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

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

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

Material Characterization Viscous Pressure Bulge (VPB) Test 4

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

Before burstingAfter bursting Test sample Material Characterization – VPB Test 6

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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]. 8

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 1018Bare 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 DP500DP 780 DP 590TRIP 780 DP 600DP 980 Stainless Steels SS 201 SS 301 SS 304 SS 409 SS 410 (AMS 5504) SS 444 LDX

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

11 Friction/Lubrication – Cup Draw Test Evaluation of Lubricants 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)

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

Friction / Tribology Ref: Kim et al 2009 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

14 Friction / Lubrication Evaluation of Lubricants for Forming Al (1.5 mm)

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

AZ31B-O AA5754-O T(°C)LDR RT T(°C)LDR RT Velocity : mm/sec Cup diameter: 40 mm Warm Forming of Al, Mg, Ti & SS in an Aida Servo Drive Press 16

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, 2) Shrink flanging, BLANK 3) Stretch flanging, BLANK 4) U-Bending, 5) Curved U-Bending, BLANK 6) Deep Drawing.

20 Forming of AHSS in a Servopress Deep drawn sample DP 600, t 0 = 0.83 mm Draw depth = 50 mm Forming of AHSS in Servo Press Max. Thinning ~ 9%

21 Forming of AHSS Die Wear in Forming of AHSS Currently with DP590 In future, Stainless Steel

22 Blanking/Piercing of AHSS Blanking / Piercing Schematic of piercing v p = punch velocityf b = blank holder force d p = punch diameterd d = die diameter r p = punch corner radiusr d = die corner radius d b = blank holder diametert = sheet thickness Punch-die clearance (% of sheet thickness) = (d d -d p )/2t*100 Fracture zone (Z f ) Burr zone (Z b ) Roll over zone (Z r ) Shear zone (Z r ) Blanked edge (obtained from FE simulations)

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 Single shear Conical with flat tip Humped Conical with spherical tip

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

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

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 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 = MPa [Feuser 2011], 450°C dies = ~850 MPa FE Simulation of parts with tailored properties

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

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

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

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 Multi-Point Control – Hydraulic Cushion 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

Questions / Comments? For more information, please contact: Dr. Taylan Altan Center for Precision Forming –CPF ( 339 Baker Systems,1971 Neil Ave, Columbus, OH Non-proprietary information can be found at web sites: