http://dspace.nbuv.gov.ua:80/handle/123456789/173408 2026-04-06T15:11:45Z http://dspace.nbuv.gov.ua:80/handle/123456789/173515 Effect of Platen Restraint on Stress–Strain Behavior of Concrete under Uniaxial Compression: A Comparative Study Kumar, S.; Mukhopadhyay, T.; Waseem, S.A.; Singh, B.; Iqbala, M.A. The stress-strain model of concrete depends on the degree of frictional resistance across the loading surfaces of a test specimen depending on the antifriction medium used during testing. This article presents a comparative study of platen restraint on the behavior of concrete under uniaxial compression based on an experimental investigation. The effect of four commercially available antifriction media (neoprene, polyvinyl chloride, teflon, and grease) with different layer thicknesses on platen restraint have been studied for a normal strength concrete and a relatively high-strength concrete. Subsequently, the effect of platen restraint has been quantified using the analogy of toughness. The experimental results indicate that post-ultimate response of concrete is significantly affected by platen restraint. It is shown that the stress–strain curve obtained from a conventional uniaxial compression test not only describes specimen/material behavior but also represents interaction between specimen and loading platen. Among the four antifriction media used in this investigation, grease is the most effective in reducing frictional resistance. Failure patterns of the concrete specimens for different antifriction media are also subsequently analyzed. 2016-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/173514 Numerical Simulation of Rotary Compression Process of Hollow Balls Skrochocki, D.; Tomczak, J. This paper presents results of the analysis of numerical Simulation of rotary compression process of hollow ball forging. Numerical analysis is conducted based on the finite element method using the Simufact Forming software. The methods of hollow ball forming are discussed with presentation of the geometrical model applied in calculations and the obtained rotary compression process description. The simulation is conducted under three-dimensional strain conditions. Strain, stress and temperature distributions are determined. The diagrams of forces and rotary moments of the hollow forging compression process are given. The described results of the numerical analysis confirm the possibility of producing the hollow balls by means of rotary compression with the use of billet in the form of a pipe part. 2016-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/173513 Application of the Micropolar Theory to the Strength Analysis of Bioceramic Materials for Bone Reconstruction Eremeyev, V.A.; Skrzat, A.; Vinakurava, A. The application of the linear micropolar theory to the strength analysis of bioceramic materials for bone reconstruction is described. Micropolar elasticity allows better results to be obtained for microstructural and singular domains as compared to the classical theory of elasticity. The fundamental equations of the Cosserat continuum are cited. The description of FEM implementation of micropolar elasticity is given. The results of solving selected 3D test problems are presented. Comparison of classical and micropolar solutions is discussed.; The research received funding from the People Program (Marie Curie ITN transfer) of the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement No. PITN-GA-2013- 606878. 2016-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/173512 Effect of Grinding Parameters on the Surface Quality of Cutting Tools Made of High-Speed Low-Alloy Steels Jaworski, J.; Trzepiecinski, T.; Stachowicz, F. The occurrence of defects caused by sharpening leads to the considerable variation of lifetime of cutting tools under identical process conditions. The loss of cutting ability of cutting tools or the change of the blade original geometry influences the quality of the surface finish as well as both dimensional and shape accuracy of workpieces. The effect of the grinding parameters on the surface finish of selected high-speed steels has been investigated. The influence of the grinding parameters has been defined especially for surface roughness, grinding forces and grinding ratio with a wide range of grinding parameters. It is found that the value of average roughness (Ra ) parameter decreases together with an increase in the grinding depth and the feed length. Furthermore, the value of Ra increases proportionally to the grinding depth. To increase the efficiency of sharpening, it is required to increase the feed length other than the grinding depth. 2016-01-01T00:00:00Z