Numerical Analysis of Multiphase Flow in a Steel Oxygen Converter With Top and Bottom Blowing

Combined blowing in the steelmaking basic oxygen converter is a technique that allows more agitation in the metal bath, and gives a fast decarburization rate, accelerated removal of impurities and chemical and thermal homogenization. In this work the multiphase flow in an industrial-like basic oxygen converter with top and bottom blowing is analyzed by means of Computational Fluid Dynamics software. Turbulence in the converter is simulated by means of the classical K-ε model given that this model yields more numerical stability during the integration for long times. Top jet velocities of Mach 1 and Mach 2, and 50 and 100 m s−1 of bottom injection velocities are used, and the results are compared with the conventional top blowing injection. Numerical results show that the combined blowing generates more agitation of the metal bath than that of the top blowing, however, from an operating viewpoint, combined blowing promotes that a significant volume of molten metal be expelled from the converter mouth.

Mobile Agent-Based Computational Steering for Distributed Simulation

Two challenging problems in the area of scientific computation are long computation time and large-scale, distributed, and diverse data sets. As the scale of science and engineering applications rapidly expands, these two problems become more manifest than ever. This paper presents the concept of Mobile Agent-based Computational Steering (MACS) for distributed simulation. The MACS allows users to apply new or modified algorithms to a running application by altering certain sections of the program code without the need of stopping the execution and recompiling the program code. The concept has been validated through an application for dynamic CFD data post processing. The validation results show that the MACS has a great potential to enhance productivity and data manageability of large-scale distributed computational systems.

Multiple Time-Scale Molecular Simulations: Modeling Realistic Loading Rates

The vast gap between the molecular dynamics (MD) and experimental time scales poses serious problems to direct comparison between the MD simulation and experimental results. The inability of the traditional MD simulation methods to model long enough time scales also results in modeling unrealistically high loading rates and strain rates that are usually at least six or seven orders of magnitude higher than the corresponding experimental values. This may have a tremendous effect on the realism and quality of the simulation results.

Free Vibration Analysis of Double Curvature Thin Walled Structures by a B-Spline Finite Element Approach

This paper presents a free vibration analysis of general double curvature shell structures using B-spline shape functions and a refinement technique. The shell formulation is developed following the well known Ahmad degenerate approach including the effect of the shear deformation. The formulation is not isoparametric, as a consequence the assumed displacement field is described through non-uniform B-spline functions of any degree. A solution refinement technique is considered by means of a high continuity p-method approach. The eigensolution of a plate, and of single and double curvature shells are obtained by numerical simulation to test the performance of the approach. Solutions are compared with other available analytical and numerical solutions, and discussion follows.

A Variational Asymptotic Model for Predicting Initial Yielding Surface and Elastoplastic Behavior of Metal Matrix Composite Materials

The focus of this paper is to develop a micromechanics model based on the variational asymptotic method for unit cell homogenization (VAMUCH) for predicting of the initial yielding surface, overall instantaneous moduli, and elastoplastic behavior of metal matrix composites. Considering the size of the microstructure as a small parameter, we can formulate a variational statement of the unit cell through an asymptotic expansion of the energy functional. To handle realistic microstructures, we implement this new model using the finite element method. For model validation, we used a few examples to demonstrate the application and accuracy of this theory and the companion code.

Exact Solution of Time History Response for Dynamic Systems With Arbitrary Viscous Damping Using Complex Modal Analysis

A solution method for general, non-proportional damping time history response for piecewise linear loading is generalized to exact solutions which include piecewise quadratic loading. Comparisons are made to Trapezoidal and Simpson’s quadrature rules for approximating the time integral of the weighted generalized forcing function in the exact solution to the decoupled modal equations arising from state-space modal analysis of linear dynamic systems. Closed-form expressions for the weighting parameters in the quadrature formulas in terms of time-step size and complex eigenvalues are derived. The solution is obtained step-by-step from update formulas derived from the piecewise linear and quadratic interpolatory quadrature rules starting from the initial condition. An examination of error estimates for the different force interpolation methods shows convergence rates depend explicitly on the amount of damping in the system as measured by the real-part of the complex eigenvalues of the state-space modal equations and time-step size. Numerical results for a system with general, non-proportional damping, and driven by a continuous loading shows that for systems with light damping, update formulas for standard Trapezoidal and Simpson’s rule integration have comparable accuracy to the weighted piecewise linear and quadratic force interpolation update formulas, while for heavy damping, the update formulas from the weighted force interpolation quadrature rules are more accurate. Using a simple model representing a stiff system with general damping, we show that a two-step modal analysis using real-valued modal reduction followed by state-space modal analysis is shown to be an effective approach for rejecting spurious modes in the spatial discretization of a continuous system.

