Rail Stress Research Articles

Influence of Rail-End Bolt Hole Position and Clearance on Stress and Displacement of Rail Using Finite Element Analysis

Influence of Rail-End Bolt Hole Position and Clearance on Stress and Displacement of Rail Using Finite Element Analysis

Numerical and experimental investigation on critical stresses due to rail cant

The track integrity is significantly affected by the internal stress state of the rail. The rail cant influences the flexural stress distribution on the rail foot, thereby shifting the critical stress locations. In this study, full-scale lab testing was done for heavy equivalent wheel loads (16–40 tonne) to measure the rail foot stresses. Further, the mathematical model for track design is modified considering the effect of rail cant on stress distribution and compared with the developed finite element model (FEM) and the experimental study conducted. It was observed that the FEM and modified model calculates the rail stresses with better accuracy of around 5% for heavy wheel loads. The rail cant cause redistribution of stresses, making the gauge corner critical to rail failures. It was observed that stresses at the gauge corner are 20% higher than at the field corner of the rail foot.

Quantifying the effect of fixed structures on rail stress management: A numerical investigation

From 2012 to 2021, FRA accident data indicate that there have been 132 derailments caused by track buckles. Out of the 132 total derailments, 59 (or 45 %) occurred within 152 m (500 ft.) of a fixed structure. Therefore, this paper presents, validates, and applies a 3D finite element-based model to study the effect of the fixed structure on the rail gap size given a rail break. Specifically, the model was used to quantify the effect of the: 1) temperature differential between the rail neutral temperature (RNT) and the actual rail temperature (dT), 2) distance of the cut to the fixed structure, and 3) fixed structure length and anchoring patterns (ETA and EOTA). Model results indicated that at low dTs (e.g., <13.9ºC (25ºF)) the effect of the fixed structure can be considered if the cut occurred at the edge of the fixed structure with EOTA anchoring pattern and the fixed structure length of at least 18.3 m (60 ft.). At a dT of 22.2ºC (40ºF), the fixed structure should be accounted for when there is an edge cut. At extreme dTs (e.g., > 44.4ºC (80°F)) the fixed structure should be considered if the cut occurs within 152.3 m (500 ft.). Therefore, it is recommended that railroads refrain from strictly following open track guidelines for CWR (continuous welded rail) management and rather, consider the influence of fixed structures in relevant situations.

Numerical analysis of concrete tub at-grade crossing rail structure

This study investigates the stresses developed at the rail transition adjacent to concrete tub crossings at varying train speeds. A finite element analysis (FEA) model was developed and validated with field data acquired from a concrete tub at-grade crossing located in Wyoming, USA. In addition to train speed, the model evaluates the influence and contributions of ties, ballast, and base materials beneath the rail structure used to provide support. The results show the train's speed does not have a critical effect on the rail's stress levels. However, the condition of the ballast adjacent to the concrete tub influences the behavior of the rail. Rail structures supported by ballast with relatively low modulus or displaced materials are subject to increases of stress up to 65 %, due to larger deflections in the supporting materials.

Vibration analysis of double elastomer layered superstructures with extended locally continuous support model

In this study, a distributed rail pad (RP) model of rail supported by double elastomer layers for rigid superstructures like light metro is presented, and a semi-analytical solution is derived via the Galerkin's method. Apart from existing distributed RP models that contain multiple individual spring-dampers, the proposed method offers locally continuous rail bedding. The new model assumes that the rail bedding is not pointwise and connects the continuous bedding and lumped baseplate mass with a derived function, which is the first novelty of the paper. Results of the single-spring model (SSM) and extended locally continuous support models (ELCSM) are obtained and compared to indoor and outdoor measurements in the time and frequency domains. The proposed model shows similar results to the conventional model for dynamic response; however, the clear difference between the models is seen at high resonant frequencies because of the stiffer bedding of the rail. Another point is that rail stresses and displacements can be calculated more accurately compared to SSM, due to including the length of RP. The findings of the study highlight the importance of considering RP length and stiffness when designing and maintaining railway tracks and provide insights into how to optimize these parameters for better performance and durability.

