design of a high speed train using a multiphysical …...{influence on stability {influence on...

DESIGN OF A HIGH SPEED TRAIN USING A MULTIPHYSICAL

APPROACH

First BCAM International Workshop on Multiphysics, Multiscale and Optimization Problems

Bizkaia Technology Park (Derio), 7th June 2010

Aitor BerasarteTechnologies Management Area

Technology DivisionCAF



WHAT DO WE ANALYSE?

STRUCTURAL ANALYSIS

AERODYNAMICS

NOISE & VIBRATIONS

DYNAMICS

TRIBOLOGY



STRUCTURAL ANALYSIS

Different FEM analysisStatic linear / non-linear

Proof case assessmentFatigue: Goodman / Miner / Dang VanSub-modelingBolted joints and Interference fits

Thermal – Stress (wheels)Non-linear dynamic (crash)Linear dynamic (modal)Mechanisms and multibody dynamics



STRUCTURAL ANALYSIS

Main simulation toolsHyperMesh pre-processorAbaqus solver and post-processor



STRUCTURAL ANALYSIS

Modal FEAEigenvalue and eigenfrequency extraction

Based on structural FE modelRequires adding mass (finished vehicle condition)

Mass at heavy equipment CoGMass distribution by means of density increment

Requires considering substructure stiffening effectDepends on joining solution (rigid / flexible)Changes modal response, difficult to idealizeStructural eigenmode



STRUCTURAL ANALYSIS

Modal FEAFrequency response

Based on modal combination techniquesRequires modal damping to be defined

Frequency dependentUnknown until experimental modal test is performed



STRUCTURAL ANALYSIS

Crashworthiness FEAStructure collapse analysis provides

Reaction load / displacement curveEnergy / displacement curveSurvival space preservation assessmentDeformation analysis



STRUCTURAL ANALYSIS

Crashworthiness FEARequires material model definition → Difficulties

Real Stress – Strain curve (material tolerance)Stiffness loss at welded regions (aluminium alloys)Spotwelds → fail criteria

Very hardware demandingNeeds experimental correlation for validation



STRUCTURAL ANALYSIS

Thermal - Stress FEASequentially coupled thermal – stress analysisRequires knowledge of physical and mechanical properties related to temperature

Specific heatThermal conductivityThermal expansionStress - strain curveCreep behaviour

Film coefficients depend on geometry and wheel speedData can be obtained by means of CFD



STRUCTURAL ANALYSIS

Thermal - Stress FEABraked wheel analysisBrake – Traction sequence simulation



NOISE & VIBRATIONS

Main problem: NOISE PREDICTIONCurrent situation

High dependence on prototypes and tests on finished vehicles

TargetPrediction information feedback on early stage

Two types of problemsStructure-borne noiseAir-borne noise



Structure-borne noiseLow modal densityLow frequenciesWay to solve → FEM

Disadvantages of FEMHuge number of elements depending on the bandwidthHuge models (a complete train)

Sections can be definedInteraction with the rest of the elements not considered

Other equipment, seats, etc.Damping unknown

NOISE & VIBRATIONS



NOISE & VIBRATIONS

Air-borne noiseHigh modal densityHigh frequencies and bandwidthWay to solve → SEA

Disadvantages of SEADefinition of different materials and couplingsUncertaintyAccuracy



NOISE & VIBRATIONS

What about the mid-frequencies?Medium modal densityNeither FEM nor SEA suitable for this problemWay to solve → ?

