IJE TRANSACTIONS C: Aspects Vol. 31, No. 3 (March 2018) 473-479    Article in Press

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K. Aliakbari, N. Safarzadeh and S. S. Mortazavi
( Received: September 09, 2017 – Accepted in Revised Form: October 12, 2017 )

Abstract    The main purpose of this study is to review the cause for the crankshaft failure of six-cylinder diesel engine of a wheel loader after passing a short period of time. The failure had occurred after 4800 hours of in-service in the fifth crankpin of the crankshaft. Hardness and tensile tests were carried out to study their mechanical properties. Spectrophotometer machine was used to examine the chemical composition of the crankshaft material. To examine the material microstructure, its defects and the morphology of fracture surface, optical microscopes (OM) and scanning electronic microscopes (SEM) equipped with energy dispersive spectrometry (EDS) were used. The morphology of fracture surface showed that the fracture is of the smooth type and has occurred due to the fatigue. Main origin of the fatigue cracks appeared on the surface of the crankpin might be created by the existence of oil impurities, the impurities on the surface of the crankpin, inappropriate machining on the surface of the crankpin or severe wear and pitting from insufficient lubricating.


Keywords    Automotive engineering, Wheel loader, Crankshaft failure, Fatigue crack, Failure cause


چکیده    هدف اصلی این مطالعه بررسی علت شکست میل لنگ موتور شش سیلندر دیزل لودر پس از مدت زمان کوتاه است. شکست پس از حدود 4800 ساعت در پنجمین محور لنگ از محل محور لنگ اتفاق افتاده بود. برای بررسی خواص مکانیکی تست‏های سختی و کشش انجام گرفت و از دستگاه اسپکتروفتومتر برای بررسی ترکیب شیمیایی عناصر تشکیل دهنده میل لنگ استفاده گردید. برای بررسی ریزساختار، عیوب، سطح شکست و علت شکست از میکروسکوپ‏های نوری و میکروسکوپ الکترونی روبشی (SEM) مجهز به طیف سنجی پراش انرژی پرتو ایکس (EDS) استفاده شدند. مورفولوژی سطح شکست نشان داد شکست از نوع نرم و در اثر خستگی روی داده است. محل شروع ترک خستگی از سطح قطعه میباشد که عامل آن میتواند حضور ناخالصی ناشی از روغن و یا ناخالصی در سطح محورلنگ، خطوط ناشی از ماشینکاری نامناسب روی سطح محورلنگ و یا سایش شدید و ایجاد حفره در اثر روانکاری نامناسب روی سطح باشد.


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