Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Tubular Hydroforming of

Advanced Steel and

Aluminum Alloys

An Economic Evaluation using Technical

Cost Modeling

Bruce Constantine

Materials Systems Laboratory

April 20, 2001

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Primer: Tube Hydroforming

a

b

c

d

F

axial

F

axial

P

e

Derived from: Siempelkamp Pressen Systeme GmbH & Co.

f

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Goal: Demonstrate Materials Effects

•

Demonstrate how manufacturing with varying
steel and aluminum alloys affects the economics of
tube hydroforming

•

Presentation in two parts:

1. Survey of significant materials affects on

hydroforming process steps

-Fixed geometry: L=1m, d=65mm, t=1.7mm, 6 bends
-Fixed operating conditions: 200,000ppy

2. Review of design considerations to determine

functionally equivalent geometries; examination of
affect of geometry change on hydroforming
economics.

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Material Properties Impact Processing

Parameters

Process

Type

Relevant

Processes

Process Parameter

Material

Properties

Mechanica

l

Slitting,

Roll-Forming,

Bending,

Pre-Forming,

Hydroformin

g

Force & Pressure

σ

y

, n, k

f

, UTS

Tool Wear

μ

Processing Rate

m

Max. Strain to Failure

UTS, ε

max

, k

f

, ε

Forming

Thermal

Annealing,

Welding

Temperature

Phase diagram

binary transition

temperature

Processing Rate, bulk

processes

ρ, C

p

, T

Processing Rate, point

processes

ρ, C

p

, T, k

c

Electrical

Welding

Power

ρ, C

p

, K

Processing Rate

σ, ε

Frequency

σ, ε, μ

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Processes Occur in Three Cells

Decoil/Slit

Roll-Form

Metal Sheet

Bend

Anneal

Lubricate

Pre-Form

Hydroform

Trim

Tubes

Bent

Tubes

Components

u

1

u

2

u

3

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

$0

$2

$4

$6

$8

$10

$12

Trim

Hydroform

Preform

Lubricate

Bend

Roll Form

Decoil/Slit

Metal

Cost per Part

Subset of Costs are Significantly Material

Dependent

Hydroformed

Component

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

Roll-Form

Metal Sheet

Metal Sheet

Decoil/Slit

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends,

200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

CNC Bending of Thin-Walled Metal Tubes

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

•

Tube is pushed into tool, bent to desired
angle

Mandrel

Wiper Die

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

CNC Bending Machinery Costs

•

Investment = F(σ

yield,

d, t, # of radii)

=

•

Cycle time = F(formability, # of radii)

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

0.0295 M

xx

+ 214900

Single R

4E-09 M

xx

2

– 0.0148 M

xx

+197700

Multiple R

Steel

Aluminum

Bend Rate

0.58

rad/sec

0.37

rad/sec

Return

Rate

0.94

rad/sec

0.94

rad/sec

Traverse

1.25 m/sec

1.25 m/sec

Stack

Change

1.25 sec

1.25 sec

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

CNC Bending Tooling Costs

•

Investment = F(d, t, R, surface hardness)

•

Lifetime = F(surface hardness)

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

Mild

Steel

DP Steel

Aluminu

m

Mandrel

Chrome

AMPCO

Bronze

Chrome

Mandrel

Lifetime

25,000

bends

20,000

bends

10,000

bends

Wiper Die

Chrome

AMPCO

Bronze

Chrome

Wiper Die

Lifetime

10,000

bends

8,000 bends

4,000

bends

Cost of Chrome

Tool

Cost of AMPCO

Bronze Tool

Wiper Die

8.66d-185

9.05d - 165

Plug Mandrel

52.1exp(0.024d)

44.7exp(0.028d)

One-ball

Mandrel

85.8exp(0.024d)

78.8exp(0.027d)

