abstract / Mechanical Engineering / Master / Master of Philosophy

Severe railcar responses can result from crosslevel and vertical rail inputs. At low speeds rail joint excitation can coincide with the roll natural frequency of a vehicle. At high speeds, dynamic effects can cause high wheel loads and harsh ride for sensitive cargos. Computer simulation of these and other vertical dynamic effects cans assist in design selections of vehicle components and diagnosis of troublesome vehicle responses. Many dynamic models available today lack the complexity to analyze accurately some of the important dynamic effects. In this report a 28-degree-of-freedom railcar model has been developed to analyze the vertical dynamic responses of railcars subjected to random and deterministic track inputs. This model features carbody vertical bending and torsional modes, multiple component trucks and suspensions, and rail irregularity inputs at each of the eight wheels. Simulation results for a 100-ton vehicle operating on harmonic track inputs compare favorably with the AAR Flexible Carbody Model. Other simulations on random track evaluate the influence of auxiliary viscous stabilizers and increased payloads on railcar responses. These simulations demonstrate the effectiveness of the computer simulation as a design and analysis tool. / M.S.

M.Ing. / Sound pressure levels exceeding acceptable limits are being generated by trains travelling on the 1000 m radius curved railway line past the town of Elands Bay. Unacceptable sound levels are attributed mainly to top of rail wheel squeal. Top of rail wheel squeal belongs to the family of selfinduced vibrations and originates from frictional instability in curves between the wheel and the rail under predominantly saturated lateral creep conditions. In small radius curves, saturated lateral creep conditions occur due to the steering of railway wheelsets with large angles of attack. Given the large curve radius and the utilisation of self-steering bogies on the Sishen-Saldanha Iron Ore railway line, curve squeal is a highly unexpected result for the 1000 m radius curved railway line. This is because curving of bogies in large radius curves are achieved without high wheelset angles of attack leading to saturated creep conditions. An experimental and analytical investigation was carried out to identify the mechanisms influencing the generation of wheel squeal in large radius curves. Simultaneous measurement of sound pressure and lateral wheel-rail forces were made during regular train service in one of the two 1000 m radius curves at Elands Bay to characterise the bogie curving behaviour for tonal noise due to wheel squeal occurring in the large radius curve. The lateral force curving signature not only reveals the levels of lateral wheel-rail forces required for bogie curving, but also whether the bogie is curving by means of the creep forces generated at the wheel-rail interface only or if contact is necessitated between the wheel flange and rail gauge corner to help steer the bogie around the curve. The test set-up consisted of two free field microphones radially aligned at equivalent distances towards the in – and outside of the curve in line with a set a strain gauge bridges configured and calibrated to measure the lateral and vertical forces on the inner and outer rail of the curve. This test set-up allowed the squealing wheel to be identified from the magnitude difference of the sound pressures recorded by the inner and outer microphones in combination with comparing the point of frequency shift of the squeal event due to the Doppler Effect with the force signals of the radially aligned strain gauge bridges. From the experimental phase of the investigation, it was found that wheel squeal occurring in the 1000 m radius curve at Elands Bay is characteristic of empty wagons and is strongly related to the squealing wheel’s flange/flange throat being in contact with the gauge corner of the rail. Here high levels of spin creepage associated with high contact angles in the gauge corner lead to high levels of associated lateral creepage necessary for squeal generation. This is in contrast to lateral creepage due to high wheelset angles of attack being the key kinematic parameter influencing squeal generation in small radius curves. Furthermore, the amplitude of wheel squeal originating from the passing of empty wagons was found to be inversely proportional to the level of flange rubbing on the squealing wheel i.e. increased flange contact on the squealing wheel brings about a positive effect on squeal control. Contrary to the empty wagons which are characterised by tonal curve squeal, loaded 4 wagons requiring contact between the wheel flange and rail gauge corner in the 1000 m curve was characterised by broadband flanging noise. It was concluded from measurements that flange contact occurring under high lateral forces for steady state curving of loaded wagons provides the complete damping necessary for squeal control. The curve squeal noise that originated from the passing of empty wagons in the Elands Bay curve could further be classified according to the frequency at which the squeal event manifested itself in the curve, i.e. low frequency audible (0 – 10 kHz), high frequency audible (10 – 20 kHz) and ultrasonic squeal (> 20 kHz). The vast majority of low frequency audible squeal events recorded in the 1000 m Elands Bay curve occurred at approximately 4 kHz and originated from the low rail/trailing inner wheel interface, whilst the vast majority of high frequency audible squeal events occurred in the frequency range between 15 and 20 kHz and originated from both the high rail/leading outer wheel and low rail/trailing inner wheel interfaces.

