1. Center for Precision Forming(
Taylan Altan, Director (
A short Review
July, 2011

2. 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 ( benefits from research conducted at Engineering Research Center for Net Shape Manufacturing (ERC/NSM –

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

5. Research and Development in Sheet Metal Forming
R & D at The Center for Precision Forming
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 1st 2011, Columbus, Ohio
© Copyright Center for Precision Forming (CPF). All Rights Reserved.

6. R&D in Sheet Metal Forming at CPF
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. R&D in Sheet Metal Forming at CPF
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. Manan Shah Jose L. Gonzalez-Mendez Eren Billur
CPF Elevated Temperature Stamping and Hydroforming (Mg, Al And Alloys)
Manan Shah
Jose L. Gonzalez-Mendez
Eren Billur

9. Al, Mg, Ti & SS (Cup Diameter: 40 mm) (in cooperation with AIDA)
Warm Forming of
Al, Mg, Ti & SS (Cup Diameter: 40 mm)
(in cooperation with AIDA)
AZ31B-O
AA5754-O
T(°C)
LDR RT
2.1
250
2.5
300
2.9
T(°C)
LDR RT -
275
2.6
3.2
Velocity : mm/sec

10. (in cooperation with AIDA)
Warm Forming of
SS 304 (Cup Diameter: 40 mm)
(in cooperation with AIDA)

11. Warm Bulge Test
(up to 350C/660F)

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

13. Warm Forming
FEA and Experiments

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

15. Load-Unload Tensile Test (in cooperation with EWI)
Springback
Load-Unload Tensile Test
(in cooperation with EWI)

16. (in cooperation with EWI and IVF)
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-flanging without stretching
U-bending without stretching
U-flanging with stretching
U-bending with stretching
S-shape forming with – without stretching

17. (in cooperation with EWI and IVF)
Springback in S-Die Test (FEA and Experiments)
(in cooperation with EWI and IVF)
U-flanging test
U-bending test
Schematic of S-shape punch
U-bending sample on S-shape punch
U-flanging sample on S-shape punch
S-shape bending sample on S-shape punch

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. Eren Billur Yurdaer Demiralp Nimet Kardes-Sever Ji You Yoon
CPF Determination of Room Temperature Material Properties of Sheet Materials Under Biaxial Conditions
Eren Billur
Yurdaer Demiralp
Nimet Kardes-Sever
Ji You Yoon

20. 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

21. 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.

22. 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

23. Materials Tested with VPB Test at CPF
(data available to CPF members)
Steels
St 14
DP 780-CR
St 1403
DP 780-HY
AISI 1018
Bare DP 980 Y-type X
AKDQ
Bare DP 780 T-Si type
1050
GA DP 780 T- AI Type
DR 120
GA DP 780 Y-type U
DDS
GA 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 980
Aluminum and Magnesium Alloys
AA 6111
AA 5754-O
X626 -T4P
AZ31B
AZ31B-O
Stainless Steels
SS 201
SS 301
SS 304
SS 409
SS 410 (AMS 5504)
SS 444
LDX 2101

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

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

26. CPF 2.5 - Evaluation of Lubricants for Improving Stamping Quality
Soumya Subramonian
Nimet Kardes-Sever
Yurdaer Demiralp

27. 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):
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)

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

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

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

31. Application of MPC die cushion technology in stamping
Case studies in process simulation
Multi-point Control systems (MPC)
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

32. Case studies in process simulation
Multi-point Control systems (MPC)
Previous work at CPF in Blank Holder/Binder Force (BHF) determination
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)
Inputs required
BHF at each cushion pin as function of punch stroke
Software developed at CPF for BHF determination
Quality control parameters (wrinkling, thinning)
No. of cushion cylinders (n)
Tool geometry (CAD)
Material properties
Process conditions
FEA Software
(PAM-STAMP, LS-DYNA)

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

35. Multi-point Control systems (MPC)
Case studies in process simulation
Multi-point Control systems (MPC)
BHF predicted by FE simulation in individual cushion pins for forming Aluminum alloy (A6111-T4, sheet thickness = 1 mm)
Pin 1 2 3 4 6 5 7 8 9 10 11 14 12 13 15
Pin locations and numbering

36. Experimental validation of BHF prediction by FE simulation
Case studies in process simulation
Multi-point Control systems (MPC)
Experimental validation of BHF prediction by FE simulation
Bake Hardened steel (BH210, t = 0.8 mm)
No wrinkles, no tears
Aluminum alloy (A6111 – T4, t = 1 mm)
Minor 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.

