Numerical Analysis of the Influence of Graphite Nodule Size on the Pitting Resistance of Austepered Ductile Iron Gears

Abstract:

In this work, an experimental study of wear evaluation in combination with a finite element analysis (FEA) was carried out for austempered ductile iron (ADI) used in gears. Two different ADI materials were used to produce gears which were tested in a FZG back-to-back test rig. The experimental results were compared to those of carburized AISI 8620 steel and induction hardened AISI 4140 steel gears. The wear resistance for pitting and spalling on the gears surfaces were measured using image analysis. Comparing the two types of ADI, the one with smaller nodules showed a higher pitting resistance. In contact fatigue tests with severe load, the carburized AISI 8620 steel proved to be superior to ADI. However, ADI with smaller nodule size presented wear resistance similar to that of induction hardened AISI 4140 steel. The FEA was conducted using the commercial code ANSYS 11.0 and aimed to provide a better understanding of the microstructural effect on the stress state of subsurface regions. From the numerical results in ADIs, it was concluded that the nodule size affects the gears life independently of the mechanical properties of the matrix. The size and number of nodules affects both the nucleation and the propagation stages of cracks. ADIs with higher amount of nodules have a superior wear resistance by pitting. Also, compared to the Hertz contact theory (valid for isotropic materials), the presence of graphite nodules induced the maximum shear stress point moves toward the surface.

• Periodical: Advanced Materials Research (Volumes 1120-1121)
• Pages: 763-772
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1120-1121.763
• Online since: July 2015
• Authors: Luiz Henrique Accorsi Gans*, Wilson Luiz Guesser, Marco Antonio Luersen, Carlos Henrique da Silva
• Keywords: Austempered Ductile Iron, Finite Element Analysis, Gears, Graphite Nodule, Pitting Tests

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