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1.	Abadikhah, Hossein, 1987, et al. (författare) Dynamic Higher Order Functionally Graded Micropolar Plate Equations 2014 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 106 Tidskriftsartikel (refereegranskat)abstract The work, described in this paper, considers the analysis and derivation of dynamical equations on rectangular functionally graded plates governed by micropolar continuum theory. The proposed method is based on a power series expansion of the displacement field, micro-rotation field and material parameters in the thickness coordinates of the plate. This assumption results in sets of equations of motion together with consistent sets of boundary conditions. These derived equations are hyperbolic and can be constructed in a systematic fashion to any order desired. It is believed that these sets of equations are asymptotically correct. The construction of the equation is systematized by the introduction of recursion relations which relates higher order displacement and micro-rotation terms with the lower order terms. The fundamental eigenfrequency is obtained for the plate using different truncations orders of the present theory. Also various plots of mode shapes and stress distributions are compared for the fundamental eigenfrequency.
2.	Abadikhah, Hossein, 1987, et al. (författare) Higher order beam equations 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 99 Tidskriftsartikel (refereegranskat)abstract This paper considers the dynamic equations of circular cylindrical beams. The method is based on the three dimensional theory, adopting the generalized Hamilton's principle. By adopting a power series expansion method in the radial coordinate, together with a Fourier series expansion in the circumferential direction, this procedure results in sets of equations of motion together with consistent sets of end boundary conditions. These are derived in a systematic fashion up to arbitrary order, and are believed to be asymptotically correct. As such, the equations of motion are hyperbolic. Among the derived equation set are recursion relations, from which it is possible to express higher order displacement and stress fields in terms of lower order displacement fields. Results are obtained for all Fourier modes, among which axisymmetric, torsional and flexural modes are special cases. Special attention is paid towards the flexural mode. Using different truncation orders of the present theory, comparisons may be performed with classical theories such as the Euler-Bernoulli and the Timoshenko theories, besides the exact theory. Numerical examples are presented for dispersion curves of an infinite beam for the three lowest modes. Here various truncation orders are presented, as well as the exact theory. It is clear that higher accuracy is obtained as more terms are used. The lowest mode curve is accurately captured in the lower frequency range for all theories. Higher order truncations are indistinguishable from the exact curves in the presented range. Concerning eigenfrequencies, the three lowest frequencies for two different beams are presented for different truncation orders, classical theories as well as the exact theory for simply supported ends. As for the dispersion curves, the series expansion results converge to the exact results as the power series orders are increased. It is clear that more accurate results are obtained for lower frequencies and slender beams as expected. The Timoshenko theory is astonishingly accurate while the Euler-Bernoulli theory confirms the well known fact that this theory renders reasonably accurate results for slender beams in the low frequency spectra. Various plots on mode shapes and stress distributions are compared for the fundamental frequency for a simply supported beam. Here the curves using the lowest series expansion theory are very close to the exact results. There are more pronounced differences between theories for the mode shapes and the stress distributions, compared to the eigenfrequency calculations and the dispersion curves. The differences are most prominent for the stress distributions.
3.	Abbasi, Saeed, 1973-, et al. (författare) Particle emission from rail vehicles : A literature review 2012 Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F. - Stirlingshire, UK : Sage Publications. ; 98 Konferensbidrag (refereegranskat)abstract Emission of airborne particles is a side effect from rail transport. This work reviews recent research on particle emissions from rail vehicles. Both exhaust and non-exhaust particle emissions are characterized by size, morphology, composition, and size distribution. Current legislation, knowledge of adverse health effects, and available and proposed solutions for emission reductions are also treated. There has been much focus on exhaust emissions, but only a few limited studies have investigated non-exhaust particle emissions, which contain a significant amount of metallic materials. A new method for measuring the airborne wear particle emission rate (AWPER) is proposed as a first step to guide new legislations and to focus further research on non-exhaust airborne emission, i.e., research on the generation mechanisms for particle emissions and their adverse health effects.
