An Investigation on the Mechanical Properties of Aluminium 6061 Alloy Reinforced with Boron Carbide and Silicon Carbide

Aluminium alloys are widely utilised in the aerospace and automobile industries due to their low density and strong mechanical qualities, as well as their superior corrosion and wear resistance and low thermal coefficient of expansion as compared to traditional metals and alloys. These material’s superior mechanical qualities and inexpensive production costs make them an appealing alternative for a wide range of scientific and technical applications. In this study, we strive to present a literature review on the overall performance of reinforced composites created by the stir casting method, as well as the effect of process factors on the properties of Aluminium-based MMC. The literature review framework in this paper provides a clear overview that the process parameters play important role for optimum properties of Aluminium based Metal Matrix Composites. As reinforcing elements in Metal Matrix Composites, Boron Carbide and Silicon Carbide play an important role. The MMCs were successfully produced using the liquid metallurgy process. Scanning electron microscopy was used to examine the morphology and microstructure of Al-B4C and Al-SiC composites. The addition of 2, 4 and 6 wt% B4C and SiC particles increased several mechanical parameters such as ultimate tensile strength and hardness. It was also discovered that the mechanical behaviour of B4C particulates AMC is superior to that of SiC particulates AMC. Keywords: Aluminum, Metal matrix composite, SiC, B4C, Tensile test, Hardness test and SEM Analysis.

ALGORITHMIC SUPPORT FOR DECISION-MAKING ON THE EFFICIENCY OF OPERATION OF ABSORPTION AND REFRIGERATION PLANTS OF AMMONIA PRODUCTION

The features of the hardware and technological design of the AM-1360 series ammonia synthesis units operating in Ukraine are established, the main of which is the use of heat-using ammonia-water absorption and refrigeration units in the secondary condensation complex. The analysis of the functioning of the absorption and refrigeration units has been carried out. A significant dependence of their efficiency on external disturbances, such as temperature and humidity of atmospheric air, has been established. This causes significant fluctuations in the cooling temperature of the circulating gas in the evaporators of absorption-refrigeration units, which significantly affects the efficiency of ammonia production in general. Based on the results of the analysis of the existing information system, implemented on the basis of the TDC-3000 microprocessor complex, recommendations for its improvement were developed, the presence of which makes it possible to abandon daily analyzes and carry out only control ones to check measuring instruments. Algorithmic support has been developed, implemented in the MATLAB package and tested according to the data of industrial operation of absorption and refrigeration units of the ammonia synthesis unit. This allows the operator, in real production conditions, to obtain operational information on the numerical indicators of the efficiency of operation of absorption and refrigeration units, which characterize their operation to the greatest extent (circulation rate, cooling capacity, circulating gas cooling temperature and thermal coefficient) and make a decision on the possibility of reducing the cooling temperature. of circulation gas in evaporators by changing the frequency of circulation of solutions The created algorithmic software in the MATLAB environment allows embedding a client module, the so-called OPC client. The latter provides technology for free programming of access to current data.

Energy efficiency of an absorption thermotransformer with two-stage absorption as part of a heat and cold supply complex based on a gas boiler house

The article proposes a scheme for using a lithium bromide absorption thermotransformer (LBATT) with two-stage absorption for deep utilization of the heat of combustion products (CPs) of gas boilers. At the same time, this solution allows heating the dictrict heating systems return water in the cold season. In the warm season, LBATT is used to cool the water of the air conditioning system or process equipment cooling. In this case, heat removal from LBAHT with two-stage absorption in the warm season is carried out using an drycooler. The analysis of the effectiveness of the use of LBATT in the cold and warm seasons is carried out. The theoretical transformation coefficient of LBATT with deep utilization of flue gases reaches 1.72. The theoretical thermal coefficient of LBATT when cooling water in the warm season reaches a value of 0.7.

