1

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

2

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

σ, ε, µ

Frequency

σ, ε

Processing Rate

ρ, C

p

, T, k

c

Processing Rate, point processes

ρ, C

p

, T

Processing Rate, bulk processes

UTS, ε

max

, k

f

, ε

Forming

Max. Strain to Failure

m

Processing Rate

µ

Tool Wear

ρ, C

p

, K

Power

Welding

Electrical

Phase diagram binary

transition temperature

Temperature

Annealing,

Welding

Thermal

σ

y

, n, k

f

, UTS

Force & Pressure

Slitting,

Roll-Forming,

Bending,

Pre-Forming,

Hydroforming

Mechanical

Material Properties

Process Parameter

Relevant

Processes

Process

Type

3

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

4

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

1.25 sec

1.25 sec

Stack Change

1.25 m/sec

1.25 m/sec

Traverse

0.94 rad/sec

0.94 rad/sec

Return Rate

0.37 rad/sec

0.58 rad/sec

Bend Rate

Aluminum

Steel

5

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

8,000 bends

AMPCO Bronze

20,000 bends

AMPCO Bronze

DP Steel

4,000 bends

10,000 bends

Wiper Die Lifetime

Chrome

Chrome

Wiper Die

10,000 bends

25,000 bends

Mandrel Lifetime

Chrome

Chrome

Mandrel

Aluminum

Mild Steel

44.7exp(0.028d)

52.1exp(0.024d)

Plug Mandrel

78.8exp(0.027d)

9.05d - 165

Cost of AMPCO

Bronze Tool

85.8exp(0.024d)

One-ball Mandrel

8.66d-185

Wiper Die

Cost of Chrome

Tool

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

Bendi

ng Cost

pe

r T

ube

Tooling

Main Machine

Labor

Other

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

6

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

7

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

3,000,000

parts

$614,200

28.0 sec

$2,570,000

31,000kN

DP Steel

600

3,000,000

parts

3,000,000

parts

Tooling Life

$550,350

$491,400

Tooling

Investment

21.1 sec

25.4 sec

Cycle Time

$1,940,000

15,000kN

$2,320,000

24,000kN

Press Investment

and Size

Aluminum

5754

Mild Steel

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

dr

of

or

m

ing Cost

per

T

ube

Main Machine

Tooling

Labor

Other

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

8

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

$77,100

$444,600

32.0 sec

$102,400

$85,100

Batch Invest.

$323,500

$466,200

Cont. Invest.

24.1 sec

29.0 sec

Cycle Time

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

Mild Steel

Dual Phase

600

5754

Aluminum

A

n

neali

ng C

o

st p

er

T

u

be

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

9

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

Mil

d S

te

el

Du

al

Ph

ase

600

TR

IP

S

te

el

5754 A

lu

m

in

um

5182 A

lu

m

in

um

6016 A

lu

m

in

um

Cos

t pe

r Tube

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

10

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 Thi

ck

ne

ss

(mm)

•

Functionally equivalent to mild steel d=65mm, t=1.7mm

11

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)

Hy

dr

of

o

rm

ing

Cost

pe

r Tu

be

(

m

m

)

Aluminum 5754

$0.00

$5.00

$10.00

$15.00

Ma

te

ri

al

C

o

st

per

T

ube

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

st per

Tub

e

5754 Aluminum

Mild Steel

Dual Phase 600

TRIP Steel

5182 Aluminum

6016 Aluminum

12

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

$1.85

1.07 kg

$13.29

1.62 mm

80 mm

Aluminum 6016

$4.27

1.61 kg

$15.20

2.48 mm

80 mm

Aluminum 5182

$4.73

2.55 kg

$11.30

1.66 mm

60 mm

Dual Phase 600

$2.74

1.78 kg

$12.90

1.16 mm

60 mm

TRIP Steel

$15.00

$10.07

Cost*

$6.16

Cost

of kg

saved

2.89 mm

1.67 mm

Thickness

2.01 kg

80 mm

Aluminum 5754

2.81 kg

65 mm

Mild Steel

Mass

Diameter

Material

* 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

13

Massachusetts Institute of Technology
Cambridge, Massachusetts

Materials Systems Laboratory

Questions