Clutch Retainer plate Failure

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Failure analysis of a clutch Retainer plate field
Failure
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Type Of failure
Window failure
Damper spring
popping out
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Type Of failure
The clutch Retainer plate was found to have
failed in the field .
Due to the failure the damper spring Popped
out as the plate could not retain the same due
to window failure
This resulted in clutch not working in the
vehicle
Also abnormal sound was reported during the
failure
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Examination of Failure
 The Failed clutch was examined Visually.
 The retainer plate window was found broken and the
piece had got dislodged.
 The damper spring was found coming out of the
window
 The spring was found to have rubbing marks on its
surface
 With careful examination Gouging marks were seen
on drive plate window sides where damper spring
was seated.
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Examination of Failure
Drive plate
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Examination of Failure
 The damper spring is located in drive plate window
and gets retained by retainer plate on both sides.
 The Drive plate window was found to have deep
digging ( Gouging ) on both ends where damper
spring was making contact .
 This was resulting in damper spring getting loosened
and coming out and hitting the retainer plate
 This hitting action was resulting in failure of retainer
plate window.
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Failure Investigation
 Material and manufacturing process for Retainer plate:
 Material : IS 513 ( SAE 1010) type D
 Manufacturing process: Blanking
Heat treatment i.e
Carbonitriding
Zinc Phosphating
 Hardness and case depth were checked for the failed retainer
plate and were found to conform to the specification with no
manufacturing or material defects
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Failure Investigation
 Material and manufacturing process for Drive plate:
 Material : IS 513 ( SAE 1010) type D
 Manufacturing process: Blanking
Heat treatment i.e
Carbonitriding
Zinc Phosphating
 Hardness and case depth were checked for the failed drive plate
The effective case depth was found low due to formation of
intermediate Pearlitic phases in the case.
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Failure Investigation
Pearlite formation in case
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Failure Investigation
 Chemistry was checked for the drive plate and the material was
found to be Aluminum killed
 Material : IS 513 ( SAE 1010) type D. Aluminum : 0.023%
 Use of Aluminum as Deoxidation agent resulted in fine grain size
 The grain size was measured and found ASTM 8-9
 The fine grain size resulted in poor hardenability of the steel
resulting in formation of intermediate phase Pearlite.
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Corrective Action
 While localization, the raw material was developed as Silicon
killed steel in place of Aluminum as deoxidation.
 Material : IS 513 ( SAE 1010) type D.
 The material was blanked and carbonitrided in seal quench
furnace using LPG and endogas.
 The case depth was measured using effective case depth method
by microhardness and also microstructure was analyzed.
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Corrective Action
 The grain size was found 6-7 ASTM.
 Both microstutcure in case as well as effective case depth values were
found conforming to specification.
 Rockwell superficial hardness was measured on components for
around 25 heat treated batches and case depth was correlated witth
superficial hardness
 Ensuring the hardness resulted in attainment of specified case depth.
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Testing and confirmation
 The drive plates were assembled in clutch assembly and were
evaluated for durability in fatigue rig for required number of
cycles
 Few clutch assemblies were tested on vehicles and found to
cover more than 1.5lac cycles compared to earlier failure cases
where life was as low as 20000-30000 kms.
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