Simulation of the Effect of Draw Bead on Drawing Process of Panel Header using Altair Hyperform

Transcription

1 Simulation of the Effect of Draw Bead on Drawing Process of Panel Header using Altair Hyperform Desai Ashutosh Valmik PG Student AISSMS COE PUNE Prof. P.V. Deshmukh Asst. Professor, Department of Mechanical Engineering, AISSMS COE, PUNE Keywords- Draw bead, Sheet metal forming, Simulation, Hyperform, Finite element Method Abstract The quality of sheet metal component is secured by the material flow into the die cavity. Draw beads are usually used in sheet metal forming to restrain the sheet from flowing freely into die cavity. In this project, finite element method is used to optimize the location of a draw bead and analysed the strain and thickness variations during the panel header drawing process. In proposed project draw bead is added to the blank holder to reduce the thinning effect of blank caused due to forming process. Altairs HYPERFORM and Radioss solver commercially available for simulation and analyzing the forming process. By using draw bead and other forming parameter such as blank holding force, coefficient of friction etc. tendency of wrinkling reduced. INTRODUCTION The sheet metal forming is a key manufacturing technology of automotive component because of its process flexibility for a quick realization of design shifts at a possible cost. In forming of sheet metal component the forming errors like wrinkling, thinning etc. are commonly observed at the very first tool tryout. In single-stage drawing of sheet metal blank the metal is drawn over various surfaces and varying radii, this makes the prediction of defects complicated. The Finite element simulation of sheet metal forming is increasingly applied to eliminate forming defects, predict and optimize process parameters and to predict stresses / strains in sheet metal blank to prevent blank failure The draw bead consists of a small groove on the die surface or binder surface matched by protrusion on the binder surface or die surface. After the binder closure, the sheet metal is drawn over the draw bead and is subjected to a bending and due to groove material flow is trapped. As draw bead controls the flow of material during forming process, so designing draw bead desired result can easily obtained With the superior awareness of FEM into the drawing process, potential problems in the process tooling and die try-out phases may be eliminated in the virtual environment, and both the costs and lead-times can be considerably reduced. The most used numerical method for numerical simulation of the forming process is finite elements method (FEM). The numerical simulations involved the estimation of the effect of numerous factors on the production process, the analysis of various test geometry, as well as the evaluation of loads, in this study Altairs HYPERFORM and Radioss solver used for virtual simulation. Methodology The thinning error in Panel lower plenum is eliminated by means of FEM simulations. For FEM simulations CAD model, specification of Panel header required. Specification of panel header as given below. 1

2 Specification of component: 1) Material D513 2) Yield strength (YS) 240 Mpa 3) Ultimate tensile strength (UTS) 279.7Mpa 4) Thickness 0.6mm 5) Poisson's ratio-0.3 6) K value (Strength coefficient) Mpa Modelling of panel header was done in CATIA V5R21 as per component specification and IGS provided by R&D department of the industry as shown in fig 1 Numerical simulation Fig.1 CAD model of Panel Header Numerical simulations were carried out for the given conditions and results were obtained.simulation is carried out using incremental Radioss platform in Altairs Hyperform software package.to achieve the less than 20% thinning several iterations are carried out with variable draw bead dimensions. The basic steps for conducting a representative FE simulation of a sheet metal forming process including formability are given schematically in fig. 2 and outlined as follows. Fig.2 FE simulation of sheet metal forming process 2

3 In numerical simulation, contact is necessary between the sliding bodies for the metal forming process, the die was treated as master surface and others were treated as slave surfaces. The static coefficient of friction between the contacts was taken as The velocity of 5000mm/sec was given to the punch in z direction downwards with stroke distance of 60 mm. Initially binder force was set as 40tons in z direction. The component to be formed is taken into HyperForm as an IGES data then using the available commends in HyperForm a mesh was created for blank and die, for creating the mesh for other parts like punch, binder automatic tool build option was used.blank mesh element size was based on thickness of blank in this case blank thickness is 0.6mm so minimum element size taken as 1mm. And for meshing of die, R-type mesh, with minimum and maximum edge length 0.5 and 3mm respectively used, also chordal deviation 0.1 and fillet angle 4 is considered. Draw Bead Design The positioning of the draw beads is crucial to their effectiveness. They should be close to the area requiring restraint and perpendicular to the flow of material. The draw bead is positioned at various locations over the binder surface from the die cavity. Fig.3 shows the various draw bead radius which used in simulation. Here R2 and R2 is entry side radius and exit radius, whereas R1 is responsible for height of bead. These radius varied according to previous iteration results. To obtain desired results various draw bead design and iterations carried out before finalizing die design. Fig.3 Draw bead Circular draw bead which has height 6mm, entry side and exit radius varies between 4mm to 5.5mm also R1 fluctuate in between 3mm to 6mm and numerical simulation was carried out. Effective strain, Von-mises stress, maximum and minimum thickness were identified. Improvement by Simulation For simulation first of all, tool setup generation is required, the exact tool setup used for simulation. Blank holder also known as binder incorporated for holing the edges of sheet metal blank in place against the top of the die while punch forces the sheet metal into the die cavity. In trials, various draw bead design are changed and radius R1 approximately define height of bead varied from 3mm to 6mm for material flow control. Radius R2 increased if there is more thinning takes place similarly while in case of wrinkling one of the radius keep on decreasing upto material thickness. Prediction of fracture, wrinkling is studied from results obtained from solver and viewed in Altair s Hyperview, some of iteration results are shown in Fig. 4 3

