Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions

  • M. Grujicic
  • B. Pandurangan
  • A. Arakere
  • C-F. Yen
  • B. A. Cheeseman


A critical assessment is carried out of the microstructural changes in respect of the associated reductions in material mechanical properties and of the attendant ballistic-impact failure mechanisms in prototypical friction stir welding (FSW) joints found in armor structures made of high-performance aluminum alloys (including solution-strengthened and age-hardenable aluminum alloy grades). It is argued that due to the large width of FSW joints found in thick aluminum-armor weldments, the overall ballistic performance of the armor is controlled by the ballistic limits of its weld zones (e.g., heat-affected zone, the thermomechanically affected zone, the nugget, etc.). Thus, in order to assess the overall ballistic survivability of an armor weldment, one must predict/identify welding-induced changes in the material microstructure and properties, and the operative failure mechanisms in different regions of the weld. Toward this end, a procedure is proposed in the present study which combines the results of the FSW process modeling, basic physical-metallurgy principles concerning microstructure/property relations, and the fracture mechanics concepts related to the key blast/ballistic-impact failure modes. The utility of this procedure is demonstrated using the case of a solid-solution strengthened and cold-worked aluminum alloy armor FSW-weld test structure.


aluminum armor ballistic limit failure mechanisms friction stir welding 



The material presented in this article is based on the study supported by two Army Research Office sponsored grants (W911NF-11-1-0207 and W911NF-09-1-0513) and two U.S. Army/Clemson University Cooperative Agreements (W911NF-04-2-0024 and W911NF-06-2-0042).