4.	Andersson, Evert, et al. (författare) How to find a compromise between track friendliness and the ability to run at high speed 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract When designing and optimizing a rail vehicle there is a contradiction between, on the one hand, stability on straight track at high speed and, on the other hand, reasonable wheel and rail wear in small- and medium-radius curves. This paper describes the process of developing and optimizing a track-friendly bogie. A simulation model has been used to investigate dynamic stability on straight track at high speeds along with the wheel and rail wear in sharper curves. The result is a bogie with relatively soft wheelset guidance allowing passive radial self-steering, which in combination with appropriate yaw damping ensures stability on straight track at higher speeds. This bogie has been tested according to EN 14363 at speeds up to about 300 km/h and in curves with radii ranging from 250 m and up.
5.	Arvidsson, Therese, et al. (författare) Modelling alternatives in the dynamic interaction of freight trains and bridges 2014 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-comp press. - 1759-3433. ; 104 Tidskriftsartikel (refereegranskat)abstract This paper focuses on studying the dynamic response of bridges under passing freight trains. To increase transport efficiency, infrastructure mangers are asked to allow for higher freight train speeds and higher axle loads. However, little work has been done on the influence of increased freight train speeds on bridges. In this paper a two-level factorial experiment was used to identify the most important factors in train-bridge interaction systems comprising the Swedish Steel Arrow freight train passing over simply supported beam bridges. Thereby, the effect of a simple 2D multibody model as opposed to moving forces was set in relation to variations in other key system parameters. Preceding the factorial experiment, four train models were compared to determine a relevant vehicle idealisation. Through the factorial design, effects of single parameters, as well as joint effects from simultaneous changes in several parameters, were evaluated. The type of load model was found to have a large effect, reducing the bridge deck response at resonance considerably for the four studied bridges of span 6, 12, 24 and 36 m. For the relatively light 24 and 36 m span bridges, clear resonance peaks from heavy freight train passages in the speed interval 50-150 km/h were much reduced.
6.	Bornet, Lucie, et al. (författare) Influence of the ballasted track on the dynamic properties of a truss railway bridge 2014 Ingår i: Civil-Comp Proceedings. - : Civil-Comp Press. - 1759-3433. ; 106 Tidskriftsartikel (refereegranskat)abstract This paper presents numerical and experimental analyses of a steel truss railway bridge. The main interest of this work is that dynamic experiments have been performed before and after the ballasted track was placed on the bridge. Consequently, it has been possible to quantify the effect of the ballast and the rails on the dynamic properties of the bridge. For that, two finite element models, with and without the ballasted track, have been implemented and calibrated using the experimental results. It appears that the ballast gives an additional stiffness of about 25-30% for the lowest three eigenmodes. This additional stiffness can be only partly explained by the stiffness of the ballast. In fact, it seems that this additional stiffness also results from a change of the support conditions.
7.	Casanueva, Carlos, et al. (författare) Payload optimization of articulated wagons considering train length and vehicle dynamic behaviour 2016 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract The Capacity4Rail EU project aims are improving the competitiveness and reliability of rail freight in order to make it more attractive for modern, more sophisticated market requirements. The work described in this paper, focuses on novel vehicle designs that can account for a higher payload per meter, both from the payload optimization and the vehicle dynamic response point of view. We analyze an articulated spine wagon composed of five car bodies and six bogies, of which four of them are shared between two car bodies. In the work package, there has been an effort to look into the implications of these very long wagons in all aspects of freight operation, and this paper focuses on two of these aspects: the gain in payload by using different configurations, and the analysis of the dynamic response of the running gear. The conclusion is that, from vehicle performance point of view, it is worth exploring the possibility of increasing payload by slightly reducing the dynamic behavior of the system, as the twelve-axle vehicle is much more flexible when it comes to modern multimodal transportation.