4 Large compression zone Fig.4 Iteration 1 st As fig 4 shows first simulation results, without draw bead there is safe thinning occurred but component not formed as expected, it shows wrinkling tendency and insufficient stretching. So to overcome this problem circular type draw bead used over rectangular because by using rectangular draw bead, there is more fluctuation observed in thickness of blank [1]. In next some iteration braw bead is incorporated to avoid these defects. Fig.5 Iteration 11 Th Fig.4 show the thinning result after inserting and gradually modifying the draw bead, still there is more than 20% thinning observed which is not desired. These % thinning and FLD plot results are extremely useful and accurate for prediction of failure, wrinkling and surface defects. Failure of blank can be shown in FLD plot with locations of occurrence, Fig.6 show the failure of blank and its location. 4

5 Failure Fig.6 Iteration 15 th As location known, by changing the dimensions of draw bead the flow material controlled and successive defects are controlled i.e. thinning and wrinkling. For avoid excessive thinning entry side radius of draw bead gradually increases while to overcome wrinkling tendency entry side radius decreased, this radius can be decreased up to thickness of blank. Result and discussion After simulation of multiple trails of possible draw bead design for panel header forming process in single-stage manager of HyperForm using Incremental Radioss as solver, final trail result are shown in fig.7 Maximum % Thining (15% %) Fig.7 Final Results 5

6 As fig.7 shows, maximum thinning of component observed is % which is under desired value i.e. less than 20% and FLD plot shows that there is no tendency of wrinkling and probable failure. After finalizing simulation process actual manufacturing of component carried out and final draw part is confirming the results up to simulation result with ±5% thinning error. Fig.8 Actual Part The details of the thickness measured at 10 locations are given in Table for experimental and numerical studies. As in maximum thinning area in both result are same, in simulation it varied between 15% % while in experimental results diverse between 13%-17% of thinning. Table I Comparison of Thickness Distribution SR NO Experimental Simulation Benefits Summary There were many benefits from the simulation carried out. Many concepts were created based on the simulation study; Saves prototype build-up cost, testing time and cost It reduces the time required to arrive at the final design, thus shortening the product design cycle. Failure and defect easily detected without any actual tool manufacturing Challenges Reducing Design Cycle Time, More Reliable & Quality Products, Improved Decision making 6

7 Conclusions This paper presents finite element based simulation techniques for optimize the position of a draw bead and investigated the strain and thickness variations during the panel header drawing process. A number of iterations were performed in CAE world before concluding the final design. This significantly replaced the proto part making and testing cost and time. This study shows that if thinning occurred at particular area of component increasing entry side radius of draw bead will result into reducing thinning effect, similarly wrinkling tendency avoid by decreasing entry side radius. ACKNOWLEDGEMENTS The authors would like to thank Mr. Kunal Jadhav from Mungi Engineering, Nashik for providing guidance in research activities. Also authors thankful to Management of AISSMS COE, Pune for constant motivation and support. REFERENCES 1. Kopanathi Gowtham, K.V.N.S. Srikanth, Simulation of the Effect of Die Radius on Deep Drawing Process, International Journal of Applied Research in Mechanical Engineering (IJARME) ISSN: , Volume-2, Issue-1, Qiang Liu, Wenjuan Liu, Parameters automated optimization in sheet metal forming process, South China University of Technology Journal of Materials Processing Technology, (2007) Guangyong Sun, Guangyao Li, Multiobjective robust optimization method for drawbead design in sheet metal forming, G. Sun et al. / Materials and Design 31 (2010) Chandra Pal Singh, Geeta Agnihotri, Study of Deep Drawing Process Parameters: A Review, International Journal of Scientific and Research Publications, Volume 5, Issue 2, February 2015, ISSN , Gasˇper Gantar*, Tomazˇ Pepelnjak, Optimization of sheet metal forming processes by the use of numerical simulations, Journal of Materials Processing Technology (2002) M. Samuel, Influence of drawbead geometry on sheet metal forming, Journal of Materials Processing Technology 122 (2002)