In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in th...In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.展开更多
In this paper new criteria for designing of temporary architectures, which can be used as a uniform coverage for open spaces, are discussed. Frequently temporary architectures use building techniques and materials lig...In this paper new criteria for designing of temporary architectures, which can be used as a uniform coverage for open spaces, are discussed. Frequently temporary architectures use building techniques and materials lightweight. In the case of temporary architectures the theme of sustainability requires that the structure can be reused in different occasions and contexts. The solution to these issues, developed in this paper, makes use of a innovative constructive procedure of prestressed masonry in blocks of natural stone. This procedure is used for the construction of the vertical supports of the cover, consisting of a tensostructure with shape of hyperboloid, obtained by products standard （steel profiles and membrane）. The columns with prestressed blocks of natural stone, dry assembled, allow you to have a modular structure, easily assembled and disassembled, with full recovery of all elements; the stone columns, due to their weight, are able to stabilize the whole structure, even to the dynamic stresses, without using any type of foundation structure fixed to the ground. This paper shows the description of all the elements that make up the new type of temporary architecture designed.展开更多
An optimum design model has been proposed for carbon/carbon ablative property based on genetic algorithm,in which the optimum parameters are the number of woven satins,K of fiber bundles,layers per unit height,the ave...An optimum design model has been proposed for carbon/carbon ablative property based on genetic algorithm,in which the optimum parameters are the number of woven satins,K of fiber bundles,layers per unit height,the average distance of puncture fibers in Z direction and Ply Stacking angle,and the constraint conditions are the density and diameter of carbon fibers and the density of carbon matrix.The results demonstrate that after optimization,the overall height of the ablative carbon/carbon surface is reduced by 56.5%,the standard deviation is reduced by 34.9% and the surface roughness is reduced by 12.6%,which suggests the remarkable improvement of ablative homogeneity.The present investigation can provide practical methodology for the optimum design of carbon/carbon ablative property and the development of new carbon/carbon composites.展开更多
This paper presents studies of aeroelastic optimization on composite skins of large aircraft wings subject to aeroelastic constraints and strength/strain constraints. The design variable for optimization was the ply t...This paper presents studies of aeroelastic optimization on composite skins of large aircraft wings subject to aeroelastic constraints and strength/strain constraints. The design variable for optimization was the ply thickness of the wing skin panels, and the structural weight was the objective function to be minimised. The impacts of three strength/strain constraints and the ply proportion of the wing skin panels on the optimization results are discussed. The results indicate that the optimal composite wings that satisfy different constraints have remarkable weight advantages over metal wing. High levels of stiffness can be achieved while satisfying the constraints regarding allowable design strains and failure criteria. The optimization results with variable-proportions indicate that wing skins with higher proportions of 0° plies from the root to the middle segment and ±45° plies outboard have a more efficient and reasonable stiffness distribution.展开更多
基金Project(2007BAE38B00) supported by the National Key Technology R&D Program in the 11th Five Year Plan of China
文摘In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.
文摘In this paper new criteria for designing of temporary architectures, which can be used as a uniform coverage for open spaces, are discussed. Frequently temporary architectures use building techniques and materials lightweight. In the case of temporary architectures the theme of sustainability requires that the structure can be reused in different occasions and contexts. The solution to these issues, developed in this paper, makes use of a innovative constructive procedure of prestressed masonry in blocks of natural stone. This procedure is used for the construction of the vertical supports of the cover, consisting of a tensostructure with shape of hyperboloid, obtained by products standard （steel profiles and membrane）. The columns with prestressed blocks of natural stone, dry assembled, allow you to have a modular structure, easily assembled and disassembled, with full recovery of all elements; the stone columns, due to their weight, are able to stabilize the whole structure, even to the dynamic stresses, without using any type of foundation structure fixed to the ground. This paper shows the description of all the elements that make up the new type of temporary architecture designed.
基金Sponsored by the National Natural Science Foundation of China(Grant No.1057244)
文摘An optimum design model has been proposed for carbon/carbon ablative property based on genetic algorithm,in which the optimum parameters are the number of woven satins,K of fiber bundles,layers per unit height,the average distance of puncture fibers in Z direction and Ply Stacking angle,and the constraint conditions are the density and diameter of carbon fibers and the density of carbon matrix.The results demonstrate that after optimization,the overall height of the ablative carbon/carbon surface is reduced by 56.5%,the standard deviation is reduced by 34.9% and the surface roughness is reduced by 12.6%,which suggests the remarkable improvement of ablative homogeneity.The present investigation can provide practical methodology for the optimum design of carbon/carbon ablative property and the development of new carbon/carbon composites.
文摘This paper presents studies of aeroelastic optimization on composite skins of large aircraft wings subject to aeroelastic constraints and strength/strain constraints. The design variable for optimization was the ply thickness of the wing skin panels, and the structural weight was the objective function to be minimised. The impacts of three strength/strain constraints and the ply proportion of the wing skin panels on the optimization results are discussed. The results indicate that the optimal composite wings that satisfy different constraints have remarkable weight advantages over metal wing. High levels of stiffness can be achieved while satisfying the constraints regarding allowable design strains and failure criteria. The optimization results with variable-proportions indicate that wing skins with higher proportions of 0° plies from the root to the middle segment and ±45° plies outboard have a more efficient and reasonable stiffness distribution.
