solar imapct absorbing body structures

8/19/2019 Solar Imapct Absorbing Body Structures

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Impact absorbing body structures



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Contents

•The cost

• Accident statistics

•Vehicle safety

•Pedestrian safety

•Bumpers

•Bonnets•Bumpers

•Towing eyes

•High impact crashes

•Crush and crumple ones

•!ront impact

•"ide impact

•Crash simulators

•Created by Har#ey Heath 2$$%



&

The cost of road accidents is huge and on going'(

• salvage and repair/replacement of motor vehicles

• repair/ replacement of other property

• emergency services

• hospital and medical expenses

• long term health services

• invalid rehabilitation

• loss of income

• loss of personal productivity

• loss of productivity due to transport interruptions

• legal expenses



%

What makes a vehicle safe in a crash?

answer- “stronger is best used to be the approach by motormanufacturers and the general public and up to a point

is still a philosophy that has some consideration when

people buy motor vehicles

+!ow the thinking is changing" manufacturers have been

actively changing body and chassis design to make

their vehicles safer by fitting energy absorbing sections

to the body and cushioning devices inside to protect

occupants



,

-ld #ehicles constructed entirely for strength using full

chassis or monoco.ue/subframe construction for o#erall

strength0

This design has been identified as dangerous to bothpeople inside and outside the #ehicle

average records from the #S$ show%-

&'( of all vehicle accidents are front to front impacts

these contribute to &'( of all motor vehicle relateddeaths

side impact is identified as the ma)or impact causing

death and in)ury

rear impact has less fatalities but creates more severe

in)ury

roll over statistics show *+( increase in fatalities if

e)ected from the vehicle

low speed contact with pedestrians created high

fatalities due to protrusions and non absorbing bodywork



1

What makes a car safe?

trend ,. *''&

Safety features% air bags" seat belts ( .+(

Crash prevention% $0S" tires"radar

,( &&(

0ody strength% bumpers" chassis +&( 1*(

2mpact absorption ,1( *'(

3ehicle 4ake% design" shape ( ,1(



5evelopments to reduce in)ury when impacting with pedestrians

Crash analysis has shown that not only were older vehicles withbumpers designed to fend off other vehicles" dangerous" but also

protrusions such as over riders" grille and bonnet ornaments" caused

in)ury even at low speed6

7he height of bumpers forced pedestrians under the bumper rather

than over

8ead in)ury caused by the momentum of the vehicle forcing the body

over the bonnet and into the windscreen without any cushioning or

absorption factor6



3

Body shape has been identified as potential danger areas when impact

pedestrians0

0umper sections lowered to lift rather than force down6

0umpers now must have cushioning sections and mountings

0onnets must have “soft sections to absorb head impact6



4$

In 431% #ehicles manufactured and imported into 5"A had to ha#e impact

absorbing bumpers in attempt to reduce pedestrian in6ury and also reduce

#ehicle repair costs in#ol#ed in low speed impact0

,.& 9nglish 7:

,.& $merican export 7:



44

Bumper mounting points are made to absorb impact by deforming or

crushing in on themsel#es7 or using hydraulic shoc8 absorbers that

mo#e to absorb impact0



42

All bumpers are designed to absorb the impact9s energy through a

series of #al#es and air chambers or hydraulic chambers0 Bumpers are

also sometimes designed with built(in :crumple ones; which fle<es onthe impact0



4&

Impact absorption bumpers

steel mounting

Aluminium armature

Polycarbonate co#er

polystyrene foam filling

They are molded in thermoplastic polycarbonate and tested to absorb

impacts up to =ph



4)


Bumper side mountings are .uic8 release type that are not bolted and

brea8 away on impact



4%


Crash test dummies used to determine danger points on the front section

that could reduce in6ury during pedestrian impact



4,


This shoc8 cone aluminum bonnet has been de#eloped by *ada to

reduce impact7 and tests show reductions in the e<tent of head in6uries

with #ehicles fitted with this de#elopment0



4

<ront and rear towing hooks not only present a danger to pedestrians

but also cause extensive vehicle body damage in low impact collisions



43

The mismatch of bumpers presents a problem with energy absorption not

starting in the correct place causes e<tensi#e body damage when low force

energy absorption sections should ha#e controlled the situation

>ow high performance #ehicles ha#e poor

bumper protection

)+) *PV pro#ide littleprotection to other #ehicles



2$

>ow speed impact appears to create a lot of damage but is created by

the crumple one wor8ing0

In this case the shoc8 absorbing sections ha#e folded to ta8e the energy

out of the impact0 The bumper has fle<ed and the mountings ha#ecollapsed to deform the front section0 The side guards are not part of the

