Papers by Keyword: Axial Crushing

Abstract: The axial crushing behavior of commercial metal honeycombs was studied with laying emphasis on the effects of strain rate and geometry on its characteristics as an energy absorber. To investigate the effect of strain rate on the energy absorption capacity, the honeycombs of some metal foil materials were numerically modeled by taking the plastic deformation and failure of adhesively-bonded joint between corrugated sheets and the initial imperfection into consideration. The relationship between the enhancement of mean buckling stress and the strain rate was discussed. Furthermore, A3003 honeycomb model was examined by changing its branch angle from 30° to 180° because the geometrical dispersion will also affect the energy absorption capacity. Typical calculated results under different strain rate and geometric conditions were compared with the corresponding experimental results. It was found that the effect of strain rate on the stress – strain relation of the honeycomb structure is greatly relaxed as compared with that of the material itself. The effects of the boundary condition on the crushing behavior of irregular honeycombs were also discussed.

Abstract: In this paper, an analytical prediction and numerical simulation of the behavior of square crash box structures having hole at corners on dynamic axial crushing are studied. The focus of the present theoretical prediction is to calculate the mean crushing force and maximum crushing force during the folding process subjected to axial impact loading. Then, the effect of hole size to the crushing response of square crash box structures was also evaluated. For validation, an explicit non-linear commercial finite element code LS-DYNA was used to predict the response of the structures subjected to axial crushing. It was found that results of numerical method and theoretical prediction were in good agreement. The results showed that, by inserting holes at corners, the folding can be controlled to be always started from the hole, and peak crush load on the first fold can be reduced significantly. Meanwhile, the decreasing of mean crushing force is insignificant compared to the one without holes. Hence, the characteristic of impact energy absorption in a progressive buckling can be improved, the damage in passenger compartment can be minimized, and the deceleration level can be kept in safe level to prevent injury of the passenger.

Abstract: Thin-walled tubes have always considered as energy absorption systems by researchers. This paper presents a new technique for energy absorption system which is simpler than other designs in production. This novel model is a thin-walled tube with perforation. During manufacturing process, equal numbers of holes are created in rows and columns in order to increase the energy absorption ability. In this article two different workpieces with the same geometry, one with holes and the other one with grooves, are compared to validate the model in accordance with other presented ones. For this purpose, specimens were modeled in finite element software ABAQUS with the same conditions and the amount of energy absorption, the initial decay, and the weight ratio of energy absorption (SEA) were evaluated. Then results which obtained from simulation are compared with experimental ones. Results confirmed that specimens with perforation have better decay symmetry rather than ones with grooves. In addition, force absorption in workpieces with hole is as twice as ones with grooves. The amounts of absorbed energy and SEA in workpieces with perforation are 56% and 46% more than workpieces with grooves, respectively.

Abstract: A thin cylindrical tube model was established. Its energy absorption property was analyzed when crushing through finite element method. Then its validity was verified through the corresponding experiment. On the basis of the above research, two different material tubes were selected which were aluminum alloy 6060 and cold-roll steel B340LA. Considering the mechanical performance of these two materials might change during dynamic crushing, so the tubes were crushed in three modes including low speed, medium speed and high speed. In order to predict the wall thickness of the two different material tubes when their energy absorption was equal, two methods were proposed which were overall energy method and the stress-strain energy method. Then get the mass ratio of the two different material tubes when they absorbed equal energy. The results showed that the mass of aluminum alloy 6060 tube was about 86%-90% to B340LA tube when they absorbed equal energy. More than 10% lightweight effect could be obtained when cold-roll steel B340LA tube was instead with aluminum alloy 6060 under the condition of their absorbing equal energy.

Abstract: Numerical and experimental study of the effects of center holes located at opposite sides on dynamic axial crushing of thin-walled square aluminum extrusions column are presented in this paper. The results showed that, by inserting the holes, the impact energy absorption characteristic in a progressive buckling can be improved as the starting location of the plastic deformation is always from holes and peak crush force can be decrease, so that the deceleration does not exceed the limit that can injure the passenger when frontal impact occurs. Here, the results of numerical simulations, conducted using an explicit finite element code, are compared with experimental results for various hole diameter. The results shows that the peak crushing force is decrease, while the mean crushing force is relatively constant.

Abstract: This paper presents the study of prismatic columns of different cross sections subjected to low velocity impact, which are commonly used as energy absorber components in vehicles. The impacts of the columns were numerically analyzed using FEM. Four cross sections were considered, i.e. square, hexagonal, octagonal and circular. For each cross section, columns with several combinations of perimeters and thicknesses were analyzed. The results showed that, for columns with equal perimeter and thickness, those with circular cross sections have the highest mean crushing force and those with square cross sections have the lowest crushing forces. Furthermore, keeping all other parameters constant, columns with thicker wall have significantly higher crushing force while columns with longer perimeter have only slightly higher crushing force. This parametric information will be very useful for modern automotive industry in designing front longitudinal members within an acceptable safety level.

Abstract: Various polygonal tubes were compressed in the axial direction under quasi-static and dynamic loading conditions. The effect of the polygonal shape and the wall thickness on the crush behavior is investigated, in which the cyclic buckling takes place. The numbers of polygonal edges were 3, 4, 5, 6 and 7 in the experiment. A circular tube was also tested for comparison. The tubes were machined from aluminum alloy A5056 bar. Crush strength is estimated as an index of the energy absorption capacity of the tube. It increases with increasing the number of polygonal edges of the tube, although it almost saturates when the number of polygonal edges is more than 6. For the wider variety of polygonal tubes than that in the experiment, numerical simulation is performed using the dynamic explicit finite element code DYNA3D. The computed crush behavior well agrees with the corresponding experimental one, however, the difference in collapse mode arises due to the slight imperfections in experiment. The deformation pattern becomes more irregular for the thinner-walled tube. Further, it is presumed that the large hardening exponent in the plastic property of the material could prevent the buckling switching from the symmetric mode to asymmetric one in the crushing of circular tube.