Rail Fatigue Research Articles

Fatigue life assessment of thermite welded rails based on laboratory tests and field measurement data

This in-depth study assesses the fatigue life of thermite-welded 60E1 rails by combining fatigue experimental tests with field measurement data. Material characterization, conducted using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM), aimed to understand the fatigue behavior of these materials. The research was particularly focused on high-speed rail lines in South Korea, targeting areas with influence of track condition to collect strain data. By combining dynamic modulus calculations from high-speed tensile tests with the rain flow counting method for determining wheel loads, and employing the Linear Cumulative Damage method for estimating rail fatigue life, this study provides novel insights into the maintenance and durability of thermite welded rails. The integration of detailed laboratory experiments with field stress data offers a significant contribution to the predictive maintenance and lifecycle management of high-speed railway infrastructure.

Fatigue Crack Characteristics in Gradient Predeformed Pearlitic Steel under Multiaxial Loading

Rolling contact fatigue of railway rails not only severely deforms the surface material near the rail head, but also induces an anisotropy in the mechanical behavior due to work hardening and alignment of the microstructure along the shear direction. Cracks typically initiate in this region and propagate along the aligned microstructure. The fatigue behavior of rails is evaluated under uniaxial loading in the undeformed material state. However, this is not representative of the contact loading condition and material performance after years of service. Herein, the nonproportional multiaxial fatigue of as‐received and biaxially predeformed pearlitic rail steel R260 is investigated. Four material states are investigated, corresponding to the microstructure found at different depths from the severely deformed surface material at the rail head. A starting notch is machined by electrical discharge machining to control crack initiation and allow for comparable surface crack propagation measurements. The crack path is found to be strongly influenced by the degree of predeformation while the early surface crack propagation rate is found to be similar for all material states.

Research on Ultrasonic Guided Wave Technology for the Rail Fatigue Cracks Based on PCA-adaboost.M2 Algorithm

Abstract As a key equipment in high-speed railway operation, rails inevitably produce various fatigue cracks during long-term service, which are major safety hazards in the railway transportation. In order to achieve intelligent detection of the rail fatigue cracks, the PCA-adaboost.M2 algorithm based on ultrasonic guided waves is proposed for the classification and identification of rail fatigue cracks. First, a rail fatigue crack detection system based on an ultrasonic guided wave was established to obtain ultrasonic guided wave signals at different depths of the rail fatigue cracks. Then, five time–frequency domain features of the ultrasonic guided wave (the maximum, the mean, the variance, the center of gravity frequency, and the frequency variance) were extracted, and the five main components of the ultrasonic guided wave were extracted by the principal component analysis (PCA) method and are used for classification and recognition of the adaboost and the adaboost.M2 algorithm, separately. The experimental results show that the ultrasonic guided wave based on the PCA-adaboost.M2 algorithm proposed has good performance in quantitative detection of the rail fatigue crack depth. The ultrasonic guided wave based on the PCA-adaboost.M2 algorithm proposed in this paper provides a method for detecting the rail fatigue crack depth.

Investigation of rail damage considering impact at a welded joint under wet condition

PurposeThe purpose of this study is to develop a transient wheel–rail rolling contact model to primarily investigate the rail damage under wet condition when the train passes through the welded joints.Design/methodology/approachThe impact force induced by welded joints is obtained through vehicle–track coupling dynamics. The normal and tangential wheel–rail contact pressures were solved by elastohydrodynamic lubrication (EHL) theory and simplified third-body layer theory, respectively. Then, the obtained tangential pressure and normal pressure were applied to the finite element model as moving loads, simulating cyclic loading. Finally, the shakedown map and critical plane method were used to predict rolling contact fatigue (RCF) and the initiation of fatigue cracks.FindingsThe results indicate that RCF will occur and fatigue cracks are more prone to appear on the subsurface of the rail, specifically around 2.7 mm below the rail surface in the vicinity of the welded joint and its heat-affected zone.Originality/valueThe cosimulation of numerical model and finite element model was implemented. The influence of surface roughness and fluids was considered. In this model, the normal and tangential wheel–rail contact pressure, the stress and strain and the rail fatigue cracks were obtained under a rail-welded joint excitation.

