New Planar and Volume Versions of a Metamaterial

Some characteristics of materials with negative permittivity and permeability, i.e., with a negative refrative index, known as metamaterials, are presented in this paper. Dispersion characteristics of left-handed parallel strips calculated by different methods are compared with each other. The calculated and measured dispersion and transmission characteristics of a newly proposed left-handed coplanar waveguide and of a novel volume metmaterial are shown. Simple equivalent circuits of both structures are presented together with elements values. The structures exhibit a negative refractive index in a wide frequency band

Behaviour of eggshell membranes at tensile loading

The aim of this paper was to study the mechanical behaviour of the eggshell membrane using tensile tests at different loading rates. The eggshell membrane was obtained from commercial breeding lines of Japanese quails (Coturnix japonica). Samples were cut out of the membrane in latitudinal direction. TIRAtest 27025 tensile testing machine equipped with a 200 N load-cell was used. Tensile deformation exhibits both non-linear as well as linear region. The dependence of the stress on the strain in non-linear region can be described using of the Mooney-Rivlin equation. Linear region corresponds to the elastic strain. Parameters of the used equation are dependent on the strain rate. Generally, the strength of the eggshell membrane increases with the strain rate

Identification of complex modulus using of the Hopkinson Split Pressure Bar.

A split Hopkinson pressure bar procedure was used for non-parametric identificon of complex\nmodulus under conditions of non-equilibrium and axially non-uniform stress Tests were carried out with\naluminium bars and with specimens of composite materials (Low viscosity epoxy resin and Baytube multiwalled\ncarbon nanotubes) and having diameter 15 mm and length 7 mm. The influence of the nanotubes\nconcentration on the dynamic response of given composites was evaluated

Studium rázově zatěžovaného slepičího vejce experimentálně i numericky

Eggs were excited by the ball impact on the blunt side or the hipe side or the equator,and the response signals were detected by the laser-vibrometers.Relationship between the dominant frequency and the egg properties has been established.The numerical analysis of the egg impact has been performed using LS DYNA 3D finite element code

A Split Hopkinson Bar Method for Testing Materials with Low Characteristic Impedance

A split Hopkinson pressure bar (SHPB) technique has been developed to study dynamic behaviour of materials having low characteristic impedance. To enable better matching of characteristic impedance with a specimen, polymethyl methacrylate (PMMA) bar is used as the output bar. The viscoelastic properties of PMMA are determined in advance through preliminary experiments. In the present SHPB method, the wave analysis of the stress pulses is executed in the frequency domain. Transmitted pulses on the PMMA output bar resulting from a SHPB test are resolved into frequency components by the Fourier transform, and are corrected to be the waveforms at the specimen-bar interfaces. The corrected waveforms have been used for the evaluation of experimental results on the stress pulse transmission and reflection at the interface between elastic (Aluminium) and viscoelastic bars

Chování vaječné skořápky nedestruktivně rázově zatěžovaných slepičích vajec

In the given paper the main attention is focused on the vibration behaviour of the egg after impact excitation by a steel ball.A dynamic stiffness parameter,kdyn,is introduced wchis is based on a mathematical mass-spring model of the dynamic behaviour of the egg.A finite element model of the static and dynamic eggshell behaviour has been developed in order to understand better the relationships between the two parameters

Evaluation of Plate Structure Response to Buried Explosive Charges

An interactiom of the blast pressure wave after detonation of a burried mine under the multilayer mine protection mounted to the bottom of a vehicle is described in this paper.The main focus was applied to absorbing capability of the multilayer sandwich. Results from numerical simulations were compared with experimental tests. The test procedure is provided according to STANAG 4569/AEP-55 standard with threat level 3B

Spall behaviour of the low alloyed high strength steel

Des theories basées sur l'energie de rupture d' ecaillage sont examinées. L'influence de la structure est etudiée. La transition fracture est examinée.The spall behaviour of low alloyed high strength steel was studied. Nine different microstructures of this steel were prepared. The experimentally found dependence of spall strength, σc, on the strain rate, ε., exhibited features suggesting a transition in the spall fracture mode. The results were interpreted in terms of an energy-based theory of spall