| 0. PrefaceWith the rapid development of China's automotive industry, China has gradually gone into the era of automobile consumption. The quality of auto panels becomes the major focus of Automobile manufacturers. Sheet metal forming CAE analysis technology is an important mean to increase die quality of auto panel and solve automotive production problems. However, as related technologies and software system were monopolized by developed countries, large auto panel dies in China has been dependent on imports, and automotive technology is difficult to have a qualitative leap. Researching on the independent sheet metal forming CAE software system, related lean diagnosis & solving technology for stamping defects and sheet metal forming quality robust control technology, is an important means to shorten the development cycle of new vehicle, improving large auto panel die design & manufacturing technology and automotive manufacturing level. It is a big significance to enhance capability independent innovation of China's equipment manufacturing industry, break through technical barriers in developed countries and market monopoly, ensure to national strategic security and achieve to national long-term technology development plan.In response to the slogan of national "Eleventh Five-Year Plan" outline, in order to improve Chinese automobile manufacture technology and enhance independent innovation capability of China Automotive industry. The research of this paper is supported by the key project of National Automotive Electronic High-tech Industrialization(SDRC high-tech 2040), the key project of National Outstanding Scientific Youth Funds(No.10125208) and the sub-item of"985"project on Automotive Engineering Technology Innovation Platform of Jilin University. The key techniques of lean diagnosis and solving technology for sheet metal forming defects base on CAE, related CAE software systems and robust control methods for stamping quality and forming process based on window were studied in depth.1. The parallel development technology for CAE software based on COMX platformIn order to solve the problem that staff turnover frequently, software code poor universal, lower reuse and slow product development cycle during current independent R&D CAE software. Combine with Universal Formability Theory, the rapid CAE software parallel development technique for lean diagnosis and solving sheet metal forming defects was studied based on COMX component platform. The design patterns of algorithms and user interface separated, develop personalized CAE software based on XML script-driven, and method of establish COMX component were expounded systematically.2. Correction to forming limit diagram and fracture criteria based on linear strain pathIn summing up the shortage of traditional forming limit diagram (FLD), the correction approach for forming limit diagram of sheet metal forming CAE analysis and fracture criterion were proposed based on linear strain path. The special formability analysis method was proposed for special conditions, such as multi-stage forming et al, The safety factor range of FLD of different materials, different forming modes and different conditions were given. Modified FLD software modules and the corresponding fracture criteria algorithm code developed, and they were integrated into the independent R&D sheet metal forming CAE software KMAS. Through making an analysis on front fender drawing process, compared with simulation and test results, it is confirmed that the correction method of FLD and fracture criteria proposed in this paper is both robust and effective.3. Lean diagnosis and solving technology for split on stamping edge considering sheared edge effectAiming at the problem of sheet metal sheared edge fracture appearing before deformation reaches its normal maximum deformation capacity, the mechanism of stamping edge deformation capacity decreasing was studied in view point of the microstructure of shearing and blanking section. The research shows that the deformation capacity of sheared edge is significantly lower produced by work-hardened zone. When the tensile stress acts along the sheared edges, burrs and micro-cracks act as"fracture resources"and expand rapidly, and cause the split on sheared stamping edge.Because stress and strain states of sheared edge stretch being as the same as that of simple tensile test, a modified simple tensile test was proposed. Using the burr height as a reference to quantify the sheared edge effect on stamping edge deformation capacity, the effect law of sheared edge on deformation capacity of sheet metal edge was studied. The test quantitative measure the relationship between burr height and deformation capacity of sheet metal edge, and test results indicate that the deformation capacity of sheet metal edge is decreasing gradually with burr height increasing. The lean diagnosis and solving approach for split on stamping edge was proposed based on test conclusion, and the corresponding defect lean CAE analysis system was developed. The problem that the traditional sheet metal forming CAE software is failed to predict edge fracture accurately was solved, and the precision of method and analysis system proposed in this paper was validated by case study.4. Lean diagnosis and solving technology for surface low stretch defect of auto panelBy researching the dent resistance tests and its influence factors, it is found that both bake-hardening and pre-strain can improve dent resistance capability of sheet metal, and the main reason of surface low stretch defect is less deformation. In order to meet auto panel dent resistance test requirements, the minimum deformation of stamping workpiece should reach to 2%. Because commonly used sheet metal forming CAE analysis software can not analysis specifically surface low stretch defect, a lean diagnosis and solution approach for surface low stretch defect was proposed, and the special analysis software for surface low stretch defect was developed. By diagnosing and solving surface low stretch defect for car door outer and decklid outer panel, it is feasible and effective that the analysis methodology for surface low stretch defect.5. Lean diagnosis and solving technology for surface soft defect of auto panel based on strain gradientBy studying the oil canning load test and its influencing factors, it is found that uneven deformation and low deformation is the main reason to produce surface soft. In order to meet the oil canning load test requirements, the minimum deformation of auto panel should be 2%, and the deformation of stamping area as homogeneous as possible, so well on strain gradient as small. Since the current sheet metal forming CAE analysis software have not special surface defect analysis module, based on strain gradient, propose a technology of lean diagnosis and solving surface soft defect, and develop a special lean analysis software for surface soft defect, the reliability and accuracy of surface soft defect lean analysis approach and software proposed in this paper were validated by case study.6. Sheet metal forming robust control technology based on stamping windowIn order to solve the problem that present sheet metal forming neither quantitatively assess its calculate results nor achieve robust design and robust control for stamping process, propose a robust control approach for stamping process based on window technology, tooling window, materials window and formability window were established respectively. Given feasible range of key stamping variables and material property parameters to produce defect-free workpiece, the key stamping variables including part geometry, die surface, forming process, blank geometry. The intersection of tooling and materials variables is formability window, and make a lean analysis on stamping defects with corresponding low and up limit of key variables in formability window respectively, the feasible field range of formability index for produce high quality and defect-free workpiece is given, to achieve the stamping process robust control.
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