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1

What does the "A" value in Crush represent?

The coefficient representing the beginning of plastic deformation.
A = (w)(b0)(b1)/gL
Units = Lbs/In

2

What does the "B" value in Crush represent?

The coefficient representing the stiffness of the vehicle structure.
B = (w)(b1)^2/gL
Units = Lbs/In

3

What does the "G" value in Crush represent?

The integration constant which represents the elastic work done to reach a force of "A." Energy dissipated before permanent damage, aka Restitution
G= A^2/2B
Units = Pounds

4

What methodologies calculate delta-V?

Crush and Momentum

5

When must the momentum along both the "x" and "y" axis be considered?

When two vehicles whose angles of engagement exceed 10 degrees

6

In angled collisions (when using momentum calculations), what are V-1 and V-2 entry and exit signs?

---Based on Heading Angle---
V-1 Entry = 0 degrees
V-2 Entry = Psi (pitch fork looking symbol)
V-1 Exit = Theta (O with line looking symbol)
V-2 Exit = Alpha (A"ish" looking symbol)

7

When does separation occur?

Occurs when the collision force of the impulse between the vehicles has stopped.

8

What is the Big Mother Rule?

Delta-V1/Delta V2 = W-2/W-1

9

Name the different collision types?

Collinear
Central
Central Collinear

10

What are the five basic pedestrian trajectories in frontal collisions?

Wrap, Forward Projection, Fender Vault, Roof Vault, Somersault

11

Describe the Forward Projection (Pedestrian Trajectory).

- Usually occurs with a smaller Ped and a normal sized vehicle or an adult Ped and a full size pickup or van.
- PDOF above COM of Ped (Ped COM below the hood line)
- Speed match-up likely
- The second most common Ped trajectory

12

Describe a Wrap pedestrian trajectory.

- The Ped's head and torso bend around the hood
- Ped's COM is above the hood line
- Ped's body contacts hood, windshield, A-pillar
- Usually a decelerating vehicle
- Close to speed match-up
- Most common Ped trajectory

13

Describe a Fender Vault pedestrian trajectory.

- Typically involves adults with normal sized vehicles
- With Braking Vehicles: Ped usually struck near corner of vehicle, wraps over fender, falls
- With Non-Braking Vehicles: Ped usually struck near corner of vehicle, slides up hood or fender to A-pillar. Vehicle then decels and causes Ped to fall. Rear wheels can hit head or legs

14

Describe a Roof Vault pedestrian trajectory.

- Usually high speeds
- Typically Ped's COM is higher than hood edge line
- Ped is lofted in the air, over the hood/roof
- Ped lands behind the vehicle but may strike roof or trunk
- Usually no braking

15

Describe a Somersault pedestrian trajectory

- Usually high speeds or contact with lower portion of the Ped's body
- Normally a decelerating vehicle
- Least common Ped trajectory

16

What are the three phases of impact for a Pedestrian collision?

1. Impact - The Ped is accelerated
2. Flight - W/Decel: Ped and vehicle may separate
W/No Decel: Ped may remain on vehicle
3. Sliding/Rolling/Tumbling: After impact and hitting ground, body tumbles, rolls, and slides to a stop

17

What does CRASH 3 stand for?

Calspan
Reconstruction
of
Accident
Speeds
on
Hihgways

18

When is Crush not validated (Hint: There are 9)?

1. Roll Over
2. Yielding fixed objects that break away
3. Impacts other than a horizontal impacts (+,- 15 degrees)
4. Severe over/under ride
5. Undercarriage damage
6. Large moving vehicles - Greater than 10,000 lbs
7. Easily moveable objects
8. Non-central collisions (i.e. sideswipe)
9. Multiple impacts to the same body area

19

What are the problems with Small vs. Large vehicles in momentum calculations?

- Determination of entry and exit angles
- Small errors in post-collision velocities can have substantial impact on the calculated pre-collision velocity of the smaller vehicles.
- A very small variance in entry/exit angle of the large vehicle can have substantial effect on the calculated pre-collision velocity of the smaller vehicle

20

What has an affect of the rollover threshold ?

- Load distribution and mass
- Suspension loading/unloading
- Tires
- Multiple Axles

21

What can be expected with motorcycles both wheel braking?

- A straight rear wheel tire friction mark is normally associated with both front and rear wheel braking
- The application of the front brake provides more stability during braking and yields maximum braking efficiency
- The front tire does not generally leave a TFM

22

What can be expected with motorcycles both wheel braking?

- A straight rear wheel tire friction mark is normally associated with both front and rear wheel braking
- The application of the front brake provides more stability during braking and yields maximum braking efficiency
- The front tire does not generally leave a TFM

23

What can be expected with motorcycles rear wheel only braking?

- Will normally leave a wavy TFM
- The locked rear wheel tire has used up all the available friction longitudinally, therefore, the tire has 100% slip laterally and will easily be influenced by the roadway contour/slope, weight shifts, steering input, etc.

24

What can be expected with motorcycles front wheel only braking?

- TFM will be dark, straight, and short
- Steering geometry will cause the motorcycle to quickly go down.

25

Big Rig Dynamics when locking the truck's front tires (steering axle)?

- Loss of steering
- Vehicle will remain directionally stable
- Jack-knife possible

26

Big Rig Dynamics when locking the truck's rear tires (drive axle)?

- Jack-knife will occur rapidly
- Generally irreversible

27

Big Rig Dynamics when locking the trailers tires?

- Trailer slowly swings out
-Generally is reversible if brakes are released

28

What are the causes of a jack-knife?

- Locking driver wheel of tractor but not trailer wheels
- Sharp steering input puts the tractor but not the trailer into a yaw
- During evasive maneuvers, trailer pushes out the tractor from behind
- Brake lag time and poor timing on brake application from individual wheels

29

Explain Entry and Exit angles

Entry = From just prior to first contact to first contact
Exit = From maximum engagement to separation

30

What is the Kinetic Energy equation?

KE = 1/2mv^2