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CPF Center for Precision Forming (CPF) Center for Precision Forming (www.cpforming.org) Taylan Altan, Director ( A short Review.

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Presentation on theme: "CPF Center for Precision Forming (CPF) Center for Precision Forming (www.cpforming.org) Taylan Altan, Director ( A short Review."— Presentation transcript:

1 CPF Center for Precision Forming (CPF) Center for Precision Forming (www.cpforming.org) Taylan Altan, Director ( A short Review July, 2011

2 CPF Center for Precision Forming (CPF) Introduction The Ohio State University (OSU) and have established the Industry/University Cooperative Research Center (I/UCRC) on Precision Forming (CPF) focusing on research needs of metal forming industry. Funding is provided by National Science Foundation (NSF) and member companies. CPF (www.cpforming.org) benefits from research conducted at Engineering Research Center for Net Shape Manufacturing (ERC/NSM –

3 CPF Center for Precision Forming (CPF) Objectives Improve existing metal forming processes/products and develop new innovative processes, tooling and equipment. Conduct projects in close collaboration with industry and transfer the results to the member companies. Train and educate engineers in the fundamentals and practice of metal forming science and technology.

4 CPF Center for Precision Forming (CPF) Current Members Boeing Cincinnati Inc Dienamic Tooling Systems ESI North America EWI Honda Hyundai ESI North America Interlaken Technology Corp. POSCO (Korea) IM Steel Scientific Forming Technologies (SFTC) Corp. IMRA America Metalsa Tyco

5 CPF Center for Precision Forming (CPF) Research and Development in Sheet Metal Forming Center for Precision Forming (CPF) (formerly Engineering Research Center for Net Shape Manufacturing) / The Ohio State University June 1 st 2011, Columbus, Ohio © Copyright Center for Precision Forming (CPF). All Rights Reserved. R & D at The Center for Precision Forming

6 CPF Center for Precision Forming (CPF) R&D in Sheet Metal Forming at CPF 6  CPF Elevated temperature stamping and hydroforming (Mg, Al and alloys)  CPF Control of springback and dimensional tolerances in forming AHSS parts  CPF 2.1 – Determination of room temperature material properties (flow stress, formability, anisotropy) of sheet materials under biaxial conditions  CPF 2.3 – Investigation tribological (friction/lubrication/wear) conditions in forming uncoated and galvanized AHSS  CPF 2.5 – Evaluation of lubricants for improving stamping quality  CPF 4.1 – Practical use of multi-point control (MPC) die cushion technology in production of stamped parts

7 CPF Center for Precision Forming (CPF) R&D in Sheet Metal Forming at CPF 7  CPF 4.2 – Tube hydroforming  CPF 5.1 – Evaluation of bendability of AHSS  CPF 5.2 – Prediction and elimination of edge cracking of AHSS in stretch flanging  CPF 5.3 – Blanking and shearing of sheet metal  CPF 5.5 – Hot stamping of boron steels  CPF 5.6 – Applications of servo drive presses in stamping

8 CPF Center for Precision Forming (CPF) CPF Elevated Temperature Stamping and Hydroforming (Mg, Al And Alloys) Manan Shah Jose L. Gonzalez-Mendez Eren Billur 8

9 CPF Center for Precision Forming (CPF) Warm Forming of Al, Mg, Ti & SS (Cup Diameter: 40 mm) (in cooperation with AIDA) AZ31B-O AA5754-O T(°C)LDR RT T(°C)LDR RT Velocity : mm/sec 9

10 CPF Center for Precision Forming (CPF) Warm Forming of SS 304 (Cup Diameter: 40 mm) (in cooperation with AIDA) 10

11 CPF Center for Precision Forming (CPF) 11 Warm Bulge Test (up to 350C/660F)

12 CPF Center for Precision Forming (CPF) 12 Fluid pressure Sheet Reverse Punch Warm Forming FEA using PAMSTAMP 2G 2009 (in cooperation with GM and Interlaken) Punch stroke= 0 mmPunch stroke= 35 mm Blank Holder Die Blank Holder Die Punch

13 CPF Center for Precision Forming (CPF) 13 Warm Forming FEA and Experiments

14 CPF Center for Precision Forming (CPF) CPF Control of Springback and Dimensional Tolerances in Forming AHSS Parts Nimet Kardes-Sever Yurdaer Demiralp Dr. Changhyok Choi 14

