analysis of the influence of driving dynamic parameters on tire marks

Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011

Analysis of the Influence of Driving Dynamic Parameters on Tire Marks

Gunther Seipel, Prof. Dr. Hermann Winner, TU Darmstadt

Dr. Frank Baumann, Ralf Hermanutz, Daimler AG


2

Overview

Motivation

Objectives and Methodology

Model for the Emergence of Tire Marks

Influencing Driving Dynamic Parameters

Experimental Results

Further Steps

Summary and Outlook


3

Tire marks are of particular importance to clarify the circumstances leading to an accident

Tire marks are of particular importance to clarify the circumstances leading to an accident

Motivation

Tire Marks in Accident Reconstruction

Tire marks provide evidence regarding

Amount of speed reduction

Trajectory of vehicles

Place of collision

Curving speed

Vehicle defects

…

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Motivation

Changes in Tire Mark Characteristics due to Changes inChanges in Tire Mark Characteristics due to Changes in

Tires Wider Dimensions New Types (e.g. RoF, Low Rolling Resistance)

Tires Wider Dimensions New Types (e.g. RoF, Low Rolling Resistance)

Chassis Control Systems Improvements of ABS New Systems (e.g. ESP) …

Chassis Control Systems Improvements of ABS New Systems (e.g. ESP) …

Chassis Weights Suspension …

Chassis Weights Suspension …

Validity of Application of Conventional Reconstruction MethodsValidity of Application of Conventional Reconstruction Methods

Main Questions

Under which conditions do tire marks occur?

How do driving dynamics parameters influence the visibility of tire marks?

How do different types of tires affect the emergence of tire marks?


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Objectives

TireTire RoadRoad

Tire MarkTire MarkFocus of Research

External ForcesExternal Forces

Tire Speed, Longitudinal and Lateral SlipsTire Speed, Longitudinal and Lateral Slips

Tire ForcesTire Forces Evaluation of the influence of superior processes by analysis of influence of basic driving dynamic parameters


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Methodology

Top-Down Approach

Model of Fundamental Mechanisms for

Emergence of Tire Marks

Model of Fundamental Mechanisms for

Emergence of Tire Marks

Identification of Relevant Driving Dynamic

Parameters

Identification of Relevant Driving Dynamic

Parameters

Experimental Analysis of Parameters on a Mono-

Wheel

Experimental Analysis of Parameters on a Mono-

Wheel

Transfer of Results on Passenger Car

Transfer of Results on Passenger Car

Fzvx


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General Assumption of Two Main Mechanisms:

Abrasive tire wear due to sliding friction (tire side)

Bleeding of bitumen due to frictional heating (road Side)

Tire PropertiesTire Properties

Road PropertiesRoad Properties

Tire Mark IntensityTire Mark Intensity

γγ

Tire HeatingTire Heating

vv

Road HeatingRoad Heating

Tire Side

Road Sidefor asphalt roads

*WV

*BitumenV

*FE

Friction energy per length is of key significance for the emergence of tire marks!


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Calculation of Friction Energy per Length

Assumptions:

Friction in the contact patch between tire and road surface occurs only for sliding friction

λ

µ

µmax

0 % 100 %

µslide

µ=cλ ∙λ

µ-λ-curve

deformation slip area

slide slip area

2

2res

c

c

2 2

,

x yresd res

res

µ µµ

c c

2 2 2

2, ,

x y

s res res d res

µ µc

c c


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Calculation of Friction Energy per Length

Assumptions:

Friction energy per length is the product of the resulting friction force and the resulting friction path per travelled distance

Resulting Friction path between tire and road per travelled distance is equal to the resulting slide slip

2 2 2

* 2 2 2, ,

x y

F F res s res z x y

µ µcE F F µ µ

c c


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Identification of Relevant Driving Dynamic Parameters

Wheel load, longitudinal slip and slide slip angle determine the amount of friction energy per length

Hypotheses:

1. No tire marks occur for pure deformation slip, i.e.

2. The intensity of a tire mark increases with increasing friction energy per length (under constant boundary conditions)

3. The intensity of a tire mark depends on the amount of friction energy per length independent of the varying parameter

2 2 2

* 2 2 2 x y

F z x y

µ µcE F µ µ

c c

* 0FE


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Experimental Analysis

Testing Tool

Tire Measurement Trailer PETRA (Personen-wagen-Reifen-Traktions-Messanhänger)

Originally built for the µ-slip-analysis of car and light truck tires with varying:

Tire types

Pavement textures and intermediate mediums

Speeds

Wheel loads

Longitudinal and lateral slips

Camber angles


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Tire Measurement Trailer PETRA

Components

Regulator (hidden)

Measurement wheel

Oil cooler

Reference wheel

Hydraulic pump (hidden)

Gearbox (hidden)

Accumulator

Correvit sensor

Hydraulic tankAnalyzer unit

Slip angle adjustment


IR temperature sensor

Measuring rim


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Regulator

Measurement wheel

Gearbox

Cooler

Reference wheel

Hydraulic axial piston pump

Proportional valve

stationary working points

transponed

µ-λ-curve characteristic pump curve


Tire Measurement Trailer PETRA

Functional principle Measurement wheel is linked to

axial piston pump via gearbox

Pump conveys oil against a regulator

Generated pump torque (by measurement wheel) depends on pump speed (=wheel speed via gearbox) and oil delivery volume

