Crashworthiness Flashcards
Explain procedure of accident reconstruction.
Accident Reconstruction
• Data Collection / Accident Investigation
–Accident type, vehicles, injuries
–Gross motions of vehicles and occupants
• Reconstruction
–Calculate severity
–Detailed simulation of system dynamics
Name a crash parameter related to velocity.
Crash Parameters
• Delta V:
–is NOT the speed of impact
–described the speed change during a
crash phase
–has been a historical measure of accident
severity
Explain Delta-v.
Explain relation Delta-V and accelerations.
How is Delta-V selected in oblique crashes?
Explain Energy in relation to crashes.
Energy
• EBS / BEV / EES / ETS
– equivalent impact speed for a rigid barrier test
– Energy Absorbed in vehicle damage is expressed as an
equivalent speed
E= 1/2 MV2
V=EBS/BEV/EES/ETS
Which are the two approaches to estimate crash severity?
Crash Dynamics
• Two Approaches to estimate the crash severity
– Momentum
– Energy
What does succesful momentum analysis needs?
Successful Momentum analysis needs:
– Accurate scene evidence
– Vehicle Masses
– Pre-impact speed
What does succesful Energy analysis needs?
Successful Energy analysis needs:
– Vehicle Stiffness data
– limited crash speed range (20-70 km/h)
How is momentum reconstructions performed?
Momentum Reconstructions
• Scene information:
– Road conditions, weather, location, road geometry
– vehicle orientation at impact
• Vehicle position at rest and/or some pre-impact information
Which are the equations for impact?
How to solve for unknown v in momentum reconstructions?
The relationship between restitution and velocity?
What are the limitations with momentum reconstruction?
Explain background for the crash model.
Explain the energy approach.
Explain the Energy calculation.
Explain differences between direct and induced damage?
Explain the crushable zone.
Equations acceleration and velocity in crash tests?
Equations velocity and displacement vehicle crash tests.
Differences between restrained and unrestrained occupant on velocity/time charts?
Explain Force Deformation Characteristics.
Curve vehicle deceleration.
General structure of car?
Which are the load paths?
Explain phases of vehicle deceleration.
Vehicle deceleration force curves.
Detailed load paths?
Explain Estimation of structure force.
Explain the compromise of compatibility/aggressivity.
Compatibility/Aggressivity
• Vehicle structural response can be considered to consist of a
“compromise”
– Self Protection: Can the vehicle protect its own occupants?
– Aggressivity: Does the vehicle protect itself at the expense of
its collision partner?
Which are the Compatibility Categories?
Compatibility Categories
• Mass - What kinetic energy is involved?
• Stiffness - How strong is the structure?
• Structural Interaction - How does the structure respond with the
crash partner’s structures?
Explain the compatibility problem.
if the mass ratio of two colliding vehicles
is 2:1, how large is the fatality risk for occupants in the
smaller vehicles.
Explain Force Level Compatibility.
Explain Stiffness compatibility.
Describe Fixed Barrier Crash Test
Problem (1).
Explain Fixed Barrier Crash Test
Problem (2).
Describe the GS diagrams.
How to calculate vehicle stiffness?
Describe vehicle deceleration and deformation.
Describe Structural Interaction.
Structural Interaction
• Can the structures absorb the energy in an effective manner
• Self protection parameter
• Pole impacts, offset impacts
What will happen?
Explain the concept of alignment in car-to-car crash.
Explain C3 deformation for mis-aligned situations?
In frontal crashes, compatibility is influenced by:
In frontal crashes, compatibility is influenced by:
– Vehicle mass (which influences stiffness)
– Structural interaction
– Compartment strength is a prerequisite.
• Fixed barrier tests create mass dependency
• Vehicle “Stiffness” measured in barrier tests is not necessarily
the same in a vehicle-vehicle crash
How can we get vehicles to interact?
Explain physical deformable barrier.
Explain progressive deformable barrier.
Dimensions in Front and Side impact.
Explain challenges with side impact.
What are common injuries for side impact? What about restraints?
Explain ECER95.
Explain the moving deformable barrier
How is Delta-v defined?
Delta-v=v_after-v_before
Describe Side Impact Design.
Geometry for car in side structure.
Describe deformation mode in side impact.
Occupant kinematic behavior in side impact?
Velocity Time History Side Impact.
Displacement in Velocity-Time History.
Elaborate on Door Padding Side Impact.
Compatibility modes for side impact?
Most important notes on side impact.
Side Impact less sensitive to mass and stiffness
–Already huge difference in stiffness for front and
side structures
• Most critical issue is the geometry of the impacting
vehicle
–Important to not load high on the vehicle side
–Reduce intrusion and intrusion velocity on
occupant
Most common crash types?
Rear-crashes
Rear Impacts.
Rear Impacts
• The most common crash type producing injuries
• Not necessarily the most severe crash type encountered
– Relative speed at impact can be lower than travel speed of
striking vehicle
• Historic main feature for rear impact it protection of fuel system
Span of impact energies?
Describe Front Component Pedestrian Impact.
Describe Sensitivity to Bullet Mass.
