Analisis Penyerapan Energi Dan Pola Deformasi Crash Box Dengan Variasi Sudut Tirus Dinding Crash Box Pada Uji Simulasi Tabrakan Arah Frontal

Sistem transportasi merupakan salah satu kebutuhan yang penting untuk dipenuhi dalam mempermudah kehidupan pada zaman modern ini. Di sisi lain, meningkatnya kebutuhan akan hal tersebut juga akan ikut meningkatkan produksi kendaraan yang secara tidak langsung turut meningkatkan jumlah kecelakaan. Meninjau hal tersebut, standar keselamatan kendaraan yang lebih baik sangat dibutuhkan, salah satunya adalah crash box. Crash box merupakan sistem keamanan pasif yang digunakan untuk mengurangi tingkat keparahan kecelakaan yang dialami penumpang atau bagian kendaraan yang vital akibat tabrakan. Penelitian ini meninjau pengaruh variasi sudut tirus dinding crash box berpenampang lingkaran (circular) terhadap pola deformasi dan penyerapan energi pada uji simulasi tabrakan arah frontal. Penelitian dilakukan dengan software berbasis metode elemen hingga (MEH). Variasi yang digunakan dalam penelitian ini yaitu crash box dengan sudut tirus (α) 0,2°; 0,4°; 0,6°; 0,8; dan 1,0° dengan material crash box baja AISI 1340. Dari hasil penelitian diperoleh bahwa pola deformasi yang terbentuk adalah pola aksial dengan mode concertina dan campuran (concertina + diamond). Deformasi mode campuran terjadi pada crash box t a 1,6 α 0,0°; α 0,8°; α 1,0°. Penyerapan energi meningkat seiring bertambah besarnya sudut tirus dinding crash box, dengan kemampuan menyerap energi terbesar pada crash box dengan sudut tirus (α) 1,0° sebesar 10823 J. Semakin besarnya sudut tirus dinding crash box juga menunjukkan peningkatan penyerapan energi spesifik crash box

Pengaruh Crash Box Berbentuk Tabung 2 Segmen Terhadap Kemampuan Menyerap Energi Impak Dengan Simulasi Komputer

Crash Box is a very important part as absorbing impact energy, especially in the frontal crash case. The purpose of this study was to determine the optimal design on two circular cross sections Crash Box to its ability to absorb impact energy and deformation pattern. The independent variable in this study were length, and thickness of the Crash Box with length of tube 1 (h ) = length of tube 2 (h 2 ) = 40, 50, 60 mm and thickness of tube 1 (t 201 1 1 ) = thickness of tube 2 (t ) = 2,5 ; 3 ; 3.5 mm were analyzed by the Taguchi method.The dependent variable is the energy absorbed and the deformation that occurs in Crash Box due to the impact test (Impactor) and is measured by using finite element-based software which is Ansys 14.5. Based on data from the simulation results, it can be obtained on one circular cross section Crash Box has the ability to absorb the energy of 2762.89 A. For optimum design of two circular cross sections Crash Box has the ability to absorb the energy of 4435.04 J. Optimum design of Crash Box has length of tube 1 (h 1 ) = 40 mm, length of tube 2 (h 2 ) = 60 mm, thickness of tube 1 (t ) = 3.5 mm, thickness of tube 2 (t ) = 3 mm. From the deformation pattern analysis, it can be seen that the deformation in the Crash Box can be divided into 2 types: Concertina mode (bending on the Crash Box walls is symmetric) and Diamond Fashion (bending on the Crash Box walls is not symmetrical)

Crashworthiness assessment considering the dynamic damage and failure of a dual phase automotive steel

Analyzing crash worthiness of the automotive parts has been posing a great challenge in the sheet metal and automotive industry since several decades. The present contribution will focus on one of the most urging challenges of the crash worthiness simulations, namely, an enhanced constitutive formulation to predict the failure and cracking of structural parts made from high strength steel sheets under impact. A hybrid extended Modified Bai Wierzbicki damage plasticity model is devised to this end. The material model calibrated using the experimental data covering high strain rate deformation, damage and failure successfully predicted the instability and subsequent response of the crash box under impact. Simulation results provide the deformation shape and deformation energy in order to predict and evaluate the vehicle crashworthiness. The simulations further helped in discovering the irrefutable impact of strain rate and stress state on the impact response of the auto-body structure. The strain rate is found to adequately affect the energy absorption capacity of the crash box structure both in terms of impact load and fold formation whereas the complex stress state has a direct association to the development of instability within the structure and early damage appearance within the folds

