Impact Testing Setup for Knowledge Based Crash Box Design to Improve Vehicle Safety
Car safety is studied widely today because of the fact there are many car accidents happening everyday and large number of people are dead or injured in car crashes. To protect occupants during those events, car safety should be increased by several approaches such as using more safety devices, improving car structure, etc. From mechanical aspect, well designed structures are the most common field to dig in. As long as passengers’ compartment could not be deformed and intrusion could be avoided during accident, car structure is said to be safe. In order to withstand shock load, vehicle structure must have specific stiffness. However, the more important point is the structure must be able to reduce the force transferred to passengers’ compartment by forming the energy absorption reaction. Normally, the two main longitudinal members in the frontal part of the car structure will absorb most of the impact energy with a progressive folding deformation of steel column. These frontal members are called crash-box and could be adjusted to limit the impact load at occupants’ section. Due to that importance, the energy absorbing characteristics, deformation mechanism and failure of structural members during collisions have been conducted and investigated by a number of researchers in both numerical and experimental studies.
Within the Light Weight Structures and Materials Research Group, Faculty of Mechanical and Aerospace Engineering ITB, numerical simulations have been performed to analyze energy absorption of tubes with different geometry, materials and configurations. The purpose of the study is to provide a good and reliable data of energy absorption characteristics of different crash box. The data can be used by vehicle designers to determine suitable geometry, materials and configurations of crash box.
To validate and to improve the numerical impact simulations by some experimental data, a test setup was developed. The development took place in two years. The design of the test setup, the development and the verification of the load sensor were carried out in the first year (2009). The construction and functional test of the setup were performed in the second year (2010).
A test setup based on the free-fall (gravity) principle was chosen due to its simplicity. The height of the drop tower and the maximum mass of the impact head were determined by considering the requirement of the impact test such as the maximum velocity and the kinetic energy of the impact. The setup was designed and developed by utilizing available components in the local market.
After the setup had been constructed and instrumented, the setup were validated by carrying out some impact tests on several tubes as specimens. The results were compared to results of other researcher, and also compared to results of numerical impact analysis of those tubes.
Impact tests have been performed on tubes with square, hexagonal, octagonal, and circular cross section. Mean crushing forces of those tubes showed some differences compared to those obtained from analytical model. The imperfection of the tube due to welding process contributed to those differences. When the welding bead and the heat affected zone were modeled in numerical analysis, the discrepancies were reduced. There are still differences between experimental and numerical data, however the difference is comparable to those of other researchers. Hence the setup is now ready to be used to measure crushing force of tubes of different geometries and materials.
Currently only load sensor is employed in the setup, and measured data is presented in the form of load time history. Since crushing force analysis is based on energy principle which needs information of force vs displacement, the setup should also be equipped with a displacement sensor. By combining time histories of force and displacement, such a force vs displacement data can be measured from experiments.
A low velocity impact machine has been designed and built. It is used to provide experimental data to support numerical modeling of crash box. The setup has been verified by performing impact tests on some specimens and comparing the results to those of other researcher and to results of numerical analysis.
Further improvement to the impact machine still necessary to make the machine capable to provide force vs displacement data.
LIST OF RESEARCH OUTPUT
- “Development of Load cell for Low Velocity Axial Impact Testing”, Proceeding of Regional Conference on Mechanical and Aerospace Technology (RCMEAE 2010), Faculty of Mechanical and Aerospace Engineering – ITB (Bali, February 9 – 10 2010)
- “Low Velocity Impact Analysis of Prismatic Columns using Type Finite Element Method”, Proceeding 8th International Conference on Fracture and Strength of Solids 2010, Far East and Oceanic Fracture Society (Kuala Lumpur, Malaysia, June 7-9 2010)
- “ Analisa Impak Kecepatan Rendah pada Tabung PVC Menggunakan Metode Elemen Hingga”, Proceeding Seminar Nasional Tahunan Teknik Mesin IX, 2010, Badan Kerjasama Teknik Mesin Indonesia (Palembang, Oktober 13-15 2010)
- Prototype: Low Impact Testing Machine for measuring the crushing force of tubes at different
HEAD OF RESEARCH TEAM: Dr. Leonardo Gunawan
TEAM MEMBERS: Prof. Ichsan Setya Putra, Dr. Tatacipta Dirgantara
OFFICIAL ADDRESS: Lightweight Structure Research Group, Faculty of Mechanical and Aerospace Engineering, ITB