7 Seminário de Tecnologias Robtec - Gilmar batalha Poli USP

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7 Seminário de Tecnologias Robtec - Gilmar batalha Poli USP

  1. 1. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 1 New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology G. L. Damoulis – FIAT SpA – Turim - Italy G. F. Batalha – EPUSP – Sao Paulo - Brazil
  2. 2. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 2 Content 1. Introduction 2. Vision 3. Effects whose plays a reasonable role to the process behaviour 4. Industrial Relevance of Springback Research 4.1 Springback Accuracy Prediction 5. Determination of 3D Optical Coordinate Measuring 6. Circular Markers 7. Measurement Procedure 8. Measuring tool try-outs 9. Optical Measurement Analysis in Sheet Metal Forming 9.1 Optical Measurement Analysis 9.2 Optical Measurement Analysis - Forming Limit Diagram (FLD) 10. Industrial Case Example - Measured Data as polygon mesh 10.1 Industrial Case Example – Front Members Rails 10.2 Industrial Case Example – Door outer Panel Skin 11. Conclusions New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 2
  3. 3. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 3 1. Introduction To reach the new market requirement targets for the auto BIW development, process integration since the early concept development phases until the start of production, must provide a streamlined scalable environment that encompasses every step in the process from early design feasibility to the process final validation, that are changing the development chain in the automotive industry:  High safety standards,  High reduction of weight that improves fuel consumption,  Emissions and performance trends;  World class quality at reasonable production costs  Schedule timing. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 3
  4. 4. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 4 2. Vision Regarding automotive lightweight construction based on the use of lightweight materials, meaning that building materials of low specific density and high- strength can be used, automotive engineers and designers are being challenged every day, through the introduction of many new materials for their applications. And for this, new design aims and methodologies should be developed; Auto BIW complains usually complex geometry, irregular pressed parts from many different metallic materials. Forming these blanks is normally a combination of deep drawing and stretching and bending, that can lead afterwards to a springback geometry from the part, making it non useful or refuted depending on or according to the quality standards; To avoid this, a detailed analysis and judging of the forming process with conventional processes requires a lot of energy for most cases. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 4
  5. 5. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 5 3. Effects whose plays a reasonable role to the process behaviour Plastically orthotropy Strain rate dependence of the material Different friction conditions in the contact area sheet-tool and their corresponding friction conditions; Springback. In this sense, the consequent use of the optical measurement techniques enables the saving of try-out time as well as enables improvements in: Quality of the stamping parts; Optimization of the drawing process, Process parameters, Material choice, Blank and forming steps; Springback reduction. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 5
  6. 6. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 6 4. Industrial Relevance of Springback Research  Extensive and time consuming experimental trial and error process;  Necessity of an accurate prediction of the springback phenomenon during whole process modelling to enable tool designers to numerically evaluate the design (through FEM Simulations);  lead-through time from design to production is considerable.  The reason for the long lead through time is that after the first design of the tools and choice of blank material and lubricant, an extensive and time consuming experimental trial and error process has to be started to determine the proper tool design and all other variables  As a result, the lead-through time from design to production can be decreased drastically when the experimental trial and error process can be reliable replaced by a numerical one, while costs are reduced. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 6
  7. 7. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 7 4.1 Springback Accuracy Prediction Accuracy of a springback prediction after a forming operation depends on the accuracy of the stress state. The accuracy of the stress state is influenced by the accuracy of several numerical algorithms:Here the most influences on the stress state would be:  Constitutive equations (Hill, Vegter, Barlat);  Friction and contact behaviour (Coulomb, Stribeck, rigid/deformable tools);  Integration schemes (number of integration points through the thickness);  Mesh dependency (mesh adaptively, mesh size, mesh shape). Improvement of the accuracy of the springback prediction after each forming operation necessitates thorough research on the influence of these aspects on springback predictions. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 7
  8. 8. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 8 5. Determination of 3D Optical Coordinate Measuring The today photogrammetric measuring devices are based upon the principle of triangulation. Multiple images are taken from the desired object using a camera. Knowing the projection equations of the used optical elements, 3D coordinates can be calculated from as many object points as needed. Using photogrammetry, the position of a point in 3D space can be determined by triangulating multiple bundles of observation rays. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 8
  9. 9. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 9 6. Circular Markers  To characterize the image points in the camera image, so called reference targets are used, which are applied onto the object’s surface or the surrounding area.  The following criteria should be taken in consideration for the choice of these markers: High accuracy concerning determination of the position, ability to be identified automatically and easy production and handling. In photogrammetry, typically circular markers are used as they meet these criteria. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 9
  10. 10. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 10 7. Measurement Procedure The six steps of a photogrammetric measurement are:  Applying the non-coded markers at the required measurement positions;  Applying some coded markers;  Positioning of scale length;  Taking images;  Automatic processing of all images and automated calculation of the 3D coordinates of all markers;  Transformation of the results into a distinct coordinate position. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 10
