solar imapct absorbing body structures
TRANSCRIPT
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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$$%
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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
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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
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-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
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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(
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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
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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
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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:
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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
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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
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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
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Impact absorption bumpers
Bumper side mountings are .uic8 release type that are not bolted and
brea8 away on impact
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Impact absorption bumpers
Crash test dummies used to determine danger points on the front section
that could reduce in6ury during pedestrian impact
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Impact absorption bumpers
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
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<ront and rear towing hooks not only present a danger to pedestrians
but also cause extensive vehicle body damage in low impact collisions
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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
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>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
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<:=!7$; 6>( +6*( .6&( +6,(
S259 24$C7 ,6,( ,6>( *6( 16.(
:9$: 24$C7 '6>( 16( '6+( &6(
Accident statistics
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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
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?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
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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
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' 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
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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
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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
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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
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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
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Panels fold at particular points and absorb energy as the collapsing ta8es
place
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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
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αα+∆/
AB
C
@
E
!
F
Front side member deformation aids
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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
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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
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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
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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
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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
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!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
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"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
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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
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"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
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"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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