Title: Uncertainties of experimental crankshaft fatigue strength assessment

Authors: Yung-Li Lee, William Morrissey

Addresses: Stress Lab., DaimlerChrysler, CIMS 482-05-34, Auburn Hills, Michigan 48326-2757, USA. Stress Lab., DaimlerChrysler, CIMS 482-05-34, Auburn Hills, Michigan 48326-2757, USA

Abstract: Experimental fatigue techniques provide the most accurate means of determining the crankshaft operating loads and fatigue strength. A safety factor is then calculated by comparing the two variables. Inadequate values indicate the need for crankshaft redesign. In some instances, the test results showed that some engines with a safety factor below 1.0 do not crack and fail during engine dynamometer tests, which implies that the testing method and the safety factor may be overly conservative. What factors are built into the conservative output? What is the right way of conducting this type of component bending fatigue test? What is the acceptable bogey based on the current testing method or the ||right|| method? This paper describes the laboratory procedures for crankshaft load acquisition and fatigue strength evaluation. Moreover, this paper documents the authors| studies and thoughts on the factors that may contribute to the conservative safety factor. The factors to be addressed are the risk associated with the safety factor chosen, the ray-projected test method, the failure criterion, and definition of the fatigue limit.

Keywords: bending; crack; crankshaft; fatigue limit; ray-projection method; risk analysis; safety factor; surface hardness.

DOI: 10.1504/IJMPT.2001.001266

International Journal of Materials and Product Technology, 2001 Vol.16 No.4/5, pp.379-392

Published online: 01 Jul 2003 *

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