  1. 1.
    A. Sullivan, C. Derry, J.D. Robson, I. Horsfall, and P.B. Prangnell, Microstructure Simulation and Ballistic Behavior of Weld Zones in Friction Stir Welds in High Strength Aluminium 7xxx Plate, Mater. Sci. Eng. A, 2011, 528, p 3409–3422CrossRefGoogle Scholar
  2. 2.
    W.M. Thomas, E.D. Nicholas, J.C. Needham, M.G. Murch, P. Temple-Smith, and C.J. Dawes, “Friction Stir Butt Welding,” International Patent Application No. PCT/GB92/02203, 1991Google Scholar
  3. 3.
    M. Grujicic, B. Pandurangan, K.L. Koudela, and B.A. Cheeseman, A Computational Analysis of the Ballistic Performance of Light-Weight Hybrid-Composite Armors, Appl. Surf. Sci., 2006, 253, p 730–745CrossRefGoogle Scholar
  4. 4.
    H. Liu, H. Fulii, M. Maeda, and K. Nogi, Tensile Properties and Fracture Locations of Friction-Stir Welded Joints of 6061-T6 Aluminium Alloy, J. Mater. Sci. Lett., 2003, 22, p 1061–1063CrossRefGoogle Scholar
  5. 5.
    W.B. Lee, C.Y. Lee, W.S. Chang, Y.M. Yeon, and S.B. Jung, Microstructural Investigation of Friction Stir Welded Pure Titanium, Mater. Lett., 2005, 59, p 3315–3318CrossRefGoogle Scholar
  6. 6.
    W.M. Thomas and E.D. Nicholas, Friction Stir Welding for the Transportation Industries, Mater. Des., 1997, 18, p 269–273CrossRefGoogle Scholar
  7. 7.
    J.Q. Su, T.W. Nelson, R. Mishra, and M. Mahoney, Microstructural Investigation of Friction Stir Welded 7050-T651 Aluminum, Acta Mater., 2003, 51, p 713–729CrossRefGoogle Scholar
  8. 8.
    O. Frigaard, Ø. Grong, and O.T. Midling, A Process Model for Friction Stir Welding of Age Hardening Aluminum Alloys, Metall. Mater. Trans. A, 2001, 32, p 1189–1200CrossRefGoogle Scholar
  9. 9.
    M.W. Mahoney, C.G. Rhodes, J.G. Flintoff, R.A. Spurling, and W.H. Bingel, Properties of Friction-Stir-Welded 7075 T651 Aluminum, Metall. Mater. Trans. A, 1998, 29, p 1955–1964CrossRefGoogle Scholar
  10. 10.
    C.G. Rhodes, M.W. Mahoney, W.H. Bingel, R.A. Spurling, and C.C. Bampton, Effect of Friction Stir Welding on Microstructure of 7075 Aluminum, Scr. Mater., 1997, 36, p 69–75CrossRefGoogle Scholar
  11. 11.
    G. Liu, L.E. Murr, C.S. Niou, J.C. McClure, and F.R. Vega, Microstructural Aspects of the Friction-Stir-Welding of 6061-T6 Aluminum, Scr. Mater., 1997, 37, p 355–361CrossRefGoogle Scholar
  12. 12.
    M. Grujicic and G. Arakere, Computational Investigation of Hardness Evolution During Friction-Stir Welding of AA5083 and AA2139 Aluminum Alloys, J. Mater. Eng. Perform., 2011, 20(7), p 1097–1108CrossRefGoogle Scholar
  13. 13.
    J.C. Bassett and S.S. Birley, Proceedings of the 2nd Symposium on Friction Stir Welding, TWI, 2000 (on CD)Google Scholar
  14. 14.
    K. Sampath, Adv. Mater. Process., 2005, 163, p 27–29Google Scholar
  15. 15.
    C. Garcia-Cordovilla, E. Louis, and A. Pamies, Microstructure and Susceptibility to Stress Corrosion Cracking of Al-Zn-Mg Weldments (AA-7017), Mater. Sci. Eng., 1994, 174A, p 173–186Google Scholar
  16. 16.
    C. Johnson, Amphibian Warfare, Nov–Dec, 1998, p 2–16Google Scholar
  17. 17.
    K.J. Colligan, P.J. Konkol, J.J. Fisher, and J.R. Pickens, Friction Stir Welding Demonstrated for Combat Vehicle Construction, Weld. J., 2003, 82(3), p 34–40Google Scholar
  18. 18.
    K.J. Colligan, J.J. Fisher, J.E. Cover, and J.R. Pickens, Adv. Mater. Process., 2002, 160(9), p 39–41Google Scholar
  19. 19.
    P.L. Threadgill, A.J. Leonard, H.R. Shercliff, and J.P. Withers, Friction Stir Welding of Aluminum Alloys, Int. Mater. Rev., 2009, 54(2), p 49–93CrossRefGoogle Scholar
  20. 20.
    M.M.Z. Ahmed, B.P. Wynne, W.M. Rainforth, and P.L. Threadgill, Proceedings of the 7th Symposium on Friction Stir Welding, TWI, Awaji Island, 2008 (on CD)Google Scholar
  21. 21.
    G.G. Corbett, S.R. Reid, and W. Johnson, Impact Loading of Plates and Shells by Free-Flying Projectiles: A Review, Int. J. Impact Eng., 1996, 18(2), p 141–230CrossRefGoogle Scholar
  22. 22.
    K.S. Kumar, D. Singh, and T. Bhat, Studies on Aluminum Armour Plates Impacted by Deformable and Non-Deformable Projectiles, Mater. Sci. Forum., 2004, 465–466, p 79–84CrossRefGoogle Scholar
  23. 23.
    T. Børvik, O.S. Hopperstad, and K.O. Pedersen, Fracture Mechanisms of Aluminum Alloy AA7075-T651 Under Various Loading Conditions, Int. J. Impact Eng., 2010, 37, p 537–551CrossRefGoogle Scholar
  24. 24.
