Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing e...Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming. Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.展开更多
Turbine blade is one of the critical components of aircraft engine.The performance of the engine depends on the shape and dimensions of components,but superalloy blade material cannot be easily machined.Although inves...Turbine blade is one of the critical components of aircraft engine.The performance of the engine depends on the shape and dimensions of components,but superalloy blade material cannot be easily machined.Although investment casting is an ideal process for such net-shape components,it requires an accurate determination of the casting-die profile.In this paper,a reversing design methodology for investment casting die using ProCAST is proposed.By combining the methods of simplifying grid files and quick sorting,the efficiency of sorting and matching can be largely improved.Further,the mould/die cavity anti-deformation system can be easily built.With ProCAST,the optimized die profile for investment casting can be established.展开更多
A hybrid reasoning model was proposed in which CBR(case-based reasoning)was applied to the conceptual design and RBR(rule-based reasoning)was applied to the detailed design after research of the design process and dom...A hybrid reasoning model was proposed in which CBR(case-based reasoning)was applied to the conceptual design and RBR(rule-based reasoning)was applied to the detailed design after research of the design process and domain knowledge of the aero-engine turbine blade investment casting mold design field.In the conceptual design stage,the representation and retrieval technologies were researched which improve the retrieval efficiency.Meanwhile,RBR was used to modify the retrieval result.The experimentation shows that the approach in this study can be used to obtain a more satisfactory design result.展开更多
The nature of networked manufacturing and agile manufacturing is to recognize enterprise resources timely and accurately. This paper mainly discusses an enterprise resource model method and the construction process. F...The nature of networked manufacturing and agile manufacturing is to recognize enterprise resources timely and accurately. This paper mainly discusses an enterprise resource model method and the construction process. Furthermore, the system frameworks of software and application are put forward to realize various enterprise resources management based on a resource business process. Thus, we ensure the integration and sharing of enterprise resources for the requirement of networked manufacturing.展开更多
Recent development and recognition methods of raster to vector conversion for engineering drawings are presented. The advantages and disadvantages of all existing models are analyzed. Some research challenges and futu...Recent development and recognition methods of raster to vector conversion for engineering drawings are presented. The advantages and disadvantages of all existing models are analyzed. Some research challenges and future directions are discussed.展开更多
As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of...As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.展开更多
To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the ...To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the turbine blade investment casting die design field. The key technologies of the intelligent design method were researched and a prototype system was developed. A hybrid reasoning model was prompted in which case-based reasoning (CBR) was applied to conceptual design and rule-based reasoning (RBR) was applied to parts design after research the design process and domain knowledge of casting die. In the conceptual design stage,a retrieval model which integrated nearest neighbor approach and knowledge-based retrieval approach was prompted to improve the retrieval efficiency. Meanwhile,RBR was used to modify the retrieval result. The practical application results indicate that this system can reuse the expert experience efficiently and heighten the die design efficiency and quality.展开更多
The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the pe...The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the performance, fatigue durability and damage of the riveting structure in the aircraft. This paper researches the riveting process mathematics modeling and simulating to more accurately analyze deformation of thin-walled sheet-metal parts. First, the mathematics and mechanics models for the elastic deformation, plastic deformation and springback of the rivet are built by mechanics theory. Second, on the basis of ABAQUS system, a finite element system, an instance made up of the rivet and two thin-walled sheet-metal parts of aluminum alloy is used to analyze and simulate the stress and deformation. What＇s more, a comparison is made between the results obtained by the mathematics and mechanics models and those by finite element method （FEM）. The models are proved true by the calculating and simulation results of the instance.展开更多
