Influence of high speed on crack propagation path in thin rim gears

Abstract

A B S T R A C T Thin rim gears need accurate design as cracks nucleated at the tooth root fillet may propagate in a safe way (through the tooth) or in catastrophic way (through the rim). Crack propagation direction is mainly influenced by both wheel geometry parameters and crack initiation point. For specific geometry configurations, crack propagation path may be influenced also by other parameters such as the centrifugal load. For this reason, in this work the effect of the centrifugal load (proportional to wheel speed), related to the bending one, has been investigated. The stress field at the tooth root fillet and near the crack has been considered to evaluate the crack initiation point and to explain the propagation direction. This research activity has been carried out by means of numerical models (traditional 2D and 3D finite elements and extended finite elements (XFEM)). Results show that both crack initiation point and crack propagation path are strongly influenced by the centrifugal load entity; this effect is mainly evident in the uncertainty zone of the backup ratio.A = bending stress coefficient B = centrifugal stress coefficient C R = ISO blank factor F = force applied on the tooth at HPSTC H B = rim thickness H T = tooth height L = face width M = normal gear modulus m b = backup ratio m W = web ratio W = web thickness σ b = bending stress σ c = centrifugal stress σ yield = yield stress τ = shear stress

Experimental investigation on crack propagation paths in spur gears

“…On the basis of previous simulations results [1][2][3], it was noted that the crack propagation direction was mainly influenced by both wheel geometry parameters and crack initiation point. Results related to gear models with different web and rim thicknesses were also interpreted in ISO Standard environment [4], relating the crack path to the so called gear blank factor CR, useful in cases of mating gears consisting of rims and webs.…”

“…Results related to gear models with different web and rim thicknesses were also interpreted in ISO Standard environment [4], relating the crack path to the so called gear blank factor CR, useful in cases of mating gears consisting of rims and webs. Results showed that the interaction between web and rim thickness may influence the crack propagation and the corresponding safe or catastrophic failure mode [1][2][3], [5][6].…”

An XFEM-Based Approach to Fatigue Crack Growth in Press-Fit Spur Gears

“…The XFEM was successfully adopted to gears to observe fatigue crack propagation. 4,5,14 In this study, the XFEM was utilized to understand the role of prestressing caused by interference in fatigue crack growth in a spur gear.…”

Optimisation methodology for lightweight gears to be produced by additive manufacturing techniques

“…6 Lightweight gears are mainly studied in the literature about what concerns fatigue strength, crack propagation and gear dynamics. As some examples, Lewicki and Ballarini 7 and Lewicki 8 and Cura`et al 9 investigated the crack path behaviour in thin rim gears. Other works are more related to the fatigue life estimation such as Kramberger et al 10 who investigated the effect of rim thickness on bending fatigue life of a thin rim gear for truck gearbox.…”

“…As some examples, Lewicki and Ballarini 7 and Lewicki 8 and Curà et al. 9 investigated the crack path behaviour in thin rim gears. Other works are more related to the fatigue life estimation such as Kramberger et al.…”