Bearing Failure Analysis 3z3l4g
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Bearing Failure Analysis
2013-09-13 ©SKF Slide 1 [Code] SKF [Organisation]
Bearing failure analysis Overview:
•Load path patterns •Failure mode classification •How to secure evidence •Hands-on exercises 2013-09-13 ©SKF Slide 2 [Code] SKF [Organisation]
Bearing failure analysis The best way to become expert is to examine damaged bearings. Evidence will emerge to allow root cause analysis and hence corrective action. Many of ball and roller bearings never attain their calculated life expectancy. .
The calculated life expectancy of any bearing is based on four assumptions:
1.Good lubrication in proper quantity will always be available to the bearing. 2.The bearing will be mounted without damage. 3.Dimensions of parts related to the bearing will be correct. 4.There are no defects inherent in the bearing.
2013-09-13 ©SKF Slide 3 [Code] SKF [Organisation]
Bearing failure analysis Even if all the four conditions are met, the bearing may still fail due to fatigue of bearing material. Three major classifications of premature spalling are lubrication, mechanical damage, and material defects.
2013-09-13 ©SKF Slide 4 [Code] SKF [Organisation]
Bearing failure analysis Most bearing failures can be attributed to one or more of the following causes: 1. Defective bearing seats on shafts and in housings. 2. Misalignment. 3. Faulty mounting practice 4. Incorrect shaft and housing fits. 5. Inadequate lubrication. 6. Ineffective sealing. 7. Vibration while the bearing is not rotating 8. age of electric current through the bearing. 9. Transportation, storage and handling. 2013-09-13 ©SKF Slide 6 [Code] SKF [Organisation]
Load paths
2013-09-13 ©SKF Slide 7 [Code] SKF [Organisation]
Normal radial load zones…
2013-09-13 ©SKF Slide 8 [Code] SKF [Organisation]
Normal radial load zones… Stationary outer ring Rotating inner ring Constant unidirectional loads
2013-09-13 ©SKF Slide 9 [Code] SKF [Organisation]
Normal radial load zones Stationary inner ring Rotating outer ring Constant unidirectional load
2013-09-13 ©SKF Slide 10 [Code] SKF [Organisation]
Combined (radial and axial) load Stationary outer ring Rotating inner ring Constant unidirectional radial and axial loads
2013-09-13 ©SKF Slide 11 [Code] SKF [Organisation]
Pure Axial load
2013-09-13 ©SKF Slide 12 [Code] SKF [Organisation]
Misalignment of outer ring
2013-09-13 ©SKF Slide 13 [Code] SKF [Organisation]
Ovalised outer ring
2013-09-13 ©SKF Slide 15 [Code] SKF [Organisation]
Out of round housing
2013-09-13 ©SKF Slide 16 [Code] SKF [Organisation]
Tight fit - preloading
2013-09-13 ©SKF Slide 17 [Code] SKF [Organisation]
Eccentric radial load
2013-09-13 ©SKF Slide 18 [Code] SKF [Organisation]
Imbalance
2013-09-13 ©SKF Slide 19 [Code] SKF [Organisation]
Failure mode classification
• Causes of failures have identifiable characteristics • Failure mechanisms have identifiable failure modes • Observed damage can identify failure causes
2013-09-13 ©SKF Slide 20 [Code] SKF [Organisation]
Failure modes Fatigue Wear Corrosion Electrical erosion Plastic deformation
Subsurface fatigue Surface initiated fatigue Abrasive wear Adhesive wear Moisture corrosion Fretting corrosion
Excessive voltage Current leakage Overload Indentation Forced fracture
Fracture
Fatigue fracture Thermal cracking
2013-09-13 ©SKF Slide 21 [Code] SKF [Organisation]
Indents from debris Indents by handling
Subsurface fatigue Subsurface fatigue Fatigue Surface initiated fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
• • • • •
Repeated stress changes Material structural Micro cracks under the surface changes Crack propagation Flaking and peeling
2013-09-13 ©SKF Slide 22 [Code] SKF [Organisation]
Fatigue spall
2013-09-13 ©SKF Slide 23 [Code] SKF [Organisation]
Edge loading
