A hidden line removal algorithm for bi parametric surfaces is presented and illustrated by some experimental results. The enclosure test is done using area coordinates. A technique of moving box of encirclement is p...A hidden line removal algorithm for bi parametric surfaces is presented and illustrated by some experimental results. The enclosure test is done using area coordinates. A technique of moving box of encirclement is presented. It is found that the algorithm is of general purpose, requires minimal computer storage, has high accuracy and simplicity, and is very easy to be implemented on a computer.展开更多
Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall info...Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall information only. However, detailed analysis is required to find effects of design parameters on the flow distribution. For this aspect, three-dimensional turbulent flow analysis was performed to assess turbulence model performance and effects of upstream pressure and branch pipe geometry. Three different turbulence models of standard k-e model, realizable k-e model and standard k-co yield similar results, indicating small effects of turbulence models on flow characteristics analysis. Geometric variations include area ratio of main and branch pipes, branch pipe diameter, and connection shape of main and branch pipes. Among these parameters, area ratio and branch diameter and shape show strong effect on flow distribution due to high friction and minor loss. Uniform flow distribution is one of common requirements in the branch piping system and this can be achieved with rather high total loss design.展开更多
The present paper discusses the modeling of tool geometry effects on the friction stir aluminum welds using response surface methodology. The friction stir welding tools were designed with different shoulder and tool ...The present paper discusses the modeling of tool geometry effects on the friction stir aluminum welds using response surface methodology. The friction stir welding tools were designed with different shoulder and tool probe geometries based on a design matrix. The matrix for the tool designing was made for three types of tools, based on three types of probes, with three levels each for defining the shoulder surface type and probe profile geometries. Then, the effects of tool shoulder and probe geometries on friction stirred aluminum welds were experimentally investigated with respect to weld strength, weld cross section area, grain size of weld and grain size of thermo-mechanically affected zone. These effects were modeled using multiple and response surface regression analysis. The response surface regression modeling were found to be appropriate for defining the friction stir weldment characteristics.展开更多
The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality(geometry,microstructure and wear rate of cladding track).Self-fluxing ferrous allo...The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality(geometry,microstructure and wear rate of cladding track).Self-fluxing ferrous alloy powders were fabricated on Q235 substrate.Based on the uniform design,the distribution of the experimental samples was designed reasonably in the sample space,which greatly improved efficiency and reduced costs.After a series of microstructural characterization,there was no difference in the phase composition of all samples,but the average grain size had a significant difference,which resulted in the change of wear rate.And the relationship among micro-hardness,average grain size and wear rate of the track had also been investigated.Subsequently,an optimization model was established and the optimal process parameters were obtained with excellent wear rate under the geometric constraints.The correctness of optimization model was verified by experiments.展开更多
Large diameter fans with low solidity are widely used in automotive application for engine cooling. Their designs with small chord length help reducing the torque on the electrical motor and providing a good aerodynam...Large diameter fans with low solidity are widely used in automotive application for engine cooling. Their designs with small chord length help reducing the torque on the electrical motor and providing a good aerodynamic compromise between several operating conditions, some of these being at high flow rate. Their global performances are measured according to the ISO standard DP 5801, which allows comparison of results from different facilities. However, some variations in global performances are observed when considering results from two different test rigs. On a fan selected for the purpose of this study, up to 6 % of efficiency is lost on the worst case. As efficiency is more than ever a key factor to select a component, some experimental and numerical investigations were conducted to analyze the fan behavior on each facility. Two sets of measurement and simulation are performed and compared. Geometries considered for the domain of computation include the test rig plenum, the torquemeter, the ground and a large domain for the atmospheric conditions. The exact fan geometry with tip clearance and under-hub ribs is also considered. Numerical results show a good agreement with experiment in both cases when convergence is reached and for low flow rate when computations are switched to unsteady mode. Comparisons show that simulations are able to capture the different fan behaviors depending on the confguration and those efficiency losses previously observed are correctly predicted. These results are further analyzed to perform some post-processing. Blade loading remains identical for both cases but disparities appear in the wake and its interaction with the surrounding. Tiny details that are often neglected during experiment and/or simulation appear to be the cause of slight variations. Position of the torquemeter and shape of the plenum are among the parameters that various and that have cumulative effects. Efficiency being a ration of pressure and torque, variations are rather important. Finally, these results are discussed in terms of rules for conception and a new geometry less sensible to loss of efficiency is proposed.展开更多