15 CPF Center for Precision Forming (CPF) 15 Springback Load-Unload Tensile Test (in cooperation with EWI)

16 CPF Center for Precision Forming (CPF) 16 Springback in S-Die Test (FEA and Experiments) (in cooperation with EWI and IVF) Material: DP 780, DP 600 thickness: 1 mm, 0.75 mm U-bending without stretching U-bending with stretching U-flanging without stretching U-flanging with stretching S-shape forming with – without stretching

17 CPF Center for Precision Forming (CPF) 17 Springback in S-Die Test (FEA and Experiments) (in cooperation with EWI and IVF) S-shape bending sample on S-shape punch U-bending testU-flanging test Schematic of S-shape punchU-bending sample on S-shape punch U-flanging sample on S-shape punch

18 CPF Center for Precision Forming (CPF) 18 CMM measurements of S-Die Test Samples Calculation of springback for S-Die Test samples: Bending angle under load was measured by camera when possible. When the tool is closed it is not possible to take pictures. Therefore, it was assumed that the specimen geometry under load is determined by tool geometry. Bending angle after unloading was measured by protractor and camera when possible and Coordinate Measurement Machine (CMM). For complex samples, sections before and after springback were compared. Schematic of CMM measurements on a sample

19 CPF Center for Precision Forming (CPF) CPF Determination of Room Temperature Material Properties of Sheet Materials Under Biaxial Conditions Eren Billur Yurdaer Demiralp Nimet Kardes-Sever Ji You Yoon 19

20 CPF Center for Precision Forming (CPF) Sheet Material Properties Viscous Pressure Bulge (VPB) Test (in cooperation with many companies) After Forming Laser Test Sample Viscous Medium Stationary Punch Pressure Transducer Before Forming Downward motion clamps the sheet Continued downward motion forms the bulged sheet 20

21 CPF Center for Precision Forming (CPF) Sheet Material Properties Tensile Test vs. VPB Test  Due to necking, flow stress data from tensile test is limited to low strains.  Bulge test is useful to determine flow stress curve for metal forming applications and FE simulations.  Bulge test is useful to determine the quality (formability) of sheet materials. 21

22 CPF Center for Precision Forming (CPF) Determination of Sheet Formability Using VPB Test Highest formability  G, Most consistent  F Lower formability and inconsistent  H Graph shows dome height comparison for SS 304 sheet material from eight different batches/coils [10 samples per batch]. 22

23 CPF Center for Precision Forming (CPF) Materials Tested with VPB Test at CPF (data available to CPF members) Aluminum and Magnesium Alloys AA 6111 AA 5754-O X626 -T4P AZ31B AZ31B-O Steels St 14DP 780-CR St 1403DP 780-HY AISI 1018 Bare DP 980 Y-type X AKDQBare DP 780 T-Si type 1050GA DP 780 T- AI Type DR 120GA DP 780 Y-type U DDSGA DP 780 Y-type V BH 210 DQS-270F GA-Phosphate coated HSS DQS-270D GA-Phosphate coated DP500 DP 590 DP 600 DP 780 TRIP 780 DP Stainless Steels SS 201 SS 301 SS 304 SS 409 SS 410 (AMS 5504) SS 444 LDX 2101

24 CPF Center for Precision Forming (CPF) CPF Investigation Tribological (Friction/Lubrication/Wear) Conditions in Forming Uncoated and Galvanized AHSS Eren Billur Ryan Patton 24

25 CPF Center for Precision Forming (CPF) Evaluation of Die Materials/Coatings for Galling and Die Wear Using The Strip Drawing and Ironing Test (SDT/SIT) (in cooperation with HONDA ) 25  Higher contact pressure accelerates the tool wear and galling, in stamping AHSS.  Various die materials and coatings are evaluated by SDT and SIT. Strip Drawing Test Galling observed on a die insert Strip Ironing Test

26 CPF Center for Precision Forming (CPF) CPF Evaluation of Lubricants for Improving Stamping Quality Soumya Subramonian Nimet Kardes-Sever Yurdaer Demiralp 26

