New Trends in Welding in the Aeronautic Industry

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 • Physics • Economics • Case studies • LBW • EBW • FSW • Research at MIT • Analysis of trends

4. oxyacetylene flame Arc Welding , gas thermite Resistance welding Oxygen cutting Electron beam Arc welding fuel Laser beam , Electroslag / Friction Plasma flame Air 10 2 10 3 10 4 10 5 10 6 10 7 W/cm 2 practical range for welding d/w .2 10 - efficiency 1 99 % HAZ size 1-10 .01-.1 cm interaction 10-100 10 -4 - 10 -3 s max speed 0.1 0.1-1 1000 cm/s cost 10 3 10 4 10 6 $ Ordering of welding processes • The intensity of the heat source determines most properties of the welding process.

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

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

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

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

15. Weight reduction in small planes • Range increased 4% • Savings ~ $7000/lb Beechcraft Baron 58 1395 kg Eclipse 500 1225 kg

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. Friction stir Welding equipment is expensive • The cost of the equipment is proportional to the intensity of the heat source

19. Welding expenditures per unit

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: 20-40 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 ceramic metal

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

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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.