shoc8 absorption and push out of the way0 The bonnet has a shoc8

absorbing section which causes it to fold rather than mo#e bac8 into the

windscreen or the passenger cage0



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The force created during a crash can be #ery high and absorption of #ehicle

energy ta8es time to dissipate0 In cases li8e this7 no amount of crumple one

can stop the #ehicle destroying itself7 but the passenger cage is remar8ably

intact though ob#iously some intrusion has ta8en place0



22

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Accident statistics



2&

A few statistics about #ehicle crashes

>&( of all road accidents are caused by human error

,6,( of road accidents are related to vehicle failures

6+( accidents related to environmental factors

.6,( involve pedestrians

,6'( other factors

The three main dri#er related causes are

speed unsuitable for the conditions

failure to yield right of way

errors in leaving the traffic flow



2)

?ewton9s first law0

“An object in motion will stay in motion with the same speed and in the

same direction unless acted upon by an unbalanced force”

A crumple one is built into the #ehicle to absorb energy on impact0 The

purpose is to increase the amount of time it ta8es the #ehicle to come to a

complete stop in comparison to the ob6ect the #ehicle is impacting with0

Ha#ing a crumple one7 the time it ta8es for the #ehicle to come to a stop may

be e<tended form $0$4 seconds7 to $02 seconds0 By ta8ing more time to slow

down using the crumple one by a factor of 2$ will decrease the acceleration

and therefore the force factor0

Crumple ones yield during a crash changing energy into heat and sound7

which in turn reduces chances that occupants of the #ehicle being hurt0



2%

Time

(MS)Events

,* initial folding of longitudinal

, initial folding of sub frame

*, 4st buc8ling of rails upper in front of shoc8 tower

1+ engine contacts barrier

1. buc8ling rear of sub frame at fi<ture on e<tension longitudinal

+' rear end of longitudinal start to buc8le behind reinforcements

+, wheels contact barrier

. ma<imum dynamic deformation

7he events as the crash happens



2,

' ms Crash begins( bumper contacts impact ob6ect

,+ ms Crash sensor determines to deploy air bag or not

*' ms The seat belt tensioners ignite

*+@1+ ms All front air bags brea8 free and start to inflate

&+ ms @ri#ers air bag is fully inflated

++ ms Passenger air bag fully inflates usually larger than the dri#er9s air bag

' ms @ri#er9s head and chest contact air bag

.' ms Passenger9s head and chest contact air bag

,'' ms Body impression into air bag is at their ma<imum and start to rebound

,+' ms Body tra#els bac8wards until retained by the seat and head rest

one millisecond one thousandth of a second

7he vehicles safety features operating



21

Vehicle manufacturers built in compression or crush ones into the

front and rear of the #ehicle to protect the passenger cage0

These ones act as time delays to absorb impact energy



2

0umper mounts absorb low speed

impact $ir bag sensors mounted here

Crash energy dissipated throughbonnet and hinges

Cross car beam forms front of

passenger cell as well as resist side

intrusion

:einforced doors with side intrusion

bars

:ear floor pan bends upwards to keep

intrusions away from the fuel tank

:ear absorption defuses energy with

controlled crumpling

0umper beam distributes point load

across the body structure

Crush Aones built into front panelsto absorb energy

Severe impact drive train buckles

under and directs engine under

safety cage

5oor hinges and latches withstandimpact and resist opening under

collision

:igid floor pan transfers crash force

through vehicle and protects

passenger cage

$"0" and C posts support roof and

form top section of the cage

:ear bumper integrated into body to

help with impact dissipation and

absorption



&$

Vehicle design must now incorporate safety features not only for the

passengers inside abut also for pedestrians impacting on the outside

Vehicle design must in#ol#e impact absorption in a number of differentdirections

!rontal impact energy transferred through the frame around the cage



&2

Crumple ones are created by using panels that ha#e of #arying thic8ness

and shape to induce folding and bending at particular points

Panel compression is created in &@ computer software to determine

pressure and distance



&&

Panels fold at particular points and absorb energy as the collapsing ta8es

place



&)