37. CPF 4.2 - Tube Hydroforming
Dr. Taylan Altan

38. CPF 5.1 - Evaluation of Bendability of AHSS
Xi Yang
Nimet Kardes-Sever
Yurdaer Demiralp
Dr. Changhyok Choi

39. Prediction of Springback (in cooperation with Cincinnati Inc.)
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. Prediction of Springback with FEA and BEND in V-Die Bending
(in cooperation with Cincinnati Inc.)
FEA
BEND
Punch
Sheet
V-die
Schematic of FE model in DEFORM 2D
Screenshot from BEND

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
Material’s properties
Strain hardening exponent (n )
Strength coefficient (K )
Initial yield stress (YS )
Young’s modulus (E )
Poisson’s ratio
Initial thickness (t0)
Sheet width (w0)
Friction coefficient (m)
Tool Dimensions
Punch radius
Die radius
Die opening

42. to Evaluate Formability/Fracture
Stretch Bending Test
to Evaluate Formability/Fracture
Punch diameter: mm
Lock Bead
Round and Strip Sample
before forming
after forming
By changing Rd and Rp, we can obtain different stress/strain conditions at fracture.

43. CPF 5.2 - Prediction and Elimination of Edge Cracking of AHSS in Stretch Flanging
Soumya Subramonian

44. (in cooperation with US Steel and TUM)
Blanking and Flanging
(in cooperation with US Steel and TUM)
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
Hole Expansion Test
• To investigate the stretch-ability of the finished edges.
• A conical punch, flat bottom punch or spherical punch can be used.

45. CPF 5.3 - Blanking and Shearing of Sheet Metal
Soumya Subramonian
Tingting Mao

46. Schematics of Blanking and Shearing (FEA and Experiments)
(in cooperation with Tyco and Cincinnati Inc.)
Shearing
Blanking
[ ]

47. Blanking and Shearing (FEA and Experiments)
Different Zones of Blanked Edge Zr Zr Zs Zs Zf Zf
(b) Zb
Zr: rollover zone
Zs: shear zone
Zf: fracture/rupture zone
Zb: burr
(a)
Different zones of the blanked edge (a) simulations and (b) experiments

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
Snap-thru forces
Analysis of snap-thru forces during blanking through simulations

49. CPF 5.5 - Hot Stamping of Boron Steels
Eren Billur

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. 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. Introduction/Direct Hot Stamping
Direct hot stamping process

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. 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. 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. 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.
Tooling for hot stamping of B-Pillar

57. Case Study-1/ AUDI B-Pillar Section
Input geometries for simulation
Die
Punch
Assembly
Blank
Blank holder
Reference: Benchmark problem-3, Numisheet 2008

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

59. Case study-2/ Cooling Channel Design
-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. 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 5.6 - Applications of Servo Drive Presses in Stamping
Adam Groseclose

62. 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

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

64. 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

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

66. 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- 2011
HONDA-Aida- 2011

67. Schematic of Servo-press line (Aida/Honda)
2500 ton/ 18 SPM draw press (2009)
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

68. Suzuka Plant Production Picture
(Honda/Aida)

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

70. Applications- Deep Drawing 2/3
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]

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

72. Side Panel Outer Deep Drawing Case Example (Honda/Aida)

73. High-speed/ High Accuracy Servo-Press (Honda/Aida)

74. Servo-Hydraulic Cushion 1/2
(Courtesy-Aida)
Die Cushion Force (kN)
Elimination of Pressure Surge in the Die Cushion

75. Servo-Hydraulic Cushion 2/2
(Courtesy-Aida)
During Down Stroke, Cushion Pressure Generates Power

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

77. Summary
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.

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. 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 79