8.	Cha, Yingying, 1989-, et al. (författare) On particulate emissions from individual trains in tunnel environments 2016 Ingår i: Civil-Comp Proceedings. - : Civil-Comp Press. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract In order to detect the concentrations and size distributions of airborne particles that were generated by individual moving trains on an underground railway platform, a series of real-time measurements were undertaken. The measurement range covered the ultrafine (less than 100 nm) and partly the fine (100 nm to 2.5 μm), but not the coarse fraction (2.5 to 10 μm). The results show that the individual trains with stop and start at the platform elevate substantially the particulate number concentrations with a diameter size greater than 100 nm. Two size modes of the particulate number concentrations are obtained. One mode peaks around 170 nm when a train stopped/started, while the other is around 30 nm when no train operated in the station. By using principal component analysis, four components are extracted from the thirty two-analyzed particulate sizes, indicating four different contributors in those detected particles. It is revealed from this study that the particulate matter released by individual moving trains (mainly through mechanical wear and turbulent resuspension) is a key contributing source of the fine particles on underground railway platforms, which can be separated from the background by their different size distributions.
9.	Eriksson, Anders (författare) Instabilities in pressurized membranes 2014 Ingår i: Civil-Comp Proceedings. - : Civil-Comp Press. - 1759-3433. ; 106 Tidskriftsartikel (refereegranskat)abstract This paper discusses instabilities occuring in thin pressurized membranes, important in biological as well as in engineering contexts. The membranes are represented by only their in-plane stress components, for which an incompressible isotropic hyper-elastic behavior can be assumed. The inherently non-linear response to pressurization can give instabilities in the forms of limit points with respect to a loading parameter, but also bifurcations and wrinkling. The hyper-elastic material model itself can also, under some circumstances, lead to a bifurcation situation. The instability situations can be included as constraints in a structural optimization. The paper discusses the formulation, the solution methods and some relevant instability situations. A numerical example considering the internal pressurization of a cylindrical pre-stressed membrane illustrates some aspects of instability.
10.	Höjer, M., et al. (författare) A noise related track maintenance tool for severe wear detection of wheel-rail contact 2016 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract An on-board measurement system has been developed that in real time identifies the probability for occurrence and also the exact location of severe wear in the wheelrail contact. Noise generated by the wheel-rail contact is a troublesome side effect both when railway vehicles negotiate curves and run on straight tracks. The concept behind this project is to use this noise as an indicator of the transition from the mild wear regime to the severe/catastrophic wear regime that implies high maintenance cost. At first tribometers were used in a laboratory study to investigate the relationships between wear and the emitted noise. Wear transitions from mild to severe wear were always accompanied by an increase in sound pressure of about 10 dB. The transitions also changed the sound pressure amplitude distribution from a narrow banded to a broader banded distribution. Secondly a full scale test in a small radius curve in a depot was carried out using a metro train, type C20. In agreement with the laboratory tests, the same kind of transfer from mild to severe wear was identified on the full scale tests in the depot. In addition, the sound pressure changed significantly, both in amplitude and in distribution, when transferring from mild to severe wear. By comparing the noise from the inner wheel-rail contact to noise from the outer wheel-rail contact a wear detection parameter for the outer wheel-rail contact is suggested. The third part of this project involves validation of the maintenance tool by operating the instrumented train in normal metro traffic, while at the same time collecting wear particles and making replicate casts of the rail at critical locations in the metro. Further comparison with weather data and a maintenance log has also been performed.
11.	Johansson, C., et al. (författare) Preliminary dynamic assessment of railway bridges subject to higher speeds 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract Swedish authorities have begun investigating the consequence of upgrading three of their major railway lines from 200 km/h to 250 km/h. The total track length is more than 1200 km and covers over 1000 bridges. Obviously, it is only possible to perform finite element analysis for a limited number of bridges for which the dynamic effects are considered to be a problem. Thus, as a consequence of the large number of bridges, a more efficient assessment approach has to be developed. The project initiated exemplifies the way in which a simple model may be used to help select a suitable bridge type or to identify existing bridges with dynamical problem so that they can be further assessed. This paper presents design curves to calculate the maximum acceleration in multi-span bridges.