Birefringence Technique for Evaluating Thermal Stresses in Railroad Rails

This paper discusses the development of an in situ noncontact electromagnetic acoustic transducer (EMAT) nondestructive evaluation technology to determine rail neutral temperature and estimate rail stress in continuous welded rail (CWR). Stresses develop in CWR due to a lack of expansion joints to accommodate thermal expansion and contraction of the rail when ambient temperatures vary over time. The novelty of the work presented is the usage of ultrasonic birefringence properties using EMATs to estimate thermally induced stresses in rails. EMATs produce polarized shear waves propagating through the rail web in the pulse-echo mode. Experimental tests were performed on machined 136RE and 141RE rail material with applied compressive and tensile stresses to explore the stress-birefringence behavior. Two additional sets of experimental tests were conducted on full-size rail sections with in situ surface conditions to study variations in the in situ birefringence and the acoustic stress constant in different rail materials including 115RE rail, 119RE rail, two different 136RE rails, and 141RE rail. The results show a highly linear relationship between the stresses applied and the measured acoustic birefringence.

Predicting Axial Stress State In Continuously Welded Rail Using Impulse-Generated Vibration Measurements

Continuously welded rails are connected without stress relief joints and, thus, thermally induced rail movement is constrained, which can result in the development of excessive axial stress and risk of rail failure. Nondestructive testing (NDT) methods that estimate in-place rail stress state or rail neutral temperature are desired. Some methods have been developed, but none satisfy the requirements for ideal monitoring in practice. We propose an NDT technique based on impulse-generated vibration, seeking high-frequency rail vibration resonances whose frequency maintains a consistent correlation with rail axial stress/strain across different temperatures, stress states, and rail support conditions. Rail temperature, axial strain, and vibration data were collected from an active Class 1 commercial rail line over a period of nearly two years. The frequencies of four consistent and clear resonance modes of the rail were monitored. One of the identified modes demonstrates a unique linear relation with axial strain across a range of temperatures and stress states at each of the two measurement locations. The developed linear relations were used to predict in-place strain and rail neutral temperature with acceptable accuracy across all the measurement data, although each test location exhibits a unique relation.

Study of Rail Structure Interaction on Double-Decker integrated bridge with Metro and Highway Structure

In the metro rail system, Long Welded Rails (LWR) have been used for less maintenance, smooth &amp; safe ride at higher speeds. The arrangement of connecting rail and deck system causes an interaction effect in force transfer. The study of this effect in the structure is Rail Structure Interaction (RSI) analysis. In this study, the behavior of double-decker integrated structure, rail stresses and relative deformation are studied due to the bending behavior of the deck, bearing articulation &amp; support stiffness with the proposed geometrical arrangement of the bridge and applicable loading as per standards. The effect of RSI analysis and limitations of additional stresses are referred with the guidance of UIC standards &amp; RDSO guidelines. The double-decker elevated viaduct structure is proposed with a first level highway deck carrying highway loading and second level metro system carrying metro loading. In highway bridge deck, the decks are proposed with four span continuous to avoid discomfort due to more number of expansion joints and thereby provide smooth riding for passengers. The effect of RSI is studied in this paper by considering the above complexity of two-level superstructure with a different type of superstructure at the metro level due to the track requirement like U girder deck system at each track, I girder deck system as a single deck for both the tracks at the cross over / pocket track locations and I girder deck system at highway level with deck continuity. A finite element analysis is performed using the analytical tool MIDAS CIVIL software to study the interaction mechanism for this double-decker bridge structure. For this study, rail and deck (unballasted) are linked with a multilinear elastic spring as recommended in UIC 774-3R and other boundary conditions as per IRS &amp; IRC standards. This paper discusses the behavior of structure from the results of the rail stresses and forces to the substructure due to thermal and live load effects at both level Metro Rail system and Highway Road systems.

