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Chang Z.,Northwestern Polytechnical University | Wang Z.,Northwestern Polytechnical University | Wang B.,Northwestern Polytechnical University | Kang Y.,Northwestern Polytechnical University | Luo Q.,Xian Aircraft Industrial Group Co.
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2016

The riveting force is one of the important parameters to guarantee riveting quality. However, traditional approaches are concentrated on experience or simplified theoretical model and do not consider the impact of formed head inhomogeneous deformation, which brings errors. This paper presents a riveting force computation model to improve the effectiveness where the formed head inhomogeneous deformation is taken into consideration. In this paper, the riveting process is divided into four stages according to the rivet material flow trends, and the maximum riveting force position can be determined. Based on the ultimate stress analysis of thick-walled cylinder compressed into plastic state, the computational model of riveting force is built in the inhomogeneous deformation situation. The model parameter is solved combining with the volume invariant assumption. Finally, 4 mm and 5 mm diameter protruding head rivets are selected to conduct the research. Under the same riveting force, the ABAQUS and G86 drilling and riveting machine are used to finish numerical simulation and riveting experiment respectively. The results show that the difference is less than 5%, comparing the ideal dimension with numerical simulation and experiment. Therefore, the computation model of riveting force has its effectiveness. © 2016, Press of Chinese Journal of Aeronautics. All right reserved.

Zhang Z.,Nanjing University of Aeronautics and Astronautics | Li L.,Nanjing University of Aeronautics and Astronautics | Yang Y.-F.,Nanjing University of Aeronautics and Astronautics | Ma L.-D.,Xian Aircraft Industrial Group Co. | Ma Y.-L.,Xian Aircraft Industrial Group Co.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2014

In order to study the machining distortion of aluminum monolithic structures in the aerospace industry, the internal residual stresses in monolithic die forging beam of aluminum alloy 7050-T74 were measured by using contour method. Electrical discharge machining was performed to cut the cross section of the specimen and the cut surfaces were measured by using laser scanner. The measured contours were fitted by using a 3D cubic spline based algorithm and then applied as an initial displacement boundary condition normal to the cut plane in the FE model but in the opposite direction. A linear elastic finite element analysis was then undertaken to calculate the corresponding distribution of residual stress normal to the cut face. In addition, the hole drilling method was employed to measure the surface residual stress of specimen, and its results were compared with those by the contour method at the same locations. The results indicate that the residual stresses in the specimen can be attributed to the stretch bending craft. The T-shaped cross section residual stress distribution shows a typical bending distribution of compression near the convex zone balanced by tension in the concave zone. Contour method efficiently provides accurate residual stress distribution in the test material. The test error at the edge area can be modified in compliance with surface residual stress measurement techniques. ©, 2014, Central South University of Technology. All right reserved.

Cheng H.,Northwestern Polytechnical University | Li Y.,Northwestern Polytechnical University | Zhang K.-F.,Northwestern Polytechnical University | Mu W.-Q.,Northwestern Polytechnical University | Liu B.-F.,XiAn Aircraft Industrial Group Co.
Journal of Manufacturing Systems | Year: 2011

Assembly variation is inevitable in aeronautical thin-walled structure (ATWS) assembly, especially in structures joined with "C-type" automated riveting system (CARS). The variation propagates along the assembly process flow and will influence final product performance such as dimensional quality and fatigue durability. This paper represents a new variation model of ATWS with multi-state riveting. Firstly, a novel multi-state process of ATWS riveting with CARS called PDJR to PDRR (P to P) is developed and it contains two stages and eight states. Secondly, based on the P to P process, the variation model is divided into three sub-models (feature, displacement and propagation) to represent the assembly variation of ATWS multi-state riveting. For the feature sub-model, three important features are discussed, and the geometric and topological information is represented by a hierarchical method. For the displacement sub-model, the variation of eight-state in P to P is divided into four types, and the displacement of each type is analyzed separately according to the coordinate transformation and finite element method (FEM). For the propagation sub-model, a translation matrix considering the disturbance factor of every state is developed to obtain the final variation. Lastly, a multi-state riveting process of a wing panel which is made up of a skin and four stringers is modeled as a case study. The FEM is integrated into the Monte Carlo simulation (MCS) to analyze the variation, and the result proves that the proposed variation modeling of ATWS multi-state riveting can solve the problem of variation analysis in ATWS multi-state riveting efficiently. © 2011 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

Zhang Z.,Nanjing University of Aeronautics and Astronautics | Yang Y.,Nanjing University of Aeronautics and Astronautics | Li L.,Nanjing University of Aeronautics and Astronautics | Chen B.,Xian Aircraft Industrial Group Co. | Tian H.,Xian Aircraft Industrial Group Co.
Materials Science and Engineering A | Year: 2015

The cold-compression stress relief process has been used to reduce the quench-induced stresses in high-strength aerospace aluminum alloy forgings. However, this method does not completely relieve the stress. Longitudinal residual stresses in 7050-T7452 aluminum alloy forging were measured with contour method. The measuring procedure of the contour method including specimen cutting under clamps with a wire electrical discharge machine, contour measurement of the cut surface with a laser scanner, careful data processing and elastic finite element analysis was introduced in detail. In addition, multiple cuts were used to map cross sectional stress at different cut surfaces. Finally, the longitudinal residual stress throughout the cut plane was mapped, and through thickness longitudinal stress profiles were also analyzed. Investigated results suggest that spatial variation of stress distribution can be attributed to the non-uniform plastic deformation of the cold-compression stress relief process. The overall reduction of peak stress magnitudes is approximately 43-79%. © 2015 Elsevier B.V.

Cheng H.,Northwestern Polytechnical University | Li Y.,Northwestern Polytechnical University | Zhang K.-F.,Northwestern Polytechnical University | Su J.-B.,XiAn Aircraft Industrial Group Co.
International Journal of Advanced Manufacturing Technology | Year: 2011

The riveting process of aeronautical thin-walled structures (ATWS) with "Frame-type" automated riveter systems is always multi-state. The changing of fixtures and datum in riveting process would lead to the difficulty of positioning error analysis, and the positioning error will influence the tolerance characteristics of final product and the fatigue durability. This paper presents an efficient method for positioning error analysis in ATWS multi-state riveting. Firstly, the whole riveting process is divided into two stages according to the changing of riveting fixtures, and the model of positioning error in each stage is developed on base of the mismatch error analysis. Secondly, by defining key characteristic points (KCPs) according to anchor points and joining points, the positioning error of ATWS is represented as the error of KCPs, and the scheme of anchor points and joining points is developed according to the "N-2-1" positioning principle. Thirdly, on base of positioning error propagation analysis in each stage, components of positioning error are discussed in detail, and the mathematical model of each component is developed, according to the manufacturing error, position accuracy as well as the mismatch error. Lastly, a wing panel which is made up of a skin and four stringers is studied as a case to calculate the positioning error. The comparison between computing result and measurement proves that the purposed positioning error analysis method can solve the positioning error analysis problem for ATWS multi-state riveting efficiently. © 2010 Springer-Verlag London Limited.

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