PSI - Issue 1

R. Baptista et al. / Procedia Structural Integrity 1 (2016) 098–105 Author name / Structural Integrity Procedia 00 (2016) 000 – 000

103

6

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

0.00005

Findley Parameter Nomal Stress max(sxx'n) Shear Stress txx'a

B&M Parameter Nomal Strain (Dexx'n) Shear Strain txx'a

0.00004

0.00003

0.00002

0.00001 B&M Parameter

Findley Parameter [MPa]

0

-90

-60

-30

0

30

60

90

-90

-60

-30

0

30

60

90

 [deg]

 [deg]

a)

b)

0.000004

0.000015

0.000003

0.00001

0.000002

SWT

0.000005

0.000001

Fameti-Socie Parameter

0

0

-90

-60

-30

0

30

60

90

-90

-60

-30

0

30

60

90

 [deg]

 [deg]

c)

d)

0.00005

0.000015

0.00004

0.00001

0.00003

( D xx'n)*( De xx'n)

0.00002

0.000005

Chu Parameter

0.00001

0

0

-90

-60

-30

0

30

60

90

-90

-60

-30

0

30

60

90

 [deg]

 [deg]

e) f) Fig. 4. Fatigue crack initiation criterions for different parameters and crack initiation angles, for a phase 30º. a) Findley, b) Brown-Miller, c) Fatemi-Socie, d) SWT, e) Liu I, f) Chu For out-of-phase loadings it was possible to assess that loading paths have a small influence on the determined fatig ue crack initiation direction angle β. Findley , Brown-Miller and Fatemi-Socie parameters depend also on material properties ( k and S ) which were considered as  = 0.2 and = 0.2, representative of AISI303 stainless steel, Reis et al. (2009), but, a small change of these parameters only has influence on the load case with δ=180º , which may change slightly de crack initiation angle. As one can see for the out-of-phase load cases studied the predicted fatigue initiation angle is always 45º for the Findley, Brown-Miller, Fatemi-Socie, Lui I, Liu II and Chu models, and 90º for the SWT and Liu I models.

Table 1. Fatigue crack initiation predicted angles by several criteria (β angle in [º]) . Findley Brown-Miller Fatemi-Socie SWT Liu I Chu

δ =0º

-

-

-

-

-

-

δ =180º

-51/51 -45/45 -45/45 -45/45 -45/45

-51/51 -45/45 -45/45 -45/45 -45/45

-45/45 -45/45 -45/45 -45/45 -45/45

-90/0/90 -90/0/90 -90/0/90 -90/0/90 -90/0/90

-90/0/90 -90/0/90 -90/0/90 -90/0/90 -90/0/90

-45/45 -45/45 -45/45 -45/45 -45/45

δ =30º δ =45º δ =60º δ =90º