27 CPF Center for Precision Forming (CPF) Evaluation of Lubricants Using The Cup Drawing Test (CDT) (in cooperation with HONDA and several lubricant companies) Performance evaluation criteria (cups drawn to same depth): i.Higher the Blank Holder Force (BHF) that can be applied without fracture in the drawn cup, better the lubrication condition ii.Smaller the flange perimeter, better the lubrication condition (lower coefficient of friction) 27

28 CPF Center for Precision Forming (CPF) Evaluation of Lubricants Using The Cup Drawing Test (CDT) – Results (in cooperation with HONDA and several lubricant companies) 28 Mill oil+

29 CPF Center for Precision Forming (CPF) CPF Practical Use of Multi- point Control (MPC) Die Cushion Technology in Production of Stamped Parts Dr. Taylan Altan 29

30 CPF Center for Precision Forming (CPF) 30 (Source: IFU, Stuttgart) IFU flexible Blank holder / Binder hydraulic control unit Erie binder unit (hydraulic system) with liftgate tooling inside press Hydraulic systems (Source: USCAR) Case studies in process simulation Multi-point Control systems (MPC)

31 CPF Center for Precision Forming (CPF) 31 MPC is routinely used in deep drawing of stainless steel sinks (Source: Dieffenbacher, Germany) Sample cushion pin configuration (hydraulic MPC unit) for drawing stainless steel double sink. Application of MPC die cushion technology in stamping Case studies in process simulation Multi-point Control systems (MPC)

32 CPF Center for Precision Forming (CPF) 32 Previous work at CPF in Blank Holder/Binder Force (BHF) determination Inputs required FEA Software (PAM-STAMP, LS-DYNA) Software developed at CPF for BHF determination Tool geometry (CAD) Material properties Process conditions Quality control parameters (wrinkling, thinning) No. of cushion cylinders (n) BHF at each cushion pin as function of punch stroke CPF in cooperation with USCAR consortium developed software to program MPC die cushion system in stamping. Methodology for BHF determination (Numerical optimization techniques coupled with FEA) Case studies in process simulation Multi-point Control systems (MPC)

33 CPF Center for Precision Forming (CPF) 33  Use of Multi-point Control (MPC) die-cushion systems helps to control metal flow.  Each cushion pin is individually controlled by a cylinder (hydraulic/ nitrogen gas /servo control). Location of cushion pins/ cylinders in the die  MPC can be used to accommodate variations in sheet properties & assist in forming AHSS. Case studies in process simulation Multi-point Control systems (MPC)

34 CPF Center for Precision Forming (CPF) 34 Estimation of BHF varying in each cushion pin & constant in stroke, using FE simulation coupled with numerical optimization, developed at CPF (OSU). Die Beads Sheet Inner Binder Punch Outer Binder Cushion Pin Geometry : Lift gate inner Material : Aluminum alloy, AA6111-T4 Initial sheet thickness : 1 mm Segmented blank holder [Source: USCAR/OSU] FE model Case studies in process simulation Multi-point Control systems (MPC)

35 CPF Center for Precision Forming (CPF) 35 Pin BHF predicted by FE simulation in individual cushion pins for forming Aluminum alloy (A6111-T4, sheet thickness = 1 mm) Pin locations and numbering Case studies in process simulation Multi-point Control systems (MPC)

36 CPF Center for Precision Forming (CPF) 36 Experimental validation of BHF prediction by FE simulation Aluminum alloy (A6111 – T4, t = 1 mm) Minor wrinkles, no tears Bake Hardened steel (BH210, t = 0.8 mm) No wrinkles, no tears Dual Phase steel (DP600, t = 0.8 mm) No wrinkles, no tears Using a hydraulic MPC system installed in mechanical press, the auto-panel was formed successfully - with three different materials/sheet thicknesses in the same die - by only modifying BHF in individual cushion pins. Case studies in process simulation Multi-point Control systems (MPC)

37 CPF Center for Precision Forming (CPF) CPF Tube Hydroforming Dr. Taylan Altan 37

38 CPF Center for Precision Forming (CPF) CPF Evaluation of Bendability of AHSS Xi Yang Nimet Kardes-Sever Yurdaer Demiralp Dr. Changhyok Choi 38

39 CPF Center for Precision Forming (CPF) 39 Prediction of Springback in V-Die Bending (in cooperation with Cincinnati Inc.) a) Before unloading b) After unloading Calculation of springback for V-die bending samples: Bending angle under load was measured by camera. Bending angle after unloading was measured by protractor and camera.

