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The main aim of this numerical study is to investigate the energy absorption behaviour of empty and foam filled AA7075 tubes during impact loading. In order to achieve this aim, the material model for Aluminium foam was based on crushable foam model, which was originally proposed by Deshpande and Fleck. The material model for AA7075 tube was taken...
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In this study, a new numerical approach based on CT-scan images and finite element (FE) method has been used to predict the mechanical behavior of closed-cell foams under impact loading. Micro-structural FE models based on CT-scan images of foam specimens (elastic-plastic material model with material constants of bulk aluminum) and macro-mechanical...
Citations
In the current numerical study, axial quasi-static crashworthiness performance of circular crash-boxes having the same geometry but made up of various frequently used wrought aluminium alloys is investigated using ABAQUS/Explicit. All the considered crash-boxes showed a stable progressive axi-symmetric collapse. Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), one of the most widely used Multi-Criteria Decision-Making (MCDM) techniques, is then employed to determine the most suitable aluminium alloy for the application of a crash-box in an automobile. It is found that, out of the considered aluminium alloys AA 6060 T4 is the most suitable aluminium alloy to be used as a crash-box in an automobile.KeywordsAluminium alloy tubesCrash-boxCrashworthinessCrush force efficiencyEnergy absorptionTOPSIS
Crash-box is an essential passive safety device in an automobile that absorbs the kinetic energy of an external impact during an accident, thereby improving passenger safety. Selecting a suitable material for fabricating a crash-box to maximize its crashworthiness performance is a critical issue and is a multi-attribute decision-making (MADM) problem. This study focuses on choosing an appropriate aluminium alloy for a crash-box out of 16 different frequently used wrought aluminium alloys considered as alternatives based on eight crashworthiness performance indicators used as attributes by taking the opinions of three decision-makers (DMs). The effect of varying the material of thin-walled circular crash-boxes with identical geometry is first examined by simulating their axial quasi-static collapse using ABAQUS/Explicit. Various crashworthiness performance indicators obtained from these simulations are used for the decision-making process. While taking a decision, the opinions of several DMs from varied backgrounds are generally considered. A systematic approach is proposed to determine the importance of each DM involved in group decision-making situations by considering their credentials, such as educational qualification, work experience, etc., using a ranking based MADM technique known as ‘R-Method’. Opinions of multiple DMs are then combined to come up with a single final decision, called a consensus. The application of the R-Method is discussed in detail to derive consensus in a group decision-making environment. The aluminium alloy AA 7075 T6 is the best, while AA 3003 H12 is the least preferred material for manufacturing a crash-box of the considered geometry as per the proposed method.
Imperfections associated with the geometric features of any component are inevitable during its fabrication and some of those can even have a drastic impact on its functionalities. One such case arises while fabricating one of the essential passive safety devices in an automobile called as 'thin-walled collapsible energy absorbers'. Thin-walled collapsible energy absorbers also known as crash-boxes are the tubular shell structures located in between the bumper and front side rails of an automobile. Crash-boxes collapse in a stable progressive manner to absorb kinetic energy of an external impact to protect the occupants during an accident. Tubular crash-boxes are generally manufactured by extrusion. Geometric imperfections in the form of irregularities in the shell thickness may be induced during extrusion of the crash-boxes. The present study aims to gauge the effects of irregularities present in the thickness of the extruded crash-box on it’s crashworthiness performance, numerically. Cylindrical aluminium alloy tubes are modelled as crash-boxes using ABAQUS/Explicit. The irregularities in the thickness of the tubular crash-box are modelled with the help of three different imperfect models. In every imperfect model, maximum variation in the thickness is kept within the tolerance value, provided by the standards DIN EN-755-9. The quasi-static axial collapse of these ‘imperfect’ cylindrical tubes is simulated and their crashworthiness performance indicators are compared with those of an ‘ideal’ circular crash-box. It is seen that the energy absorption and the mean crushing force reduced drastically due to these shell thickness irregularities in comparison to the ideal model. It is also observed that the mode of collapse of the circular tube changed from axi-symmetric concertina mode to the diamond mode due to irregularities in their thickness. Such significant change in the crashworthiness performance of crash-box may lead to a huge disaster in terms of human lives. Hence, crash-boxes should be fabricated carefully with more tight geometric and dimensional tolerances.