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

CNC Bending of Thin-Walled Metal Tubes

6 bends, L=1m, d=50mm, t=2mm,

200000ppy

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

$0.00

$0.50

$1.00

$1.50

$2.00

$2.50

Mild Steel

(ASTM-A36)

Dual Phase 600 5754 Aluminum

B

en

d

in

g

C

o

st

p

er

T

u

b

e

Tooling
Main Machine
Labor
Other

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends,

200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Hydroforming Pressure Cycle

•

Application of internal fluid pressure, applied

in stages, leads to fully formed component

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

k

f

σ

y

σ

ε

P

t

Tube

Tool

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Hydroforming Equipment, Cycle Time and

Tooling

•

Press Investment = 32278*(Press Closing
Force)

0.41

(Press Closing Force) = F(k

f

, r, s’)

= k

f

*(0.57(r/s’))

-1.90

•

Cycle Time = F(σ

yield

, k

f

, pressurization rates)

•

Tooling Investment = F(L, surface finish, HB)

•

Tooling Life = F (surface finish)

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

k

f

σ

y

σ

ε

P

t

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Examples of Equipment, Cycle Time and

Tooling

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

Mild Steel

DP Steel

600

Aluminu

m 5754

Press

Investment and

Size

$2,320,000

24,000kN

$2,570,000

31,000kN

$1,940,000

15,000kN

Cycle Time

25.4 sec

28.0 sec

21.1 sec

Tooling

Investment

$491,400

$614,200

$550,350

Tooling Life

3,000,000

parts

3,000,000

parts

3,000,000

parts

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends,

200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Hydroforming Cost Factors by Material

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

$0

$1

$2

$3

$4

$5

$6

Mild Steel

Dual Phase 600 5754 Aluminum

H

y

d

ro

fo

rm

in

g

C

o

s

t p

e

r

T

u

b

e

Main Machine
Tooling
Labor
Other

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends,

200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

What if Annealing is Required?

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

Annealing

•

Requirement = F(formability)

•

Can result in dimensional changes,
increasing reject rate

•

Assumptions

– Furnace designed to feed single

hydroforming press

– Either in-line or batch annealing possible
– Investment = F(Hydroforming Cycle Time)

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Additional Cost of Annealing

Cycle Time

29.0

sec

32.0 sec

24.1 sec

Cont.

Invest.

$466,20

0

$444,60

0

$323,500

Batch

Invest.

$85,100

$77,100

$102,400

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

Mild Steel

Dual Phase

600

5754

Aluminum

A

n

n

e

a

li

n

g

C

o

s

t

p

e

r

Tu

b

e

Main Machine
Cost

Labor

Energy
Other

C

C

C

B

B

B

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

Annealing

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends, 200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Sensitivity of Annealing Cost to Scrap Rate

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

Annealing

$0.00

$0.50

$1.00

$1.50

$2.00

5754 Aluminum

[0.1% - 10%]

Dual Phase 600

[0.1% - 10%]

Mild Steel

[0.1% - 10%]

Annealing Cost per Tube

C

B

C

B

C

B

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends,

200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Total Cost of Hydroforming Different

Materials

Hydroformed

Part

Bend

Lubricate

Pre-Form

Metal Tube

Hydroform

Trim

$0

$2

$4

$6

$8

$10

$12

$14

$16

$18

M

ild

S

te

el

D

ua

l P

ha

se

6

00

TR

IP

S

te

el

57

54

A

lu

m

in

um

51

82

A

lu

m

in

um

60

16

A

lu

m

in

um

C

o

s

t

p

e

r

Tu

b

e

Annealing

Continuous Annealing

Batch Annealing

Trim

Hydroform

Pre-Form

Lubricate

Bend

Roll Form

Decoil/Slit

Metal

Case Assumptions: L=1m, d=65mm, t=1.7mm, 6 bends,

200,000 ppy

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Conditions of Functional Equivalence