A peridynamic model for rail crack initiation with cavity defect

Cavity defects can aggravate the rail crack initiation. To study their effect on rail fatigue crack initiation behaviour, a peridynamic model of rail crack initiation considering the characteristics of the cavity defect was proposed. First, based on the low-cycle fatigue test data, the bond failure criterion of the rail material was derived and verified to characterize the fatigue damage performance. Then, mathematical expressions for circular, triangular and rectangular defect characteristics were proposed, establishing a prefabricated method for rail cavity defects. Based on the ordinary state-based peridynamic fatigue theory, a rail crack initiation model with the cavity defect was constructed. Finally, the behaviour of rail crack initiation with the cavity defect was analysed.

Surface treatment of rail to enhance rolling contact fatigue and wear resistance: Combined spot laminar plasma quenching and tempering method

The railway industry faces the challenge of improving the fatigue and wear resistance of rails simultaneously. Laminar plasma quenching (LPQ) can enhance wear resistance but may result in severe rolling contact fatigue (RCF) damage. This study proposes a combined LPQ and tempering method to address this issue and evaluates its effect on rail RCF damage and wear resistance using twin-disc tests. The findings demonstrate that tempering diminishes the grain density and mitigates the lattice distortion in the quenched zone of LPQ rails, thereby enhancing the RCF resistance in that zone. This treatment leads to a substantial reduction in surface fatigue cracks and spalling of the rails and a wear resistance improvement of over one-fold compared to ordinary rails. Thus, this rail surface treatment approach effectively improves both the fatigue and wear resistance of rails simultaneously.

Assessment of residual stresses in railway rails using ultrasonic and Barkhausen noise techniques

Residual stress, a factor affecting the fatigue and fracture characteristics of rails, is formed during the processes of fabrication and heat treatment, and is also generated by shrinkage/tension due to the temperature differences and vertical loads on wheels due to the weight of vehicles. Moreover, damage to rails tends to accelerate due to residual stress caused by the continuous increase in the number of passes and the high speed of passing vehicles. Because this can have a direct effect on safety accidents on railroad rails, having a technique to evaluate and analyse the residual stresses in rails accurately is very important. In this paper, firstly, residual stresses applied in rails were evaluated using longitudinal critically refracted (LCR) wave. Non-destructive stress measurement using ultrasonic techniques is based on calculation of the acoustoelastic coefficient obtained from the relationship between material stress and LCR wave velocity. This is because LCR waves exhibit a relatively large change in flight time in relation to a change in stress compared to other ultrasonic modes. Barkhausen noise technique is also very suitable for measuring residual stresses on railway rails, which are ferromagnetic materials. Tensile and compression tests were performed with the specimens extracted from the inspection object, and the difference between the ultrasonic speed and the magnetization amplitude according to the applied stress was measured. Then, the feasibility of calculating the internal stresses in railway rails using the reference data obtained from the extracted specimens was determined, and the reliability of each method was verified. Furthermore, based on these results, the difference in the results for the loads asymmetrically applied according to the wheel shape was analysed by measuring for each part of new and used rails.

A Method of Quantitative Detection of Fatigue Crack Depth in Bottom Rails by Ultrasonic Guided Waves Based on PCA-SVM

Abstract Ultrasonic guided wave is widely used to detect cracks in rail because of its long propagation distance and small attenuation. To effectively detect the fatigue crack in rail bottom through ultrasonic guided wave, an improved principal component analysis-support vector machine (PCA-SVM) intelligent algorithm based on grid search (GS) is proposed to detect the fatigue crack at different depths of rail bottom. The finite element method is used to establish the model of ultrasonic guided wave at different depths of the rail bottom, and the simulation model is compared with the experimental data to determine the effectiveness of the simulation model. Five main component features of the fatigue cracks at different depths are extracted by PCA. The GS method is used to optimize the penalty factor c and kernel function parameter g in the SVM, and the optimized SVM model is selected to identify the rail fatigue crack at different depths. The combination of theoretical simulation and experimental results shows that the accuracy of the training set and the test set of the improved PCA-SVM intelligent algorithm based on the GS method can reach 99.79 % and 99.73 %, respectively, which provides a basis and method for the detection of the fatigue crack depth of the rail bottom.

