Page 385 - Handbook of Materials Failure Analysis

References 383

The fatigue simulation predicts that a fatigue crack initiates at the SPR #9 after
50,540 cycles. This prediction was in agreement with the experimental results. It
should be noted that the fatigue model adopted in this case study predicts only
the crack initiation life. Crack propagation phase must be dealt with separately, using
a fracture mechanics based model.

4 CONCLUSION
In this chapter, fatigue models of welded joints were classified into different
approaches and their features were explained. An automotive substructure was con-
sidered for the case study and its fatigue behavior was predicted using a fatigue
model based on the local notch approach. Through the case study, the following con-
clusions were made:
• An unusual asymmetric shape of the hysteresis loop is the key feature of the
cyclic behavior of wrought Mg alloys.
• The constitutive material model adopted in this study was capable of simulating
the asymmetric cyclic hardening behavior of Mg alloys.
• Accounting for the asymmetric hardening behavior and using the local strain
energy model resulted in a successful prediction of the failure location and crack
initiation life.

ACKNOWLEDGMENTS
Authors would like to acknowledge the contribution of Mi Chengji, a visiting PhD student
from Hunan University in China, in developing the detailed geometry of the riveted areas
as well as a FE model for the whole Demo-structure.

REFERENCES
[1] Stephens RI, Fatemi A, Stephens RR, Fuchs HO. Metal fatigue in engineering. 2nd ed.
New York: Willey; 2001.
[2] ASTM. Standard terminology relating to fatigue and fracture testing. West
Conshohocken, PA: ASTM International; 2012.
[3] Reed RP, Smith J, Christ B. The economic effects of fracture in the United States.
Washington, DC: National Bureau of Standards Special Publication; 1983, p. 1–7.
[4] Pook LP. Metal fatigue: what it is, why it matters. Dordrecht: Springer; 2007.
[5] Milne I, Ritchie RO, Karihaloo BL. Comprehensive structural integrity: cyclic loading
and fatigue. Oxford, UK: Elsevier; 2003.
[6] Suresh S. Fatigue of materials. Cambridge: Cambridge University Press; 1998.
[7] Fatemi A, Socie DF. A critical plane approach to multiaxial fatigue damage including
out-of-phase loading. Fatigue Fract Eng Mater Struct 1988;11:149–65.