Using Virtual Prototyping and Rapid Prototyping to evaluate, for industrial benchmarking, Pedestrian Safety performances of the front part of a vehicle

All over the world, and mainly in United States [10], since 1977 to 1991 the research centers of the main automotive companies had processed several statistical data on real accidents between vehicles and pedestrians taking care, obviously, to pedestrians' injury [7]. In latest years a research group of EEVC (European Enhanced Vehicle Safety Committee) had examined the statistic works of past twenty years and subsequent several scientific papers, and had realized some documents about "pedestrian test" procedures [2,6,7]. In reference papers of period 1977 - 1997 and in EEVC documents, the scientists describe a proposed homologative test for child-head impact; an impact simulation of a standardized impactor on car bonnet represents it, in order to evaluate the child-head injury as deceleration of its center of gravity [1,4,5]. Injury evaluation criteria is an energy criterion and is quantified by the HPC index (Head Performance Criteria also called, without distinction, HIC - Head Injury Criteria) defined as follows: HPC = [1/t(2)-t(1) (t2)(t1)integraladt ](2.5) (t(2)-t(1))max in which t(1) and t(2) are respectively initial and final impact's instants (t(2)-t(1) is the integration range) and a is acceleration resultant vector, measured by an accelerometer mounted in the head-impactor. The HPC index became very high if the bonnet, during its deformation, hits the under-bonnet very hard part. In past researches we have used a laser reverse engineering facilities for reconstruct the geometry of the external frontal part of a car in order to virtually evaluate, with a numerical/experimental correlated methodology, the performance of the bonnet for Child-Head impact tests. Now we want to evaluate if, in all parts of the under-bonnet area, we can underline a potential impact with under bonnet hard parts. Our research was propose a new method based on virtual reconstruction of the surface that envelopes all the deformation surfaces in internal part of the bonnet. The deformed shapes of bonnet will be evaluated using FEM explicit codes PamCrash. Using a Pre-processor we will reconstruct, starting from a points (FEM model's nodes) clouds, a new surface of maximum deformed bonnet. This surface will be processed and rapid prototyped as a puzzle of shells with their support. This prototyped surface will be super-imposed on the real under-bonnet layout of car and will allow to easily evaluate where and how much our deformed bonnet could hit the hard-parts of the Engine Lay-out. Our results will show a new easy and fast method to evaluate the potential performance of the front part of a vehicle in Child head impact only reconstructing, with a reverse engineering operation, the bonnet shapes (surface) and, after a simple processing, rapid-prototyping the deformed bonnet-shape, in order to avoid to take all the under-bonnet layout with a reverse engineering operation that could be less easy and very time-consuming.