Hydroformed

Part

Bend

Lubricate

Pre-form,

Hydroform,

Trim

Metal Tube

Roll-Form

Metal Sheet

Decoil/Slit

Annealing

•

One point fixed

•

Two points fixed

•

Two points pinned

•

Strategy: Use design conditions to calculate
tube dimensions of cost minimizing
functionally equivalent section under
different materials

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Many Geometries Yield Functional

Equivalence

Hydroformed

Part

Bend

Lubricate

Pre-form,

Hydroform,

Trim

Metal Tube

Roll-Form

Metal Sheet

Decoil/Slit

Annealing

F

max

= σ

y

I

L r

o

I = ¼ π (r

o

4

- r

i

4

)

Aluminum 5754

0

5

10

15

20

40

50

60

70

80

90

Diameter (mm)

W

al

l T

h

ic

kn

es

s

(m

m

)

•

Functionally equivalent to mild steel d=65mm,

t=1.7mm

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Competing Factors Set Up Optimization

Problem

Hydroformed

Part

Bend

Lubricate

Pre-form,

Hydroform,

Trim

Metal Tube

Roll-Form

Metal Sheet

Decoil/Slit

Annealing

Mass

Decreases

Projected Area

Increases

$0.00

$1.00

$2.00

$3.00

$4.00

$5.00

50

60

70

80

90

Diameter (mm)

H

y

d

ro

fo

rm

in

g

C

o

st

p

e

r

T

u

b

e

(

m

m

)

Aluminum 5754

$0.00

$5.00

$10.00

$15.00

M

at

er

ia

l

C

o

st

p

er

T

u

b

e

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Choice of Functionally Equivalent

Dimensions

Hydroformed

Part

Bend

Lubricate

Pre-form,

Hydroform,

Trim

Metal Tube

Roll-Form

Metal Sheet

Decoil/Slit

Annealing

$9

$10

$11

$12

$13

$14

$15

$16

$17

$18

$19

$20

35

45

55

65

75

85

Diameter (mm)

C

o

s

t

p

e

r

Tu

b

e

5754 Aluminum

Mild Steel

Dual Phase 600

TRIP Steel

5182 Aluminum
6016 Aluminum

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Cost of Functionally Equivalent

Hydroformed Parts

Hydroformed

Part

Bend

Lubricate

Pre-form,

Hydroform,

Trim

Metal Tube

Roll-Form

Metal Sheet

Decoil/Slit

Annealing

Material

Diamet

er

Thicknes

s

Cost*

Mass

Cost

of kg

saved

Mild Steel

65 mm

1.67 mm

$10.0

7

2.81

kg

Dual Phase

600

60 mm

1.66 mm

$11.3

0

2.55

kg

$4.73

TRIP Steel

60 mm

1.16 mm

$12.9

0

1.78

kg

$2.74

Aluminum

5754

80 mm

2.89 mm

$15.0

0

2.01

kg

$6.16

Aluminum

5182

80 mm

2.48 mm

$15.2

0

1.61

kg

$4.27

Aluminum

6016

80 mm

1.62 mm

$13.2

9

1.07

kg

$1.85

* L=1m, 6 bends, 200,000 ppy, does not include annealing

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Conclusions

•

Material dependence

•

Bending cost tooling surface
properties

•

Hydroforming cost machinery
flow stress

•

Annealing the wild card

•

Formability, design necessity

•

Cost related more strongly to scrap
rate and cycle time of hydroforming
than material properties (T, etc)

•

Must include geometry change to have
meaningful comparisons between functionally
equivalent parts

•

Geometry dictated by design condition

Cost minimizing geometry
Cost of each kg of mass saved

Hydroformed

Part

Bend

Lubricate

Pre-form,

Hydroform,

Trim

Metal Tube

Roll-Form

Metal Sheet

Decoil/Slit

Annealing

Massachusetts Institute of Technology

Cambridge, Massachusetts

Materials Systems Laboratory

Questions