2. Fundamentals of Collision Damage4
Chapter
Fundamentals of Collision Damage

3. Objectives After studying this chapter, you will be able to:
Describe the various factors that will influence the way a vehicle will react in a collision.
Identify bends, body lines, and crowns.
Differentiate between direct and indirect damage.
Explain the bend-versus-kink rule.
Describe the types of collision damage found on full-frame and unibody vehicles.

4. Vehicle Design Factors
Influence way vehicle will react in collision
Metal properties
Grain pattern
Elasticity
Plasticity
Component shapes

5. Metal Properties (Grain Pattern)
Determines metal strength
Varies by steel type
Mild steel
Large, loose grain pattern
High-strength steel
Small, tight grain pattern

6. Metal Properties (Elasticity)
Ability of metal to bend without permanent deformation
Elastic deformation
Force applied to panel causes bend
Force removed, panel assumes undamaged shape

7. Metal Properties (Plasticity)
Ability of metal to be shaped
Plastic deformation
Force applied to panel causes a bend
Force removed, panel does not return to undamaged shape
Bend
Manufactured into part
Buckle
Caused by impact force

8. Component Shape Determines how panel responds to impact force
Work hardening
Rearrangement of metal grains
Find in bends and buckles
Makes metal stronger

9. Component Shape (Cont.)
Body line
Makes panel more rigid
Makes panel less likely to flex
Forms convolutions in unirails
Crown
Curvature in panel
Less severe bend than body line
Degree of curvature determines panel strength

10. Component Shape (Types of Crown)
Low crown
Almost flat
Will flex in and out
High crown
Highly curved
Rigid
Will not flex
Double crown
Curved in two directions
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11. Component Shape (Types of Crown, Cont.)
Reverse crown
Curved in, not out
Forms concave surface
Will not flex
Combination crown
Two or more crown types in one panel
Most body panels are combination crown

12. Collision Factors (Force)
Action between objects that changes their relative condition as to motion or rest
Weight multiplied by speed
Yield point
Minimum amount of force required to cause permanent change in grain arrangement

13. Collision Factors (Force, Cont.)
Longitudinal force
Force applied to one end of panel
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14. Collision Factors (Force, Cont.)
Lateral force
Force applied to side of panel
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15. Collision Factors (Force, Cont.)
Simple rolled buckle
Caused by longitudinal force
Found on panels without body lines
Collapsed hinge buckle
Found on panels with body line

16. Collision Factors (Force, Cont.)
Arrowhead
Caused by lateral force on high crown panels
Dent (low area)
Caused by force greater than yield point applied to panel

17. Collision Factors (Inertia)
Tendency of object to remain at rest or to remain in motion
Inertia damage
Buckles in panels
Caused by one part of vehicle stopping while another portion of vehicle remains in motion for instant

18. Collision Factors (Inertia, Cont.)
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19. Collision Factors (Target)
Object with which vehicle collides
May be hard or soft
May be movable or unmovable

20. Collision Factors (Impact Angle)
Orientation of vehicle and target at moment of contact
Greater damage closer to vehicle center
May cause target to spin

21. Collision Factors (Surface Area of Impact)
Area collision force is spread across
Large area vs. small area

22. Collision Factors (Vehicle Height)
Vertical position of vehicle and target at moment of contact
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23. Damage Force applied to vehicle may cause damage
May travel through entire vehicle, causing damage away from point of impact
Direct and indirect damage
Bend-versus-kink rule
Full-frame damage
Unibody damage

24. Damage (Cont.) Direct damage Deformation at point of impact
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25. Damage (Cont.) Indirect damage Deformation away from point of impact
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26. Damage (Cont.) Upset Bend Kink Bend-versus-kink rule
Compression of grains
Point of arrowhead
Bend
Buckles in which grain structure is not weakened
Kink
Buckles in which grain structure is weakened
Bend-versus-kink rule
Replace kink; repair bend

27. Full-Frame Damage Types
Kickup
Change in frame height
Frame distorted
Part higher than specifications
Sag
Part lower than specifications

28. Full-Frame Damage Types (Cont.)
Mash
Change in frame length
Frame shorter than specifications
Sidesway
Change in lateral orientation
Frame distorted
Part of vehicle laterally distorted

29. Full-Frame Damage Types (Cont.)
Diamond
Change in orientation of frame rails and cross members in center section of vehicle
Do not form right angles
Twist
Not level to each other

30. Front Impact Full-Frame
What types of damage are shown here?
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31. Side Impact Full-Frame
What types of damage are shown here?
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32. Rear Impact Full-Frame
What types of damage are shown here?
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33. Rollover Full-Frame What types of damage are shown here?
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34. Unibody Damage Types Kickup Sag Mash Sidesway Twist
Change in orientation of rocker panels and cowl
Rocker panels not level to each other

35. Front Impact Unibody What types of damage are shown here?
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36. Side Impact Unibody What types of damage are shown here?
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37. Rear Impact Unibody What types of damage are shown here?
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38. Top Impact Unibody What types of damage are shown here?
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