The Experts below are selected from a list of 30948 Experts worldwide ranked by ideXlab platform
Yuqiang Jiang - One of the best experts on this subject based on the ideXlab platform.
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effects of two stage creep aging on precipitates of an al cu mg alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Guan Liu, Y C Lin, Xiancheng Zhang, Yuqiang JiangAbstract:Abstract Creep-aging forming, combining the aging treatment and forming process, is an ideal method to manufacture the Complex Aircraft panels. Two-stage creep-aging behaviors of an Al–Cu–Mg alloy are studied by uniaxial tensile creep tests over wide ranges of temperature and external stress. Effects of creep-aging temperature and external stress on precipitates are discussed. The results show that the formation of substantial nuclei occurs in the first creep-aging stage. With the increases of creep-aging temperature and external stress in the second creep-aging stage, the precipitates easily grow up, while the density of precipitates first increases and then decreases. Meanwhile, the width of precipitate free zone and the size of grain boundary precipitate increase. Compared with the stress-free aging process, the two-stage creep-aging process broadens the width of precipitate free zone, and result in the discontinuously-distributed aging precipitates along grain boundaries, which can improve the corrosion resistance of the studied Al–Cu–Mg alloy.
Minghui Huang - One of the best experts on this subject based on the ideXlab platform.
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experimental research on creep aging behavior of al cu mg alloy with tensile and compressive stresses
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Lihua Zhan, Minghui HuangAbstract:Abstract Complex Aircraft panels are generally manufactured by creep age forming process (CAF). In CAF, an aluminum panel is mainly subjected to bending, in which one side of the component is in tension and the other side is in compression. The tension and compression creep aging behaviors of Al-Cu-Mg alloy are investigated through creep tests, hardness tests and transmission electron microscope observations. It is found that the creep strains under compressive stresses are smaller than those under tensile stresses. When comparing to the microstructure of creep-aged alloy, the compressive stress can promote the formation of S phase in aluminum matrix and inhibit the generation of grain boundary precipitates, which leads to the improvement of hardness of the compression creep aged alloy. A unified creep constitutive model to describe the creep aging behavior of 2524 aluminum alloy with different stress roles was established based on the Hyperbolic Sine method, and a good agreement between the experimental results and model predictions is obtained.
Antony Jameson - One of the best experts on this subject based on the ideXlab platform.
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Aerodynamic shape optimization of supersonic Aircraft configurations via an adjoint formulation on distributed memory parallel computers
Computers and Fluids, 1999Co-Authors: Josephine Reuther, J. J. Alonso, Mark J. Rimlinger, Antony JamesonAbstract:This work describes the application of a control theory-based aerodynamic shape optimization method to the problem of supersonic Aircraft design. A high fidelity computational fluid dynamics (CFD) algorithm modelling the Euler equations is used to calculate the aerodynamic properties of Complex three-dimensional Aircraft configurations. The design process is greatly accelerated through the use of both control theory and parallel computing. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods. The resulting problem is then implemented in parallel using a domain decomposition approach, an optimized communication schedule, and the Message Passing Interface (MPI) Standard for portability and efficiency. In our earlier studies, the serial implementation of this design method, was shown to be effective for the optimization of airfoils, wings, wing-bodies, and Complex Aircraft configurations using both the potential equation and the Euler equations. In this work, our concern will be to extend the methodologies such that the combined capabilities of these new technologies can be used routinely and efficiently in an industrial design environment. The aerodynamic optimization of a supersonic transport configuration is presented as a demonstration test case of the capability. A particular difficulty of this test case is posed by the close coupling of the propulsion/airframe integration.
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constrained multipoint aerodynamic shape optimization using an adjoint formulation and parallel computers
Journal of Aircraft, 1999Co-Authors: James Reuther, J. J. Alonso, Mark J. Rimlinger, Antony Jameson, David SaundersAbstract:An aerodynamic shape optimization method that treats the design of Complex Aircraft configurations subject to high fidelity computational fluid dynamics (CFD), geometric constraints and multiple design points is described. The design process will be greatly accelerated through the use of both control theory and distributed memory computer architectures. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods. The resulting problem is implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on a higher order CFD method. In order to facilitate the integration of these high fidelity CFD approaches into future multi-disciplinary optimization (NW) applications, new methods must be developed which are capable of simultaneously addressing Complex geometries, multiple objective functions, and geometric design constraints. In our earlier studies, we coupled the adjoint based design formulations with unconstrained optimization algorithms and showed that the approach was effective for the aerodynamic design of airfoils, wings, wing-bodies, and Complex Aircraft configurations. In many of the results presented in these earlier works, geometric constraints were satisfied either by a projection into feasible space or by posing the design space parameterization such that it automatically satisfied constraints. Furthermore, with the exception of reference 9 where the second author initially explored the use of multipoint design in conjunction with adjoint formulations, our earlier works have focused on single point design efforts. Here we demonstrate that the same methodology may be extended to treat complete configuration designs subject to multiple design points and geometric constraints. Examples are presented for both transonic and supersonic configurations ranging from wing alone designs to Complex configuration designs involving wing, fuselage, nacelles and pylons.
