Rail Section Research Articles

Assessing Energy Consumption of High-speed Trains based on Mechanical Energy

Normally, not all the stopping sections of a high-speed rail (HSR) are long enough for a train to achieve the initially fixed target speed. By taking this crucial attribution of HSR into consideration, an assessment model for energy consumption of a high-speed train (HST) is established based on its mechanical energy. An example based on real data in China effectively demonstrates the model. It is found that both the target speed and stopping frequency have significant effects on HST energy consumption. If the target speed rises from 200 to 350km/h, the increasing percentages of energy consumption are 133%, 140%, 149% and 153% respectively for HSTs of the four examined stop schedules: all-stop, skip-stop, large-stop and non-stop. The non-stop HST consumes the less energy whereas all-stop HST consumes the most under equivalent conditions. Moreover, the travel speed of an HST with high target speed and frequent stopping is not significantly higher than that of an HST with lower target speed and less frequent stopping, but the former's energy consumption is strikingly more than the latter's. The findings might help rail departments to make a more environmental-friendly HST operation scheme by integrating its target speed and stop schedule.

An analysis of the simulated acoustic emission sources with different propagation distances, types and depths for rail defect detection

Acoustic Emission (AE) technique is an effective nondestructive detecting method, and has a promising application for rail defect detection. So far, little attention has been paid to propagation distances, types, and depths of AE sources, which are important for rail defect detection accurately. This paper presents an experimental study on the simulated AE sources with different propagation distances, types and depths for rail defect detection. Three simulated AE sources with different frequencies are seeded on the cross section of rail, and the depths of AE sources are changed in the vertical direction. After receiving AE signals, wavelet transform and Rayleigh–Lamb equations are utilized to extract time–frequency features and modes. Based on the wavelet transform with corresponding group-velocity curves, the influences of different propagation distances, the features of different source types and the rules of different source depths are examined. It is concluded that the features of AE sources with different propagation distances, types and depths can be obtained by AE technique for rail defect detection. It is very useful to analyze and detect defects in rail defect detection.

Dynamic Characteristic Analysis of Irregularity under Turnout by Vehicle-Turnout Rigid-Flexible Coupling Model

Finite element model of track in frog zone is built by vehicle-turnout system dynamics. Considering variation of rail section and elastic support, bending deformation of turnout sleeper, spacer block and sharing pad effects, the track integral rigidity distribution in longitudinal direction is calculated in the model. Vehicle-turnout rigid-flexible coupling model is built by finite element method (FEM), multi-body system (MBS) dynamics and Hertz contact theory. With the regularity solution that different stiffness is applied for rubber pad under sharing pad of different turnout sleeper zone, analysis the variation of vertical acceleration of bogie and wheelset, rail vertical displacement and wheel-rail interaction force, this paper proves that setting reasonable rubber pad stiffness is an efficient method to solve rigidity irregularity problem.

Field and laboratory assessments of the friction coefficient at a railhead

The aim of this work was to prove that the oil applied to the wheel flange using on-board lubricators not only alters the friction coefficient between wheel and rail but also influences the braking and acceleration performance of trains on one of the lines of the metro in Mexico City. A series of tests were carried out in the presence of an oil lubricant, both in the laboratory and in the field, using a pendulum tester. It was observed that the oil migrated from the rail corner to the top of the rail. In another set of experiments, water was sprayed onto the lubricant on the top of the rail. The results indicated that under these conditions, the friction coefficient has a low value in rail sections where a high value of the friction coefficient is required. Tests with water/oil mixtures presented similar levels of friction to the oil-only tests. A set of tests were performed after the rail surface was cleaned and the oil lubricant and water were applied together. The laboratory and field tests showed similar behaviour trends for the friction coefficient. The pendulum method can be used to assess railhead friction on short-length sections of rail. Points are made regarding the conditioning of the pads and calibration of the pendulum arm.