Advanced Materials for Radiation Dosimetry

<p>The motivation for this work was to find materials that have the following characteristics: good optical transparency, rapid read-out, automation of read-out, good fading characteristic, promise high sensitivity to ionising radiation, and tissue equivalence for use in medical applications. For example, there are medical applications in brachytherapy and high-energy photon therapy for the treatment of cancer. These applications benefit small dosimeters for monitoring radiation during radiotherapy or for dose verification and validation. This thesis studies fluoroperovskite materials that were manufactured as bulk materials or nanoparticles. The techniques of photoluminescence (PL), radioluminescence (RL), thermoluminescence (TL) and optically stimulated luminescence (OSL) were employed in order to get a deeper understanding of the defect distribution in these materials. A detailed model of the trap distribution was developed from the results of these measurements. It was observed that compared to the bulk materials, the nanoparticles show a lower PL lifetime and less dependence on the dose of the RL intensity, which is due to the different defect distribution. The nanoparticles also demonstrate more low temperature peaks in the TL glow curves. PL and RL measurements of Eu3+ doped samples show that the crystal environment of the Eu3+ in the bulk material is more distorted than for the nanoparticles. For the bulk materials, the thermal coefficient of the RL is <0.4 %/K, which is a desirable property of real -time dosimeters. The thermal coefficient of the RL in the nanoparticles has a high uncertainty ( 7 %/K) compared to the bulk materials ( 0.4 %/K). For the fluoride nanoparticles, it was observed that the PL lifetimes for the LaF3 decreases with increasing rare earth concentrations. This can be attributed to energy transfer from luminescence ions in the core to luminescence ions near the surface followed by non-radiative decay. In comparison, the decrease of the PL lifetimes of RbMgF3 and NaMgF3 is predominantly due to non-radiative recombination centres inside the crystal.</p>

Advanced Materials for Radiation Dosimetry

<p>The motivation for this work was to find materials that have the following characteristics: good optical transparency, rapid read-out, automation of read-out, good fading characteristic, promise high sensitivity to ionising radiation, and tissue equivalence for use in medical applications. For example, there are medical applications in brachytherapy and high-energy photon therapy for the treatment of cancer. These applications benefit small dosimeters for monitoring radiation during radiotherapy or for dose verification and validation. This thesis studies fluoroperovskite materials that were manufactured as bulk materials or nanoparticles. The techniques of photoluminescence (PL), radioluminescence (RL), thermoluminescence (TL) and optically stimulated luminescence (OSL) were employed in order to get a deeper understanding of the defect distribution in these materials. A detailed model of the trap distribution was developed from the results of these measurements. It was observed that compared to the bulk materials, the nanoparticles show a lower PL lifetime and less dependence on the dose of the RL intensity, which is due to the different defect distribution. The nanoparticles also demonstrate more low temperature peaks in the TL glow curves. PL and RL measurements of Eu3+ doped samples show that the crystal environment of the Eu3+ in the bulk material is more distorted than for the nanoparticles. For the bulk materials, the thermal coefficient of the RL is <0.4 %/K, which is a desirable property of real -time dosimeters. The thermal coefficient of the RL in the nanoparticles has a high uncertainty ( 7 %/K) compared to the bulk materials ( 0.4 %/K). For the fluoride nanoparticles, it was observed that the PL lifetimes for the LaF3 decreases with increasing rare earth concentrations. This can be attributed to energy transfer from luminescence ions in the core to luminescence ions near the surface followed by non-radiative decay. In comparison, the decrease of the PL lifetimes of RbMgF3 and NaMgF3 is predominantly due to non-radiative recombination centres inside the crystal.</p>

Development of MEMS Composite Sensor with Temperature Compensation for Tire Pressure Monitoring System

The pressure and temperature inside the tire is mainly monitored by the tire pressure monitoring system (TPMS). In order to improve the integration of the TPMS system, moreover enhance the sensitivity and temperature-insensitivity of pressure measurement, this paper proposes a microelectromechanical (MEMS) chip-level sensor based on stress-sensitive aluminum-silicon hybrid structures with amplified piezoresistive effect and temperature-dependent aluminum-silicon hybrid structures for hardware and software temperature compensations. Two types of aluminum-silicon hybrid structures are located inside and outside the strained menbrane to simultaneously realize the measurement of pressure and temperature. The model of this composite sensor chip is firstly designed and verified for its effectiveness by using finite element numerical simulation, and then it is fabricated based on the standard MEMS process. The experiments indicate that the pressure sensitivity of the sensor is between 0.126 mV/(V·kPa) and 0.151 mV/(V·kPa) during the ambient temperature ranges from -20 ℃ to 100 ℃, while the measurement error, sensitivity and temperature coefficient of temperature-dependent hybrid structures are individually ± 0.91℃, -1.225 mV/(V·℃) and -0.150%/℃. The thermal coefficient of offset (TCO) of pressure measurement can be reduced from -3.553%FS/℃ to -0.375%FS/℃ based on the differential output of the proposed sensor. In order to obtain the better performance of temperature compensation, Elman neural network based on ant colony algorithm is applied in the data fusion of differential output to further eliminate the temperature drift error. Based on which, the overall measured error is within 3.45 kPa, which is less than ±1.15%FS. The thermal coefficient of offset (TCO) is -0.017%FS/℃, and the thermal coefficient of span (TCS) is -0.020%/FS℃. The research results may provide a useful reference for the development of the high-performance MEMS composite sensor for the TPMS system.

