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The Influence of External Heat Exposure on the Stress State of Shell Molds by Smelting Models

Mathematical Models and Computer Simulations 2022年第6期14卷 995-1001页

作者： Evstigneev, A.I. Dmitriev, E.A. Chernyshova, D.V. Odinokov, V.I. Evstigneeva, A.A. Ivankova, E.P. Komsomolsk-na-Amure State University Komsomolsk-on-Amur 681013 Russian Federation

Abstract: The problem of determining the force effect of the support filler on the resistance of the shell mold (SM) during the crystallization of liquid metal (steel) in it is formulated and solved. The tensile normal stress that occurs in the outer layers of the mold in the initial time moments when liquid metal is poured into it is taken as the leading physical quantity that affects the crack resistance of the SM. The force factor affecting the stress-strain state (SSS) of the SM is the friction between the SM and the supporting filler (SuFi), which appears during the elastic expansion of the outer layer in the SM as a result of the temperature exposure from the crystallizing liquid metal. The problem of mathematical programming (minmax function) is formulated to determine the coefficient of friction between the SM and SuFi to obtain the smallest value of the normal tensile stress in the SM over the area under consideration in the presence of a system of constraints. An axisymmetric body of rotation is considered, which has four regions: liquid metal, solid metal, SM, and SuFi, which is considered to be a solid body that creates friction at the contact point with the outer layer of the SM. To solve the problem, equations of the linear theory of elasticity, the equation of thermal conductivity and a proven numerical method are used, according to which the area under study is divided into elements by a system of orthogonal surfaces. For each element, the formulated system of equations is written in a difference form. An algorithm for solving the problem is developed and the results of the solution are presented, stress diagrams in the SuFi are constructed using the found value of the friction coefficient. The analysis of the received results is given. © 2022, Pleiades Publishing, Ltd.

关键词： casting by smelting models crack resistance displacement force action numerical method shell mold software solution algorithm stress stress state support filler

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Toward a Pseudo-Time Accurate Formulation of the Adjoint and Tangent Systems

Toward a Pseudo-Time Accurate Formulation of the Adjoint and...

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AIAA Science and Technology (SciTech) Forum and Exposition

作者： Padway, Emmett Mavriplis, Dimitri Univ Wyoming Dept Mech Engn Laramie WY 82071 USA

ISBN: (数字)9781624105784

ISBN: (纸本)9781624105784

This paper presents efforts to better compute sensitivities using adjoint and tangent systems for primal problems with partial or incomplete convergence. First we apply the unsteady adjoint to the steady equations to obtain a pseudo-time accurate formulation of the tangent and adjoint systems. This approach is demonstrated for the tangent and adjoint systems for three different solution algorithms: forward Euler and 5-stage Runge-Kutta pseudo-time evolution, and a quasi-Newton method. Proofs for the forward Euler and quasi-Newton method systems are shown. Those for the 5-stage Runge-Kutta scheme are found in the Appendix. Verification results for the derived schemes are shown followed by three test cases. The first test case compares results of the steady-state adjoint to the pseudo-time accurate formulation, showing magnitude differences and evaluating the angle between the two computed sensitivity vectors. The second case compares the steady-state method to the pseudo-time accurate formulation in a subsonic case for a non-converging primal problem. This case shows that while averaging the state decreases the angle between the two vectors, there are still significant magnitude differences between the vectors. The final test case is a transonic case with a non-converging primal and shows that the sensitivity vector computed from an averaged state still has a significant angle difference with the vector computed from the pseudo-time accurate result. Finally, an investigation into the effect of averaging the pseudo-time accurate adjoint computes sensitivities is presented.

