(1) MEKANIKA PERPATAHAN

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(1)MEKANIKA PERPATAHAN FAILURE ANALYSIS

• Muhammad Fitrullah
• Teknik Metalurgi
• Fakultas Teknik Universitas Sultan Ageng Tirtayasa

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DEFINISI KERUSAKAN (FAILURE)

• Ketidak-mampuan suatu komponen untuk dapat
  berfungsi sebagaimana mestinya. Perpatahan
  (fracture) tidak perlu harus terjadi.

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KONDISI UMUM KERUSAKAN

• 1. Jika tidak dapat dioperasikan (dijalankan)
• 2. Masih dpt beroperasi, tetapi tidak berfungsi
  semestinya
• 3. Kerusakan serius atau tidak aman untuk
  digunakan

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Failure analysis rules

• The failure investigator has only one objective
  to determine the failure mechanism that caused
  the failure and to use that knowledge to prevent
  another occurrence.
• Start with and maintain an open mind. Emotion
  obscures objectivity and must be edged from the
  investigation.
• The theory, however elegant, must agree with the
  observed evidence, however humble.

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Failure analysis rules?

• The simplest solution is the best solution.
• Having the wrong solution is frequently much
  worse than having no solution.
• Major incidents are often triggered by very minor
  or apparently innocuous details.

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Failure analysis rules?

• Only one thing is worse than knowing you have a
  crack growing in a component, and that is not
  knowing you have a crack growing in a component.
• Cracks never get smaller, nor do they ever
  disappear. Either they stay the same size
  (invariably in a minor, insignificant, or easily
  repaired component), or they get bigger (usually
  in a critical component).

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QUATION FOR SUCCESSFUL FAILURE ANALYSIS

• Proper background information
• correct analyses and tests
• Thorough knowledge of materials behaviour
• and processing
• Pertinent experience
• ______________________
• Correct Analysis

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Penyebab Kerusakan Material
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FAKTOR KEGAGALAN

• 1. SALAH DISAIN
• Apakah ada stress concentration (lubang, ulir,
  notch)
• Apakah Dimensinya sesuai ? Lost by wear or
  corrosion
• Haruskah Rigid atau Flexsible like spring?
• Apakah Part / Komponen memang didisain untuk
  mudah rusak atau memang untuk tahan rusak ?

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FAKTOR KEGAGALAN

• 2. SALAH MEMILIH MATERIAL
• Apakah mechanical prop. sesuai? (Hardness, UTS,
  yield)
• Apakah physical prop. sesuai? (Thermal ex,
  density, cond.)
• Apakah Chemical prop. sesuai? (chem comp.,
  corrosion res.)

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FAKTOR KEGAGALAN

• 3. KETIDAK SEMPURNAAN MATERIAL
• Apakah ada defects pada base metal?
• (porosity, inclusion, lamination, segregation)
• Apakah ada residual stress pada base metal?
  (tension, compression)

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FAKTOR KEGAGALAN

• 4. SALAH DALAM MANUFACTURE (Fabrikasi)
• Rolling ? (lamination, inclusion)
• Welding ? (Pore, undercut, cracks, lack of
  penetration)
• Casting ? (Pore, coldshut, shrinkage,
  segregation)
• Heat Treatment ? (decarburization, scale,
  over/under tempered, improper microstructures)

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FAKTOR KEGAGALAN

• 5. SALAH DALAM ASSEMBLING (PERAKITAN)
• Ada Misalignment ?
• Ada Inaccurate Machining accum. Of tolerance
• ? Interference abnormal stress
• Ada Deflection? (shafts or pipes)

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FAKTOR KEGAGALAN

• 6. KONDISI OPERASI
• Ada unusual occurrence (abnormal)? (bunyi, bau,
  asap)
• Apakah terjadi over speed ?
• Apakah terjadi over load ?
• Apakah lingkungannya korosif? (temperature
  environment)

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Contoh Kerusakan akibat korosi
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FAKTOR KEGAGALAN

• 7. KONDISI PERAWATAN (MAINTENANCE)
• Apakah terjadwal?
• Apakah ada pelumasan?
• Apakah metoda pengukuran baik?
• (temperature, pressure, dimension, etc.)

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Terima Kasih
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Tugas