Evaluation of a cast-joining process of dual-metal crankshafts with nodular cast iron and forged steel for medium speed diesel engines

Abstract

A new nontraditional way of manufacturing crankshafts for medium speed diesel engines is proposed and evaluated by the state of the art of multibody dynamic analysis. Introduced for the first time in this paper, the new approach makes use of commercially unprecedented dual-metal cast-joining of nodular cast iron and forged steel. The strength of the dual-metal interface is validated by tensile tests with specially prepared dual-metal test coupons. The tensile tests revealed that the tensile strength of the dual-metal interface could be controlled to have over 700 MPa, which provides a fundamental basis to a dual-metal crankshaft. Given the reliable dual-metal cast joining, two dual-metal crankshafts, the so-called DM1 and DM2, are suggested and evaluated for two operational cases: an actual case of 100 bars of gas pressure; and a virtual case of 210 bars of gas pressure. The analysis results of the two cases demonstrated that one of the two dual-metal crankshafts, DM2, showed equivalent or outperforming fatigue performance over the traditional steel crankshaft. Therefore, by virtue of the new materialistic combination and the cast-joining technology introduced in this paper, the dual-metal crankshaft of nodular cast iron and forged steel presents a strong possibility to replace the traditional forged steel crankshaft, which is costly and low productive.