Clutch Retainer plate failure

Field failure of a passenger car clutch retainer plate

Transcript

1. Materials info consultancy private limited
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   Failure analysis of a clutch Retainer plate field
   Failure
   

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2. Type Of failure
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   Window failure Damper spring
   popping out
   

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3. 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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4. 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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5. Examination of Failure
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   Drive plate
   

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6. 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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7. 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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8. 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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9. Failure Investigation
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   Pearlite formation in case
   

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10. 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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11. 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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12. 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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13. 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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