Collision Dynamics

A GUIDE IN UNDERSTANDING THE FORCES OF A COLLISION

Collision

Collision

Dynamics

May or may not have visual

indicators!

Collision Dynamics Is the knowledge and understanding of the forces involved in a

collision

Collision Dynamics Visual Inspection

Measuring Analyzing

Repair Planning Documentation

OEM Procedures

Inertia Load

Pathing

“Not Just Knowledge

But Know How”

Training

Front End Impacts

The Purpose of Crash Testing

Side Impacts

Rear Collisions

Side Collision

Pedestrian 5 4

3 2

1

These aren’t your father’s cars anymore

1959 Bel Air at a 40 MPH/ 64 KM

¾ offset Impact Is that my

Knee?!

2009 Chevy Malibu 40MPH/ 60KM

¾ offset impact

Ah! I spilled

my drink!

The advanced technology engineered into vehicles

today has changed the way vehicles react in a collision and,

consequently, the way they are looked at for repairs.

Load Pathing

►Engineering how the collisions are directed thru structure

►Collision Dynamics:

►Front

►Rear

►Side

►Rollover

Forces within the vehicle

Collision Forces-

What creates a collision

Force from another object

or vehicle.

Internal

A collision consists of two or

more objects impacting each

other causing a change in

motion. Both moving or One

moving and one stationary -

Forces within the vehicle

Collision Forces-

What creates a collision

Force from another object

or vehicle.

Internal

A collision consists of two or

more objects impacting each

other causing a change in

motion. Both moving or One

moving and one stationary -

Understanding Inertia

Inertia is “the tendency of a body at rest to remain at rest or of a body in motion to remain in motion”

A change in motion presents itself as a force. Moving Force

Resisting Force

The more sudden the change, the stronger the forces created during the change

Size and Weight (Mass) has a tremendous influence on the effects of Inertia and the amount of force it generates.

Types of Forces

Internal Forces E

xte

rnal

For

ces

Types of Forces

The Internal Force is now trying to resist movement against the vehicle crashing into it.

Structural Misalignment (Deflection)

To better understand deflection of

collision forces we first study “simple”

uniform collisions. This rail was

damaged in a controlled environment

causing the rail to collapse like an

accordion

To repair this uniform structure, one

end must be held while pulling the

other end straight out, reversing the

forces which caused the damage.

“Simple, Uniform” collisions don’t occur

Vehicles do not have a uniform structure and

rarely, if ever, impact another object in a perfect straight line.

In reality, most collisions occur at some angle and involve

deflection of forces, resulting in “complex” damage.

What factors

affects

Structural

Misalignment?

Two Factors Two majors

factors in

Structural

Misalignment

Vertical

Misalignment Structural Design of the

vehicle is responsible for

most vertical (up and

down) misalignment.

This is a major factor in

the three section

principle

1

The lower structure "steps" up and over the suspension at the ends of the vehicle.

This creates a situation in which the structural members in the suspension area deflect vertically when collapsing - especially from a

front or rear collision.

Misalignment from Structural Design

It is essential to understand

the metal structure of today’s

vehicles in order to achieve a

complete understanding of

vehicle reactions to impact in a

collision.

Direction of

travel The direction of travel is

responsible for most

lateral (sideways)

misalignment. Most

people would turn the

steering wheel to avoid

the collision if possible.

2

MISALIGNMENT FROM THE DIRECTION OF TRAVEL

Passenger compartments do not react the way they typically did in recent years.

So What Has Changed?

►Deflection of forces around the passenger compartment may change where the energy is directed.

►AHSS steel placement in critical areas

►Slowing the collision forces thru design

►Crash Pulse

►Load pathing

Load Pathing

►Engineering how the collisions are directed thru structure

►Collision Dynamics:

►Front

►Rear

►Side

►Rollover

Collision forces entering the vehicle encounter better energy absorption and force management due to the use of AHSS.

Engineers, through design, are able to direct forces in specific paths through the structure. Less damage makes its way into the center section, but damage will still occur and closer examination will be required to locate that alternative damage.

Advanced steels found in the windshield pillar design and other areas of the center section absorb and transfer energy around the passenger compartment

leaving it intact with very little or no distortion.

While energy is being transferred it is also being absorbed. This is evident in the characteristic rippling and buckles in the pillar.

It is important to recognize that patterns of damage that may have been

characteristic in the past will not necessarily repeat in newer designs.

The vehicle's direction of travel and any variation in its angle from a straight-ahead position during the collision will be responsible for most of the lateral

misalignment.

Impact Area

If the position of the vehicle is not straight ahead, in relation to its direction of travel during the collision, lateral misalignment will result.

Advanced steels located in

the center section help

control the amount of

intrusion in that area and

redirect the energy around

the occupants.

The center section is basically a

straight, flat, rigid area reinforced

by the rocker panels and inner

reinforcements

This combination is

very strong and

resists

misalignment

For this reason, as

collision forces begin to

misalign the structure,

the end sections (front

and rear) tend to

misalign relative to the

center section.

Each section reacts independently

The heavier the section, the stronger the inertial effect will become.

Three Section Principle

►Do all vehicles have three sections?

Manufacturers are producing smaller more compact vehicles, but do these types of vehicles still react as three distinct sections?

There is still an area that steps upward in the suspension area, both at the front and rear, creating three sections, but those sections are much smaller in relation to the center section.

Even with the smaller end sections we still have forces reacting but

because of the size of the sections the misalignment from each section

will not have the same amount of force as if the section was larger.

Direct Misalignment

Damage at the point

of impact

How misalignment is

Categorized

Indirect

Misalignment

Damage beyond

the point of

impact

2

1

Direct Damage

Indirect Damage due to Energy Transfer

If the repair is approached properly, the direct misalignment will be repaired by pulling directly at the points of impact. Much of the indirect misalignment can

be corrected simultaneously by holding and supporting the vehicle at the proper points.

