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R&D at Center for Precision Forming- CPF

R&D at Center for Precision Forming- CPF. Engineering Research Center for Net Shape Manufacturing (ERC/NSM) www.ercnsm.org Center for Precision Forming (CPF) www.cpforming.org Taylan Altan , PhD, Professor Emeritus The Ohio State University Columbus, OH July 2013.

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R&D at Center for Precision Forming- CPF

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  1. R&D at Center for Precision Forming- CPF Engineering Research Center for Net Shape Manufacturing (ERC/NSM)www.ercnsm.org Center for Precision Forming (CPF)www.cpforming.org TaylanAltan, PhD, Professor Emeritus The Ohio State University Columbus, OH July 2013

  2. Center for Precision Forming - CPF CPF is supported by NSF and 16 member companies, interested in metal forming.

  3. CPF – Current Projects • Material Characterization • Friction / Lubrication • Process Simulation / Forming Al & AHSS-Software: • DEFORM-forging, PAMSTAMP/LS-DYNA-stamping • Die Wear in Forming AHSS • Edge Quality in Blanking / Shearing • Hot Stamping of UHSS • Servo Drive Presses and Hydraulic Cushions • Project experiments are conducted in cooperation with CPF members 3

  4. Material Characterization Viscous Pressure Bulge (VPB) Test 4

  5. Material Characterization – Flow Stress Viscous Pressure Bulge (VPB) Test

  6. Material Characterization – VPB Test Test sample After bursting Before bursting 6

  7. Material Characterization – VPB Test 7

  8. Determination of Sheet Formability Using VPB Test Graph shows dome height comparison for SS 304 sheet material from eight different batches/coils [10 samples per batch]. Highest formability  G , Most consistent  F Lower formability and inconsistent  H 8

  9. Materials Tested with VPB Test at CPF (data available to CPF members) 9

  10. Material Characterization – Dome Test When the blank is well lubricated, it fails at the center of the dome. Dome Test (Frictionless) Necking / fracture moves with increased friction.

  11. Friction/Lubrication – Cup Draw Test Evaluation of Lubricants Performance evaluation criteria (cups drawn to same depth): Higher the Blank Holder Force (BHF) that can be applied without fracture in the drawn cup, better the lubrication condition Smaller the flange perimeter, better the lubrication condition (lower coefficient of friction)

  12. Friction – Cup Draw Test Cup Draw Test Lubrication performance: Shorter Perimeter Higher BHF before fracture 12

  13. Friction / Tribology Temperatures in Cup Draw Test – DP 600 Challenges: 1) Higher contact pressure and higher temperature are detrimental for lubricants, 2) Temperature and pressure additives are needed 13 Ref: Kim et al 2009

  14. Friction / Lubrication Evaluation of Lubricants for Forming Al 5182-0 (1.5 mm)

  15. Forming of Al Alloys in a Servo Drive Press Material draw-in Maximum thinning ~28% Draw depth = 155 mm

  16. Warm Forming of Al, Mg, Ti & SSin an Aida Servo Drive Press AZ31B-O AA5754-O Velocity : 2.5-50mm/sec Cup diameter: 40 mm

  17. Forming of AHSS in a Servopress Forming of AHSS in Servo Press Can we use servo drive properties to improve formability and reduce springback in forming AHSS?

  18. Forming of AHSS Materials of interest: DP 600 DP 980 Maybe others? Forming of AHSS in Servo Press Die design (in progress) for testing AHSS.

  19. Forming of AHSS in a Servopress Forming of AHSS in Servo Press 1) Straight bending, BLANK BLANK BLANK 2) Shrink flanging, BLANK BLANK BLANK 3) Stretch flanging, 4) U-Bending, 5) Curved U-Bending, 6) Deep Drawing.

  20. Forming of AHSS in a Servopress Forming of AHSS in Servo Press Max. Thinning ~ 9% Deep drawn sample DP 600, t0 = 0.83 mm Draw depth = 50 mm

  21. Forming of AHSS Die Wear in Forming of AHSS Currently with DP590In future, Stainless Steel

  22. Blanking/Piercing of AHSS Blanking / Piercing Schematic of piercing Blanked edge (obtained from FE simulations) Burr zone (Zb) Fracture zone (Zf) Shear zone (Zr) vp = punch velocity fb = blank holder force dp = punch diameter dd = die diameter rp = punch corner radius rd = die corner radius db= blank holder diameter t = sheet thickness Punch-die clearance (% of sheet thickness) = (dd-dp)/2t*100 Roll over zone (Zr)

  23. Blanking/Piercing of AHSS Hole Expansion Test Schematic of hole expansion test Before and After Hole Expansion (conical punch)

  24. Blanking/Piercing of AHSS Reduction of strains at blanked surface Conical with flat tip Single shear Conical with spherical tip Humped

  25. Hot Stamping 22MnB5 At ~950°C (1750ºF) Austenite Easier to Form 3-5 min.s in Furnace Quenched in the die >27°C/s (~49°F/s) Less force and springback Mn-B alloyed steel (As delivered) Ferrite-Pearlite Quenched Martensite Ref: Grote 2009, Gutermuth 2011.

  26. Hot Stamping FE Simulation of parts with uniform properties Colors other than gray: Thinning >20%. Part stamped at the participating company

  27. Hot Stamping FE Simulation of cooling channel analysis 1.3 mm roof rail die, After 10 stampings.

  28. Hot Stamping FE Simulation of cooling channel analysis After 10 stampings.

  29. Hot Stamping FE Simulation of parts with tailored properties Hardened zone: 485 – 515 HV 1500 – 1590 MPa (~220 – 230 ksi) Soft zone: 310 – 330 HV 920 – 1020 MPa (~135 – 150 ksi) Literature: [George 2011] , 400°C dies = 790-840 MPa [Feuser 2011], 450°C dies = ~850 MPa

  30. Formability Challenge: This type of fracture cannot be predicted using conventional Forming Limit Curve (FLC). Stretch Bending DP780 Underbody structural part DP980 B-pillar inner 30 Ref: Shi and Chen 2007

  31. New Project: Prediction of Fracture Prediction of fracture/necking from strain or thickness variations (tensile data from Jim Dykeman-Honda HRA)

  32. Multiple Point Control – Hydraulic Cushion Deep Drawing Deep Drawing One solution to this problem is: Optimizing blankholder pressure, including multi-point cushion systems. 32 Ref: Palaniswamy and Altan 2006

  33. Multi-Point Control – Hydraulic Cushion Application of MPC die cushion technology in stamping Sample cushion pin configuration (hydraulic MPC unit) for drawing stainless steel double sink. (Source: Dieffenbacher, Germany) MPC is routinely used in deep drawing of stainless steel sinks 33

  34. Case studies in process simulation Multi-Point Control Systems (MPC) • 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. 34

  35. Questions / Comments? For more information , please contact: Dr. Taylan Altan (altan.1@osu.edu), Ph-614-292-5063 Center for Precision Forming –CPF (www.cpforming.org) 339 Baker Systems,1971 Neil Ave, Columbus, OH-43210 Non-proprietary information can be found at web sites: www.cpforming.org www.ercnsm.org

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