BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI

96 Iulian Agape et al
1. Introduction
During the evolution of automotive there were elaborated different
calculus models for the impact moment velocities, differing on the theoretical
bases used to establish the calculus relations.
In most cases, at the scene of impact are found exclusively only later
produced traces, making easier to determine the post – collision speeds for the
involved vehicles. Most times, the only evidence that may be related to pre –
impact kinematic parameters of the vehicles are the remaining deformations
resulting from impact.
The most competitive calculus models, that generated already
acknowledged numerical calculation programs, are based on the application of
the impulse conservation principle with the consideration of the connection
between energy needed to produce deformations, remaining deformation
amplitude, equivalent speed and body rigidity of involved vehicles.
The CRASH-3 model, well – known for the accuracy of the results,
requires knowledge of remaining deformation, stiffness coefficients, and the
main force of impact direction. The procedure involves dividing the
deformation front in 2, 3 or 5 equal intervals of L length, purpose for
establishing on the deformation front 3, 4 or 6 equidistant points, in which the
remaining deformations will be determined.
The evaluation of deformation values in these points is appreciated as
sufficient for the average deformation determination, with an acceptable
accuracy. Evidently, the increase of the number of points where the deformation
is determined leads to the improvement of the method.
2. The Deformation Function
The algorithm requires dividing the impact zone width (L) in n equal,
consecutive intervals, each with the length L/n, n∈∞ * , n finite number. For
defining the deformation function it will be considered a frontal deformed
vehicle and an orthogonal coordinate system will be jointly attached to this
vehicle. The Ox axis of this system will be normal to the longitudinal axis of the
vehicle, and the Oy axis of deformations will contain the first point of the
vehicle front, starting from left (advancing way), in which the deformation is
measurable.
There is the possibility that, based on deformation values determination,
ξ i in a number of (n+1) equidistant points distributed on the L impact zone
⎛ L ⎞
length, ξi
= ξi⎜( i −1)
n
⎟, 1, ( 1)
⎝ ⎠ i=
n+
, n∈ϒ* , n finite number, to determine an
algebraic function for the deformation, with the form: f: [0, L]→ϒ; f = f(l), so