Foam-filled Tubes Research Articles

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.

Fabrication of Aluminum Foam-Filled Thin-Wall Steel Tube by Friction Welding and Its Compression Properties.

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube.

A Study on Bending Behaviours of Aluminium Foam-Filled Tubes

In the study, the strengthening effect of aluminium foam in thin-walled aluminium tubes subject to bending load in investigated experimentally and numerically. Bending tests are conducted on foam filler, hollow tube and foam-filled tube. The finite element method is used as well to get deeper insight into the crush failure modes via focusing on the influence from wall thickness of the tube. The obtained information is useful to optimally design foam-filled tubes as energy absorbing devices in automotive engineering. The optimisation results can be implemented to find an optimum foam-filled tube that absorbs the same energy as the optimal hollow tube but with much less weight.

Experimental Evaluation of Novel Foam-Filled Energy-Absorbing Composite Tubes

Experimental Evaluation of Novel Foam-Filled Energy-Absorbing Composite Tubes

Investigating the quasi-static axial crushing behavior of polymeric foam-filled composite pultrusion square tubes

The capability of structures to absorb large amounts of energy is a crucial factor, particularly for structural components of vehicles, in reducing injury in case of collision. In this study, an experimental investigation was conducted to study the crashworthiness of polymeric foam-filled structures to the pultruded square cross-section E-Glass fiber-reinforced polyester composite tube profiles. Quasi-static compression was applied axially to composite tubes to determine the response of the quasi-static load displacement curve during progressive damage. Three pultruded composite tube wall thicknesses at different sizes were examined, and the effects of crushing behavior and failure modes were analyzed and discussed. Experimental results indicated that the foam-filled profile is superior to the non-filled foam composite tube profile in terms of the capacity to absorb specific energy.

Crushing analysis of foam-filled single and bitubal polygonal thin-walled tubes

Foam-filled thin-walled structures have drawn considerable attention and been widely applied in automotive and aerospace industries for their significant advantages in high energy absorption and light weight. This paper aims to compare the energy absorption characteristics of foam-filled single and bitubal polygonal tubes with different cross-sectional configurations under different axial crushing load conditions. The coupled finite element method (FEM) and element free Galerkin method (EFGM) are applied in modeling the foam-filled tubes for their interaction associated with large deformation, failure and damage. By the complex proportional assessment (COPRAS) technique – the multicriteria decision-making method, the comparisons of energy absorption characteristics of the considered single and bitubal polygonal tubes are conducted herein, respectively. The results show that the foam-filled circular bitubal column has outstanding energy absorption characteristics under all the conditions considered. It is found that the mean crushing force and energy absorbed generally increase with the increase in the edge number of foam-filled bitubal columns. The multiobjective optimization of foam-filled circular bitubal tube is finally conducted by using Non-dominated Sorting Genetic Algorithm (NSGA-II) for the maximization of specific energy absorption (SEA) and the minimization of peak crushing force (PCF).

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.

Response of Filled Thin-Walled Square Tubes to Axial Impact Load

This paper presents the results of an investigation into the response of thin-walled square (60x60 mm and 76x76 mm) tubes made from mild steel filled with four different fillers; aluminium foam (Cymat 7%), two types of aluminium honeycomb and polyurethane foam to quasi-static and dynamic axial impact load. The energy absorption characteristics of the foam-filled tubes are compared to that of a hollow tube, through efficiency calculations. The tubular structures are subjected to axial impact load generated by drop masses of 320 kg and 390 kg released from a height ranging between 2.1 m to 4.1 m. Footage from a high speed camera is used to determine the average crush forces exerted by each specimen. The results show that the fillers have insignificant effects on the initial peak forces based on the quasi-static results but increase the overall mean crushed force. The findings also indicate that the fillers affect at times the size of the lobe formed thus compromising the energy absorption capacity of the tube.

Manufacturing and bending behaviour of in situ foam-filled aluminium alloy tubes

The manuscript focuses on manufacturing of new in situ foam-filled tubes (in situ FFTs) of Al-alloys including the foaming stage and studying their mechanical behaviour under quasi-static and dynamic bending loadings. The composite structures were manufactured by the powder compact foaming technique. These structures are fabricated by heating foamable precursor material pieces above their solid temperature inside thin-walled tubes. Different manufacturing parameters were appropriately adjusted based on preliminary experiments. The mechanical crushing behaviour and failure mechanisms were assessed by three-point bending experiments supported by infrared thermography. The bending performance of in situ FFTs and ex situ foam-filled heat treated tubes (ex situ FFTTs) were compared with that of empty tubes subjected to heat treatment. The observed results have been explained in terms of the structural changes in the thermally treated tubes, the surface roughness derived from oxidation, and the dimensions of the interface gap between the two components in the composite structures. The in situ FFTs composite structures confirmed stable and controllable deformation and a promising energy absorption capability.

