Dynamic Vertical Force Research Articles

Vertical and Lateral Dynamics of 4L Freight Bogie

Freight wagons in Europe have used Y25 bogies since the 1960s. Although very cost-effective, Y25 suffers from intrinsic limitations due to its architecture and running behaviour. This study introduces an innovative lightweight bogie, named 4L bogie, aimed at removing those limitations as well as improving running dynamics and track friendliness. This task was particularly challenging as the high ratio between laden and tare weight (up to 5:1) forced us to use a non-conventional suspension system and an innovative architecture of frame, reducing the mass by about 15% and the yaw moment of inertia by about 30% with respect to the Y25 bogie. Maintenance issues were addressed by reducing the number of components and easing overhaul, while the new design was validated from both the structural and the running dynamics point of view, assessing its interaction with the track in terms of stability, curving behaviour and the vertical response of the 4L bogie. Stability was improved by about 20% even in empty conditions and high conicity at the wheel/rail contact. Vertical dynamic force on a straight track, evaluated according to the Ride Force Count metric, and wear behaviour on sharp and mild curves were considerably reduced, leading to an improved track friendliness of the bogie.

Результаты оценки силового воздействия тяжеловесных и длинносоставных грузовых поездов на железнодорожный путь различными методами измерений

Objective: to assess the force effect of heavy and long-component freight trains on the railway track by various measurement methods: Schlumpf, influence matrices and the two-section method (PGUPS). Methods: measurements of the assessment of the force effect of heavy and long-component freight trains on the railway track were carried out using the Schlumpf methods, influence matrices and the two-section method (PGUPS). Results: it was found that measurements of vertical dynamic forces by three methods are well correlated with each other, and the Schlumpf method gives overestimated results when measuring horizontal transverse force. Practical importance: the two-section method can be recommended for measuring the force effect of both new and upgraded rolling stock on the railway track, as well as for operated rolling stock in order to identify defects and deviations on the rolling surface of the wheels

Forces on a singing wineglass rim

The characterization of friction is a multiscale problem involving a balance between asperity contacts and fluid film forces, most commonly modeled with a velocity-dependent coefficient of friction. Periodic stick–slip phenomena are often associated with the friction force that causes mechanical vibration. This type of vibration can cause noise to radiate via structural modes of a system. Notable examples include journal bearings, brake squeal, turkey calls, and wineglasses. Singing wineglasses have been used for centuries as musical instruments, so musical acousticians have studied the structural vibrations and acoustic output. However, the tri-axial force applied to the rim has not been measured. A test rig was designed to measure the vertical, tangential, and radial dynamic forces applied to the spinning glass rim and simultaneously capture the radiated noise. The sound radiated from the wineglass was observed to depend on the relative velocity at the rim and applied vertical load, so a stability region for a clear sound was determined. Additionally, the strongest radiating modes and harmonics in the pressure were found in the concurrently measured nonlinear force. This work may be extended to confirm the force measurement by existing friction models, a water medium, and more complicated systems.

On the dynamic stability of tunnel roof in nonuniform rock/soils characterized by nonlinear Mohr envelope

This study proposes a pseudo-static procedure for investigating roof stability of deep-buried tunnels in non-uniform rock/soil surrounds, on the basis of a generalized nonlinear Mohr envelope and upper bound theorem. Non-uniformity of rock/soil surrounds is discretized to certain layers characterized by differing rock/soil properties. An effective collapse mechanism is constructed, satisfying an associated flow rule and the generalized Mohr envelope. After having computed the internal and external rates of work, the upper bound formulations including collapse profile, collapse height and width are derived based on work rate balance equation. FE modelling is simulated to verify the analytical solutions with and without considerations of vertical dynamic forces. Effects of corresponding parameters representing rock/soil properties and external forces are investigated to demonstrate the implication on tunnel roof stability, aiding to provide reference for design and engineering practice.

