Dual metal crankshaft for heavy-duty engines by cast-joining of DCI and forged steel

Abstract

An alternative design of a crankshaft applicable for heavy-duty diesel engines up to 5000 horsepower has been introduced to achieve cost effectiveness and manufacturing efficiency simultaneously not sacrificing its reliability. Because it is expensive and time consuming to make full-scale prototype and run a test, analytical feasibility study has been made in this paper. From the point of material, cast-joined dual metal for a crankshaft is totally unprecedented and will be realized by virtue of the latest dual metal cast joining of ductile cast iron (DCI) and forged steel, which consequently reduces the manufacturing lead time dramatically. The strength of the dual metal interface is experimentally investigated to make sure its possibility and soundness. The key features of the new crankshaft include crankpins and journals made of forged steel and crankwebs of DCI. Prior to actual manufacturing of the new conceptual crankshaft, the design is analytically examined to verify its reliability in an existing heavy-duty engine. Both conventional and the new dual metal crankshafts are investigated and compared to each other in terms of the stress and fatigue using comprehensive multi-body dynamic analysis. The results demonstrate that the new dual metal approach is likely to provide higher reliability than the conventional monometallic crankshafts. In addition, it is shown that the inferior mechanical properties of DCI for a crankweb are effectively countered by the superior characteristics of forged steel for a crankpin and journal in the dual metal crankshaft.