Piotr Szurgott

Numerical analysis of a shaped rail pad under selected static load

Numerical analysis of selected type of the polyurethane rail pad is presented in the paper. A shaped pad with cylindrical-shaped elements in its working section was selected as a representative for the computational simulation. Analysis reflected the experimental test according to the valid standard. The test included loading of the vertical force perpendicular to the foot of the rail. Such test allows determining the static stiffness of the pad. The Mooney – Rivlin material model was selected in the current study. Necessary experimental tests including a uniaxial compression and tension were conducted to provide material constants for the hyperelastic material model applied for the FE model. Simplified FE models of the considered rail pad and the rail were developed. Rounded corners and edges of the cylindrical-shaped elements were omitted, since their modelling required a significant density of the FE mesh. Vertical force perpendicular to the foot of the rail was declared as nodal force distributed evenly along the edges of the selected finite element models Non-linear static analysis was performed using MSC.Marc software with large displacements and deformations taken into consideration. The obtained results allowed estimating deformations and the state of stress in a highly deformed rail pad. The static stiffness of the pad was defined as secant stiffness based on the vertical force – deflection curve.

Experimental Assessment of Dynamic Responses Induced in Concrete Bridges by Permit Vehicles

Results from experimental testing of three permit vehicles are presented in the paper. The selected heavy vehicles, which require permits from state DOTs, included two tractor-trailer systems and a midsize crane. The vehicles were experimentally tested on popular existing speed bumps and on a representative highway bridge. The selected bridge was a reinforced-concrete structure constructed in 1999, located on the U.S. 90 in Northwest Florida. The bridge approach depression, combined with a distinct joint gap between the asphalt pavement and the concrete deck, triggered significant dynamic responses of the vehicle-bridge system. Similar dynamic vibrations were observed and recorded when the permit vehicles were driven over the speed bumps. Time histories of relative displacements, accelerations, and strains for selected locations on the vehicle-bridge system were recorded. The analysis of experimental data allowed for assessment of actual dynamic interactions between the vehicles and the speed bumps as well as dynamic load allowance factors for the selected bridge.

HYBRID LOCOMOTIVES OVERVIEW OF CONSTRUCTION SOLUTIONS

Nowadays, transportation becomes a significant source, apart from factories and power plants, of air pollution. Therefore, due to legal restrictions on the emission of noxious gases, other power sources for vehicles are necessary. Some of these power sources allow replacement of the internal combustion engine completely, whereas the other ones only support the engine operation. Hence, a hybrid powertrain – alternative to the drivetrain equipped with an internal combustion engine only – is increasingly being used. The hybrid powertrain was mostly applied in cars and buses but recently it has been also used in railway vehicles such as locomotives and multiple units. The paper presents a shortened and brief overview of construction solutions of selected hybrid locomotives. A list of the applied hybrid drive systems as well as the basic data and properties are provided. The most important variants of vehicles are compared. The presented material allows identification of the development trends in the considered area. The hybrid locomotive usually uses an onboard rechargeable energy storage system, placed between the power source and the traction transmission system connected to the wheelsets. Modification of a classic diesel-electric locomotives is a relatively simple procedure since they have all the components of a series hybrid transmission except the storage battery. Therefore, the existing and operated diesel-electric locomotives can be modified to increase their efficiency and reduce operating costs and emissions.

Experimental validation of numerical modelling of the bridge-track-moving train system

A new methodology of physical and FE modelling and simulation of bridge–track –moving train (BTT) systems has been developed with the use of commercial CAE systems. A methodology is related to composite (steel-concrete) bridges, ballasted tracks and high-speed trains. In the methodology, Altair HyperMesh, LS-DYNA, LS-PrePost and HyperView software was applied. The methodology is based on homogenization of reinforced concrete (RC) platform slab, RAIL_TRACK and RAIL_TRAIN LS-Dyna’s modules for simulating the moving train–track interaction, non-linear modelling of rail fastenings and crushed stone ballast, application of cylindrical and revolute constrained joints and discrete springs and dampers for modelling suspensions in rail-vehicles. For experimental validation of numerical modelling and simulation of BTT systems, the KNI 140070 composite viaduct and the EuroCity EC 114 train moving at 160 km/h have been selected. The experimental setup contained Keyence LK-G 157 system (CCD laser displacement sensors), PULSE system (acceleration sensors), and PHANTOM v12 high-speed camera. According to the experiment plan, selected vertical displacements and vertical and horizontal accelerations vs. time were measured. The simulated time-histories of displacements and accelerations have been compared to respective experimental diagrams. The results have proved that the validation is positive.

Modelling and simulation of repeated charging/discharging cycles for selected nickel-cadmium batteries

The main aim of the paper is to present a developed methodology of simulation of the energy efficiency of a selected energy storage unit. The authors focused their actions on batteries that could be the base for an energy storage system possible to apply in a modernized hybrid-shunting locomotive. Three different nickel-cadmium batteries were selected as representatives for the study. Simulation was focused on repeated cycles of charging and discharging the batteries. The simulation model generally consists of three main components: a specified load cycle, a dynamic model of the DC electrical machine and a model of the Ni-Cd battery. The input data for the battery model is based mostly on the parameters provided by the manufacturer data sheets. However, an internal resistance had to be measured for each battery. Conducted simulations provided information about the electromotive force, state of charge, an average efficiency of the battery, as well as the temperature changes during the cycle. The proposed approach to the battery simulation can be also applied for the loading cycles similar to those that occur during the actual operation of the locomotive. The current study is a part of the project focused on modernization of the dieselelectric shunting locomotive to the hybrid one.