  11. 11. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 11 8. Measuring tool try-outs  Pressed sheet metal parts made with tools manufactured according to the CAD data, in most cases do not comply with the specified data straightaway although the deep drawing processes have been simulated in advance;  Therefore, those tools have to be modified manually (try-out) resulting in the fact that the tools after the try-out process differ from the CAD data models;  Using optical digitizing, modified areas can be identified by means of a nominal/actual comparison. Surface reconstruction of the relevant modified areas provide for updating the CAD to the real shape of the tool;  For simply copying a tool or a modified area, the digitized data, may also be imported as STL data into CAM systems without surface reconstruction. The high accuracy and the data quality of the system allows for direct milling on the polygon meshes with normal finishing work. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 11
  12. 12. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 12 9. Optical Measurement Analysis in Sheet Metal Forming There is a new state-of-the-art in stamping quality control for easy, effective and reliable determination of shape, strains and thinning. Full-field optical vision systems based on the well-known principles of circle grid analysis and photogrammetry provide automated analysis and quantitative colour maps for every square inch of complex parts. The quality results are displayed on a 3D computer model, using the actual measured dimensions of the real part, allowing it to be viewed from any angle. The user can place a cursor at any point on the surface, and a corresponding crosshair shows that same point on the forming limit diagram (FLD); New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 12
  13. 13. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 13 Circular dot pattern electrochemically etched onto the unformed sheet Shaped metal sheet after the forming process with bar-coded markers Thickness reduction along a surface section in the centre of deep drawn cup. 9.1 Optical Measurement Analysis New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 13
  14. 14. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 14 New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 9.2 Optical Measurement Analysis - Forming Limit Diagram (FLD) Forming Limit Diagram (FLD) 14
  15. 15. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 15 New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 9.2 Optical Measurement Analysis - Forming Limit Diagram (FLD) Thickness reduction along a surface section in the centre of deep drawn cup. Forming Limit Diagram (FLD)  As a result, the major and minor strain and the thickness reduction of the sheet metal are available as surface information.  The thickness reduction is directly calculated from the major and minor strain assuming a constant volume 15
  16. 16. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 16 10. Industrial Case Example - Measured Data as polygon mesh New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 16
  17. 17. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 17 10. Industrial Case Example - Measured Data as polygon mesh New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 17
  18. 18. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 18  The figure shows one long member front from one vehicle platform and respective results obtained from a stamping simulation performed using a commercial stamping simulation program.  Normally due crash requirements, this part is produced with materials belonging to the high strength steels family, which not only confers strengths to the part, but also undesirable springback! 10.1a Industrial Case Example – Front Members Rails  Respective results obtained from a stamping simulation performed using a commercial stamping simulation program New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 18
  19. 19. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 19 Simulation Actual stamped part  Long member front from one vehicle platform and respective simulation results obtained from a stamping simulation performed using a standard program.  On a circle evidence, wellness critical paths. 10.1b Industrial Case Example – Front Members Rails New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology
  20. 20. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 20 (a) (b) (d)(c) 10.1c Industrial Case Example – Front Members Rails Performed simulation in 4 modified Geometry model proposals according to the measured results. New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 20
  21. 21. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 21  Confirmation results after optimisation using Optical Measurement Analyze FEM Simulation Optical Measurement 10.1d Industrial Case Example – Front Members Rails New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 21
  22. 22. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 22 10.2a Industrial Case Example – Door outer Panel Skin New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 22
  23. 23. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 23 10.2b Industrial Case Example – Door outer Panel Skin Detail Analyze New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 23
  24. 24. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 24 11. Conclusions  Optical measuring systems for digitizing, forming analysis and material property determination are a part of advanced process chains in the development of products and production processes for sheet metals and tools;  In the future, these measuring technologies will be used increasingly for automated inspection tasks due to their further integration in processes and the availability of powerful data processing systems;  Hence, the measurement of limited areas can be performed in minutes, and uniquely, entire parts can be fully documented for quality control purposes; Comparing the obtained results in a simulation with the true values founded in a tryout stamped part measured through optical systems, this bring us true values that can be overlapped in a cross-section analysis, supplying to the stamping method plan analysts and die designers more reliable information in order that they can better figure out different solutions and local geometry improvements or compensations; New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 24
  25. 25. 28/08/2009 G. F. Batalha & G. L. Damoulis & E. Gomes 25 New trends in sheet metal forming analysis and optimization trough the use of optical measurement technology 25 Thanks for your attention ! gdamoulis@uol.com.br gilmar.batalha@poli.usp.br http://www.poli.usp.br/pmr/lefa

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