A.G. Hanssen

Experimental and numerical studies of foam-filled sections

A comprehensive experimental and numerical studies of the crush behavior of aluminum foam-filled sections undergoing axial compressive loading is performed. Non-linear dynamic finite element analyses are carried out to simulate quasi-static test conditions. The predicted crushing force and fold formation are found to be in good agreement with the experimental results. Based on the numerical simulations, simple closed-form solution is developed to calculate the mean crushing force of the foam-filled sections. It is found that the increase of mean crushing force of a filled column has a linear dependence with the foam compressive resistance and cross-sectional area of the column. The proposed solution is within 8% of the experimental data for wide range of column geometries, materials and foam strengths.

Validation of constitutive models applicable to aluminium foams

An extensive experimental database has been established for the structural behaviour of aluminium foam and aluminium foam-based components (foam-filled extrusions). The database is divided into three levels, these are: (1) foam material calibration tests, (2) foam material validation tests and finally (3) structural interaction tests where the foam interacts with aluminium extrusions. This division makes it possible to validate constitutive models applicable to aluminium foam for a wide spectrum of loading configurations. Several existing material models for aluminium foam from the literature are discussed and compared. To illustrate the use of the database, four existing material models for foams in the explicit, non-linear finite element code LS-DYNA have been calibrated and evaluated against configurations in the database.

Close-range blast loading of aluminium foam panels

Full-scale field tests have been carried out in order to investigate the behaviour of aluminium foam panels subjected to blast loading. Charges were detonated at a given standoff distance in front of the foam panels, which were attached to the bob of a ballistic pendulum. Using this test set-up, the maximum swing of the pendulum after each test was used to calculate the energy and impulse transfer from the blast loading. Tests were carried out by varying the foam panel density and charge mass. Experiments were also done with an aluminium cover plate attached to the front of the foam panels. In general, it was observed that the energy and impulse transfer to the pendulum increased by adding a foam panel. In order to investigate this phenomenon, an analytical solution based on shock-wave theory was proposed in order to describe the deformation behaviour of a one-dimensional foam bar subjected to a linearly decaying blast loading. However, using this approach, it was found that the addition of a foam bar should not change the global response of the pendulum. On the other hand, similarities between the present case and recent investigations reported in the literature suggest that the observed increase in maximum swing of the pendulum when adding foam panels may be due to the continuous changing of the shape of the initially plane panel surface into a concave shape. In this way, surface effects could be controlling the energy and impulse transfer.

Static crushing of square aluminium extrusions with aluminium foam filler

An experimental investigation was carried out to study the behaviour of square aluminium extrusions filled with aluminium foam under quasi-static loading conditions. Based on the experimental work, simple relations between dimensionless numbers governing the influence of the foam on the characteristics of the crush problem were identified. Furthermore, a simplified set of equations applicable for design of foam-filled components was proposed.

Crash behaviour of thin-walled aluminium members

In order to assess the crashworthiness of aluminium extrusions, a research programme was carried out in co-operation with the aluminium industry in Norway. The main objective was to study the behaviour of aluminium extrusions under axial loading conditions and to give experimental data for validation of a numerical model in the computer code LS-DYNA. In order to increase the energy absorbing capabilities of thin-walled aluminium members under axial loading, an experimental investigation was performed to study the combined behaviour of extrusions and aluminium foam.

Optimum design for energy absorption of square aluminium columns with aluminium foam filler

The performance in axial compression of square aluminium columns with aluminium foam filler has been assessed based upon existing design formulas for average crush force, maximum force and effective crushing distance. Using an optimisation algorithm, the combination of (1) foam density, (2) column wall thickness, (3) column width, (4) column material strength and (5) total component length giving the component of minimum mass was determined for specific cases. It was found that optimum foam filled columns compared to the traditionally designed non-filled columns showed smaller cross section dimensions in addition to less weight. As a consequence, mass-, length- and volume reductions are possible by utilising foam filler.

Bending of square aluminium extrusions with aluminium foam filler

SummaryAn experimental programme consisting of 24 tests was carried out to study the three-point-bending behavior of square AA6060 aluminium extrusions filled with aluminium foam under quasi-static loading conditions. The outer cross section width and span of the beams were kept constant at 80 mm and 800 mm, respectively. The main parameters investigated were the foam density, the extrusion wall strength and the extrusion wall thickness. The experiments showed that the foam filler significantly altered the local deformation pattern of the beams. Simple design formulae were developed in order to predict the load bearing capacity of the foam filled beams.

Joining of aluminium using self-piercing riveting: Testing, modelling and analysis

The paper presents a study on identification and modelling of self-piercing rivet connections in aluminium. Failure loads of self-piercing rivets have been investigated under combined opening and shear static loading conditions using a new test set-up and simple specimen geometry with only a single rivet. These results were used to identify rivet model parameters in the code LS-DYNA using inverse modelling. Static and dynamic tests were conducted on double-hat sections made of aluminium sheets jointed with self-piercing rivets at the flanges to validate the chosen rivet model. The numerical analyses of these components provided a direct check of the accuracy and robustness of the numerical model.

Design of aluminium foam-filled crash boxes of square and circular cross-sections

Abstract The transportation industry currently considers aluminium foam with interest for use in passive safety components. For low speed crashes, the crash box concept is widely used in bumper systems as a constituent for localisation of plastic energy absorption. The current paper summarises the experiences gained at the Structural Impact Laboratory related to generic, composite crash boxes made from aluminium extrusions with aluminium-foam filler. The experience is concentrated in a simple framework of design formulas that can be applied for preliminary design of such components.

Crash behavior of foam-based components: Validation of numerical simulations

An extensive experimental database has been established for the structural behaviour of aluminium foam and aluminium foam-based components (foam-filled extrusions). The database is divided into three levels: 1) foam material calibration tests, 2) foam material validation tests and finally 3) structural interaction tests where the foam interacts with aluminium extrusions. This division makes it possible to validate constitutive models applicable to aluminium foam for a wide spectrum of loading configurations. To illustrate the use of the database, four existing material models for foams in the explicit, non-linear finite element code LS-DYNA have been calibrated and evaluated against configurations in the database.