In situ formed TiB2 particle reinforced aluminum matrix composites （TiB2/Al MMCs） have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influen...In situ formed TiB2 particle reinforced aluminum matrix composites （TiB2/Al MMCs） have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influence of TiB2 particles, the machinability is still a problem which restricts the application of TiB2/Al MMCs. In order to meet the industrial requirements, the influence of TiB2 particles on the machinability of TiB2/Al MMCs was investigated experimentally. Moreover, the optimal machining conditions for this kind of MMCs were investigated in this study. The major conclusions are： （1） the machining force of TiB2/Al MMCs is bigger than that of non- reinforced alloy and mainly controlled by feed rate; （2） the residual stress of TiB2/AI MMCs is compressive while that of non-reinforced alloy is nearly neutral; （3） the surface roughness of TiB2/Al MMCs is smaller than that of non-reinforced alloy under the same cutting speed, but reverse result was observed when the feed rate increased; （4） a multi-objective optimization model for surface roughness and material removal rate （MRR） was established, and a set of optimal parameter combinations of the machining was obtained. The results show a great difference from SiC particle reinforced MMCs and provide a useful guide for a better control of machining process of this material.展开更多
Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin content.The accuracy of pressure control systems is af...Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin content.The accuracy of pressure control systems is affected by nonlinear disturbances,such as friction,parameter perturbation,and measurement noise.A robust control algorithm based on linear quadratic optimal control and sliding mode control(LQSMC)is proposed to overcome these problems.The method is based on the system state space expression and linear quadratic optimal control.The state space model of the system is improved by using a Kalman filter and control input for state estimation,and a new sliding surface equation is defined.The ameliorated control algorithm exhibits good performance and can effectively suppress sliding mode control(SMC)chattering.Simulation and experimental results show that LQSMC offers high control precision,much stronger antiinterference,and robustness,which can effectively improve the positioning and tracking accuracy of a pressure control system compared with linear quadratic optimal control(LQC).The winding pressure control precision is improved by 45%to 50%.The results show that the porosity of composite fiber tape winding products decreased thanks to our method.展开更多
The purpose of this paper is to present an extended topology optimization method for the stiffeners layout design of aircraft assembled structures. Multi-fastener joint loads and manufacturing constraints are consider...The purpose of this paper is to present an extended topology optimization method for the stiffeners layout design of aircraft assembled structures. Multi-fastener joint loads and manufacturing constraints are considered simultaneously. On one hand, the joint loads are calculated and constrained within a limited value to avoid the failure of fasteners. On the other hand, the manufacturing constraints of the material distribution in the machining directions of stiffeners are implemented by an improved piecewise interpolation based on a beveled cut-surface. It is proven that the objective function is strictly continuous and differentiable with respect to the piecewise interpolation. The effects of the extended method with two different constraints are highlighted by typical numerical examples. Compared with the standard topology optimization, the final designs have clearly shown the layout of stiffeners and the joint loads have been perfectly constrained to a satisfying level.展开更多
The traditional strategy of 3D model reconstruction mainly concentrates on orthographic projections or engineering drawings. But there are some shortcomings. Such as, only few kinds of solids can be reconstructed, the...The traditional strategy of 3D model reconstruction mainly concentrates on orthographic projections or engineering drawings. But there are some shortcomings. Such as, only few kinds of solids can be reconstructed, the high complexity of time and less information about the 3D model. The research is extended and process card is treated as part of the 3D reconstruction. A set of process data is a superset of 2D engineering drawings set. The set comprises process drawings and process steps, and shows a sequencing and asymptotic course that a part is made from roughcast blank to final product. According to these characteristics, the object to be reconstructed is translated from the complicated engineering drawings into a series of much simpler process drawings. With the plentiful process information added for reconstruction, the disturbances such as irrelevant graph, symbol and label, etc. can be avoided. And more, the form change of both neighbor process drawings is so little that the engineering drawings interpretation has no difficulty; in addition, the abnormal solution and multi-solution can be avoided during reconstruction, and the problems of being applicable to more objects is solved ultimately. Therefore, the utility method for 3D reconstruction model will be possible. On the other hand, the feature information in process cards is provided for reconstruction model. Focusing on process cards, the feasibility and requirements of Working Procedure Model reconstruction is analyzed, and the method to apply and implement the Natural Language Understanding into the 3D reconstruction is studied. The method of asymptotic approximation product was proposed, by which a 3D process model can be constructed automatically and intelligently. The process model not only includes the information about parts characters, but also can deliver the information of design, process and engineering to the downstream applications.展开更多