关键词： Adaptive Mesh Refinement solution algorithm Computational Fluid Dynamics Multidisciplinary Design Optimization Finite Difference Method Triangular Element Drag Coefficient Stiffness Matrices Lift Coefficient Euler Equations

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SOLVING STOCHASTIC EQUILIBRIUM-MODELS WITH THE EXTENDED PATH METHOD

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ECONOMIC MODELLING 1990年第3期7卷 251-257页

作者： GAGNON, JE TAYLOR, JB COUNCIL ECON ADVISORS WASHINGTON DC 20500 USA

This paper demonstrates that the extended path algorithm of Fair and Taylor [2] can be used to solve the class of asset pricing models introduced by Lucas [5] The paper begins by describing the application of the extended path method to capital asset pricing. Next, the numerical solution is shown to converge to the true solution as the forecast horizon and the number of stochastic draws are increased. Finally, the method is used to solve a specific functional form of the model in order to test for accuracy and computational intensity.

关键词： Capital asset pricing Rational expectations solution algorithm

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Coupled Discrete Adjoints for Multiphysics in SU2

Coupled Discrete Adjoints for Multiphysics in SU2

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AIAA Aviation Forum

作者： Burghardt, Ole Gaugert, Nicolas R. Gomez, Pedro Palacios, Rafael Kattmann, Tobias Economon, Thomas D. TU Kaiserslautern Chair Sci Comp D-67663 Kaiserslautern Germany Imperial Coll London Dept Aeronaut London SW7 2AZ England Bosch Corp Res Fluid Dynam D-71272 Renningen Germany SU2 Fdn San Francisco CA 94158 USA

ISBN: (数字)9781624105982

ISBN: (纸本)9781624105982

Many optimization problems in fluid dynamics are naturally constituted in a larger multiphysics setting, the most prominent ones nowadays being fluid-structure interaction and conjugate heat transfer or combinations of them. In the context of partitioned solution approaches, and from a software perspective, this means that two or more solvers are coupled by exchanging data at common physical boundaries during the simulation. Optimization methods relying on discrete adjoint solutions have to consider such couplings in order to give accurate gradients. This article presents a methodology for how coupled multiphysics adjoints can be computed efficiently in a way that is also independent of the choice or configuration of the underlying physical problem. Based on an implementation in SU2 (an open-source multiphysics simulation and design software(1)) we demonstrate how the same algorithm can be applied for shape sensitivity analysis on a conjugate heat transfer as well as a fluid-structure interaction test case.

关键词： Fluid Structure Interaction Conjugate Heat Transfer Pressure Coefficient Sensitivity Analysis Poisson's Ratio solution algorithm Aerodynamic Shape Optimization Incompressible Flow Material Properties Stiffness Matrices

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Optimal Design of eVTOLs for Urban Mobility using Analytical Target Cascading (ATC)

Optimal Design of eVTOLs for Urban Mobility using Analytical...

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AIAA SciTech Forum

作者： Chinthoju, Prajwal K. Lee, Yong Hoon Das, Ghanendra K. James, Kai A. Allison, James T. Univ Illinois Ind & Enterprise Syst Engn 104 S Mathews Ave406 TB Urbana IL 61801 USA Univ Memphis Dept Mech Engn 3815 Cent Ave322D ES Memphis TN 38152 USA Georgia Inst Technol Sch Aerosp Engn 275 Ferst Dr NW212 Weber Atlanta GA 30332 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

Over the past few decades, multidisciplinary design optimization (MDO) techniques have shown great potential in generating optimal designs for complex system of systems. Monolithic MDO methods that formulate the design problem as a single optimization problem are effective, but present challenges in coordination. On the other hand, distributed MDO methods decompose the design problem into different optimization problems and hence offer more modularity and flexibility, especially when implemented by teams of optimization specialists. In this article, one such distributed MDO method, Analytical Target Cascading (ATC), is investigated as a candidate for the design of electric Vertical Take Off and Landing aircraft (eVTOL). Design of eVTOLs for urban mobility has been a subject of immense interest over the past decade. eVTOLs offer many advantages over conventional modes of urban transport such as reduced environmental impact, utilization of vertical space for transportation, and competitive cost of transportation. Most current efforts for eVTOL design are in relatively early stages. Hence, distributed MDO methods that can effectively consider complex interactions between different subsystems and disciplines can help support eVTOL design efforts. In this study, ATC is implemented to optimize the total cost per flight for a simple mission, involving take-off to a set altitude, cruising at constant velocity for a range of 50-150 km, and landing, all while carrying a given payload. The key design parameters that are optimized as a part of this study are the mass of aircraft and individual subsystems, cruise velocity, wingspan, and radius of the propeller. Furthermore, a comparison of the resulting optimal solutions using ATC and monolithic MDO methods is presented. General observations are also articulated regarding potential computational advantages, such as parallelism and tailored solution algorithms, as well as organizational considerations, such as distributed iterati

