摘要 :
In a modern world, importance of computer modeling for solving complex engineering problems cannot be overstated. However, in a number of critical engineering problems computational models cannot provide unique answer and so furth...
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In a modern world, importance of computer modeling for solving complex engineering problems cannot be overstated. However, in a number of critical engineering problems computational models cannot provide unique answer and so further physical and analytical insight is required to guide computer simulations. Such an insight becomes even more valuable when off-nominal regimes of operation have to be considered. To deal with complexity of the physical process at the interface of multiple engineering systems a new discipline is emerging - operational physics of critical missions. This discipline combines an old-good physics based approach to modeling engineering problems with modern advanced technologies for analyzing continuous and discrete information flow involving multiple modes of operation in uncertain environments, unknown state variables, heterogeneous software and hardware components. In this paper the new approach is illustrated using as an example analysis of the critical physics phenomena that lead to Challenger accident including physics of cryogenic explosion and propagation of detonation waves, internal ballistics of SRM's in the presence of the case breach fault, and monitoring of the structural integrity of the spacecraft.
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摘要 :
In a modern world, importance of computer modeling for solving complex engineering problems cannot be overstated. However, in a number of critical engineering problems computational models cannot provide unique answer and so furth...
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In a modern world, importance of computer modeling for solving complex engineering problems cannot be overstated. However, in a number of critical engineering problems computational models cannot provide unique answer and so further physical and analytical insight is required to guide computer simulations. Such an insight becomes even more valuable when off-nominal regimes of operation have to be considered. To deal with complexity of the physical process at the interface of multiple engineering systems a new discipline is emerging - operational physics of critical missions. This discipline combines an old-good physics based approach to modeling engineering problems with modern advanced technologies for analyzing continuous and discrete information flow involving multiple modes of operation in uncertain environments, unknown state variables, heterogeneous software and hardware components. In this paper the new approach is illustrated using as an example analysis of the critical physics phenomena that lead to Challenger accident including physics of cryogenic explosion and propagation of detonation waves, internal ballistics of SRM's in the presence of the case breach fault, and monitoring of the structural integrity of the spacecraft.
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The In-Space Manufacturing (ISM) project at NASA Marshall Space Flight Center, in a partnership with the company, Made in Space, has previously investigated 3D printing of polymer materials on-orbit. In recent years, the project h...
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The In-Space Manufacturing (ISM) project at NASA Marshall Space Flight Center, in a partnership with the company, Made in Space, has previously investigated 3D printing of polymer materials on-orbit. In recent years, the project has begun exploring the potential for metal additive manufacturing (AM) on future space missions to reduce logistics and enable point-of-use manufacturing for sparing and repair. This paper provides an overview of constraints for demonstrating a manufacturing process on the International Space Station (ISS) as well as information on previous trades of available metal AM processes and their potential for in-space use. There are currently two processes in development as payloads for an ISS technology demonstration: wire+arc additive manufacturing (the Vulcan payload from Made in Space, Inc.) and bound metal additive manufacturing (the Fabrication Laboratory from Techshot, Inc). An update on both of these systems, key results to date, and future development efforts will be presented. Relevant modeling work, performed by NASA Ames Research Center, to evaluate operation of certain aspects of the bound metal AM process in a microgravity environment will also be summarized.
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摘要 :
The In-Space Manufacturing (ISM) project at NASA Marshall Space Flight Center, in a partnership with the company, Made in Space, has previously investigated 3D printing of polymer materials on-orbit. In recent years, the project h...
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The In-Space Manufacturing (ISM) project at NASA Marshall Space Flight Center, in a partnership with the company, Made in Space, has previously investigated 3D printing of polymer materials on-orbit. In recent years, the project has begun exploring the potential for metal additive manufacturing (AM) on future space missions to reduce logistics and enable point-of-use manufacturing for sparing and repair. This paper provides an overview of constraints for demonstrating a manufacturing process on the International Space Station (ISS) as well as information on previous trades of available metal AM processes and their potential for in-space use. There are currently two processes in development as payloads for an ISS technology demonstration: wire+arc additive manufacturing (the Vulcan payload from Made in Space. Inc.) and bound metal additive manufacturing (the Fabrication Laboratory from Techshot, Inc). An update on both of these systems, key results to date, and future development efforts will be presented. Relevant modeling work, performed by NASA Ames Research Center, to evaluate operation of certain aspects of the bound metal AM process in a microgravity environment will also be summarized.