12.	Krajnovic, Sinisa, 1970, et al. (författare) Aerodynamic Shape Optimization of High-Speed Trains 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract The paper presents a new, fully automatic multi-objective shape optimization method for improving the aerodynamic properties of trains. The optimization method was applied to a multi-objective optimization problem of crosswind stability of a train placed on an embankment. The train was optimized with two objective functions and the geometry was changed according to two design parameters. Furthermore, two flow scenarios were used in the optimization where the train was placed either on the windward or the leeward side of the two-track embankment. The optimization resulted in an optimal shape of the train which was the same regardless of the train's location on the embankment. The present approach is shown to be robust and capable of obtaining an optimal design of the train without the influence of the user during the optimization process. The example of the optimization problem presented in this paper was multi-objective but one objective was chosen to be the dominant one. Although there are no limitations in the number of design parameters or objective functions in the method developed, an increase in the number of parameters will result in an increase in the computational effort required for the optimization. An interesting result of the present work is that almost identical optimal shapes for the train were obtained for both trains traveling on the windward and the leeward sides of the embankment. This is a desirable outcome of the optimization as it does not require selecting the shape that is optimal for only one operational condition of the train.
13.	Krajnovic, Sinisa, 1970, et al. (författare) Large Eddy Simulation of the Flow around a Simplified Train Moving through a Crosswind Flow 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract This paper presents the results from large eddy simulation (LES) of the flow around a simplified train model moving through a crosswind flow. The results are compared with the experimental data from previous experimental study by Suzuki et al. [1] who used a model train with 1/60 scale that was moved along a 4m linear guide rail placed in front of a wind tunnel nozzle. The train in the present numerical work is stationary and the influence of the train movement is simulated by changing the boundary conditions. In addition to the simulation of the flow around the moving model, another simulation of the flow around a steady model influenced by the maximum crosswind from the moving case was made and the results are compared with the moving case. Comparison of the LES results with the experimental data from [1] showed good agreement proving that LES is capable of accurately predicting the dynamic change of the aerodynamic coefficients caused by the motion of the model through the wind profile. The aerodynamic moments and forces are computed and the results from the dynamic and the steady case were compared. Overshoots in several aerodynamic coefficients of the moving case over the steady case were observed. The yawing moment coefficient displayed an overshoot of some 30% indicating the importance of performing the dynamic tests for the purpose of satisfying the safety conditions. The large difference between the front and the rear part of the body in the distribution of the flow structures attached to the lee side of the body were found to cause the overshoot in the yawing moment signal during the dynamic case simulations. The instantaneous trailing vortices responsible for much of the aerodynamic stability of the vehicle when it enters the crosswind region were analysed. Several differences between the trailing vortices resulting from the dynamic and the steady cases were observed. These flow structures were found have a shape that changed during the cross flow passage. During their evolution, some of them obtained, for some time instances, the shape of the vortices in the steady case while other (such as the trailing vortex around the lower front edge) never reached exactly the same shape of the structure as in the steady case.
14.	Krajnovic, Sinisa, 1970 (författare) Unsteady simulations in train aerodynamics 2014 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 104 Tidskriftsartikel (refereegranskat)abstract This paper presents the present status of unsteady simulations in train aerodynamics. The approaches range from large-eddy simulation, hybrid RANS-LES in the form of detached-eddy simulations and partially-averaged Navier-Stokes to unsteady Reynolds-averaged Navier-Stokes. Use of a hybrid technique called partially-averaged Navier-Stokes is discussed. Applications of different techniques are illustrated with examples from predictions of flows around generic train vehicles. Numerical prediction of crosswind stability and flow control of train-like vehicles is discussed.
15.	Lacanna, Giuseppe, 1983, et al. (författare) The Reality of BIM Implementation in European Design Practice 2015 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 108 Tidskriftsartikel (refereegranskat)abstract Engaging in the BIM experience as a whole is much harder than is usually believed. Adopting a BIM approach, encompasses a change of management policy within the structure of the practices involved in the process. Having a clear organisational structure supports the efficiency of the communication. It affects its success. Very little research has been conducted on effective BIM implementation. This paper established the nature of BIM implementation. Eleven crucial issues worldwide provide the basis for the statistically controlled survey conducted across some of the biggest North-western European architectural practices, known to be BIM advocates and operating in the healthcare industry. The level of BIM implementation, based on eleven independent variables and their single implementation, proves to be below the level stated by the companies observed. The acronym BIM should not be synonymous with marketing campaigns. The outcomes of the study, presented in this paper, provide an opportunity to critically reflect on the requirements needed to reach an efficient level of implementation of the BIM platform in architectural practices. A clear organisational structure of the design team with a BIM manager that only acts as a coordinator among the overall design team, as well as the different external stakeholders involved in the BIM platform is highly recommended.
