SN curve(s) of an anisotropic material

HI,

     I was just wondering how many S-N curves would i need to  define the fatigue properties of an anisotropic material. For an isotropic material we just use 1-curve. Would that also  be enough  for an anisotropic material? We need 21 elastic constants to define anisotropic material. Would the number of SN curves be similar or be somehow related to the number or would the number of S-N curves required would be probabilistic in nature. i.e. we find the S-N curves along several planes and get a some sort of probabilistic distibution. 

 

Atul Jain

I have strung and unstrung my instrument,

but the song i came to sing remains largely unsung


Yongming Liu's picture

See if this paper

See if this paper helps.

Liu. Y., Mahadevan, S. Probabilistic fatigue life prediction of multidirectional composite laminates. Composite Structures, Vol. 69, pp. 11-19, 2005. 

It has a corrigendum. It suggests that at least 3 independent S-N curves are required for 2D case. For more general anisotropic materials, it will be more complex.