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NUMERICAL SIMULATION OF THE BIAXIAL WHEEL TEST

ZWARP Users Conference 2017 08.11.2017 Riccardo Möller Fraunhofer LBF, Darmstadt

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CONTACT

Dipl.-Ing. Riccardo Möller

Group manager Numerical System Analysis

Department Assemblies and Systems Division Structural Durability Fraunhofer Institute for Structural Durability and System Reliability LBF Bartningstr. 47, 64289 Darmstadt Phone: +49 6151 705-408 Mobil: +49 172-6935445 riccardo.moeller@lbf.fraunhofer.de

www.lbf.fraunhofer.de

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CONTENT

Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

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Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

CONTENT

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INTRODUCTION

Situation:

Physical tests on biaxial wheel test bench

Experiences in numerical simulation for various test bench application cases

Motivation: Improvements of the ZWARP

Accumulation of experiences

Identification of parameters which influence the results

Tasks:

Numerical model of LBF ZWARP

Including capable tire simulation model

Validation physical test vs. numerical test

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Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

CONTENT

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MBS MODEL OVERVIEW

Multibody simulation tool: MSC.ADAMS

Rigid parts, kinematic joints

Link for loading wheel assembly modelled with different level of detail

Rotating drum

Wheel assembly

Dampers (longitudinal and lateral)

Actuators (vertical and lateral, drum rotational movement)

Source of data:

CAD, measurements

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MBS MODEL KINEMATIC LINK

CAD Rigid

CAD/Beam Modal structure

CAD/FEA Modal structure

Kinematic link level of detail

Rigid formulation CAD

Flexible formulation

CAD Beam modal structure

CAD FEA modal structure

Flexible formulation:

Additional results: strain on link

Approximation of inertia/stiffness

Modelling effort

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MBS MODEL EXCITATION CONCEPT

Wheel assembly

Drum: revolution speed

Vertical / Lateral actuation: force / motion (input)

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MBS MODEL EXCITATION CONCEPT

Drum Vertical Lateral

Wheel assembly

Drum: revolution speed

Vertical / Lateral actuation: force / motion (input)

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MBS MODEL EXCITATION CONCEPT

Drum Vertical Lateral

Wheel assembly

Drum: revolution speed

Vertical / Lateral actuation: force / motion (input)

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MBS MODEL EXCITATION CONCEPT

Drum Vertical Lateral

Wheel assembly

Drum: revolution speed

Vertical / Lateral actuation: force / motion (input)

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MBS MODEL SENSOR APPLICATION FOR VALIDATION

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MBS MODEL TIRE MODEL | INTERFACE TO MBS TOOL GENERAL

Rim

Tire

Road

Force Torque

Kinematical Rigid Body State

Force Torque

Kinematical Rigid Body State

Mechanical interface

MBD solver supplies Rim (Road) kinematical state

Position

Orientation

Velocity

Angular velocity

MBD solver expects accumulated force and torque acting on rim center

Tire DOFs are hidden from MBD solver

Only accumulated entities are returned in standardized (STI) interface

Source: Fraunhofer ITWM

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MBS MODEL TIRE MODEL | STRUCTURAL MBD TIRE MODELS

Typ

ical

nu

mb

er

of

sim

ula

tio

ns Ty

pica

l com

pu

tatio

nal e

ffort

100

101

102

103 100

101

102

103

104

105

DOFs

Empirical

Frequency-based

Rigid ring

Emperical contact

Flexible belt

Brush-type contact

FEA

Handling

NVH

Active safety

Ride/Comfort

Durability

Crash

REPs

CDTire/

Realtime

CDTire/3D

CDTire

CDTire/MF++

CDTire/NVH

CDTire/Thermal

Source: Fraunhofer ITWM

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MBS MODEL TIRE MODEL | CDTIRE

Complete 3 D shell based model

FD shell discretization

Materialized belt + materialized sidewall

Functional layer modeling (accessible in pre-processing)

Brush type contact

Inflation pressure

Acts as a normal force to inner shell

Can change during simulation

Belt/Sidewall/Rim Contact

Belt Sidewall

Rim Source: Fraunhofer ITWM

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MBS MODEL TIRE MODEL | CDTIRE/3D

