concepts and cri riteria towards a 0-deaths str trategy The finite - - PowerPoint PPT Presentation

Road safety th through FEM sim imulations: concepts and cri riteria towards a 0-deaths str trategy

The finite element methods in the road accident reconstruction

• Phd. Eng. Monica Meocci

September, 18 - 2019

Objectives: Reconstruct, after the event, the dynamics of the accident in order to determine the pre-collision parametres: 1) Velocity of the vehicles involved in the occurrence; 2) Trajectors of the vehicles involved in the occurrence; 3) Injury level; 4) Responsability in the causation of the event.

Accident reconstruction

23/09/2019 FEM in Accident Reconstruction

ROAD HOMICIDE

Main methods

23/09/2019 FEM in Accident Reconstruction

Semi-empirical methods

allows the determination of the speed pre-collision by means of equations obtained from experimental data i.e. full scale crash test, real events with camera, laboratory analysis Vehicle-pedestrian collision

Vehicle-pedestrian collision

23/09/2019 FEM in Accident Reconstruction

𝑊 = 𝑙 𝑒

km/h m Appel Happer Wood Input data: throw distance

Distance between the collision point and the final position of pedestrian hit

23/09/2019 FEM in Accident Reconstruction

Vehicle-pedestrian collision

𝑊 = 13,3 𝑒 − 4,5

Main methods

23/09/2019 FEM in Accident Reconstruction

Matemathical models

Results obtained consequently the evaluation of the physical model representing the real phenomenon i.e. physical formulations Vehicle-pedestrian collision

Main methods

23/09/2019 FEM in Accident Reconstruction

Ballistic motion

h S g S V

x x

    tan cos 2 /

h = height difference between launch and landing point Sx= horizontal distance  = starting angle

Allow to:

Evaluate all parametres but…It is necessary to know: Boundary condition … both velocities and directions (or hypothesis) For example

23/09/2019 FEM in Accident Reconstruction

Reconstruction by FEM

Results:

Damages Throw distance

23/09/2019 FEM in Accident Reconstruction

Reconstruction by FEM

EES

Results:

Damages Throw distance

23/09/2019 FEM in Accident Reconstruction

Reconstruction by FEM

Main methods

23/09/2019 FEM in Accident Reconstruction

Conservation of momentum – 2 DoF

X and Y coordinates allow to define the position of the vehicle

) ( ) ( ) ( ) ( ) cos( ) cos( ) cos( ) cos(

2 2 2 1 1 1 2 2 2 1 1 1 2 2 2 1 1 1 2 2 2 1 1 1

        sen V m sen V m sen V m sen V m V m V m V m V m      

2 1

e V V

2 1 2 1 2 1

, , , , ,     V V

Between two (or more vehicle)

Input: known parametres Results of the system

Main methods

23/09/2019 FEM in Accident Reconstruction

Conservation of momentum – 3 DoF X, Y and angle allow to define the position of the vehicle

2 1 2 1

, , ,   V V

Between two (or more vehicle)

Input: known parametres Results of the system

8 different equations

23/09/2019 FEM in Accident Reconstruction

When???

The main examples can be summarized follow:

• Vehicle rollower;
• Definition the position of the occupants;
• Collision with road restraint systems (definition of the energy

dissipation)

• ..in the other cases the methodology can be applayed with an improve
• f computational cost if compared ofthe traditional methods.

…when the problem can’t be represented in 2 dimension

23/09/2019 FEM in Accident Reconstruction

When???

The main examples can be summarized follow:

• Vehicle rollover;
• Definition the position of the occupants;
• Collision with road restraint systems (definition of the energy

dissipation)  ..in the other cases the methodology can be applayed with an improve

• f computational cost if compared with traditional methods.

…when the problem can’t be represented in 2 dimension

23/09/2019 FEM in Accident Reconstruction

When???

Rollover

23/09/2019 FEM in Accident Reconstruction

When???

Occupant’ position

23/09/2019 FEM in Accident Reconstruction

When???

23/09/2019 FEM in Accident Reconstruction

When???

Road restraint system collision

23/09/2019 FEM in Accident Reconstruction

When???

Road restraint system collision

23/09/2019 FEM in Accident Reconstruction

Severity of the collision