Study and Optimization of Car Hood for Pedestrian Head Safety by Using Simulation Technique

Head and face injuries in pedestrianaccount for 60 % of all pedestrian fatal injuries, whereas 17.3 % of head injuries were due to the car hood. The above ratios show the necessity to consider carefully the role of the hood in pedestrian he safety. Redesigning the hood structure to improve pedestrian protection has recently received considerable attention by automobile manufacturers and industry institutes. However, there is a lack of research that considers methods of choosing the most effective thicknesses of hood skin and hood reinforcement with respect to pedestrian safety. The aim of these tests was to compare the general pedestrian friendliness of steel and aluminum, used as hood material. The tests were conducted on a car that is still available on the market with either a steel or aluminum hood, both having the same desig


I. INTRODUCTION
The hood and bumper, with which pedestrians come in frequent contact, can be designed and manufactured to be pedestrian friendly, effectively decr injuries [3]. During the development of a safe hood and bumper structures, experiments and computer simulations are used to evaluate their performances Computer simulations contain many errors from inaccurate modeling and approximation of governing Equations. On the other hand, experiments are considered to be accurate even with the possibility of experimental errors and inaccuracies. In design, it would be the best if all the data could be obtained @ IJTSRD | Available Online @ www.ijtsrd.com | Volume -2 | Issue -4 | May-Jun 2018  Fig. 1 shows that 2010 is about 9.1%. @ IJTSRD | Available Online @ www.ijtsrd.com As expected, more crowded countries will have higher total numbers of pedestrian deaths with China, India, and the Russian Federation in first, second, and third in that category, respectively. Figure 2 shows the experimental set up for the test of hood. The angle for adult pedestrian is taken as 65 when it is falling on hood and the wrap around distance is 1700-2100mm.The wrap around distance is the distance measured from ground surface to the hood surface when the head will be impacted when the height of pedestrian is 154cm. For child pedestrian the wrap around distance is taken as 1000 depending on the height of the pedestrian. As expected, more crowded countries will have higher total numbers of pedestrian deaths with China, India, and the Russian Federation in first, second, and third Figure 2 shows the experimental set up for the test of . The angle for adult pedestrian is taken as 65 0 and the wrap around The wrap around distance distance measured from ground surface to the hood surface when the head will be impacted when For child pedestrian the wrap around distance is taken as 1000-1700mm depending on the height of the pedestrian.  The wrap around distance is measured by using string.

III. Reduced Fe Model Preparation
The full co related model of Toyota Yaris is reduced by cutting it from the B-Pillar and removing the front wheels, seats, door etc. The model is reduced such that the test results will not be affected by the modification done. Fixed Boundary Constraints are applied to the reduced model at the cutting location. The reduced model helps in fast processing of the LS Dyna runs due to reduced number of elements.

IV Test Procedure
The Reduced Car Model is at the same level when the Full Vehicle is standing on the level floor arrested in software and also the degree of freedom been arrested . All translational and rotational degrees of freedoms are fixed (arrested) at the cutting location of BIW. Head is positioned as per Adult Head Impa Zone at 65⁰ to horizontal. The head is impacted on different locations as the location has been assigned by the numbers. The Head is impacted with initial velocity of 9.7 m/s. Head accelerations are measured from the accelerometer which is Determination of WAD [5] The wrap around distance is measured by using string.

III. Reduced Fe Model Preparation
model of Toyota Yaris is reduced Pillar and removing the front wheels, seats, door etc. The model is reduced such that the test results will not be affected by the modification done. Fixed Boundary Constraints are duced model at the cutting location. The reduced model helps in fast processing of the LS to reduced number of elements.
car model cut for analysis The Reduced Car Model is at the same level when the is standing on the level floor as it is arrested in software and also the degree of freedom . All translational and rotational degrees of freedoms are fixed (arrested) at the cutting location of BIW. Head is positioned as per Adult Head Impact The head is impacted on different locations as the location has been assigned The Head is impacted with initial Head accelerations are measured which is fitted in Head form. Zone. Figure 6 shows the boundary condition applied on the reduced car model.

1) Animation instances
Animation instances for test point P0 is shown in figure 9. The animation shows the impact of head on hood at different time instant. This time fraction is in point second. Figure 9 Animation instances for test point P0

2) Overall Stress Plot
The overall stress plot for point P0 is distributed along the hinge supports. The maximum stress developed at the head impact section.

3) Overall Strain Plot
The overall strain plot for point P0 has maximum value at the impact section. In this plot the fringe levels on hood shows the minimum damage to pedestrian head will be possible when the thickness is optimum.

4) Head Injury Criteria (HIC)
The obtained HIC value for point P0 is 159.2, which is the acceptable limit of HIC. Similarly the simulation for all points is carried out.

VI Conclusion
This result shows that the interdependence of the HIC value, the hood reinforcement thickness, and the hood skin thickness is very difficult. This study analyses and proposes a method of identifying the most effective values for the hood reinforcement thickness and the hood skin thicknesses to protect pedestrians while maximizing the hood stiffness. The method presented in this study uses the regression technique to design constraints for the optimization problem. The proposed algorithm identifies numerous critical positions on the hood surface with respect to pedestrian safety. The algorithm used to optimize the thicknesses is solved by combining LS-DYNA and LS-OPT to simulate and analyze the simulation results.