40 CPF Center for Precision Forming (CPF) 40 Prediction of Springback with FEA and BEND in V-Die Bending (in cooperation with Cincinnati Inc.) Punch V-die Sheet FEABEND Schematic of FE model in DEFORM 2DScreenshot from BEND

41 CPF Center for Precision Forming (CPF) 41 Prediction of Springback With BEND in V-Die Bending (in cooperation with Cincinnati Inc.) The program BEND was developed based on the analytical model to predict the springback in air-bending. (Channel Die or V-Die) Parameters input to the program 1.Material’s properties Strain hardening exponent (n ) Strength coefficient (K ) Initial yield stress (YS ) Young’s modulus (E ) Poisson’s ratio Initial thickness (t 0 ) Sheet width (w 0 ) Friction coefficient (m) 2.Tool Dimensions Punch radius Die radius Die opening

42 CPF Center for Precision Forming (CPF) Stretch Bending Test to Evaluate Formability/Fracture 42 Round and Strip Sample Lock Bead before formingafter forming By changing R d and R p, we can obtain different stress/strain conditions at fracture. Punch diameter: mm

43 CPF Center for Precision Forming (CPF) CPF Prediction and Elimination of Edge Cracking of AHSS in Stretch Flanging Soumya Subramonian 43

44 CPF Center for Precision Forming (CPF) 44 Blanking and Flanging (in cooperation with US Steel and TUM) Hole Expansion Test To investigate the stretch-ability of the finished edges. A conical punch, flat bottom punch or spherical punch can be used. Factors Influencing Hole Expansion Edge quality of the hole The method used to finish the hole (e.g. blanking, reaming, etc.) Punch/die clearance used in blanking Positioning of burr with respect to punch Sheet material

45 CPF Center for Precision Forming (CPF) CPF Blanking and Shearing of Sheet Metal Soumya Subramonian Tingting Mao 45

46 CPF Center for Precision Forming (CPF) 46 Schematics of Blanking and Shearing (FEA and Experiments) (in cooperation with Tyco and Cincinnati Inc.) Blanking Shearing [www.custompartnet.com/wu/sheet-metal-shearing ]

47 CPF Center for Precision Forming (CPF) 47 Blanking and Shearing (FEA and Experiments) Different Zones of Blanked Edge ZfZf ZsZs ZrZr ZfZf ZbZb ZsZs ZrZr Different zones of the blanked edge (a) simulations and (b) experiments Zr: rollover zone Zs: shear zone Zf: fracture/rupture zone Zb: burr (a) (b)

48 CPF Center for Precision Forming (CPF) 48 Blanking and Shearing Critical Parameters Effects of the following parameters on the blanked edge quality and punch load/life are studied: Punch-die clearance Punch/die corner radii Stripper pressure and design Punch end geometry Coefficient of friction Punch misalignment Snap-thru forces / reverse loading Vibration and dynamics Analysis of snap-thru forces during blanking through simulations Snap-thru forces

49 CPF Center for Precision Forming (CPF) CPF Hot Stamping of Boron Steels Eren Billur 49

50 CPF Center for Precision Forming (CPF) 50 Introduction/Hot stamping - Developed for automotive applications in the 80’s - Fast growing and an evolving technology for manufacturing crash resistant, light weight parts with reduced springback Parts manufactured using hot stamping

51 CPF Center for Precision Forming (CPF) 51 Introduction/Technology Overview - Manganese Boron steel (22MnB5) has ferritic pearlitic microstructure in as received condition. - These blanks are heated to austenitisation temperature(~950°C) for 5 minutes. - The heated blanks are formed and quenched in the press at a cooling rate higher than 27K/sec. - Quenching changes the microstructure from austenite to martensite and the final part is hardened and has an ultimate tensile strength of around 1500 MPa.

