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The improvement in component service life and railway service reliability has been viewed from an environmental perspective. Delays and train accidents carry enormous costs and greenhouse gas (GHG) emissions potential due to the increased fuel burn and the need to replace heavy equipment prematurely. The use of higher-performance materials, more efficient vehicle design, and modern technology by Canadian railways to reduce service interruptions are presented. Their resulting cost savings not only can provide financial incentives for the continuous optimization of asset utilization but can also lead to significant contributions to the decarbonization of the railway industry. The authors have estimated a total reduction of 2.4 kt-CO2e per year in embodies carbon emissions due to life extensions of wheelsets compared to 2017 levels on a Class 1 railway. System-wide, the rail life extension has resulted in a saving of 8.1 kt-CO2e per year compared to 2017 for the same railway. Compared to 2004, the Canadian railway industry has achieved an annual reduction in embodied carbon emission of 6.7 Mt-CO2e from the reduction in mainline derailments. [ABSTRACT FROM AUTHOR]

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Mixed freight trains have more diversified vehicle characteristics and train combination modes than unified freight trains, so it is more difficult for mixed freight trains to predict the accident caused by longitudinal impulse. At present, train dynamics theories and numerical simulation methods have been increasingly used to reduce longitudinal train impulse and decrease freight wagon instability. According to these research experiences, this paper focuses on the marshalling modes of mixed freight trains and their effects on the longitudinal in-rain forces. For this purpose, an advanced simulation model for mixed freight trains was developed and several typical mixed marshalling modes were designed and simulated. The results indicate that, for the mixed train including empty and loaded wagons, empty wagons should be arranged at the tail of the train and should avoid being marshalled together. For the mixed train including marshalled wagons with various actual live loads or nominal axle loads, heavier wagons should be centrally arranged in the front part of the train, and meanwhile marshalled wagons should avoid being sorted by weight in the concave and ascending distribution mode. For the mixed train including marshalled wagons with various body types, container flat wagons and oil tank wagons should be arranged as much as possible in the front of the other wagons. [ABSTRACT FROM AUTHOR]

A train–tunnel–surrounding rock numerical model was established by using ABAQUS to analyze the dynamic response of a heavy-haul railway tunnel in hard rock, quantify the influence of the train axle load on the tunnel dynamic response and determine its potential vulnerable position. The results suggested that: Under the 30 t train load and surrounding rock pressure coupling, the maximum principal stress caused by rock pressure was 1.27 MPa, located at the bottom of the structure below the side drain; the maximum dynamic response of the tunnel structure and base rock was located directly below the rail. The lower part of the side drain and rail was the vulnerable position in the tunnel bottom structure, and the probability of base disease under the rail may be higher than that in soft-rock tunnels, for it has a greater dynamic response and thinner structure compared to a soft-rock tunnel. The maximum principal stress amplitude of the tunnel structure and base rock were 129.3 kPa and 43.0 kPa, respectively. When the axle load increased by 1 t, the dynamic amplitude of the structure's maximum principal stress increased by about 4.14 kPa, and the base rock's maximum principal stress increased by about 1.33 kPa. The rock pressure was not negligible in the dynamic analysis of the railway tunnel, and the dynamic response of the tunnel bottom structure and base rock will decrease, obviously, when the rock pressure is ignored. [ABSTRACT FROM AUTHOR]

This article focused on the microstructure characterization and residual stress measurements of the flange from classes D and C railway wheels (called 7D and 7C steel, respectively) to contribute with the residual stress level on new forged wheels flange area. A correlation with the hardness was conducted. The residual stress was measured in three points of the flange using the x-ray diffraction technique, and the microstructure characterization on SEM microscopy. We found the 7C steel has fine pearlite and ferrite microstructures, and 7D steel has degenerated pearlite and bainite microstructures. In the 7D steel, the compressive residual stress in the flange region was higher than in the 7C steel, which is related to the presence of bainite on the microstructure. There was a correlation between the hardness and residual stress value. The knowledge of the residual compression stress level is important for safety train wheels operation. The traction stress generated by the brake system on the wheel is attenuated by residual compression stress. [ABSTRACT FROM AUTHOR]

