Analysis of the relationship between flow characteristics of crankshaft core and fracture failures of S43CMnV steel

Abstract

The intrinsic correlation between the flow characteristics at the core of the bar and the crankshaft surface cracks for an S43CMnV non-quenched and tempered steel three-cylinder crankshaft is systematically investigated by a combination of material nonlinearity numerical simulations, microstructural characterizations, and bar streamline experiments. The results indicate that the source of the jagged crack is located inside the transition fillet of the rod journal (parting surface) and that the failure mode is fatigue fracture. An analysis of the failure defects based on numerical simulations indicates that the volume of material flowing from the core of the bar to the inside and surface of the rod journals is larger, and that the average grain sizes at the cracks in the core material area are larger. Among them, the maximum displacement at the 1st and 3rd rod journals are 15.9 mm and 19.6 mm, and the average grain sizes in the core material area are approximately 151 μm and 148 μm, respectively, while the 2nd rod journal is approximately 147 μm. A comparison of the three-cylinder and four-cylinder crankshafts of the S43CMnV material under the same process reveals that the volume of the outflowing core material contained in the rod journals of the three-cylinder crankshaft is larger than that of the four-cylinder crankshaft. Moreover, the analysis results for the microstructures and bar streamline experiments indicate the presence of numerous riverine sulfides and other impurities in the crack source area of the rod journals. These impurities mainly originate from the core of the bar, consistent with the simulation results.