Shaping the structure during rolling and isothermal annealing, and its influence on the mechanical characteristics of high-carbon steel

Rail sections made of pearlitic steels used in the construction of turnouts and railroads must have appropriate mechanical and fatigue characteristics as well as high resistance to abrasive wear. The paper discusses the influence of temperature at the end of rolling and isothermal annealing on the morphology of pearlite and the mechanical properties of steel R260. Properties of sections were evaluated in a statistic tensile and impact test, while that of the microstructure by using a scanning microscope. For a quantitative analysis of pearlite colonies, the “MET-Ilo v.3.5” computer program was used. The influence of the morphology of pearlite on the impact strength of KCU in the temperature range from −80°C to 100°C was also determined. It was demonstrated that in the above-mentioned processes the properties of the steel may be controlled within a wide range by changing the pearlite morphology parameter in the material.

Allowable Bending Fatigue Stress of Rails

Allowable bending fatigue stress is an important input for rail section design because of the nature of repeated loading on railways. The majority of rail failures have their origin in fatigue. In the American Railroad Engineering and Maintenance-of-Way Association (AREMA), there is only a fatigue test under the name of rolling load test for bonded joints; there are no fatigue tests for parent rail and welded joints. With respect to bonded joints, there is no known railroad or transit agency that uses plain bonded joints as an alternative to either flash butt weld (FBW) or alumino thermite weld (ATW) joints. A rail or weld should be able to resist at least 2 million stress cycle repetitions without developing any cracks. In this paper, allowable bending fatigue stress is formulated analytically with the nominal stress method (S-N). Marin’s six modification factors are applied to the laboratory-determined fatigue limit to account for surface conditions, size, load, temperature, reliability, and shape. Then, Goodman’s mean stress correction factor is applied to account for mean tensile stress in the rail. A brief literature review on the modification factors is included. The allowable bending fatigue stress is calculated and validated theoretically, then compared with the recommended AREMA value. Finally, the current AREMA formula and its recommended value for allowable bending fatigue stress are discussed.

Simulation Analysis on Temperature Field and Microstructure Field of 60AT Rail in Air Cooling

In this paper, the DEFORM-3D finite element software is used to construct the models of temperature and microstructure fields of the 60AT rail during the air cooling process after rolling, with the distribution regularities of temperature and phase-transformation in air cooling analyzed. The computation results suggest that the temperature distribution along the cross section of the 60AT rail is significantly influenced by its rail web with great volume-to-surface-area ratio. At 150s during the air cooling process, there is no phase change on the cross section of the 60AT rail, with all phase that appears to be austenite. At 650s with the temperature dropped, the almost all the cross section of the rail has been turned into pearlite, with the changing rate of 97.2%. The pearlite phase change happens from the three edges of the railhead and the long and short wings of the rail flange to the railhead and the rail web, until the whole cross section of the rail is changed.

Influence of Pearlite Morphology on Creeping Characteristic Curves of R260 Steel

The elements of railway turnouts made from rail sections of R260 high carbon steel must have a high resistance to abrasive and contact fatigue wear, as well as a good resistance to cracking under service loads. These mechanical properties largely determine the suitability of steel for use as railway track components. In this study, two groups of specimens were subjected to tests of mechanical properties and metallurgical analyses. The first group included material obtained from the hot-rolled block section, the rolling end temperature being Tkw = 950°C, while the second group was material after the rolling process with the subsequent 20-minute isothermal annealing at a temperature of 480°C. The microstructure of tested materials (Rm, Rp0.2, A5, Z, HB) was characterized, and their basic mechanical properties and fracture toughness in the KIc plane strain condition were determined. Also the effect of temperature, ranging from-80°C to 100°C, on the KCU impact toughness of R260 steel was established. Based on the SEM observation using the Hitachi S-3400N scanning microscope, it was found that pearlitic structure with a varied distance between cementite plates, equal to 0.29 μm and 0.09 μm, respectively, appears in the hot-rolled R260 steel and in the steel subjected to additional isothermal annealing treatment. The impact of pearlite morphology on the cracking characteristics and basic mechanical properties of materials was analyzed. It was found that at room temperature, the higher fracture toughness (KIc = 66.4 MPa·m1/2) is shown by the steel after isothermal annealing at 480°C, in which less distance between the plates of cementite has been observed in the perlite. The fracture toughness of R260 steel after hot rolling at 950°C was KIc = 48.3 MPa·m1/2. As in the case of fracture toughness, the impact strength of R260 steel after isothermal annealing was significantly greater than the impact strength of steel only after hot rolling. The determined cracking characteristics of R260 steel make it possible to determine the effect of heat treatment on the formation of microstructure and material properties, which determine the service life of rail sections.