Front side member deformation aids

By creating a crush initiator the designer ensures that when the front side

member contacts the opposing structure at the point where force is

introduced7 namely the point of highest pressure7 a con#ersion of energy

begins immediately and this shoc8wa#e begins to counter the speed of the

#ehicle0 Dhen the pressure wa#e reaches the end of the rail7 it is reflected

and rebounds from front to rear se#eral times0

*A""

Area of high

impact pressure

counter wa#e formation

frontal shoc8 wa#e against

#elocity wa#e of material



&%

αα+∆/

AB

C

@

E

!

F

Front side member deformation aids



&,

Impact absorption is controlled by

panel shape and thic8ness0The enclosed section with the

separators clearly shows how

panel deformation has occurred

during impact and slows the

speed of the #ehicle while the

energy is directed and redirected

in the body sections0



&

Testing enables accurate data to collected as to how panels will react in

8nown circumstances0

Absorption of crash energy can be determined using crush sections or

deformation aids formed in the panel sections



&3

The research and de#elopment costs are huge7 especially after all the

theoretical and computer generated tests ha#e been completed7 manufacturers9

use real #ehicles in the final testing stage0

This test underta8en by *ercedes to chec8 the energy absorption of the small

smart car against the large family saloon0



)$

The odds seemed stac8ed against the automoti#e welterweight7 partly

because of the enormous weight difference ratio of 4'20 The "marts lac8

of a protecti#e long front end was another source of doubt before the

crash test began0 Although the collision was to ta8e place with both

contenders dri#ing at a speed of %$ =ph0

The huge difference between their weights meant that the impact would

ha#e #ery different results on each of them0 !or the hea#y *ercedes7

the impact would be e.ui#alent to crashing against a barrier at a speed

of && =ph0

The lightweight "mart7 howe#er7 would ha#e to absorb an impact

corresponding to a crash against a stationary barrier at a speed of ,1

8ilometres per hour ( double the speed of the *ercedes0

The measurements carried out on the four participating test dummies

showed that potential occupants in the two #ehicles would not ha#esuffered any life(threatening in6uries0 The passengers in the "(Class

would in all li8elihood ha#e wal8ed away without a scratch7 while the

passengers in the smart would ha#e suffered bruised ribs7 and the dri#er

would ha#e also had some slight leg in6uries0



)4

Crash simulators are used in the

final stages of crash absorption

de#elopment using controlled

trac8s7 #ehicles can be forced into

barriers representing solid ob6ects

and other #ehicles with shoc8

absorbing capabilities0

By using crash dummies7 potential

in6uries can be monitored to all

passengers inside the cage0

High speed cameras are used torecord all actions during the

impact0



)2



)&

!rontal impact is not always s.uare

on and may in#ol#e ob6ects that ha#eno impact absorption of their own0

This causes all #ehicle momentum to

be absorbed by the #ehicle7 especially

when not all the #ehicle crumple one

is e<posed to the energy force0

5ne.ual force such as this will re.uire

the e<posed crumple one to account

for all the #ehicle energy unless the

ob6ect being hit also has energy

absorption facilities0



))

"ide impact is ma6or cause of head and chest in6ury and door strength is

important as well as being able to di#ert crash energy around the passenger

cage0

@oor intrusion bars or braces are constantly be testing both using computer

simulation and actual #ehicle testing0



)%

This graphic clearly shows how side intrusion is pre#ented by

transferring energy through the controlling sections in the floor pan and

lea#ing the passenger cage intact0



),

"trength in the door frames is achie#ed by intrusion bars across the door

frame0 !rame shape causes the e<terior of the door s8in to ride o#er the

pillar and 8eep the door shut under impact0

The door is foam filled between the steel frame and the trim panel which

helps absorb impact and protect the pel#ic section0



)1

"ome #ehicles are more prone to occupant in6ury regardless of crumple

ones and side intrusion protection0 Air bags and seat belt pensioners do

help but body design also allows these protection de#ices to mounted in

the most ad#antageous position0



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solar imapct absorbing body structures

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