PSI - Issue 5

Yoichi Kayamori et al. / Procedia Structural Integrity 5 (2017) 286–293 Yoichi Kayamori et al. / Structural Integrity Procedia 00 (2017) 000 – 000

288

3

2. CTOD and plastic rotational deformation

A well-known CTOD calculation formula that is prescribed in BS7448 (1991) and ISO 12135 (2002) is given by the following equation, where  is the total CTOD,  el is the elastic component of CTOD,  pl is the plastic component of CTOD, K is the stress intensity factor,  is Poisson’s ratio,  ys is the yield stress, E is Young’s modulus, r p is the plastic rotational factor, V p is the plastic part of the clip gauge opening displacement, and z is the height of the knife edge measurement point from the load line:       p p p ys pl el V r W a a z r W a E K          0 0 0 2 2 2 1      (1) The calculation of  pl is derived from the plastic hinge model, where plastic rotational deformation is assumed as shown in Fig.1. Some r p values have been proposed for CTOD calculation in C(T) specimens. Merkle and Corten (1974) conducted plastic limit analysis, and the following coefficient,  , was obtained:

1

   

   

2

2

  

   

  

   

  

  

 W a a 2 0

 W a a 2 0

 W a a 2 0

2

2

1









(2)

0

0

0

Eq.(2) gives the following r p according to their plastic displacement diagram:      0.5 1 p r

(3)

WES1108 (2016) replaced the factor of 0.5 in Eq.(3) with 0.43 as shown in the following equation:      0.43 1 p r

(4)

Shiratori and Miyoshi (1981) carried out slip line field analysis, and the following equation was obtained:

1

   

      

2

2

  

   

  

1 2    

  

W

 W a W

W

2 1

r

r

r

1

,

0.370

 









(5)

p

0

0

 W a

 W a

0

0

0

Fig.1 Plastic hinge model of a deformed C(T) specimen.