This paper presents a comprehensive investigation on the effects of tool and turning parameters on surface integrity and fatigue behavior in turning c-Ti Al alloy. The wear of inserts surface, cutting forces, and surf...This paper presents a comprehensive investigation on the effects of tool and turning parameters on surface integrity and fatigue behavior in turning c-Ti Al alloy. The wear of inserts surface, cutting forces, and surface roughness were studied to optimize PVD-coated carbide inserts.Surface topography, residual stresses, microhardness, and microstructure were analyzed to characterize the surfaces layer under different turning parameters. Surface integrity and fatigue life tests of c-Ti Al alloy were conducted under turning and turning-polishing processes. The results show that compared to CNMG120412-MF4, CNMG120408-SM is more suitable because it obtained low cutting force, surface roughness, and tool wear. With increasing the cutting speed and depth, the depths of the compressive residual stress layer, hardening layer, and plastic deformation layer increased. For turning and turning-polishing specimens, the compressive residual stress was relaxed by less than 20%–30% after 10^7 cycles. The fatigue life of a turning-polishing specimen with Ra= 0.15 mm has increased 3 times from that of a turning specimen with Ra= 0.43 mm.展开更多
An improved method to determine cutting force coefficients for bull-nose cutters is proposed based on the semi-mechanistic cutting force model. Due to variations of cutting speed along the tool axis in bull-nose milli...An improved method to determine cutting force coefficients for bull-nose cutters is proposed based on the semi-mechanistic cutting force model. Due to variations of cutting speed along the tool axis in bull-nose milling, they affect coefficients significantly and may bring remarkable discrepancies in the prediction of cutting forces. Firstly, the bull-nose cutter is regarded as a finite number of axial discs piled up along the tool axis, and the rigid cutting force model is exerted. Then through discretization along cutting edges, the cutting force related to each element is recalculated, which equals to differential force value between the current and previous elements. In addition, coefficient identification adopts the cubic polynomial fitting method with the slice elevation as its horizontal axis. By calculating relations of cutting speed and cutting depth, the influences of speed variations on cutting force can be derived. Thereby, several tests are conducted to calibrate the coefficients using the improved method, which are applied to later force predictions. Eventually, experimental evaluations are discussed to verify the effectiveness. Compared to the conventional method, the results are more accurate and show satisfactory consistency with the simulations. For further applications, the method is instructive to predict the cutting forces in bull-nose milling with lead or tilt angles and can be extended to the selection of cutting parameters.展开更多
Machining quality of clean-up region has a strong influence on the performances of the impeller. In order to plan clean-up tool paths rapidly and obtain good finish surface quality, an efficient and robust tool path g...Machining quality of clean-up region has a strong influence on the performances of the impeller. In order to plan clean-up tool paths rapidly and obtain good finish surface quality, an efficient and robust tool path generation method is presented, which employs an approach based on point-searching. The clean-up machining mentioned in this paper is pencil-cut and multilayer fillet-cut for a free-form model with a ball-end cutter. For pencil-cut, the cutter center position can be determined via judging whether it satisfies the distance requirement. After the searching direction and the tracing direction have been determined, by employing the point-searching algorithm with the idea of dichotomy, all the cutter contact （CC） points and cutter location （CL） points can be found and the clean-up boundaries can also be defined rapidly. Then the tool path is generated. Based on the main concept of pencil-cut, a multilayer fillet-cut method is proposed, which utilizes a ball-end cutter with its radius less than the design radius of clean-up region. Using a sequence of intermediate virtual cutters to divide the clean-up region into several layers and given a cusp-height tolerance for the final layer, then the tool paths for all layers are calculated. Finally, computer implementation is also presented in this paper, and the result shows that the proposed method is feasible.展开更多
