Applied Mechanics and Materials Vols. 752-753

Abstract: In this paper, yttrium aluminum garnet-magnesium aluminate spinel with good mechanical strength was fabricated by directional solidification, and its microstructure and mechanical properties were investigated. MgAl₂O₄-Y₃Al₅O₁₂ eutectic rods were grown by a float zone method. The composition of the grown ingots was determined by the X-ray diffraction technique and electron probe microanalysis. The crack growth characteristics were examined in directionally solidified YAG/spinel eutectics. The residual stresses were determined in MgAl₂O₄/Y₃Al₅O₁₂ eutectics using piezospectrosocopic probes. The crack growth behaviors show that residual stresses play a key role in the crack growth.

Abstract: Composite character of ceramics is a base for creating new generation materials. It is established that the rational choice of the basic structural elements allows to control stress-strain state of the "loaded" ceramics and to slow down process of its degradation. The developed method of designing of details taking into account ceramics degradation at exploitation is described.

Abstract: Present article report synthesis and spectroscopic analysis of BiVO₄ nanophosphor doped with trivalent Eu ions. It was observed that BiVO₄ nanocrystals shows higher yield in comparison with the as-made nanocrystals on 266 nm laser excitation. On 266 nm excitation, emission composed of red dominated wide spectrum in the range of 400-950 nm was reported. Emission intensity enhanced five times on annealed sample than the counterpart. Time resolved analysis explores significant alteration in excited state relaxation process due to annealing. Detailed photo physics involved to improve optical emissions has also been explained.

Abstract: Eutrophication as a result of uncontrolled phosphorus (P) concentration that is released in wastewater has emerged as a major problem nowadays. Treatment of P demands high costs specifically to its chemical and maintenance needs. A lot of efforts were undertaken to find the most economical material that can treat P such as Electric Arc Furnace Slag (EAFS), a by-product from steel industry and Limestone (LS), and a natural resource that can be easily obtained from sedimentary rock. Despite numerous study conducted previously, the mechanism of P removal between these two materials have not been explored yet in detail. Therefore, an experimental work had been designed to evaluate the performance of P removal mechanism between the EAFS and LS lab-scale filter systems which can offer the best removal in overall. In this study a column lab scale of vertical rock filters in 100 mm diameter × 400 mm height were constructed for both EAFS and LS filters. The observation period was conducted for 2.5 months utilizing synthetic phosphorus concentration of 25 mg/L as its initial concentration. Working condition of the experiment was adjusted at pH 4.5 to 7.5 under 26.8±0.64 °C. X-ray fluorescence (XRF) analysis was also performed in order to determine chemical composition of EAFS and LS media. Results revealed that EAFS showed a significant effect on the removal of P mechanism compared to the LS filter system. The highest removal of P for both filter systems were observed to achieve 90% (pH 5) in the EAFS compared to only 68% (pH 4.5) in the LS system. This may be associated with the dissolution of Ca, Fe and Al elements in the EAFS that promotes precipitation process and hence gave higher removal compared to the LS element (only Ca has the highest percentage = 91%). At lower pH (acidic) condition the soluble metal salts react with phosphate ion to form phosphate hydrolysis product thus promoting precipitation in the system. In conclusion, it is predicted that precipitation may occur within the filter systems predominantly in the EAFS filter as pH was change from acidic to alkaline (4.5 – 7.5) due to dissolved (Al³⁺, Ca²⁺, Fe³⁺) within the filter system. Nevertheless, it is recommended that future study should be carried out on the precipitates salts through X-ray diffraction (XRD) analysis so as the existence of phosphate and metal salts as a result of precipitation can be finally confirmed.

Abstract: A series of experiments have been done to evaluate the way an electrode wire feed affects residual stresses in welded joints. It was found that an electrode wire pulse feed combined with shielding gases decreases residual stresses up to two times in comparison with welding with a continuous feed of an electrode wire.

Abstract: This research paper deals with an experimental investigation of mechanical properties of prepared composite panels. Flexural behavior in three-point bending test is measured. Composites are prepared in order to satisfy requirements for transport industry. Totally, three material compositions are tested with different multiaxial reinforcing fabric and polyester resin. All samples are produced by low-pressure vacuum infusion mainly used for large-scale composite parts. Furthermore, fire resistance of prepared laminates is tested and appropriate classification into corresponding categories is also done. Experimental results proved suitability of prepared glass fiber composites for application in transport industry.

Abstract: In this article we treat a pathological problem for a better understanding of the phenomena of ASR; the modeling of ASR has been represented in a relative element of volume (REV) in mesoscopic scale. The method used to estimate the formation of ASG is the kinematic estimation of the ASR where it generates in the end an expansion, thus modeling leads to a better range of understanding of the rheological behavior of a concrete with ASR.The numerical model adopted to validate the effect of the expansion of alkali silica gel in terms of strain/stress is a phenomenological one, where it gives sustainable results with the rheological models.

Abstract: This work aims to investigate the effect of recycled material and effect of particle size on the mechanical properties of the recycled material. Tested material is polyamide 6. Every manufacture of any plastic parts produces certain amount of waste, such as defective injects or cold runner system from injection molding technology. When size of this material is reduced, particles of different sizes are made. From large particles similar to the original granulate material, to dust particles. This size variation can cause problems during subsequent processing. These particles of different size have distinct melting rate. To determine behavior of recycled material at room temperature. Impact toughness and hardness tests are performed.

Abstract: The aim of this research is to show influence of particle size of recycled polymeric material to mechanical tensile properties. During grinding, the particles with various sizes are formed, from larger pieces to dust particles. This size variation can cause problems during subsequent processing. These particles of different sizes have distinct melting rate. That can cause an inhomogeneity of a melt and diverse structure of a solidified polymer. Several recycled mixtures with varied particle size after crushing were prepared. Tested polymer was polyamide 6 and the tests were performed at ambient temperature.

Abstract: The aim of this article is to demonstrate and asses to what extent there is an impact on the mechanical properties of a standardized testing sample made of rubber compound based on synthetic rubber EPDM and produced by injection molding in comparison with a sample produced by classic preparation (cutting off a compression molded plate) according to the standard ISO 23529.