In this thesis, a computer program for graphically displaying finite element beam stresses is discussed. Beam elements are represented as thick lines with colored stress contours along the length. Stress gradients through the beam thickness are not displayed. Many program options are available to aid in creating a clear view of stress distributions in complex models. The front, right, top, and isometric views are preprogrammed views, or a rotated view of the model can be specified. Also, specific portions of the model can be magnified. A region may be defined for showing cut sections of the model. Contour options are available to help enhance stress representation. Node locations may be marked, and beam line widths modified. Finally, any view that has been developed can be saved in a file to be redisplayed at a later time. The program also has the capability of displaying resultant beam forces and moments. Beam stress displays for two train car models are used to demonstrate the usefulness of the program as both a presentation and modeling diagnostic tool. Stress gradients and high-stress regions are easily seen. With these displays some model discrepancies were uncovered and some highly stressed locations were observed that had not been discovered in the prior research. / Master of Science

This paper presents a static three-dimensional finite element analysis and redesign of a railroad hopper car draftsill. The purpose of the work was to modify the current draftsill structure to minimize its weight without compromising its current capabilities and foundry production specifications. The intuitive optimization procedure used both linear and parabolic isoparametric solid finite element models to check for solution convergence. In order to intuitively optimize the models, a composite plotting program was developed to display only the highest stresses at each node from all loading cases. This allowed for an overall visualization of low stressed regions for potential weight reduction. An additional study investigated the possibility of tapering the front and rear draftlugs for a better stress distribution in the draftsill's structure under loading. It was determined that a tapered relief of 0.025 - 0.050 in.(0.0635 - 0.127 cm) from the center of the draftlug to its outer edge would more effectively distribute the stresses created, and also reduce the maximum stress levels generated by at least 20 percent. All loading and geometry specifications used in this research were based on data provided by the Norfolk Southern Corporation. If both the redesign and tapered relief are adopted, then the final redesign will produce a draftsill that is approximately 106 lb(471.5 N) or 9.6 percent lighter than its original weight with maximum stresses reduced by 20 percent. / Master of Science

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Susan Marie Krolewski. / M.S.

Rail vehicle designers and analysts can benefit from the results of vehicle parameter estimation. Using this technique, they can determine the effects of suspension design decisions, and they can reduce the amount of on-track testing required to qualify new designs for service. This work addresses two major issues: the determination of parameter identifiability and the estimation of rail vehicle parameters from laboratory tests. Usually, the identifiability issue should be addressed first since identifiability determines the number of independent parameters that can be estimated. The general issues of identifiability and parameter estimation are discussed. Two identifiability tests are explored in-depth, as is a Bayesian least-squares parameter estimation method. Laboratory tests from a lightweight intermodal rail vehicle with single-axle trucks provided the data for the parameter estimation. The test setup and a simple vehicle mathematical model provided the structure for the identifiability determination. This work shows that identifiability and estimation issues closely interact. Even if a system is not identifiable, the Bayesian estimation method can return results. Thus, the Bayesian method can instill false confidence in the validity of the estimation results. Estimation of experimental data with a linear model provided values within one percent for the mass and damped natural frequency, and ten percent for the peak amplitude. Excellent agreement with the experimental data was obtained for frequencies above the resonant peak and for very low frequencies. Error at frequencies slightly below the resonant peak, however, indicated the vehicle contained significant nonlinearities. To achieve closer agreement between model response and test response at these frequencies, a nonlinear vehicle model is needed. / Master of Science

