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