Applied Mechanics and Materials Vol. 621

Abstract: In this paper, the acoustic radiation mode’s amplitudes of laminated composite plates are studied. The layer wise finite element model is imposed to determine velocity distributions of laminated composite plates. Based on the acoustic radiation mode, the effects of the panel orientation angle on the first three orders acoustic radiation mode’s amplitude of the laminated composite plates are then discussed. A twelve-layer laminated plate was used as an example, and the numerical simulations results show that the effects of the panel orientation angle on the acoustic radiation amplitude of the laminated composite plates are significant.

Abstract: The results of experimental studies on the formation of the surface layers of a material with shape memory effect (SME) based on TiNi deposition of Pb-Bi melt at a temperature gradient of 600-1100 °C in an argon atmosphere. It is shown that this method allows to obtain uniform surface layers in nanostructured state and almost any thickness can be used for the formation of coatings on the interior surfaces of products of any shape with the stress concentrators. Structure, chemical and phase composition of the surface layers provide a manifestation of TiNi shape memory. The average grain size of TiNi coatings ranges between 60 ÷ 160 nm.

Abstract: The removal of COD_Mn, UV₂₅₄, nitrate nitrogen and turbidity have been investigated in this paper by a biological activated charcoal (BAC) reactor in different height of the filter and the in different temperature of 4-18°C and 19 to 26°C. The results show that the highest concentration of microorganism occurs in the top of the BAC. The microorganism concentration decreases from top to bottom. The backwash period at low temperature is 4-5 days by measuring permanganate index of the different packing height, which can be extended to 6-7 days at normal temperature. COD_Mn was not removed effectively by BAC with the average value of about 4.51mg/L. The removal rates COD_Mn at normal temperature and low temperature are 15.90% and 4.38% respectively. The removal of nitrate nitrogen is also influenced by temperature. Removal of turbidity and UV₂₅₄ under different stages do not show significant changes, but UV removal shows no obvious changes at the temperature of 5-26°C.

Abstract: Several lime-based plasters with fine ground brick content are studied in this article. In the first plaster the ceramics was used as lime substitute while in the second one it was dosed as replacement of the silica sand, the substitution levels being 20% and 50%. Pure lime plaster was use as a reference. Experimental methods and results of measuring basic physical properties, pore characterization, mechanical properties and liquid water transport are described. The plasters with fine ground brick were characterized by improved material’s properties in a comparison with pure lime plaster.

Abstract: Hygric transport properties belong to a group of important characteristics from a construction design point of view. Since a content of water (at whatever state) could lead to degradation processes of materials whether by phase changes or by chemical reaction (with any component of water contained), it is important to know an amount of water which can get into the pore structure of a material. Studied materials in this workwere sandstones. Several types of these clastic sedimentary rocks were chosen and experimental determinations of basic physical properties as well as hygric transport parameters were performed. From the achieved results,it is obvious that the main influence on hygric transport characteristics has the open porosity, in particular the pore structure.The higher porosity is the higher amount of water can be transported through the sandstones.

Abstract: Natural zeolite rocks are known to be able to act as Supplementary Cementitious Materials (SCM) in Portland cement based concrete. Generally SCMs are reacting with portlandite and providing binding hydration products just as Portland cement does. In this way an SCM can substitute certain amount of Portland cement in concrete and thus reduce the related energy consumption and CO₂ generation. Due to a large variability of SCMs composition and properties there is not any general rule for an optimum Portland cement substitution level. In this paper, the influence of natural zeolite rock on selected mechanical, hygric and thermal properties of concrete is studied. Experimental results show that the analyzed zeolite is acting as a pozzolan but for higher amounts its application leads to an increase in concrete porosity which affects its properties in a significant way.

Abstract: This paper studies the effect of sodium chloride as the additive component in cement paste. Sodium chloride was included at 0.5%, 1%, 1.5%, and 2% by weight of cement content. Analysis on the performance of this reagent was conducted via setting time, compressive strength, and porosity test. Based on the setting time analysis, the inclusion of sodium chloride can extend the initial setting time of cement paste up to 24.91% longer than control specimen. Obstruction on the formation of calcium silicate hydrate gel by sodium and chloride ion was one of the possible causes to this phenomenon. Acceleration on the compressive strength development by sodium chloride was also detected. It appears that sodium chloride was able to de-flocculate the coagulated cement particles and reduced the viscosities of cement slurries; hence resulted in faster early hydration process.

Abstract: The influence of radiation on magnetic material has been investigated in many researches which had proved that the magnetic properties of hard magnetic were unchangeable under radiation effect ^{[1],[2],[3],[4],[5],[6]}.In this work, we performed the study of the influence of gamma radiation on Fe₃O₄, Co_0.8Ni_0.2Fe₂O₄, Co_0.8Zn_0.2Fe₂O₄. The ⁶⁰Co gamma radiation was emitted on ferrite magnetic materials with doses 1000, 1500, 2000 kGy. Analyzing magnetic properties of the materials before and after emitting by Walker Automatic Hysteresisgraphs AMH 20-50. The change of (B-H) loop is insignificant. Our work agrees well with the result of ^[1][2][3][4].

Abstract: Polycarbosilane (PCS) fibers have been made using a solvent which is a mixture of N,N-dimethylformamide (DMF) in toluene. Polycarbosilanes (PCS) obtained from NaBond with concentration 1.2 g/ml dissolved in solution toluene and N,N-dimethylformamide (DMF) was stirred gently for 24 h at ambient temperature. DMF was mixed with toluene at ratios 22%, 24%, 26%, 28% and 30%. Electrospinning apparatus (nanoE-Spinning) from NaBond was used. In a vertical electrospinning set up, the solution in a glass syringe delivered to the tip of a 6-gauge (0.5 mm inner diameter) stainless steel needle. The tip to collector distance was adjusted to 100 mm with applied high voltage at 10kV. A stainless steel plate with dimension 100 mm x 100 mm wrapped by aluminum foil was used as collector. The electrospinning non-woven fiber was cured at temperature 200°C (2°C/min), for 1h, 1.5h, and 2h, and fibers with DMF concentration 30% was also pyrolysis at 1000 °C for 3 h in inert atmosphere. The samples were tested and observed with FTIR spectroscopy, and SEM-EDS apparatus. The results showed that PCS fibers can be made from dissolving PCS with toluene with the addition of DMF to increase the polarity of the solvent and the formation of fibers is done by using electrospinning which is supported by the presence of voltage from the outside. Fiber curing is done at 200 °C to evaporate the toluene, the DMF, and resulting stronger fibers than before. The addition concentration of DMF in toluene and curing time will affect the composition of the resulting PCS fiber. Curing time on PCS fibers will affect the composition of solvents such as DMF and Si-H bond on which to assert their PCS fiber cross linking conditions. PCS fiber morphology is known of changes in fiber diameter and fiber uniformity. Smallest PCS fiber average diameter 4.81 μm resulted from 28% DMF with curing time 2 hours and the largest achieved from 22% DMF with curing time 1 hour around 14.22 μm. Composition of pyrolyzed fiber was SiO_0.587C_0.413, with average density 3.1033 g/cc and average diameter the fiber was 3.06 μm.