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Retainer plate Failure

Field failure of a passenger car clutch retainer plate

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Retainer plate Failure

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  1. Failure analysis of a clutch Retainer plate field Failure Materials info consultancy private limitedwww.materials-info.com

  2. Type Of failure Window failure Damper spring popping out Materials info consultancy private limited

  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 Materials info consultancy private limited

  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. Materials info consultancy private limited

  5. Examination of Failure Drive plate Materials info consultancy private limited

  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. Materials info consultancy private limited

  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 Materials info consultancy private limited

  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. Materials info consultancy private limited

  9. Failure Investigation Pearlite formation in case Materials info consultancy private limited

  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. Materials info consultancy private limited

  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. Materials info consultancy private limited

  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. Materials info consultancy private limited

  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. Materials info consultancy private limited

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