Analytical and numerical study of hot rolling railway rail sections with the help of simulation and finite element software

Hot rolling of sections is one of the metal forming processes used to shape materials into profiles with a fixed cross-section, such as road rails. Iron is chosen for this process due to its repeatability. Despite the numerous equipment and high costs associated with it, the analysis of this process and its simulation can be highly desirable. In this process, the initial raw piece is passed through several rollers until the desired section's shape is created (1,2). The more passes are made, the greater the reduction in the cross-sectional area, and the tolerances increase. During rail rolling, several key factors play a crucial role, including the length of the workpiece, cross-section change, piece deviation, roller speed, and friction. This article focuses on investigating the effective parameters in this process using simulation software. For the rolling analysis, we use an isothermal and rigid model of rollers, considering the heat transfer between the rollers and the rail during the shaping process. The analysis is performed using thermal stress solutions in Abaqus/explicit. Additionally, the workpiece may deviate due to the asymmetry of the top and bottom shapes. Hence, we examine the effects of the friction coefficient between the part and the rollers on rail deflection, stress values, strain, and rolling force. The results indicate that the maximum stress on the rail's surface occurs below the points of contact with the rollers, leading to a higher percentage reduction.

Nondestructive determination of longitudinal rail stress from guided wave dispersion properties

The determination of the longitudinal stress in continuous welded rails is essential for the safe operation of high-speed railways. Guided wave inspections have many advantages, and can provide an effective tool for non-destructive measurements of the longitudinal stress in rails. This paper provides a new method for determining longitudinal rail stress using ultrasonic guided wave dispersion properties. First, the characteristic equations of guided waves propagating in a waveguide with existing longitudinal stress are constructed, generating the dispersion properties of the waveguide such as the wavenumber, phase velocity and group velocity. The sensitivity of the dispersion properties of propagative modes to the longitudinal rail stress is investigated, which is then used for selecting appropriate modes for guided wave inspections. On the basis of the perturbation method, the relationship between the change in longitudinal rail stress and the change in dispersion properties is developed, which can be used for determining the longitudinal rail stress from dispersion properties. Furthermore, a mode selection index considering both the stress sensitivity and mode shape characteristics is employed for selecting appropriate propagative modes for guide wave inspections. Finally, a numerical example for CHN60 rail is adopted to demonstrate the effectiveness of the proposed method. From the results, the proposed method can accurately determine the longitudinal stress in the rail by using the dispersion properties available.

Effect of Critical Factors Influencing Longitudinal Track Resistance Leveraging Field Experimentation

As extreme temperatures increase, there is an increased need to ensure that continuous welded rail (CWR) stresses are more accurately set and better maintained. Therefore, to improve the management of CWR rail stresses and to increase safety through the reduction of buckled track derailments this paper documents the results from a field experimentation program of controlled single rail breaks (SRBs). SRBs were conducted at multiple field site locations to quantify the longitudinal resistance on both timber and concrete sleeper track. Accurate longitudinal resistance values are critical, because if the wrong value is selected, the rail neutral temperature could easily be set to a low value, increasing the probability of a track buckle or rail pull-apart, further compounding the impact of extreme temperatures. The results presented quantify the effect of sleeper and fastener type as well as ballast consolidation, and compare them with relevant results from the literature. From this, it was found that well-maintained concrete sleeper track exhibited a longitudinal resistance greater than the currently recommended value. Further, well-maintained timber sleeper track with anchors on every other sleeper exhibited a longitudinal resistance 44% lower than concrete sleeper track and 30% lower than timber track with anchors installed on every sleeper. Additionally, disturbing the ballast reduced the longitudinal resistance by 15%. Finally, the results indicated that slip was primarily occurring at the rail–sleeper interface for unanchored timber sleepers and at the sleeper–ballast interface for anchored timber sleepers and concrete sleepers.

