Electronic Thesis/Dissertation

 

Development and Validation of Progressive Deformable Barrier Modeled with Shell Elements Open Access

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Deformable crash test barriers used for vehicle crash tests are made of deformable aluminum honeycomb blocks. These aluminum honeycomb blocks have excellent energy absorbing capabilities. They have different crush strengths representing the front end of a vehicle. The finite element models of these crash test barriers are used extensively by auto manufacturers to optimize the vehicle structure. Hence in a finite element simulation, the behavior and the crush modes of the barrier have to be simulated accurately. Historically, in these barrier models the honeycomb blocks were represented using solid elements. Due to large deformation seen by the barrier the solid elements are prone to negative volume problems which greatly reduce stability and accuracy of the simulations. In this study a finite element model of Progressive Deformable Barrier (PDB) is developed using shell elements to overcome the negative volumes and inaccuracies issues. Discretizing the honeycomb cell to its exact size was not feasible due to extremely small cell size. A scaling method is used to model the PDB. The main objective of this research was to simulate the global and local crushing behavior of the honeycomb blocks and the characteristic deformation modes observed in the physical tests.PDB has honeycomb blocks with progressively increasing stiffness in the depth direction. The compressive strength of the PDB is controlled by progressively increasing the thickness of the shell elements. The various honeycomb blocks are tied using adhesives and tied contact is used to represent the adhesive. The FE model of the PDB with shell elements was compared to a previously developed barrier using solid elements. The shell element model simulations showed noticeable improvements in the validation tests. Particularly, the validation test with large local deformation and shearing of the honeycomb cells showed improvement and stability in the shell element PDB model. In order to demonstrate the robustness and the stability of the FE model in large deformations, a 50% offset Frontal simulation at 60 kph was simulated using a FE model of Ford F250 pickup truck (model year 2006).

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