The Haoji railway in China is the longest heavy haul railway in the world, including 235 tunnels located along the 1837 km railway. With the increasing axle load of the new line and the basal deterioration of the existing heavy haul railway in China, studying the fatigue performance of the newly designed tunnel structure is essential. To study the coupling effect of the surrounding rock pressure and 30 t axle load train, in this study, we combined three-dimensional numerical simulation and three-point bending fatigue tests to investigate the fatigue performance of the basal structures. The results of numerical simulation indicate that the center of the inverted arch secondary lining is the position vulnerable to fatigue in the lower tunnel structures; the surrounding rock pressure performance exerts a stronger influence on the stress state of the vulnerable position than the dynamic train loads. The S–N formula obtained from the experiment showed that the fatigue life of tunnel bottom structures decreases with increasing surrounding rock pressure and dynamic load. In typical grade V surrounding rock and 30 t axle loads, fatigue failure will not occur in the newly designed tunnel bottom structures within 100 years if bedrock defects are lacking and pressure of surrounding rock is not excessive. [ABSTRACT FROM AUTHOR]

In this article, a wheel life prediction model considering wear and rolling contact fatigue (RCF) is developed and applied to a heavyhaul locomotive. For wear calculations, a methodology based on Archard's wear calculation theory is used. The simulated wear depth is compared with profile measurements within 100,000 km. For RCF, a shakedown-based theory is applied locally, using the FaStrip algorithm to estimate the tangential stresses instead of FASTSIM. The differences between the two algorithms on damage prediction models are studied. The running distance between the two reprofiling due to RCF is estimated based on a Wöhler-like relationship developed from laboratory test results from the literature and the Palmgren-Miner rule. The simulated crack locations and their angles are compared with a five-year field study. Calculations to study the effects of electro-dynamic braking, track gauge, harder wheel material and the increase of axle load on the wheel life are also carried out. [ABSTRACT FROM AUTHOR]

The main task for heavy haul railway operators is to reduce the cost of exported minerals and enhance the long-term viability of rail transport operations through increasing productivity by running longer and heavier trains. The common opinion is that this is achievable by means of implementation of high adhesion locomotives with advanced AC traction technologies. Modern AC high adhesion locomotives are very complex mechatronic systems and can be designed with two alternative traction topologies of either bogie or individual axle controls. This paper describes a modelling approach for these two types of AC traction systems with the application of an advanced co-simulation methodology, where an electrical system and a traction algorithm are modelled in Matlab/Simulink, and a mechanical system is modelled in a multibody software package. Although the paper concentrates on the analysis of the functioning for these two types of traction control systems, the choice of reference slip values also has an influence on the performance of both systems. All these design variations and issues have been simulated for various adhesion conditions at the wheel–rail interface and their influence on the high traction performance of a locomotive equipped with two three-axle bogies has been discussed. [ABSTRACT FROM PUBLISHER]

Copyright of Transport Problems: an International Scientific Journal is the property of Silesian University of Technology, Faculty of Transport and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose – This paper aims to present the theoretical and experimental investigation of the temperature of high speed and heavy haul tilting pad journal bearing. Design/methodology/approach – The bearing is 152.15 mm in diameter with three slenderness ratios (L/D) and three clearance ratios. The equations that govern the flow and energy transport are solved by the finite difference method, and the experimental tests are conducted in a test rig of high speed and heavy haul tilting pad journal bearing. The shaft speed ranges from 3,000 to 16,500 r/min (the highest linear-velocity equals 131.4 m/s), and the three static loads are 10, 20 and 30 KN. Findings – The comparisons between numerical results and experimental results show better correlations. It is shown in the theoretical and experimental results that the temperature increases with static load and shaft speed and decreases with clearance ratio and L/D. Originality/value – The theoretical models presented in this paper can be used to predict the temperature of tilting pad journal bearing when the shaft’s linear velocity is up to 130 m/s. [ABSTRACT FROM AUTHOR]