There are numerous riveting points on the large-sized aircraft panel, irregular row of riveting points on delta wing. It is essential to plan the riveting sequence reasonably to improve the efficiency and accuracy of ...There are numerous riveting points on the large-sized aircraft panel, irregular row of riveting points on delta wing. It is essential to plan the riveting sequence reasonably to improve the efficiency and accuracy of automatic drilling and riveting. Therefore, this article presents a new multi-objective optimization method based on ant colony optimization （ACO）. Multi-objective optimization model of automatic drilling and riveting sequence planning is built by expressing the efficiency and accuracy of riveting as functions of the points＇ coordinates. In order to search the sequences efficiently and improve the quality of the sequences, a new local pheromone updating rule is applied when the ants search sequences. Pareto dominance is incorporated into the proposed ACO to find out the non-dominated sequences. This method is tested on a hyperbolicity panel model of ARJ21 and the result shows its feasibility and superiority compared with particle swarm optimization （PSO） and genetic algorithm （GA）.展开更多
Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation.A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of t...Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation.A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the threedimensional turning effect and impingement like flow.Improved internal convective cooling is therefore required to increase the blade tip lifetime.In the present study,augmented heat transfer of an internal blade tip with pin-fin arrays has been investigated numerically using a conjugate heat transfer method.The computational domain includes the fluid region and the solid pins as well as the tip regions.Turbulent convective heat transfer between the fluid and pins,and heat conduction within pins and tip are simultaneously computed.The main objective of the present study is to observe the effect of the pin material on heat transfer enhancement of the pin-finned tips.It is found that due to the combination of turning,impingement and pin-fin crossflow,the heat transfer coefficient of a pin-finned tip is a factor of 2.9 higher than that of a smooth tip at the cost of an increased pressure drop by less than 10%.The usage of metal pins can reduce the tip temperature effectively and thereby remove the heat load from the tip.Also,it is found that the tip heat transfer is enhanced even by using insulating pins having low thermal conductivity at low Reynolds numbers.The comparisons of overall performances are also included.展开更多
基金National Natural Science Foundation of China （90405016, 10676028） 973 Program （2006CB601205）+1 种基金 863 Project （2006AA04Z 122） Aeronautical Science Foundation （04B53080, 2006ZA 53006） and 111 Project （B07050）
文摘Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming. Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.
基金supported by National Key Technologies R&D Program under Grant No. 2006BAF04B02
文摘Turbine blade is one of the critical components of aircraft engine.The performance of the engine depends on the shape and dimensions of components,but superalloy blade material cannot be easily machined.Although investment casting is an ideal process for such net-shape components,it requires an accurate determination of the casting-die profile.In this paper,a reversing design methodology for investment casting die using ProCAST is proposed.By combining the methods of simplifying grid files and quick sorting,the efficiency of sorting and matching can be largely improved.Further,the mould/die cavity anti-deformation system can be easily built.With ProCAST,the optimized die profile for investment casting can be established.
基金supported by National High-tech R&D Program(863 Program)(2006AA04Z144)Key Technologies R&D Program(2006BAF04B02)
文摘A hybrid reasoning model was proposed in which CBR(case-based reasoning)was applied to the conceptual design and RBR(rule-based reasoning)was applied to the detailed design after research of the design process and domain knowledge of the aero-engine turbine blade investment casting mold design field.In the conceptual design stage,the representation and retrieval technologies were researched which improve the retrieval efficiency.Meanwhile,RBR was used to modify the retrieval result.The experimentation shows that the approach in this study can be used to obtain a more satisfactory design result.
文摘The nature of networked manufacturing and agile manufacturing is to recognize enterprise resources timely and accurately. This paper mainly discusses an enterprise resource model method and the construction process. Furthermore, the system frameworks of software and application are put forward to realize various enterprise resources management based on a resource business process. Thus, we ensure the integration and sharing of enterprise resources for the requirement of networked manufacturing.
文摘Recent development and recognition methods of raster to vector conversion for engineering drawings are presented. The advantages and disadvantages of all existing models are analyzed. Some research challenges and future directions are discussed.