Track‐Bridge Interaction: Influence of Transition Zone on the Stability of Continuous Welded Rail

AbstractRealization of high‐speed rail track demands continuous welded rail (CWR) to be laid on bridges without providing special expansion joints. In India, the existing rail bridges must be evaluated for their suitability for upgradation to CWR. CWR Inherently develops axial stress on account of the surrounding temperature changes. CWR in track‐bridge transition zone is subjected to additional stress and displacements as a result of track‐bridge interaction (TBI). Longitudinal thermal loading is a major source of rail stress and substructure forces due to TBI. Also, TBI results in accumulation of large compressive stress in transition zone. Further, the tamping effect in the transition zone by passing vehicles due to sudden change in vertical stiffness weakens the transition zone ballast. CWR is a slender steel element prone to buckling under large compressive stress. A numerical model is developed for track bridge interaction phenomenon in SAP2000 considering the aspect of CWR track buckling. In this study, the developed model is utilized to perform nonlinear buckling analysis to assess the influence of change in ballast stiffness on CWR stability in transition zone. Also, the influence of missing ballast contact raising from ballast subsidence locally in the transition zone was investigated. A single span simply supported steel bridge is considered. Longitudinal thermal loading is considered in this study. CWR supported on the ballasted track is considered. Material Nonlinearity associated with ballast is considered. Maintenance of CWR track is found to play a key role in track stability as the loose ballast or missing of ballast underneath the rail sleeper is to introduce discontinuity in CWR track support and reduces the critical buckling temperatures of the track considerably. Overall, this study contributes to the understanding of track‐bridge interaction and the stability of CWR in the transition zone.

Permissible Additional Stress in Rail and Preventive Measures

Permissible Additional Stress in Rail and Preventive Measures

Rail-structure interaction and vehicle-track-structure interaction level 1 and 2 analyses

Rail-structure interaction (RSI) analysis and vehicle-track-structure-interaction (VTSI) analysis are often required during bridge design. For example, the California High-Speed Train Project requires RSI analysis for final design of all structures, as well as VTSI analysis, with the level of interaction to be modeled determined by the complexity of a structure. The goal of RSI analysis is to ensure that superstructure deformations and rail stresses are within acceptable limits. VTSI analysis is a dynamic analysis that takes into account influence of actual trainsets. VTSI Level 1 analysis includes train loads as a series of moving loads. This analysis allows evaluation of dynamic impact effects from trainsets and vertical accelerations of the deck. For complex high-speed railway bridges, VTSI Level 2 might be required, accounting for full dynamic interaction between the trainset and the bridge. To represent this interaction, the trainset is modeled as a multibody system consisting of rigid bodies, springs, and dashpots. The interaction between wheels and rails is accounted for through kinematic constraints and Lagrange multipliers. This paper presents modeling, RSI, and VTSI analyses of a railway bridge in the LARSA 4D software package. The track and superstructure are modeled in an expedited way using a macro that generates the track, approach, and bridge geometries. Fasteners are modeled as hysteretic springs and automatically positioned along the curved geometry of the track using a LARSA 4D’s bridge path coordinate system definition. RSI analysis is performed accounting for temperature differentials between rails and the deck, vertical train loads, acceleration and braking forces. Break in the rail is introduced using stage construction analysis, followed by progressive collapse analysis (with adapting increments and arc-length control) or nonlinear dynamic analysis. Finally, VTSI Level 1 and 2 analyses are performed and the results are compared. Car body accelerations are compared to limit values to ensure passenger comfort.