A new framework for free-form surface design is proposed. Using manifolds can generalize the spline scheme to surfaces of arbitrary topology. Physics-based modeling incorporate physical laws into shape representation ...A new framework for free-form surface design is proposed. Using manifolds can generalize the spline scheme to surfaces of arbitrary topology. Physics-based modeling incorporate physical laws into shape representation to provide direct shape interaction. The combination presents a new method inherits the attractive properties of the manifold surface as well as that of the physics-based models.展开更多
Rotary tables are equipments in precision machinery applied in five-axis Machine Tools and CMM （Coordinate Measuring Machines）, offering rotational （C-axis） and tilting motion （A-axis）, allowing the obtaining of...Rotary tables are equipments in precision machinery applied in five-axis Machine Tools and CMM （Coordinate Measuring Machines）, offering rotational （C-axis） and tilting motion （A-axis）, allowing the obtaining of several configurations for manufacturing or inspection of parts with complex geometries. The demand for high accuracy, high efficiency and fewer errors in the positioning of the part in precision machines increases every day, thus ensuring their high confidence and the use of aerostatic bearings enable constructive innovations to the equipment. In this context, this work presents the mechanical design, the development and error analysis of a prototype of an aerostatic rotary table. This study emphasizes the analysis of a prototype that uses the air as a working principle for reducing friction between moving parts, increasing the mechanical efficiency, and its influence of motion error is also discussed based on the experimental results. For the geometrical errors analysis, experimental tests were realized in laboratory using a DBB （Double Ballbar）. The tests are performed with only one axis moving, observing the behavior of the system for different feedrate at the C-axis.展开更多
According to the combination of the complementary medium and transformation optics, the shape of two-dimensional (2D) internal-external cloaks has been generalized into any geometry to adapt to the variety of object s...According to the combination of the complementary medium and transformation optics, the shape of two-dimensional (2D) internal-external cloaks has been generalized into any geometry to adapt to the variety of object shapes. In order to adapt to the practical application, some approximations have been introduced to eliminate the infinite singularity of the parameters in the compressed region by adjusting the principle sketch out of the plane. Firstly, the general parameter equations of the nonsingular cloak with arbitrary cross-section are deduced strictly by the mathematical method based on coordinate transformations in the cylindrical coordinate system. Secondly, taking into account the discontinuous property of the curve functions of arbitrary polygons, a supplementary investigation is given for the nonsingular cloak with arbitrary polygonal cross-section. The transformations in the supplementary study are carried out in the Cartesian coordinate system directly and referred to the coordinates of the polygon's vertices rather than the curve function of the polygon. Last, the invisibility effect of the corresponding cloak is studied by full-wave simulations based on the finite element method. The applicable scope of the 2D internal-external cloak is expanded greatly by the methods and results given in this paper.展开更多
文摘A hidden line removal algorithm for bi parametric surfaces is presented and illustrated by some experimental results. The enclosure test is done using area coordinates. A technique of moving box of encirclement is presented. It is found that the algorithm is of general purpose, requires minimal computer storage, has high accuracy and simplicity, and is very easy to be implemented on a computer.
基金Project supported by Changwon National University in 2010
文摘Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall information only. However, detailed analysis is required to find effects of design parameters on the flow distribution. For this aspect, three-dimensional turbulent flow analysis was performed to assess turbulence model performance and effects of upstream pressure and branch pipe geometry. Three different turbulence models of standard k-e model, realizable k-e model and standard k-co yield similar results, indicating small effects of turbulence models on flow characteristics analysis. Geometric variations include area ratio of main and branch pipes, branch pipe diameter, and connection shape of main and branch pipes. Among these parameters, area ratio and branch diameter and shape show strong effect on flow distribution due to high friction and minor loss. Uniform flow distribution is one of common requirements in the branch piping system and this can be achieved with rather high total loss design.
基金supported by the Department of Scientific and Industrial Research(DSIR),India
文摘The present paper discusses the modeling of tool geometry effects on the friction stir aluminum welds using response surface methodology. The friction stir welding tools were designed with different shoulder and tool probe geometries based on a design matrix. The matrix for the tool designing was made for three types of tools, based on three types of probes, with three levels each for defining the shoulder surface type and probe profile geometries. Then, the effects of tool shoulder and probe geometries on friction stirred aluminum welds were experimentally investigated with respect to weld strength, weld cross section area, grain size of weld and grain size of thermo-mechanically affected zone. These effects were modeled using multiple and response surface regression analysis. The response surface regression modeling were found to be appropriate for defining the friction stir weldment characteristics.