关键词： Multidisciplinary Design and Optimization Electric Vertical Take off and Landing Propeller Blades solution algorithm Maximum Takeoff Weight Lift Coefficient Electric Motors Helicopters Drag Coefficient Blade Element Momentum Theory

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Experimental and Numerical Study of Methane-Oxygen Combustion Inside a Low Pressure Rocket Motor

Experimental and Numerical Study of Methane-Oxygen Combustio...

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AIAA Propulsion and Energy Forum / IEEE Electric Aircraft Technologies Symposium (EATS)

作者： Kaya, Mine Akyuzlu, Kazim M. Univ New Orleans Dept Mech Engn New Orleans LA 70148 USA Texas A&M Univ College Stn TX 77843 USA

ISBN: (数字)9781624106118

ISBN: (纸本)9781624106118

An experimental and numerical study was conducted to gain insight to the thermal-fluid characteristics of methane fueled combustion inside a laboratory scale, low pressure, rocket motor. The combustion chamber of the motor has a square cross section and is equipped with quartz side windows to enable visual observation of the flame. The thermocouples placed along the axial direction of the motor provides measurement of temperature inside the flame. Hot tests were conducted for various methane-oxygen ratios and at different chamber pressures. A numerical study was also conducted using a commercial CFD code to predict the temperature and velocity distribution inside combustion chamber. The CFD predicted temperatures at the thermocouple locations fair well with the experimentally measured values.

关键词： Hybrid Rocket Engines Combustion Chambers Thermocouples CFD Codes Combustion Products Mass Flow Rate Numerical Simulation solution algorithm Data Acquisition System Pressure Transducers

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Dynamic States Specific Analysis for Belt Conveyor Based on FDM

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International Conference on Mechatronics and Control Engineering (ICMCE 2012)

作者： Shen, Xiao Wang, Qun Fu, Zhouyu Bai, Shuowei Sun, Zhaoyang Shandong Univ Sci & Technol Coll Mech & Elect Engn Qingdao 266590 Peoples R China Datong Coal Min Grp Yangzhou 272100 Jiangsu Peoples R China Shandong Univ Coll Mech eNGN Jinan 250061 Peoples R China

ISBN: (纸本)9783037855959

There are two common research methods on the dynamic states model of belt conveyor in China at present. The mathematical model is built by finite element method then it is solved by numerical method. And the continuous model is built when the belt is treated as elastic body then it is solved by mathematical method. This paper puts forward the establishment of continuous model, the model is solved by FDM and the simulation results are given.

关键词： Belt conveyor Dynamic states specific FDM solution algorithm

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An Exact Method for Solving Selective Maintenance Problems Considering Imperfect Maintenance 8

An Exact Method for Solving Selective Maintenance Problems C...

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8th International Conference on Intelligent Networking and Collaborative Systems (INCoS)

作者： Cao, Wenbin Song, Wenyuan Hu, Qiwei Du, Yinxia Mech Engn Coll Dept Engn Management Shijiazhuang Peoples R China Heibei Polytech Inst Shijiazhuang Peoples R China

ISBN: (纸本)9781509041237

In the past few decades, analytical models for maintenance optimization have been extensively investigated. As research continues, the cases considered during the mathematical modeling are much more practical, as well as complex, which brings many difficulties for solution. In this paper, we present an exact method for solving the selective maintenance model considering multiple maintenance actions. The solution procedure is discussed in detail. Moreover, an example is adopted to verify its efficiency. Compared with total enumeration method, the proposed method can significantly reduce the solution space (about 42.46%). What's more, unlike some intelligent algorithm, this method can always give out an optimal solution. Finally, the effects of available resources on solution space are discussed.