16.	Liu, Hailong, et al. (författare) A pin-on-disc study of airborne wear particles from dry sliding wheel-rail contacts 2016 Ingår i: Civil-Comp Proceedings. - : Civil-comp press. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract Pin-on-disc laboratory tests were carried out to identify the generation of airborne wear particles in wheel-rail contacts under different sliding velocities. The results show that the sliding velocity significantly influences both the number and size distribution of airborne wear particles. A comparison of the contact temperature was obtained during tests. For tests with high sliding velocities (1.2 and 3.4 m/s), the particle number concentration level was related to the elevated contact temperature in selected time intervals. Moreover, morphological and elemental analyses of collected particles and pin worn surfaces were studied by using a scanning electron microscope and field emission-scanning electron microscope. The data suggests that the oxide layers were detected within the pin's worn surfaces and an abundant presence of iron-oxide containing particles was observed. Therefore, it can be concluded that abundant fine and ultrafine airborne particles are more likely to be produced from an oxidative wear process in a wheel-rail contact under high sliding velocities.
17.	Lundén, Roger, 1949, et al. (författare) The influence of corrugation on frictional stress at the rail-wheel interface 2016 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract The influence of rail and wheel corrugation on vertical and tractive forces is studied, in this paper, for high-speed trains with the aim of evaluating the risk for surface initiated rolling contact fatigue (RCF). A train-track interaction model for vertical dynamics, which accounts for a prescribed torque on the wheelset and for the highfrequency content of the induced force spectrum, is employed. Corrugation distributions according to ISO 3095 (smooth rail) and as obtained from field measurements (corrugated rail) are considered. A parametric study is carried out in which level of corrugation, tractive effort and vehicle speed are varied. Also the influences of axle load and unsprung mass are investigated. The results are interpreted in terms of rolling contact fatigue impact spectra and by using the Tgamma energy model. If is found that the two models give similar tendencies regarding the surface initiated RCF impact. As expected, the traction effort will dominate the development of RCF, but significant influences are also found for corrugation, speed, axle load and unsprung mass.
18.	Lyu, Yezhe, et al. (författare) The effect of Subzero temperature and snow on the tribology of wheel-rail contact 2016 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract The wheel-rail system operates in an open environment where the weather condition varies constantly. In this laboratory study, an investigation using a pin-on-disc tribometer placed in a temperature-controlled room was conducted to examine the effect of subzero temperature and snow on friction and wear at the wheel-rail contact. In temperature range from 3 to-15 °C (without snow) friction and wear were dominated by low temperature brittleness, which led to an increase in friction and wear. When temperature decreased down to-25 °C, an ice layer condensed on the pin and disc surfaces, which then melted during sliding and acted as a lubricant, leading to the sharp decrease of friction and wear. When snow crystals were added into the contact they melted into water droplets during sliding because of pressure melting and reduced the friction and wear following the boundary lubrication mechanism. With increasing temperature from-25 to 3 °C, friction performed monotonously decreasing because of the increasing thickness of the water layer. A large area of oxide flakes generated on the worn surfaces also significantly protected the contacting wheels and rails from severe wear.
