Papers by Author: Lin Gao

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Authors: Yan Xu, Shuang Gao Li, Lin Gao
Abstract: Incremental forming of sheet metal is difficult to be simulated for its complicated 3D loading path. In this work, an acceptable approach to generate 3D loading path, called “virtual guiding model method” is accomplished. The method, which has the similar idea with the conventional copy mill, is based on FEM and the basic principle of kinematics. With the help of the method, multi-stage incremental forming of a drawing typed square cup was simulated in the FEM software-PAMSTAMP and experimented. Through measuring the thickness distribution the vertical edge of the cup, the most difference between them is less than 0.05mm, which is satisfied with engineering request, and the results shows that the 3D loading path generating method is one of the most effective way to realize the incremental forming simulation.
Authors: Ming He Chen, J.H. Li, Lin Gao, Dun Wen Zuo, Min Wang
Abstract: In order to solve the problem existed in the numerical simulation of sheet metal forming for its use the strain-based forming limit diagram as criterion, which has the flaw of dependence on the strain paths, this paper develops the finite element analysis program based on the stress forming limit criterion applicable to the blank plastic forming technique, which follows the stress-strain transformation relationship when the sheet metal is undergoing plastic deformation, chooses Hill’s quadratic normal anisotropic criterion as computational model and selects the commercial finite element code Dynaform as its development environment. Also it be analyzed the finite element numerical simulation results of two deep drawing parts by the developed program module and realizes the prediction of sheet metal forming limit adopting the FLSD as criterion. The stress-based forming limit criterion for the developed program provides a new means to analyze the forming limit for the multistage sheet metal forming.
Authors: Ming He Chen, Lin Gao, H.H. Mao, Dun Wen Zuo, Min Wang
Abstract: In order to improve the forming precision of the stretch bending process for T section aluminum extrusions and meet the fine forming requirement of the aerostat blank parts, the elongation controlled stretch bending process finite element model is proposed, which is based on the basic principle of the stretch bending forming with respect to A-7B CNC Section Stretch Wrap Forming Machine by analyzing various factors that influence the qualities of stretch bending parts, and the numerical simulation of the stretch bending process and spring back for T section aluminum extrusions is carried out. The results of simulation show that the pre-stretching elongation has a major effect on stretch bending parts and finite post-stretching elongation helps to improve the forming qualities of the parts. Comparing with the experimental results, the spring back of the finite element simulation shows good agreement with that of the experimental results.
Authors: Ming He Chen, Lin Gao, Z.S. Zhu, Dun Wen Zuo, Min Wang
Abstract: The calescent superplastic bulge forming (CSPBF) of Ti-6Al-4V (TC4) alloy sheet was investigated using experimental method, and carried out the research that optimized its technological parameters using fuzzy neural network (FNN) . The experimental results show that the CSPBF may save processing time, can also improve materials’ formability as well as get ideal microstructure. The study indicated that the FNN adapt to solve complex nonlinear problem such as technological parameters of CSPBF of TC4 sheet. Utilizing optimized technological parameters successfully have formed the part of aerostat, the nonuniformity of wall thickness is less than 8% and part' forming time may be shorten 10minute.
Authors: Ghulam Hussain, Nasir Hayat, Lin Gao
Abstract: Single point incremental forming (SPIF) is a novel sheet metal forming process. Owing to unique deformation mechanism, this process improves the sheet formability as compared to the conventional stamping process. In the current paper, the mechanical properties and spifability (i.e. formability in SPIF) of a wide range of materials were tested. The mechanical properties were mainly determined through tensile testing and the spifability was evaluated using Varying Wall Angle Conical Frustum (VWACF) test. Each mechanical property was drawn against the improvement in sheet formability (i.e. difference of spifability and stampability) and the sole most influential property was identified. It was found that the improvement in formability increases with the increasing of true thickness strain at tensile fracture.
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