Sigit Santosa

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.

Crash behavior of box columns filled with aluminum honeycomb or foam

Abstract The effect of low density filler material, such as aluminum honeycomb or foam, on the axial crushing resistance of a square box column under quasi-static loading conditions is studied. Numerical simulation shows that in terms of achieving maximum energy absorption, filling the box column with aluminum honeycomb can be preferable to thickening the column wall. Superior specific energy absorption is also obtained by filling the column with moderate or high strength aluminum foam. Simple formulas for the relationship between mean crushing force and the strength of filler are developed. Moreover, the presence of adhesive increases energy absorption significantly compared to unbonded filling.

On the modeling of crush behavior of a closed-cell aluminum foam structure

Crush behavior of a closed-cell aluminum foam is studied analytically and numerically. A new model of a truncated cube, which captures the basic folding mechanism of an array of cells, is developed. The model consists of a system of collapsing cruciform and pyramidal sections. Theoretical analysis is based on energy consideration in conjunction with the minimum principle in plasticity. The assumed kinematic model for the crushing mechanism of the truncated cube cell gives a good agreement with the deformation mechanism obtained from the numerical simulation. Analytical formulation for the crushing resistance of the truncated cube cell is shown to correlate very accurately with the numerical results. Closed form solutions for crushing resistance of closed-cell aluminum foam in terms of relative density are developed. The formulas are compared with the experimental results and give an excellent agreement.

Effect of an ultralight metal filler on the bending collapse behavior of thin-walled prismatic columns

Abstract The effect of low-density metal filler, such as aluminum foam or honeycomb, is studied on the bending collapse resistance of thin–walled prismatic columns. A combination of analytical and numerical results is used to predict the initial and post collapse response of empty and filled columns. Closed-formed solutions for the bending-rotation characteristics are constructed in terms of the geometrical parameters and the filler strength. The low-density metal core retards sectional collapse of the thin-wall column, and increases bending resistance for the same rotation angle. Numerical simulations show that, in terms of achieving the highest energy absorption to weight ratio, columns with aluminum honeycomb or foam core are preferable to thickening the column wall. Moreover, the presence of adhesive improved the specific energy absorption significantly.

Experimental and numerical analyses of bending of foam-filled sections

SummaryNumerical simulations and experiments are conducted to study the bending crush behavior of thin-walled columns filled with closed-cell aluminum foam. A nonlinear dynamic finite element code was used to simulate quasi-static three point bending experiments. The aluminum foam filler provides a higher bending resistance by retarding inward fold formation at the compression flange Moreover, the presence of the foam filler changes the crushing mode from a single stationary fold to a multiple propagating fold. The progressive crush prevents the drop in load carrying capacity due to sectional collapse. Henceforth, the aluminum foam filling is very attractive to avoid global failure for a component which undergoes combined bending and axial crushing. This phenomenon is captured from both experiment and numerical simulation. It was found that partially foam-filled beams also still offer, high bending resistance, and the concept of the effective foam length is developed. Potential applications of foam-filled sections for crashworthy structures are suggested.

Bending collapse of thin-walled beams with ultralight filler: numerical simulation and weight optimization

SummaryA study on the bending collapse of thin-walled beams filled with aluminum foam or aluminum honeycomb was carried out. The strengthening effects of ultralight metal fillers were quantified numerically and experimentally. The moment-rotation characteristics of filled sections were derived, and the results were then incorporated with structural optimization technique to develop a methodology for crashworthiness optimization of filled members. The proposed methodology requires relatively simple computations and is suitable for early stage design of crash members. Finally, the optimization problem of filled sections under combined compression/bending loading was formulated and solved. The optimization results showed potentials of significant weight saving and volume reduction by utilizing ultralight metal filler.

Bending Crush Resistance of Partially Foam-Filled Sections

Potential applications of foam-filled sections are for the automotive structures. A foam-filled section can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision. In the case of biaxial loading where bending and axial compression are involved in the crushing mechanics, the foam filler will be significant in maintaining progressive crushing of the thin-walled structures so that more impact energy can be absorbed. In the case of side collision, the foam-filled section can be used to strengthen the B-pillar structure to avoid severe intrusion in the passenger compartment.

Steel Plate Behavior under Blast Loading-Numerical Approach Using LS-DYNA

Plate is one of the most common structural elements, which appears in a wide range of applications: steel bridges, blast-resistance door, and armored vehicles. In this paper, the behavior of steel plates under blast loading was studied through numerical approaches using LS DYNA and then the results were compared with the experiment results obtained from existing literatures. The study of a clamped square plate exposed to blast loading in three distinct stand-off distances. Three different methods of modeling blast loading were used, namely: empirical blast method, arbitrary Lagrangian Eulerian (ALE) method, and coupling of Lagrangian and Eulerian method. The empirical blast method was deployed by using key card *LOAD_BLAST in LS-DYNA. In ALE method, Langrangian and Eulerian solution were combined in the same model and the fluid-structure interaction (FSI) handled by coupling algorithm. In coupling method, the engineering load blast in LS-DYNA (*LOAD_BLAST_ENHANCED) was coupled with the ALE solver. In terms of central deflection and computational time, the coupling method appeared to be the best method which is very time-effective and showed a good correlation with the experiment data.

Measurement of Mechanical Properties of St 37 Material at High Strain Rates Using a Split Hopkinson Pressure Bar

The dynamic mechanical properties of a material are important keys to investigate the impact characteristic of a structure such as a crash box. For some materials, the stress-strain relationships at high strain rate loadings are different than that at the static condition. These mechanical properties depend on the strain rate of the loadings, and hence an appropriate testing technique is required to measure them. To measure the mechanical properties of a material at high strain rates, ranging from 500 s-1 to 10000 s-1, a Split Hopkinson Pressure Bar is commonly used. In the measurements, strain pulses are generated in the bars system, and pulses being reflected and transmitted by a test specimen in the bar system are measured. The stress-strain curves as the material properties of the test specimen are obtained by processing the measured reflected and transmitted pulses. This paper presents the measurements of the mechanical properties of St 37 mild steel at several strain rates using a Split Hopkinson Pressure Bar. The stress-strain curves obtained in the measurement were curve fitted using the Power Law. The results show that the strength of St 37 material increases as the strain rate increases.

Numerical simulation of SHPB to measure the mechanical properties of aluminium foam material at high strain rate by using MAT 163 modified crushable foam

Aluminium foam is a kind of metal foam material which has large energy absorption capability. The mechanical properties of aluminium foam material in high strain rates could be measured by using SHPB. Numerical simulation is used as the initial step to measure mechanical properties of this material. MAT 163 modified crushable foam used as material model in the SHPB numerical simulation of aluminium foam. Numerical simulation showed a quite close results to experimental data.