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A Discrete Springback Compensation Algorithm for Stampings with Curved Surfaces Using Optical Measuring Technology

Author: LiaoJuan
Tutor: RuanFeng
School: South China University of Technology
Course: Mechanical Manufacturing and Automation
Keywords: Optical measurement Surface stampings Springback compensation Curvature Strain Discrete
CLC: TG386
Type: PhD thesis
Year: 2011
Downloads: 117
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Abstract

In sheet metal forming field, rebound phenomenon is inevitable in the forming process, it is the presence of a direct impact on the forming precision stampings. With the development of the automotive and aerospace industries, forming part of the three-dimensional surface accuracy have become increasingly demanding, especially in recent years due to the extensive use of high-strength steel, springback problems are more prominent. Although the rebound can be reduced to some extent by improving the stamping process, but can not fundamentally eliminate the rebound. Mold compensation theory can completely eliminate the shape of the error caused by the rebound, but how to get the right compensation surface problem is that the technology is not yet resolved. Currently most of the methods used by iterative application of CAE technology mold the final compensation surface CAE technology can not accurately predict springback of stamping parts, especially for some of the more complex surfaces stampings, so this way the mold compensated surface is difficult to ensure its accuracy, repeatedly tryout is still inevitable. For this reason, this paper, based on the study of modern optical measurement techniques curved stampings rebound in the Discrete compensation algorithm in order to obtain the correct surface mold compensation, and effectively solve the problem of sheet metal stamping springback. The main research work done in this article are as follows: a two-dimensional variable parts of the curvature of the cross-sectional shape of the rebound, measurement-based compensation algorithm of discrete curvature correction. The algorithm will be non-rules complex parts of the cross-section of discrete tiny etc. curvature segment. For each, etc. curvature segment curvature compensation algorithm, and the actual measurement of the curvature springback correction, anti-calculated the mold surface compensation curvature; Finally, the surface curve theory of differential geometry-based surface reconstruction algorithm automatically create compensating mold surface, then the next time stamping. The algorithm has been successfully applied to the the springback problem processing wavy parts and leaf parts, the experimental results show that the compensation method through a repair mode can be obtained ideal stampings. Springback problems of the three-dimensional surface stampings discrete way into multiple small double curvature piece separate rebound and its interaction problems. First, create a part springback prediction model based on the measurement of double curvature. The theoretical analysis for the typical three-dimensional double curvature parts directly based on optical measurements obtained double curvature parts forming strain before unloading parts neutral layer offset bridges, to establish a double curvature parts of different stress-strain state moment and membrane force model, which predicted rebound, laid the theoretical foundation for the subsequent compensation algorithm. According to the theoretical model, the paper discusses the film force, material parameters and mold surface curvature parameters of double curvature parts rebound. Second, the double curvature parts of the drawing rebound test research. Two optical measurement system used in the experiment were given parts forming strain data before uninstall and shaped surface point cloud data. Rebound control for the measurement data, an evaluation method based on the curvature of the curved stampings rebound, can objectively reflect stampings area rebound. Double curvature parts of springback law and strain distribution pattern analysis in conjunction with the evaluation method; material and process parameters on the parts rebound, theoretical model to predict the results of a comparative analysis of the experimental results verify the above back bomb the correctness of the prediction model. Finally, a combination of the above based on the measurement of double curvature parts springback prediction model and evaluation system, the the discrete surfaces stampings compensation algorithm. The method stampings surface discrete plurality of quadrilateral facets, surface patches enough hours, each surface approximation seen as the the double curvature chip a double curvature surface patches, three-dimensional surface stampings rebound into each separate rebound and its interaction problems. The single double curvature film using the theoretical model based on the measurement of the rebound, looking for the mold surface curvature incremental neutral layer offset incremental build the the moment film force changes between the two stamping process, anti-calculated single the surface patches compensation curvature; mutual influence between the surface patches by actual stampings rebound to correct curvature release the scale factor of the curvature of the theoretical calculation of the compensation; final discrete principal curvatures of the surface of the mold by compensation matrix reconstruct the next stamping the desired mold surface. The algorithm has been successfully applied to the double curvature parts mold surface modification experiments, the experimental results show that the algorithm is effective and feasible.

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