19.	Mousavi Bideleh Seyed, Milad, 1985, et al. (författare) Application of Semi-Active Control Strategies in Bogie Primary Suspension System 2014 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 104 Tidskriftsartikel (refereegranskat)abstract Primary suspension components of high speed train bogies can affect the vehicle's performance from different points of view, such as wear reduction and increasing forward speed to decrease track access charges. Various types of suspension components, as well as several control techniques, have been developed to amend the cost efficiency of railway operation; with respect to speed, wear, ride comfort, and safety. In the current study, the research overview is laid out with focus on the state-of-the-art, introducing semi-active technology for primary suspension of a bogie for high speed trains. The dynamic behaviour of a one car vehicle model developed in SIMPACK running on various operational scenarios including tangent and curved tracks is considered. The focus is to investigate the effects of passive and different semi-active control strategies on wear. For the passive case, an optimization problem is formulated to find the values of design parameters that guarantee minimum wear in system, while safety and comfort are taken as thresholds. Primary longitudinal and lateral stiffness as well as the primary suspension damper characteristics are chosen as design parameters and genetic algorithm based optimization routine in MATLAB is employed to solve the optimization problems. The attained optimized suspension parameters are applied in a one car railway vehicle model that is developed to be used as a reference case for comparison for the semi-active vibration control techniques. Application of magnetorheological (MR) dampers in the bogie's primary suspension, integrated with several semi-active on-off control strategies, is investigated. The outcomes of this research can amend the cost efficiency of railway operation (especially reduce wear) and give some hints for the design process of adaptive bogies.
20.	Muld, Toma. W., et al. (författare) Mode decomposition of flow structures in the wake of two high-speed trains 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract Two different train geometries, the Aerodynamic Train Model (ATM) and the CRH1, are studied in order to compare the flow structures in the wake. The flow is simulated with Detached Eddy-Simulation and then decomposed into modes with Proper Orthogonal Decomposition. This study has found that the flow structures are indeed different for the two train models although the tails are rather similar. For the CRH1 the dominant flow structures twist one of the counter-rotating vortices and leaves the other straight. The convergence of the modes are investigated and it is shown that approximately the same number of snapshots are needed for both trains.
21.	Muñoz-Paniagua, J., et al. (författare) Aerodynamic optimization of the ICE 2 high-speed train nose using a genetic algorithm and metamodels 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract © Civil-Comp Press, 2012. An aerodynamic optimization of the ICE 2 high-speed train nose in term of front wind action sensitivity is carried out in this paper. The nose is parametrically defined by Bézier Curves, and a three-dimensional representation of the nose is obtained using thirty one design variables. This implies a more complete parametrization, allowing the representation of a real model. In order to perform this study a genetic algorithm (GA) is used. Using a GA involves a large number of evaluations before finding such optimal. Hence it is proposed the use of metamodels or surrogate models to replace Navier-Stokes solver and speed up the optimization process. Adaptive sampling is considered to optimize surrogate model fitting and minimize computational cost when dealing with a very large number of design parameters. The paper introduces the feasibility of using GA in combination with metamodels for real high-speed train geometry optimization.
22.	Okhovat, Reza, 1984, et al. (författare) Dynamic equations for a spherical shell 2012 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 99 Tidskriftsartikel (refereegranskat)abstract Using a series expansion technique together with recursion relations the dynamic equations for an elastic spherical shell are derived. The starting point is an expansion of the displacement components into power series in the thickness direction relative the mid-surface of the shell. The three-dimensional elastodynamic equations yield recursion relations among these that can be used to eliminate all but the six of lowest order. The boundary conditions on the surfaces of the shell then give the shell equations as a power series in the thickness that can in principle be truncated to any order. The method is believed to asymptotically exact to any order. Comparisons are made with correct three-dimensional theory and other shell theories.
23.	Okhovat, Reza, 1984, et al. (författare) Dynamic equations for an anisotropic cylindrical shell using a power series method 2014 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 106 Tidskriftsartikel (refereegranskat)abstract The dynamic equations for a thin cylindrical shell made of a homogeneous, but transversely isotropic material are derived. First the displacement components are expanded in a power series in the thickness coordinate direction (around the mid-surface of the shell). The recursion relations are obtained among the expansion functions by inserting the aforementioned expansions into the three-dimensional elastodynamic equations. These recursion relations can be used to express all higher-order expansion functions in terms of the six lowest-order ones. The power series expansions of the displacement components are inserted into the stress-free boundary conditions on the two cylindrical surfaces of the shell leading to six power series in the shell thickness. Eliminating all but the six lowest-order expansion functions with the help of the recursion relations finally gives six dynamic equations for the shell. To investigate the properties of the resulting shell equations the eigenfrequencies for the transversely isotropic cylindrical shell are computed for a simply supported shell. Comparisons are made with exact three-dimensional calculations and membrane theory for some simple cases. The calculated eigenfrequencies for the shell equations agree very well with exact three-dimensional theory when the order of the shell equations is increased. © Civil-Comp Press, 2014.
