Experimental and numerical study on fretting wear and fatigue of full-scale railway axles
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Experimental and numerical study on fretting wear and fatigue of full-scale railway axles Lang Zou1 • Dongfang Zeng1 • Yabo Li2 • Kai Yang2 • Liantao Lu1 Caiqin Yuan1
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Received: 7 August 2020 / Revised: 21 October 2020 / Accepted: 21 October 2020 Ó The Author(s) 2020
Abstract This study investigated the fretting wear and fatigue of full-scale railway axles. Fatigue tests were conducted on full-scale railway axles, and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed. Three-dimensional finite element models were established based on the experimental results. Then, multi-axial fatigue parameters and a linear elastic fracture mechanics-based approach were used to investigate the fretting fatigue crack initiation and propagation, respectively, in which the role of the fretting wear was taken into account. The experimental and simulated results showed that the fretted zone could be divided into zones I–III according to the surface damage morphologies. Fretting wear alleviated the stress concentration near the wheel seat edge and resulted in a new stress concentration near the worn/unworn boundary in zone II, which greatly promoted the fretting crack initiation at the inner side of the fretted zone. Meanwhile, the stress concentration also increased the equivalent stress intensity factor range DKeq below the mating surface, and thus promoted the propagation of fretting fatigue crack. Based on these findings, the effect of the stress redistribution resulting from fretting wear is suggested to be taken into account when evaluating the fretting fatigue in railway axles. Keywords Railway axle Fretting wear Fretting fatigue Crack initiation Crack propagation Finite element
& Dongfang Zeng [email protected] 1
State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China
2
CRRC Qingdao Sifang Co., Ltd, Qingdao 266111, China
1 Introduction The axle is a highly critical component of a railway vehicle [1–4]. Because it is connected to the wheels via pressfitting, the fretting wear and fretting fatigue usually appear within the region near the wheel seat edge [5–7]. When a crack reaches a critical size, the axle may break with a high risk of derailment. The design standards for railway axles estimate the nominal bending stresses in each section using the classical beam theory and prescribe axles to have an infinite life [8–12]. Nonetheless, the premature failure of a railway axle as a result of fretting fatigue still occasionally occurs. In 2016, fretting fatigue cracks were detected at the wheel seat of a certain type of locomotive axle used in China, leading to the replacement of more than 600 axles [13]. Obviously, the current design cannot fully ensure the safety of railway axles, and the fretting fatigue in railway axles should be further studied. Because of the enclosed structure of a press-fitted axle, some fretting variables that influence the fretting characteristics, such as the local contact pressure and shear stress [1
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