关键词： selective miantnance solution algorithm exact method imperfect maintenance

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Interpretation of Experimental Tensile Test Results and Its Implication on Damage Modeling

Interpretation of Experimental Tensile Test Results and Its ...

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AIAA Science and Technology (SciTech) Forum and Exposition

作者： Arnold, Steven M. Lerch, Bradley A. Ricks, Trenton M. NASA Glenn Res Ctr Multiscale Modeling Mat & Struct Div Cleveland OH 44135 USA NASA Glenn Res Ctr Mat & Struct Div Cleveland OH 44135 USA

ISBN: (数字)9781624105784

ISBN: (纸本)9781624105784

To improve prognostics for predicting component life, coupon tests were conducted on Ti-6Al-4V to investigate the development of damage. Various test types were employed (tension, creep, stress relaxation and fatigue) under a wide range of temperatures and loading rates to engage various amounts of time-dependent and damage behavior. Both stiffness degradation and Poisson's ratio were monitored to see if they were useful in indicating the initiation and accumulation of damage and subsequently the onset of failure. Stiffness exhibited large decreases with increasing strain when calculated using engineering stress and strain. However, minimal stiffness change was observed when using the true stress and strain values. Poisson's ratio was monitored on every test and showed promise as a damage indicator. However, calculation of Poisson's ratio was found to be more involved than expected;due to anisotropy and the presence of strain gradients along the specimen at large applied strains. First, the material had a moderate texture and resulted in anisotropy of the strains. Second, the evolution of instantaneous Poisson's ratio as a function of axial strain showed strange and unexpected behaviors, which necessitated a more extensive analysis of its development. This led to a discussion on the use of small versus large strain approaches and the importance of making consistent measurements, i.e. axial and transverse strain measurements over the same volume of material. Additionally, finite element analysis of a tensile sample indicated that non-uniform strain occurred in the sample prior to attaining the maximum strength. This coupled with the location at which transverse strain was measured had a significant influence on the resulting values of instantaneous Poisson's ratio.

关键词： Tensile Tests Ultimate Tensile Strength Temperature Stresses Finite Element Analysis Ti 6Al 4V Extensometer Viscoplasticity Compressibility Effect Catastrophic Failure solution algorithm

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Multi-Agent Passive Safe Optimal Control using Integration Constants as State Variables

Multi-Agent Passive Safe Optimal Control using Integration C...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Guffanti, Tommaso D'Amico, Simone Stanford Univ Aeronaut & Astronaut 496 Lomita Mall Stanford CA 94305 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

This paper presents a new algorithm that provides optimal control profiles that drive a multi-agent system to a desired state at a desired time, with the guarantee of no collision, for a specified time horizon, even in case of control input application failure. The algorithm is applicable to multi-agent systems governed by nonlinear control-affine dynamics. First, the paper defines the problem of passive safe optimal control, which adds an important layer of safety to the traditional collision avoidance between agents. A multi-agent system is defined passive safe if the agents maintain safe separation even in the case any agent loses control at any time on the trajectory towards the final condition. Second, the paper shows that using the integration constants of an integrable portion of the multi-agent system dynamics as state variables is the key for including efficiently passive safety into an algorithmic framework. In particular, the number of constraints to be enforced reduces from cubic to quadratic in the number of time samples. Finally, using the integration constants, a solution algorithm based on convex programming is formalized and tested on the challenging problem of passive safe optimal control of multi-spacecraft systems in closed orbits of arbitrary eccentricity.

关键词： Trajectory Optimization Multi Agent System solution algorithm Nonlinear Control Spacecraft System Highly Eccentric Orbit Orbital Period Model Predictive Control Saturn Numerical Integration

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