Dynamic responses of bridge-approach embankment transition section of high-speed rail

Based on the vehicle-track coupling dynamics theory, a new spatial dynamic numerical model of vehicle-track-subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0–5 m zone behind the abutment should be specially designed. The results of the study from vehicle-track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction (K 30) is greater than 190 MPa within the 0–5 m zone behind the abutment and greater than 150 MPa in other zones.

Modeling damage mechanics of railway tracks to evolve control strategies for derailment prevention

Purpose – With an eye to prevent derailment of high-speed trains, vis-à-vis unwarranted loss of lives and property, this paper aims to develop a formalism of designing a suitable control system with embedded decision support system. Design/methodology/approach – A model of rolling contact fatigue (RCF) crack propagation in railway tracks is designed, simulating the alarming stress intensity factor around the advancing fatigue cracks. COMSOL multi-physics software is employed to design the RCF crack monitoring system with acoustic emission (AE) count signals, describing the damage threshold of railway tracks. Findings – Simulation experiment on stress intensity factor for cracks in real life rail sections has enabled to describe the maximum working stress; it has been noticed that the threshold value of stress intensity factor (∼ 41 MPa m1/2) for the onset of unstable crack propagation is reached at a fatigue crack length of 11.5 mm. It is further noticed that the observed AE count at a particular instant of time in a specific location of railway track is a true indication of the vulnerability of rail failures. Originality/value – The proposed model, a completely new of its kind, bears a high socio-technological value as it entails the design of an intelligent control system to prevent train accidents.

HEMU 430-X 주행특성을 고려한 호남고속철도 곡선궤도구조의 거동연구

The wheel-rail interaction forces are influenced by the velocity of vehicle, wheel load, alignment (curve radius, cant etc). For the safety of track structure, it is required to evaluate the influences for track and influential factors. Recently, the HEMU 430-X, which was developed by Next Generation High-Speed Rail Development R&D Project, achieved 421.4km/h in a test run of Daegu-Busan section of the Gyeongbu high speed rail on March in 2013. In the case of additional speed-up test on Test-Bed Section(Gongju-Jeongeup: KP 100~128km Osong starting point), the analysis of track forces is required for outer rail by the increase of dynamic force and centrifugal force of vehicle. In this paper, the vehicle speed variation on HSL line is evaluated by TPS analysis considering the tractive effort of HEMU 430-X, tested running resistance and alignment of Honam HSR. And the track forces are evaluated by centrifugal force and impact factor on curved track.

Railroad inspection based on ACFM employing a non-uniform B-spline approach

The stresses sustained by rails have increased in recent years due to the use of higher train speeds and heavier axle loads. For this reason surface and near-surface defects generate by Rolling Contact Fatigue (RCF) have become particularly significant as they can cause unexpected structural failure of the rail, resulting in severe derailments. The accident that took place in Hatfield, UK (2000), is an example of a derailment caused by the structural failure of a rail section due to RCF. Early detection of RCF rail defects is therefore of paramount importance to the rail industry. The performance of existing ultrasonic and magnetic flux leakage techniques in detecting rail surface-breaking defects, such as head checks and gauge corner cracking, is inadequate during high-speed inspection, while eddy current sensors suffer from lift-off effects. The results obtained through rail inspection experiments under simulated conditions using Alternating Current Field Measurement (ACFM) probes, suggest that this technique can be applied for the accurate and reliable detection of surface-breaking defects at high inspection speeds. This paper presents the B-Spline approach used for the accurate filtering the noise of the raw ACFM signal obtained during high speed tests to improve the reliability of the measurements. A non-uniform B-spline approximation is employed to calculate the exact positions and the dimensions of the defects. This method generates a smooth approximation similar to the ACFM dataset points related to the rail surface-breaking defect.

