Papers by Keyword: Modeling

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Authors: Quan Ping Sun, Hai Bing Wu, Qian Liang Chen
Abstract: In order to control cutting depth of preheating ZrO2 sintered ceramics accurately, linear expansion elongation of preheating ZrO2 multiple phase is measured; on the base of the measured data a mathematical model of thermal expansion coefficient given at different preheating temperature is put forward. Its fitting-error from-9μm to +2μm is very small compared to the data of linear expansion elongation measured. Some milling experiments that cutting force is following preheating temperature have been done by the amending cutting-depth from the model. The experimental results show that the cutting performance of ZrO2 sintered ceramics preheated not only turns better but also extends cutter life.
Authors: Xi Bing Li, Chang Long Yang, Gong Di Xu, Wen Yuan, Shi Gang Wang
Abstract: With heat flux increasing and cooling space decreasing in microelectronic and chemical products, micro heat pipe has become an ideal heat dissipation device in high heat-flux products. Through the analysis of its working principle, the factors that affect its heat transfer limits and the patterns in which copper powders are arrayed in circular cavity, this paper first established a mathematical model for the crucial factors in affecting heat transfer limits in a circular micro heat pipe with a sintered wick, i.e. a theoretical model for capillary limit, and then verified its validity through experimental investigations. The study lays a powerful theoretical foundation for designing and manufacturing circular micro heat pipes with sintered wicks.
Authors: Andreas Nau, Berthold Scholtes
Abstract: There is a strong need for reliable residual stress measurements. On the one hand, residual stresses can be beneficial, when they are adapted to external loads. On the other hand, they can be detrimental, when they are unknown. Thus, their occurrence can lead to an uneconomical oversizing of components or in their failure, as well. Apart from diffraction methods, mechanical methods are well recognized in order to determine unknown residual stress states. Depending on the applied method, specific boundary conditions have to be taken into account. In the case of mechanical methods like the hole-drilling and the ring-core method, the characteristics of the geometry of the component should be in accordance with an ideal and thick plate. The reason behind is the need for a calibration data set to transform strains into stresses. The calibration is usually carried out numerically. For the sake of simplicity, the geometry of the component is an ideal thick plate and the hole is introduced in its center. However, in most cases, this is not identical with the geometry of the component under investigation. Hence, an application tool was designed that enables the parametric design of a Finite Element Model, the determination of calibration coefficients, the evaluation of the experiment and the visualization of the results for geometries of practical importance. So far, the application tool can represent plates variable in their geometries and in positioning of the point of measurement. The option for other geometries are also possible e.g. a turbine blade.
Authors: Richard Wellman, John R. Nicholls
Authors: Hong Wei Guan, Yuan Li, Ying Dao Li, Shuo Li
Abstract: This paper introduces a modeling method of distributed control system, which is based on data. A subspace which can represent the key feature of the ensemble of data by extracting the eigenfunctions from the data will be founded. The Galerkin method will be applied to compute the coefficient of corresponding to the eigenfunctions and then the corresponding algorithm is also designed. The process of heat conduction in a metal bar is analysed with this kind of method. The results show the method well implementes modeling for distributed control system.
Authors: Philippe Maugis, M. Gouné, P. Barges, D. Dougnac, D. Ravaine, M. Lamberigts, Tadeusz Siwecki, Y. Bi
Authors: Ulrika Borggren, Göran Engberg, Tadeusz Siwecki
Abstract: Precipitation of carbonitrides has been studied in as-cast slabs of one Nb and one Nb and Ti containing HSLA steel. The precipitates have been quantified using LOM and TEM. The measured size and number distributions was then compared to model calculations of precipitate nucleation and growth using estimates of the cooling rates in the austenitic range (1490oC to 800oC) during casting. Both average size and number distributions could be modelled with good agreement using identical model parameters (except for individual diffusion coefficients for the participating species). The model is based on classic nucleation rate theory and a quasistationary approximation for growth of spherical particles. Local equilibrium is assumed at the phase boundary.
Authors: Qing Yan Xu, Rui Chen, Yu Feng Shi, Bai Cheng Liu
Abstract: In the present investigation, a physically based numerical model was developed to predict the yield stress of Al-7Si-Mg cast alloy during processing. It covered the integrated unit step models of the physical metallurgy of solidification, solid-state of homogenization, and structural hardening of precipitation. The as-cast microstructure of Al-7Si-Mg alloy was calculated based on the cellular automaton method and the evolution of the precipitated phase during aging process was achieved by a precipitation kinetic model involved nucleation, growth and coarsening. The yield stress prediction was achieved by a strengthening model including the effects of as-cast microstructure, solution strengthening and precipitate hardening. The predictions of this model were verified by comparing with experimental measured yield stress which shows that this model is successfully applied to predict the yield stress evolution of Al-7Si-Mg cast alloy.
Authors: Fernanda A. Sampaio da Silva, Marcos Flavio de Campos
Abstract: A model, based on hyperbolic tangent curve, was found to be able to reproduce several different types of magnetization curves of soft magnetic materials. The model is especially suitable for curves with sigmoid shape. The model is compared with experimental data for bonded soft iron powders, and also other ferromagnetic materials (1045 steel). Three adjusting parameters were used in the original hyperbolic tangent equation. Each parameter has different physical meaning.
Authors: Gilles Damamme, David Piot, Frank Montheillet, S. Lee Semiatin
Abstract: A simple mesoscale model was developed for discontinuous dynamic recrystallization. The material is described on a grain scale as a set of (variable) spherical grains. Each grain is characterized by two internal variables: its diameter and dislocation density (assumed homogeneous within the grain). Each grain is then considered in turn as an inclusion, embedded in a homogeneous equivalent matrix, the properties of which are obtained by averaging over all the grains. The model includes: (i) a grain boundary migration equation driving the evolution of grain size via the mobility of grain boundaries, which is coupled with (ii) a dislocation-density evolution equation, such as the Yoshie–Laasraoui–Jonas or Kocks–Mecking relationship, involving strain hardening and dynamic recovery, and (iii) an equation governing the total number of grains in the system due to the nucleation of new grains. The model can be used to predict transient and steady-state flow stresses, recrystallized fractions, and grain-size distributions. A method to fit the model coefficients is also described. The application of the model to pure Ni is presented.
Showing 31 to 40 of 2006 Paper Titles