Papers by Keyword: Free Surface

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Authors: Xiong Jun He, Yan Huang, Min Lan, Sheng Ping Jin, She Sheng Zhang
Abstract: A basic mathematic model of ship section added mass is important for the ship dynamics research. According to the fluid dynamics control equations, the numeric formula of added mass is derived by using Green function. The representation form of added mass is discussed on basic domain of integral function.
Authors: Rafal Abdank-Kozubski, Andrzej Biborski, Mirosław Kozłowski, Christine Goyhenex, Veronique Pierron-Bohnes, Mebarek Alouani, Marcus Rennhofer, Savko Malinov
Abstract: Chemical ordering kinetics in L10- and B2-ordered AB binary intermetallics was simulated by means of Monte Carlo (MC) technique implemented with vacancy mechanism of atomic migration. While vacancy concentration is usually much lower than the antisite defect concentration in L10-ordered systems, triple defects are generated in particular B2–ordered systems. The latter definitely affects the chemical ordering process and requires that full thermal vacancy thermodynamics is involved in B2-ordering simulations. The study on L10-ordered binaries was dedicated to FePt thin layers considered as a material for ultra-high-density magnetic storage media. Metastability of the L10 c-variant with monoatomic planes parallel to the layer surface and off-plane easy magnetization was revealed. Thermal vacancy formation in B2-ordered binaries was modelled by implementing a mean-field Hamiltonian with a specific formalism of phase equilibria in a latticegas composed of atoms and vacancies. It was demonstrated that for particular pair-interaction energetics, equilibrium concentrations of vacancies and antisites result mutually proportional in well-defined temperature ranges. The MC simulations of B2-ordering kinetics involved the modelled equilibrium vacancy concentration and reproduced the experimentally observed low rate of the process.
Authors: Xiao Jun Wu, Shu Dong Sun, Chao Zheng
Abstract: Die and mold are constructed with various free surfaces. In the machining of die and mold, it takes a long time to finish the curved surface. In this study high accurate polishing technique by GC (grinding center) with elastic ball type wheel is developed. In polishing process it is very important to remove cusp height without decreasing machined form accuracy. It is available to use GC in free surface grinding and finishing of die and mold with elastic ball type wheel. In polishing process only cusp height is removed in order to keep form accuracy that is produced in cutting process with ball end mill. In order to know the polishing characteristics of elastic ball type wheel, basic experiments were conducted. The polishing parameters Sp. were obtained experimentally by changing the values of polishing process. Using polishing parameter, removal amount can be obtained and polished surface is possible to estimate.
Authors: Shuang Yi, Guang Xian Li, Song Lin Ding, John Mo
Abstract: Recently, titanium alloys have been widely used in industry owing to their excellent physical and mechanical properties. However, the severe cutting conditions such as abrasion, adhesion and high temperature accelerate the rate of chip formation and strongly affect the quality of machined surface. This paper investigates that the effect of the conventional coolant (CC) and graphene oxide suspended (GO) on the drilling process of titanium alloy Ti-6Al-4V using tungsten carbide tools. Here are two main chip formation could be found that zigzag chips and spiral chips. Through the analysis of chip morphology, it was found that under graphene oxide suspended fluid. It can be found that using conventional coolant would form the zigzag chips, while it formed spiral chips when graphene oxide suspended fluid applied. In addition, by analysing the chip free surfaces, the chip lamella stuck and chip flaw happened when conventional fluid used. While the back surfaces could be found that less chip stuck and crack occurred when graphene oxide suspended coolant applied. Finally, chip thickness were investigated that thinner chip thickness was found when graphene oxide suspended fluid used.
Authors: Jian Jun Wu, Wen Zhen Fu
Abstract: On the fitting process simulation, the dangerous area related with buckling or tearing phenomena is identified with special colors and values, then deleting, cutting line designing, refitting and spreading processes are implemented to obtain a reasonable blank shape with dart feature. Moreover, a so called expanding surface method was presented in order to realize the fitting and spreading of free surface with hole feature. The above provided methods are realized through software codes and used in some cases effectively.
Authors: Akiyuki Takahashi, Naoki Soneda, A. Nomoto, G. Yagawa
Abstract: This paper describes dislocation dynamics simulation of grain boundary effects on yield behavior of metals, such as α-Fe bcc metal. Since the stress field arising from the grain boundary has not been well understood yet, the geometrical effect of the grain boundary can be handled in the simulation by the use of rigid boundary condition. The dislocation pileups can be observed near the grain boundary in the result of the DD simulation. And the yield stress in the crystal having the grain boundary becomes larger than that in the crystal having free surface. This result tells us that the Hall-Petch effect can actually describe well the effects of the grain boundary on the yield behavior of metals.
Authors: Jiří Šafka, Martin Lachman, Petr Zelený, Martin Seidl
Abstract: The paper deals with multi-axis machining of complex shapes of freeform surfaces. Machining of such surfaces is very difficult and the critical operation is the optimal setting of tilt and lead angle which, along with other parameters, must ensure collision-free machining. This paper describes the possible dividing of solved freeform surface areas into partial elements with similar properties from CAD data using Matlab software instruments. The partition is solved by algorithms calculated according to the curvature of the surface using both methods the maximum and the Gaussian curvature. These partial elements can be machined separately which allows employment of tools with optimal dimensions for individual elements. This process enables significant reduction of tool-path necessary for machining these shapes which also leads to reduction of the working time. Furthermore, there are practical examples including a comparison of standard method and the use of machining process optimized by the algorithm in this article.
Authors: D.M. Pedroso
Abstract: Partial differential equations such as models for flow in unsaturated porous media are difficult to be solved when space-time variable boundary conditions are included. A general solution to this problem is discussed in this contribution and is devised in such a way that the face with variable boundary condition can be subjected to Dirichlet, Neumann or the so-called Signorini/ambiguous boundary conditions, considering the transition from one type to another. A method based on the enrichment of finite elements that is able to accurately model seepage with these complex boundary conditions is discussed. Simulations are presented illustrating the capabilities of the new method in 2D and 3D, including cases where the free surface varies due to rain.
Authors: Arkadeep Kumar
Abstract: Granular materials have widespread use in the industry. The flow of granular media requires careful studies through experiments to understand the rheology of these complex materials. The present work determines the surface profile of dense granular media subjected to cylindrical Couette flow. A translation stage is used to obtain measurement of depth varying with radial distance. A depth gauge attached to the translation stage is used to measure the surface profile. Glass beads (average diameter 0.8-1 mm) and mustard seeds (average diameter 1.2-1.4 mm) are used as model granular materials. Two different Couette gaps are used (4cm and 3cm). Cylinders with smooth surfaces, as well as coated with emery paper are used. The surface profile varies with material, surface roughness of the cylinders, and the gap between the two cylinders. The comparison of the various cases has been done by graphical representation. The probable reasons for the development of such a surface profile are given.
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