Development of a Dropped Weight Impact Testing …

1 International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 06 98 115606-9393 IJET-IJENS @ December 2011 IJENS I J E N S Abstract This article presents the Development of a Dropped Weight Impact Testing machine. The machine was developed as a facility to provide experimental data to validate numerical simulations of Impact loads on crash boxes, parts of car structure that absorb kinetic energy during collision.

2 The Dropped Weight Impact machine was designed to produce Impact load to a specimen that represents a crash box. The machine was equipped with sensor systems to measure the velocity of the impactor just before it hit the specimen and the force that crushed the specimen, and with a data acquisition system to record the crushing force for further analysis. The Development process included the design, fabrication, and function tests of the machine. The function tests performed after the machine was built indicated that the Dropped Weight Impact Testing machine can fulfill the design objectives.

3 Results of several experiments using specimens in form of columns with square, hexagonal, octagonal and circular cross sections showed that the experimental results are in good agreements with the results of Impact simulations carried out using Finite Element Method. Index Term Crash box, design, Impact load, experiments. I. INTRODUCTION One of the main concerns in traffic safety nowadays is the improvement of the vehicle crashworthiness. To increase passenger safety, some parts of automotive structure known as crash boxes are designed to absorb kinetic energy during collision.

4 These components are usually in the form of columns which will undergo progressive plastic deformation during collision. The crushing force, the force needed to deform the crash box, determines the deceleration of the vehicle during collision and indicates the capability of the crash box to absorb kinetic energy. The value of crushing force is determined by the geometry and the material of the crash box. Several researches on the analyses of buckling behavior of prismatic columns under low velocity Impact have been reported for several years [1, 2, 3, 4, 5, 6].

5 These earlier studies explored columns of different materials and geometries which were unrelated from one to another. Hence, it is not easy to obtain certain relation between columns geometry and material with their capability to absorb Impact energy. Practical researches that produced usable design rules are limited. Further, for columns made of aluminum, which is of LeonardoGunawan is with the Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Bandung 40132, Indonesia ( e-mail: Tatacipta Dirgantara is also with the Faculty of Mechanical and Aerospace Eng.)

6 , ITB, Bandung 40132, Indonesia (e-mail: Ichsan Setya Putra is also with the Faculty of Mechanical and Aerospace Eng., ITB, Bandung 40132, Indonesia (e-mail: importance in the future due to its high strength to Weight ratio, only a few results have been published. From these considerations, systematic studies on energy absorption capacity of prismatic aluminum columns under low speed Impact were carried out [7, 8, 9, 10, 11]. In these studies, behavior of aluminum columns subjected to axial Impact load were numerically analyzed using explicit finite element method.))

7 Parameters considered in this study were cross section geometry and wall-thickness to perimeter ratio. Fig. 1 shows a result of numerical simulation of an aluminum circular tube subjected to axial Impact load [7]. To verify the results of these numerical studies, an Impact Testing machine based on Dropped Weight principle was developed. The Impact speed obtained from this principle is limited by the dropping height. However, the range of the Impact speed still fulfills the low speed criteria. Moreover, its Development and operation cost is low.

8 This article presents the design and Testing of this machine. II. DESIGN OF LOW VELOCITY Impact Testing MACHINE A. Design Objectives The Impact Testing machine was designed to perform low speed Impact tests, Impact velocities less than 15 m/s. At each Impact speed, the kinetic energy should be able to be varied. The machine should be able to accommodate Impact tests on specimens of various cross sectional geometry with maximum outer geometry of 60 mm and maximum height of 170 mm. Other considerations in design were the safety and cost aspects.

9 B. Conceptual Design An Impact machine based on Dropped Weight principle was selected since it is able to provide Impact velocity by using earth gravity. This machine is a cost effective solution compared to that using a gas gun. In the design, a specimen was fixed on top of a steel base. An impactor was elevated and then released at a certain height above the specimen. The impactor would hit the specimen with an Impact speed that depends on the dropping height. The kinetic energy of the impactor was then absorbed by the progressive folding of the specimen wall, which reduced the kinetic energy of the impactor until it finally stopped.

10 Development of a Dropped Weight Impact Testing Machine Leonardo Gunawan, Tatacipta Dirgantara, and Ichsan Setya Putra International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 06 99 115606-9393 IJET-IJENS @ December 2011 IJENS I J E N S The crushing force of the specimen during the Impact was sensed by using a load cell which was placed between the specimen and the steel base.