Mfg 01 a_study_on_solid_and_shell_material_model_valeo
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Mfg 01 a_study_on_solid_and_shell_material_model_valeo Mfg 01 a_study_on_solid_and_shell_material_model_valeo Document Transcript

  • A Study on Solid and Shell Material Model in Stamping Simulation Elangovan P Stamping Simulation Engineer Valeo India Private Limited Block - A, 4th Floor, TECCI Park No. 176 Rajiv Gandhi Salai Sozhanganallur Chennai - 600 119, India Keywords: FEA, Sheet Metal forming, Elements, Deep drawing, HyperForm AbstractSheet metal stamping simulation will be carried to predict the part failure during product design stage and some times during processtoo, mainly for stages definitions and optimized blank development. But this study will focus on how solid and shell material model isused in stamping simulation and their impact on results and application. This study will focus on Deep drawing process which will becarried out with Shell and Solid Elements. Active tool elements will be designed for this study. The expected contribution from thisstudy is when and where to use Shell and Solid Elements for the Stamping simulation using HyperForm.IntroductionDeep drawing is a forming process to make cylindrical components. Now, days for all kind of formingprocess up to maximum extent, we can optimize the process using FEA Simulation softwares. This will givean advantage of reduction in product development cost and product development time. FEA Simulationsoftware’s are very helpful for the process people and R&D People. For Blank Optimization, Stagesdefinition and Press tonnage calculation. For R&D, they can work with different materials with different sheetthickness to develop the robust design. In addition to that the marketing people can work on Quotationpurpose based on Blank development and Strip layout. Most of the Sheet metal simulation engineers willwork on Shell Elements because of its lesser sheet thickness and it requires lesser time for simulation.Difference between Shell and Solid ElementsShell Elements are used for lesser thickness and larger displacement problems. For shear strain formingand higher thickness, we need to go for Solid elements. Shell elements can reduce the simulation hours.Element type for Shell is Shell43-Three degrees of freedom in Rotation and Translation and for solid Solid45(Elasto-Plastic Volume Element) which as three degrees of freedom with no degree of freedom in rotation.These element types should be used appropriately for better results.Simulation Driven Innovation 1
  • Process Methodology Figure 1.0: Typical Drawing processA typical drawing process is shown in the fig.1.0 which explains how the drawing operation is performed inreal process. A blank is kept over the die and it is held by Blank holder and Bottom Shedder to control thematerial flow. Punch will travel at a defined velocity to a certain depth. More material flow will leads towrinkling effect this is because of insufficient pressure given by Blank Holder during process. More Blankholder pressure leads to thinning and even cracks. Draw quality steel to be used for this kind of application.For Severe draw Extra Deep draw steel will be used. For, better drawability the r-plastic strain ratio isimportant. r should be (r>1) and Work hardening exponent value should be n>0.20. Figure 1.1: Component drawingSimulation Driven Innovation 2
  • For Shell Modeling Figure 1.3: Shell Elements Simulation ResultsSimulation Driven Innovation 3
  • For Solid ModelingChallengesStamping simulation using shell elements is common through out the industry because of its HyperFormauto process, for using solid elements we did more iterations to run the simulation with the support of Altairpeople (Material model, Number of layers, stamping velocity and contact) etc. Even then we could notcomplete the calculation fully. Figure 1.4: Tool and Blank Design Figure 1.5: Solid Elements Simulation ResultsSimulation Driven Innovation 4
  • Shell element is extruded to 1mm sheet thickness with 5layers by applying type7 contact (surface to nodegroup). For shell element adaptive meshing is available, for solid it is not available. Hence, it is understoodfor solids it will take additional time. Plastic strain- Comparison between Shell and Solid ModelingThe above comparison is shown for progression depth of approximately 11mm. Since, the simulation hoursfor solid elements is too high and even not completed after 20hours. But, for shell elements it has taken just2.5hrs to complete it. The results are plotted in HyperView. Plastic Strains for solids can be viewed inHyperView. Basically, HyperView plots are based on shell elements only. Hence, thinning and fld strainplots are unable to predict. We are working on this to find the alternate solution.Simulation Driven Innovation 5
  • Results & DiscussionsThis study is to understand the difference between the solid and shell elements in stamping simulation. Asper sheet metal theory the failure prediction by Keeler-Goodwin will be based on sheet surface. Hence,based, on Shell element model we can conclude the result. Flc strains are with in the limit. Hence, theprocess is safe. Thinning reduction is around 16.4% which is acceptable. Regarding solid elements we needto check for alternate solution in HyperView or enhance it for solid elements.Benefits SummaryFormability study was carried out for different parameters like Blank holder pressure, Stamping velocity andContact definition the best tryout was explained in this paper. Since the forming process is carried out invirtual environment using the FEA technology we can predict the formability of the component withoutspending money on manual tryouts and corrections.Future PlansEven then, this study is not completed yet. But, we learned how to simulate using solid elements. Furtherstudy is required to improve the solid elements in HyperForm. We are planned to work with Altair to definethe optimized material models, element types and number of layers for solid elements which can enhancethe capability of solid forming by reducing the running hours.ConclusionsFormability study using shell and solid elements is performed in HyperForm. Results of Shell element arepresented. The use and development of Solid-shell finite elements for sheet forming simulation is a growingtopic on Computational Mechanics. We are expecting to work with Altair to define the solid stampingsimulation methodology which will reduce the running hours and as simple as shell autoprocess inHyperForm. ACKNOWLEDGEMENTSI would like to thanks Management of Valeo India Private limited, Chennai for providing Altair’s HyperWorkssoftware and constant motivation. We are also thankful to Mr.Yogesh from Altair India for support andguidance for preparation of the paper. REFERENCES1. Coupling Forming Simulation and Fatigue Life Prediction of Vehicle Components Daniel.B.Dallas, Littleton2. David A. Smith, Die design hand book, Third Edition, SME, 19903. Altair User’s Guide4. IDDRGSimulation Driven Innovation 6