Application of the Ultrasonic Guided Wave Technique Based on PSO-ELM Algorithm in the Rail Fatigue Crack Assessment

Abstract Rail safety is very important, and fatigue cracking is one of the important factors affecting rail safety. Therefore, it is an urgent need to develop a safe and effective rail fatigue crack detection technology. Ultrasonic guided wave technology plays an important role in rail detection because of its long propagation distance and small attenuation. In order to realize the quantitative detection of rail fatigue crack, an ultrasonic guided wave technology based on particle swarm optimization–extreme learning machine (PSO-ELM) algorithm for evaluating the rail fatigue crack depth is proposed. The finite element method is used to establish the ultrasonic guided wave model in the rail, and the rail fatigue crack at different depths is simulated. The ultrasonic guided wave selected through the time window function of the excitation signal is used for analysis, and then nine features such as the time domain and the frequency domain of the ultrasonic guided wave are extracted. The PSO-ELM algorithm is used to identify the rail fatigue crack with different depths, and an ultrasonic guided wave-based detection system for the rail fatigue crack is built to verify the relevant theoretical results. The results of finite element simulation and the experiment show that ultrasonic guided wave technology based on PSO-ELM algorithm proposed can quantitatively evaluate the rail fatigue crack with different depths, with an accuracy of more than 99.95 %, which provides an effective method for the rail fatigue crack detection.

Evaluation of fatigue cracks on rail material based on laser nonlinear wave modulation and adaptive particle swarm optimization - support vector machines

ABSTRACT The evaluation of fatigue cracks is essential for the detection of early damage to railway tracks. Laser nonlinear wave modulation spectroscopy using broadband excitation is an effective method for fatigue crack detection that can solve the problem of frequency combination optimisation. However, due to the complex components of laser nonlinear ultrasonic signals, the evaluation of fatigue cracks using laser nonlinear ultrasonic signals remains a challenge. In this study, wavelet packet decomposition and principal component analysis were used to extract various features of nonlinear ultrasonic signals in the frequency domain, and four new combinations of features were obtained. These new features were used as input for the evaluation model. Finally, a fatigue crack evaluation model based on adaptive particle swarm optimisation-support vector machines was proposed to accurately evaluate fatigue cracks of different lengths. The experiments conducted showed that the fourth new combination of features and evaluation model proposed in this paper can improve the accuracy of evaluating rail fatigue cracks of different lengths, reaching a classification accuracy of 97%.

Analysis of Rail Fatigue Crack Initiation under Nonsteady State Loading of Wheel-rail

Analysis of Rail Fatigue Crack Initiation under Nonsteady State Loading of Wheel-rail

Approaches of Finite Element Analysis to Study Fatigue Analysis of Rail-Wheel Contact for Light Rail Transit

Rolling contact fatigue (RCF) is oneof the main rail failure due ofrepeated stresses at rail-wheel contact. The types of defects of RCF such as spalling, squat and head checking occur at surface of rail as possible lead to catastrophic for train derailment. As to reduce the cost of maintenance in using preventative maintenance than corrective maintenance where it crucial to predict the rail fatigue failure through simulation. The objective of this research paper was to predict the cracks at rail surface in 3-dimensional through finite element analysis and in compared results with Hertz theory, alsoto count circlesof fatigue failure with 80000 N against rail.The rail profile selection was R260 as standard rail for light rapid transit. Results demonstrated that the highest von mises stress located at contact patch of rail-wheel, different percent of von mises stress & contact pressureand predicted the rail fatigue regards 339300 circles. Furthermore, this research study has not yet reported and discussed in previous studies for light rapid transit.