Oil delivery volume is adjusted using a proportional valve

Equilibrium of brake and pump torque leads to stationary working points with constant longitudinal slip


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Step Visisbility Characteristic

0 0 % No Mark recognizable

1 10 % Mark incomplete and/or very faint pronounced without supporting mark fragments

2 20 % Mark incomplete, clearly recognizable interval mark parts

3 30 % Mark complete and faint pronounced without supporting mark fragments

4 40 % Mark complete and faint pronounced, edge mark and/or interval mark parts support the recognizability

5 50 % Mark complete and moderate pronounced, edge mark and/or interval mark parts support the recognizability

6 60 % Mark complete, edge mark emphasized to incomplete, filling faint pronounced

7 70 % Mark complete, edge mark clearly emphasized, filling moderate pronounced

8 80 % Mark complete, edge mark clearly emphasized, filling pronounced

9 90 % Mark complete, edge mark not or hardly distinguishable from filling, filling much pronounced

10 100 % Mark complete, edge mark not distinguishable from filling, edge mark and filling very much pronounced


Assessment of Visibility

Subjective assessment of tire mark on a scale from 0 (no mark) to 10 (clearly recognizable)*

*Cf. Grandel, J., 1989


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Testing Ground

Former airfield with asphalt pavement


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Test Procedure

1. Generation of tire mark within a defined area

2. Marking and documentation of tire mark

PETRA


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0

10

20

30

40

50

60

70

80

90

100

0,00 100,00 200,00 300,00 400,00 500,00

Subj

ecti

veV

isib

ility

[%]

Friction Energy [J/m]

ContiEcoContact3 185/65 R 15

Variation λ (2 - 16 %)

Variation Fz (4,8 - 5,8 kN)

Variation α (-6 - 6 °)0

10

20

30

40

50

60

70

80

90

100

0,00 100,00 200,00 300,00 400,00 500,00

Subj

ecti

ve V

isib

ility

[%

]


Pirelli SOTTOZERO 225/45 R 17 (Winter)



Variation α (-6 - 6 °)


First Results No visible tire marks for pure deformation slip

Tires show increasing intensity with increasing friction energy

The amount of friction energy per intensity and beginning of visibility differs between different tire types


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0

10

20

30

40

50

60

70

80

90

100

0,00 100,00 200,00 300,00 400,00 500,00

Subj

ecti

veV

isib

ility

[%]


ContiEcoContact3 185/65 R 15



Variation α (-6 - 6 °)0

10

20

30

40

50

60

70

80

90

100

0,00 100,00 200,00 300,00 400,00 500,00

Subj

ecti

ve V

isib

ility

[%

]


Pirelli SOTTOZERO 225/45 R 17 (Winter)



Variation α (-6 - 6 °)


First Results Restrictions:

Large scattering of intensity values mainly due to subjective assessment of visibility and environmental influences (e.g. lighting conditions, angle of view, individual perception)

Tire marks for the same values of λ, α and Fz not always reproducible


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Further Steps

Requirements for Further Investigation

Development of an objective method for the assessment of tire mark intensity, which is robust against environmental influences

Development of a method to determine the “tire marking sensitivity” of different combinations of tire and road surface

Tire PropertiesTire Properties

Road PropertiesRoad Properties

Tire Mark IntensityTire Mark Intensity

γγ

Tire HeatingTire Heating

vv

Road HeatingRoad Heating

Tire Side

Road Sidefor asphalt roads

*WV

*BitumenV

*FE

Tire Marking Sensitivity


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Further Steps

Requirements for Further Investigation

Development of an objective method for the assessment of tire mark intensity, which is robust against environmental influences

Development of a method to determine the “tire marking sensitivity” of different combinations of tire and road surface

Approach: Determination of sensitivity with help of a mobile testing facility for tire tread elements which allows for indoor and outdoor use under very controlled conditions


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Possible Applications

Backward Calculation

Forward Calculation

Intensity of tire mark

(crash scene)

Tire marking sensitivity

Friction energy

Determination with mobile testing facility at crash scene

Calculation of friction energy

Tire marking sensitivity

Output parameters from driving dynamics Simulation

Beginning, intensity, …Visibility of tire

mark


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Summary and Outlook

A concrete model was presented showing the key significance of dissipated friction energy per length for the emergence of tire marks

Longitudinal slip, tire slip angle, and wheel load have been identified as relevant driving dynamic parameters, determining the amount of this energy

Experimental results basically agree with the model description

Results additionally show a high influence of tire and road specific properties (tire marking sensitivity) on the intensity, and environmental influences on its assessment

Requirements for further investigation:

Development of an objective and robust method for the assessment of tire mark intensity

Development of a method for the determination of the tire marking sensitivity of different tire/road combinations

analysis of the influence of driving dynamic parameters on tire marks

Documents

mark recognizable

mark fragments

mark incomplete andor

filling faint

filling moderate

variation fz

subjecti visibility