Abstract
The 3-2-1 constraint principle has been widely applied as the boundary conditions for the finite element method (FEM) to simulate machining deformation of aerospace structure components. However, this principle is inconsistent with the actual contact surface between workpieces and worktables because it provides only three constraint points. These points have rarely been studied in terms of positions and distances. In addition, the applicability of the principle is limited for the workpiece with geometric centers difficult to find or centers without nodes. Therefore, this study proposed a new boundary condition method, low-stiffness spring element constraint method (SECM), drawing on FEM theories and related mechanic theories. With the method proposed this study established the FE model of machining deformation, and then compared the simulation results with both the analytical results and the experimental results of milling and deformation measurements. Good agreement is found between the three results. Finally, this study examined the effect of the three constraint points on simulation of the 3-2-1 principle in terms of point positions and distances. A comparison between SECM and the 3-2-1 principle revealed that SECM is closer to the actual working conditions and more reliable with wider application, which suggests that SECM can replace the 3-2-1 principle as the boundary conditions for the workpiece.
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Abbreviations
- B :
-
Geometric matrix
- c :
-
Thickness of each layer
- D :
-
Elastic matrix of the material
- E :
-
Young’s modulus
- F ix :
-
Nodal force
- h :
-
Half width of the element
- I :
-
Inertia moment
- j :
-
Number of layers along the thickness direction
- k :
-
Spring element stiffness
- k rs :
-
Sub-block matrices (r, s = 1, 2, 3, 4)
- K :
-
Total stiffness matrix
- K e :
-
Stiffness matrix of the FE
- I :
-
Half the length of the element
- m :
-
Number of nodes in the X-direction for each row
- M :
-
Equivalent moment per unit width
- n :
-
Number of nodes in the Z-direction for each row
- [P] :
-
Total node load vector
- α :
-
Node displacement vector
- [q] :
-
Total node displacement vector
- R :
-
Radius of the arc ABM1
- σ x0i :
-
Stress function matrix
- t :
-
Thickness of the element
- uj, ur :
-
Displacements of the target and reference position along the X-direction, respectively
- wj, wr :
-
Displacements of the target and the reference position along the Z-direction, respectively
- z :
-
Distance from the point to the neutral plane
- z x0i :
-
Distance from the ith layer to the neutral plane after removing the material
- α :
-
Equal to half of the arc angle corresponding to the arc ABM1
- ε :
-
Strain of the element
- μ :
-
Poisson’s ratio
- σ :
-
Stress of the element
- σ j :
-
Equivalent normal stress at any point on both end faces of the workpiece
- σ x0j :
-
Average stress of each layer
- ξ, η :
-
Dimensionless parameters
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Acknowledgments
The authors thank the referees of this paper for their valuable and very helpful comments.
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: this work was partially supported by Civil Aerospace Technology Pre-research Project, China (B0109), Defense Industrial Technology Development Program, China (JCKY2018601 C002), State Key Laboratory of Virtual Reality Technology Independent Subject, China (BUAA-VR-16ZZ-07), National Science and Technology Major Project, China (2014ZX040 01011), and Beijing Natural Science Foundation, China (3172021).
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He-chuan Song is a Ph.D. of the School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing, China. His research interests include process simulation of aerospace components, simulation and control of machining deformation of thin-walled components, and simulation research on radial-axial large ring rolling technology and residual stress relief.
Yi-du Zhang is a Professor of the School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing, China. He received his Ph.D. in Mechanical Engineering from Beijing University of Aeronautics and Astronautics. His research interests include prediction and control of machining deformation, and dynamics of mechanical system.
Qiong Wu is an Associate Professor of the School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing, China. He received his Ph.D. in Mechanical Engineering from Beijing University of Aeronautics and Astronautics. His research interests include material machining deformation, and the manufacturing and analysis of metal matrix composites.
Han-jun Gao is an Assistant Professor of the School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing, China. He received his Ph.D. in Mechanical Engineering from Beijing University of Aeronautics and Astronautics. His research interests include prediction and control of machining deformation, and performance simulation of aerospace complex mechanical products.
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Song, Hc., Zhang, Yd., Wu, Q. et al. Low-stiffness spring element constraint boundary condition method for machining deformation simulation. J Mech Sci Technol 34, 4117–4128 (2020). https://doi.org/10.1007/s12206-020-0905-x
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DOI: https://doi.org/10.1007/s12206-020-0905-x