Investigation of Dynamic Factor, Rail Stress and Track Foundation Modulus of Ballasted Railway Track for Different Bed Conditions Using Numerical Methods

The track stiffness is the primary function of roadbeds thickness and subgrade characteristics. For this purpose, numerical scale track finite element technique representing the ballasted track with multi layered substructure founded on subgrade was simulated. The track deflection, stress was abstracted in static and dynamic conditions. The track significant design parameters: Foundation modulus, rail fatigue strength, rail bending stress and stress on subgrade levels were evaluated by using improved current track design numerical methods and compared against field test results which were carried out on part of MG Double track high speed main line (1600 km). Mathematical equations were developed to correlate the variables; ballast thickness, settlement, track stiffness, rail bending stress and rail fatigue strength on varying subgrade soil modulus. Incorporation of this parametric study will improve and optimise the conventional track design and maintenance standard. A simple improved track design was introduced by using single track stiffness parameter from conventional plate bearing test (PBT) on Force Displacement (FD) conventional curve method. The improved method with deriving equivalent track stiffness from rail pad and track substructure tested C value are accurate and simple. The current test method to determine the track stiffness in live track condition is expensive and unsafe with operational requirements. This PBT is simple, cost saving on labour, safe and without applying live train load.

Influence of Stress Intensity Factor on Rail Fatigue Crack Propagation by Finite Element Method.

Wheel rail rolling contact fatigue is a very common form of damage, which can lead to uneven rail treads, railhead nuclear damage, etc. Therefore, ANSYS software was used to establish a three-dimensional wheel–rail contact model and analyze the effects of several main characteristics, such as the rail crack length and crack propagation angle, on the fatigue crack intensity factor during crack propagation. The main findings were as follows: (1) With the rail crack length increasing, the position where the crack propagated by mode I moved from the inner edge of the wheel–rail contact spot to the outer edge. When the crack propagated to 0.3–0.5 mm, it propagated to the rail surface, causing the rail material to peel or fall off and other damage. (2) When the crack propagation angle was less than 30°, the cracks were mainly mode II cracks. When the angle was between 30 and 70°, the cracks were mode I–II cracks. When the angle was more than 70°, the cracks were mainly mode I cracks. When the crack propagation angle was 60°, the equivalent stress intensity factor reached the maximum, and the rail cracks propagated the fastest.

Experimental Consideration of Conditions for Measuring Residual Stresses of Rails Using Magnetic Barkhausen Noise Method.

Residual stress, a factor affecting the fatigue and fracture characteristics of rails, is formed during the processes of fabrication and heat treatment, and is also generated by vertical loads on wheels due to the weight of vehicles. Moreover, damage to rails tends to accelerate due to the continuous increase in the number of passes and to the high speed of passing vehicles. Because this can have a direct effect on safety accidents, having a technique to evaluate and analyze the residual stresses in rails accurately is very important. In this study, stresses due to tensile loads applied to new rails and residual stresses remaining in used rails were measured by using magnetic Barkhausen noise method. First, a magnetization frequency and noise band suitable for the rails were selected. Moreover, by applying tensile loads to specimens and comparing the difference in magnetization amplitudes for each load, the stresses applied to the rails by using the magnetic Barkhausen noise method were measured, and the analysis of the results was verified. Based on these results, the difference in the results for the loads asymmetrically applied according to the wheel shape was analyzed by measuring for the head parts of used rails.

Prediction of rail defect development using parametric bootstrapping modified Weibull equations

The railroad industry has historically used the 2-Parameter Weibull equation to determine the rate of rail fatigue defect occurrences and to forecast the fatigue life of railroad rail. However, the 2-Parameter Weibull equation has significant limitations to include inability to analyze segments of track with limited number of rail defects. These limitations are addressed through modification of the traditional 2-Parameter Weibull equation with a novel approach developed from Parametric Bootstrapping. The result is a Parametric Bootstrapping modified Weibull (PBW) forecasting approach. This methodology is applied to rail segments with insufficient numbers of defects to allow for appropriate defect forecasting analysis. Thus, the PBW method provides reasonable estimates of the rate of defects for track segments that have little or no prior defect history. This approach allows for more track to be analyzed and forecasts the probability of rail defect occurrence as a function of key parameters such as cumulative traffic over the rail. A validation of the proposed methodology was performed. Comparison of the output results of over 300,000 track segments with over 200,000 rail defects showed a major improvement in percentage of segments with reasonable Weibull parameters (alpha and beta). This percentage increased from 11% of segments using traditional Weibull analysis to 77% of segments using Parametric Bootstrap modified Weibull approach. These results show that the PBW Analysis approach introduced here offers a more accurate and effective approach to determining the probability of developing future rail defects. This provides a benefit to railroads in planning maintenance of their expensive rail assets.

