Virtual Testing and Its Application in Aerospace Structural Parts

  • Bahram Farahmand


In many occasions, metallic parts will undergo plastic deformation either during their service usage or prior to their actual operation in the manufacturing and assembly phases. Under these circumstances, material properties may change considerably and must be accounted for when estimating the residual strength capability of parts. The change in material properties will occur when load has been removed and the work-hardening phenomenon has caused increase in material yield value, reduction in percent elongation, and degradation in fracture allowables. For these reasons, new static and fracture data must be generated if safe-life assessment must be performed on fracture critical parts. Fracture data are currently obtained through the ASTM testing standards, which are costly and labor intense. Difficulties associated with preparing the specimen, precracking the notch, recording and monitoring the data, obtaining the variation of fracture toughness versus part thickness, capturing data in the threshold region, and repeating the test in many cases due to invalid results make the virtual testing technique extremely helpful to overcome the time and cost related to the above-mentioned testing difficulties. Farahmand (Fatigue & Fracture Mechanics of High Risk Parts, Chapman & Hall, 1997, Chapter 5; Fracture Mechanics of Metals, Composites, Welds, and Bolted Joints, Kluwer Academic Publisher 2000, Chapter 6) utilized the extended Griffith theory to obtain a relationship between the applied stress and half a crack length by using the full stress–strain curve for the material under consideration. The extension of this work led to estimation of material fracture toughness and construction of full fatigue crack growth rate curve (Farahmand, J. Fract., 2007, Vol. 75, pp 2144–2155). This technique will be very useful to implement when materials undergo plastic deformation (the work-hardening phenomenon) and fracture allowables are needed to conduct a meaningful life analysis assessment of parts. First, Farahmand’s virtual testing theory is described briefly and, subsequently, the application of this methodology to two cases of aerospace pressurized tanks, exposed to plastic deformation, presented in this chapter.


Fracture Toughness Stress Intensity Factor Fatigue Crack Growth Friction Stir Welding Fatigue Crack Growth Rate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


  1. 1.
    B. Farahmand, Fatigue & Fracture Mechanics of High Risk Parts, Chapman & Hall, 1997, Chapter 5Google Scholar
  2. 2.
    B. Farahmand, Fracture Mechanics of Metals, Composites, Welds, and Bolted Joints, Kluwer Academic Publisher, November 2000, Chapter 6Google Scholar
  3. 3.
    B. Farahmand, “Predicting Fracture and Fatigue Crack Growth Properties Using Tensile Properties, Engineering,” J. Fract., Vol.75, 2007, pp. 2144–2155Google Scholar
  4. 4.
    B. Farahmand, De Xie, F. Abdi, “Estimation of Fatigue and Fracture Allowables for Metallic Materials Under Cyclic Loading,” AIAA-2007Google Scholar
  5. 5.
    B. Farahmand, “Multiscaling of Fatigue” Application of virtual testing for obtaining fracture allowables of aerospace and aircraft materials. Springer, 2008 (A Book Chapter by G. Sih)Google Scholar
  6. 6.
    G. Irwin, “Fracture Dynamics,” Fracture of Metals, ASM, 1948, p. 147Google Scholar
  7. 7.
    E. Orowan, “Fracture and Strength of Solids,” Rep. Prog. Phys., Vol. 12, 1949, pp. 185–232CrossRefGoogle Scholar
  8. 8.
    Fatigue Crack Growth Computer Program “NASGRO 4.0”, JSC, SRI, ESA, and FAA, 2002Google Scholar
  9. 9.
    MIL-HDBK-5H “Military Handbook Metallic Materials and Elements for Aerospace Vehicle Structure”Google Scholar
  10. 10.
    B. Farahmand, “Virtual Testing for Estimating Material Fracture Properties (Reducing Time & Cost of Testing),” 11th International Conference on Fracture (ICF11), Turin Italy, March 2005Google Scholar
  11. 11.
    NHB 8071 “Fracture Control Requirements for Payloads Using the National Space Transportation System (NSTS),” NASA, Washington, DC, 1985Google Scholar
  12. 12.
    Metal lined Composite Overwrapped Pressure Vessels (COPVs), Arde Inc., 875 Washington Avenue, Carlstadt, New Jersey 07072Google Scholar
  13. 13.
    Military Standard 1522A, “Standard General Requirements for Safe Design Operation of Pressurized Missile and Space System,” USA, May 1984Google Scholar
  14. 14.
    B. Farahmand and M. Doyle, “Obtaining Fracture Properties by Virtual Testing and Multiscale Modeling,” The Aging Aircraft Conference, 2009Google Scholar
  15. 15.
    B. Farahmand and G. Odegard, “Obtaining Fracture Properties by Virtual Testing and Molecular Dynamics Techniques,” The NSTI Conference, 2009Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.Taylor Aerospace (TASS – Americas) Inc.KirklandUSA

Personalised recommendations