image analysis of defects of railway wheels: a …aila/smogen_200408_wheel_damage_ek.pdf · of...
TRANSCRIPT
![Page 1: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/1.jpg)
Image analysis of defects of railway wheels: a challenge for mathematicians
Elena KaboCHARMEC / [email protected]
![Page 2: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/2.jpg)
Overall scope
Railway operations need to ensure
safetyreliability
Railway wheels are safety critical components
regularly monitoredre-profiled as needed
Reprofilingis costlycauses operational disturbancesensures safe operations
∴ Need to classify wheels to ensure optimal reprofilingintervals
![Page 3: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/3.jpg)
ContentsWheel damages –appearances and mechanismsWheel reprofiling –short introductionImage analysis –an overview of some challengesExamples of workshop images
![Page 4: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/4.jpg)
Wheel damage – surface fatigue
![Page 5: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/5.jpg)
Wheel damage – subsurface fatigue
![Page 6: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/6.jpg)
Wheel damage – thermal damage
Heating (due to tread braking) followed by rapid cooling causes tensile surface stressesResult
vertical cracks in typical “dry clay” patternmartensite (white etching layer)
![Page 7: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/7.jpg)
Wheel damage – wheel flats
Formed by a locked wheel sliding on a railPart of the wheel becomes flattenedThermal damage (and martensite) may form at the flatCauses high impact loads that may result in cracking, noise and discomfort
![Page 8: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/8.jpg)
Wheel damage – indentations
Gravel (or other objects) are trapped between the wheel and the railTypically results in smooth pits that are benign (no further crack growth)
RCF
RCF
![Page 9: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/9.jpg)
Wheel damage – wear
Wear occurs from sliding between the wheel and rail, typically in the flange root areaBenign (slow process). Too high wear is monitored by geometry measurements
![Page 10: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/10.jpg)
Wheel reprofilingOwing to surface cracks and/or unacceptable geometry, wheels are reprofiled.Decision based on:
ultrasonic testing (subsurface cracks)measurements (e.g. flange thickness)visual inspection (surface cracks)
Typically 250 000 km between reprofilings≈ 6 times around the earth (depends on operational conditions). Typically three reprofilings before scrapping of the wheel
damage
time
failure
allowed
inspection reprofilingPrinciple between optimumwheel reprofiling intervals
![Page 11: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/11.jpg)
Image analysis – some challenges
Damage identificationseldom a single damage, but a mix with different origins and formed at different times (overlapping may occur)often similar appearance (e.g. indentation and surface fatigue)
a single damage is sometimes owing to a mix of different mechanisms (e.g. a surface crack may be formed due to sliding which causes thermal damage and surface fatigue)
![Page 12: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/12.jpg)
Image analysis – some challenges
Inspection conditionslight conditions may vary between workplacesreflection of light may occurthe surface of the wheels may be dirty and/or corroded
the whole circumference of the wheel needs to be inspected – need for position identificationthe process must be (reasonable) fast owing to operational constraints
![Page 13: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/13.jpg)
Image analysis – outcome
A “perfect” image analysis should be able to identify:
causes of damage (or at least benign vs detrimental)degree of deterioration (e.g. how much of the total circumference is affected and to what degree)
A working image analysis would:
aid the workshop staffimprove the standardization of inspections and classificationsprovide a statistical database of wheel damages
![Page 14: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/14.jpg)
Wheel flat / surface plastification
![Page 15: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/15.jpg)
Surface fatigue and indentations
![Page 16: Image analysis of defects of railway wheels: a …aila/Smogen_200408_Wheel_damage_EK.pdf · of defects of railway wheels: a challenge for mathematicians ... workshop images. Wheel](https://reader030.vdocument.in/reader030/viewer/2022020413/5b7b75807f8b9a483c8e2a95/html5/thumbnails/16.jpg)
Thermal damage