Understanding the difference between the two types of damage is important from a repair standpoint.

5 Milliseconds

At 5 Milliseconds the body structure is already absorbing and managing the crash force energy

5 Milliseconds

At 5 milliseconds air bag sensors detect loads and rates that require activation. Seatbelt pre-tensioners activate for sensor input

10 Milliseconds

►At 10 milliseconds the bumper is fully collapsed and crash forces are being directed through the upper and lower body members

15 Milliseconds The engine sub/frame begins to deform

20 Milliseconds

►The structure forward of the engine is fully deformed and the crash load is transmitted into the roof rail, rocker and rear portion of the engine subrame

20 Milliseconds

►The main front crash rails begin to deform often using crush initiators to trigger an accordian-like deformation

30 Milliseconds

►At predetermined points the upper and lower frame rails continue to deform absorbing and redirecting crash loads

30 Milliseconds

►Occupants are launched forward. The load from their movement is transferred to seat and seatbelt mounting points.

50 Milliseconds

►The engine/transaxle assembly contact dash and the wheel contacts the barrier.

►The A-pillar, roof, door pillar, rocker and floorpan carry balance of the crash load

67-99 Milliseconds

Maximum deformation of the vehicle is achieved The crash load has transferred around and under the occupants The passenger compartment deformation controlled and penetration is limited.

100 Milliseconds & Returned to Pre Accident Condition

►Event is complete

Collision Types

FRONT END COLLISIONS

When a vehicle collides with an another object a change in motion occurs. The contact

point will begin to stop while the rest of the vehicle continues in motion.

FRONT END COLLISIONS

As the impact point comes to a stop, the rest of the vehicle continues and the front section of

the vehicle becomes shorter in length. At this point vertical misalignment above the wheel

occurs due to the structural design in the suspension area.

FRONT END COLLISIONS

Energy continues to be absorbed in the front, and the rest of the vehicle continues to move

forward. As the A-Pillar comes to a stop, energy is distributed through the pillar and,

likewise, into the floor to rocker area within the center section.

FRONT END COLLISIONS

Without advanced steels the center section is subject to collapse and distortion,

possibly causing injury to the occupant.

REAR END COLLISIONS

Rear end collisions are the second most common type of collision.

REAR END COLLISIONS

At the point of the impact, the vehicle being hit in the rear will present

a resisting force to the forward force applied by the outside object

Upon impact, the end of the rail will begin to move down in relation to the suspension area’s upward travel, as the rear section begins to shorten.

In the past, rear end collision damage could easily extend the length of the vehicle to include collapse of and intrusion into the passenger compartment.

Note: All rear impact testing is currently done at 30 MPG (48KPH) but

authorities are considering a change to increase it to 60MPG (96 KMP)

SIDE IMPACT COLLISIONS

While not the most common of collisions, the Side Impact Collision is one of the most dangerous due to point of

impact being directly into the passenger compartment. This type of impact is more likely to produce injuries or fatalities due to the fact that there is very little separation between

the passengers and the devastating external forces encountered.

SIDE IMPACT COLLISIONS

During the side impact the outside force moves the center section

laterally with respect to the end sections which resist movement.

Impact force will travel through the upper portion of the center section

A center section employing advanced Steels allows for energy

absorption and distribution of the forces with very little distortion.

That front section of the vehicle carries the majority of the weight of the vehicle, particularly on front wheel drive models. The engine is mounted in rubber mounts and can move independently. Close examination of the engine compartment for damage and distortion is essential.

The effects of inertia on the end sections and the resistance of the tires against the road to sideways movement will affect the amount of

lateral misalignment of the end sections.

“Banana Effect”. The end sections

move toward the impacted side of the

vehicle, in respect to the center

section, leaving much wider gaps on

the opposite side.

With the use of advanced steels there is less intrusion into the passenger compartment which results in fewer injuries and fatalities.

Work hardening of the advanced steels used in the pillars and door beams increases energy absorption and greatly reduces intrusion into

the passenger compartment.

Advanced steels and design combine to efficiently direct collision forces around the occupants for better survivability.

The advent of side curtain airbags has had a dramatic affect.

Side Curtain Airbags

ROLLOVER COLLISIONS

When a vehicle overturns or rolls over it creates what is considered to be multiple collisions.

Each time the vehicle impacts an object (or the ground) a separate collision has occurred and each collision must be addressed independently from a planning and repair standpoint.

Rollovers are probably the least common type of collision. In terms of severity or injury/fatality rates rollover is among the highest.

Implemented by the

Insurance Institute for

Highway Safety (IIHS),

NATEF standards have

increased from 1.5 times

the vehicle weight to 2.5

times the vehicle weight

for Roof Crush Testing.

During a rollover the vehicle will generally impact one of the front windshield corners causing the roof and windshield area to

collapse into the passenger compartment.

As the roof comes to a stop at impact, the rest of the vehicle continues to move downward this and generally results in massive upper body damage

and serious injury to passengers.

Advanced Rollover

Prevention

Advancements in material and design are allowing increased roof crush test standards to be met, reducing intrusion and increasing survivability.

Roof rails are now being reinforced with advanced steel inner

structure that will withstand the collision forces and disburse

the energy to areas outside of the passenger compartment.

Conclusion

Many of the vehicles being manufactured for 2010 and beyond will be designed and manufactured to meet or exceed the recommended safety test standards.

This will present a problem for the repair industry until estimators, appraisers and technicians learn to locate and implement the OEM’s requirements and procedures to ensure proper and complete repair of each specific vehicle make and model.