An improved three-dimensional （3-D） experimental visualization methodology is presented tor evaluating the fracture mechanisms of ferritic stainless steels by in-situ tensile testing with an environmental scanning e...An improved three-dimensional （3-D） experimental visualization methodology is presented tor evaluating the fracture mechanisms of ferritic stainless steels by in-situ tensile testing with an environmental scanning electron microscope （ESEM）. The samples were machined with a radial notched shape and a sloped surface. Both planar surface deformation and sloping surface deformation-induced microvoids were observed during dynamic tension experiments, where a greater amount of information could be obtained from the sloping surface. The results showed that microvoids formed at the grain boundaries of highly elongated large grains. The microvoids nucleated in the severely deformed regions grew nearly parallel to the tensile axis, predominantly along the grain boundaries. The microvoids nucleated at the interface of particles and the matrix did not propagate due to the high plasticity of the matrix. The large microvoids propagated and showed a zigzag shape along the grain boundaries,seemingly a consequence of the fracture of the slip bands caused by dislocation pile-ups. The final failure took place due to the reduction of the load-beating area.展开更多
Effectively and accurately modelling the spatial relation of fracture surfaces is crucial in the design and construction of large hydropower dams having a complex underlying geology. However, fracture surfaces are ran...Effectively and accurately modelling the spatial relation of fracture surfaces is crucial in the design and construction of large hydropower dams having a complex underlying geology. However, fracture surfaces are randomly formed and vary greatly with respect to their spatial distribution, which makes the construction of accurate 3-D models challenging. In this study, we use an optimal Monte Carlo simulation and dynamic conditioning to construct a fracture network model. We found the optimal Monte Carlo simulation to effectively reduce the error associated with the Monte Carlo method and use dynamic conditioning to ensure the consistency of the model with the actual distribution of fractures on the excavation faces and outcrops. We applied this novel approach to a hydropower station on the Jinshajiang River, China. The simulation results matched the real sampled values well, confirming that the model is capable of effectively and accurately simulating the spatial relations in a fracture network.展开更多
In this article, we present a three-dimensional visualization technique that has been developed in order to establish an interactive immersive environment to visualize the particles in granular materials and dislocati...In this article, we present a three-dimensional visualization technique that has been developed in order to establish an interactive immersive environment to visualize the particles in granular materials and dislocations in crystals. Simple elementary objects often exhibit complex collective behavior. Understanding of such behaviors and developments of coarse-scale theories, often requires insight into collective behavior that can only be obtained through immersive visualization. By displaying the computational results in a virtual environment with three-dimensional perception, one can immerse inside the model and analyze the intricate and very complex behavior of individual particles and dislocations. We built the stereographic images of the models using OpenGL rendering technique and then combine with the Virtual Reality technology in order to immerse in the three-dimensional model. A head mounted display has been used to allow the user to immerse inside the models and a flock of birds tracking device that allows the movements around and within the immersive environment.展开更多
The anadromous fish can pass through turbines of run-of-the-river hydropower stations to reach the downstream watershed, but their mortality is significant because of the complex turbine structure, the fast-rotating r...The anadromous fish can pass through turbines of run-of-the-river hydropower stations to reach the downstream watershed, but their mortality is significant because of the complex turbine structure, the fast-rotating runner, and the special flow patterns. Numerical simulations of the dynamics of fish passing are a challenging task, because the fish motion in the turbines involves a strong fluid-structure interaction (FSI). In this paper, the 3-D immersed boundary-lattice Boltzmann (IB-LB) coupling scheme is proposed to treat the FSI between the water and the fish. The process of one fish and three fish passing through a tubular turbine is simulated on a graphics processing unit (GPU) platform. The fish motion postures (translation and rotation), the fish body pressure distributions and histories are analyzed, and the results are consistent with the previous studies. This paper presents the IB-LB models, the simulation procedures, the specific treatments, and related results, to demonstrate the effectiveness of the IB-LB coupling scheme in simulating FSI problems and its application prospects in developing fish-friendly turbines.展开更多
文摘An improved three-dimensional （3-D） experimental visualization methodology is presented tor evaluating the fracture mechanisms of ferritic stainless steels by in-situ tensile testing with an environmental scanning electron microscope （ESEM）. The samples were machined with a radial notched shape and a sloped surface. Both planar surface deformation and sloping surface deformation-induced microvoids were observed during dynamic tension experiments, where a greater amount of information could be obtained from the sloping surface. The results showed that microvoids formed at the grain boundaries of highly elongated large grains. The microvoids nucleated in the severely deformed regions grew nearly parallel to the tensile axis, predominantly along the grain boundaries. The microvoids nucleated at the interface of particles and the matrix did not propagate due to the high plasticity of the matrix. The large microvoids propagated and showed a zigzag shape along the grain boundaries,seemingly a consequence of the fracture of the slip bands caused by dislocation pile-ups. The final failure took place due to the reduction of the load-beating area.
基金supported by the National Basic Research Program of China (973 Program, No. 2013CB035904)the Innovative Research Groups of the National Natural Science Foundation of China (No. 51321065)the National Natural Science Foundation of China (No. 51439005)
文摘Effectively and accurately modelling the spatial relation of fracture surfaces is crucial in the design and construction of large hydropower dams having a complex underlying geology. However, fracture surfaces are randomly formed and vary greatly with respect to their spatial distribution, which makes the construction of accurate 3-D models challenging. In this study, we use an optimal Monte Carlo simulation and dynamic conditioning to construct a fracture network model. We found the optimal Monte Carlo simulation to effectively reduce the error associated with the Monte Carlo method and use dynamic conditioning to ensure the consistency of the model with the actual distribution of fractures on the excavation faces and outcrops. We applied this novel approach to a hydropower station on the Jinshajiang River, China. The simulation results matched the real sampled values well, confirming that the model is capable of effectively and accurately simulating the spatial relations in a fracture network.
文摘In this article, we present a three-dimensional visualization technique that has been developed in order to establish an interactive immersive environment to visualize the particles in granular materials and dislocations in crystals. Simple elementary objects often exhibit complex collective behavior. Understanding of such behaviors and developments of coarse-scale theories, often requires insight into collective behavior that can only be obtained through immersive visualization. By displaying the computational results in a virtual environment with three-dimensional perception, one can immerse inside the model and analyze the intricate and very complex behavior of individual particles and dislocations. We built the stereographic images of the models using OpenGL rendering technique and then combine with the Virtual Reality technology in order to immerse in the three-dimensional model. A head mounted display has been used to allow the user to immerse inside the models and a flock of birds tracking device that allows the movements around and within the immersive environment.
基金supported by the National Natural Science Foundation of China(Grant Nos.51839008,51579187 and 11172219)supported by the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130141110013).
文摘The anadromous fish can pass through turbines of run-of-the-river hydropower stations to reach the downstream watershed, but their mortality is significant because of the complex turbine structure, the fast-rotating runner, and the special flow patterns. Numerical simulations of the dynamics of fish passing are a challenging task, because the fish motion in the turbines involves a strong fluid-structure interaction (FSI). In this paper, the 3-D immersed boundary-lattice Boltzmann (IB-LB) coupling scheme is proposed to treat the FSI between the water and the fish. The process of one fish and three fish passing through a tubular turbine is simulated on a graphics processing unit (GPU) platform. The fish motion postures (translation and rotation), the fish body pressure distributions and histories are analyzed, and the results are consistent with the previous studies. This paper presents the IB-LB models, the simulation procedures, the specific treatments, and related results, to demonstrate the effectiveness of the IB-LB coupling scheme in simulating FSI problems and its application prospects in developing fish-friendly turbines.