Guideway Joint Surface Properties of Heavy Machine Tools Based on the Theory of Similarity

In the process of Heavy NC machine tool design, the combination of static, dynamic characteristics directly determines and influences stiffness, damping, machining precision and work efficiency, Therefore the research on the combination of the characteristics become extremely important to the success of machine tool design. This study mainly studies the dynamic and static characteristic parameters of heavy machine tool guide way joint. And put forward a practical machine tool combining surface analysis method according to the experimental verification. How to obtain the analysis and test of the dynamic parameters to the combination is introduced. It is presented that small linear guide as a scale model based on similarity theory. And make a research on the static and dynamic characteristics of small guide joint and the conclusion extended to heavy machine set of faces. And the conclusion is extended to the heavy machine set of faces. It is introduced the spring damping unit of combined surface characteristics simulation during a small test about guide way dynamic performance analysis. Thus it can more effective simulate influence of combination of surface characteristics to components of the overall structure. The study analyze the dynamic performance of machine tool bed rail section by the verification and treat extraction of the first five modes as the analysis and forecast of the models of guide-way joint dynamic performance. The results can be used as reference data about structure and design of the machine tool due to the similarity principle and error range.

Characteristics of Current Distribution in Rails and Armature With Different Section Shape Rails

The railguns can be classified into three types by the interior surface shape of rails, which are the type of plane-rail, convex-rail, and concave-rail. In this paper, the characteristics of current distribution in rails and armature are analyzed and compared for those three types, during the rising, dropping, and the flat part of the exciting current source. This current distribution is simulated by the finite element software ANSYS. The convex-rail type gun is of the weakest opposite direction current phenomenon, and its current distribution on the rail section is the most even. The evenness of the current distribution can be adjusted by changing the height of the convex part. The current density at the corner of armature is very large in the plane-rail and the concave-rail types, which results in stress concentration and probably damage of armature or rail surfaces.

Multi-point contact of the high-speed vehicle-turnout system dynamics

The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.

Motion deviation rectifying method of dynamically measuring rail wear based on multi-line structured-light vision

Rail wear dynamic measurement techniques are important to ensure the security of railway system and the efficiency of maintaining. Nowadays, a widely used approach is based on structured-light vision sensor, which includes a camera and a laser projector generating a light plane on the inner side of the rail. Considering the sensor installation error and vibration of running train, it is difficult to ensure the perpendicularity between the light plane and the rail, which leads to large measurement error. In order to overcome the problem, a motion deviation rectifying method is proposed. Rail section profiles are obtained by a multi-line structured-light vision sensor with multiple parallel light planes. Each profile can be segmented into two curves. One representing the rail waist is used to fit the rail longitudinal axis (parallel to train running direction) and establish an auxiliary plane perpendicular to the direction. Deviation rectifying process is to project the rail section profiles onto the auxiliary plane to recover perpendicularity between the light plane and the rail. Then another curve representing the rail head is used to calculate the rail wear based on the standard profile. The experimental results indicate that the method reduces the rail wear measurement error, meeting the requirements for real-time dynamic measurement of rail wear.

Effect of Bolt Hole Residual Stresses on Fatigue Performance of Truck Frame Rail Structures

The large numbers of bolt holes cut into truck frame side members act as joineries and points of attachments for various sub systems of the truck. While these bolt holes are unavoidable due to their primary functional importance, the near hole residual stress resulting from the type of hole cutting operation plays a significant role in deciding the fatigue performance of frame rail structures. If the residual stress is tensile in nature, this along with the surface roughness at the hole surface can lead to early initiation of fatigue cracks around bolt hole surface. In order to assess the extent of plastic deformation and resulting residual stresses in near hole areas of frame bolt holes cut using drilling, punching, laser cutting and water jet cutting processes, experimental investigation was carried out through microstructure analysis and X-ray diffraction measurements. Apart from this, an assessment of shot-peened hole surface was taken up to understand the effect of shot-peening on fatigue behavior of frame rail section with bolt holes. Also the test specimens extracted from frame rail sections were tested for comparing the fatigue life of specimens having bolt holes cut using different hole cutting operations.

