Heavy Duty Truck And Trailer Bearing Failure Analysis

Heavy Duty Truck and TrailerBearing Failure AnalysisAn ISO / TS 16949 Certified Company28397 GBC-Hyatt broch R1.indd 112/23/11 11:36 AM

Company OverviewGeneral Bearing Corporation (GBC)occupies a unique position in thebearing industry. Renowned for itsability to combine quality withcompetitive cost structures, GBC’swinning combination has been usedto establish a first class reputation atOriginal Equipment Manufacturers aswell as the Aftermarket. Withengineering, sales, and logisticslocated in New York, and stateof-the-art manufacturing facilities in China, GeneralBearing is an ISO/TS 16949 certified manufacturerGeneral Bearing Corporation HeadquartersWest Nyack, NYof ball and roller bearings. Under our brands HYATTand THE GENERAL, OEMs and distributors aroundthe world rely on General Bearing Corporation forconsistent, high quality products and service.Industries currently using General Bearing productsinclude: Heavy Trucks Truck Trailers Automotive Electric Motors Industrial Equipment Lawn & Garden Material Handling Office Equipment Power Tools Railroad Recreational Vehicles28397 GBC-Hyatt broch R1.indd 212/23/11 11:36 AM

IndexIntroductionIntroduction ----------------------------------- 3Prior to Installation --------------------- 4Correct Bearing Installation Techniques -------------------------------- 4Failure ModesGrooving ----------------------------------------- 5Pitting and Contaminants --------- 5Excessive Abrasive Wear ---------- 6Etching from Moisture Contamination ------------------------------------ 6Friction Corrosion ------------------------ 6Operating ConditionsMisalignment --------------------------------- 7Static Overload ------------------------------ 7Outer Diameter Damage ------------- 8Effects of Lubrication Starvation ------------------------------------------------ 8Effects of Electrical Current ------- 8Fracture -------------------------------------------- 8Failure AnalysisFailure Modes ---------------------------------- 10-1328397 GBC-Hyatt broch R1.indd 312/23/11 11:36 AM

IntroductionThe size of a bearing has no affect on its resistance to improperoperating conditions, poor handling, or environmental ufacturingtolerances are often not found in other components that are part ofthe same assembly. Modern machining techniques and processeshave managed to keep the cost of bearings low, masking theirvalue as highly precise machine elements.It is a known statistical fact that greater than 90% of all bearingfailures are due to external influences. These include lubricationconditions, assembly installation techniques, contamination of theoperating environment, and improper bearing size selection forthe application.Under proper operating conditions, a bearing should only failfrom fatigue which is predictable based on the bearing size andit’s application parameters.Many other types of bearing damageprevented with theg can be pknowledge of how external influencesaffect the life of a rolling bearing.g.For that reason, we present thishisguide as a reference towardsunderstanding the causesand effects of bearing damage.e.328397 GBC-Hyatt broch R1.indd 412/23/11 11:36 AM

Prior to InstallationBearings should be stored in a clean anddry location without exposure to vibration.Handle bearings with care. A drop from evena low height or a low shock load can causerolling surface brinelling, a starting point forsurface damage.Keep bearings in their original packaginguntil they are installed.Avoid cleaning or degreasing a new bearingas it will remove the preventative rustcoating.Hands should be clean and dry. Gloves arerecommended.The work area should be clean with minimalexposure to contaminant generatingequipment.Never spin a bearing with compressed air.Correct Bearing Installation TechniquesUse only the lubricant chosen for theapplication during installation. Do not mixlubricants.Use the appropriate sized tools for thebearing. Check for tool wear often.Assure that both the shaft and housingseating areas are clean and free fromcontaminants. The dimensions of the shaftand housing as well as any radii contactingthe bearing should be confirmed as correctfor the bearing size chosen.Avoid touching bearing surfaces with barehands as this can lead to surface oxidation.Prior to press fitting, assure the bearing isaligned. Only apply force to the bearing racebeing pressed. For example: Do not crossload the bearing by pressing on the innerrace when the outer race is being fitted.Do not apply shock loads to the bearingduring assembly either through mishandlingor direct use of a hammer.428397 GBC-Hyatt broch R1.indd 512/23/11 11:36 AM

Failure ModesGroovingGrooving occurs when hard contaminants enterthe bearing and get wedged in the cage and cutgrooves in the rollers.Particles can also get caught between rollers andcut grooves in the bearing races.The damage is permanent and will lead to earlybearing failure.Pitting and ContaminantsPitting is damage that is also caused by foreignmaterial such as dirt or metal particles enteringthe bearing.The most likely source of these particles areimproperly cleaned housings.Even light pitting may lead to eventual bearingfailure. Caution should be taken to evaluatewhether lightly damaged parts should bereturned to service.Excessive contaminants and resultingraceway pitting.528397 GBC-Hyatt broch R1.indd 612/23/11 11:36 AM