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A moving-boundary model of two-phase (TP) flow in a cross-country cryogenic fuel supply line has been developed. It is based on time-dependent one-dimensional ordinary differential equations that describe mass and energy conservat...
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A moving-boundary model of two-phase (TP) flow in a cross-country cryogenic fuel supply line has been developed. It is based on time-dependent one-dimensional ordinary differential equations that describe mass and energy conservation of the flowing cryogen that exchanges heat with the tubes' walls. The momentum conservation is taken into consideration by relating the pressure drop across the boundaries of the control volumes (CVs) with the corresponding inlet and outlet mass flow rates through the boundaries of these volumes. With a relatively small computational effort compare to full-scale schemes, the model describes pressure and temperature variations together with kinetics of vapor void fraction and of the interphase boundary motion in the different parts of the spatially distributed system. In this part, special attention is given to detailed study of the transient and steady state two-phase cryogenic movement in a long horizontal pipe with different regimes of flow: with and without heat exchange between the tube walls and the cryogen and between the walls and the environment; in the presence of local mass and heat leaks, and of sudden obstructions, etc. The convergence of the computational procedure with respect to the number of the CVs is discussed.
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摘要 :
A moving-boundary model of two-phase (TP) flow in a cross-country cryogenic fuel supply line has been developed. It is based on time-dependent one-dimensional ordinary differential equations that describe mass and energy conservat...
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A moving-boundary model of two-phase (TP) flow in a cross-country cryogenic fuel supply line has been developed. It is based on time-dependent one-dimensional ordinary differential equations that describe mass and energy conservation of the flowing cryogen that exchanges heat with the tubes' walls. The momentum conservation is taken into consideration by relating the pressure drop across the boundaries of the control volumes (CVs) with the corresponding inlet and outlet mass flow rates through the boundaries of these volumes. With a relatively small computational effort compare to full-scale schemes, the model describes pressure and temperature variations together with kinetics of vapor void fraction and of the interphase boundary motion in the different parts of the spatially distributed system. In this part, special attention is given to detailed study of the transient and steady state two-phase cryogenic movement in a long horizontal pipe with different regimes of flow: with and without heat exchange between the tube walls and the cryogen and between the walls and the environment; in the presence of local mass and heat leaks, and of sudden obstructions, etc. The convergence of the computational procedure with respect to the number of the CVs is discussed.
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摘要 :
A moving-boundary model of two-phase (TP) flow in a cross-country cryogenic fuel supply line has been developed. It is based on time-dependent one-dimensional ordinary differential equations that describe mass and energy conservat...
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A moving-boundary model of two-phase (TP) flow in a cross-country cryogenic fuel supply line has been developed. It is based on time-dependent one-dimensional ordinary differential equations that describe mass and energy conservation of the flowing cryogen that exchanges heat with the tubes' walls. The momentum conservation is taken into consideration by relating the pressure drop across the boundaries of the control volumes (CVs) with the corresponding inlet and outlet mass flow rates through the boundaries of these volumes. With a relatively small computational effort compare to full-scale schemes, the model describes pressure and temperature variations together with kinetics of vapor void fraction and of the interphase boundary motion in the different parts of the spatially distributed system. In this part, special attention is given to detailed study of the transient and steady state two-phase cryogenic movement in a long horizontal pipe with different regimes of flow: with and without heat exchange between the tube walls and the cryogen and between the walls and the environment; in the presence of local mass and heat leaks, and of sudden obstructions, etc. The convergence of the computational procedure with respect to the number of the CVs is discussed.
