|
Return to the
central of
this site.
Return to "The Whiplash-injury" main Page.
Retur til "Whiplash-skader" Hovedside.
EXTRACT G.
For the table of contents of the
EXTRACT of the compendium.
Return to EXTRACT F
Part E: Conclusions.
It is two factors which has to be present if any
deformation, causing injuries or not, shall take place:
a) The acting force towards a structure is so
strong giving a particular a deformation.
b) The force acts with an energy of such amount
that the structure is deformed beyond it's limits of elasticity.
In an impact, the force acting towards a structure
might be extremely high if the stiffness of the bodies involved
is extremely high. The acting force depends of how long time the
impact lasts. Knowing the accelerating force, the acceleration
of the body depends on the weight of that particular body.
The amount of energy that absorbed by deformations
of the items involved, is independent of their structural strength,
only of the masses and the difference in the velocities as the
impact starts.
It will be a lower limit of the possibility of
injuries towards a body in a rear-end collision and it will be
a minimum of strength and of energy required to give deformations
to affected structures exceeding the deformations the structure
is able to resist without being injured.. To find those limits,
any part of the body affected by such an incident are to be considered.
Facing tiny structures where the smallest shifting may exceed
what it may tolerate without being hurt, I am afraid such a limit
has to be rather low and very difficult to define. And it will
not be the same limits for all the structures.
To consider only the acceleration of the cars
itself is a way to avoid meeting the reality in any collision
as the loads towards the body depends on how the body is affected.
To make such a evaluation, a thorough examination of each case
has to be done, including both the structural strength of car
and how they were struck, the flexibility of seat structures and
the way the person was seated.
Having done this thorough study of the nature
of the "Whiplash-mechanism" I have to conclude, from
a technicians point of view:
The "Whiplash-mechanism" is a mechanism
which may involve all parts of the body, from the lower part of
the spine as well as the neck region and the head. It may cause
stretching loads towards the spine and the spinal cord accompanied
by extreme deflections of the neck affecting the structures of
the spinal cord and the medulla as well as central areas of the
brain itself. The combination of a pressure between the scull
and the brain together with a rotation of the brain itself inside
the scull may cause stretching and shearing loads to the brain
structures in the affected areas. The neck region and other exposed
structures may be affected by additional loads because of angular
acting forces or an initial turning of head.
The acceleration of the body in a rear-end collision
must be considered as an impact between the car and the body as
the body is delayed. This is an impact between two items with
a very large difference between the masses, giving a significant
increase in the velocity of the body even at low velocities of
the struck car. Dependent of how the person is seated, and the
properties of the structures, mainly of the seat structures, the
acceleration of the person may be significant even in low velocity
collisions.
Glesvaer the 14 th. of May 1996
Kjell Olav Pettersen signature,
Naval architect.
Return
Return to the
central of
this site.
Return to "The Whiplash-injury" main Page.
Retur til "Whiplash-skader" Hovedside.
The contents of, or any part of
this compendium, are not allowed to be made public or copied without
my permission.
|