the lubrication method, improve the sealing device and so on.


9. Indentation

When a small metal powder or foreign matter is bitten into, an indentation is produced on the raceway surface or rotating surface or an indentation (Brinell hardness indentation) is formed on the pitch interval of the rolling element due to an impact during installation. The main factors causing the indentation are: metal powder and other foreign objects biting into the assembly or transportation process by the impact load is too large.

Solution: Improve the sealing device, filter the lubricating oil, and improve the assembly and use methods.


10. Burning

Raceway, rolling body and cage in the rotation of the rapid heating until discolouration, softening, melting and breakage. Causes of burnout are poor lubrication, excessive load (excessive preload), excessive speed, too small a clearance, water, foreign matter intrusion, shaft, bearing box precision is poor, shaft deflection is large.

This can be solved by improving the lubricant and lubrication method, correcting the bearing selection, studying the fit, bearing clearance and preload, improving the sealing device, checking the shaft and bearing box accuracy or improving the installation method.


11. Galvanic Corrosion

The so-called galvanic corrosion refers to the current in the rotation of the bearing collar and rolling body of the contact part of the flow, through the thin film of lubricating oil sends out sparks, the surface of the local melting and bump phenomenon. The leading cause of current corrosion is the potential difference between the outer and inner rings and the effect of static electricity.

 Solution: When setting up the circuit, the current does not pass through the bearing, the bearing is insulated, and the static electricity is grounded.

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12. Rust And Corrosion

Rust and corrosion of bearings are pitted rust on the surface of raceways and rolling bodies and comprehensive rust and corrosion. Bearing rust and corrosion will cause the ring, rolling body surface pit rust, pear-shaped rust and moving body interval to the same pit rust, comprehensive rust and corrosion. Cause rolling bearing rust and corrosion failure for many reasons, mainly have: water, corrosive substances (paint, gas, etc.) invasion, lubricant is not suitable due to the condensation of water vapour with water droplets, high temperature and humidity when stopping, transportation process of rust flawed, the storage state is not suitable, the use of inappropriate and so on.

Solutions include: improving the sealing device, studying the lubrication method, preventing rust when stopping, improving the storage method, and paying attention to the use.

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In addition to the above common forms of failure, rolling bearings in actual operation, many forms of loss are to be further analyzed and studied. The bearing common failure mechanism and failure modes can be seen; although the rolling bearing is a precise and reliable mechanism base body, improper use will also cause early failure.

 If the bearing can be used correctly, it can be used until the fatigue life. The early failure of the bearing is mainly caused by the manufacturing accuracy of the host with the part, the installation quality, the use of conditions, lubrication effect, external foreign body invasion, thermal influence and host sudden failure and other factors.

Therefore, the correct and reasonable use of bearings is a systematic project in the bearing structure design, manufacturing and installation process; to produce early failure of the link, take appropriate measures to improve the service life of bearings and host effectively.

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