Simplifying the Structural Design of the Advanced Pedestrian Legform Impactor for Use in Standardized Testing 2018-01-1049

The advanced Pedestrian Legform Impactor (aPLI) incorporates a number of enhancements for improved lower limb injury prediction capability with respect to its predecessor, the FlexPLI. The aPLI also incorporates a simplified upper body part (SUBP), connected to the lower limb via a mechanical hip joint, that expands the impactor’s applicability to evaluate pedestrian’s lower limb injury risk also in high-bumper cars.As the aPLI has been developed to be used in standardized testing, further considerations on the impactor’s manufacturability, robustness, durability, usability, and repeatability need to be accounted for.. The aim of this study is to define and verify, by means of numerical analysis, a battery of design modifications that may simplify the manufacturing and use of physical aPLIs, without reducing the impactors’ biofidelity. Eight candidate parameters were investigated in a two-step numerical analysis. One of the parameters was related to the SUBP structure, six to the mechanical characteristics of the hip joint (x-rotation, and y and z displacements), and one to the ankle joint characteristics (x-rotation). First, the individual effect of each candidate parameter on biofidelity targets was assessed based on linear regression analysis of three peak lower limb injury measurements (femur bending moment, knee medial collateral ligament elongation and tibia bending moment) from impact simulations conducted with either a human full-body model or with the corresponding aPLI model. Second, the same methodology was applied to assess the cumulative effect of the candidate parameters on the biofidelity targets with different aPLI versions that incorporated a gradually increasing number of simplifications. The most remarkable results revealed that a compact SUBP connected to the mechanical lower limb by a highly simplified cylindrical mechanical hip joint can be incorporated to the aPLI design without reducing its biofidelity. In addition, the methodology applied to simplify the aPLI design proved effective to find the simplest solution.