In order to alleviate the wear of heavy-haul wheel/rail materials, the wear experiments of wheel/rail rollers undergoing laser quenching were carried out using rolling-sliding testing apparatus. The results indicate that laser quenching produces a hard martensite layer with a certain depth. The improvement of wear resistance of materials resulting from laser quenching markedly decreases the wear volume of wheel/rail rollers. The maximal decrease rate of wear volume of wheel and rail materials is about 92.9% and 89.5%, respectively. Furthermore, the worn surfaces of wheel/rail rollers present different surface morphology and damage mechanisms due to difference of hardness matching. When the surface hardness of wheel/rail rollers undergoing laser quenching is high, the spalling damage and adhesion wear are dominating. When a single wheel or rail roller undergoes laser quenching, the damage mechanism of wheel and rail rollers are significantly different. According to the severe wear region of the heavy-haul wheel/rail, it is proposed that the rail side and wheel flange may undergo laser quenching treatment for alleviating wear of heavy-haul wheel/rail materials. However, further work should be carried out for clarifying the fatigue characteristic of wheel/rail with laser quenching. [ABSTRACT FROM PUBLISHER]

This paper presents an analysis of the influence of materials that can be present in the so-called “third-body layer” at the wheel/rail interface on curving forces generated in heavy haul operating conditions. The third-body layer is the interfacial layer whose shear properties determine the bulk frictional characteristics that emerge in wheel/rail contact. It is often postulated that precipitation (rain) provides an effective form of lubrication at the wheel tread/rail head interface, reducing curving forces and corresponding wear. The postulate is explored through the analysis of lateral and vertical force data collected under a wide range of environmental conditions in full-scale revenue service. The effects of precipitation are rigorously explored and compared with the effects of top of rail friction modifiers, which are intentionally introduced into the third-body layer.This paper originated from the 2011 IHHA Conference. [ABSTRACT FROM AUTHOR]

Shuohuang Railway (SHR) is one of the major coal carriers in China, with a total network length of 590 km running from Shenchi to Huanghua. Significant increases in annual operating tonnage have generated accelerated rail wear and rolling contact fatigue (RCF) growth problems for many sharper/lower radius curves. In order to address these rail problems, SHR is interested in the state-of-the-art total friction management (TFM) technology currently deployed by some North American heavy haul freight railroads and is evaluating the impact of TFM via a field trial at SHR’s Yuanping subdivision. This paper presents an evaluation of the effect of TFM, which includes both wayside gauge face lubrication and wayside application of a thin film top of rail friction modifier on control of lateral forces, rail wear and RCF. [ABSTRACT FROM AUTHOR]

A finite element model for the process of a wheel passing a crossing is presented. In the dynamic model, one wheel, the wing rails and the crossing nose (frog) are modelled. The bogie, the complete wheel set and the support of the crossing are represented as a system consisting of masses, springs, dampers and friction-generating elements. The rolling/sliding behaviour between the wheel and crossing is studied using the proposed model. Due to the conical shape of the wheel tread and multiple contacts between the wheel and the crossing parts, sliding occurs during the transition of the wheel from the wing rail to the crossing nose or vice versa. At the same time, an impact occurs that produces high contact forces. The parameters of the model are the train speed and passing direction, the wheel and the crossing geometry, the axle load and the support of the crossing. In this paper, the crossover process is studied for high axle loads and compared with results of simulations using a normal axle load. Further parameters are three train velocities, both directions of passing and different crossing materials. The loading of the crossing nose is calculated for all cases (axle load, train speed and direction) and materials. [ABSTRACT FROM AUTHOR]

Rolling contact fatigue on any railway system has a significant impact on the safety and efficiency of the operation. This is especially true for heavy haul railways where higher axle loads and demands for higher throughput have, over the years, challenged the limits within the wheel/rail interface. The objective of this paper is to present a methodology to manage this stress state using a detailed wheel/rail contact stress analysis. Based on the results of recent wheel profile and rail profile surveys, a kinematic wheel/rail contact analysis is performed to identify and eliminate profiles that cause high stresses. The results show that the current hollow wear criterion is effective, but that an alternative or additional criterion based on the gauge side false flange gradient or the calculated peak contact stress values can further reduce the stress state. Within the wheel and rail profile combinations investigated, the contact stresses were largely independent of the transverse profile of the high rail. [ABSTRACT FROM AUTHOR]