Динамические силы воздействия колеса на рельс при безбалластной конструкции пути RHEDA 2000

Purpose: Experimental determination of vertical dynamic forces of wheel impact on a rail at ballastless construction of railway track RHEDA2000 upper structure with subsequent analysis of obtained data; definition of main factors affecting vertical dynamic force value; identification of dependence of change in the value of wheel vertical dynamic force impact on a rail from motion speed and rolling stock type; calculation of coefficients of vertical dynamics at ballastless construction of rail upper structure. Methods: Measurement of wheel vertical dynamic force impact on a rail was carried out by strain-gauge method (Schlumpf method). Numerical values of those, obtained in the course of experiment, were processed by mathematical statistics method, in its turn, probability level was taken equal to 0.994. Results: The values of vertical dynamic forces of wheel impact on a rail for ballastless structure of RHEDA2000 type at rolling stock different types and various ranges of motion speed have been determined. The dependence of change in the value of wheel vertical dynamic force impact on a rail from motion speed and rolling stock type has been graphically built. Comparison of vertical dynamics coefficients of ballastless construction of railway RHEDA2000 upper structure with the construction of a track on a ballast has been carried out. Practical significance: The obtained results can be used in projection, construction, reconstruction and repair of railway track where track ballastless upper composition is provided.

Determination of state of avalanche protection gallery during seismic impact and avalanches

The article considers the definitions of the state of the avalanche protection gallery under seismic impact and avalanches. Determined emerging horizontal and vertical vibrations of the entire structure. A calculation scheme was developed to study the dynamics of loose bodies. The scheme of vibrations of a reinforced concrete gallery with an arch covering with backfill soil during a possible earthquake in the OYZ plane is considered. The main type of vibration is lateral, vertical dynamic forces in the ground backfill. The dependence of horizontal forces on the snow layer, the dependence of the force Fr on the gallery on the speed of avalanche movement, the dependence of the force Fr on the unevenness of the backfill soil, and the change in the frequency characteristics of the gallery on the speed of avalanche movement were determined.

Application of VTB in NPD - Suspension System in Quad Bike

The development of a suspension system is a complex process that requires extensive testing and evaluation to ensure safety and performance. This technical paper focuses on the product development of a suspension system and the use of a test bench to evaluate its performance. The suspension system is an essential component of any vehicle, providing stability, handling, and ride comfort. The paper outlines the design process, including material selection and component placement, and explains the importance of simulation tools in the design phase. The test bench is used to simulate various road conditions and assess the suspension system's performance under different loads and driving conditions. The paper discusses the parameters that are measured during testing, including vertical acceleration, wheel displacement, and dynamic forces. The results of the test bench analysis are used to optimize the design and identify areas for improvement. The paper concludes with a discussion of the benefits of using a test bench in the suspension system development process. It highlights the importance of accurate and reliable testing to ensure that the final product meets safety and performance standards. Overall, this technical paper provides valuable insights into the development and testing of suspension systems, which can be applied to other automotive products.

Polygonal Wear Mechanism of High-Speed Train Wheels Based on Lateral Friction Self-Excited Vibration

This work details research on the formation mechanism of wheel polygonalization in high-speed trains and its effect factors by numerical modeling in order to prevent the increasingly prevalent problem of wheel polygonal wear. The lateral self-excited vibration model of a wheel was developed using the LuGre friction model and self-excited vibration theory. The properties of wheel self-excited vibration and the crucial condition of Hopf bifurcation were investigated; the process of wheel polygonal wear was simulated and the results were validated using field tracking data. The results demonstrated that periodic self-excited vibration generated by Hopf bifurcation is a required condition for polygonal wheel attrition at a given speed. The wheel’s polygonal wear has the following characteristics: “Constant speed—Self-excited—Fixed frequency—Divisible.” The order of the polygon is determined by the ratio of the wheel lateral self-excited vibration frequency to its rotational frequency. Wheel polygonal wear was caused by the vertical dynamic force of the wheel rail. The findings of the study can serve as a theoretical foundation for the prediction and reduction of wheel polygonal wear.

Development and Validation of a Weigh-in-Motion Methodology for Railway Tracks.

