A Stress Analysis on Railway Axle With Fatigue Crack Growth. (original) (raw)

On The Influence of Residual Stresses on Fatigue Fracture of Railway Axles

2010

Influence of residual stresses on the fatigue propagation of cracks represents a major concern for important components subject to complex loading. The purpose of present research is to numerically predict the lifetime of axles used for railway tank wagons in various theoretical conditions. The developed procedure is based on both calculating residual thermal stresses by mean of finite element method, and the number of cycles to fracture, using the closed form solution of NASGRO equation for fatigue. Calculations of fatigue resistance are based on fatigue crack development starting from an initial crack detectable by means of non9destructive testing. The numerical prediction of number of cycles (or kilometers) to fracture for axles belonging to railway tank wagons has proved the deep negative impact of residual thermal stresses introduced by poorly controlled heat treatments or other processing procedures.

The analysis and prevention of failure in railway axles

International journal of fatigue, 1998

Axles are one of the most important components in railway vehicle with regard to safety, since a failsafe design is not available. To maintain the safety record of high speed railway systems, the fatigue strength of the axles has been extensively studied. The objective of the present paper is to review and analyse the causes of failure in railway axles, and to show how the results have been applied to improve axle manufacture and in-service inspection. The problems of fretting fatigue crack initiation at press-fitted axle parts is emphasized, however, these problems have not been completely solved even though up-to-date fatigue design methods are employed. The safety of the railway has been ensured by maintenance such as the regular inspection for fatigue cracks at critical parts.

Fatigue lifetime estimation of railway axles

Engineering Failure Analysis, 2017

The railway axles are subjected to cyclic loading during their operation. Their load is of long-term nature, therefore a real risk of fatigue failure exists. This failure could lead to derailment of the whole train with serious consequences. To prevent such scenario, the railway axles have to be safely removed from operation before their final failure occurs. This paper presents methodology for the residual fatigue lifetime prediction of the railway axle based on the linear elastic fracture mechanics concept. The methodology contains estimation of the critical position of initial crack, prediction of the fatigue crack front shape development during crack propagation, separation of the bending and press-fitting contributions to the axle load, experimental measurement of the crack growth kinetics of EA4T steel and subsequent estimation of the residual fatigue lifetime of railway axle. Part of the presented study is also devoted to the probability aspects of determination of material characteristics describing fatigue crack propagation and retardation effects caused by existence of plastic zone ahead of propagating fatigue crack. Described methodology is already applied in the design process of new railway axles in Bonatrans company.

Analysis of fatigue fracture of tank wagon railway axles

2010

The paper is focused on the fracture mechanism of railway axles due to the fatigue of material. The purpose of the present article is to numerically predict the number of cycles (or kilometers) to fracture of tank wagon railway axles in various theoretical conditions. The stresses in the axles were calculated by finite element methods. The number of cycles to fracture was calculated using closed form solution of NASGRO equation for fatigue crack development starting from an initial crack detectable by means of non-destructive testing. In order to demonstrate the deep negative impact of forbidden thermal treatments and operations applied to railway axles, residual stresses of these treatments were calculated and new numerical predictions of number of cycles to fracture have been made.

Numerical study on fatigue crack growth in railway wheels under the influence of residual stresses

Engineering Failure Analysis, 2015

Accurate prediction of fatigue crack growth on railway wheels and the influence of residual stresses by finite element method (FEM) modeling can affect the maintenance planning. Therefore, investigation of rolling contact fatigue and its effect on rolling members life seem necessary. The objective of this paper is to provide a prediction of rolling contact fatigue crack growth in the rail wheel under the influence of stress field from mechanical loads and heat treatment process of a railway wheel. A 3D nonlinear stress analysis model has been applied to estimate stress fields of the railway mono-block wheel in heat treatment process. Finite element analysis model is presented applying the elastic-plastic finite element analysis for the rail wheel under variable thermal loads. The stress history is then used to calculate stress intensity factors (SIFs) and fatigue life of railway wheel. The effect of several parameters, vertical loads, initial crack length and friction coefficient between the wheel and rail, on the fatigue life in railway wheels is investigated using the suggested 3-D finite element model. Three-dimensional finite element analysis results obtained show good agreement with those achieved in field measurements.

An Analysis about the State of Stress in a Railway Axle

Analele Universităţii Eftimie Murgu Reşiţa. Fascicula de Inginerie, 2007

This paper presents the researches made by the authors in order to detect damages in beams using natural frequencies by applying the superposition principle. The chosen type of beam was the cantilever one, for which a database containing the first ten natural frequencies in undamaged state was realized. The database was completed with the first ten natural frequencies of the beam with one damage in 200 points and 3 levels of severity. The resulted frequency shift for each place of the damage was used to create a pattern, in order to describe the behavior of the damaged beam. The natural frequencies were determined using the Finite Element Method (FEM). Finally, two damages on the beam were modeled and analyzed and the superposition principle was applied and compared with the analyzed cases for the beam with one damage.

