Foam-filled Conical Tubes Research Articles

Collapse behavior of thin-walled conical tube clamped at both ends subjected to axial and oblique loads

The structures of the vehicles during the crushing processes or accidents not only experience direct or axial collisions but sometime these structures are crushed off-axially. Therefore, it is very crucial to study whether or not a foam-filled tube is capable of supporting the oblique compression forces efficiently and effectively. In this paper, investigation of the axial and oblique loading collapse behavior of thin-walled conical tube clamped at both ends is presented. Several numerical simulations using ABAQUS finite element explicit code are carried out to study crashworthiness characteristics of empty and foam-filled thin-walled conical tubes clamped at both ends. In order to verify these numerical results, a series of quasi-static axial and oblique compression tests are performed. The validated finite element model was then used for the parametric studies, in order to determine the effect of the empty and filler tube geometry parameters (i.e. semi-apical angle) and loading parameters (i.e. load angle) on the energy absorption and mean crushing load. The primary outcome of this study is to provide information for the use of foam-filled conical tubes as energy absorbers where oblique loading is expected.

Experimental and Numerical Analysis of Foam-Filled Aluminum Conical Tubes Subjected to Oblique Impact Loading

AbstractThis study aims to investigate the response of AA6061-T6 conical tubes under oblique impact loading, for variations in filler density and tube material by using experimentally validated model. Good correlations between the numerical and experimental results were observed. The initial peak force and dynamic force increase from AA6061-T6 to carbon steel tubes and further increase with increasing filler density, leading to increased energy absorption capacity. Conversely, the initial peak force and dynamic force of empty and foam-filled AA6061-T6 conical tubes decrease with the introduction of oblique loading as the load angle increases from 0° to 20°, leading to reduced energy absorption capacity. Carbon steel is relatively more advantageous compared with AA6061-T6 in terms of energy absorption, whereas AA6061-T6 is comparable with carbon steel because of its lower initial peak force.

An Experimental and Numerical Analysis of Empty and Foam-Filled Aluminium Conical Tubes under Oblique Impact Loading

This paper presents the crushing behaviour of empty and foam-filled conical aluminium alloy (AA6061-T6) tubes under oblique impact loading using a validated nonlinear finite element (FE) code, LS-DYNA. The study aims to assess the beneficial of foam filling on the energy absorption in terms of mass reduction, for variations in filler density and geometrical parameters of AA6061-T6 tubes. The results obtained successfully identified the critical tube mass and critical foam density. It is evident that foam filling successfully induced high Specific Energy Absorption (SEA) value of foam-filled tubes thus proving that the assessment of critical total tube mass and critical foam density point is vital in identifying proper combination of tube-filler to the effectiveness of foam-filled tubes. The combination of AA6061-T6 tube and aluminium foam demonstrates pronounced SEA increase as high as 72.3% compared to the empty tube.

Multiobjective crashworthiness optimization of hollow and conical tubes for multiple load cases

Much attention of current design analysis and optimization of crashworthy structures have been largely paid to the scenarios with single load case in literature. Nevertheless the designed structures may often have to be operated in other load conditions, thus raising a critical issue of optimality. This paper aims to understand and optimize the dynamic responses and energy absorption of foam-filled conical thin-walled tubes under oblique impact loading conditions by using multiobjective optimization method. The crashworthiness criteria, namely specific energy absorption (SEA) and crushing force efficiency (CFE), are related to loading parameters and design variables by using D-optimal design of experiments (DoE) and Kriging model. To obtain the optimal Pareto solutions of hollow and foam-filled conical tubes, design optimization is first performed under different loading case (DLC) using multiobjective particle swarm optimization (MOPSO) algorithm separately. The optimal designs indicate that hollow tube has better crashing performance than the foam-filled tube under relatively high impacting velocity and great loading angle. To combine multiple load cases (MLC) for multiobjective optimization, a double weight factor technique is then adopted. It is found that the optimal foam-filled tube has better crashing performance than empty conical tube under any of overall oblique loading cases concerned. The study gains insights in deriving multiobjective optimization for multiple load cases, providing a guideline for design of energy absorber under multiple oblique loading.

Dynamic Axial Crushing of Empty and Foam-Filled Conical Aluminium Tubes: Experimental and Numerical Analysis

This paper presents the crushing behaviour of empty and foam-filled conical tubes under axial dynamic loading. A nonlinear finite element (FE) model was developed and validated against experiments. The validated model was subsequently used to assess the beneficial of foam filling with regards to the variation in filler densities and tube materials. The results obtained were further analyzed and compared with straight tubes. We aim to evaluate the critical effective point for different density of fillers in foam-filled tubes based on specific energy absorption (SEA) value. The SEA value was highest for foam-filled conical aluminium tube with aluminium foam filler, followed by straight aluminium tube, straight carbon steel tube and conical carbon steel tube. Moreover, the initial peak force was found lower in aluminium tubes than carbon steel tubes and lower in conical tubes than that in straight tubes. The combination of conical aluminium tube and aluminium foam filler successfully convey the beneficial of foam filling and thus signify that proper combination and selection of tube and filler is vital in assessing the effectiveness of foam-filled tubes.

Crushing characteristics of fiber reinforced conical tubes with foam-filler

In this paper, crushing force and energy absorption of foam-filled conical tubes with fiber reinforced layer between two metal walls under axial loading have been studied by means of an analytical method. Based on the axially crushing models, a simplified analytical solution for the static crushing of foam-filled fiber reinforced conical tubes is presented. The influences of fiber reinforced orientation, fiber layer thickness and base angle of conical tube on energy absorption capability were studied in examples. A validated finite element method was introduced to simulate the collapse of foam filled metal conical tubes and indirectly verified the feasibility of the simplified analytical model proposed in this paper.

