PSI - Issue 5

Yoichi Kayamori et al. / Procedia Structural Integrity 5 (2017) 279–285 Yoichi Kayamori et al. / Structural Integrity Procedia 00 (2017) 000 – 000

282

4

2

   

   







  

    y c m

(6)





y

Begley (1974) showed an equation of J versus uniform strain, and the equation is approximately regarded as the following equation for  ≫  y :    y J E c 2  (7)

Substituting J = m  y  into Eq.(7),  is given by the following form:

   

   

2







  

    y c m 

(8)



y

However, Eq.(8) is valid only for a quite large strain level. In this study, a constant was put in the right side of Eq.(8) in order to form a continuous design curve with Eq.(6) at  /  y = 1. The following CTOD design curve was consequently obtained.

         

2

   

   







  

  

for

(9 ) a

1



m





y

y





c



y

   

   

   

    

2



2 1





  

  

for

(9 ) b

1



m





y

y

3. CTOD calculation in corner boxing fillet welded joints

3.1. CTOD obtained by finite element analysis

The authors (2008) conducted 3-D elastic-plastic finite element analysis (FEA) of a semi-elliptical surface crack in a corner boxing fillet welded joint model, and  was calculated using the deformed crack profile. In addition, another corner boxing fillet welded joint model without crack was also analyzed for calculating  as the average local strain by area around an assumed crack. In this study,  and  in the welded joint models were referred to, and the applicability of Eqs.(9a) and (9b) to CTOD estimation was investigated. Mechanical properties were set as shown in Table 1 for four structural steels with different Y/T . Other analytical conditions such as welded joint modeling, meshing, boundary conditions, stress-strain curve modeling and an FEA code used are shown in the reference (2008).

Table 1. Mechanical properties used for reference finite element analysis (2008). Steels  y (MPa) Y / T JIS SN490 375 0.68 JIS SM490 381 0.74 API 5L X80 583 0.82 JIS HT780 830 0.95