PSI - Issue 71

Ninad Vasant Pawar et al. / Procedia Structural Integrity 71 (2025) 134–141

138

Integrity 00 (202 ) 000

1 – Initiation zone 2 – Intermediate zone 3 – fast fracture zone

Fig. 5 Overall view of fracture surface with three distinct zones

3.5. Fracture sequence of cone flange The visual and SEM analyses indicate that the fracture started at the groove. The fracture appeared stable initially near the groove surface zone. The symmetry of the fracture surface around the periphery suggested fracture initiation was multi location origin. As the fracture propagated from the groove towards the large face of the cone, it became more unstable, evident from the transitioning of the fracture surface appearance into intergranular fracture mode (refer fig. 6(c) to 6(f)). Presence of beach mark indicate the failure has occurred in fatigue mode. The sectional schematic view of the abutment surface pinion gear, which supports and holds the cone, is shown in Fig. 7. The colored circles show projection of cone bore, groove zone, and flange outer diameter position of cone with on the pinion gear face. The cone flange is supported on eight flat faces of the pinion tooth, whereas there are 8 locations of the tooth space (showed by point y). It is also observed in the 8 unsupported tooth space zones; the groove line is also unsupported (blue circle passing over tooth space). In fig. 1(c), a fracture line is observed towards the root of the pinion gear tooth in the tooth space. In taper roller bearings, part of the total bearing load is taken by the flange along with the track of the cone. In the present case, when rollers are rolling over a cone track from point x to point y (refer to Fig. 7), the flange will experience a change in stress as the cone flange, which is supported at point x, will be in an overhang condition on point y. In the region of unsupported cone flange zone over tooth space, tensile stress is generated on the groove surface. With the rapid movement of rollers as they roll over the unsupported zone from the supported zone of the flange, a spike in stress is expected. This spike can be severe if there is a momentary increase in operating load as the application is a commercial vehicle.