The understanding of rail vehicle steady-state and dynamic curving has increased substantially in the last few years. Contemporary curving models include such nonlinear effects as two-point contact, creep force saturation, and rail flexibility. The usual approximation concerning the contact geometry is that the Iocalized wheel and rail curvatures at the center of the contact patch are constant throughout the contact patch. This approximation allows computation of contact stresses using Hertzian theory, and it allows the computation of contact patch forces using one of Kalker’s theories. In vehicle curving, contact usually occurs at or near the wheel flange, where the wheel/rail contact geometry is non·Hertzian. Furthermore, after being in service for some time, the wheel and rail profiles provide non·Hertzian geometry due to wear. Both of these effects tend to invalidate the assumption of Hertzian contact geometry in the contact region. This work uses a generic wheelset model which is the basic component of any rail vehicle model. The wheel/rail interaction is modelled using the finite element method. The wheel is generated as a surface of revolution of its tread profile, and the rail is generated as an extrusion of the rail head profile. Three—dimensional contact elements are used to characterize the wheel/rail interface. A simple stick/slip friction model is used wherein relative motion is permitted if the tangential force exceeds the adhesion limit, and no relative motion occurs otherwise. The results show that the finite element method was successfully used to solve the static contact problem. Both Hertzian and non-Hertzian contact problems were anaIyzed correctly. However, the application of the finite element method to the rolling contact problem was not completely successful. The finite element method results for tangential contact forces were about 25 percent lower than forces predicted by Kalker’s theory. Recommendations for extending the analysis to solve the rolling contact problem are made. The report includes a derivation of the wheelset steadystate equations of motion, as well as a solution algorithm for the nonlinear, algebraic equations. / Master of Science / incomplete_metadata

Orientador: Franco Giuseppe Dedini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-22T04:27:38Z (GMT). No. of bitstreams: 1 Eckert_JonyJavorski_M.pdf: 14458146 bytes, checksum: b2eb0f5d4618d1873858f49c66965bec (MD5) Previous issue date: 2013 / Resumo: Dinâmica veicular é o estudo das interações entre o veículo, condutor e o ambiente bem como as reações de carga, sendo esta dividida em 3 grandes áreas: dinâmica longitudinal, vertical e lateral. Existem variações entre os métodos propostos pela literatura para o cálculo da dinâmica longitudinal do veículo, sendo que o objetivo deste trabalho é, por meio de simulações, compararem os resultados obtidos pelas diversas metodologias. Por meio de um modelo gerado com auxílio do programa de análise dinâmica de multicorpos Adams®, juntamente com o Simulink Matlab®, foram implementados os métodos de cálculo propostos pela literatura de forma a simular o comportamento de um veículo em função de uma demanda de potência gerada por meio do padrão de velocidades imposto pelos ciclos das normas brasileiras NBR6601 e NBR7024. Os resultados encontrados foram comparados por meio da correlação linear entre as curvas de torque resultantes do modelo dinâmico, possibilitando uma avaliação entre os resultados encontrados pelos diferentes métodos. Também foram avaliados o consumo de combustível, a influência da variação da massa do veículo e da estratégia de condução no comportamento dinâmico do veículo, bem como modelos complementares referentes a veículos híbridos e o efeito da adição de um modelo de embreagem no conjunto simulado / Abstract: Vehicular dynamics is the study of interactions between vehicle, driver and load reactions. The vehicular dynamics is divided into three areas: longitudinal, vertical and lateral. There are variations between the methods proposed in the literature to calculate the longitudinal dynamics of the vehicle. The purpose of this study is, through simulations; compare the results obtained by different methods. By means of a model generated by Adams® (Software of Multibody Dynamics Analysis) together with Simulink Matlab® were implemented the calculation methods proposed by literature to simulate the behavior of a vehicle according to a power demand resulting from the default speeds cycles required by Brazilian Standards NBR6601 and NBR7024. The results were compared using linear correlation between the couple curves resulting from the dynamic model, allowing an evaluation of the results reported by different methods. Were also evaluated: the fuel consumption and the influence of the mass vehicle variation, the driving strategy in the vehicle dynamic behavior, some complementary models of hybrid vehicles and the effect of add a clutch model / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica