Issue 59

M. Shariyat, Frattura ed Integrità Strutturale, 59 (2022) 423-443; DOI: 10.3221/IGF-ESIS.59.28

Figure 1: Samples (not used by the present research) of variations of the fatigue stress amplitude versus the mean stress (constant fatigue life diagrams), for a UD Glass/Epoxy ply [7]: (a) in the direction of fibers, (b) transverse to fibers, and (c) in-plane shear. Based on Eqn. (12), Eqn. (10) becomes:

2

    

        

2

   

 a

 a

1

2



















  , m u





, n N

  , m u





, n N

  2 2



a

2

2 2

 



a

1



R

1

2



1

1

1

1

1



R



1

2



1

2

   

   

   12

a





(13)









  , m u





, n N

 



a



R

1

12



  a a

1 2





1







    2







  , m u

  , m u







, n N

, n N

 

  2 2



a

a

1

2

2 2



R

1

1

1

1

1

1



R

1



2



1

Indeed, using the  function is identical to imposing Puck and Schurmann (i.e., Coulomb-Mohr) modifications, but in a more detailed and accurate manner; because the different frequencies, means, and asynchronous time variations and time shifts of the stress components are taken into account as well.

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