Rolling contact fatigue on any railway system has a significant impact on the safety and efficiency of the operation. This is especially true for heavy haul railways where higher axle loads and demands for higher throughput have, over the years, challenged the limits within the wheel/rail interface. The objective of this paper is to present a methodology to manage this stress state using a detailed wheel/rail contact stress analysis. Based on the results of recent wheel profile and rail profile surveys, a kinematic wheel/rail contact analysis is performed to identify and eliminate profiles that cause high stresses. The results show that the current hollow wear criterion is effective, but that an alternative or additional criterion based on the gauge side false flange gradient or the calculated peak contact stress values can further reduce the stress state. Within the wheel and rail profile combinations investigated, the contact stresses were largely independent of the transverse profile of the high rail. [ABSTRACT FROM AUTHOR]

Life cycle cost (LCC) considerations are of increasing importance for all organizations making long-term investments. Developments for heavy haul applications were carried out in close cooperation with users identifying the key technical requirements and the overall cost situation.The design and material specifications of the components within a turnout have to be of the highest level with regards to axle load, dynamic forces, and accelerations to meet the demands for heavy haul.Aside from the price of a product, the supply-chain, installation, and maintenance costs coupled with the total life expectancy all have a significant impact on the LCC.Key influencing factors are: (a) initial track quality, (b) delivery logistics - track closing during installation, (c) inspection intervals, (d) time to maintain in track, (e) time for replacement of rails and components, (f) life expectancy of single components.LCC optimized turnout systems are influenced by the following features: (a) minimizing forces on rails, switches, and crossings by optimizing turnout curvature and contact/transition geometries, (b) providing ideal conditions for maintenance work (e.g. through automatic tamping throughout the whole turnout without dismantling of components), (c) using low-maintenance components in order to minimize costs for inspection and maintenance and to increase availability especially in the field of switching, detecting, and locking of the turnouts. The implementation of LCC philosophy in a state-of-the-art heavy haul turnout technology will be highlighted and demonstrated with examples. [ABSTRACT FROM AUTHOR]

Based on the basic principle of thermodynamics, an elastoplastic damage constitutive model of concrete is constructed in this paper. The model is realized and verified in FLAC3D, which provides a solid foundation for the study of dynamic response and fatigue damage to the base structure of a heavy haul railway tunnel. The dynamic response and damage distribution of the base structure of a heavy-duty railway tunnel with defects were numerically simulated by the concrete elastic-plastic damage constitutive model. Then, by analyzing the response characteristics of the tunnel basement structure under different surrounding rock softening degrees, different foundation suspension range and different foundation structure damage degree are determined. The results show the following: (1) The elastoplastic damage constitutive model of concrete can well describe the stress–strain relationship of materials, especially with the simulation results of post peak softening being in good agreement with the test results, and the simulation effect of the unloading–reloading process of the cyclic loading and unloading test also meet the requirements. (2) The initial stress field and dynamic response of the tunnel basement structure under the action of train vibration load are very different from the ideal state of the structure design when the surrounding rock of the base is softened, the base is suspended, or the basement structure is damaged. With the surrounding rock softening, basement hanging, or basement structure damage developing to a certain extent, the basement structure will be damaged. (3) The horizontal dynamic stress amplitude increases with the increase in the softening degree of the basement surrounding rock. The horizontal dynamic stress of the measuring point increases with the increase in the width of the hanging out area when the hanging out area is located directly below the loading line. When the degree of damage to the basement structure is aggravated, the horizontal dynamic tensile stress of each measuring point gradually decreases. (4) The maximum principal stress increment increases with the increase in the fracture degree of the basement structure, while the minimum principal stress increment decreases with the increase in the fracture degree of the basement structure, but the variation range of the large and minimum principal stress increments is small. The research results have important theoretical and practical significance for further analysis of the damage mechanism and control technology of the foundation structure of a heavy haul railway tunnel with defects. [ABSTRACT FROM AUTHOR]