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.

Parametric analysis and multiobjective optimization for functionally graded foam-filled thin-wall tube under lateral impact

Foam-filled thin-walled tubes have proven an ideal energy absorber in automotive industry for its extraordinary energy-absorbing ability and lightweight potential. Unlike existing uniform foam (UF), this paper introduces functionally graded foam (FGF) to fill into the thin-walled structure subjected to lateral impact loading, where different configurations of foam grading (axial FGF and two transverse FGFs) are considered. To systematically investigate the bending behavior of this novel structure, numerical model is established using nonlinear finite element analysis code LS-DYNA and then is validated against the experiment. Through parametric study, it is found that the FGF tube absorbs more energy but may produce larger force than the UF counterpart. In addition, various parameters have a considerable effect on the crashworthiness performance of the FGF filled tube. Finally, multiobjective optimizations of UF and FGF filled columns are conducted, aiming to improve the specific energy absorption (SEA) and reduce the maximum impact force simultaneously, based upon the multiobjective particle optimization (MOPSO) algorithm and Kriging modeling technique. The optimization results show that all the FGF filled tubes can produce better Pareto solutions than the ordinary UF counterpart. Furthermore, the axial FGF tube provides better energy absorption characteristics than the two types of transverse FGF tubes.

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.

Crashworthiness and lightweight optimisation of thin-walled conical tubes subjectedto an oblique impact

Two major requirements for a vehicular system's crash components are being lightweight and having good crashworthiness. Thin-walled round and conical tubes, which are either empty or foam filled and that can potentially be used as the front rails of a passenger car subjected to oblique impact, are numerically analysed using the finite element method. The conical tube was found to have the best performance in terms of both specific energy absorption and peak crushing force. A maximum of 106.6% increase in the specific energy absorption was observed for the empty conical tube than the foam-filled round tube in the load angle range of 0°–30°. Using the Kriging metamodels with a maximum relative error less than 4%, multi-objective design optimisation of the conical tube was performed with a weight constraint of 0.2 kg. Lightweight and improved crashworthiness were obtained simultaneously for the conical tube through optimisation. It was also found that the optimal tube configurations differ for different impact angles. However, including multiple load angles in the multi-objective design optimisation process is feasible and could result in improved robustness of the tube against oblique impact.

Crush Response of Polyurethane Foam-Filled Aluminium Tube Subjected to Axial Loading

In this paper, the experimental investigation of polyurethane (PU) foam-filled into circular aluminum tubes subjected to axial crushing was presented. The purpose of this study is to improve the energy absorption of aluminium tube under axial quasi-static load. The aluminium tube was made from the AA6063-T5 aluminium alloy tubes. Each tube was filled with polyurethane foam. The density of foam was varied from 100, 150 and 200 kg/mP3P including with empty tube. The range of diameter/thickness (D/t) ratio of tube was varied from 15-55. The specimen were tested by quasi-static axial load with crush speed of 50 mm/min using the 2,000 kN universal testing machine. The load-displacement curves while testing were recorded for calculation. The mode of collapse of each specimen was analyzed concerning on foam density and the influence of D/t ratio. The results revealed that the tube with foam-filled provided significantly increment of the energy absorption than that of the empty tube. While the density of foam and D/t ratios increase, the tendency of collapse mode is transformed from asymmetric mode to concertina mode.