Excessive Abrasive Wear from ContaminantsExtremely contaminated environments will causeexcessive wear to the point of wearing downroller ends as shown here. Bearing life is severelyreduced in this situation.Abrasive wear occurs when a hard rough surfaceslides across a softer surface.Damage caused by lubricant-borne particles inrolling/sliding contacts can severely reduce theoperational life of ball and roller bearings.Lubricant supplies frequently contain suchcontaminating particles, either generated fromwithin the machinery itself or incorporated into the fluid from the surroundings.Etching from Moisture ContaminationWhen water is allowed to enter the bearingassembly and mix with the system lubricants,a chemical reaction can cause surfaceetching as shown above.Frictional CorrosionSmall vibrations will cause the bearing rollingpathway surfaces to rub together when the bearingis not rotating, such as when an assembly withinstalled bearings are shipped.The rubbing eventually leads to surface oxidationand a failure initiation point.Properly installed bearings with correct clearanceand lubrication can alleviate this.628397 GBC-Hyatt broch R1.indd 712/23/11 11:36 AM

Operating ConditionsMisalignmentMisalignment caused by installtation forces the centerline ofthe inner bearing race (cone) to operate at a slight angle tothe centerline of the outer race (cup).This causes the load to be unevenly distributed creatinggreater than expected stress at one end of the rollingsurfaces.Eventually, this will lead to surface spalling and prematurefailure as shown.The unexpected forces caused by misalignment can extendoutside of the bearing, influencing the bearing matingcomponents and causing other unexpected and unevenwear. In the photos shown here, a misalignment conditionhas caused wear between the cone bore and shaft outerdiameter and caused the bore to have a polished appearance.Static OverloadStatic overload of a stationary bearing from either load orshock will produce true brinelling or permanent plasticdeformation at the rolling element and raceway contactpoints.Excessive preload, improper installation, or improperhandling can all cause this condition.This will lead to premature failure.728397 GBC-Hyatt broch R1.indd 812/23/11 11:36 AM

Outer Diameter DamageIn these photos, grooves and heavy wear onthe outer diameter of the cup indicate that thecup was spinning inside the housing/hub. Thiscondition is most often caused by improper fits ormisalignment.Effects of Lubrication StarvationLack of lubrication in fully loaded bearings willcause prompt and severe failure.Impropermaintenance, installation, and poor sealing areseveral root causes.In addition to the destruction of the roller separatorpictured above, overheating due to high frictionwill affect all bearing components.828397 GBC-Hyatt broch R1.indd 912/23/11 11:36 AM

Effects of Electrical CurrentDue to small internal clearances in the bearing,electrical current can arc between componentsurfaces causing rolling surface pitting. This willeventually lead to failure.Proper grounding techniques should be employedto avoid current passing through bearings.FractureExcessive preload, high shock loads, poorhandling and extreme thermal conditionscan lead to component fracture.928397 GBC-Hyatt broch R1.indd 1012/23/11 11:36 AM

Failure AnalysisFailure ModesISO 15242:2004(E) is a comprehensivedocument on Bearing Failure Analysis.Almost all bearing failure modes can beclassified into one of these six ractureElectricalErosionFailure CausesAlmost all bearing failure causes can beclassified into one of these five ingOperatingCondition1028397 GBC-Hyatt broch R1.indd 1112/23/11 11:36 AM

Lubricant Based Failure CausesAll bearings need proper lubrication to function properly. Lubrication must be correctly selected,be applied to the correct quantity level, be clean, monitored, and maintained g333Scratches3333333333333Increased WearExcessiveLubricantTracksScoresHot RunningPittingSpalling3RustCage Fracture333333IndentationsThermal Cracks333Operating Condition Based Failure CausesOperating conditions must be carefully considered when choosing the proper bearingand determining the bearing’s expected life.Increased uting3Chatter MarksHot RunningPittingSpalling33333333Fretting (Rust)3Fracture CracksCage FractureIndentationsThermal CracksPassage ofElectricalCurrent333333333331128397 GBC-Hyatt broch R1.indd 1212/23/11 11:36 AM

Bearing Mounting Based Failure CausesIncorrect mounting practices can severely shorten bearing life.Faulty ingMisalignment33333333Increased WearScratchesFlutingHot RunningPittingSpallingElectrical Craters333333333Fracture CracksCage FractureDeformationIndentations33Thermal CracksIncreased Uneven seatingSurfaceIncorrectSeating fit33333333333SmearingHot RunningPittingSpalling33333Fretting (rust)Fracture CracksCage FractureDeformationThermal Cracks3333333333333333333331228397 GBC-Hyatt broch R1.indd 1312/23/11 11:36 AM

Application Design Based Failure CausesProper bearing selection, along with thecomponents they are mounted to, will enhancebearing mponentsSmearing33Scratches33Hot Running33Fretting (rust)33Fracture Crack33Cage Fracture33Spalling33Bearing Handling Based Failure CausesBearing handling, storage, and transportationshould follow proper guidelines to avoid rollingsurface damage.IncorrectBearingStorage3ScratchesCorrosion (rust)VibrationDuringTransportation3Fretting (rust)3Indentations31328397 GBC-Hyatt broch R1.indd 1412/23/11 11:36 AM