52 CPF Center for Precision Forming (CPF) 52 Introduction/Direct Hot Stamping Direct hot stamping process

53 CPF Center for Precision Forming (CPF) 53 Partners/Supporters National Science Foundation (NSF) - Supporting CPF/finite element simulations of hot stamping. IMRA, Japan - Data base of references and information in hot stamping. POSCO, South Korea Tooling System Group, USA COSKUNOZ (die maker), Turkey - Providing geometry and experimental data on example hot stamped components (details are proprietary).

54 CPF Center for Precision Forming (CPF) 54 International Co-operation CPF maintains good relationship with several leading research institutes active in Hot Stamping technology Lulea University of Technology, Sweden (Prof. Akerstrom) University of Erlangen-Nuremberg, Germany (Prof. Merklein) Leibniz University, Hannover (Prof. Behrens) University of Padova, Italy (Prof. Bariani) Tech.Univ.Graz,Austria (Prof. Kolleck) Toyohashi University of Technology, Japan (Prof. Mori) Technical University of Munich, Germany (Prof. Hoffman) Dortmund University of Technology, Germany (Prof. Tekkaya)

55 CPF Center for Precision Forming (CPF) 55 FE Simulation of Hot Stamping Status / Update Various companies/research groups are using combination of different FE codes like LS-Dyna, ABAQUS, PAMSTAMP, FORGE, MSC. Marc, AUTOFORM for simulating the entire hot stamping process Our Strategy Use PAMSTAMP and DEFORM 3D to predict -Temperature distribution -Thickness distribution -Metal flow -Elastic tool deflection -Cooling channel optimization Simulate and compare results with example parts a) from literature b) provided by our partner companies

56 CPF Center for Precision Forming (CPF) Case Study-1/ AUDI B-Pillar Section -Bench Mark problem-3 given in Numisheet D section of the part is simulated. -The objective is to predict in the formed part: (a) thickness distribution, (b) hardness distribution, (c) potential defects. 56 Tooling for hot stamping of B-Pillar

57 CPF Center for Precision Forming (CPF) Case Study-1/ AUDI B-Pillar Section 57 Input geometries for simulation Punch Die Blank holder Blank Assembly Reference: Benchmark problem-3, Numisheet 2008

58 CPF Center for Precision Forming (CPF) Case Study-1/ AUDI B-Pillar Section 58 -A critical section of the B-Pillar is chosen for 2-dimensional simulation (DEFORM 2D /Variable mesh density) Initial simulation setup Final simulation setup Top die (75 C) Blank holder(75 C) Punch (75 C) 22 MnB5 Blank (810 C)

59 CPF Center for Precision Forming (CPF) Case study-2/ Cooling Channel Design 59 -For this case study, the geometry used in the case study-2 was chosen. -Heat transfer module available in DEFORM is used for simulation -Different combination of cooling channel configurations and examples from the literature are simulated to achieve uniform cooling and martensite microstructure Temperature distribution at the end of press stroke

60 CPF Center for Precision Forming (CPF) Future plans Develop a simplified and practical procedure to simulate the entire hot stamping process with reasonable accuracy using commercial codes PAMSTAMP, LS-Dyna and DEFORM (predict thinning, defects, hardness) ---Develop a simulation procedure to predict tool and part dimensions during hot pressing and correct the tool surface profile to obtain accurate part dimensions and desired hardness distribution (uniform or variable) ---Estimate residual stresses in the part after hot stamping, quenching and cooling

61 CPF Center for Precision Forming (CPF) CPF Applications of Servo Drive Presses in Stamping Adam Groseclose 61

62 CPF Center for Precision Forming (CPF) Servo-Drive Characteristics 1/2 Precise ram position and velocity control, anywhere in stroke Adjustable stroke length (TDC and BDC) Ram position/ velocity can be synchronized with automatic part transfer In deep drawing, cycle times can be shorter than in mechanical presses Considerable savings in energy Dwell at BDC/ restriking/ vibrating and variable blank holder force (BHF) Max. motor torque available during the entire stroke 62

63 CPF Center for Precision Forming (CPF) The flexibility of slide motion in servo drive (or free motion) presses. [Miyoshi, 2004] Servo-Drive Characteristics 2/2 63

64 CPF Center for Precision Forming (CPF) Servo-Drive Mechanisms Low Torque/ High RPM Motors Use Ball Screws or/and Linkage Mechanisms High Torque/ Low RPM Motors Use Existing Crank and/or Link Press Drives 64