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aerodynamic shape optimization of supersonic Aircraft configurations via an adjoint formulation on parallel computers
Symposium on Multidisciplinary Analysis and Optimization, 1996Co-Authors: James Reuther, J. J. Alonso, Mark J. Rimlinger, Antony JamesonAbstract:This work describes the application of a control theory-based aerodynamic shape optimization method to the problem of supersonic Aircraft design. The design process is greatly accelerated through the use of both control theory and a parallel implementation on distributed memory computers. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods. The resulting problem is then implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) Standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on higher order computational fluid dynamics methods (CFD). In our earlier studies, the serial implementation of this design method was shown to be effective for the optimization of airfoils, wings, wing-bodies, and Complex Aircraft configurations using both the potential equation and the Euler equations. In our most recent paper, the Euler method was extended to treat complete Aircraft configurations via a new multiblock implementation. Furthermore, during the same conference, we also presented preliminary results demonstrating that this basic methodology could be ported to distributed memory parallel computing architectures. In this paper, our concern will be to demonstrate that the combined power of these new technologies can be used routinely in an industrial design environment by applying it to the case study of the design of typical supersonic transport configurations. A particular difficulty of this test case is posed by the propulsion/airframe integration.
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aerodynamic shape optimization of Complex Aircraft configurations via an adjoint formulation
34th Aerospace Sciences Meeting and Exhibit, 1996Co-Authors: James Reuther, Antony Jameson, J Farmer, Luigi Martinelli, David SaundersAbstract:This work describes the implementation of optimization techniques based on control theory for Complex Aircraft configurations. Here control theory is employed to derive the adjoint differential equations, the solution of which allows for a drastic reduction in computational costs over previous design methods (13, 12, 43, 38). In our earlier studies (19, 20, 22, 23, 39, 25, 40, 41, 42) it was shown that this method could be used to devise effective optimization procedures for airfoils, wings and wing-bodies subject to either analytic or arbitrary meshes. Design formulations for both potential flows and flows governed by the Euler equations have been demonstrated, showing that such methods can be devised for various governing equations (39, 25). In our most recent works (40, 42) the method was extended to treat wing-body configurations with a large number of mesh points, verifying that significant computational savings can be gained for practical design problems. In this paper the method is extended for the Euler equations to treat complete Aircraft configurations via a new multiblock implementation. New elements include a multiblock-multigrid flow solver, a multiblock-multigrid adjoint solver, and a multiblock mesh perturbation scheme. Two design examples are presented in which the new method is used for the wing redesign of a transonic business jet.
Guan Liu - One of the best experts on this subject based on the ideXlab platform.
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effects of two stage creep aging on precipitates of an al cu mg alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Guan Liu, Y C Lin, Xiancheng Zhang, Yuqiang JiangAbstract:Abstract Creep-aging forming, combining the aging treatment and forming process, is an ideal method to manufacture the Complex Aircraft panels. Two-stage creep-aging behaviors of an Al–Cu–Mg alloy are studied by uniaxial tensile creep tests over wide ranges of temperature and external stress. Effects of creep-aging temperature and external stress on precipitates are discussed. The results show that the formation of substantial nuclei occurs in the first creep-aging stage. With the increases of creep-aging temperature and external stress in the second creep-aging stage, the precipitates easily grow up, while the density of precipitates first increases and then decreases. Meanwhile, the width of precipitate free zone and the size of grain boundary precipitate increase. Compared with the stress-free aging process, the two-stage creep-aging process broadens the width of precipitate free zone, and result in the discontinuously-distributed aging precipitates along grain boundaries, which can improve the corrosion resistance of the studied Al–Cu–Mg alloy.
Lihua Zhan - One of the best experts on this subject based on the ideXlab platform.
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experimental research on creep aging behavior of al cu mg alloy with tensile and compressive stresses
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Lihua Zhan, Minghui HuangAbstract:Abstract Complex Aircraft panels are generally manufactured by creep age forming process (CAF). In CAF, an aluminum panel is mainly subjected to bending, in which one side of the component is in tension and the other side is in compression. The tension and compression creep aging behaviors of Al-Cu-Mg alloy are investigated through creep tests, hardness tests and transmission electron microscope observations. It is found that the creep strains under compressive stresses are smaller than those under tensile stresses. When comparing to the microstructure of creep-aged alloy, the compressive stress can promote the formation of S phase in aluminum matrix and inhibit the generation of grain boundary precipitates, which leads to the improvement of hardness of the compression creep aged alloy. A unified creep constitutive model to describe the creep aging behavior of 2524 aluminum alloy with different stress roles was established based on the Hyperbolic Sine method, and a good agreement between the experimental results and model predictions is obtained.