Physical-Based Simulations of Mechanical Watches and Clocks

Mechanical watches and clocks are intricate mechanical devices that fascinate millions of people around the world. In general, a mechanical watch is made of some 100 components. Among these components, the escapement plays a vital role in controlling the timekeeping accuracy. An escapement usually consists of an escape wheel, which receives energy provided by the mainspring through the gear train, and a pallet fork, which controls the oscillation. Owing to its complex nature, few have built a mathematical model for the escapement. In this paper, we present a physical-based simulation model for the Graham Escapement (the oldest and the most common escapement for clocks), and a model for the Swiss Lever Escapement (the most popular escapement for mechanical watches). The models are developed based on a commercial software system RecurDyn® [1]. The simulation helps to understand the kinetics as well as the dynamics of the escapements.

A Study on Bearing Creep Mechanism With FEM Simulation

Because of the continuous quests for high performance and compact structure of automobile and machine in recent years, rolling bearings are required to work under harder conditions of high speed and heavy load than before. The applications of hard condition may lead to a greater likelihood of happening of bearing malfunctions such as flaking, wear, creep, fracture etc. In this paper, the phenomenon called outer ring creep occurring in bearings subject to non-rotating load is discussed. Outer ring creep is referred to that bearing outer ring rotates relatively to the housing in certain applications. Outer ring creep may result in such problems as unusual noise and vibration and may cause wear of housing and outer ring. If abrasive particles caused by wear of the ring and housing enter the raceway, the bearing may be damaged and destroyed. Conventionally, the problem of outer ring creep was considered to be a result of rotating bearing load. However, even if the direction of radial load remained relatively unchanged, outer ring creep is observed in many cases. The generation mechanism of this kind of outer ring creep has not yet been made clear till now. With FEM simulation and test verification, we analyzed the phenomenon of outer ring creep under non-rotating load. We concluded that outer ring creep under non-rotating load is a result of localized strain and rippling deformation caused by rolling elements. In this paper, only outer ring creep is discussed below, but the similar result can be obtained for inner ring creep.

Regime Switching Issues and Criteria for Coupled Static-Dynamic Atomistic Methods

Coupled static-dynamic atomistic method may be used for coarse graining time in temporal multi-scale atomistic modeling of nano-mechanical problems. This approach can be especially effective for mechanical processes that consist of two distinct phases: the slow phase when the system resides in one local energy minimum and the fast phase associated with a rapid transition from one meta-stable state to another. In this case, the slow phase can be effectively modeled using static energy minimization technique, while the fast phase corresponding to the state transition event may be modeled dynamically. In this case, dynamic modeling is necessary to capture the dynamic effects, such as thermal and inertial, that can not be accounted for in static modeling. One of the major issues of this type of method is to determine when the transitions between the two regimes have to be done. In this presentation, issues of switching between the static and dynamic regimes are outlined and criteria that can be used for effective switching between the two regimes are proposed. In particular, a dynamic-to-static switch based on the kinetic energy and static-to-dynamic switch based on the potential energy are discussed.

Correlation of an Acoustic Finite Element Model of the Automobile Passenger Compartment Using Loudspeaker Excitation

An acoustic finite-element model of the automobile passenger compartment is developed and experimentally assessed for predicting the sound pressure response in the compartment. The acoustic finite-element model represents both the passenger compartment cavity and the trunk compartment cavity, with the coupling between them through the rear seats for which the acoustic properties are determined from a modified “heavy air” approximation. Measurements of the sound pressure response in the passenger compartment are obtained using a specially developed loudspeaker excitation device for assessing the accuracy of the model. Comparisons are made of the predicted versus measured sound pressure response to 300 Hz for loudspeaker excitation in both the passenger and trunk compartments.