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[en] Highlights: • High velocity crushing of continuous graded foam is theoretically examined. • Study suggests that the graded foam outperforms its homogeneous counterpart. • The denser part should be placed at the loading end. - Abstract: Energy absorption of graded foam subjected to blast is investigated, in which the high velocity crushing of foam is modeled with shock theory and rigid-perfectly-plastic-locking idealization. The characteristics of a typical blast are taken into account when determining the foam density profile. Different from the homogeneous foam, the graded foam density variation is designed largest at the loading end and smallest at the supporting end, with an exponential decay in between. It is found that, subjected to the same blast load, the total input energy, in fact the energy to be dissipated by the cladding, decreases with increasing density gradient. The final foam deformation with larger density gradient is smaller.
[en] In this document we provide responses to the various issues raised in the report of the Preliminary Safety Review Panel (see http://mice.iit.edu/mnp/MICE0069.pdf). In some cases we have made design changes in response to the Panels suggestions. In other cases, we have chosen not to do so. In a few cases, we indicate our plans, although the tasks have not yet been completed. For simplicity, the responses are organized along the same lines as those of the Panel Report
[en] In order to design a wave energy generating system of a floater type, a 6 DOF motion technique was applied to the three Dimensional CFD analysis on a floating body and the behavior was interpreted according to the nature of the incoming waves. Waves in a tank model were generated using a single floater comparing with that of a Pelamis wave energy converter. In this paper, we focus on four variables, namely the wave height, angular velocity, diameter and length of the floater. The process was carried out in three stages and it was found that there are energy absorption differences in different parameters of wave height, length and the diameter of a floater during simulation, thus leading for the necessity of an optimal design for wave energy generation
[en] Highlights: • Novel lightweight sandwich structures with the bio-inspired double-sine corrugated cores are proposed. • The new constructions are capable of reducing the initial peak force dramatically. • The double-sine corrugated core enhances the energy absorption capacity of the sandwich structures. • Specific energy absorption is highly dependent on the wave number and wave amplitude of the double-sine corrugated core. The concept of mimicking natural materials to design novel lightweight structures with high capacity of energy absorption is of great interest at present. Enormous natural structures exhibit fascinating mechanical performance after hundreds of millions of years of convergent evolution. Odontodactylus scyllarus, known as the peacock mantis shrimp, whose dactyl strike is recognized as one of the rapidest and powerful creatures found in nature, has an enormous potential to act as excellent biomimetic protective system. In this paper, a novel lightweight bio-inspired double-sine corrugated (DSC) sandwich structure has been proposed to enhance the impact resistance. The out-of-plane uniform compression of the bio-inspired bi-directionally sinusoidal corrugated core sandwich panel has been conducted under the quasi-static crushing load. Compared with the regular triangular and sinusoidal corrugated core sandwich panels, the bio-inspired DSC core sandwich panels significantly improve the structural crashworthiness as well as reducing the initial peak force greatly. Finally, the influences of the wave amplitude, wave number and corrugated core layer thickness on the mechanical performance of the bio-inspired DSC core sandwich panel are investigated to seek for the appropriate structural parameters to optimize the energy absorption behavior.
[en] The purpose of this work was to investigate the dependence of whole-body averaged specific energy absorption rate (SAR), calculated using the finite-difference time-domain (FDTD) method, on the width of the free space region between a numerical phantom and the perfectly matched layer (pml) absorbing boundary. Results show that an increase in this width from 2 cells to 70 cells caused variations in the calculated whole-body averaged SAR of less than 2% for the FDTD code employing split-field pmls. Similarly, an increase in the width of the pml layer had little effect on the whole-body SAR values. (note)
[en] Carbon nanotubes have high strength, light weight and excellent energy absorption capacity and therefore have great potential applications in making antiballistic materials. By examining the ballistic impact and bouncing-back processes on carbon nanotubes, this investigation shows that nanotubes with large radii withstand higher bullet speeds and the ballistic resistance is the highest when the bullet hits the centre of the CNT; the ballistic resistance of CNTs will remain the same on subsequent bullet strikes if the impact is after a small time interval
[en] Stir casting technique has been applied to synthesize ZnAl12 hybrid foam to study the effect of temperature on the deformation behavior of the composite. Cenosphere particles (CPs) were used as thickening agent to increase the viscosity of melt and also used as a space holder to create microporosity into the structure. CaH2 (0.5 wt%) was used as the foaming agent. The relative density of ZnAl12 hybrid foam was found between 0.27–0.40. The synthesized hybrid foam was put under microstructural investigation and for compressive deformation behavior at high temperature. The effect of strain rate was observed at constant temperature (100 °C) varying strain rate from 0.001/s to 1/s and the effect of temperature was studied at constant strain rate (0.01/s) varying temperature in the range of 100 °C–250 °C. It is noted that higher relative density with high strain rate has higher plateau stress and energy absorption capacity at a steady temperature. The values of plateau stress and energy absorption capacity decreases as an increase in the temperature range. Densification strain has been found less effect of strain rate and temperature but it varies according to relative density. (paper)
[en] Lightweight polymeric cellular materials are increasingly used in many industrial applications because of their height mechanical and energy absorption properties. This paper investigates the effect of foam anisotropy under quasi-static compression tests. A 35 kg/m3 closed-cell rigid Polyisocyanurate (PIR) structural foam was tested in the experimental programme with a loading speed of 10 mm/min. Experimental results show that the investigated foam presents a highlighted anisotropic behavior and the main mechanical properties such as Young’s modulus, yield stress, plateau stress and onset strain of densification varies with changing the loading direction. In addition, during compression, the energy absorption performance of PIR foam is strongly affected by the anisotropy. (paper)
[en] Highlights: • The compressive properties of a beetle elytron plate (BEP) are better than those of a honeycomb plate of the same cost. • The core structure of a BEP undergoes convex deformation with three half-waves under compression. • The strengthening mechanism of high energy absorption in BEPs is found and elucidated. • The biological and engineering implications of the high energy absorption in BEPs are revealed. For the development of lightweight biomimetic functional-structural materials, the compressive deformation mode of beetle elytron plates (BEPs) and their strengthening mechanism of high energy absorption were investigated, with the following results: compared with honeycomb plates, the compressive strength and the energy absorption properties of BEPs are significantly increased. This is because in a BEP, the hollow trabeculae with high torsional stiffness cause the deformation behavior to be dominated by compression, generating a convex curve with three half-waves, which is consistent with the deformation of the honeycomb walls. This study reveals not only the compressive deformation mode and the mechanism of high energy absorption in BEPs but also the relationship between the biological prototype of a BEP and its function. The findings show that BEPs represent a significant improvement over honeycomb plates and show potential for widespread application as novel energy-absorbing sandwich structures.
[en] We present mean energy measurements for the atom optics kicked rotor as the kicking period tends to zero. A narrow resonance is observed marked by quadratic energy growth, in parallel with a complete freezing of the energy absorption away from the resonance peak. Both phenomena are explained by classical means, taking proper account of the atoms' initial momentum distribution