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

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

Dynamic fracture of ceramics

The aim of the paper consists in the comparison of two experimental methods which are used for the study of the ceramics fracture under dynamic loading. The experimental study has been performed for the specimen of the Al$_{2}$O$_{3}$. The loading has been performed using of the Taylor test. The impact velocity when the fracture of the specimen starts has been determined. Using of the numerical simulation of the given test, the dynamic strength of the given material has been evaluated. In the next step, the dynamic Brazilian tests has been performed with a Hopkinson bar, at strain rates 76 s$^{-1}$. The numeric simulation showed the agreement between results of both methods

EFFECT OF NEUTRON IRRADIATION ON VISCOPLASTIC BEHAVIOUR OF REACTOR PRESSURE VESSEL STEEL

Ce papier décrit les résultats d'une étude de l'influence d'une irradiation aux neutrons sur les propriétés mécaniques d'un acier de cuve de réacteur pressurisé dans une gamme de vitesse de déformation allant de 10-3 à 104s-1 pour des températures comprises entre -196°C et 500° C. Les résultats, exprimés en terme de variation de la contrainte d'écoulement σf à 1% de déformation, sont analysés à l'aide de la théorie de la viscoplasticité. Les valeurs de certains paramètres de cette théorie sont calculées.This paper describes the results of an investigation of the influence of neutron irradiation on mechanical properties of a reactor pressure vessel steel at strain rates from 10-3 to 104s-1 and temperatures from -196°C to 500°C. The results, expressed in terms of the variation of the flow stress σf at 1% strain, are analysed in terms of the theory of viscoplasticity. The values of certain parameters of this theory are calculated