基金supported by National Science and Technology Major Project of the Ministry of Science and Technology of China (No. 2013ZX04001081)
文摘As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.
文摘To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the turbine blade investment casting die design field. The key technologies of the intelligent design method were researched and a prototype system was developed. A hybrid reasoning model was prompted in which case-based reasoning (CBR) was applied to conceptual design and rule-based reasoning (RBR) was applied to parts design after research the design process and domain knowledge of casting die. In the conceptual design stage,a retrieval model which integrated nearest neighbor approach and knowledge-based retrieval approach was prompted to improve the retrieval efficiency. Meanwhile,RBR was used to modify the retrieval result. The practical application results indicate that this system can reuse the expert experience efficiently and heighten the die design efficiency and quality.
基金National Natural Science Foundation of China （50805119） Aeronautical Science Foundation in China （2010ZE53049） Fund of National Engineering and Research Center for Commercial Aircraft Manufacturing （SAMC11 -JS-07-200）
文摘The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the performance, fatigue durability and damage of the riveting structure in the aircraft. This paper researches the riveting process mathematics modeling and simulating to more accurately analyze deformation of thin-walled sheet-metal parts. First, the mathematics and mechanics models for the elastic deformation, plastic deformation and springback of the rivet are built by mechanics theory. Second, on the basis of ABAQUS system, a finite element system, an instance made up of the rivet and two thin-walled sheet-metal parts of aluminum alloy is used to analyze and simulate the stress and deformation. What＇s more, a comparison is made between the results obtained by the mathematics and mechanics models and those by finite element method （FEM）. The models are proved true by the calculating and simulation results of the instance.
基金co-supported by the National Natural Science Foundation of China(No.51505387)the China Postdoctoral Science Foundation funded project(No.2016M602860)the 111 project(No.B13044)
文摘In situ formed TiB2 particle reinforced aluminum matrix composites （TiB2/Al MMCs） have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influence of TiB2 particles, the machinability is still a problem which restricts the application of TiB2/Al MMCs. In order to meet the industrial requirements, the influence of TiB2 particles on the machinability of TiB2/Al MMCs was investigated experimentally. Moreover, the optimal machining conditions for this kind of MMCs were investigated in this study. The major conclusions are： （1） the machining force of TiB2/Al MMCs is bigger than that of non- reinforced alloy and mainly controlled by feed rate; （2） the residual stress of TiB2/AI MMCs is compressive while that of non-reinforced alloy is nearly neutral; （3） the surface roughness of TiB2/Al MMCs is smaller than that of non-reinforced alloy under the same cutting speed, but reverse result was observed when the feed rate increased; （4） a multi-objective optimization model for surface roughness and material removal rate （MRR） was established, and a set of optimal parameter combinations of the machining was obtained. The results show a great difference from SiC particle reinforced MMCs and provide a useful guide for a better control of machining process of this material.
基金supported by the National Natural Science Foundation of China(No.51505356).
文摘Pressure fluctuations during the composite fiber winding process seriously affect the produces compactness strength,fatigue resistance,stress uniformity,and resin content.The accuracy of pressure control systems is affected by nonlinear disturbances,such as friction,parameter perturbation,and measurement noise.A robust control algorithm based on linear quadratic optimal control and sliding mode control(LQSMC)is proposed to overcome these problems.The method is based on the system state space expression and linear quadratic optimal control.The state space model of the system is improved by using a Kalman filter and control input for state estimation,and a new sliding surface equation is defined.The ameliorated control algorithm exhibits good performance and can effectively suppress sliding mode control(SMC)chattering.Simulation and experimental results show that LQSMC offers high control precision,much stronger antiinterference,and robustness,which can effectively improve the positioning and tracking accuracy of a pressure control system compared with linear quadratic optimal control(LQC).The winding pressure control precision is improved by 45%to 50%.The results show that the porosity of composite fiber tape winding products decreased thanks to our method.
