Search

The Hopkinson split pressure bar (HSPB) was used for the testing of three polymers at strain rates between 10^2 to 10^3 1/s. Higher strain rates were achieved using the direct Hopkinson test. Experimental data were evaluated in time as well as in the frequency domain. A more detailed analysis in the frequency domain showed that the description of tested polymers can be described in the framework of the linear viscoelasticity. The use of the direct Hopkinson test showed the occurrence of a permanent strain.

An experimental system was set up to generate the impact force, measure the response wave signal and analyze the frequency spectrum for detection of the behavior of grape berries at different harvest days. Seven varieties of grape berries harvested for six consecutive weeks have been tested. The response of grape berries to a nondestructive impact is studied both in time and in frequency domains. The digitalized time history of the force was analyzed to extract some mechanical characteristics (peak force, impact duration, impulse). The evaluation of the modulus of elasticity of berries using frequency response characteristics was carried out. This modulus decreases with the total sugar content. This dependence can be used for the estimation of the maturity of grape berries. Practical Applications This paper describes the use of a technique of the nondestructive impact for monitoring grape texture, particularly during ripening. It was found that the response of the grape berries to this impact measured as the time history of the surface displacement provided reliable tool to monitor the progress of grape maturity. The described method could also be used to highlight important information on grape evolution during ripening including their composition (total sugar content) and help to provide better insight on the choice of the preferred/ideal harvest date. Owing to the available computer techniques, this method enables testing much more number of berries in comparison with classical methods of the evaluation of grape's mechanical properties. [ABSTRACT FROM AUTHOR]

This paper describes experimental investigation on the response of new advanced materials to low and high velocity load. The main aim of the experiments is to improve the behaviour of sandwich structures under dynamic loading, in particular explosion. Two types of porous raw particle materials based on expanded glass and ceramics in combination with polymeric binder were used to design a new type of blast wave energy absorber. The effect of binder amount and type of filler on the static and dynamic properties of designed materials was evaluated. Bulk density, compressive and flexural strength under quasi-static load were determined on prism specimens. Izod impact strength characteristics were evaluated as well. Numerical simulations were conducted to determine the dynamic response of the material in sandwich structure, using implicit/explicit solver LS-Dyna. As the last step, the developed material was used as the interlayer of blast resistant litter bin, and its functionality was verified by real field blast tests. [ABSTRACT FROM AUTHOR]