Functional layer modeling

Tread (brush type)

Cap ply

Belt 1

Belt 2

Carcass

Inner liner + matrix

Anisotropic material

Orthotropic layers

Kirchhoff-Love bending

Discrete cords

Condensed into one shell

In pre-processing

Using a 3-dimensional meta-model

2

1

9

3

8

9

8

1

2

3

Source: Fraunhofer ITWM

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MBS MODEL TIRE MODEL | ADVANTAGES

Complete materialized model of sidewall and belt

Physical modelling of all functional layers of a modern tire

Separation of geometry and material properties

Physical correct inflation pressure dependency no pressure dependency in parameters

Possibility to adapt wheel and tire configurations (rim width, tire size,…) without re-parameterization

Wider application range

Constructional approach for parameter identification

Source: Fraunhofer ITWM

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MBS MODEL TIRE/RIM MODEL

Typical model approach

Fx,Mx

Fz,Mz

Rim rigid body

Contact forces between tire and rim are summed

Resulting forces and torques are applied directly in the wheel center sufficient to represent to loading of the tire/rim assembly to the hub but no information about loading of rim itself

Additional required information (non-standard)

Each tire/rim contact force/torque: function of time sufficient to define the loading of the rim

Assumption: local deflection of the rim does not influence the dynamic loading

Fy,My

Picture of tire: Fraunhofer ITWM

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Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

CONTENT

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SIMULATION PROCESS STEP 1: MBS-SIMULATION

Frame Tire

CDTire

Excitation

measurement

comparison in validation phase

simulation

x y

z

Fxi (t), Fyi (t), Fzi (t), Mxi (t), Myi (t), Mzi (t)

i tire-rim contact nodes

Input for Step 2

CDTire

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SIMULATION PROCESS STEP 2: SIMULATION OF STRAIN ON THE WHEEL

CAD

FEA | Contact nodes including load distribution to surrounding mesh

Fxi (t), Fyi (t), Fzi (t), Mxi (t), Myi (t), Mzi (t)

i tire-rim contact nodes

FEA Input File Generator Matlab-Script

Output from Step 1

ABAQUS

- FEA solver input deck

- Time-depending quasi-static loads

Post-processing local strain

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Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

CONTENT

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RESULTS VALIDATION LOAD CASES

Excitation signal:

Drum speed:

Synthetic signals: 10, 20 and 93 km/h

Eurocycle: 93 km/h

Actuator forces

Synthetic test cycle

Pure vertical load

Vertical and horizontal load

Measured forces from physical test low pass filtered and applied to numerical model

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RESULTS ZWARP

Good correlation between test and simulation (FEA)

Differences, if high and lateral load add each other

Different load offsets on different load levels between BEAM and FEA simulation

Strain on spindle:

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RESULTS ZWARP

Strain on link:

Results for strain gauge 04 on kinematic link

Good correlation between test and simulation

Differences increases with increasing vertical load

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RESULTS WHEEL

Strain on Wheel – Strain Gauge 09

Strain on Wheel – Strain Gauge 10

Several strain gauges are applied on the rim

Signal characteristic and range for all strain gauges pretty good

Amplitudes for some strain gauges fits well (e.g. 09)

Results not yet sufficient for all strain gauges (e.g. 10)

Possible reason might be transfer of position/ orientation in regions with high strain gradient from physical test to FEA-mesh

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Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

CONTENT

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CONCLUSIONS

Advantages of a simulation model

Change of parameters

Generation of additional results

Possible application cases at Fraunhofer LBF?

Improvement of test benches: Identification of the influence of

drum (inner/outer)

wheel dimensions in relation to diameter of drum

boundary conditions (wheel, wheel-hub-assembly)

General understanding of our test benches ( numerical models)

Test parameter (initial estimation of CV / CH , camber angle)

Improvement of load profiles

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Introduction

Multibody simulation model (MBS model)

Simulation process

Results

Conclusions

Summary

CONTENT

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SUMMARY

MBS model of biaxial test bench created

Complex tire model CDTire (Fraunhofer ITWM) included

Process to estimate local strains on the rim in combination with tire simulation model established

First validation of model using simplified load cases performed

Simulation model will support the development of biaxial test benches and may be used to generate additional information

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Thank you for your attention!