Papers by Author: Robert Panowicz

Abstract: The aim of this article is to present the results of experimental studies on protection systems of military vehicles against RPG type missiles. The paper presents the research methodology of rod armours and active protection system. On the basis of the presented methodology, both a rod armour and an active protection system were investigated. The effectiveness of these solutions reaches 70% in the rod armour and about 80% in the case of the active protection system.

Abstract: The paper deals with the numerical and experimental analyses of functionally graded material structures which are represented by a surface layer of the steel sample hardened during the laser treatment process. A functionally graded parameter of the researched structure was assumed as the hardness value experimentally measured with the use of a Vickers hardness test method. The microstructure of the tested layer was also analyzed for the Vickers test verification. Two homogenization methods were used for the purpose of layer substitute properties for numerical calculations. The first one was to divide the FGM domain into a number of layers in the direction of material gradation and then apply a numerical homogenization method within each layer. The resulting material model describes the FGM as a composite of homogeneous layers. The second method was based on the Mori-Tanaka homogenization theory and was carried out with the use of Digimat software, which is the nonlinear multi-scale materials and structures modelling platform. Both methods were compared and showed good correspondence.

Abstract: In the present work, the description of a numerical model for predicting the electromagnetic composite ring expansion process and validation of a developed numerical code is presented. The strength response of rings materials under high strain rate deformation was described by using the well-known JohnsonCook constitutive relationship. Numerical considerations and experimental validation were performed for a composite ring consisted of a copper drive ring and X37CrMoV51 steel ring specimen. The analyses of the obtained results allow to find out that good convergence of theoretical and experimental data was achieved.

Abstract: The paper presents experimental and numerical results of the investigation of fragmentation process of copper rings expanded with maximum radial velocity close to 170 m/s. The experiments were performed on Cu-ETP rings of average diameter of 32 mm and cross-section of 1 x 1 mm. The authors particularly focus on the statistical concept of the ring fragmentation process. In connection with the above, the number of fragments, their size and distribution were determined on the basis of multiple experimental ring tests. It was established that for selected loading condition, the copper ring fracture appeared when the strain reached the average values of 0.35 and the average number and length of fragments were about 11 and 13 mm, respectively. Moreover, the numerical prediction of the fragment size distribution was carried out using the Mott fragmentation model.

Abstract: Selection of a constitutive model from commonly used ones, which in the best way describes dynamic behaviour of material during electromagnetic expanding ring test, is our primary goal in this work. Five more popular constitutive models are examined, i.e., Johnson-Cook, Steinberg-Guinan, Zerilli-Armstrong, MTS, and Preston-Tonks-Wallace model. As a criterion of the selection, qualitative/quantitative agreement of the numerical results with analogous data obtained from experiment presented in the work was taken [1]. It was found that the numerical results obtained by using Steinberg-Guinan or Preston-Tonks-Wallace model gave the best agreement with experimental data.