In railways, weigh-in-motion (WIM) systems are composed of a series of sensors designed to capture and record the dynamic vertical forces applied by the passing train over the rail. From these forces, with specific algorithms, it is possible to estimate axle weights, wagon weights, the total train weight, vehicle speed, etc. Infrastructure managers have a particular interest in identifying these parameters for comparing real weights with permissible limits to warn when the train is overloaded. WIM is also particularly important for controlling non-uniform axle loads since it may damage the infrastructure and increase the risk of derailment. Hence, the real-time assessment of the axle loads of railway vehicles is of great interest for the protection of railways, planning track maintenance actions and for safety during the train operation. Although weigh-in-motion systems are used for the purpose of assessing the static loads enforced by the train onto the infrastructure, the present study proposes a new approach to deal with the issue. In this paper, a WIM algorithm developed for ballasted tracks is proposed and validated with synthetic data from trains that run in the Portuguese railway network. The proposed methodology to estimate the wheel static load is successfully accomplished, as the load falls within the confidence interval. This study constitutes a step forward in the development of WIM systems capable of estimating the weight of the train in motion. From the results, the algorithm is validated, demonstrating its potential for real-world application.

ПРОЦЕДУРА ТА АЛГОРИТМ ВИЗНАЧЕННЯ КОЕФІЦІЄНТА ЗАПАСУ МІЦНОСТІ ВАНТАЖНОГО ВАГОНА З УРАХУВАННЯМ СУЧАСНИХ ВИМОГ

Improving the reliability of test results is achieved by applying more advanced methods of recording and processing the results. Therefore, an important part of the study of the strength of freight wagons is the choice of methods for obtaining, processing and analyzing experimental data. The article outlines the procedure and algorithms for determining the equivalent stresses under longitudinal and dynamic loads acting during operation. It is shown that algorithms for determining stresses generated by dynamic longitudinal and vertical forces are significantly different due to various load application schemes. Thus, the testing of freight wagons under dynamic longitudinal loads is carried out by the impact against an experimental wagon, and testing under dynamic vertical forces is performed during the wagon motion in the composition of the experimental train on the characteristic, pre-selected (planned) sections of the railway track at specified speeds. To estimate the level of loading of the freight wagon structureunder vertical dynamic loads, a method based on the replacement of a real random process is used by some schematized process, which in terms of the fatigue damage accumulation should be equivalent to a real process. From the whole variety of schematic methods, two methods stand out, i.e., the full cycle method and the rainflow method, which most fully represent the real process.The advantage of the rainflow method is the ability to process the process in real time. However, the algorithm of the rainflow method is quite complicated and does not allow processing large amounts of information. In this regard, a method of maximum discharge was proposed, which is a kind of full cycles method and allows you to process an unlimited amount of information online. An example specified in GOST 25.101 was used for a comparative analysis of the rainflow and maximum discharge methods. Analysis showed a satisfactory matching of both methods. Based on the procedure outlined, the block structure of the computational process is proposed to determine the equivalent reduced voltage amplitude. Each block displays the impact of the forces depending on the loading condition, that is, longitudinal impact force and dynamic forces when the wagon is moving on straight track sections, curves and switches of the railway track. Key words: wagon car, process, dynamic load, longitudinal load, voltage, amplitude, algorithm, equivalent stress, safety margin, strength.

Permissible Values of the Dynamic Impact of the Rolling Stock on the Railway Track in the Case of Axle Load Increase

Purpose. The study is aimed at determining experimentally the values of the parameters characterizing the dynamic effect of rolling stock on the railway track, substantiating the maximum permissible (limiting) values. Methodology. To investigate the interaction between the track and the rolling stock, the devices to record various physical processes were installed on the experimental sections. The devices were installed in 8 sections along the outer railway line. To establish the actual state of the track, field measurements were carried out in accordance with the Program and research methodology. Findings. According to the results of experimental tests of the impact on the track, it was revealed that the average vertical loads, and, accordingly, the average vertical deformations, under the cars with an axle load of up to 25 tf/axle are higher than that under the cars with an axle load of up to 23.5 tf/axle by 8 percent. The maximum vertical loads under the cars with an axle load of 25 tf/axle exceeded the average loads by 10.0 tf, and under the cars with an axle load of up to 23.5 tf/axle exceeded the average values by 12.8 tf. During the tests, no cars were found in which the vertical dynamic force exceeds 20 tf, and the horizontal force exceeds 10 tf. Therefore, the norms of permissible dynamic impact can be taken in accordance with the Regulations on Preventive Maintenance and Repair Track Work on the Railways of Ukraine. Originality. The authors conducted a study to assess the dynamic characteristics of the interaction of track and rolling stock, in particular the stresses in the edges of the rail base, vertical and horizontal forces from the wheels of rolling stock. Practical value. On the basis of the results obtained, it is possible to estimate the permissible values of the dynamic effect of the rolling stock on the railway track to substantiate the need to change the standards for the material consumption of the track superstructure and labor. In turn, this will make it possible to plan the repair and track periods more economically and according to the actual indicators of the state of the track superstructure.

