PSI - Issue 18

Goran Vukelic et al. / Procedia Structural Integrity 18 (2019) 406–412 Vukelic, Pastorcic, Vizentin/ StructuralIntegrity Procedia 00 (2019) 000–000

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Fig. 7. Spiral bevel gear pair: a) pinion damaged flanks, b) pinion damaged tooth tip.

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undamaged flank damage teeth tip damage

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Pinion angular position (°)

Fig. 8. Time varying mesh stiffness (TVMS)

4. Discussion and conclusion Visual examination of the failed spiral bevel gear damage evolving around gear teeth. This damage was probably caused by the mismatch between the gear and the pinion designed axial lines causing unwanted contact between the bodies. This contact resulted in raising the stress points along the gear teeth and excessive stress gradually worn out the surface of the teeth. This tends to be the case of gear tooth spalling. Spallings are a product of extremely high localized contact stresses that act as damage initiators and they tend to develop in the region near the pitch circle of the tooth surface where the tooth pair is subjected to a higher mesh force. As the analysis showed, gear was made of special alloy structural steel 28NiCrMoV8-5. It is a common choice for manufacturing gears exposed to heavy duty tasks. This steel with somewhat elevated content of nickel and chromium. Chromium at steels tends to increase tensile strength, hardness, toughness, resistance to wear and corrosion, while nickel increases strength and hardness without sacrificing ductility and toughness. It can also increase resistance to