Energy Absorption and Deformation Pattern Analysis of Crash Box with Tapered Wall Angle and Trigger Circles under Quasi-Static Loading

ABSTRACT


Introduction
World health organization (WHO) provides a report with a title of the global report on road safety 2018, containing reports of traffic accidents in 175 countries.In this report, Indonesia is the third-ranked country in Asia in the death numbers due to traffic accidents after China and India which amounted to 31,726 [6].Increasing traffic density, which results in high traffic accidents, encourages decision makers to consider and use safety as a major research topic in the field of vehicle technology.In the production process, car components go through a more complex and complicated process which has implications for quite high costs.This also applies to the repair process if the car is damaged in an accident.Therefore, a safety tool is used that can reduce damage in the event of an accident, where this tool is included in a passive safety system.Crash box is a passive safety system technology that has been studied a lot lately, because its function is to absorb kinetic energy when a car collides in the event of an accident, both front and rear collisions.Crash boxes are designed to reduce the occurrence of forces acting on the entire vehicle structure during a collision.Therefore, a crash box device is installed between the support and the vehicle frame because it functions as an energy absorbing component.Velmurugan et al. (2009) conducted a study on the specific energy absorption characteristics of tubes with circular, square and rectangular sections.The energy absorption results for tubes with circular cross-sections were higher than for tubes with square and rectangular cross-sections [5].Choiron M.A. et al. (2015) conducted a study on circular cross-section crash boxes by varying the tapered wall angle (α) 0.2°; 0.4°; 0.6°; 0.8°; and 1.0° for energy absorption and deformation patterns by obtaining the greatest energy absorption results found in the crash box model with a tapered wall angle of α 1.0° of 10823 J [4].Nasution A. Y. et al. ( 2023) also conducted research on the energy absorption of crash boxes with a combination of frustrated shapes, cross sections and trigger circles.The energy absorption results were 142.66 kJ at 0.005 s, load 5728 kN and displacement 57 mm [2].It is from this background that further research is needed to obtain better energy absorption capabilities in the event of an accident.In addition, it can be determined that the optimal deformation behavior of the crash box in greater energy absorption.The development of increasingly advanced technology, numerical simulations can be used to predict the amount of energy absorption and deformation pattern of the crash box before conducting experimental research.With a circular cross section model combined with tapered wall angles and trigger circles in the hope of getting optimal energy absorption to reduce the impact of the collision.

Methods
The research method was quasi-experimental, namely by computer simulation using FEM-based (Finite Element Method) which aimed to predict the results of experiments to be used as references to conduct real experiments.The Crash Box in this study was the crash box of a tapered wall angle and trigger circles circular cross section as follows;

Geometric speciment
In this study, a crash box model was used with circular tubes which had trigger circles with tapered angle variations on the wall.Geometry has diameter = 100 mm, thickness = 2 mm and length = 100 mm as shown in the Figure1.

Material model
The crash box and impactor materials used in this study are Aluminum 6061-T4 with a bilinear isotropic hardening plasticity model and Structural Steel.The material properties taken from data by Choiron M A [3].

Finite element model
The finite element analysis software MSC Patran 2022 is used to carry out the numerical simulation analysis.Crash box model consists of three parts: the impacting rigid plate, the flexible crash box and fix support condotion, as shown in figure 2. In this modeling, the impactor position has no distance from the crash box and the impactor load velocity of 5 mm/s until 64 mm final deformation is obtained.In this study are 2 mm and automatic mesh was used to mesh crash box and impactor sequentially.

Results and Discussion
The amount of energy absorption from each model due to load can be seen in Table 3 and the deformation patterns are shown in Figure 4-6.The energy absorption E a value based on Table 3 can be sorted into 3 models from the largest, namely models 1, 5, and 7.The energy absorption values of the three models sequentially can be written as follows 3124.0J, 3101.7 J and 3072.8J.The magnitude of the energy absorption value is influenced by the P mean value and changes in the length of the specimen.The P mean values for the three models are 48236.39N, 47807.22N, and 47505.05N respectively, indicating that the order of magnitude of energy absorption corresponds to the order of the P mean values.The value of the change in length also affects the value of energy absorption, but because there is no significant difference in the value of the change in length in the three models, the change in length can be assumed to be the same.Thin-walled tubes or crash boxes have four possible deformation patterns when subjected to quasi-static loading, namely concertina (axisymetric), diamond (non-axisymetric), mixed mode, and Euler buckling.Deformation pattern is analyzed based on visual observations on the simulation results.The deformation pattern on the simulated crash box is set as 64 mm final displacement.

Figure 1 .
Figure 1.Crash box designThe parameter design of this study are the crash box circular geometry with variation tapered angle and location of trigger circles.All model specifications are shown in Table1

Figure 2 .
Figure 2. Meshing and testing model

Table 1 .
Parameter design

Table 2 .
Parameters for Aluminium 6061-T4 and Structural Steel

Table 3 .
Energy absorption value due to load

Table 4 .
Deformation pattern of crash box