2013-09-13 ©SKF Slide 24 [Code] SKF [Organisation]
True brinelling
2013-09-13 ©SKF Slide 25 [Code] SKF [Organisation]
Surface initiated fatigue Subsurface fatigue Fatigue
Surface initiated fatigue
Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 26 [Code] SKF [Organisation]
• Surface distress • Reduced lubrication • Sliding motion • Severity micro cracks
40 µm
Abrasive wear • Progressive removal of material • Accelerating process • Inadequate lubrication • Ingress of dirt particles Fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 29 [Code] SKF [Organisation]
Abrasive wear Adhesive wear
Wear
2013-09-13 ©SKF Slide 30 [Code] SKF [Organisation]
Adhesive wear Fatigue Abrasive wear
Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 32 [Code] SKF [Organisation]
Adhesive wear
• Smearing / skidding / galling • Material transfer / friction heat • Tempering / rehardening with stress • •
concentrations and cracking or flaking Low loads Accelerations
Adhesive wear Fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 33 [Code] SKF [Organisation]
Abrasive wear Adhesive wear
• It is a material transfer from one
surface to another high temperature resulting in tempering and rehardening of material
Temperature discoloration 150° - 177° C (300° - 350° F) 177° - 205° C (350° - 400° F) 205° - 260° C (400° - 500° F) + 260° C
(+ 500° F)
+ 540° C
(+ 1000° F)
• SKF Bearings can be used at temperatures up to 125° C (~ 250° F)
• Higher temperatures may cause loss of Hardness • Loss of 2-4 points of Rockwell Hardness reduces life 50% 2013-09-13 ©SKF Slide 34 [Code] SKF [Organisation]
Corrosion Fatigue
Rust will form if water or corrosive agents reach the in side of the bearing In such quantities that the lubricant can not provide adequate protection.
Wear Moisture corrosion Corrosion
Fretting corrosion
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 35 [Code] SKF [Organisation]
• • •
Oxidation / rust Chemical reaction Etching (water / oil mixture)
Ineffective sealing
2013-09-13 ©SKF Slide 36 [Code] SKF [Organisation]
False brinelling… Fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 37 [Code] SKF [Organisation]
Moisture corrosion Fretting corrosion
• Rolling element / raceway • Micro movements / elastic deformations • Vibrations • Corrosion / wear: shiny or reddish depressions • Stationary: Damage at rolling element spacing • Rotating: Damage exhibits parallel flutes
Fretting corrosion Fatigue Wear Corrosion
Moisture corrosion Fretting corrosion
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 38 [Code] SKF [Organisation]
• Rolling element / raceway • Micro movements / elastic deformations • Vibrations • Corrosion / wear: shiny or reddish depressions • Stationary: Damage at rolling element spacing • Rotating: Damage exhibits parallel flutes
Advanced fretting…
2013-09-13 ©SKF Slide 39 [Code] SKF [Organisation]
Advanced fretting
2013-09-13 ©SKF Slide 40 [Code] SKF [Organisation]
Electrical erosion • High current = sparking • Instant localized heating leads to melting and/or welding
• Craters up to 100 µm
Fatigue Wear Corrosion Electrical erosion Plastic deformation
Fracture
2013-09-13 ©SKF Slide 41 [Code] SKF [Organisation]
Excessive voltage Current leakage
Electrical erosion – excessive voltage
2013-09-13 ©SKF Slide 42 [Code] SKF [Organisation]
Electrical erosion Fatigue
• Low current intensity
Wear
• Shallow craters
Corrosion Electrical erosion Plastic deformation Fracture
Excessive voltage Current leakage
closely positioned
• Development of
flutes on raceways and rollers, parallel to rolling axis
• Dark gray
discoloration
2013-09-13 ©SKF Slide 43 [Code] SKF [Organisation]
Vibration
2013-09-13 ©SKF Slide 44 [Code] SKF [Organisation]
Current leakage
2013-09-13 ©SKF Slide 45 [Code] SKF [Organisation]
Electric current age solutions