Моделювання та програмний комплекс для дослідження функціонування ежектора в змінних режимах

One of the current directions of development of modern energy-saving and energy-efficient technologies for ship and stationery (including municipal) energy is the use of ejector refrigeration machines, which can be used for air conditioning systems together with an absorption refrigeration machine (cascade cycle) or vapor compressor refrigeration machine as part of cogeneration or trigeneration units. Such circuit solutions can be used together with ensuring the rational organization of work processes in the main elements of the refrigeration machine, in particular in the jet device - ejector, the appropriate design of which, in turn, will further increase the thermal coefficient. Improving the design of the ejector is a rather complex and long process and does not always give positive results. It is primarily because many tests are required on full-scale models. Therefore, computer simulation of the ejector operation at different variable input parameters, considering the geometric characteristics of the flow part and variable mode characteristics during operation is more attractive in terms of finding options for rational (optimal) design. The paper presents the results of software development for modeling hydrodynamic processes in the flowing part of the ejector, considering the variable operating modes of the ejector refrigeration machine. The existing method for calculating the pressure and circulation characteristics of jet devices is used. The developed software complex "RefJet" in the design mode defines the maximum achievable coefficients of ejection of a jet ejector. In the simulation mode - provides determination of the ejection coefficients of the already designed (certain sizes) ejector at variable values of pressure at the inlet and outlet in specific operating conditions, considering its operation at the limit and partial modes. The work of the software package was tested in the development and analysis of circuit solutions of ejector refrigeration machines as part of the heat recovery circuits of three-generation units based on internal combustion engines and gas turbine engines.

Formation, Phase Stability, and Characterization of Unstabilized Aluminum Titanate (Al2TiO5) Ceramics

In the present study, Al2TiO5 was prepared via the sol–gel technique then sintered at 1000°C to 1300°C for 1 h. The thermal stability of the formed ceramic bodies was explored. The densification parameters, microstructure, and phase composition of the sintered Al2TiO5 ceramic were examined, and the mechanical properties and thermal coefficient were characterized. The phase composition study revealed the presence of alumina and TiO2 residuals up to 1100°C. Phase stability was observed in Al2TiO5 bodies sintered up to 1300°C. The vitrification behavior of the bodies was improved by increasing the sintering temperature. The thermal expansion coefficient of the sintered samples sintered at 1300°C was enhanced by the formation of rod-like Al2TiO5 grains. Increases in the bending strength (from 22.40 to 28.90 MPa) and hardness (HV0.1; from 1467 to 1873) were observed when the treatment temperature was increased from 1000°C to 1300°C.

Sensitivity analysis on deformation of woven polyethylene formwork

The use of different material quality and amount can affect formwork performance at the beginning of casting. Practical easy to install formwork such as woven polyethylene with wire mesh reinforcement makes field work easier. Sensitivity analysis on the elastic modulus and the thermal coefficient variables of woven polyethylene, fresh concrete temperature during casting and fresh concrete load model are the objectives of this research. The research is performed by comparing experimental data and the numerical modeling of woven polyethylene formwork using Finite Element Method. The formwork span and width dimension are 1 m x 0.3 m, with a variety of heights namely 0.6 m, 0.45 m, and 0.3 m. The sensitivity value for each variable will be evaluated based on Pearson coefficient or R. The sensitivity analysis of thermal coefficient showed no correlation to changes in formwork deformation. The sensitivity analysis of elastic modulus and fresh concrete temperature showed perfect correlation to changes in formwork deformation although the changes are small (around 0.0003 cm to 0.0006 cm). The fresh concrete load model showed perfect correlation to formwork deformation as well as becoming the determining variable of the changes in the formwork deformation values.

Experimental study of the thermophysical properties for aluminum-magnesium alloy AMg3

The thermal diffusivity (a), the thermal coefficient of linear expansion (α), the isobaric heat capacity (cp ) and the fusion enthalpy (ΔH) of aluminum-magnesium alloy AMg3 were investigated by laser flash method, dilatometric method and method of differential scanning calorimetry in the temperature range of 300–773…1000 K. The thermal conductivity (λ) has been calculated from the measurement results. The estimated errors of the obtained data were 2–5%, 3–5%, 2–3% and (1.5–2.0)⋅10-7 K-1 for a, λ, cp and α, respectively. Approximation equations and a table of reference values for the temperature dependence of the studied properties have been obtained.