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COBEM 2017
24th ABCM International Congress of Mechanical Engineering
A FINITE ELEMENT STUDY OF THE INFLUENCE OF GRAPHITE NODULES SIZE ON SUBSURFACE CONTACT STRESSES OF AUSTEMPERED DUCTILE IRON GEAR
Submission Author:
Jaqueline Lazzaron , PR , United States
Co-Authors:
Carlos Henrique Silva, Marco Antonio Luersen, Jaqueline Lazzaron
Presenter: Jaqueline Lazzaron
doi://10.26678/ABCM.COBEM2017.COB17-1680
Abstract
Economic advantages and desirable mechanical properties have motivated academic research involving ADI (Austempered Ductile Iron) to replace traditional alloy steels, like AISI 8620 and AISI 4140, in the manufacture of gears. As known, there are graphite nodules inside the ADI matrix which work as stress concentrators in the evolving matrix during the contact between teeth. Each type of ADI has different nodule count and size, which influence on the properties of these materials. Hence, the aim of this work is to study, through finite element modeling, the influence of size and distance between nodules in order to understand previous experimental wear results with ADI. A finite element model of the gears in contact (called global model) is built and analyzed, followed by two local analyses using the submodeling technique. Two types of ADI with different nodule sizes are considered. The results show that the variation of the nodule size, positioned in the highest shear stress region does not substantially affect the stress concentration factor, reaching approximately 2.363 for all tested diameters. On the other hand, the study reveals that the presence of a second nodule can relieve stress in the nodule neighborhood. It was observed that when the nodule is positioned in the parallel direction to the stress flow lines, distant 0.5 to one diameter from another nodule, the second nodule works reducing the stress of the first nodule. This effect is more intense in ADI with smaller nodule size, which is a possible reason for higher contact fatigue strength of ADI with higher nodule count (and consequently with smaller nodule size), as observed in previous experimental studies performed with spur gears on a FZG equipment.
Keywords
Austempered Ductile Iron, Finite Element Analysis, graphite nodule, contact fatigue, spur gear