    T. Børvik, M.J. Forrestal, O.S. Hopperstad, T.L. Warren, and M. Langseth, Perforation of AA5083-H116 Aluminium Plates with Conical-Nose Steel Projectiles—Calculations, Int. J. Impact Eng., 2009, 36, p 426–437CrossRefGoogle Scholar
  25. 25.
    M.R. Edwards and A. Mathewson, The Ballistic Properties of Tool Steel as a Potential Improvised Armor Plate, Int. J. Impact Eng., 1997, 19, p 297–309CrossRefGoogle Scholar
  26. 26.
    T. Børvik, J.R. Leinum, J.K. Solberg, O.S. Hopperstad, and M. Langseth, Observations on Shear Plug Formation in Weldox 460 E Steel Plates Impacted by Blunt-Nosed Projectiles, Int. J. Impact Eng., 2001, 25, p 553–572CrossRefGoogle Scholar
  27. 27.
    M.J. Forrestal, V.K. Luk, and N.S. Brar, Penetration of Aluminum Armor Plates with Conical-Nose Projectiles, Mechanics, 1990, 10, p 97–105Google Scholar
  28. 28.
    A.J. Piekutowski, M.J. Forrestal, K.L. Poormon, and T.L. Warren, Ogive-Nose Steel Rods at Normal, Int. J. Impact Eng., 1996, 18, p 877–887CrossRefGoogle Scholar
  29. 29.
    T. Børvik, A.H. Clausen, O.S. Hopperstad, and M. Langseth, Perforation of AA5083-H116 Aluminium Plates with Conical-Nose Steel Projectiles—Experimental Study, Int. J. Impact Eng., 2004, 30, p 367–384CrossRefGoogle Scholar
  30. 30.
    A.H. Chausen, T. Børvik, O.S. Hopperstad, and A. Benallal, Flow and Fracture Characteristics of Aluminium Alloy AA5083-H116 as Function of Strain Rate, Temperature and Triaxiality, Mater. Sci. Eng., 2004, A364, p 260–272Google Scholar
  31. 31.
    A.P. Rybakov, Spall in Non-One-Dimensional Shock Waves, Int. J. Impact Eng., 2000, 24, p 1041–1082CrossRefGoogle Scholar
  32. 32.
    M. Grujicic, B. Pandurangan, C.-F. Yen, and B.A. Cheeseman, Modifications in the AA5083 Johnson-Cook Material Model for Use in Friction Stir Welding Computational Analyses, J. Mater. Eng. Perform., doi: 10.1007/s11665-011-0118-7, 2011
  33. 33.
    M. Grujicic, G. Arakere, B. Pandurangan, J.M. Ochterbeck, C-.F. Yen, B.A. Cheeseman, A.P. Reynolds, and M. A. Sutton, Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys, J. Mater. Eng. Perform., doi: 10.1007/s11665-011-0069-z, 2011
  34. 34.
    M. Grujicic, G. Arakere, A. Hariharan, B. Pandurangan, C-F. Yen, and B.A. Cheeseman, Two-level Weld-Material Homogenization Approach for Efficient Computational Analysis of Welded Structure Blast Survivability, J. Mater. Eng. Perform., doi: 10.1007/s11665-011-9876-5, 2010
  35. 35.
    M. Grujicic, G. Arakere, A. Hariharan, and B. Pandurangan, A Concurrent Product-Development Approach for Friction-Stir Welded Vehicle-Underbody Structures, J. Mater. Eng. Perform., doi: 10.1007/s11665-011-9955-7, 2010
  36. 36.
    M. Grujicic, G. Arakere, B. Pandurangan, and A. Hariharan, Statistical Analysis of High-Cycle Fatigue Behavior of Friction Stir Welded AA5083-H321, J. Mater. Eng. Perform., 2011, 20(6), p 855–864CrossRefGoogle Scholar
  37. 37.
    M. Grujicic, G. Arakere, B. Pandurangan, A. Hariharan, C.-F. Yen, B.A. Cheeseman, and C. Fountzoulas, Computational Analysis and Experimental Validation of the Ti-6Al-4V Friction Stir Welding Behavior, J. Eng. Manuf., 2010, 224(8), p 1–16Google Scholar
  38. 38.
    M. Grujicic, G. Arakere, B. Pandurangan, and A. Hariharan, Development of a Robust and Cost-Effective Friction Stir Welding Process for Use in Advanced Military Vehicle Structures, J. Mater. Eng. Perform., 2011, 20(1), p 11–23CrossRefGoogle Scholar
  39. 39.
    M. Grujicic, G. Arakere, H.V. Yalavarthy, and T. He, Modeling of AA5083 Material-Microstructure Evolution During Butt Friction-Stir Welding, J. Mater. Eng. Perform., 2010, 19(5), p 672–684CrossRefGoogle Scholar
  40. 40.
    M. Grujicic, T. He, G. Arakere, H.V. Yalavarthy, C.-F. Yen, and B.A. Cheeseman, Fully-Coupled Thermo-Mechanical Finite-Element Investigation of Material Evolution During Friction-Stir Welding of AA5083, J. Eng. Manuf., 2010, 224(4), p 609–625CrossRefGoogle Scholar
  41. 41.
    ABAQUS Version 6.10EF, User Documentation, Dassault Systems, 2011Google Scholar
  42. 42.
    C. F. Yen, Army Research Laboratories, Work in Progress, 2012Google Scholar

Copyright information

© ASM International 2012

Authors and Affiliations

  • M. Grujicic
    • 1
  • B. Pandurangan
    • 1
  • A. Arakere
    • 1
  • C-F. Yen
    • 2
  • B. A. Cheeseman
    • 2
  1. 1.Department of Mechanical EngineeringClemson UniversityClemsonUSA
  2. 2.Army Research Laboratory—Survivability Materials BranchAberdeen, Proving GroundUSA

Personalised recommendations