115 レール継目部における衝撃音に係わる振動・音響特性評価(鉄道車両の騒音)

Impact noise occurs when a train passes through the section of discontinuous rail. It is one of the sources of the environmental problem of railway traffic. Therefore, the characteristics of impact noise have been investigated using the measurement results obtained both static test and running test. In this paper, an attempt is made to evaluate the vibration properties of the rail and wayside noise at two rail joints. The result shows that the frequency characteristics of the rail vibration and wayside noise at each rail joint are different. One reason is that the wheel/rail contact force is different from each other. Furthermore, the relationship between the wheel/rail contact force and the displacement of the wheel axle which is derived from a profile shape of jointed rails is investigated.

Use of Recycled Tire Rubber to Modify Track–Substructure Interaction

Resiliently bound ballast (RBB) is a new engineered material being developed as an alternative or supplement to conventional ballast for use in transit, passenger, and freight railways to improve mechanical behavior and control the modulus and damping when recycled tire waste material is used. RBB is a stable mixture of standard ballast stone and tire-derived aggregate (TDA) bound together with a purpose-designed resilient epoxy binder. Initial laboratory tests were conducted on specimens 6 in. (151 mm) and 10 in. (254 mm) in diameter of two mixes of RBB. Tests were conducted on fully bound (cemented) samples of ballast, TDA, and epoxy as well as individual particles with TDA bound to the individual ballast particles with the resilient epoxy binder. The tests included static triaxial compression tests and dynamic cyclic triaxial tests. Static tests indicated that the addition of the TDA and epoxy resulted in an increase in cohesive strength. The dynamic tests indicated changes in modulus and damping depending on the mixture of rock, TDA, and epoxy. One proposed use of RBB is to affix the RBB to the bottom of concrete ties to modify the interaction between the tie and the ballast material and improve ballast durability and modify resilience and damping. Box tests were conducted on a section of concrete tie with and without RBB attached. The tie with a section of rail attached was vertically loaded with a sinusoidal load to model repetitive axle loading. Observations indicated that the box test that used a concrete tie without RBB produced more ballast breakage compared with the test that used a concrete tie with RBB; however, more abrasion between particles occurred with the RBB-bound tie.

Forensic Engineering Investigation Of Sectional Ladder Treestand Failures

The Purpose Of This Forensic Engineering Investigation Was To Determine The Root-Cause Of Failure Of Three 15-Foot Sectional Ladder Treestands That Caused Injury To Users. All Three Treestands Were Identical In Design And Manufactured By The Same Company Despite Differences In Trade Names. Within A Reason-Able Degree Of Scientific And Engineering Certainty, It Was Concluded That Failure Of The Treestands Was The Result Of Overstressing The Star-Crimped Area Of The Treestands At Adjoining Ladder Sections. Overstressing Was Caused By A Designed Reduction In Section Modulus Of The Rail At Adjoining Ladder Sections. Further, The Load-Bearing Ability Of The Ladder Treestands Was Evaluated In Accordance With Com-Monly Accepted Engineering Principles For Metal Ladder Design (Ansi A14.2-2007). Analysis Revealed That The Structural Strength Of The Rail Section And Testing Standards For The Treestand Industry Are Lack-Ing When Compared To Portable Metal Ladders Designed For Identical Load Ratings. In Fact, The Treestands Failed To Meet The Standard Requirement For A Portable Metal Ladder Rated At 170-Pounds Even When The Treestand Was Tested At ½ Of Its Spanning Length (2-Sections). Comparisons Between The Treestands And Portable Metal Ladder Standards Indicated That The Treestands Failed To Meet Minimum And Generally Accepted Standards For Ladder Design And Suggested The Treestands Do Not Meet Minimum Requirements For Merchantability.