基金supported by National Natural Science Foundation of China (Nos. 11432011, 11620101002)National key research and development program of China (No. 2017YFB1102800)Key Research and Development Program of Shaanxi, China (No. S2017-ZDYF-ZDXM-GY-0035)
文摘The purpose of this paper is to present an extended topology optimization method for the stiffeners layout design of aircraft assembled structures. Multi-fastener joint loads and manufacturing constraints are considered simultaneously. On one hand, the joint loads are calculated and constrained within a limited value to avoid the failure of fasteners. On the other hand, the manufacturing constraints of the material distribution in the machining directions of stiffeners are implemented by an improved piecewise interpolation based on a beveled cut-surface. It is proven that the objective function is strictly continuous and differentiable with respect to the piecewise interpolation. The effects of the extended method with two different constraints are highlighted by typical numerical examples. Compared with the standard topology optimization, the final designs have clearly shown the layout of stiffeners and the joint loads have been perfectly constrained to a satisfying level.
文摘The traditional strategy of 3D model reconstruction mainly concentrates on orthographic projections or engineering drawings. But there are some shortcomings. Such as, only few kinds of solids can be reconstructed, the high complexity of time and less information about the 3D model. The research is extended and process card is treated as part of the 3D reconstruction. A set of process data is a superset of 2D engineering drawings set. The set comprises process drawings and process steps, and shows a sequencing and asymptotic course that a part is made from roughcast blank to final product. According to these characteristics, the object to be reconstructed is translated from the complicated engineering drawings into a series of much simpler process drawings. With the plentiful process information added for reconstruction, the disturbances such as irrelevant graph, symbol and label, etc. can be avoided. And more, the form change of both neighbor process drawings is so little that the engineering drawings interpretation has no difficulty; in addition, the abnormal solution and multi-solution can be avoided during reconstruction, and the problems of being applicable to more objects is solved ultimately. Therefore, the utility method for 3D reconstruction model will be possible. On the other hand, the feature information in process cards is provided for reconstruction model. Focusing on process cards, the feasibility and requirements of Working Procedure Model reconstruction is analyzed, and the method to apply and implement the Natural Language Understanding into the 3D reconstruction is studied. The method of asymptotic approximation product was proposed, by which a 3D process model can be constructed automatically and intelligently. The process model not only includes the information about parts characters, but also can deliver the information of design, process and engineering to the downstream applications.
基金financial support for this work by the National Natural Science Foundation of China (No. 51375393)
文摘This paper presents a comprehensive investigation on the effects of tool and turning parameters on surface integrity and fatigue behavior in turning c-Ti Al alloy. The wear of inserts surface, cutting forces, and surface roughness were studied to optimize PVD-coated carbide inserts.Surface topography, residual stresses, microhardness, and microstructure were analyzed to characterize the surfaces layer under different turning parameters. Surface integrity and fatigue life tests of c-Ti Al alloy were conducted under turning and turning-polishing processes. The results show that compared to CNMG120412-MF4, CNMG120408-SM is more suitable because it obtained low cutting force, surface roughness, and tool wear. With increasing the cutting speed and depth, the depths of the compressive residual stress layer, hardening layer, and plastic deformation layer increased. For turning and turning-polishing specimens, the compressive residual stress was relaxed by less than 20%–30% after 10^7 cycles. The fatigue life of a turning-polishing specimen with Ra= 0.15 mm has increased 3 times from that of a turning specimen with Ra= 0.43 mm.
