For the dynamics of wheel/rail and car body, lightweighting of bogie frames is one of main concerns of designers. Lightweighting of the bogie frames may reduce the fatigue strength and life, especially in heavy haul a...For the dynamics of wheel/rail and car body, lightweighting of bogie frames is one of main concerns of designers. Lightweighting of the bogie frames may reduce the fatigue strength and life, especially in heavy haul and high-speed conditions. In this work, full-scale fatigue and fracture experiments are performed to meet the design requirements of bogie frame of a high-speed electrical locomotive. Multi-axial stress-states of some dangerous points are found both in service and numerical calculation. The Von-Mises equivalent stress criterion is used to evaluate the strength. Then crack initiation and propagation detected during the test are described. The reason why the crack growth rate may become slow in the weld structure of the bogie frame is explained using a residual stress concept. Miner's accumulative damage rule and P-S-N curve are used to predict the life of the bogie frame under fatigue and fracture tests. The experimental approach and theoretical analysis give satisfactory results and design information.展开更多
The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendati...The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendation for the allowable strength and lifetime, which hinders the lightweight design of modern railway vehicles. In this study, to ensure the reliability and durability of a brake unit bracket, an attempt was made to integrate the nominal stress method and an advanced damage tolerance method. First, a complex bogie frame was modelled using solid elements instead of plate and beam elements. A hot spot stress region on the bracket was found under an eight-stage load spectrum obtained from the Wuhan–Guangzhou high-speed railway line. Based on the probability of foreign damage, a semi-elliptical surface crack was then assumed for residual life assessment. The results obtained by the cumulative damage and damage tolerance methods show that the brake unit bracket can operate for over 30 years. Moreover, even if a 2-mm depth crack exists, the brake unit bracket can be safely operated for more than 2.27 years, with the hope that the crack can be detected in subsequent maintenance procedures. Finally, an appropriate safety margin was suggested which provides a basis for the life prediction and durability assessment of brake unit brackets of high-speed railways.展开更多
基金Supported by the Key Technologies R&D Programme (No. 85402-02-03)
文摘For the dynamics of wheel/rail and car body, lightweighting of bogie frames is one of main concerns of designers. Lightweighting of the bogie frames may reduce the fatigue strength and life, especially in heavy haul and high-speed conditions. In this work, full-scale fatigue and fracture experiments are performed to meet the design requirements of bogie frame of a high-speed electrical locomotive. Multi-axial stress-states of some dangerous points are found both in service and numerical calculation. The Von-Mises equivalent stress criterion is used to evaluate the strength. Then crack initiation and propagation detected during the test are described. The reason why the crack growth rate may become slow in the weld structure of the bogie frame is explained using a residual stress concept. Miner's accumulative damage rule and P-S-N curve are used to predict the life of the bogie frame under fatigue and fracture tests. The experimental approach and theoretical analysis give satisfactory results and design information.
基金Supported by National Natural Science Foundation of China(Grant No.11572267)Sichuan Science and Technology Program(Grant No.2017JY0216)+1 种基金Open Research Project of State Key Laboratory for Strength and Vibration of Mechanical Structures of China(Grant No.SV2016-KF-21)Open Research Project of State Key Laboratory of Traction Power of China(Grant No.2018TPL_T03)
文摘The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendation for the allowable strength and lifetime, which hinders the lightweight design of modern railway vehicles. In this study, to ensure the reliability and durability of a brake unit bracket, an attempt was made to integrate the nominal stress method and an advanced damage tolerance method. First, a complex bogie frame was modelled using solid elements instead of plate and beam elements. A hot spot stress region on the bracket was found under an eight-stage load spectrum obtained from the Wuhan–Guangzhou high-speed railway line. Based on the probability of foreign damage, a semi-elliptical surface crack was then assumed for residual life assessment. The results obtained by the cumulative damage and damage tolerance methods show that the brake unit bracket can operate for over 30 years. Moreover, even if a 2-mm depth crack exists, the brake unit bracket can be safely operated for more than 2.27 years, with the hope that the crack can be detected in subsequent maintenance procedures. Finally, an appropriate safety margin was suggested which provides a basis for the life prediction and durability assessment of brake unit brackets of high-speed railways.