No method has proven to be suitable for all frequenciesHybrid methods → They combine FEM and SEA



DYNAMICS

Studies performedModal analysisDynamic stabilityCurve equilibriumTime simulationsActive suspension designWheel profile designComfortGauge analysis

ToolIn-house Multi-body simulation (MBS) software



DYNAMICS

Multi-body model (MBS model)Bodies (rigid or flexible)

GeometryMass and CoGInertia

Connection elementsStiffness and damping elementsKinematical restrictionsActive control elements

Vehicle-track interactionWheel-rail contact

REAL SYSTEM EQUIVALENCE

MULTIBODY SIMULATION MODEL



Bodies High-speed trains → Flexible carbodyObjective

Represent the influence of carbody structural modes on vehicle dynamics behaviour

HowFEM modal analysis Input for MBS model

The more structural modes on the MBS modelThe more precisionThe higher computational cost

SolutionInfluence of modes >20Hz → Residual flexibility

DYNAMICS

REDUCTION



Influence on stability

Influence on running comfort

DYNAMICS

100 150 200 250 300 350 400 450 5000.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2INDICE CONFORT

Velocidad (Km/h)

N

Flexible CarbodyRigid Carbody

Direct influence of carbody flexibility

on vehicle dynamics



Suspension elementsFunction

Connect different bodiesEnsure good comfort and ride qualityProvide good stability

Types

Selection of suspension parametersCompromise between the different ride conditions

DYNAMICS

Linear Non-linear



Vehicle-track interactionTrack features → Excitation to the vehicle

Straight or curved trackReal track irregularities

Time domainFrequency domain

Simulation of specific irregularitiesAccurate modelling of wheel-rail contact needed

Cornerstone of vehicle running dynamicsSource of excitations

Tribology problems (wear prediction)Impact on life cycle costs

DYNAMICS

Wheel profile design

Wheel reprofiling



Vehicle-track interactionCurrent work lines

Wear predictionMultipoint contactTridimensional contact (flange contact at different plane)Coupling with traction and brakeLeft and right rail with different friction coefficientVariable friction coefficient as a function of contact position (flange lubrication)

DYNAMICS



AERODYNAMICS

Resistance to motionAerodynamic term has a great influence in high speedA proper CFD simulation is very challenging

Great level of geometry detail is requiredMany parameters have an influence

Nose designPantograph configurationInter-coach geometryBogie featuresEtc.



AERODYNAMICS

Crosswind issuesA safety requirementA well-established European methodology

Geometry characterizationDefined wind scenariosCoupling with real-time MBS simulations

ChallengesProper simulation of realityParametric optimization

Nose shapeRoof featuresEtc.



AERODYNAMICS

Open air phenomenaSafety issue for passengers on platforms and workers close to the track

Pressure effects are not a problem for simulationViscous effects and wake are difficult to simulate

Structural requirement for passing trains and infrastructure equipment

Input for FEM calculationsStatic valueLoad collectives



AERODYNAMICS

Tunnel phenomenaPressure variations

Many combinations possibleType of tunnel, type of trains, etc.

Tackled with CFD and 1-d simulationsInput for FEM calculations

Micro-pressure wave generated at the exit portalMany factors play a roleTransient CFD seems suitable

Portal (entry) Tunnel centre Portal (exit)

train

Emission of MPW



AERODYNAMICS

Ballast flyingInitiation

DynamicsIce dropAerodynamics (very important at high speeds)

ContinuationMainly aerodynamic

ChallengesProper simulation of the flow in the underbelly regionFlow-stones interactionMotion of stones and collision with other stones/elements



AERODYNAMICS

AeroacusticsAerodynamic contributes to

Structure-borne noiseFlow-structure interaction

Air-borne noiseFlow behaves as a noise source

Very challenging to simulateRefrigeration

Cooling of equipmentClimatic comfort of passengers



AERODYNAMICS

Aerodynamic designMany effectsMany variablesInteraction

Interaction withStructural designDynamicsNoise & vibrationsTribology (2nd order)

Optimization of designEnergy efficiency

Need for advanced design approach



GENERAL OVERVIEW

STRUCTURAL ANALYSIS

AERODYNAMICS

NOISE & VIBRATIONS

DYNAMICS

TRIBOLOGY



THANKS FOR YOUR KIND ATTENTION!!!

design of a high speed train using a multiphysical …...{influence on stability {influence on...

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