Effect of rail cant on stress distribution

The rail cant is an important geometry parameter and is commonly monitored to ensure railway safety and comfort conditions. Understanding the influence of cant variation on the performance of railway components is extremely important to define the tolerance limits of the track and adequacy of maintenance plans. There are numerous rail cant patterns on railways, 1:40, 1:30, 1:20. However, the optimal rail cant to reduce the stress and wear of rail head not been extensively studied. This work performs an analysis of the effect of the rail cant on the rail head stress distribution. To investigate stress and strain in rail head, a Finite Element Model with Ansys software was used. For the analysis was considered a 136RE rail, axle load of 32 ton and AAR-1B wheel profile. The rail cant was varied in 0, 1:20 and 1:40. The results show that the stress in rail and wheel increases with the rail cant. The maximum stress occurred in the condition with rail cant of 1:20. The variation of cant from 0 to 1:20 results in a decrease of approximately 9% in maximum stress, ranging from 947 MPa to 867 MPa. The wheel/rail contact in cant zero condition occurred close to the transition of the wheel tread and the beginning of flange root, resulting in a dynamic instability in the wheelset. In addition to higher contact stress, increases the propensity for the hutting phenomenon, which can accelerate rail and wheel wear

Мокрій Т. Ф., Малишева І. Ю. , Лапіна Л. Г., Пасічник С. С. Взаємодія з рейками коліс пасажирського вагона з новим профілем ободу ІТМ-73EP в криволі-нійних ділянках колії

Speeding up the integration of Ukraine into the European railway transportation is an important task in the current development of the Ukrainian railway transport. Currently, the most effective way to travel across borders between countries with different track gauges is the use of gauge-changeable wheelsets. Continuous traffic on the Ukrainian (1520 mm gauge) and European (1435 mm gauge) railways calls not only for gauge changing facilities, but also for the compatibility of the wheel-rail contact pair on both railways: R65 rails and a cant of 1/20 in Ukraine and UIC60 rails and a cant of 1/40 in Europe. At the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, a new wear-resistant wheel profile, ITM-73ER, was proposed. As predicted, its use in passenger cars will offer dynamic stability and a high dynamic performance throughout the range of operating speeds on the Ukrainian and European railways and acceptable indices of wheel – unworn rail interaction on both railways. In service, the shapes of the wheel and rail contact surfaces change due to wear, especially in curves. Because the Ukrainian and European railways mostly use wheel and rail profiles of their own, the use of the new wheel profile may impair the wheel–rail interaction process, enhance wheel flange wear, and shorten the wheel life. The goal of this work is to study the effect of the in-service rail head shape change in curves of the Ukrainian and European railways on the wheel–rail interaction indices of a passenger car with ITM-73ER profile wheels. The head shapes of outer rails of the Ukrainian and European railways’ circular curves were predicted for a side flange wear changing from 0 to 8 mm in 2 mm increments. The calculations were made for two circular curves of radius 300 m with UIC60 rails and a cant of 1/40 (Europe) and R65 rails and a cant of 1/20 (Ukraine). To speed up the prediction, it was assumed that the curves were traveled by four-axle fully loaded freight cars, which maximizes the rail wear. The freight car wheels were assumed to be unworn and machined to the S1002 profile (for the European railways) and to the standard profile specified by the Ukrainian State Standard GOST 10791:2016 (for the Ukrainian railways). Using the computed head shapes of R65 and UIC60 rails differing in wear degree, a study was conducted into their effect on the wheel–rail pair strain and stress field and the dynamic indices of car–track interaction for passenger cars with ITM73-ER profile wheels negotiating a circular curve of radius 300 m. It was shown that the use of the ITM-73ER wheel profile in passenger cars will offer improved indices of car–track interaction, for worn rails too, both on the Ukrainian railways and in the combined operation on the Ukrainian and European railways.