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This presentation deals with the mathematical modeling of composite microstructures for uncertainty quantification of composite structural parameters. Multiple designs of unidirectional fiber reinforced composite materials with ar...
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This presentation deals with the mathematical modeling of composite microstructures for uncertainty quantification of composite structural parameters. Multiple designs of unidirectional fiber reinforced composite materials with arbitrary ply orientations are investigated. We consider a homogenization approach from microscopic to macroscopic scales for the prediction of mechanical properties of the composites. An uncertainty assessment of the effective structural modulus of composite materials consisting of an elastic matrix reinforced with fibers as functions of the phase volume fractions and the structural properties of the constituents is conducted. We consider the global sensitivity analysis (GSA) methods based both on the Fourier Amplitude Sensitivity Test (FAST) and on the Sobol global sensitivity index (GSI). The proposed approach makes it possible to quantify the effective structural parameters of the material based on the variance in the constituents. Numerical results of the GSI and FAST computed for composite materials reveal significant dependence of the macroscopic composite on the probabilistic properties of the fiber volume fraction. The GSA is performed to quantify the influence of fiber volume fraction variation, lamina thickness variation, etc. A nonlinear stage for composite failure prediction based on the Tsai-Wu failure theory was considered. The GSI quantify the relative contribution of variances in material constituents to the total variance of the material under a critical load.
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This presentation deals with the mathematical modeling of composite microstructures for uncertainty quantification of composite structural parameters. Multiple designs of unidirectional fiber reinforced composite materials with ar...
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This presentation deals with the mathematical modeling of composite microstructures for uncertainty quantification of composite structural parameters. Multiple designs of unidirectional fiber reinforced composite materials with arbitrary ply orientations are investigated. We consider a homogenization approach from microscopic to macroscopic scales for the prediction of mechanical properties of the composites. An uncertainty assessment of the effective structural modulus of composite materials consisting of an elastic matrix reinforced with fibers as functions of the phase volume fractions and the structural properties of the constituents is conducted. We consider the global sensitivity analysis (GSA) methods based both on the Fourier Amplitude Sensitivity Test (FAST) and on the Sobol global sensitivity index (GSI). The proposed approach makes it possible to quantify the effective structural parameters of the material based on the variance in the constituents. Numerical results of the GSI and FAST computed for composite materials reveal significant dependence of the macroscopic composite on the probabilistic properties of the fiber volume fraction. The GSA is performed to quantify the influence of fiber volume fraction variation, lamina thickness variation, etc. A nonlinear stage for composite failure prediction based on the Tsai-Wu failure theory was considered. The GSI quantify the relative contribution of variances in material constituents to the total variance of the material under a critical load.
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摘要 :
This presentation deals with the mathematical modeling of composite microstructures for uncertainty quantification of composite structural parameters. Multiple designs of unidirectional fiber reinforced composite materials with ar...
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This presentation deals with the mathematical modeling of composite microstructures for uncertainty quantification of composite structural parameters. Multiple designs of unidirectional fiber reinforced composite materials with arbitrary ply orientations are investigated. We consider a homogenization approach from microscopic to macroscopic scales for the prediction of mechanical properties of the composites. An uncertainty assessment of the effective structural modulus of composite materials consisting of an elastic matrix reinforced with fibers as functions of the phase volume fractions and the structural properties of the constituents is conducted. We consider the global sensitivity analysis (GSA) methods based both on the Fourier Amplitude Sensitivity Test (FAST) and on the Sobol global sensitivity index (GSI). The proposed approach makes it possible to quantify the effective structural parameters of the material based on the variance in the constituents. Numerical results of the GSI and FAST computed for composite materials reveal significant dependence of the macroscopic composite on the probabilistic properties of the fiber volume fraction. The GSA is performed to quantify the influence of fiber volume fraction variation, lamina thickness variation, etc. A nonlinear stage for composite failure prediction based on the Tsai-Wu failure theory was considered. The GSI quantify the relative contribution of variances in material constituents to the total variance of the material under a critical load.
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