| During the aircraft digitized assembly processes,connection holes are often processed in a stacked state to ensure concentricity of the mounting holes and hole-efficiency. Since the impact of the assembly error and axial drilling forces, there will be a inter-layers gap in the process of laminate to provide a physical space for the growth of burrs. Inter-layer burrs will not only reduce the assembly precision and assembly quality, but also prone to fatigue cracking when subject to cyclic loading, thus reducing the fatigue performance of the aircraft structure. To achieve the demand for aircraft digital assembly of high quality and long life, it is very important to control inter-layer burr height during the hole-making of laminate.Compared to other parts, hole-making region of stacked panels has a relatively simple structure with weaker rigidity. In practical engineering applications, the main method of controlling the inter-layer burrs is applying a unidirectional pressing force in the hole making process to reduce the inter-layer gap and inhibit the growth of burrs. At present, the size of pressing force depends on workers’ experience, low clamping force can not reach the purposes of eliminating inter-layer gap and reducing the burrs, while higher clamping force make the work-piece’s deformation too large and reduce the geometric accuracy of hole. Therefore it is necessary to optimize the Clamping force during Aircraft stacked panels hole-making process.At first, this paper summarizes the research and development status of aircraft digital assembly technology and elaborate the study and application of robotic automatic hole-making technology at home and abroad. At the same time analyzes the reasons for the stacked burrs during hole-making and the importance of unidirectional pressing force for eliminating burrs, And introduces a number of domestic and foreign research results on burrs-controlled technology.Then, making theoretical modeling for the process of stacked hole-making based on the theory of elasticity, set forth the basic principles of the pressing force to eliminate stacked gap, then calculate the deflections of laminated panels affected by Pressing force and axial drilling force through the thin plate small deflection theory so as to arrive the minimum clamping force to eliminate stacked gap. Next, use the ABAQUS finite element software to make finite element modeling and simulation for the process of stacked hole-making based on actual process parameters, obtain the optimal clamping force by comparing the simulation results under different clamping force and the results were compared with the theoretical analysis, explaining the causes of error.Finally, use the robotic automation system holes system for experimental platform, do stacked hole-making experiment under different clamping force, analysis and compare the different clamping force’s impact for the inter-layer burrs height to correctness of verify the theoretical analysis and finite element simulation. The results show that:with the increase of the pressing force, the inter-layer burr height decreases firstly and then tend to be stable, the optimum clamping force is about 350N under certain conditions, the inter-layer burrs height can be controlled in less than 0.08mm under optimized clamping force, achieve the requirements of no burr hole-making. |
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