Experimental investigation on the rail residual stress distribution and its influence on the bending fatigue resistance of rails

This paper presents an experimental study on the residual stress distribution of 60E2 (UIC 60) rails, and its influence on the rail bending fatigue resistance. First, a brief introduction concerning the rail bending fatigue resistance and the rail residual stress distribution is given. Second, an experimental investigation using the sectioning method on the residual stress distribution over the height and in the foot of the 60E2 rails is presented. Third, an experimental investigation on the residual stresses in the rail foot by applying the X-ray diffraction method is elaborated. Afterwards, the results of these two methods are compared. The residual stresses determined with the sectioning method show better consistency with those in literature. Subsequently, the residual stress results determined with the sectioning method are considered with the four-point-bending fatigue results and integrated into a new comprehensive Smith-diagram. As a result, the residual stress distribution is found out to be decisive when determining rail fatigue resistance. It is further concluded that rail bending fatigue resistance shows a good mean-stress dependency when the actual residual stress distribution is considered.

Study on the effect of residual stresses on fatigue crack initiation in rails

Rolling contact fatigue cracks shorten rail service life, and increase costs of rail maintenance and replacement significantly. The aim of the present study is to investigate the effect of residual stresses induced by manufacturing and repeated wheel-rail contact on fatigue crack initiation in rails. To this end, three-dimensional finite element models of rail on-line heat treatment, rail straightening, and wheel-rail contact were established to study the state of residual stresses of on-line heat-treated rails. The effect of residual stresses induced by rail manufacturing and repeated wheel-rail contact on fatigue crack initiation was analyzed based on a fatigue parameter FPmax by Jiang–Sehitoglu low cycle fatigue criterion. Rail fatigue crack initiation mechanism under the combined action of wheel load and residual stresses was studied. The results show that residual stresses induced by rail manufacturing affect the stress state of on-line heat-treated rails after repeated wheel loads. The influence of residual stresses induced by rail manufacturing and repeated wheel-rail contact on the FPmax of rails is significant. However, there is no positive or negative correlation between residual stresses and FPmax of rails under different wheel loads and friction coefficients.

Experimental investigation on rail fatigue resistance of track/bridge interaction

This paper presents an experimental study on the flexural fatigue behavior of the typical high-speed rail profile 60E2 (UIC60) for five million load cycles. A resonant machine was applied to achieve a test program of different load levels with high loading frequency. This investigation focuses on the rail fatigue resistance under multiple minimum stress levels and different corrosion conditions. In comparison with historic investigations of rails for two million load cycles, this new rail profile shows better fatigue behavior even for 2.5 times more load cycles. In the end, a new Smith–diagram for five million load cycles is proposed.

An integrated experimental and numerical method to assess the fatigue performance of recycled rail

Recycling of rail is practised in the railway industry to promote sustainability and economic efficiency. The functional reliability of recycled rail has to be addressed to ensure safe application. Studies on the reliability of railway rails place great emphasis on fatigue failure. However, scarcity of public domain data on recycled rails and limitation of experimental hardware capability has constrained the study on the fatigue of recycled rails. The aim of the investigation is to propose a novel integrated approach for exploring the fatigue performance of recycled rail effectively and efficiently. A high cycle fatigue test was conducted on a recycled rail specimen to obtain data for the validation of the finite element (FE) numerical model. Following this, the FE numerical model was incorporated with the stepwise load increase test (LIT) method. The integrated method gave a more conservative prediction of the fatigue performance than the analytical method. The shot blasting process induced compressive residual stress which affected the specimen’s fatigue performance. This result was demonstrated by the integrated method. Furthermore, this integrated method also successfully reduced the overall required test time. The predicted endurance limit of the specimen was 130.37MPa, accomplishing the BS EN 13674-1:2011 standard.