Improving the Compatibility of Vehicles and Roadside Safety Hardware (2004) / Chapter Skim
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Pages 60-82
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From page 60... ...
55 Chapter 3 Assessment of Vehicle Characteristics In order to identify vehicle body styles and structural characteristics which were influential during crashes with roadside systems, a review of full scale crash tests was conducted. This review provided a clear indication of the roadside systems that performed best under a series of test conditions with the chosen NCHRP test vehicles (i.e.
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56 9. Vehicle Static Stability Factor In addition, the literature review provided insight into the most appropriate characteristics which should be considered to assess vehicle performance during roadside crashes.
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57 10. Because wheelbase, weight, overall length, overall width, and front track width were highly correlated, by retaining one of them, all of the statistical information contained in original data was preserved.
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58 During frontal impacts with narrow objects, the position of these frame rails is important when considering optimal engagement of the pole/post with rigid structure (engine) or deformable structures (rails)
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59 frontal impact force during impact. These rails are often tubular, box or c-channels welded to the vehicle structure in the case of unibody constructed vehicles.
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60 pickups and may occur during impacts between barriers and similarly configured sport utility vehicles.
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61 impacted device. This information is critical to properly determine barrier heights including longitudinal and end terminals in use.
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62 vehicles. The Rollover Resistance Rating, however, does not address the causes of the driver losing control and the vehicle leaving the roadway in the first place.
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63 current practices utilize the "worst case vehicle" approach where the attributes of the test vehicle lie at the boundary of the population. To aid the selection of an average vehicle, Appendix B lists over 342 vehicle makes and models and their corresponding design attributes.
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64 Length Width Ht Whlbase Curb Wgt. Front Ovrhng Rear Ovrhng Ft.
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65 3.2 Barrier Force Data Vehicle to vehicle crash incompatibility has been attributed to three factors: (1) mass incompatibility, (2)
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66 The barrier used in the New Car Assessment Program (NCAP) is a rigid, fixed barrier with 36 force measuring load cells on its surface.
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67 distributed. The height of the center of the force was calculated, applying static equilibrium relationships as shown in Figure 3.3.
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68 Figure 3.4: Total Barrier Force vs. Vehicle Crush At a crush of 200 mm, the Jeep Grand Cherokee exerts almost twice as much force as the Dodge Neon.
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69 An idealized relationship between the crash forces of cars with different frontal stiffnesses is shown in Figure 3.4. In a frontal-to-frontal collision, the soft car crushes more than the stiff car at the same interface force.
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70 The raw data from all 36 load cells was processed. The raw acceleration and barrier load cell data points were filtered according to SAE J211 Standard, with a corner frequency of 18, using a filter supplied by NHTSA.
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71 vehicles and roadside hardware devices should be aligned to ensure optimal performance of highway systems during crashes. The following full-scale crash tests (#472580-1 and #472580-2)
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72 During the first test (#472580-1) where the impacting vehicle was a 1996 Ford Taurus, the guardrail provided adequate protection during the 25 degree impact.
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73 vertical direction, the lowest structural point of the Lumina falls at nearly the same height as the bottom edge of the W-beam section as installed. This vertical and lateral location of this hard point creates a more favorable condition for loading at splice of the W-beam section.
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74 Figure 3.7: Ford Taurus Stiffness Profile Figure 3.8: Ford Taurus Underbody- Post Crash
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75 Figure 3.9: Chevrolet Lumina Stiffness Profile Figure 3.10: Chevrolet Lumina Underbody- Post Crash At 2 inches of crush, the stiffness profile of the Ford Taurus peaks at approximately 75 N/mm and the shape of the stiffness curve spans from the 3L location to the 7R column. For the Lumina, this curve peaks at 45 N/mm and spans a narrower region across the vehicle.
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From page 81... ...
76 stiffness at this level of crush also peaks at nearly 100 N/mm but spans a much smaller percentage of the vehicle frontal structure, It spans from the 3L location to the 7R location. The implication of this during an oblique guardrail impact would be high levels of deformation of the outer body structure of the Lumina at the outboard regions of the vehicle.
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From page 82... ...
77 Figure 3.11: Interaction of Ford Taurus and Chevrolet Lumina impacting Modified G4(1S)
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