Application of functionally graded materials for severe plastic deformation and smart materials: experimental study and finite element analysis

Functionally graded materials (FGMs) refer to the composite materials where the compositions or the microstructures are locally varied so that a certain variation of the local material properties is achieved. Determination of compositional gradient and the process of making an FGM are dependent on its intended use. In this study, new possible applications of FGM and its production process were investigated. Three possible application of FGM were proposed. First, the novel technique in producing ultra fine grain of difficult-to-work materials by equal-channel angular pressing (ECAP) process at ambient temperature was developed by using FGM. For this study, Ti as the difficult-to-work material was tightly encapsulated in a hollow host material made of Al-based FGM matrix. The Al-based FGM as a host material assists the deformation of Ti. The ECAP process was simulated by the finite element method (FEM) to determine the appropriate compositional gradient of Al-based FGM and the position to embed Ti wire. FEM was conducted with Ti embedded into a different host material type as well as different die channel geometry. The strain distribution of the specimen after a single ECAP pass was analyzed. From the obtained results, it is found that the strain distribution in Ti is strongly influenced by the host material and the shape of the die channel. An experimental work was carried out to confirm the ability of the proposed technique in producing ultra fine grain of Ti. The host material was prepared by embedding Al-Al3Ti alloy into Al. Three types of the Al-Al3Ti alloys with different Al3Ti volume fractions were used to prepare the host materials. ECAP for specimens was carried out for up to eight passes by route A. The microstructure and hardness of ECAPed specimens were investigated. The changes in microstructure and the increase in the hardness value of Ti with increased number of ECAP passes are evidences showing that Ti is successfully deformed by this technique. Second, new types of FGM crash boxes with stepwise strength gradient in longitudinal directions were proposed. The property of the proposed FGM crash boxes were analyzed using FEM. Crash behavior of the crash box under axial quasi-static and dynamic impact loads were studied. The obtained load-displacement curves and the crash failure patterns then were evaluated to assess the effect of the stepwise strength gradient of the crash-box. II Moreover, four different shapes of cross-sectional i.e. square, circle, pentagon and hexagon were considered. The results show that the FGM crash box is superior to than the homogeneous crash box in overall crashworthiness. Although there were no trigger mechanism introduced, the FGM crash boxes experience the progressive crushing initiated at the impact side. Third, the FGMs were applied in pipe and pressure vessel field. A solution procedure for finite element thermo-visco-plasticity and creep analysis in an FGM thick-walled pressure vessel subjected to thermal and internal pressure was presented. The thick�walled pressure vessel was replaced by a system of discrete rectangular cross-section ring elements interconnected along circumferential nodal circles. The property of FGM was assumed to be continuous function of volume fraction of material composition. The thermo-visco-plasticity and creep behavior of the structures were obtained by the use of an incremental approach. The obtained results show that the material composition significantly affects the stress as a function of time at the inside and outside surface of thick-walled pressure vessel. The use of FGM can adjust the stress distribution in the structure. Moreover, one of the FGM fabrication method, centrifugal casting, was investigated. Two types of centrifugal casting method namely, centrifugal solid-particle method (CSPM) and centrifugal mixed-powder method (CMPM), were used to fabricate Al/SiC FGM. Formations of graded distribution of SiC particles within molten Al by CSPM and CMPM under huge centrifugal force were examined and simulated. The movement of SiC particles in viscous liquid under centrifugal force was explained theoretically based on Stoke’s law. The effect of composition gradient of particles on viscosity was taken into account. Also, the effect of temperature distribution on viscosity and density were considered. A computer code to simulate the formation of compositional gradient in an Al/SiC FGM manufactured by CSPM and CMPM was developed. From the obtained results, it was found that the SiC particles can be graded from inner to outer surface of Al/SiC FGM by CSPM. Meanwhile by CMPM, the SiC particles can be dispersed on the surface of Al/SiC FGM. The graded distribution in Al/SiC FGM under huge centrifugal force was significantly affected by the mold temperature but less affected by the initial temperature of molten Al and casting atmosphere

Pengaruh Variasi Geometri Crash Box 2 Segmen Terhadap Kemampuan Menyerap Energi Impak Dengan Simulasi Komputer

