Papers by Author: Yuan Li

Abstract: Assembly design and simulation plays a very important role among all stages of product design, and is the fundamental guarantee to improve the assembly performance of product. However, in current assembly design and simulation process, the detailed assembly path and the assembly position and orientation of parts are all needed to be defined through human-computer interaction. Especially when a product contains quantities of parts, there will be so many human-computer interactions to do, which can greatly increase the burden of designers. For this reason, the purpose of this paper is to study an automatic assembly method to reduce the complexity in the definition of assembly design and simulation. Firstly, we studied the intrinsic relationship between the Assembly Feature Pair (AFP) and assembly behaviors of a part, and it’s our belief that the AFP pattern of one part determines its assembly behaviors. And then we proposed an automatic product assembly method based on AFP, by which one only need to enter or specify certain parameters to achieve the assembly design and simulation of a part. Finally, a simple toolset developed based on CATIA and DELMIA using this method was introduced, and an example was given to verify the validity of this approach.

Abstract: Fixtures, tools, and other assembly resources have an important role in the assembly of complex products, so it is very necessary to consider the interactive relationship between the resources model and the product model for assembly order planning in 3D environment. Firstly, the features of assembly process planning involved resources are analyzed. Secondly, the concept of the assembly process intention（AsmPI） is introduced，and an assembly process can be divided into an AsmPI sequence. Thirdly, based on the graph theory, a resource-involved assembly process model is built up. At last, setting a typical structure as an example, the validity of this modeling method is verified.

Abstract: This paper aims to investigate the cell layout problem of aircraft assembly system. A mathematical model for this problem is proposed, taking into account the integration design of cell layout and logistics network. The means of logistics transportation are divided into horizontal transportation and space transportation, meanwhile, the logistics transportation route is calculated. Based on sequence pair, the presentation of solution structure for cell layout is put forward, and the solution structure is solved using simulated annealing algorithm. This method is applied successfully to the assembly cell layout of the fuselage-wing assembly system for a giant aircraft, and the result shows its feasibility and effectiveness.

Abstract: The assembly variation of Aeronautical Thin Walled Structure (ATWS) with automated riveting is inevitable. The deformations of drilling, riveting and releasing are ralated to the final assembly variation. This paper represents a new method for deformation analysis of ATWS with automated riveting. Drilling deformation is modeled by the relationship among deflexion, strain and stress, riveting deformation is modeled by uilibrium equation, and releseaing deformation is modeled by releasing force. The comparison between computing result and expriment proves that the purposed deformation analysis method can solve the problem for ATWS automated riveting efficiently.

Abstract: CFRP/AL stacks are widely used in modern aircraft manufacturing industry. Thrust force is the most important element which will cause delamination in the drilling of stack. This paper developed a thrust force dynamic analysis model for drilling of CFRP/AL stack, by firstly, representing the drilling process into a five-stage model. Secondly, the dynamic thrust force is decomposed into two parts (sub models for CFRP and AL drilling). Thirdly, the thrust force components on both tool major cutting edge and chisel edge is developed according to the analysis on infinitesimal cutting unit in both sub models for CFRP and AL drilling. Lastly, several experiments are performed to compare the result of thrust force analysis, which proves that the purposed model can analyze the dynamic thrust force in drilling of CFRP well.

Abstract: Automatic drilling and riveting process, in order to improve the quality of drilling and riveting aircraft panel deformation are needed for compensation. Due to panels in automatic drilling and riveting process with more posture, therefore, solving panel deformation of plates under more posture is important. This paper establishes aircraft panel in the automatic drilling riveting process multiple posture deformation model. Firstly, simplify the manner of support, locate and clamping between the panel and the splints, supportive of integral panel at each location are calculated using three-moment theory to provide data reference for spacing between splints. Then, deformation results are calculated using flat shell theory to provide data reference for error compensation in automated riveting system, thus, drilling and riveting quality are improved.

Abstract: Interference-fit is the main joint mode of the aircraft composite components, however, improper interference-fit percentage will lead to the onset and the expanding of the damage around the hole. Currently, the interference-fit percentage is decided only through experience, and theoretical foundation is lacked. This paper first analyzes the stress condition of the interference-fit joining process, and constructed the stress distribution model based on interference-fit percentage. Based on this, damage onset model is constructed combined with the Yamada criterion, and the damage expanding model is constructed with the help of the Characteristic curve method; Secondly ABAQUS is used to simulate the interference-fit joining process; Finally contrast is made between the numerical and experimental of joints with different diameters, and the result of the contrast shows that the damage region onset and expanding model and the degeneration model are good.

Abstract: Thrust force is the most important element which will cause delamination in the drilling of CFRP. This paper developed a dynamic thrust force prediction model for CFRP drilling, by firstly, representing the drilling process into a three-step model. Secondly, the dynamic thrust force is decomposed into two parts. Thirdly, the thrust force components on both tool major cutting edge and chisel edge is developed according to the analysis on infinitesimal cutting unit. Lastly, several experiments are performed to compare the result of thrust force analyzed, which proves that the purposed model can analyze the dynamic thrust force in drilling of CFRP well.

Abstract: Beginning with the disassembly of the semi-finished modules, the general assembly process of satellites is quite different from that of other mechanical products. This kind of disassembly-reassembly process cannot be solved by the widely used cut-set theory that only deals with linear problems, thus an approach called Dynamic Transition Graph (DTG) is proposed to solve this nonlinear assembly sequence planning problem. By analyzing and verifying possible assembly statuses hierarchically through matrix operations, a DTG is produced on the basis of Liaison Graph, where the DTG includes all the geometric feasible assembly sequences for the general assembly of satellite. Finally, the effectiveness of this method is verified by an example.

Abstract: Aero Thin-Walled Structure (ATWS) is tending to deformed in automated riveting. Fixture plays an important role in enhancing riveting quality of the ATWS assembly process, and an appropriate layout of locating points can decrease the assembly variation substantially. This paper focused on the layout of locating points for ATWS automated riveting, using Genetic Algorithm and Ants Algorithm (GAAA) to minimize the locating points to decrease riveting variation. Firstly, the scheme of locating points is analyzed, and all potential locating points are represented by leveled matrixes. Secondly, on base of the locating point scheme, information of potential locating points is coded as gene, and the configuration of splint is defined as chromosome; the fitness is also defined according to the Key Characteristic Points (KCPs)’ riveting variation. Thirdly, the genetic and ants manipulations are discussed individually, and the two parts are connected by threshold value of the probability for chromosome in the genetic manipulation. Lastly, a case of aircraft wing panel is studied, and the finite element analysis result proves that the purposed optimizing method can solve the layout of locating point for ATWS automated riveting well.