Crack origin were located on laser marking area of small head end of inner ring. We list the most common bearing failures to help you decide what has happened with your bearing. Failure analysis of tapered roller bearing inner rings. In this article i will address the issue and share a case study in. Axial cracks on inner rings of high speed and intermediate speed bearings have become a leading cause of wind turbine gearbox life issues. As a result, the bearing inner or outer ring can eventually crack, leading to the premature failure of the bearing. Bearing failures and their causes bearing, linear motion. Relation between residual and hoop stresses and rolling. After mounting, for tight transition fit keeping inner ring from rotating relative to shaft, innerring o. When in order to allow larger axial displacements of the shaft in relation to the housing, needle roller bearings must be combined with wider inner rings. Grinding burn leading to thermal softening occurred on the small head end. A load was then applied during a running test until the stress causes the precrack to expand. It is an uncommon fault that bearing inner ring is cracked axially. The inner ring fracture strength test involves creating a precrack on the innerring of a bearing, and then mounting it on a test shaft to a prescribed interference fit.
Slightly rounded fractured edges indicate that fracture originated during operation and was cycled crack edges may break off after prolonged operation. We deliver a broad, quality range of products along with the highest levels of customer service. Understanding the root causes of axial cracking in wind. Premature bearing failures in wind gearboxes and white. Sharp edged cracks indicate fracture during dismounting. The crack may be initiated from material defects such as inclusions and, owing to. Bearing failures and their causes bearings are among the most important components in the vast majority of machines and exacting demands are. Bearing rotation, outer ring vs retainer vs inner ring. This type of failure is progressive and once initiated will spread as a result of further operation. The shaft cannot be used as a raceway with needle roller and cage assemblies, drawn cup needle roller bearings with open ends, drawn cup needle roller bearings with closed end and needle roller bearings. As you mounted the bearing inner ring on the tapered shaft, the stresses on the ring increased. Hoop brittle fracture occurred on the tapered roller bearing inner rings. An axial crack failure of the inner ring can be caused by excessive hoop stresses during installation but this does not appear to be the general case in the wind industry. Buy needle roller bearing inner rings direct from motion industries.
These include mounting bearings on shafts by applying pressure or blows to the outer race, mounting bearings into a housing by pressing on the inner ring, loose shaft fits, loose housing fits, excessively. When examining a bearing that has run for some time, a number of changes can be observed, such as. Wec are structural changes in the material that form below the surface of the bearing. These two spherical diameters are then matched to offer the optimum combination of load capacity and bearing frictional torque.
Practically all rollerbearings consist of four basic parts. Relation between residual and hoop stresses and rolling bearing fatigue life. A number of conditions can cause denting, wear, cracked rings, high operating temperatures, early fatigue and premature failure of bearings. Inner rings are made from hardened rolling bearing steel and have precision machined or ground raceways. Outer ring crack caused by a heavy impact through the rolling elements inner ring crack caused by excessive hoop stress. These changes result in the formation of cracks, which extend to the surface during stress conditions under different external loads. The steel didnt fracture right away, it was sneaky. Amcan is a fast growing global supplier of ball and roller bearing products. Radial bearings include an outer ring with a concave spherical surface.
A design criterion for the fatigue life of ball bearings is developed in section 3. Material improvements can reduce inner ring fractures. Premature bearing failures in wind gearboxes and white etching cracks wec. Inner rings are made from hardened rolling bearing steel and have precision ground or machined raceways. Bloch, in machinery failure analysis and troubleshooting fourth edition, 2012. Bearing 1 failed with one visible axial crack on the inner ring raceway. A bit later, as you start lifting the roll to get it into position, the roll rotates, and you can see what happened. There is a crack in the bearing inner ring, straight. What are some of the determining factors faults could assembly during service bearing bore and the shaft seat. How to diagnose cracked inner ring and bearing looseness. Static overload of the bearing or severe impact to the bearing, such as using a hammer to install the bearing, dropping or striking assembled equipment, or pressing a bearing onto the shaft by applying force to the outer ring. Originating point is observed at the middle of the left raceway surface.
Fatigue damage in a loaded zone of a tapered roller bearing inner ring flaking on the edge of a tapered roller inner ring. Severe brinell marks can cause premature fatigue failure. The remedy is to replace the bearing or consider redesigning to use a bearing having a greater calculated fatigue life. Your proven service leader with reliable delivery since 1972. The internal bearing construction is basically the same as the deep race. Wide inner ring bearings introduction fafnir bearings division of the torrington company, originated the wide inner ring bearing design for ball bearings which could be easily mounted on straight shafts and positioned without shoulders, locknuts or adapters. It waited until you were busy with something else and crack. These are heat checks on the bore of an inner ring. Understanding the root causes of axial cracking in wind turbine. View our range of inner rings, made from hardened rolling bearing steel and have been precision machined. Heat generation due to sliding with the inner ring. Deep and narrow nearsurface microgrooves were introduced by laser marking.
Geew series spherical plain radial bearings with wide inner ring with fitting crack and wide inner ring with fitting crack two seals. Cracking inspection of bearings after operation howto. To decide whether a bearing ring, either inner or outer, should be mounted with an interference or a slip fit on its shaft or in its housing, determine whether the ring rotates or is stationary with reference to load direction. Needle roller bearing inner rings motion industries. Roller bearing service damage and causes figure 17 heat checks see description of figure 16. However bearing getting loose over shaft is not uncommon. Prevention of white etching cracks in rolling bearings. It will always be accompanied by a marked increase in vibration, indicating an abnormality. The test involves a cylindrical roller bearing with its inner ring bore diameter of 220 mm mounted with a normal fit onto a fivelobewaviness sleeve that is attached to a shaft with interference. Inner rings inch and metric bearing inner rings ast. Since bearings that fail prematurely or unexpectedly cause trouble, it is important to be able to identify and predict failure beforehand, so that preventive measures can be adopted. When the ring cools, it shrinks holding the ring in place, but also creating tensile stress in the ring that increases the possibilities for axial cracking.1356 415 671 111 340 737 648 1093 943 1170 867 1504 1219 1266 1296 824 412 921 200 394 48 1331 998 1277 1041 1024 803 400 396 1614 1646 461 1525 507 684 573 330 756 368 457 1082 911 462 64 370 1104 1417 1132 116 344