Crash box is a passive safety system placed on four wheeled vehicle, the purposes it to absorb the impact energy due to bumper no longer able hold the impact happened. There have been many studies done with the type of segment, so it needs development especially segment additional, and in this study of two segments of crash box is expected to absorb more energy, the additional of this segment purposes to increase the critical load so can be reduced the buckling. The method in this study used is ANSYS Workbench 14.5 finite element software. The variables used are the section type crash box geometry of circle, square, and hexagon, with cross section area of 1492 mm2, 1771 mm2, and 2045 mm2 and uniform height of 100 mm, the material used is aluminum AA 7003-T7. Simulation process begins when the impactor collision with speed 16 km/hour. From the research result is that moment inertia of the cross section area were able an important role in the absorption of impact energy, the cross section area 2045 mm2 were able to absorb the higher energy for each type of crash box, and the section of hexagon term that can absorb highest impact energy

Validating performance of automotive materials at high strain rate for improved crash design

This paper investigates sources of performance variability in high velocity testing of automotive crash structures. Sources of variability, or so called noise factors, present in a testing environment, arise from uncertainty in structural properties, joints, boundary conditions and measurement system. A box structure, which is representative of a crash component, is designed and fabricated from a high strength Dual Phase sheet steel. Crush tests are conducted at low and high speed. Such tests intend to validate a component model and material strain rate sensitivity data determined from high speed tensile testing. To support experimental investigations, stochastic modeling is used to investigate the effect of noise factors on crash structure performance variability, and to identify suitable performance measures to validate a component model and material strain rate sensitivity data. The results of the project will enable the measurement of more reliable strain rate sensitivity data for improved crashworthiness predictions of automotive structures

Crashworthiness modelling of hierarchical short glass fibres reinforced graphene polymer composites materials

This work aims to analyse the response under crashworthiness impact of an automotive crash box composite consisting on short glass fibres that are embedded within graphene reinforced polymer composite. Analytical as well as finite element techniques are employed to derive the overall composite response and mechanical characterisation for a macroscopic structural crashworthiness application. Graphene sheets are considered as platelets GPL embedded within an elasto plastic polymer matrix phase leading to a 2-phases graphene/polymer composite. The modelling of 3-phases short glass fibres/graphene polymer composite consists on a double-scale approach combining the 2-phases graphene polymer composite as matrix phase in which are embedded the glass fibres. The full structure crash box is simulated at each Gauss integration point by implementing the constitutive 3-phases composite using a user-defined materials subroutine

CRASH: a Radiative Transfer Scheme

We present a largely improved version of CRASH, a 3-D radiative transfer code that treats the effects of ionizing radiation propagating through a given inhomogeneous H/He cosmological density field, on the physical conditions of the gas. The code, based on a Monte Carlo technique, self-consistently calculates the time evolution of gas temperature and ionization fractions due to an arbitrary number of point/extended sources and/or diffuse background radiation with given spectra. In addition, the effects of diffuse ionizing radiation following recombinations of ionized atoms have been included. After a complete description of the numerical scheme, to demonstrate the performances, accuracy, convergency and robustness of the code we present four different test cases designed to investigate specific aspects of radiative transfer: (i) pure hydrogen isothermal Stromgren sphere; (ii) realistic Stromgren spheres; (iii) multiple overlapping point sources, and (iv) shadowing of background radiation by an intervening optically thick layer. When possible, detailed quantitative comparison of the results against either analytical solutions or 1-D standard photoionization codes has been made showing a good level of agreement. For more complicated tests the code yields physically plausible results, which could be eventually checked only by comparison with other similar codes. Finally, we briefly discuss future possible developments and cosmological applications of the code.Comment: 17 pages, 14 figures, accepted for pubblication in MNRAS, high res figures available at http://www.arcetri.astro.it/science/cosmology/IGM/radtrans.htm

Can One Make Any Crash Prediction in Finance Using the Local Hurst Exponent Idea?

We apply the Hurst exponent idea for investigation of DJIA index time-series data. The behavior of the local Hurst exponent prior to drastic changes in financial series signal is analyzed. The optimal length of the time-window over which this exponent can be calculated in order to make some meaningful predictions is discussed. Our prediction hypothesis is verified with examples of '29 and '87 crashes, as well as with more recent phenomena in stock market from the period 1995-2003.Some interesting agreements are found.Comment: LaTeX 2e, 7 figures (included), 17 page