A New Method for Solving the Problem of Determining the Characteristics of Spatial Stiffness and Elasticity of the Rail Threads and Stresses and Strains in Rails

The reference data given in technical literature on the characteristics of spatial stiffness and elasticity of rail threads in the conditions of joint action on the rails of vertical and horizontal lateral forces and torsion are very different and in some cases contradictory. This situation is due to the lack of an accurate analytical solution to this problem and the provision for reference materials only experimental research data, which are clearly different, not only for different railway structures, but also significantly differ in different conditions of acting external forces (P, H, Mtor). The purpose of this article is to present a new method of analytical solution of the problem of determining the spatial characteristics of stiffness and elasticity of rail threads and also computation the stresses and strains that occur in them, under conditions of complex joint action on rail threads of vertical and horizontal dynamic forces (Pdyn, Hdyn) simultaneously with the external torque moment Mtor arising from off-center forces applied to the rails from wheel loads. The complex method of solving the problem was used in the paper. It includes the theoretical part and the results of the experiment. Using the experimental researches characteristics of horizontal lateral stiffness of the rail threads of the head and sole at different constructions of the modern rail fastenings was measured. The second task of determination of the real values of the characteristics of spatial elasticity and stiffness modulus of the rail thread under joint vertical and lateral horizontal bends of the rail in conjunction with its simultaneous torsion was solved by the theoretical methods. As the results of author’s researches were obtained new values of the characteristics of spatial stiffness and elasticity modulus of rail threads under joint vertical and lateral horizontal bends of the rail in conjunction with its simultaneous torsion. These characteristics were obtained for the modern railway track constrictions with rails (R65, R50, UIC60) on concrete and wooden sleepers and with rail fastenings unlined or lined types (KB, KPP-5, KPP-1, D0). And also these characteristics were obtained in the functional dependence on the ratio of vertical and horizontal lateral forces P/H.

Modeling the interaction of soil and a vibrating subsoiler using the discrete element method

A vibrating subsoiler can effectively reduce the draft force compared to a rigid one. Several theoretical and experimental methods have been developed to study the interaction of soil and vibrating tools, enabling the exploration of the mechanism of a vibrating subsoiler to reduce the draft force. However, these methods are unable to predict the dynamic force of tools and soil behavior because of nonlinear soil properties. This paper employs the discrete element method (DEM) to simulate vibrating tillage. The aim is to clearly understand the dynamic force of vibrating tools and soil behavior. Three different types of representative vibrating subsoilers and one rigid one were selected for this study. These subsoilers varied in their tines and vibrating structures. The DEM model of soil and subsoilers was established. Results showed that the draft and vertical dynamic forces of the vibrating tines periodically changed and had distinct peak and valley phases in one period. The value of the draft and vertical forces in the valley phase of a vibrating subsoiler was much less than that of the rigid one, which led to the decrease of mean draft force. The soil disturbance widths, velocities, and horizontal and vertical forces of soil particles also periodically changed. Soil ruptures mainly occurred when a tine vibrated in the forward direction. Compared with a rigid tine, a vibrating tine had more time to disturb soil particles and thus to achieve better soil fracture. The DEM model was validated by comparing it with an actual soil bin test. The errors of the simulation model in predicting the soil disturbance and forces were less than 13.23% and 9.65%, respectively, indicating that the model is a useful tool to simulate the dynamic interaction of soil and a vibrating subsoiler.

