1. 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. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 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. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 3 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 …… Pictures: http://www.unfallaufnahme.info

4. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 4 Motivation Changes 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 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?

5. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 5 Objectives Tire Road Tire Mark Focus of Research External Forces Tire Speed, Longitudinal and Lateral Slips Tire Forces  Evaluation of the influence of superior processes by analysis of influence of basic driving dynamic parameters

6. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 6 Methodology Top-Down Approach Model of Fundamental Mechanisms for Emergence of Tire Marks Identification of Relevant Driving Dynamic Parameters Experimental Analysis of Parameters on a Mono- Wheel Transfer of Results on Passenger Car

7. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 7 Model for the Emergence of Tire Marks 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 Properties Road Properties Tire Mark Intensity γ γ Tire Heating v v Road Heating Tire Side Road Side for asphalt roads Friction energy per length is of key significance for the emergence of tire marks!

8. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 8 Model for the Emergence of Tire Marks Calculation of Friction Energy per Length  Assumptions:  Friction in the contact patch between tire and road surface occurs only for sliding friction λ µ µ max 0 %100 % µ slide µ=c λ ∙λ µ-λ-curve deformation slip area slide slip area

9. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 9 Model for the Emergence of Tire Marks 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

10. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 10 Model for the Emergence of Tire Marks 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

11. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 11 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

12. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 12 Tire Measurement Trailer PETRA  Components Regulator (hidden) Measurement wheel Oil cooler Reference wheel Hydraulic pump (hidden) Gearbox (hidden) Accumulator Correvit sensor Hydraulic tank Analyzer unit Slip angle adjustment Experimental Analysis IR temperature sensor Measuring rim

13. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 13 Regulator Measurement wheel Gearbox Cooler Reference wheel Hydraulic axial piston pump Proportional valve stationary working points transponed µ-λ-curve characteristic pump curve Experimental Analysis 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

14. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 14 Experimental Analysis Assessment of Visibility  Subjective assessment of tire mark on a scale from 0 (no mark) to 10 (clearly recognizable)* *Cf. Grandel, J., 1989

15. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 15 Experimental Analysis Testing Ground  Former airfield with asphalt pavement

16. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 16 Experimental Analysis Test Procedure 1.Generation of tire mark within a defined area 2.Marking and documentation of tire mark PETRA

17. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 17 Experimental Analysis 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

18. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 18 Experimental Analysis 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 F z not always reproducible

19. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 19 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 Properties Road Properties Tire Mark Intensity γ γ Tire Heating v v Road Heating Tire Side Road Side for asphalt roads Tire Marking Sensitivity

20. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 20 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

21. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 21 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

22. Analysis of Tire Marks | Gunther Seipel | Tire Science and Technology Annual Meeting 2011, Akron | September 13-14, 2011 22 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