Development of finite element model of shunting locomotive applicable for dynamic analyses

The main aim of this study is to develop a finite element model of the hybrid-shunting locomotive. Considered locomotive is based on a popular shunting locomotive in Poland – SM42. All components above the locomotive frame could be modified in comparison to the original object, whereas a chassis was essentially unchanged. Such solution allows the operators freely configure components e.g. diesel engine, generator, cooling module, cab etc., according to their own requirements. Works on the FE model were focused on very accurate reflection of the locomotive frame since the planned dynamic analyses include crash tests. FE model of the frame has a fine mesh and it is considered as a deformable component. Other segments of the vehicle are simplified and treated as rigid bodies mostly. FE model was developed on the basis of the locomotive CAD model. It was decided to transform the CAD model of the frame into the FE one applying the midsurface procedure. Such approach is correct since the locomotive frame is made of a large number of steel elements in the form of sheet metal plates and sections welded together. Altair Hyper Mesh software was used in the FE model developing process. Appropriate connections between respective components of the model e.g. wheelset – bogie, bogie – locomotive frame, were applied. Finally, the locomotive FE model consists of about 116 thousands of finite shell and solid elements and about 125 thousands of nodes. Dynamic analyses of the locomotive FE model will be carried out using LS-DYNA computer code.

Modelling and simulation of crash tests of N2-W4-A category safety road barrier in horizontal concave arc

ABSTRACT The paper examines a road safety barrier of a N2-W4-A class, with a B-type guide bar, located on a road bend of a 150 m radius and shaped as a horizontal concave arc. In order to ensure accepting the TB11 and TB32 standard crash tests, a composite/foam/rubber overlay is designed, combined with the guide bar with screw connectors spaced by 2 m. The study develops a methodology for numerical modelling and simulation of unmodified (a straight barrier) and modified (a curved barrier) crash tests, without and with the overlay, including deformable joints with limited load capacities, contact with friction, tire pressure, posts embedded in deformable subsoil, gravity load and damping. The TB11- and TB32-simulated crash tests are conducted for the four above-mentioned barrier systems. It has been proved that the barrier with the overlay provides approval for the standard crash tests on road bends.

NUMERICAL ANALYSIS OF THE FRONT IMPACT BETWEEN TWO SHUNTING LOCOMOTIVES

The main aim of this study is to carry out dynamic finite element analysis of a crash between two identical shunting locomotives. Numerical simulations include front-end impact of the running locomotive with a stationary one situated on the track. The first design collision scenario includes such obstacle for railway vehicles operated on national and regional networks. A considered locomotive based on a popular Polish shunting locomotive – SM42. However, the tested locomotive was slightly modernized in comparison with the original one. Finite element model of the locomotive was developed by the authors. FE analyses were carried out according to the PN-EN 15227 standard, which provides crashworthiness requirements for railway vehicle bodies. LESS-DYNA computer code was used for the simulations. The energy balance was initially checked in order to confirm the accuracy of analysis. The paper presents selected results of analyses focused on the locomotive frame behaviour. Contours of effective stress for selected moments of time are presented. Time histories of selected parameters are also depicted. The current study is a part of the project focused on modernization of the SM42 locomotive. Therefore, it is required to evaluate the locomotive behaviour during the impact test. Dynamic numerical simulation is acceptable since the experimental tests on the complete objects under consideration are impractical and impossible at the moment.

Dynamic Interaction Between Heavy Vehicles And Speed Bumps.

The paper presents finite element (FE) model development and experimental validation for a truck tractor with a three axle single drop lowboy trailer. The main objective of this research activity was to create a simplified, three dimensional virtual FE model, applicable for computer simulation of dynamic interaction between a vehicle and a bridge or road structure. Such model should provide a reliable approximation of dynamic loadings exerted by the wheels to the bridge or pavement structure for a wide range of total weights and speeds considered. To meet this requirement the FE model should have correct mass distribution and properly represented stiffness characteristics of the suspension system. As explicit laboratory testing of the suspension system requires its disassembling and is very expensive, an indirect method was applied to find the stiffness and damping characteristics of the suspension. The study reported in this paper consists of experimental and numerical parts. During the experimental tests the vehicle was driven across the speed bumps at different speeds. The relative displacement and acceleration histories were recorded for several points located on the vehicle axles and the frame. In addition, a speed bump was scanned on site using a laser scanner. The experimental data was subsequently used for the development and calibration of the spring and damping characteristics for suspension systems of the FE model. The numerical part was based on non-linear, explicit, dynamic, finite element (FE) analysis using the LS-DYNA computer code.

PRELIMINARY NUMERICAL ANALYSIS OF SELECTED PHENOMENA OCCURRING IN A RAIL FASTENING SYSTEM

The results of numerical analysis of selected phenomena occurring in a rail fastening system were presented in the paper. The study is focused on assessment of the state of displacement and stresses in the rail pad subjected to a moving load. Two finite element models of the considered system were developed. The first one included elementary track segment corresponding to one sleeper. The second FE model consisted of several elementary segments. The number of the track segments was determined independently on the basis of dynamic analysis carried out using LS-DYNA computer code. Essential FE analyses were performed using MSC.Marc/Mentat software. FE model of the elementary segment included 600 mm length rail and a two-side shaped rail pad. The Mooney – Rivlin material model was applied for the polyurethane rail pad. The fastening systems were modelled using spring elements. The vertical and longitudinal spring elements were also applied for the ballast modelling. A case of moving load caused by single vertical force – one axle – was considered in the study. Methodology of moving load simulation in the MSC.Marc software was proposed. The obtained results allowed assessing the total deflection of the rail pad, the state of stress, the load distribution on respective sleepers. Moreover, they gave information about the behaviour of the rail pad under moving load in context of static test described in respective standards.