Research into the track/vehicle interaction processes for underground railways

The article deals with determination of dynamic forces in interaction between a rail vehicle and underground track for working out recommendations in terms of a longer service life of the permanent track without extra charges. The issue is of importance for enterprises under limited resources. The research was conducted with mathematical model methods for the vehicle/track dynamic system (the principles were developed earlier), as the experimental work in the underground tunnels was complicated by intensive train traffic during a day. A special feature of the research was consideration of a rail as a bar rested on discrete elastic-dissipative supports in a design diagram of the vehicle/track dynamic system. Thus, the authors established the effects of unequal elasticity of the track rail support on the value of vertical dynamic forces when a metro coach moves on the track. In particular, the dependencies of dynamic factors and amplitude ratios of vertical forces on speeds of metro coaches along the discrete elastic- dissipative track were obtained. An exceptional value of the research is consideration of both vertical and horizontal lateral forces on the vehicle/track interaction. It allowed the authors to define the value of vertical and horizontal lateral forces which occurred when metro coaches moved along straight and curved sections of the track according to the speed and curve radius.

Service life evaluation of ballastless track construction

The article presents method for calculating service life of ballastless track structure using the track oscillation model as a structure containing three infinitely long beams, the lower of which lies on the modified Winkler base, and the upper and middle are based on elastic layers, mainly having the characteristics of Winkler. The use of this model is due to the need to carry out calculation for bearing concrete slab, the destruction of which is the main reason for the failure of the ballastless track structure. First part of the article presents model for calculating service life of a ballastless structure. When calculating the damage index, which takes the stresses in the bearing concrete slab, to estimate the vertical dynamic forces acting on the track, it is proposed to use a frequency response that determines the dynamic system with input on the track unevenness and output on the dynamic force at the wheel and rail contact in the model oscillations of the track as a three-layer beam. Second part presents estimates of the service life of ballastless structure for various operating conditions and their comparison with the results obtained using the practice method with the single-beam model. Graphs were plotted for the service life of the ballastless track structure on axle loads, the speed of the carriages and the load capacity on the line. Results show the applicability of the single-layer beam model for estimating the service life of the ballastless track structure in the current operating conditions; however, for the promising conditions of high-speed and heavy traffic, it is advisable to use a three-layer model.

Material equivalence, modeling and experimental validation of a piezoelectric boot energy harvester

This paper presents a material equivalent model, electromechanical coupling finite element (FE) modeling and experimental validation of a piezoelectric energy harvester for energy harvesting from human walking. The harvester comprises of six piezoelectric stacks within force amplification frames (FAFs) sandwiched between two heel-shaped aluminum plates, which can be put inside shoes as a shoe heel. The harvester amplifies the vertical dynamic reaction forces with ground at a heel and transfers them to the inner piezoelectric stacks to maximize the power output. Symmetries in geometry, load and boundary conditions are fully exploited and the multilayered piezoelectric stack is simplified as an equivalent bulk to simplify the FE model and expedite dynamic analysis. Dynamic simulation is performed on the symmetric FE model over different external resistive loads with the measured forces at different walking speeds as inputs. The prototype of the harvester is fabricated and tested on a treadmill to validate the proposed material equivalent model and FE model. The simulation results agree well with both the experimental measurements and numerical predictions from the simplified single degree-of-freedom model. Parametric study is performed on the validated FE model to investigate the effect of geometric dimensions of the FAFs on the power output. The peak power outputs of 83.2 and 84.8 mW, and average power outputs of 8.5 and 9.3 mW are experimentally achieved at the walking speeds of 2.5 mph (4.0 km h−1) and 3.0 mph (4.8 km h−1), which agree well with the simulations. Simulation shows that an average power of 34.7 mW can be obtained at 6.0 mph (9.7 km h−1).

