Dr Yan Sun - CQUniversity - Module 3: Suspension designs to optimize curving and hunting
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Dr Yan Sun - CQUniversity - Module 3: Suspension designs to optimize curving and hunting

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Dr Yan Sun delivered the presentation at 2014 RISSB Wheel Rail Interface Forum. ...

Dr Yan Sun delivered the presentation at 2014 RISSB Wheel Rail Interface Forum.

The RISSB Wheel Rail Interface Forum reviewed the fundamentals of what happens between wheel and rail before focusing on the practicalities of monitoring, interventions, maintenance, management and the critical importance of the interdisciplinary cooperation.

For more information about the event, please visit: http://www.informa.com.au/wheelrailinterface14

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Dr Yan Sun - CQUniversity - Module 3: Suspension designs to optimize curving and hunting Dr Yan Sun - CQUniversity - Module 3: Suspension designs to optimize curving and hunting Presentation Transcript

  • Suspension designs to optimise curving and hunting Dr. Yan Quan Sun, Centre for Railway Engineering, CQUniversity Tuesday 20 May 2014 Brisbane CENTRE FOR RAILWAY ENGINEERING Module 3 - Information about rail vehicle suspension design issues
  • Outline  Rail Vehicles – Passenger Cars & Wagons  Bogies & Suspensions  Principles for Selecting Suspension Parameters  Approaches for Preliminary Selection of Suspension Parameters  Simulation Modelling for Optimum Selection of Suspension Parameters  Closing Remarks CENTRE FOR RAILWAY ENGINEERING
  • Rail Vehicles – Passenger Cars & Wagons  Rail vehicles are used to transport human beings and various types of cargo;  Rail vehicles referring to a vehicle car body with a pair of bogies are presented and discussed;  Rail vehicle consists of a number of components which, depending on the design and use, can include: • Car body; • Vehicle frame (underframe); CENTRE FOR RAILWAY ENGINEERING • Couplings & draft gear; • Bogies – unpowered bogies and powered bogies:  Bolster or bolsterless;  Suspension components;  Sideframes or bogie frame;  Wheelsets;  Brakes.
  • Rail Vehicles – Passenger Cars & Wagons CENTRE FOR RAILWAY ENGINEERING • Two types of wagons - heavy haul & freight wagons. Heavy haul wagon [1] Freight container wagon [1]
  • Rail Vehicles – Passenger Cars & Wagons CENTRE FOR RAILWAY ENGINEERING • Two kinds of passenger trains - older style long distance trains hauled by locomotives at the front & metropolitan or inter-city trains with powered bogies at the front and rear of the trains. Long haul passenger train [1] High sped passenger train [1]
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING • Bogies for wagons and passenger cars are typically as shown below: Three-piece bogie for freight wagons [1] Bogie for passenger cars [2]
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING The main functions are: • Transmission and equalisation of the vertical load from the wheels of the vehicle to the rails; • Guidance of vehicle along the track; • Control of the dynamic forces due to motion over track irregularities, in curves, switches and after impacts between the cars; • Efficient damping of excited oscillations; • Application of traction and braking forces.
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING For passenger bogies: • Wheelsets are generally mounted in a rigid H- shaped frame; • Primary suspensions (PS) – elastic elements connect axlebox to bogie frame (coil springs & dampers), transmit forces from wheelsets to bogie frame; • Secondary suspensions (SS) – elastic elements between bogie frame and vehicle body (air springs), transmit forces from bogie frame to car body; • The principal functions of PS are guidance of wheelsets on straight track and in curves, and isolation of the bogie frame from dynamic loads produced by track irregularities; • The SS provides the reduction of dynamic accelerations acting on the car body which determines passenger comfort.
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING Modern passenger bogie designs: • A smaller number of parts in the secondary suspension and thus reduced maintenance costs – flexi coil springs, air springs; • Bolsterless – car body directly mounts on secondary suspensions; • Equipped with separate secondary dampers to damp oscillations in vertical and lateral directions; • Yaw dampers are often fitted longitudinally between the body and bogie to damp hunting motion on straight track.
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING For wagon bogies: • The frame of a three-piece bogie consists of bolster and two sideframes, elastically connected by a coil spring and friction wedge-type secondary suspension (SS), which can resist asymmetrical loads and holds the bogie frame square in-plane; • Such SS allows independent pitch of sideframes when negotiating a large vertical irregularity on one rail, allowing bogie to safely negotiate relatively poor track; • SS consists of a set of nested coil springs and the wedge arrangement, providing friction damping in the vertical and lateral directions. Secondary suspension [1]
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING • There are two types of friction dampers - constant friction and variable friction dampers: Three-piece bogie friction wedge type dampers [1]
  • Bogies & Suspensions CENTRE FOR RAILWAY ENGINEERING • Clearances between adapter (or the axlebox) and sideframe in longitudinal and lateral directions, allow the wheelsets to move in curves and pass large horizontal irregularities; • Due to the absence of PS, such bogies have a large unsprung mass which causes increased track forces; • In curves, three-piece bogies demonstrate the “lozenging” or “warping” effect, when the two sideframes adopt a parallelogram position (in plan view); • In this instance, the wheelsets cannot adopt a radial position in the curve, and generate large angles of attack, leading to constant flange contact and causing high levels of wear. Clearances [2]
