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1

Controlled Synthesis and Application of Nano-energetic Materials Based on the Copper Oxide/Al System

He S., Chen J., Yang G., Qiao Z., Li J.

Central European Journal of Energetic Materials

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2015

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Vol. 12, no. 1

129--144

EN

Nanothermite composites containing metal oxide and metal fuel are attracting attention due to their outstanding combustion characteristics. The morphology of metal oxide is important for the performance of nanothermite composites. In this paper, branch-, plate-, sphere-, and hollow sphere-like CuO nano/microstructures were synthesized via a facile hydrothermal process. The CuO/Al based nanothermites were prepared via ultrasonic mixing of the asobtained CuO products and nano-Al. The combustion behaviour of CuO/Al based nanothermites was analyzed by DSC and laser ignition. This study shows that this nanoscale mixing resulted in a large interfacial contact area and low diffusional resistance between the fuel and the oxidizer, and the reaction reflects large energy and laser ignition sensitivity.

2

Steady symmetrical temperature field in a hollow spherical particle with temperature-dependent thermal conductivity

Moosaie A.

Archives of Mechanics

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2012

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Vol. 64, nr 4

405-422

EN

In this work, an exact analytical solution to the axisymmetric heat conduction equation for hollow spherical objects with temperature-dependent thermal conductivity is presented. The nonlinear differential equation is first transformed into a linear one by means of an integral transform method. Then, the separation of variables method is employed to solve the transformed linear equation. Ultimately, we use the inverse transform to obtain the physical temperature field. Furthermore, two examples are worked out, i.e., the one-dimensional heat conduction in the radial direction and the two-dimensional case with axial symmetry. The solution is presented as an infinite series in terms of Legendre functions. The problem with spherical symmetry is also solved by using perturbation methods up to the third-order approximation, and the results are compared with the exact solution.

3

Elastic, perfectly plastic hollow sphere problem: a finite strain solution and energetic analysis

Zambelli S., Hild F., Trumel H., Roy G., Pellegrini Y. -P.

Foundations of Civil and Environmental Engineering

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2010

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No. 13

117--127

EN

The growth of a void in a sphere of an elastic perfectly plastic material subjected to an external hydrostatic loading is modeled in the framework of irrotational finite strains. It is shown that, for small initial void volume fractions, the infinitesimal plastic strain hypothesis leads to a gross overestimation of the void growth kinetics. This assumption is relaxed in the present work, and the analytical results compare exactly with numerical simulations carried out with the commercial finite element code ABAQUS. A thermodynamic analysis is then performed, and will be considered as a basis for investigating thermal softening and micro-inertia effects on the damage process.

4

An investigation on thermoelastic behaviour of functionally graded thick spherical vessels under combined thermal and mechanical loads

Alavi F., Karimi D., Bagri A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 2

422-428

EN

Purpose: The subject of this paper is to study the thermoelastic behavior of thick functionally graded hollow sphere under thermal and mechanical loads. The mechanical and thermal properties of FG sphere are assumed to be functions of radial position. Design/methodology/approach: In present study, two methods are used to estimate the effective mechanical properties of FG sphere. One of the simplest methods in estimation of the effective mechanical and thermal properties of a mixture of two constituent materials is the Rule of Mixture (R-M) scheme. Another scheme for estimating the mechanical properties is due to the work of Mori-Tanaka. When the mechanical properties of FG sphere are estimated by using the Mori-Tanaka scheme, thermal material properties of FG body may be determined utilizing the R-M or the other methods which will be discussed as follows. Findings: Results for the temperature, radial displacement, radial stress and hoop stress fields through the geometry of the sphere are give. The figures reveal that some minor difference may be obtained for two schemes and the difference between the results for displacement distribution is larger than difference of temperature and stress distributions. Practical implications: The thermal material properties are obtained utilizing the Hatta-Taya and Rosen- Hashin relations. Also, the mechanical properties are estimated using the Mori-Tanaka scheme. In addition to the methods of approximation of material properties cited above, the rule of mixture scheme for determination of thermal and mechanical properties is also considered and results of these two schemes are compared for two cases of material composition through the geometry of FG sphere. The FG sphere is assumed to be symmetrically loaded and one-dimensional steady-state analysis of isotropic linear thermoelastic FG sphere under combined thermal and mechanical loads is investigated. Solution of the heat conduction equation and the Navier equation are obtained by using the Galerkin finite element method and by generating 100 elements along the radial direction of FG sphere. Originality/value: This paper presents the FEM analysis of a functionally graded thick hollow sphere which its thermal and mechanical material properties only depend on the radial position.

5

Dynamic fragmentation of melted metals upon intense shock wave loading. Some modelling issues applied to a tin target

Signor L., Dragon A., Roy G., Resseguier T. de, Llorca F.

Archives of Mechanics

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2008

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Vol. 60, nr 4

323-343

EN

We are interested in the dynamic fragmentation event produced in shock-melted metals called micro-spalling. Global energetic approach is briefly reviewed. It provides a general modelling framework that leads to realistic fragment-size predictions. But the actual physical mechanisms involved remain poorly understood. We attempt to explore the conditions under which cavitation, i.e. nucleation and growth of microvoids, may be responsible for fragmentation. This cavitation process is described by means of a hollow sphere model whose matrix is made of liquid tin.