Non-invasive measurement of floating–sinking motion of a large object in a gas–solid fluidized bed

A Lagrangian sensor system has been established to non-invasively measure both the vertical position and dynamic force acting on itself. It consists of a 3-axis acceleration sensor, a 3-axis magnetometer, a microcontroller, a wireless module, batteries, and external electromagnetic coils. In this study, we applied the system to a free-moving coarse object in a gas–solid fluidized bed. The floating and sinking motions of the object in the fluidized bed are essentially caused by differences between its density and the apparent density of the fluidized media. However, the object sometimes shows strange behavior under the influence of variance in the fluidization state. We measured the temporal change of the upward force acting on the object as well as the vertical position, which is invisible from the outside. The experimental results indicate that the force acting on the object differs significantly between the floating and sinking states and is greatly complicated by interference with rising bubbles in the fluidized bed. The probability density of the vertical position of the object shows that its motion is explained not only by hydrostatic effects, but also by inhomogeneity of the fluidization state in the bed.

A probabilistic estimate of the vertical dynamic forces acting on the track, in the model of a three-layer beam under the influence of a four-axle freight car

The article contains a method for determining the ma-the permanent way as deflections, angles of section rotation, bending trix of mutual spectral densities of vertical dynamic forces acting on a moments, transverse forces, stresses of its three-layer structures. railway track, depending on its spectrum of irregularities. It will allow to Mathematical model of track oscillations is used for calculations make a more accurate calculation of the mean values and mean-square as a construction containing three infinitely long beams, the lower deviations of vertical dynamic forces, as well as such characteristics of of which lies on the modified Winkler base. Authors present formulas for finding amplitude-frequency characteristics connecting vertical deflections of structural layers and vertical dynamic load acting on a track. A method is described for finding a matrix of mutual spectral densities of vertical dynamic forces acting on a track having real deviations from its position in the profile, with the passage through it of a four-axle freight car. Considered example finds the amplitude-frequency characteristic that connects the vector of dynamic forces in the contacts of wheels and rails with the vector of vertical displacements of wheel centers for the model of a four-axle car. Concluding authors give the results of calculations of the amplitude-frequency characteristic of the elements of the matrix of mutual spectral densities of vertical dynamic forces acting on the track. The received statistical estimations can be used at calculations of service life of ballastless track constructions and loading on roadbed.

Touchdown Remaining Lift on the Wings and Dynamic Vertical Force Transmitted to the Runway

Airfield pavements are designed to handle an increasing volume of conventional aircraft, but in the future they may be required to accommodate both unmanned aircraft and space vehicles; these have their own unique requirements in terms of pavement strength and durability.This study deals with the problem of application of loads on the runway during landing. The solution of this problem, necessary for the correct construction of the decay curve, has been studied with reference to the Grip Number (GN). The experiment has been conducted on the runway of the Airport of Lamezia Terme ( IATA: SUF, ICAO: LICA) - Italy. Traffic data (from 2010 to 2014) and data on surface features (in terms of GN) for the same period (according to the Publication-ICAO Doc.9137-AN / 898, where guidelines Speed equals 65 km / h) were acquired for the goals of this study.The analysis of the data has supplied important information about the conditions of application of the loads on the Runway. In particular, through an optimization procedure and the use of the technique OLS, a relationship of application of loads on the runway has been proposed and furthermore two different areas, in reference to the methods of the application of loads in the process of landing, have been defined: a first part x1 within which the load is applied gradually with a linear law, and a second part (L-x1), in which all the load is applied with a constant law.

Analysis of Vertical Irregularities and Dynamic Forces on the Switch Frogs of the Underground Railway

This article presents the analysis of vertical irregularities and dynamic forces on the switch frogs in operating conditions on the main tracks of Kiev underground railway. For main railways the deterioration problem of tongues, framed rails, switch frogs and as a consequence formation of the character in interaction on the railroad switches is quite widely studied by different scientists, but for conditions of railway underground such researches are practically absent. However, in order to use metal elements of switches rationally and efficiently, the forecast of their service operation and replacement planning, it is necessary to estimate the level of dynamic forces within the most deteriorated elements of switches at different operational stages. This problem is particularly relevant in conditions of financial restriction for track facilities. The studies allowed determining the form, parameters and basic patterns of the irregularities formation in the rolling zone on switch frogs P65 and P50 mark of crossing 1/9 on wooden beams under different operating conditions, which is the basis for determining vertical dynamic forces of interaction within the switch frog subject to setting maximum permissible speeds of movement.