  • Principles for Selecting Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Understanding of Suspension Parameter Effect on Hunting & Curving • Massive investigations on this area began in the 1950s; • Early study showed that both lateral and yaw PS stiffnesses are increased, there being an optimum at which stability is a maximum; • With a careful choice of lateral suspension damping and lateral & longitudinal stiffnesses, it was possible to eliminate the low-speed body instability (a strongly contributory factor in wagon derailments) so that the vehicle operating speed was only limited by the wheelset instability; • The use of yaw relaxation dampers could provide sufficient flexibility at low frequencies in curves and sufficient elastic restraint at high frequencies to prevent wheelset instability; • The design of a two-axle vehicle with a purely elastic suspension requires a compromise between stability and curving; • When linear theories of the curving of railway vehicles became available it became possible for the first time to consider the best compromise between the requirements of stability and curving on a numerate basis; • Generally, to achieve high speeds the longitudinal stiffness of PS should be high, whereas the lateral stiffness may be lower to reduce dynamic force when negotiating lateral track irregularities.
  • Principles for Selecting Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Principles for Selection • The parameters of a rail vehicle may be considered optimal if its dynamic characteristics meet three groups of requirements:  There is sufficient reserve of critical speed with respect to design speed;  Ride quality, track forces, and safety factors satisfy the standards on straight track and in curves for the full range of operational speeds;  Wear rate of friction elements and wheel profiles is within acceptable limits. (the requirements are specified in many standards. (e.g., RISSB, Australia)) • How to achieve the optimal design of suspensions:  At the preliminary stage the suspension parameters can be estimated using simple engineering approaches;  To make sure that the parameters are optimised, further refinement is usually done using computer simulations.
  • Approaches for Preliminary Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING
  • Approaches for Preliminary Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Selecting Lateral and Longitudinal Primary Suspension Stiffness • Theoretical investigations and experiments show that wheelset stability increases with increasing stiffness of the connection to the bogie frame; • However, the character of this dependence is highly nonlinear and the relationship between suspension stiffness and the mass and conicity of the wheels influences the critical speed; • Increasing the longitudinal stiffness of the primary suspension impairs the guidance properties of the wheelset in curves, whilst increasing the lateral stiffness reduces the ability of the wheelset to safely negotiate large lateral irregularities.
  • Approaches for Preliminary Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Selecting Shear & Bending Stiffness • A fundamental conflict therefore exists between the requirements for high speed stability on straight track and good curving with safe negotiation of track irregularities; • For a preliminary choice of bogie lateral and longitudinal stiffness, a simplified approach providing the relationship between stiffness and ride quality in analytical or graphical form would be useful; • Two generalised parameters can be introduced to represent the primary suspension: 1. A stiffness corresponding to relative lateral displacement between the centres of wheelsets referred to as the shear stiffness (Ks); 2. A stiffness corresponding to the relative yaw angle between the wheelsets referred to as the bending stiffness (Kb). Shear & bending stiffness [2] where 2a = wheelset centres, and 2b = wheelset journal centres.
  • Approaches for Preliminary Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Selecting Shear & Bending Stiffness • Shear stiffness Ks has a greater influence on critical speed of vehicle, whilst bending stiffness Kb mainly determines wheelsets’ angles of attack in curves; • Solution of the stability problem shows that the critical speed of a conventional railway vehicle is a function of its shear and bending stiffness; • The quality of curving can be estimated using relationship of wear number (the sum of creep force power for all wheels of vehicle) to shear and bending stiffness. Ref. [2]
  • Approaches for Preliminary Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Selecting Suspension Damping • Damping is typically provided within the suspension by either friction or hydraulic devices; • The selection of the optimum damping levels is more complicated than the choice of suspension stiffness; • High levels of damping decrease the amplitudes of vibrations in resonances but significantly increase the accelerations acting on vehicle body for higher frequency inputs such as short wavelength track irregularities; • Considering the simplified case of linear dependence between the damper force and the velocity, the damping coefficient is defined as the ratio of the real part of the eigenvalue to the corresponding natural frequency: where [B], [M] are the damping and inertia matrices of the vehicle multi-body model, respectively,{vi} is the column-vector of ith eigenmode and ωi is the natural frequency of ith eigenmode; • Effective damping of vibrations of railway vehicles is typically obtained with damping coefficients which lie in the following ranges: 0.2 – 0.3 for vertical oscillations; 0.3 – 0.4 for horizontal oscillations, and 0.1 – 0.2 for vehicle body roll.