Research on non-destructive testing of stress in ferromagnetic components based on metal magnetic memory and the Barkhausen effect

In this paper, the relationship between the effective field of metal magnetic memory (MMM) emission and the structural stress of the ferromagnetic components is studied. The relationship between the voltage of the received magnetic Barkhausen noise (MBN) and the excitation source is also studied. Moreover, the characteristics of the emission spectrum of the MMM and MBN detection signals, and the influences of the lift-off distance on the stress detection accuracy of the two detection methods are studied. The advantages and disadvantages of the two magnetic non-destructive testing (NDT) techniques are analyzed separately, and their functions are combined to enhance the advantages and weaken the disadvantages. Modern signal analysis methods such as wavelet packet transform and signal feature extraction are introduced to process MMM signals, and a classifier for stress grading is established in combination with machine learning methods. On this basis, graded detection of the temperature stress of the continuous welded rail (CWR) was carried out. The detection accuracies of the 30–50 MPa, 50–70 MPa and 70–90 MPa stress grade ranges of CWR reach 71.43%, 82.76% and 75.00% respectively. The rapid grading detection of the temperature stress of the CWR and the rapid judgment of the structural stability of the CWR are realized based on the MBN-MMM detection technique.

A review of non-destructive evaluation techniques for axial thermal stress and neutral temperature measurement in rail: Physical phenomena and performance assessment

Thermal buckling of continuous welded rail (CWR) has been a long-standing challenge for the railroad industry because of the high derailment rate and the associated social, economic, and environmental impacts it causes. Rail buckling is generally attributed to excessive thermally-induced axial compressive stress developed in the rail from high temperatures. Knowing the rail thermal stress or its rail neutral temperature (RNT) is critical for safe and efficient rail system operation. There has been great interest and much work on the development of nondestructive evaluation (NDE) techniques to estimate rail thermal stress and RNT in situ. This paper reviews the findings and conclusions from research about NDE approaches for estimating rail thermal stress or RNT, emphasizing the physical phenomena and performance interpretation related to each of the approaches. We identify the type of reference measurements each technique relies on and tabulate this information showing key assumptions, performance, and limitations for each technique.

Rail Structure Interaction Analysis for Providing CWR on Un-Ballasted Multi-Span Open Web Steel Girder Bridge

Rail structure interaction (RSI) requires thorough study to understand the force transfer mechanism between the track and bridge components due to train vertical live loads, braking/traction loads and thermal loads accordingly. RSI analysis gives us an outline of the axial stress in rail, support reactions transferred to the bridge components and the relative displacement caused between the track and bridge. This paper investigates rail structure interaction analysis of unballasted multi-span steel through girder railway bridge carrying dedicated freight corridor (DFC) of 32.5t axle load. For this purpose, RSI analysis is performed as per the guidelines given in UIC774-3R [7] Code of Practice (International Union of Railways) for two different multi-span bridge with a span configuration of 7x63m and 6x48m respectively and the axial stress in rail, relative displacement between rail and bridge and support reactions transferred to the bridge components are calculated based on the span and stiffnesses of the bridges. From the analysis results, it shall be concluded whether to explore the possibility of providing a provision of continuous welded rail (CWR) on the bridge or to adopt switch expansion joints (SEJ) or other expansion devices accordingly.

Combining welding-induced residual stress with thermal and mechanical stress in continuous welded rail

Continuously welded rail (CWR) with flash-butt welded joints has become standard practice for railway construction around the world. The welding process during rail installation or repair forms a residual stress field in the weldment altering locally the distribution and amplitude of the total stress that develops when the rail is in service. This paper presents a computer simulation approach to study the combined residual, thermal, and mechanical stress caused by the fastener system that develops in rail during the in-track welding and installation. The proposed approach simulates within a Finite Element Analysis framework the rail welding and installation sequence using detailed thermal and mechanical models of the weldment formation, and in-track installation. The model is validated with experimental measurements reported in the literature. It is implemented in a study that demonstrates the combined effects of such stresses with stress that develops in the rail during a daily solar-induced thermal cycle. A non-trivial stress gradient is observed where the mean tensile stress in the weldment is elevated relative to the rail at large. The higher mean stress warrants further investigations in view of fatigue performance under wheel loading. The proposed computer simulation approach is a tool that will enable future investigations focusing on more detailed examinations of weldment behavior, particularly concerning fatigue failures and track configurations, as well as in optimizing welding parameters to control the development of residual stresses.