78 Section 1 Introduction to Collision Repair
Copyright Goodheart-Willcox Co., Inc.
■ Inertia is the tendency of an object to remain at
rest or to remain in motion.
■ The object that a vehicle collides with is called the
target.
■ If an impact takes place at a vehicle’s center, the
damage will be greater than if the impact takes
place away from the center.
■ If the surface area of impact is large, the collision
force will be spread out over a large area. If the
surface area of impact is small, the collision force
will be concentrated in a small area.
■ Damage that occurs at the point of contact during
a collision is called direct damage. Indirect damage
occurs away from the point of impact and is a
result of the direct damage.
■ The bend-versus-kink rule states that damaged
high-strength steel parts can be repaired if they are
bent but must be replaced if they are kinked.
■ A change in frame or unirail height is called kickup
when the frame moves upward and sag when the
frame moves downward.
■ A change in frame or unirail length is called mash.
■ The lateral movement of the rails is called
sidesway.
■ Twist damage is present when the frame rails or
rocker panels are not level with each other.
■ If the vehicle has diamond damage, the center
section of the vehicle no longer forms a rectangle.
Activities
1. Select a vehicle(s) in the shop and identify the four
types of crown.
2. Draw an arrowhead. Identify its component parts.
Use the color red to indicate the strongest part of
the damage.
Review Questions
Answer the following questions using the information
provided in the chapter.
1. List the factors that determine the grain pattern of
steel.
2. _____ is the ability of metal to bend without
permanent deformation.
3. Explain the difference between a buckle and a
bend.
4. Work hardening _____ the strength of metal.
5. A(n) _____ crown panel has very little curvature.
6. What are the components of force?
7. _____ force is applied from one end.
8. Explain how a collapsed hinge buckle is formed.
9. _____ is the tendency of an object to remain at rest
or in motion.
10. Explain how surface area of impact determines the
amount of damage a vehicle sustains in a collision.
11. Explain the difference between direct and indirect
damage.
12. The compression of grains is called _____.
13. A(n) _____ has a buckle that is greater than 90° in
a short area.
14. All load bearing and structural parts of a damaged
vehicle should be replaced if buckled.
True or False?
15. A(n) _____ vehicle is designed to collapse during
a collision, absorbing impact forces.
ASE-Type Questions
1. 1 Technician Te ch ni ci an A A says s ay s that th at grains g ra in s are ar e formed fo fo rm ed by b y the th e
cryst y ta lli ll in e pattern p tt f of th t he m t et l al a d nd alloy ll y m lec ol les. ul
Technician Te ch ni ci an B B says s ay s that th at different d if fe re nt types t yp es of o f metals me ta ls
have ha ve different d if fe re nt grain g g ra in patterns. p p at te rn s. Who W ho is i s right?g ri gh t?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.
2. Each of the following will affect elasticity of sheet
metal except:
(A) alloying elements.
(B) annealing process.
(C) humidity.
(D) shape.
3. Which of the following properties of metal indicates
how readily the metal can be shaped by bending
and stretching?
(A) Elasticity.
(B) Deformation.
(C) Plasticity.
(D) Inertia.
4. Technician A says that a low-crown panel will flex
in and pop out. Technician B says that a reverse-
crown panel flexes as much as a low-crown panel.
Who is right?
(A) A only.
(B) B only.
(C) Both A and B.
(D) Neither A nor B.