基金the Postgraduate Seed Fund of Northwestern Polytechnical University(No.Z2012038)National Natural Science Foundation of China(No.51005183)National Key S&T Special Projects(No.2011X04016-031)
文摘An improved method to determine cutting force coefficients for bull-nose cutters is proposed based on the semi-mechanistic cutting force model. Due to variations of cutting speed along the tool axis in bull-nose milling, they affect coefficients significantly and may bring remarkable discrepancies in the prediction of cutting forces. Firstly, the bull-nose cutter is regarded as a finite number of axial discs piled up along the tool axis, and the rigid cutting force model is exerted. Then through discretization along cutting edges, the cutting force related to each element is recalculated, which equals to differential force value between the current and previous elements. In addition, coefficient identification adopts the cubic polynomial fitting method with the slice elevation as its horizontal axis. By calculating relations of cutting speed and cutting depth, the influences of speed variations on cutting force can be derived. Thereby, several tests are conducted to calibrate the coefficients using the improved method, which are applied to later force predictions. Eventually, experimental evaluations are discussed to verify the effectiveness. Compared to the conventional method, the results are more accurate and show satisfactory consistency with the simulations. For further applications, the method is instructive to predict the cutting forces in bull-nose milling with lead or tilt angles and can be extended to the selection of cutting parameters.
基金National Natural Science Foundation of China （51005183） National Science and Technology Major Project （2011X04016-031）
文摘Machining quality of clean-up region has a strong influence on the performances of the impeller. In order to plan clean-up tool paths rapidly and obtain good finish surface quality, an efficient and robust tool path generation method is presented, which employs an approach based on point-searching. The clean-up machining mentioned in this paper is pencil-cut and multilayer fillet-cut for a free-form model with a ball-end cutter. For pencil-cut, the cutter center position can be determined via judging whether it satisfies the distance requirement. After the searching direction and the tracing direction have been determined, by employing the point-searching algorithm with the idea of dichotomy, all the cutter contact （CC） points and cutter location （CL） points can be found and the clean-up boundaries can also be defined rapidly. Then the tool path is generated. Based on the main concept of pencil-cut, a multilayer fillet-cut method is proposed, which utilizes a ball-end cutter with its radius less than the design radius of clean-up region. Using a sequence of intermediate virtual cutters to divide the clean-up region into several layers and given a cusp-height tolerance for the final layer, then the tool paths for all layers are calculated. Finally, computer implementation is also presented in this paper, and the result shows that the proposed method is feasible.
基金National Natural Science Foundation of China (50805119)Aeronautical Science Foundation of China (2009ZE53)
文摘There are numerous riveting points on the large-sized aircraft panel, irregular row of riveting points on delta wing. It is essential to plan the riveting sequence reasonably to improve the efficiency and accuracy of automatic drilling and riveting. Therefore, this article presents a new multi-objective optimization method based on ant colony optimization （ACO）. Multi-objective optimization model of automatic drilling and riveting sequence planning is built by expressing the efficiency and accuracy of riveting as functions of the points＇ coordinates. In order to search the sequences efficiently and improve the quality of the sequences, a new local pheromone updating rule is applied when the ants search sequences. Pareto dominance is incorporated into the proposed ACO to find out the non-dominated sequences. This method is tested on a hyperbolicity panel model of ARJ21 and the result shows its feasibility and superiority compared with particle swarm optimization （PSO） and genetic algorithm （GA）.
基金The research has been funded by the Swedish Energy Agency,Siemens Industrial Turbomachinery AB and Volvo Aero Corporation through the Swedish research program TURBO POWER,the support of which is gratefully acknowledged.
文摘Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation.A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the threedimensional turning effect and impingement like flow.Improved internal convective cooling is therefore required to increase the blade tip lifetime.In the present study,augmented heat transfer of an internal blade tip with pin-fin arrays has been investigated numerically using a conjugate heat transfer method.The computational domain includes the fluid region and the solid pins as well as the tip regions.Turbulent convective heat transfer between the fluid and pins,and heat conduction within pins and tip are simultaneously computed.The main objective of the present study is to observe the effect of the pin material on heat transfer enhancement of the pin-finned tips.It is found that due to the combination of turning,impingement and pin-fin crossflow,the heat transfer coefficient of a pin-finned tip is a factor of 2.9 higher than that of a smooth tip at the cost of an increased pressure drop by less than 10%.The usage of metal pins can reduce the tip temperature effectively and thereby remove the heat load from the tip.Also,it is found that the tip heat transfer is enhanced even by using insulating pins having low thermal conductivity at low Reynolds numbers.The comparisons of overall performances are also included.