基金Project (51210008) supported by National Natural Science Foundation of China
文摘The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality(geometry,microstructure and wear rate of cladding track).Self-fluxing ferrous alloy powders were fabricated on Q235 substrate.Based on the uniform design,the distribution of the experimental samples was designed reasonably in the sample space,which greatly improved efficiency and reduced costs.After a series of microstructural characterization,there was no difference in the phase composition of all samples,but the average grain size had a significant difference,which resulted in the change of wear rate.And the relationship among micro-hardness,average grain size and wear rate of the track had also been investigated.Subsequently,an optimization model was established and the optimal process parameters were obtained with excellent wear rate under the geometric constraints.The correctness of optimization model was verified by experiments.
文摘Large diameter fans with low solidity are widely used in automotive application for engine cooling. Their designs with small chord length help reducing the torque on the electrical motor and providing a good aerodynamic compromise between several operating conditions, some of these being at high flow rate. Their global performances are measured according to the ISO standard DP 5801, which allows comparison of results from different facilities. However, some variations in global performances are observed when considering results from two different test rigs. On a fan selected for the purpose of this study, up to 6 % of efficiency is lost on the worst case. As efficiency is more than ever a key factor to select a component, some experimental and numerical investigations were conducted to analyze the fan behavior on each facility. Two sets of measurement and simulation are performed and compared. Geometries considered for the domain of computation include the test rig plenum, the torquemeter, the ground and a large domain for the atmospheric conditions. The exact fan geometry with tip clearance and under-hub ribs is also considered. Numerical results show a good agreement with experiment in both cases when convergence is reached and for low flow rate when computations are switched to unsteady mode. Comparisons show that simulations are able to capture the different fan behaviors depending on the confguration and those efficiency losses previously observed are correctly predicted. These results are further analyzed to perform some post-processing. Blade loading remains identical for both cases but disparities appear in the wake and its interaction with the surrounding. Tiny details that are often neglected during experiment and/or simulation appear to be the cause of slight variations. Position of the torquemeter and shape of the plenum are among the parameters that various and that have cumulative effects. Efficiency being a ration of pressure and torque, variations are rather important. Finally, these results are discussed in terms of rules for conception and a new geometry less sensible to loss of efficiency is proposed.
基金Funded by the Chinese National Natural Science Foundation (No.50105013).
文摘A new framework for free-form surface design is proposed. Using manifolds can generalize the spline scheme to surfaces of arbitrary topology. Physics-based modeling incorporate physical laws into shape representation to provide direct shape interaction. The combination presents a new method inherits the attractive properties of the manifold surface as well as that of the physics-based models.
文摘Rotary tables are equipments in precision machinery applied in five-axis Machine Tools and CMM （Coordinate Measuring Machines）, offering rotational （C-axis） and tilting motion （A-axis）, allowing the obtaining of several configurations for manufacturing or inspection of parts with complex geometries. The demand for high accuracy, high efficiency and fewer errors in the positioning of the part in precision machines increases every day, thus ensuring their high confidence and the use of aerostatic bearings enable constructive innovations to the equipment. In this context, this work presents the mechanical design, the development and error analysis of a prototype of an aerostatic rotary table. This study emphasizes the analysis of a prototype that uses the air as a working principle for reducing friction between moving parts, increasing the mechanical efficiency, and its influence of motion error is also discussed based on the experimental results. For the geometrical errors analysis, experimental tests were realized in laboratory using a DBB （Double Ballbar）. The tests are performed with only one axis moving, observing the behavior of the system for different feedrate at the C-axis.
文摘According to the combination of the complementary medium and transformation optics, the shape of two-dimensional (2D) internal-external cloaks has been generalized into any geometry to adapt to the variety of object shapes. In order to adapt to the practical application, some approximations have been introduced to eliminate the infinite singularity of the parameters in the compressed region by adjusting the principle sketch out of the plane. Firstly, the general parameter equations of the nonsingular cloak with arbitrary cross-section are deduced strictly by the mathematical method based on coordinate transformations in the cylindrical coordinate system. Secondly, taking into account the discontinuous property of the curve functions of arbitrary polygons, a supplementary investigation is given for the nonsingular cloak with arbitrary polygonal cross-section. The transformations in the supplementary study are carried out in the Cartesian coordinate system directly and referred to the coordinates of the polygon's vertices rather than the curve function of the polygon. Last, the invisibility effect of the corresponding cloak is studied by full-wave simulations based on the finite element method. The applicable scope of the 2D internal-external cloak is expanded greatly by the methods and results given in this paper.