  • Approaches for Preliminary Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Selecting Suspension Damping • In freight bogies, friction dampers are commonly used. When making the preliminary choice of parameters, the friction force in the damper is estimated on the basis that the amplitude should not increase in the resonance case; • A relative friction coefficient is defined to be equal to the ratio of friction force to the static vertical load. For freight cars the recommended value of relative friction coefficient is typically in the range 0.05 – 0.15.
  • Simulation Modelling for Optimum Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING VAMPIRE • A VAMPIRE wagon modelling contains 11 masses (one wagon car body, two bolsters, four sideframes, and four wheelsets). The connections among these 11 masses have been modelled using 17 stiffness elements, 74 bumpstop elements, 13 viscous damper elements, 116 friction elements, and four shear spring elements, which fully consider the nonlinear characteristics of the connections. • There are some commercial software packages available for comprehensive rail vehicle modelling to conduct suspension designs for optimum curving and hunting, such as VAMPIRE, Gensys, NUCARS, Simpack, Adams/Rail, etc. • VAMPIRE and Gensys are available at CRE, CQU.
  • Simulation Modelling for Optimum Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING VAMPIRE • The natural frequencies of the wagon with loaded and empty condition are determined using VAMPIRE model. Loaded Car Body Bounce Mode (1.998 Hz) Loaded Car Body Pitch Mode (3.04 Hz) Empty Car Body Bounce Mode (5.373 Hz) Empty Car Body Pitch Mode (8.161 Hz) Vampire wagon model [3]
  • Simulation Modelling for Optimum Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Gensys Whole Wagon Bogie Bogie (Side View) Bogie (Front View) Gensys wagon model [4]
  • Simulation Modelling for Optimum Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Gensys • The wagon model includes 11 masses – one wagon car body, 2 bolsters, 4 sideframes and 4 wheelsets, which are modelled as rigid bodies; • The connections include centre bowl and side bearers between wagon car body and bolster, secondary suspensions between bolster and sideframes and primary suspensions between sideframe and wheelsets; • Each friction wedge is modelled as a massless block and the exact triangular shape is considered; • In the wheel-rail modelling, the Hertzian contact stiffness normal to the wheel-rail contact surface is defined. Three different contact surfaces can be in contact simultaneously. The calculations of creep forces are made in a lookup table calculated by Fastsim.
  • Simulation Modelling for Optimum Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Gensys • Hunting speed & curving analysis; • The determination of critical hunting speed is through simulation using a decreasing vehicle speed (e.g. from 200 or 300 km/h to 50 km/h) with an initial lateral disturbance; • The wheel-rail normal force and the L/V ratios during curving (radius = 300m with lateral geometry irregularities).
  • Simulation Modelling for Optimum Selection of Suspension Parameters CENTRE FOR RAILWAY ENGINEERING Gensys Determination of hunting speed [4] Simulation results during curving
  • CENTRE FOR RAILWAY ENGINEERING Closing Remarks • Only rail vehicles with a pair of bogies are covered, and the types and use of passenger vehicle and freight wagon are discussed; • The functions of their bogies & suspensions are described; • The design of suspension significantly affects rail vehicle stability and curving, requiring a compromise between them; • In order to achieve the optimal design of suspensions, the initial suspension parameters can be estimated using simple engineering approaches, and then the optimum selection is usually done by sensitivity analysis using computer simulation; • Finally, rail vehicle modelling using VAMPIRE and Gensys simulation programs are introduced and some simulation results are shown.
  • CENTRE FOR RAILWAY ENGINEERING References 1. M. Spiryagin, C. Cole, Y.Q. Sun, M. McClanachan, V. Spiryagin and T. McSweeney, Design and Simulation of Rail Vehicles, Ground Vehicle Engineering Series, CRC Press, 2014. ISBN 978-146-657-566-0. 2. Simon Iwnicki, Handbook of Railway Vehicle Dynamics, CRC Press, Taylor & Francis Group, 2006, ISBN 978-0-8493-3321-7 (Hardcover) 3. Y.Q. Sun, C. Cole and M. McClanachan, The calculation of wheel impact force due to the interaction between vehicle and a turnout, Proc. IMechE, Part F, Journal of Rail and Rapid Transit, Vol. 224, 2010, pp391-403. 4. Y.Q. Sun, M. Spiryagin, C. Cole and S. Simson, EFFECT OF WHEEL-RAIL CONTACTS AND TRACK GAUGE VARIATION ON HUNTING BEHAVIOURS OF AUSTRALIAN THREE-PIECE BOGIE WAGON. Proceedings of 23rd International Symposium on Dynamics of Vehicle on Roads and Tracks, Aug. 19th ~ 23rd, 2013, Qingdao, China.
  • CENTRE FOR RAILWAY ENGINEERING Thanks for Your Attention
  • CENTRE FOR RAILWAY ENGINEERING Discussion Questions • What are the main functions of bogie and suspension? What type of bogie & suspension is used in your company? • What are the principles for selection for the suspension parameters? Do you know the requirements in RISSB standard? • If you know the required natural bounce frequency is 2.5 Hz for loaded vehicle and 4 Hz for the empty, how to determine the static deflections of a suspension with linear characteristics? • If the shear & bending stiffnesses are selected, how to deduce the lateral and longitudinal stiffnesses of a primary suspension?