Center for Precision Forming ( Taylan Altan, Director (e-mail: [email protected])[email protected] A short Review March 2014.

Center for Precision Forming(www.cpforming.org

Taylan Altan, Director

(e-mail: [email protected])

A short Review

March 2014

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INTRODUCTION

• The Ohio State University (OSU) has 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 the Engineering Research Center for Net Shape Manufacturing (ERC/NSM – www.ercnsm.org)

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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

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CPF is supported by NSF and member companies,

interested in metal forming

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CURRENT PROJECTS

Project CPF-1.1 – Warm Forming of Al AlloysProject CPF-1.4 – Forming of AHSS in a Servo Press – Die Design Project CPF-2.1 – Material Properties and Formability Project CPF-2.2 – Forming Al in a Servo Press Project CPF 3.3 – Friction/Lubrication/Wear Project CPF-5.1 – Bending and Springback in Forming of AHSS and Copper Alloys Project CPF-5.2 – Blanking / PiercingProject CPF-5.2 A – Hole Flanging and Edge Cracking  Project CPF-5.5 -  Hot Stamping Project  CPF 5.6 Practical Method for Predicting Fracture Using FE Simulation

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AZ31B-OAA5754-O

T(°C) LDRRT -

275 2.6275 3.2

T(°C) LDRRT 2.1

250 2.5300 2.9

Velocity : 2.5-50mm/sec

Cup diameter: 40 mm

Insulation plate

Die ring

Heaters

Blank holder

Water inlet

Cushion pins

Punch

Sheet

CPF-1.1 - Warm Forming of Al, Mg, Ti & SSin an Aida Servo Drive Press

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CPF-1.4 - Forming of AHSS in a Servopress

Forming of AHSS in Servo Press

980 MPa(145 ksi)

590 MPa(85 ksi)

440 MPa(65 ksi)

270 MPa(40 ksi)

Can we use servo drive properties to improve formability and reduce springback in forming AHSS?

Die

Top die set8

CPF-1.4 - Forming of AHSS

Punch

Blank holder

Bottom die set

Materials of interest:DP 600DP 980And others

Forming of AHSS in Servo Press

Die design (manufactured by Shiloh) for testing AHSS.

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CPF-1.4 - Forming of AHSS in a Servopress

Forming of AHSS in Servo Press

1) Straight Bending2) Shrink Flanging3) Stretch Flanging4) U-Bending5) Curved U-Bending6) Deep Drawing

CPF/Shiloh die set (for 300 ton servo-press)

CPF-1.4 – Forming of AHSS in a Servopress

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R1

R2

R3 R4

R5R6

DIE

Parameter Notation Value

Concave side radius R1 601.6 mm

Convex side radius R2 598.4 mm

Cavity corner radii

R3 51.6 mm

R4 56.6 mm

R5 61.6 mm

R6 66.6 mm

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CPF-1.4 – Forming of AHSS in a Servopress

Example: Shrink and Stretch Flanging

DIE

BLANK

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CPF-1.4 - Forming of AHSS in a Servopress

Deep drawn sampleDP 600, t0 = 0.83 mmDraw depth = 50 mm

Forming of AHSS in Servo Press

Thinning (%)

Min = -12.8Max = 9.0

-9.7-12.8

9.05.82.7-0.4-3.5-6.6

Max. Thinning ~ 9%

CPF-2.1 Material Characterization

Downward motion

clamps the sheet

Before Forming After Forming

Stationary Punch

Pressure Transducer

Viscous Medium

Test Sample

Laser Sensor

Continued downward

motion forms the bulged

sheet

Viscous Pressure Bulge (VPB) Test

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CPF-2.1 Material Characterization – Flow Stress

Viscous Pressure Bulge (VPB) Test

0 0.1 0.2 0.3 0.4 0.50

200

400

600

800

1000

True Strain

True Stress (MPa) True Stress (ksi)

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58

87

116

145

VP Bulge Test

Tensile Test

Uniform Strain from Tensile Test = 0.16

Tensile data with Power Law (σ=Kεn)

Useful strain from Bulge Test = 0.49

Material, DP600, 1 mm

Before bursting After bursting

Test sample

CPF-2.1 - Material Characterization – VPB Test

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CPF-2.1 - Material Characterization – VPB Test

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CPF-2.1 - 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].

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

A B C D E F G H

Coil/Heat/Supplier

Do

me

he

igh

t b

efo

re b

urs

t (i

n)40

30

20

10

1.6

1.2

0.8

0.4

Maximum bulge height before fracture(mm) (in)

Batch / Coil / Heat / Supplier ID

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CPF-2.1 - Materials Tested with VPB Test at CPF(data available to CPF members)

Aluminum and Magnesium AlloysAA 6111

AA 5754-OX626 -T4P

AZ31BAZ31B-O

SteelsSt 14 DP 780-CR

St 1403 DP 780-HYAISI 1018 Bare DP 980 Y-type X

AKDQ Bare DP 780 T-Si type1050 GA DP 780 T- AI Type

DR 120 GA DP 780 Y-type UDDS GA DP 780 Y-type V

BH 210  DQS-270F GA-Phosphate coatedHSS  DQS-270D GA-Phosphate coated

DP500 DP 780DP 590 TRIP 780DP 600 DP 980

Stainless SteelsSS 201SS 301SS 304SS 409

SS 410 (AMS 5504)SS 444

LDX 2101

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CPF-2.1 - 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.