Impact Response of Circular Aluminum Tube Filled with Polyurethane Foam

The behavior of foam-filled thin-walled aluminum tube under impact was investigated focusing on different crashworthiness parameter. The diameter to thickness of tube ranging between 26.5 and 200 were filled with polyurethane foam density from 100­250 kg·m13. The specimens were crushed by a drop hammer. The result from finite element simulation and experiment was compared and good agreement was achieved. The simulation was also used to conduct further investigation on tube with higher diameter to thickness ratio. It was found that by filling foam, the tubes change their collapse modes from asymmetric mode to axisymmetric mode. Also, the energy absorption can be enhanced by filling tube with higher foam density. The impact energy was found to be managed more efficient in foam filled tube as the load efficiency is higher in higher density foam-filled tube. However, the specific energy absorption of foam-filled tube is getting lower in higher density foam. This paper provides experimental and numerical data as well as discussion in various aspects of crashworthiness. [doi:10.2320/matertrans.M2013293]

Axial Crushes Simulation of Thin-walled Square Aluminum Alloy 6061-T5 Foam-filled Section

This paper deal with numerical study of the dynamic impact of axial crushing on thin-walled extrusion aluminum alloy 6061 and polystyrene foam-filled tubes square cross-section. Non-linear dynamic-impact simulation was done using finite element software's package as well on foam-filled model. Non-linear dynamic finite elements were carried out to simulate buckling and crushing phenomenon in the crushed event. Influence of fillers on the energy absorption behavior of square and thin-walled metal tube extrusion aluminum alloy 6061 estimates empty and foam-filled examined. Three main decay modes have been identified for the model is crushes, for example, diamond compound symmetry, axisymmetric concertina mode of formation and mixing times. Three different arrangement foam-filled inner tube columns has been examined and investigated.

Off-Axis Crushes Simulation of Thin-walled Tapered Tubes Inserted with Foam-filled Structures

In this study deal with numerical analysis of the impact dynamic effects of crush performance of the tapered cross-section tubes, containing straight, single taper, double taper, taper triple and fourth tapered lightweight polyurethane foam filled alloy steel thin-walled tube. Foam-filled thin-walled tubes have been examined numerically. Off-axis angle load dynamic effects in front of crash were examined at an angle of 0, 5, 10, 15 and 20 degrees. Numerical analysis has been verified by experimental studies in place to validate the data. The results show that the energy absorption capacity has been significantly affected tube with various oblique angle, impact velocity and wall thickness. It was found that the foam filling in a thin-walled tubes increase the amount of energy absorbed compared with empty tubes.

Effect of triggering and polyurethane foam-filler on axial crushing of natural flax/epoxy composite tubes

In this study, empty and polyurethane-foam filled flax fabric reinforced epoxy composite tubes were longitudinally crushed under quasi-static compression. The effects of foam-filler (density of 160kg/m3, two diameters of 64 and 86mm), tube thickness (2, 4 and 6 plies of laminate), and triggering (45° edge chamfering) and the combination of triggering and foam-filler on the crushing characteristics and energy absorption capacity of these tubes were investigated. The test results indicate that the observed primary failure mode was progressive crushing for all the specimens. Foam-filled tubes have better crashworthiness than empty tubes in total absorbed energy, specific absorbed energy and crush force efficiency. The presence of triggering has no significant effect on total absorbed energy and specific absorbed energy of the empty tubes. However, the crush force efficiency of triggered tube is significantly larger compared to the non-triggered one. In addition, the triggering minimises the force variation of the tubes from the average crush force and in turn a more stable progressive crushing is achieved. The foam-filled and triggered tubes have better crashworthiness than the empty tubes in all the aspects. Compared with either triggered or foam-filled tubes, the triggered and foam-filled tubes have larger values in average crush load and crush force efficiency. In terms of total absorbed energy and specific absorbed energy, the triggered and foam-filled tubes have values always larger than those of the tubes with triggering only, but these values are either larger or smaller than the tubes with foam-filler only.

Dynamic and quasi-static bending behaviour of thin-walled aluminium tubes filled with aluminium foam

This paper aims to evaluate the potential use of closed-cell aluminium alloy integral-skin foams as stiffening elements for aluminium alloy thin-walled structures that are main basic components in the concept and design of automotive body parts. Foam specimens were prepared using the powder metallurgical route, inserted into empty thin-walled tubes and subjected to quasi-static and dynamic bending loading conditions. The effect of introducing foam into tubes was evaluated using the infrared thermography during the three-point bending tests. The foam-filled tubes, empty tubes and foams are compared in terms of the maximum load carrying capacity, crash energy absorption, specific energy absorption and deformation modes. Results showed that the foam filling leads due to interaction between the tube wall and foam filler, causing an increased bending response of the filled tubes which exceeds the sum of the bending response for the individual components. Their deformation mode is a combination between the modes of the individual components.