Optimization of functionally graded foam-filled conical tubes under axial impact loading

Metallic foams as a filler in thin-walled structures can improve their crashworthiness characteristics. In this article, nonlinear parametric finite element simulations of FGF foam-filled conical tube are developed and the effect of various design parameters such as density grading, number of grading layers and the total mass of FGF tube on resulting mode shapes, specific energy absorption and initial peak load is investigated. Multi design optimization (MDO) technique and the geometrical average method, both are based on FE model are applied to maximize the specific energy absorption and minimize the impact peak force by estimating the best wall thickness and gradient exponential parameter “m” that controls the variation of foam density. The results obtained from the optimizations indicated that functionally graded foam material, with graded density, is a suitable candidate for enhancing the crashworthiness characteristics of the structure compared to uniform density foam.

Inclusion of Tapered Tubes in Enhancing the Crash Performance of Automotive Frontal Structures

This paper treats the design and analysis of an energy absorbing system. Experimental tests were conducted on a prototype, and these tests were used to validate a finite element model of the system. The model was then used to analyze the response of the system under dynamic impact loading. The response was compared with that of a similar system consisting of straight circular tubes, empty and foam-filled conical tubes. Three types of such supplementary devices were included in the energy absorbing system to examine the crush behavior and energy absorption capacity when subjected to axial and oblique impact loadings. The findings were used to develop design guidelines and recommendations for the implementation of tapered tubes in energy absorbing systems. To this end, the system was conceptual in form such that it could be adopted for a variety of applications. Nevertheless, for convenience, the approach in this study is to treat the system as a demonstrator car bumper system used to absorb impact energy during minor frontal collisions.

Experimental and numerical crashworthiness investigation of empty and foam-filled end-capped conical tubes

Foam-filled thin-wall structures exhibit significant advantages in light weight and high energy absorption. They have been widely applied in automotive, aerospace, transportation and defense industries. Quasi-static tests were done to investigate the crash behavior of the empty and polyurethane foam-filled end-capped conical tubes. Non-linear dynamic finite element analyses were carried out to simulate the quasi-static tests. The predicted numerical crushing force and fold pattern were found to be in good agreement with the experimental results. The energy absorption capacities of the filled tubes were compared with the empty end-capped conical tubes. The results showed that the energy absorption capability of foam-filled tube is somewhat higher than that of the combined effect of the empty tube and the foam alone. Finally, the crash performance of the empty and foam filled conical and cylindrical tubes were compared. Results from this study can assist aerospace industry to design sounding rocket carrier payload based on foam-filled conical tubes.

Dynamic energy absorption characteristics of foam-filled conical tubes under oblique impact loading

This paper treats the crush behaviour and energy absorption response of foam-filled conical tubes subjected to oblique impact loading. Dynamic computer simulation techniques validated by experimental testing are used to carry out a parametric study of such devices. The study aims at quantifying the energy absorption of empty and foam-filled conical tubes under oblique impact loading, for variations in the load angle and geometry parameters of the tube. It is evident that foam-filled conical tubes are preferable as impact energy absorbers due to their ability to withstand oblique impact loads as effectively as axial impact loads. Furthermore, it is found that the energy absorption capacity of filled tubes is better maintained compared to that of empty tubes as the load orientation increases. The primary outcome of this study is design information for the use of foam-filled conical tubes as energy absorbers where oblique impact loading is expected.

Application of foam-filled conical tubes in enhancing the crashworthiness performance of vehicle protective structures

This paper treats the feasibility of including a supplementary energy-absorbing device in the form of foam-filled conical tubes onto vehicular protective structures to enhance their energy absorbing capacity and hence to enhance safety for the occupants during accidental impacts. The effect of the supplementary energy absorber device was investigated for varying values of the wall thickness of the tube and the foam density of the filler. Research findings have shown the inclusion of this supplementary energy-absorbing device to be a cost-effective and beneficial solution, which promoted an enhanced level of occupant safety by enhancing the energy absorption, reducing the amount of plastic deformation sustained by the protective structure as well as reducing the severity of the peak decelerations transferred to the occupant compartment during such an event.

Dynamic computer simulation and energy absorption of foam-filled conical tubes under axial impact loading

This paper treats the dynamic response and energy absorption of aluminum foam-filled conical tubes under axial impact loading using non-linear finite element techniques. The influence of geometrical, material and loading parameters on the impact response is investigated using validated numerical models. Results are quantified in terms of important impact response parameters and indicate that the foam filler stabilizes the crushing process and thus improves the energy absorption capacity. The superior performance of foam-filled conical tubes as impact energy absorbers is evident from the results. The research information generated will be useful in developing guidance towards the design of these devices in impact applications.

Crushing response of foam-filled conical tubes under quasi-static axial loading

Foam-filled thin-walled tubes are considered to be desirable energy absorbers under axial loading due to their higher energy absorption compared with empty tubes. This paper treats the axial crushing and energy absorption response of foam-filled conical tubes under quasi-static axial loading, using non-linear finite element models. Influence of important parameters such as wall thickness, semi-apical angle and density of foam filler was investigated and the results highlight the advantages of using foam-filled conical tubes as energy absorber. Results also indicate that the crush and energy absorption performances of conical tubes are significantly enhanced by foam filling. The primary outcome of the study is new research information and development of empirical relations which will facilitate the design of foam-filled conical tubes as energy absorbers in impact applications.