1. New Trends in Welding in the Aeronautic Industry
Patricio F. Mendez (MIT/Exponent)
Thomas W. Eagar (MIT) 1

2. Welding for Aeronautics is Growing!

3. Outline Fundamentals Case studies Research at MIT Analysis of trends
Physics
Economics
Case studies
LBW
EBW
FSW
Research at MIT
Analysis of trends

4. Ordering of welding processes
The intensity of the heat source determines most properties of the welding process. 10 2 4 5 6 7 3
Air /
fuel
gas
flame
Electroslag ,
oxyacetylene
thermite
Friction
Arc welding
Resistance welding
Oxygen cutting
Plasma
Arc Welding
Electron beam
Laser beam
W/cm
practical range for welding
d/w
efficiency
HAZ
size
interaction
max speed
cost - % cm s
cm/s $ .2 1
1-10
10-100
0.1 99
.01-.1 -4
- 10 -3
1000
0.1-1
Penetration increases dramatically--> higher efficiency and higher welding speeds
Interaction time of 0.3 sec= minimum human operator can do.

5. Characteristics of aeronautical industry
low unit production
high unit cost
extreme reliability
severe operating conditions

6. Joining processes in aeronautics
Bird’s eye view
Laser beam welding
Electron beam welding
Friction stir welding

7. Laser beam welding Concentrated heat source
Can be done in open atmosphere
Uses: A318, A380

8. Electron Beam Welding Concentrated heat source Must be done in vacuum
Uses: F22, Titanium

9. Friction Stir Welding Solid-state process No need for shielding gas
Uses: Eclipse, Space Shuttle

10. Concentrated heat makes stronger welds
Electron beam and laser beam make stronger welds than arc welding
2219 alloy
Ironically, the strongest alloys are also the less weldable. This is because they obtain their strength from microstructure and heat treatment, and welding destroys those two.

11. Concentrated heat causes less distortion
Electron beam welding and laser beam welding melt much less than other processes
much less distortion
less metallurgical defects
Electron beam
GTAW

12. Solid state processes have no solidification defects
No cast structure, fine grain
Friction Stir Welding
Can weld 7XXX
stronger than 2XXX
Diffusion Welding
Can weld Ti, not Al

13. Velocity, weight, money 1 10 100 1000 10000 100000 Velocity [km/h]
Savings per pound lighter [$/lb]
car
$2/lb
airliner
$200/lb
military jets
$2,000/lb
rockets
$20,000/lb

14. The pursuit for weight reduction
10-15 tons lighter!
$5 million in fuel savings over lifetime

15. Weight reduction in small planes
Beechcraft Baron 58
1395 kg
Eclipse kg
Range increased 4%
Savings ~ $7000/lb

16. Weight reduction in space
2219 Al2195 Al-Li
1% Li
7500 lb weight savings
Essential to to get to the ISS
$75 million savings per launch

17. Weight reduction in engines
Compressors, fans
machined titanium, composites, friction welded
Hot sections
friction welded inconel

18. Welding equipment is expensive
The cost of the equipment is proportional to the intensity of the heat source
Friction stir
FSW incredibly expensive, that’s the reason it’s in aerospace

19. Welding expenditures per unit
Total welding expenditures
Units produced in a year
Welding expenditures per unit
$2.5 billion
30 million
~$100
$200 million
2,500
~$100,000
$50 million
100
~$500,000

20. Proportion of welding expenditures

21. Labor costs are highest in aero industry

22. Welding expenditures are smallest for aerospace

23. Implications of welding economics
Welders in aeronautics are highly qualified
Proportion of welding expenses are small
Large window of opportunity for
process development
employment
Cost efficiency likely to increase with scale
Laser and friction stir welding cheaper than riveting

24. Case Studies

25. Laser Beam Welding: A318/A380
Riveting consumes 40% of man hours on structure
LBW cuts time by half (8 m/min!)
Less expensive (fewer mfg steps)
Less corrosion (no holes, crevices)
Lighter (no sealing)
Stronger than rivets
Same fatigue life

26. New Structures Skin sheet unaffected
Welding on both sides simultaneously

27. Electron Beam Welding: F-22
Aft fuselage
90 m of EBW, 76 cast parts)

28. Friction Stir Welding: Eclipse 500
65% of riveted joints=30,000 rivets eliminated
Welded:
Cabin, aft fuselage, wings, and engine mounts
Riveted:
Tail, longitudinal fuselage joints, skins thinner than 0.040”

29. Friction Stir Welding: Eclipse 500
Welds three times stronger
Equal fatigue strength
Better corrosion properties
Riveting: 6 in/min
FSW: in/min
$50,000-$100,000 savings per plane
Less factory space

30. Friction Stir Welding: Space Shuttle
GTAW
VPPA
FSW:
solves purging problems
stronger

31. Friction Stir Welding: Boeing
Boeing made $15 million investment in FSW
Delta rockets
(1st flight: Delta II on 8/99)

32. Friction Stir Welding: A380
FSW
faster, stronger, better fatigue, less corrosion
Incompatible with Glare

33. Research at MIT: modeling
New modeling technique: OMS
Order of Magnitude Scaling
Can reduce number of experiments
Can give approximate solutions to equations
Can generalize numerical or experimental results

34. Research at MIT Ceramic to metal joining TLP, patterned interfaces

35. Research at MIT
EBSFF (3D bodies without mold)

36. Startup: Semi-Solid Technologies
Fast manufacturing: SSM-SFF
Semi-solid die-casting
Semi-solid welding

37. (2000)  

38. (2000)   

39. (2000)    

40. (2000)    
!!

41. Conclusions (2002) Rivets are being replaced by welding at a fast pace
Welding is expanding its role in airplanes
From fuselage parts, to wings
Use of welding will influence materials selection
Favors metals over composites
Development of high-strength Al alloys

42. Conclusions (2002) FSW is the focus of much attention
If Eclipse 500 is successful:
FSW will increase role in airplanes
Boeing might use FSW rocket experience to airplanes
Airbus might revive FSW plans
For rockets
FSW replacing fusion processes
VPPA losing appeal
EB welding losing appeal (Russia)
For jet engines
FSW not ready yet for Ti and superalloys
Linear friction welding used for military apps.