Issue 37

N. Zuhair Faruq, Frattura ed Integrità Strutturale, 37 (2016) 382-394; DOI: 10.3221/IGF-ESIS.37.49

Fig.4. This algorithm is developed based on the multi-variable optimisation method known as a Gradient Ascent Method [15].

Figure 4 : Flowchart to explore the orientation of the critical plane [15]. In order to explore the critical plane, a notched component is considered subjected to in-service cyclic load as shown in Fig. 5a. Then, by taking full advantage of the theory of critical distance, multiaxial local strain history is determined at a specific distance from the notch apex equal to critical distance. The local strain history is described with the following strain tensor (see Fig. 5b):





t ( )

t ( )

       

        

xy

xz



t ( )

x

2

2





t ( )

t ( )

xy

yz

  t ( ) 



 

(4)

t ( )

y

2

2





t ( )

t ( )

xz

xz

z 

t ( )

2

2

In the above equation, ε x are shear strain history. According to the maximum variance method, shear strain amplitude is described by the following Eq. 5: (t) , ε y (t) and ε z (t) are normal strain components, whereas xy  yz xz t ( ), t and t ( ), ( )  

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