Development of a Numerical Chain to Optimize Railway Axles with Respect to Fatigue Damage

Key Engineering Materials, 2014

In today's competitive business environment, it has become increasingly important to reduce manufacturing and raw materials cost. For this purpose, an innovative process of design and manufacturing railway axles is developed. It is based on forging hollow axles which allows a significant reduction in steel consumption. In this work, we tried to analyze how these modifications induced by this new process and design impact the service behavior and particularly the durability face to cyclic loadings that can lead to fatigue failure. In the present study, a numerical chain has been developed going from the simulation of the manufacturing process up to the analysis in fatigue. In the first step, the forging process is modeled in order to predict the residual stress field and the initial plastic strain. From this initial condition, the assembly operation of the wheel on the axle is simulated before the redistribution of stresses and strains under cyclic load. The final objective is to...

Fracture mechanics and scale effects in the fatigue of railway axles

Fatigue of railway axles is one of the basic problems of fatigue. However, in spite of the criticality of this component, modern approaches have not been used for addressing a critical revision of traditional design. The scope of this paper is to study the scale effects in fatigue limit and in crack growth rate for a high strength steel used for high speed railway axles.

A railway wheel evaluation under multiaxial loading conditions

MATEC Web of Conferences, 2019

Railway mechanical components are subject to thousands of fatigue cycles. Fatigue damage and life assessment is still an open issue. Under service multiaxial loading conditions several challenges can arise. In this study an evaluation of a railway wheel material is performed, i.e. the material properties and the working conditions are taking into account and evaluated. Different mechanical tests are carried out, namely fatigue tests under uniaxial (LCF+HCF) and biaxial (HCF) conditions, applied to several specimens made from the railway wheel. Multiaxial fatigue models were considered regarding the fatigue life estimation. Moreover, fatigue crack plane measurements were compared with estimations from several critical plane models. The applied models provided very satisfactory results, regarding the fatigue life estimation and the initial crack initiation plane under the multiaxial loadings conditions.

Fatigue analysis of railway wheel using a multiaxial strain-based critical-plane index

Fatigue & Fracture of Engineering Materials & Structures, 2017

A fatigue damage model to assess the development of subsurface fatigue cracks in railway wheels is presented in this paper. A 3-dimensional finite element model (FEM) is constructed to simulate repeated cycles of contact loading between a railway wheel and a rail. The computational approach includes a hard-contact over-closure relationship and an elastoplastic material model with isotropic and kinematic hardening. Results from the simulation are used in a multiaxial critical-plane fatigue damage analysis. The employed strain-based critical-plane fatigue damage approach is based on Fatemi-Socie fatigue index that takes into account the non-proportional and out-of-phase nature of the multiaxial state of stress occurs when a railway wheel rolls on a rail. It predicts fatigue-induced micro-crack nucleation at a depth of about 3.7 mm beneath the wheel tread, as well as the crack plane growth orientation which indicates the possible failure pattern. Additionally, the influence of various factors such as contribution of normal stresses, higher wheel load, and material model have been investigated. KEYWORDS critical-plane approach, multiaxial fatigue, railway wheels, rolling contact fatigue (RCF), subsurface fatigue crack, vertical split rim (VSR) 1 | INTRODUCTION Technological advancements in the railway industry have made it possible to significantly extend the fatigue life of wheels. Simultaneously, current economical and logistical constraints demand increasing train speeds and load capacities that result in larger contact forces on wheels. As a result, longer wear periods, higher speeds, and larger loads have made fatigue the main cause of railway wheel replacement and re-engineering. 1 There are roughly 25 to 50 million railway wheels in operation in the world. Considering an annual failure rate of one in 1000, it means 25 000 to 50 000 wheel failures every year. It's obvious that if "failure" here means a complete fracture of the wheel the way the train to be inoperative, railways would not be an efficient method of transportation. 2 According to the Union Pacific Railroad wheel fracture database, 65% of railroad wheel failures are caused by shattered rims, 3 a form of subsurface initiated Nomenclature: C k , =initial kinematic hardening modulus; E, =modulus of elasticity; FS, =Fatemi-Socie fatigue index; G, =shear modulus; Q ∞ , =maximum change in the size of the yield surface; S, =deviatoric stress tensor at the material point of interest; b, =yield surface development rate; Δγ max , =maximum shear strain range in a cycle; α dev , =deviatoric part of the back-stress tensor; γ k , =kinematic hardening modulus decreasing rate; _ ε pl , =rate of plastic flow; _ ε pl , =equivalent plastic strain rate; η, =normal coefficient (an empirical material constant); ν, =Poisson's ratio; σ| 0 , =yield stress at zero plastic strain; σ n , =maximum normal stress in a cycle; σ y , =yield stress; τ ′ f , =Fatigue strength coefficient