24.	Pieringer, Astrid, 1979, et al. (författare) Curve squeal of rail vehicles: Linear stability analysis and non-linear time-domain simulation 2016 Ingår i: Civil-Comp Proceedings. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract Railway curve squeal arises from self-excited vibrations during curving. In this paper, a combination of a frequency-and a time-domain approach for curve squeal is applied in order to compare and evaluate the two different approaches. In the frequency-domain, linear stability is investigated through complex eigenvalue analysis. The time-domain model is based on a Green's functions approach and uses a convolution procedure to obtain the system response. To ensure comparability, the same submodels are implemented in both squeal models. The wheel model includes a single flexible wheel and accounts for inertia effects due to rotation adopting Eulerian coordinates. The track is modelled using the moving element method technique corresponding to a finite element mesh that travels with the vehicle speed. Coulomb's law with a constant friction coefficient is applied to model the local friction characteristics in the contact zone. The frictional instability arises due to geometrical coupling. The rolling contact model applied is Kalker's variational method in the time domain and a linearized version of this method in the frequency domain. Conditions similar to those of a curve on the Stockholm metro exposed to severe curve squeal are studied with both squeal models. The influence of the wheel-rail friction coefficient and the direction of the resulting creep force on the occurrence of squeal is investigated for vanishing train speed. The results of both models show similar tendencies, but differ in the predicted squeal frequencies.
25.	White, B. T., et al. (författare) The contribution of iron oxides to the wet-rail phenomenon 2016 Ingår i: Civil-Comp Proceedings. - Stirlingshire, Scotland : Civil-Comp Press. - 1759-3433. ; 110 Tidskriftsartikel (refereegranskat)abstract This paper reviews the current literature regarding iron oxide formation in the wheel-rail contact in order to assess the possible role of iron oxides in the "Wet-Rail" phenomenon, which causes low adhesion between the wheel and the rail. The paper discusses the structure and formation of oxides from a chemical perspective before analysing the direct tribological effects and outlining the techniques that have been used to study the oxide layers. This paper also suggests how knowledge of the subject could be expanded and how further understanding of the "Wet-Rail" phenomenon could lead to better mitigation methods, resulting in both economic and safety benefits.
26.	Zhu, Yi, et al. (författare) A field test study of leaf contamination on railhead surfaces 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Tidskriftsartikel (refereegranskat)abstract Leaves on train tracks cause low adhesion between wheels and rails, especially in the autumn. A Stockholm local traffic track with a long history of adhesion problems was subject to field tests of railhead contamination. Over a year, on five occasions under different conditions, the friction coefficient was measured using a hand-push tribometer and rail samples were taken. ESCA and GD-OES analyses were conducted to determine the composition of the top layer of rail contaminants. The blackish layer contains much higher contents of calcium, carbon, and nitrogen than other samples indicating a chemical reaction occurring from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer predicts the friction coefficient and leaf contamination extent.
27.	Östh, Jan, 1985, et al. (författare) Large Eddy Simulation of the Flow around one Single-Stacked Container Freight Wagon 2012 Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98 Konferensbidrag (refereegranskat)abstract In this work a time-dependent numerical simulation of the flow around a single stand-ing container wagon model is presented. The model consists of a 11.8m long con-tainer placed on the wagon. The model includes some geometrical details such aswheels and other undercarriage roughness. The Reynolds number in the study is 100,000based on the width of the container. The simulation method used is the Large EddySimulation technique. The forces and the flow field are averaged in time and the re-sults thereof are presented in the paper.

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