Hybrid deep groove ball bearing 2013-09-13 ©SKF Slide 46 [Code] SKF [Organisation]
Insocoat
Overload Fatigue Wear Corrosion
• Static or shock loads • Plastic deformations • Depressions at rolling element spacing • Handling damage
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 47 [Code] SKF [Organisation]
Overload Indentation
Indents from debris Indents by handling
Installation damage
2013-09-13 ©SKF Slide 48 [Code] SKF [Organisation]
Debris denting Fatigue Wear Corrosion
• Localized overloading • Over-rolling of particles = dents • Caused by soft / hardened steel / hard mineral particles
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 49 [Code] SKF [Organisation]
Overload Indentation
Indents from debris
Indents by handling
Handling damage… • Localized overloading • Nicks caused by hard / sharp objects
Fatigue
Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 50 [Code] SKF [Organisation]
Overload Indentation
Indents from debris Indents by handling
Handling damage
2013-09-13 ©SKF Slide 51 [Code] SKF [Organisation]
CRB roller damage
2013-09-13 ©SKF Slide 52 [Code] SKF [Organisation]
Forced fracture… Fatigue Wear Corrosion
• Stress concentration exceeds tensile strength • Impact / overstressing
Electrical erosion Plastic deformation
Forced fracture
Fracture
Fatigue fracture Thermal cracking
2013-09-13 ©SKF Slide 53 [Code] SKF [Organisation]
Forced fracture…
2013-09-13 ©SKF Slide 54 [Code] SKF [Organisation]
Fatigue fracture • Exceeding fatigue
Fatigue
strength under bending
Wear Corrosion
• Crack initiation / propagation
Electrical erosion Plastic deformation
Forced fracture
• Finally forced fracture
Fracture
Fatigue fracture
• Rings and Cages
Thermal cracking
2013-09-13 ©SKF Slide 55 [Code] SKF [Organisation]
Thermal cracking
Fatigue
• High sliding and / or
Wear
• •
Corrosion
insufficient lubrication High friction heat Cracks at right angle to sliding direction
Electrical erosion Plastic deformation
Forced fracture
Fracture
Fatigue fracture Thermal cracking
2013-09-13 ©SKF Slide 56 [Code] SKF [Organisation]
Securing evidence • Collect operating data, monitoring data • Collect lubricant samples • Check bearing environment(s) • Assess bearing(s) in mounted condition • Mark mounting position(s) • Remove, mark and bag bearing(s) and parts • Check bearing seats
2013-09-13 ©SKF Slide 58 [Code] SKF [Organisation]
Conducting the analysis Examine Bearing(s) and Parts
• Record visual observations • Use the Failure Modes to eliminate improbable possible causes and determine the original cause of the failure.
• external resources for assistance, if needed • Initiate corrective action, if desired
2013-09-13 ©SKF Slide 59 [Code] SKF [Organisation]
False brinelling
2013-09-13 ©SKF Slide 60 [Code] SKF [Organisation]
2013-09-13 ©SKF Slide 1 [Code] SKF [Organisation]
Bearing failure analysis Overview:
•Load path patterns •Failure mode classification •How to secure evidence •Hands-on exercises 2013-09-13 ©SKF Slide 2 [Code] SKF [Organisation]
Bearing failure analysis The best way to become expert is to examine damaged bearings. Evidence will emerge to allow root cause analysis and hence corrective action. Many of ball and roller bearings never attain their calculated life expectancy. .
The calculated life expectancy of any bearing is based on four assumptions:
1.Good lubrication in proper quantity will always be available to the bearing. 2.The bearing will be mounted without damage. 3.Dimensions of parts related to the bearing will be correct. 4.There are no defects inherent in the bearing.
2013-09-13 ©SKF Slide 3 [Code] SKF [Organisation]
Bearing failure analysis Even if all the four conditions are met, the bearing may still fail due to fatigue of bearing material. Three major classifications of premature spalling are lubrication, mechanical damage, and material defects.
2013-09-13 ©SKF Slide 4 [Code] SKF [Organisation]
Bearing failure analysis Most bearing failures can be attributed to one or more of the following causes: 1. Defective bearing seats on shafts and in housings. 2. Misalignment. 3. Faulty mounting practice 4. Incorrect shaft and housing fits. 5. Inadequate lubrication. 6. Ineffective sealing. 7. Vibration while the bearing is not rotating 8. age of electric current through the bearing. 9. Transportation, storage and handling. 2013-09-13 ©SKF Slide 6 [Code] SKF [Organisation]
Load paths
2013-09-13 ©SKF Slide 7 [Code] SKF [Organisation]
Normal radial load zones…
2013-09-13 ©SKF Slide 8 [Code] SKF [Organisation]
Normal radial load zones… Stationary outer ring Rotating inner ring Constant unidirectional loads
2013-09-13 ©SKF Slide 9 [Code] SKF [Organisation]
Normal radial load zones Stationary inner ring Rotating outer ring Constant unidirectional load
2013-09-13 ©SKF Slide 10 [Code] SKF [Organisation]
Combined (radial and axial) load Stationary outer ring Rotating inner ring Constant unidirectional radial and axial loads
2013-09-13 ©SKF Slide 11 [Code] SKF [Organisation]
Pure Axial load
2013-09-13 ©SKF Slide 12 [Code] SKF [Organisation]
Misalignment of outer ring
2013-09-13 ©SKF Slide 13 [Code] SKF [Organisation]
Ovalised outer ring
2013-09-13 ©SKF Slide 15 [Code] SKF [Organisation]
Out of round housing
2013-09-13 ©SKF Slide 16 [Code] SKF [Organisation]
Tight fit - preloading
2013-09-13 ©SKF Slide 17 [Code] SKF [Organisation]
Eccentric radial load
2013-09-13 ©SKF Slide 18 [Code] SKF [Organisation]
Imbalance
2013-09-13 ©SKF Slide 19 [Code] SKF [Organisation]
Failure mode classification
• Causes of failures have identifiable characteristics • Failure mechanisms have identifiable failure modes • Observed damage can identify failure causes
2013-09-13 ©SKF Slide 20 [Code] SKF [Organisation]
Failure modes Fatigue Wear Corrosion Electrical erosion Plastic deformation
Subsurface fatigue Surface initiated fatigue Abrasive wear Adhesive wear Moisture corrosion Fretting corrosion
Excessive voltage Current leakage Overload Indentation Forced fracture
Fracture
Fatigue fracture Thermal cracking
2013-09-13 ©SKF Slide 21 [Code] SKF [Organisation]
Indents from debris Indents by handling
Subsurface fatigue Subsurface fatigue Fatigue Surface initiated fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
• • • • •
Repeated stress changes Material structural Micro cracks under the surface changes Crack propagation Flaking and peeling
2013-09-13 ©SKF Slide 22 [Code] SKF [Organisation]
Fatigue spall
2013-09-13 ©SKF Slide 23 [Code] SKF [Organisation]
Edge loading
2013-09-13 ©SKF Slide 24 [Code] SKF [Organisation]
True brinelling
2013-09-13 ©SKF Slide 25 [Code] SKF [Organisation]
Surface initiated fatigue Subsurface fatigue Fatigue
Surface initiated fatigue
Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 26 [Code] SKF [Organisation]
• Surface distress • Reduced lubrication • Sliding motion • Severity micro cracks
40 µm
Abrasive wear • Progressive removal of material • Accelerating process • Inadequate lubrication • Ingress of dirt particles Fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 29 [Code] SKF [Organisation]
Abrasive wear Adhesive wear
Wear
2013-09-13 ©SKF Slide 30 [Code] SKF [Organisation]
Adhesive wear Fatigue Abrasive wear
Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 32 [Code] SKF [Organisation]
Adhesive wear
• Smearing / skidding / galling • Material transfer / friction heat • Tempering / rehardening with stress • •
concentrations and cracking or flaking Low loads Accelerations
Adhesive wear Fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 33 [Code] SKF [Organisation]
Abrasive wear Adhesive wear
• It is a material transfer from one
surface to another high temperature resulting in tempering and rehardening of material
Temperature discoloration 150° - 177° C (300° - 350° F) 177° - 205° C (350° - 400° F) 205° - 260° C (400° - 500° F) + 260° C
(+ 500° F)
+ 540° C
(+ 1000° F)
• SKF Bearings can be used at temperatures up to 125° C (~ 250° F)
• Higher temperatures may cause loss of Hardness • Loss of 2-4 points of Rockwell Hardness reduces life 50% 2013-09-13 ©SKF Slide 34 [Code] SKF [Organisation]
Corrosion Fatigue
Rust will form if water or corrosive agents reach the in side of the bearing In such quantities that the lubricant can not provide adequate protection.
Wear Moisture corrosion Corrosion
Fretting corrosion
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 35 [Code] SKF [Organisation]
• • •
Oxidation / rust Chemical reaction Etching (water / oil mixture)
Ineffective sealing
2013-09-13 ©SKF Slide 36 [Code] SKF [Organisation]
False brinelling… Fatigue Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 37 [Code] SKF [Organisation]
Moisture corrosion Fretting corrosion
• Rolling element / raceway • Micro movements / elastic deformations • Vibrations • Corrosion / wear: shiny or reddish depressions • Stationary: Damage at rolling element spacing • Rotating: Damage exhibits parallel flutes
Fretting corrosion Fatigue Wear Corrosion
Moisture corrosion Fretting corrosion
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 38 [Code] SKF [Organisation]
• Rolling element / raceway • Micro movements / elastic deformations • Vibrations • Corrosion / wear: shiny or reddish depressions • Stationary: Damage at rolling element spacing • Rotating: Damage exhibits parallel flutes
Advanced fretting…
2013-09-13 ©SKF Slide 39 [Code] SKF [Organisation]
Advanced fretting
2013-09-13 ©SKF Slide 40 [Code] SKF [Organisation]
Electrical erosion • High current = sparking • Instant localized heating leads to melting and/or welding
• Craters up to 100 µm
Fatigue Wear Corrosion Electrical erosion Plastic deformation
Fracture
2013-09-13 ©SKF Slide 41 [Code] SKF [Organisation]
Excessive voltage Current leakage
Electrical erosion – excessive voltage
2013-09-13 ©SKF Slide 42 [Code] SKF [Organisation]
Electrical erosion Fatigue
• Low current intensity
Wear
• Shallow craters
Corrosion Electrical erosion Plastic deformation Fracture
Excessive voltage Current leakage
closely positioned
• Development of
flutes on raceways and rollers, parallel to rolling axis
• Dark gray
discoloration
2013-09-13 ©SKF Slide 43 [Code] SKF [Organisation]
Vibration
2013-09-13 ©SKF Slide 44 [Code] SKF [Organisation]
Current leakage
2013-09-13 ©SKF Slide 45 [Code] SKF [Organisation]
Electric current age solutions
Hybrid deep groove ball bearing 2013-09-13 ©SKF Slide 46 [Code] SKF [Organisation]
Insocoat
Overload Fatigue Wear Corrosion
• Static or shock loads • Plastic deformations • Depressions at rolling element spacing • Handling damage
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 47 [Code] SKF [Organisation]
Overload Indentation
Indents from debris Indents by handling
Installation damage
2013-09-13 ©SKF Slide 48 [Code] SKF [Organisation]
Debris denting Fatigue Wear Corrosion
• Localized overloading • Over-rolling of particles = dents • Caused by soft / hardened steel / hard mineral particles
Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 49 [Code] SKF [Organisation]
Overload Indentation
Indents from debris
Indents by handling
Handling damage… • Localized overloading • Nicks caused by hard / sharp objects
Fatigue
Wear Corrosion Electrical erosion Plastic deformation Fracture
2013-09-13 ©SKF Slide 50 [Code] SKF [Organisation]
Overload Indentation
Indents from debris Indents by handling
Handling damage
2013-09-13 ©SKF Slide 51 [Code] SKF [Organisation]
CRB roller damage
2013-09-13 ©SKF Slide 52 [Code] SKF [Organisation]
Forced fracture… Fatigue Wear Corrosion
• Stress concentration exceeds tensile strength • Impact / overstressing
Electrical erosion Plastic deformation
Forced fracture
Fracture
Fatigue fracture Thermal cracking
2013-09-13 ©SKF Slide 53 [Code] SKF [Organisation]
Forced fracture…
2013-09-13 ©SKF Slide 54 [Code] SKF [Organisation]
Fatigue fracture • Exceeding fatigue
Fatigue
strength under bending
Wear Corrosion
• Crack initiation / propagation
Electrical erosion Plastic deformation
Forced fracture
• Finally forced fracture
Fracture
Fatigue fracture
• Rings and Cages
Thermal cracking
2013-09-13 ©SKF Slide 55 [Code] SKF [Organisation]
Thermal cracking
Fatigue
• High sliding and / or
Wear
• •
Corrosion
insufficient lubrication High friction heat Cracks at right angle to sliding direction
Electrical erosion Plastic deformation
Forced fracture
Fracture
Fatigue fracture Thermal cracking
2013-09-13 ©SKF Slide 56 [Code] SKF [Organisation]
Securing evidence • Collect operating data, monitoring data • Collect lubricant samples • Check bearing environment(s) • Assess bearing(s) in mounted condition • Mark mounting position(s) • Remove, mark and bag bearing(s) and parts • Check bearing seats
2013-09-13 ©SKF Slide 58 [Code] SKF [Organisation]
Conducting the analysis Examine Bearing(s) and Parts
• Record visual observations • Use the Failure Modes to eliminate improbable possible causes and determine the original cause of the failure.
• external resources for assistance, if needed • Initiate corrective action, if desired
2013-09-13 ©SKF Slide 59 [Code] SKF [Organisation]
False brinelling
2013-09-13 ©SKF Slide 60 [Code] SKF [Organisation]
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