변형 가능한 전단 반구형 내부 심재를 가진 초경량 금속 샌드위치 판재의 충격 특성 분석

Abstract

Recently, the needs for the development of the light-weight materials with high stiffness and crashworthiness have been increased to improve the safety of passengers and the energy efficiency of transport vehicles. The objective of this thesis is to investigate into the impact characteristics of ultra-light weight sandwich panel with deformable sheared dimple inner structures. Two types of impact experiments, including drawing and plane strain bending types, were performed via a drop impact tester. From the results of the experiments, the influence of impact conditions on the deformation behaviors, the force-deflection relationships and the energy absorption characteristics were investigated. The deformed shape of the inner structures were measured by the X-ray CT system. From the results of the measurement, it was shown that the excessive deformation of the dimple structures in the vicinity of the impacted region takes place and the deformation of the dimple structures in the outside of the impact region is negligible. In order to examine the performance of the ultra-light weight sandwich panel quantitatively, the impact characteristics of the designed panel were compared to those of SPFC 780 panel. The SPFC 780 panel is an advanced high strength steel, which are used in the bumper back beam. The results of the comparison showed that the energy absorption rate per mass of the ultra-light weight sandwich panel is higher than that of the SPFC 780 plane and the contact force of the ultra-light weight sandwich panel is lower than that of the SPFC 780 plane. In addition, it was noted that the deflection of the designed ultra-light weight sandwich panel is lower than that of SPFC 780 before the failure initiation of the deformable sheared dimple inner structures. Three-dimensional nonlinear finite element analysis was performed via a commercial code ABAQUS Explicit in a condition of the plane strain bending. Through the comparison of the results of experiments with those of the analysis, a proper FE analysis model was obtained. The initial time of the failure of the inner structures were estimated through the FE analysis. The results of the FE analysis showed that an initial time of the failure of the inner structures decreases when the impact energy increases. In addition, it was shown that the reaction force of the impact head decreases abruptly when the failure of the inner structures initiates. From the results of the FE analysis, the influence of the impact energy on the plastic strain, the effective stress and the plastic dissipation energy distribution in the ultra-light weight sandwich panel with deformable sheared dimple inner structures.