Applied Mechanics and Materials Vols. 752-753

Abstract: The paper describes the experimental tests of steel bearing elements, which were aimed at obtaining material, geometric and strength characteristics of the fillet welds. Preparation of experiment consisted in defining of numerical models of tested samples using FEM analysis and the commercial software ANSYS. Data obtained from described experimental tests are necessary for further numerical modelling of stress analysis of steel structural supporting elements.

Abstract: In this paper, depending of the blocking temperature on magnetite core size for core/shell nanoparticles has been carried out using our theoretical model. Nanoparticles has size of 100nm, and magnetite core increases from 0nm to 100nm. Systems were studied with different values of exchange constant. The data obtained indicate that exchange constant increases the blocking temperature. However, the sign of the constant does not matter.

Abstract: This paper deals with influence of surface shape on light absorption. The study was performed on polyvinylchloride samples with different grooves. It was investigated the influence of shape, width, depth and number of grooves on light absorption. The investigated material samples were produced on CNC milling machine. Experimental measurements of light absorbance were performed under diffuse daylight on the basis of illuminance ratio. Different factors, that have influence on light absorption, are evaluated in the conclusion of this work. It was found that the lowest light absorbance was obtained in case of the smooth polyvinylchloride sample. The material machining causes multiple reflections of light from groove surfaces. For this reason the light absorbance of the groove surfaces is higher compared to the smooth material sample.

Abstract: The article deals with a problem of racking strength and stiffness of timber based two-by-four wall systems insulated with polyurethane foam. There are racking strength and rigidity tests described in the main part of the work. Results of performed tests are compared to calculation of the racking strength according to national standard.

Abstract: This article intends to present the pavement response analysis due to the 18-axles special truck used to transport a 400 tons generator parts. According to the DOH Declarations issued in 2005, DOH had issued the additional declarations containing special trucks or vehicles for overloaded transportation, proper axle and gross weights of each type of vehicles. However, the strain of the special truck must be less than the standard Thai truck (Truck25). The typical asphalt pavement is modeled and performed based on layered elastic analysis theory. The pavement is loaded with 18-axle truck. The maximum tensile strains under asphaltic concrete layer and compression strains on base, subbase, selected material and subgrade for special truck load are 234.4 ,618.1, 494.4, 422.9, and 772.3 με, respectively. However, the maximum compressive strains on selected material and subgrade of the special 18-axle truck was exceeded the standard Thai truck.

Abstract: The paper presents behavior of molten carbonate fuel cell fueled by ash free coal. Comparison between AFC and hydrogen as a fuel for MCFC is presented. Then, simulation gases expected from gasified ash free coal were investigated. The simulations were provided for different composition of gases based on results of AFC gasification. Current-voltage curves for investigated cases are presented as well as results are discussed.

Abstract: A Fire assay is method to verify the fineness of gold with use lead in its process. In this research, Bi-Ag sandwich sheets for a lead-free fire assay method were developed. Bi-Ag sandwich sheets were produced by a hot-dipping method at temperature 300 °C and 400 °C. Samples were characterized the microstructure by SEM along the process. A fire assay method was used to verify and correlate the results of gold fineness to various kinds of wrapping sheets which are Bi-Ag sandwich sheets and lead. The Bi-Ag sandwich sheets shows the layer of 14-20 µm at 300 °C and 8.5-10.5 µm at 400 °C. After cupellation process, the metal beads were observed by SEM and mapping techniques to analyze the remained copper. XRF characterization was confirmed the results of compositions showing an increasing amount of copper as increasing temperature dipping on Bi-Ag sandwich of 0 wt%, 1.58 wt% and 1.34 wt% at S1, S2 and S3, respectively. Higher amounts of copper left on bead buttons consisted with the accuracy of fire assay results which were S1, S2 and S3 obtaining 99.99 wt%, 99.87 wt% and 100 wt% of gold, respectively.

Abstract: This contribution analyses influence of thermo mechanical conditions of magnesium alloy - type AZ31 forming on its flow stress. Temperature and strain/deformation rate belong to the essential thermo mechanical parameters of strain/deformation process. A testing cylinder made of selected Mg alloy was strained using pressure at warm temperatures within defined two degrees of nominal strain 30% and 60% and strain rate of 5 s^-1. The pressure test at warm temperatures was conducted at testing temperatures 250, 300 and 350°C. It is important to explore the temperature influence on AZ31 alloy flow stress in order to reduce energy consumption of formed pieces production. Surface quality and precision of required dimension will improve, as well. The experiment was aimed at graphic evaluation of temperature influence on flow stress of Mg alloy AZ31B. Resulting form flow stress curve it is possible to read out its value for particular strain. These values are essential for calculation of forming force and work. For magnesium alloy AZ31 warm forming at temperature interval of 230 - 425°C is typical. The pressure tests were realized within the temperature interval of 250 - 350°C, i. e. at temperatures belonging to lower limit of recommended temperature interval, with the aim of acquirement as much information as possible on Mg alloy behavior at low forming temperatures.

Abstract: The result of direct ablation of silicon by an 800 nm Ti:Sa femtosecond laser pulses are presented. Obtained slice of silicon with submicron roughness with tilt focused femtosecond laser pulses. Yaw cut more due to mechanical vibrations of the entire installation on a pneumatic table, but not the physics of the ongoing process. During processing, possibly thinning the silicon sample from the opposite edge (sharpening) to submicron values ​​(tens of nanometers).

Abstract: Heat transfer augmentation techniques ultimately results in the reduction of thermal resistance in a conventional heat exchanger by generating higher convective heat transfer coefficient. Present study with the use of Alumina (Al₂O₃)/water nanofluid and baffled twisted tape inserts in double pipe heat exchanger as compound augmentation technique. Experiments were conducted to evaluate the heat transfer coefficient and friction factor for the flow through the inner tube of heat exchanger in turbulent flow range (8000<Re<60000). The effect of rectangular, circular, triangular baffled twisted tape having twist ratio (y/w) 4.2 and twisted tapes without baffles of twist ratio (y/w) 4.2 and 5.2 were studied. Experiments were conducted for both water and 0.1% volume concentration Alumina/water nanofluid. It is found that the enhancement of heat transfer coefficient by using rectangular baffled twisted tape and nanofluid is about 20%. Performance evaluation criteria were found for water and nanofluid and it was observed that rectangular baffled twisted tape performs better than other twisted tapes.