Impact response of curved sandwich panels under cylindrical foam projectiles impact

Abstract not available

Dynamic indentation and penetration properties of aluminium foams

Failure of aluminium foams due to dynamic indentation and penetration is very common in their application such as light-weight structural sandwich panels, packing materials and energy absorbing devices. This requires a sound understanding of deformation and energy absorption mechanisms of the aluminium foams as well as the effect of impact velocity. In this study, a finite element analysis using ABAQUS is conducted for the dynamic indentation/penetration process of aluminium foams under a rigid flat-headed indenter. The indenter is pushed into the foam either at a constant velocity or with an initial velocity. Two mechanisms exist: compression of the foam ahead of the indenter and fracture along the indenter edge. Effect of impact velocity is noted on the size of a localized deformation and the total energy absorbed

PARAMETRIC LEVEL SET METHOD-BASED TOPOLOGY OPTIMIZATION OF HEAT CONDUCTION STRUCTURES

With the problems of complicated calculation process and lower computational efficiency in topology optimization using the traditional level set method（LSM） of heat conduction structures,parametric level set method（PLSM） is introduced into topology optimization for heat conduction structures.The compactly supported radial basis functions（CS-RBFs） are used to interpolate the initial level set function.The interpolation coefficients of CS-RBFs are proposed as the design variables,dissipation of heat transport potential capacity is adopted as the objective function,and the volume of material is used as the constraint.The topology optimization model for heat conduction structures is thus built.Because the method of moving asymptotes（MMA） is used to update the interpolation coefficients of CS-RBFs,the process of topology optimization for structures is transformed into that of updating interpolation coefficients and the optimal topology is finally obtained.Numerical examples show that the optimal results using PLSM are essentially in agreement with those of LSM optimal results,which illustrates the feasibility and validity of the proposed method

TOPOLOGY OPTIMIZATION OF STRUCTURES USING HYBRID CELLULAR AUTOMATION METHOD BASED ON RELIABILITY

In order to suppress gray-scale elements in Hybrid Cellular Automation method, distance factor and a new updating technique for state variables are proposed, combining the uncertainty of engineering structure, the optimization model of structural topology is established based on reliability. First, the modified random variables could be obtained through the reliability analysis, the reliability constraints are translated into deterministic constraints, and then the modified random variables are used for deterministic structural topology optimization. The optimization results under different updating techniques are contrasted. Results show that the proposed updating technique for state variables can effectively reduce the amount of gray-scale elements and reduce the strain energy of the structure

Ideal Oscillation of a Hydrogenated Deformable Rotor in a Gigahertz Rotation–Translation Nanoconverter at Low Temperatures

It was discovered that large-amplitude axial oscillation can occur on a rotor with an internally hydrogenated deformable part (HDP) in a rotation–translation nanoconverter. The dynamic outputs of the system were investigated using molecular dynamics simulations. When an input rotational frequency (100 GHz > ω > 20 GHz) was applied at one end of the rotor, the HDP deformed under the centrifugal and van der Waals forces, which simultaneously led to the axial translation of the other end of the rotor. Except at too high an input rotational frequency (e.g., >100 GHz), which led to eccentric rotation and even collapse of the system, the present system could generate a periodic axial oscillation with an amplitude above 0.5 nm at a temperature below 50 K. In other ranges of temperature and amplitude, the oscillation dampened quickly due to the drastic thermal vibrations of the atoms. Furthermore, the effects of the hydrogenation scheme and the length of HDP on the equilibrium position, amplitude, and frequency of oscillation were investigated. The conclusions can be applied to the design of an ideal nano-oscillator based on the present rotation–translation converter model

Experiments on curved sandwich panels under blast loading

In this paper curved sandwich panels with two aluminium face sheets and an aluminium foam core under air blast loadings were investigated experimentally. Specimens with two values of radius of curvature and different core/face sheet configurations were tested for three blast intensities. All the four edges of the panels were fully clamped. The experiments were carried out by a four-cable ballistic pendulum with corresponding sensors. Impulse acting on the front face of the assembly, deflection history at the centre of back face sheet, and strain history at some characteristic points on the back face were obtained. Then the deformation/failure modes of specimens were classified and analysed systematically. The experimental data show that the initial curvature of a curved sandwich panel may change the deformation/collapse mode with an extended range for bending dominated deformation, which suggests that the performance of the sandwich shell structures may exceed that of both their equivalent solid counterpart and a flat sandwich plate

Short sandwich tubes subjected to internal explosive loading

The response of sandwich tubes under internal explosive loading was investigated experimentally, numerically and analytically in this paper. Experiments were conducted first to capture the fundamental deformation and failure patterns and they served as a basis of validation for both the FE and analytical models. Further detailed deformation and blast loading history were revealed by the FE model. An explicit analytical solution for the deformation of sandwich tubes under blast loading has been worked out and used to obtain the optimum sandwich configurations, which would outperform their corresponding monolithic tubes

Energy absorption of sandwich tubes under lateral loading

The energy absorption of sandwich tubes impacted between two rigid plates was investigated experimentally and numerically in the paper. Based on the collapse patterns observed in quasi-static experiment, several typical sandwich specimens were made and tested. The specimens were placed on the bottom platen of an Instron machine and gained a constant upwards velocity, followed by the impact with the top rigid platen. Their deformation history and load-compression curves were recorded. The energy absorption of sandwich tubes were then calculated and analyzed. Three different crushing patterns have been identified from previous experiments. The dynamic enhancement of energy absorption of the sandwich tubes were only observed in collapse pattern III under the tested velocity up to 10 m/s. Finite element (FE) models using ABAQUS were developed and validated against experimental results and the strain rate effect of metallic foam was considered. They were used to explore the detailed energy-absorption characteristics beyond the experimental range for impact velocities up to 100 m/s. The dynamic enhancement occurred for each configuration of sandwich tubes when the impact velocities were greater than 20 m/s. It was found that increasing the compression velocity leads to an increase in total plastic energy dissipation. Sandwich tubes with a thicker foam core are proved to be the optimum design