Fundamentals of Collision Damage 4 Chapter Fundamentals of Collision Damage

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.

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

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

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

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

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

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

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 Goodheart-Willcox Publisher

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

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

Collision Factors (Force, Cont.) Longitudinal force Force applied to one end of panel Goodheart-Willcox Publisher

Collision Factors (Force, Cont.) Lateral force Force applied to side of panel Goodheart-Willcox Publisher

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

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

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

Collision Factors (Inertia, Cont.) Goodheart-Willcox Publisher

Collision Factors (Target) Object with which vehicle collides May be hard or soft May be movable or unmovable

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

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

Collision Factors (Vehicle Height) Vertical position of vehicle and target at moment of contact Goodheart-Willcox Publisher

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

Damage (Cont.) Direct damage Deformation at point of impact Goodheart-Willcox Publisher

Damage (Cont.) Indirect damage Deformation away from point of impact Goodheart-Willcox Publisher

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

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

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

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

Front Impact Full-Frame What types of damage are shown here? Goodheart-Willcox Publisher

Side Impact Full-Frame What types of damage are shown here? Goodheart-Willcox Publisher

Rear Impact Full-Frame What types of damage are shown here? Goodheart-Willcox Publisher

Rollover Full-Frame What types of damage are shown here? Goodheart-Willcox Publisher

Unibody Damage Types Kickup Sag Mash Sidesway Twist Change in orientation of rocker panels and cowl Rocker panels not level to each other

Front Impact Unibody What types of damage are shown here? Goodheart-Willcox Publisher

Side Impact Unibody What types of damage are shown here? Goodheart-Willcox Publisher

Rear Impact Unibody What types of damage are shown here? Goodheart-Willcox Publisher

Top Impact Unibody What types of damage are shown here? Goodheart-Willcox Publisher