Fenomena Patah Lelah Batang Torak Mesin Kendaraan Niaga

Authors

  • Hadi Sunandrio Balai Besar Teknologi Kekuatan Struktur (B2TKS) - BPPT

DOI:

https://doi.org/10.29122/mipi.v8i2.3649

Abstract

Batang torak (connecting rod) mesin kendaraan niaga mengalami patah di daerahconnecting rod shank, pada saat kendaraan tersebut sedang berjalan.Untuk mengetahui penyebab terjadinya kerusakan tersebut, maka perlu dilakukan pemeriksaan dan pengujian di laboratorium terhadap patahan batang torak tersebut, meliputi : pemeriksaan fraktografi, pemeriksaan metalografi, pengujian kekerasan, analisa komposisi kimia dan pemeriksaan dengan SEM. Dari hasil pemeriksaan dan pengujian diketahui bahwa patahnya connecting rod shankdisebabkan karena mengalami patah lelah (fatigue fracture). Bila dilihat dari luasan area lelah (fatigue area) yang lebih besar dibandingkan dengan sisa patahannya (final fracture), maka dapat diketahui bahwa connecting rod shanktelah mengalami patah lelah akibat beban unidirectional bending, dengan tegangan nominal yang rendah (low nominal stress) tanpa adanya konsentrasi tegangan (no stress concentration). Struktur mikro connecting rod shank adalah ferrite dan pearlite, Dari hasil pemeriksaan komposisi kimia dan pengujian kekerasan menunjukkan jenis materia daril connecting rod shank sesuai dengan spesifikasi yang digunakan, yaitu JIS G 4051 Grade S 20 C.

Kata kunci : Batang torak, Patah lelah, Beban tekuk searah, Tegangan nominal rendah, Tanpa konsentrasi tegangan

Abstract

The connecting rod engine of commercial vehicle was suffering damage on the coneecting rod shank area, while its running. To determine the cause of the damage, it is necessary to do inspection and test on the connecting rod fracture in the laboratory, includes: fractography examination, metallography examination, hardness testing, chemical composition analysis and SEM examination. From the results of inspection and testing are known that the fracture of connecting rod shank caused by fatigue fracture. By observing that extent of fatigue area is larger than the final fracture, shows that the connecting rod shank has suffered unidirectional bending fatigue due to load, with nominal low stress and no stress concentration. Connecting rod shank microstructure is ferrite and pearlite, From the results of the chemical composition and hardness testing indicates the type of connecting rod shank material is in accordance with the specification, JIS G 4051 Grade S 20 C.

Keywords : Connecting rod, Fatigue fracture, Unidirectional bending, Low nominal stress, No stress concentration

References

ASM Metals Handbook, Vol. 12, “Fractographyâ€, American Society for Metals, 2009.

ASM Metals Handbook, Vol. 9, “Metallography and Microstructuresâ€, American Society for Metals, 2009.

ASM Metals Handbook, Vol. 11, “Failure Analysis and Preventionâ€, American Society for Metals, 2009

Charlie R. Brooks, Ashok Choudhury, "Metallurgical Failure Analysis", Mc. Graw-Hill, Inc., United States of America, 1993.

Heinz P. Bloch, Fred K. Geitner,

“Machinery Failure Analysis and Troubleshootingâ€, Gulf Publishing Company, Houston, Texas, 1997.

George E. Dieter, "Mechanical Metallurgy", Mc.Graw-Hill Book Company, New York, 1988.

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Published

2019-07-29