CPF-2.1 - Formability

Ref: Shi and Chen 2007

Stretch Bending

DP780Underbody structural part

DP980 B-pillar inner

Challenge:This type of fracture cannot be predicted using conventional Forming Limit Curve (FLC).

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CPF-2.2 - Forming of Al Alloys in a Servo Drive Press (AIDA)

Thinning (%)

Min = -26.3Max = 28.4

-18.5-26.3

28.420.512.74.9-2.9-10.7

Maximum thinning ~28%Draw depth = 155 mm

Material draw-inDie set built by Honda

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CPF-3.3 - 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)

CPF-3.3 - Friction – Cup Draw Test

Shorter Perimeter

Higher BHF before fracture

Cup Draw Test

Lubrication performance:

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CPF-3.3 - Friction / Tribology

Ref: Kim et al 2009

Temperatures in Cup Draw Test – DP 600

Contact area with die

Challenges: 1) Higher contact pressure and higher temperature are detrimental for lubricants, 2) Temperature and pressure additives are needed

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CPF-3.3 - Friction / Lubrication

Evaluation of Lubricants for Forming Al 5182-0 (1.5 mm)

Punch(Stationary)

Die Insert

Dp = 152.4 mm

r = 5 mmt0 = 0.77 mm

r = 20 mm

Punch(Stationary)Die Insert

Press Motion

Ironingt ≈ 0.70 mm

Dp = 152.4 mm

r = 5 mm

t0 = 0.77 mm

r = 20 mm

Press Motion

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CPF-3.3 - Forming of AHSS / Die Wear

Die Wear in Forming of AHSS

Currently with DP590In future, Stainless Steel

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CPF-5.1 – Bending and springback in Forming AHSS and Copper Alloys

Schematic of 3 point bending tooling at OSU

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CPF-5.2 - Blanking/Piercing of AHSS

Blanking / PiercingSchematic of piercing

vp = punch velocity fb = blank holder forcedp = punch diameter dd = die diameterrp = punch corner radius rd = die corner radiusdb = blank holder diameter t = sheet thicknessPunch-die clearance (% of sheet thickness) = (dd-dp)/2t*100

Fracture zone (Zf)

Burr zone (Zb)

Roll over zone (Zr)

Shear zone (Zr)

Blanked edge(obtained from FE simulations)

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CPF-5.2 - Blanking/Piercing of AHSS

Reduction of strains at blanked surface

Single shear Conical with flat tip

HumpedConical with spherical tip

0.600000000000

001

1 1.5 2 2.5 3 3.5 3.60

0.5

1

1.5

2

2.5

3

Flat

Humped

Conical

Distance from the top surface of the sheet (mm)

Eff

ecti

ve s

trai

n

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CPF-5.2A – Hole Flanging/Edge Cracking

Hole Expansion Test

Schematic of hole expansion test

vp=punch velocity fb=blankholder forceθ=punch angle (conical) dd=diameter of the diedb=diameter of blankholder rd=die radiusdh=diameter of pierced hole in the blankdp=punch diameter (hemispherical)

Punch

θdp

dd

rd

db

vp

fbBlank Holder

DIE dh

Before and After Hole Expansion(conical punch)

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CPF-5.5 - Hot Stamping

Ref: Grote 2009, Gutermuth 2011.

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)

Eas

ier

to F

orm

22MnB5

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CPF-5.5 - Hot Stamping

Colors other than gray:Thinning >20%. Part stamped at the participating

company

FE Simulation of parts with uniform properties

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CPF-5.5 - Hot Stamping

Nodal temperature - Membrane

5425

23020017114211283

FE Simulation of cooling channel analysis

1.3 mm roof rail die,After 10 stampings.

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CPF-5.5 - Hot Stamping

FE Simulation of cooling channel analysis

After 10 stampings.

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CPF-5.5 - Hot Stamping

Hardened zone:485 – 515 HV1500 – 1590 MPa(~220 – 230 ksi)

Soft zone:310 – 330 HV920 – 1020 MPa(~135 – 150 ksi)

Literature:[George 2011] , 400°C dies = 790-840 MPa [Feuser 2011], 450°C dies = ~850 MPa

FE Simulation of parts with tailored properties

0 0.02 0.04 0.06 0.08 0.1 0.12 0.140

200

400

600

800

1000

1200

1400

Strain (mm/mm)

Str

ess

(MP

a)

CPF–5.6 - New Project: Prediction of Fracture

Prediction of fracture/necking from strain or thickness variations (tensile data from Jim Dykeman-Honda HRA)

0 50 100 150 2000

0.1

0.2

0.3

0.4

0.5

0.6

Maj

or S

trai

n (m

m/m

m)

Time (s) 36

Questions / Comments?

For more information , please contact:

Dr. Taylan Altan ([email protected]), 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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