1,721,378 research outputs found
Al-Mg-Y와 Al-Ni-Y 3원계 합금의 비정질형성 영역의 열역학적 계산
No full textThe glass forming ranges of the ternary Al-Mg-Y and Al-Ni-Y systems have been predicted and compared with experimental measurements. A thermodynamic method (CALPHAD method) has been used to obtain T_o curves of five bounding binary systems, Al-Ni, Ni-Y, Y-Al, Al-Ni and Ni-Y, and ternary Al-Mg-Y and Al-Ni-Y systems. Glass transition temperature T_g in these systems has been approximated by crystallization temperature T_x, which was derived from the relationship with hole formation enthalpy. Based on the magnitude between T_o and T_g, the glass forming range has been determined. The range has been calculated to be rather wide because of the upper limit concept for T_g. This approach can be used as a guide to predict the glass forming range of binary, ternary and even multicomponent systems
In situ observation of fracture sequence of physical vapor deposited TiN film on (11(2)over-bar-0) sapphire
No full textThe critical parameters for the structural stability of physical vapor deposited TiN film on (11 (2) over bar0) sapphire were investigated by analyzing the adhesion strength and failure mechanism through in situ observations of the fracture sequence during scratch tests and static normal indentation. TiN was deposited by arc ion plating on (11 (2) over bar0) sapphire, and the thickness of the TiN film was controlled to 700 nm. Delamination of TiN film was monitored in situ from below the contact through a transparent sapphire substrate, using zoom optics mounted into a video imaging sensor. In situ observation enables us to detect the failure origin of TiN coating on sapphire. The failure origin of TiN film on (11 (2) over bar0) sapphire was identified as both rhombohedral and basal twinning of the sapphire substrate. Rhombohedral twinning was initiated first, and basal twinning ensued. Twinning-induced plastic deformation of the sapphire substrate triggered the initiation of interfacial delamination of the TiN coating. The plastic deformation of the substrate ultimately induced failure of the protective coating.This work was supported by a grant for International
Collaboration Research Program from Korea Ministry of
Science and Technology (M6-0105-00-0012)
Influence of fabrication residual thermal stresses on rubber-toughened adhesive tubular single lap steel-steel joints under tensile load
No full textThe tensile load bearing capability of adhesively-bonded tubular single lap joints which is calculated under the assumption of Linear mechanical adhesive properties is usually much less than the experimentally-determined because the majority of the load transfer of adhesively-bonded joints is accomplished by the nonlinear behavior of rubber-toughened epoxy adhesives. Also, as the adhesive thickness increases, the calculated tensile load bearing capability with the linear mechanical adhesive properties increases, while, on the contrary, the experimentally-determined tensile load bearing capability decreases. In this paper, the stress analysis of adhesively-bonded tubular single lap steel-steel joints under tensile load was performed taking into account the nonlinear mechanical properties and fabrication residual thermal stresses of the adhesive. The nonlinear tensile properties of the adhesive were approximated by an exponential equation which was represented by the initial tensile modulus and ultimate tensile strength of the adhesive. Using the results of stress analysis, the failure criterion for the adhesively-bonded tubular single lap steel-steel joints under tensile load was developed, which can be used to predict the load-bearing capability of the joint. From the failure criterion, it was found that the fracture of the adhesively-bonded joint was much influenced by the fabrication residual thermal stresses
Tradable tagged permit system for global pollution control
No full textWe propose a new tradable permit system, called "tradable tagged permit system" (TTPS), which is specifically geared to global environmental issues of long-term dynamics. This is an extended emission permit system composed of various types of permits, one for each country or class of countries. It induces countries to reveal their damages, in addition to the costs, through their permit prices. It is shown that this achieves a Pareto-superior outcome than without the system, and that the repeated application of this scheme converges to the global first-best steady state. A numerical analysis with empirical data shows that TTPS achieves most of the potential gains from global cooperation, even with an initial allocation scheme based on voluntary pledge levels that gives participation incentives for all countries. (C) 2001 Society for Policy Modeling. Published by Elsevier Science Inc
STUDY ON THE POSSIBLE EXISTENCE OF MULTIPLICITY FEATURES IN ETHENE HYDROGENATION OVER PLATINUM BOEHMITE CATALYSTS
No full textThe possible existence of multiplicity features, including ignition and extinction phenomena, are examined in ethene hydrogenation over a very short fixed bed of platinum/boehmite catalysts. Ethene hydrogenation is compared with carbon monoxide oxidation for which it has been claimed in several studies that multiple steady states can occur within the kinetic region. In our experiments an important experimental parameters is the size of the catalyst charge in the reactor. In ethene hydrogenation the multiplicity feature cannot be observed below a certain size of catalyst charge. On the other hand, in carbon monoxide oxidation this multiplicity can be observed regardless of catalyst charge size. From our observations, it is concluded that the multiplicity in ethene hydrogenation cannot be attributed to a purely kinetic process, but it results from the interaction of the chemical reaction and the heat transfer process
MANUFACTURING OF THE COMPOSITE SCREW ROTORS BY RESIN TRANSFER MOLDING
No full textA screw-type pump with at least two rotors that ale composed of male and female rotors with helical extending lands and grooves is increasingly used because it has a smaller weight to power ratio and produces less noise and vibration compared to conventional reciprocating pumps. Most male and female rotors of the screw type pump have been manufactured by machining. The manufacturing time is long because the amount of material cut-away is considerable and the manufacturing cost is high because the screw rotors have a complicated shape and require high degree of accuracy in machining. Therefore, there are many attempts to manufacture the screw rotors with plastics and ceramics using different manufacturing methods such as injection molding and casting. Since the lands of rotors manufactured with polymer composite materials have resilient deflecting characteristics when clashed with other rotors, in this paper, the composite screw rotor was manufactured with chopped carbon fiber reinforced epoxy composite materials by resin transfer molding. The interfacial strength between the screw and the aluminum core shaft was tested with respect to the knurling size of the surface of the aluminum core shaft and the surface treatment. Also, the flexural strength and coefficient of thermal expansion were tested. Using the measured data, the composite screw rotors were manufactured by resin transfer molding
An upper-bound solution for axisymmetric extrusion of composite rods through curved dies
No full textThe study is concerned with an analysis of forward extrusion of composite rods through curved dies. A kinematically admissible velocity field is derived by assuming proper streamlines and applying the flow function concept to each material region of plastic deformation. Two kinds of flow functions are chosen in order to compare the effect of the choice of the flow functions. The effect of work-hardening is incorporated approximately by calculating the strains at the exit of both materials. The upper-bound method is then employed to determine the extrusion pressure for various process variables. The experiments are carried out with commercially pure aluminum and copper billets for various reductions of area and cone angles at room temperature. The experimental results are then compared with the theoretical calculations. The comparison shows that the second-order flow function is in better agreement with the experimental observation both in extrusion loads and in deforming regions
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