Applied Mechanics and Materials Vol. 756

Abstract: The effect of ion-assisted deposition of the Al films on their UV reflectance is investigated in this paper. The films' reflectance is measured by a spectrophotometer. The obtained films are examined by using transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and atomic force microscopy (AFM). The TEM and AFM measurements allow the determination of the size of crystallites in a film and its microstructure. The XRD analysis reveals that the films deposited with argon ion-beam assist are characterized by much higher microstress levels compared to the films deposited without ion assist. The comparison of the Al films’ reflectance measurements indicate that the films with a higher microstress level (hence, higher defect concentration) are characterized by the enhanced reflectance in the UV region. The conducted investigation shows that the defects of the Al films’ crystalline structure affect its optical properties.

Abstract: The removal and recuperation of copper from the residual liquors of galvanic industry by ion exchange have been studied using the natural clinoptilolite and mordenite zeolites from different deposits of Russia and Georgia.

Abstract: This paper presents the analysis of rubberlike hyperbranched polyethylene (PE) deposits in separators and high-pressure (HP) recycle system with use of NMR spectroscopy ¹³С, X-ray phase analysis and differential scanning calorimetry; polymer extraction separation with boiling o-xylene and comparison of fraction characteristics have been carried out. With literature data and process conditions taken into account the potential reason of such structure polymer synthesis is being under discussion.

Abstract: This study presents the results of polymeric deposit analysis from propylene washing column of «Spheripol» process polymerization unit using such methods as gel-permation chromatography, differential scanning calorimetry (DSC), X-ray phase analysis, IR and NMR¹³C-spectroscopy and analytical process control methods. For comparison the relative data for larger volume polypropylene grades have been presented as well. Based on the findings and available similar practice in a slurry process an assumed formation mechanism was proposed for the discussion.

Abstract: Deformation and damage occurring at the meso-scale level in structured representative volumes (RVE) of modern nanocomposites in wide loading conditions were simulated. The computational models of a structured RVE of ceramic nanocomposites were developed using the data of structure researches on meso-, micro -, and nanoscale levels. The critical fracture stress on meso-scale level depends not only on relative volumes of voids and inclusions, but also on the parameters of inclusion clusters. The critical fracture stress at the meso-scale level depends not only on relative volumes of voids and strengthened phases, but also on sizes of corresponding structure elements. In the studied ceramic composites the critical failure stress is changed non-monotonically with growth of the volume concentration of strengthening phase particles. At identical porosity, concentration of nanovoids in the vicinity of grain boundaries causes the decrease in the shear strength of nanostructured and ultrafine-grained ceramics. It is revealed that the occurrence of bimodal distributions of the local particle velocity at the meso-scale level precedes the nucleation of microcracks. At mesoscale level of ceramic nanocomposites the pressure and particle velocity distribution don’t display a resonance behavior under submicrosecond single shock pulse loading or repeated pulse loadings.

Abstract: Multiscale computer simulation approach has been applied to research mechanisms of failure in ceramic nanostructured ceramics under dynamic loading. The obtained experimental and theoretical data indicate quasi-brittle fracture of nanostructured ZrB₂ ceramics under dynamic compression and tension. Damage nucleation and accumulation in quasi brittle nanostructured ceramics were simulated under impact loadings. Fracture of nanostructured ultra-high temperature ceramics under pulse and shock-wave loadings is provided by fast processes of intercrystalline brittle fracture and relatively slow processes of quasi-brittle failure via growth and coalescence of opened microcracks. For nanostructures ZrB₂ ceramics with porosity of 7 %, the compressive strength at strain rate of 1800 s^-1 is equal to 2440±50 MPa, the tensile strength at strain rate of 300 s^-1 is equal to 155±20 MPa.

Abstract: Deformation and damage at the meso-scale level in representative volumes (RVE) of light ultrafine grained (UFG) alloys with distribution of grain size were simulated in wide loading conditions. The computational models of RVE were developed using the data of structure researches aluminum and magnesium UFG alloys on meso-, micro -, and nanoscale levels. The critical fracture stress on meso-scale level depends not only probabilistic of grain size distribution in RVE but relative volumes of coarse grains. Microcracks nucleation is associated with strain localization in UFG partial volumes in alloys with bimodal grain size distribution. Microcracks branch in the vicinity of coarse and ultrafine grains boundaries. It is revealed that the occurrence of bimodal grain size distributions causes the increasing of UFG alloys ductility, but decreasing of the tensile strength. The distribution the shear stress and the local particle velocity takes place at mesoscale level under dynamic loading of UFG alloys with bimodal grain size. The increasing of fine precipitations concentration not only causes the hardening but increasing of ductility of UFG alloys with bimodal grain size distribution.

Abstract: Quality improvement problem has been considered for a laser sintered surface layer. Purposely built experimental setup was described together with a four-factor experiment design on laser sintering PMS-1 copper powder. A mathematical model describing the effect of laser sintering process parameters on the surface roughness has been proposed. Practical recommendation for improving the quality of the surface layer is given.

Abstract: At present the development of methods of layer-by-layer and line-by-line synthesis of finished prototypes and functional products made of powder materials furthers introduction of these technologies into different areas of human activities from light to heavy industry and medicine. The research has been carried out to describe how gamma radiation of the Co⁶⁰ radioactive isotope and the mechanical activation makes an impact on the copper powder, as well as the nature of sintering by the layer-by-layer laser synthesis. The changes of the structure and properties of the powder, which generally affects the layer-by-layer laser process of products sintering, have been detected.

Abstract: The results of investigation of physical and mechanical properties of ceramic materials manufactured by compaction of alumina, zirconia, and aluminum oxynitride powders using spark plasma sintering (SPS) are presented. It is found out that the ceramics thus produced exhibit improved density and microhardness compared to the materials sintered at high temperature in a resistance furnace.