65 CPF Center for Precision Forming (CPF) Low RPM/High Torque Motor Drive 65 a) C-Frame Servo Press (Aida) Power SourceBalancer tank Main gear Servomotor Capacitor Drive Shaft b) Stroke-Time program for warm forming of Al and Mg sheet

66 CPF Center for Precision Forming (CPF) Modern Stamping Lines Using Large Servo-Drive Presses BMW- Leipzig and Regensburg (Germany)/ 2500 ton servo-drive drawing press (Schuler)/ 17 SPM (2009) HONDA- Suzuka (Japan)/ 2500 ton servo-drive drawing press (Aida)/ 18 SPM (2009) New large press lines are planned –BMW-Schuler –HONDA-Aida

67 CPF Center for Precision Forming (CPF) Improved Formability Improved Productivity Energy-Saving ・ System with optimized press forming requirements for each product ・ Press-to-Press Loading Motion: System is optimized for each product. ・ Die cushions have an energy regeneration system Schematic of Servo-press line (Aida/Honda) 2500 ton/ 18 SPM draw press (2009) 67

68 CPF Center for Precision Forming (CPF) 68 Suzuka Plant Production Picture (Honda/Aida)

69 CPF Center for Precision Forming (CPF) Comparison between the slide motions of an 1100 mechanical and servo drive press for identical slide velocity during forming [Bloom, 2008]. Applications- Deep Drawing 1/3 69

70 CPF Center for Precision Forming (CPF) Decrease in cycle time by reducing the stroke length and operating the servo press in “pendular” mode (progressive die stamping, 200% increase in output) [Bloom, 2008] Applications- Deep Drawing 2/3 70

71 CPF Center for Precision Forming (CPF) Decrease in cycle time as well as in impact speed using a servo press (150% increase in output) [Bloom, 2008] Applications- Deep Drawing 3/3 71

72 CPF Center for Precision Forming (CPF) Side Panel Outer Deep Drawing Case Example (Honda/Aida) 72

73 CPF Center for Precision Forming (CPF) High-speed/ High Accuracy Servo-Press (Honda/Aida) 73

74 CPF Center for Precision Forming (CPF) Die CushionForce (kN) Elimination of Pressure Surge in the Die Cushion Servo-Hydraulic Cushion 1/2 (Courtesy-Aida) 74

75 CPF Center for Precision Forming (CPF) Servo-Hydraulic Cushion 2/2 (Courtesy-Aida) During Down Stroke, Cushion Pressure Generates Power 75

76 CPF Center for Precision Forming (CPF) Optimization of Ram Velocity for Deep Drawing with Servo-Drive Presses Objective Develop a methodology to optimize the ram velocity during deep drawing of sheet metal parts with a servo-drive press. New CPF Project- in cooperation with the University of Darmstadt (Germany) 76

77 CPF Center for Precision Forming (CPF) 77  Process simulation using FEA is state of the art for die/process design. Determination of reliable input parameters [material properties /interface friction conditions] is a key element in successful application of process simulation.  Advanced FE simulation + reliable input data helps to predict process parameters for forming the part and save tryout/setup time, cost, material & energy.  Multi-point control (MPC) die -cushion systems offer high flexibility in process control, resulting in considerable improvement in formability. MPC systems offer advantages in forming high strength materials. Summary

78 CPF Center for Precision Forming (CPF) 78 Summary  Warm forming of selected Al- and Mg- alloys shows improvement in formability at temperatures in the range of °C. Reliable flow stress data at elevated temperature is required as an input for accurate FE simulation of the warm forming process. Considerable research on warm forming process and its application to production is in progress.  Hot stamping technology will increase rapidly (Process simulation and die design/manufacturing are major issues).  Electric/Mechanical servo-drive presses will be increasingly used, also in higher tonnages (2,000-4,000 tons).

79 CPF Center for Precision Forming (CPF) 79 Summary/Questions  CPF is supported by the National Science Foundation and 10+ member companies.  With a staff of 20 (post docs, PhD students, MS students), CPF is conducting R&D in metal forming, with emphasis on forming AHSS.  CPF is maintaining close contacts with many other forming research labs, world wide.  For questions, please contact Taylan Altan or Linda Anastasi  For detailed information, please visit and


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