PSI - Issue 39

Keke Tang et al. / Procedia Structural Integrity 39 (2022) 387–392 Author name / Structural Integrity Procedia 00 (2021) 000–000

391

5

capacity of lamellar structure tend to decline when the elliptical notch evolves into line crack.

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055 0.060 0.065 0.070

0.045

0.045

Lamellar;a=30,b=15 No lamellar;a=30,b=15 No lamellar;a=30,b=15

Lamellar;a=30,b=25 No lamellar;a=30,b=25 No lamellar;a=30,b=25

Lamellar;a=30,b=20 No lamellar;a=30,b=20 No lamellar;a=30,b=20

0.040

0.040

0.035

0.035

0.030

0.030

0.025

0.025

LE

LE

LE

0.020

0.020

0.015

0.015

0.010

0.010

0.005

0.005

0.000

0.000

0

5

10

15

20

0

5

10

15

20

0

5

10

15

20

D

D

D

C

C

Path Length/μm

Path Length/μm

Path Length/μm

C

(a)

(b)

(c)

Fig.4 Radial strain distribution at both sides of the elliptical notch

4.3. Strain accumulation along circular path If both ends of the elliptical notch are distributed with single phase grains, it can be seen from Figure 5(a) that strain variation is relatively stable. Strain gradually increases to maximum and then decreases. As the notch aspect ratio increases from Figure 5(a) to 5(c), high strain accumulation stands out. If both ends of the notch are distributed with lamellar structure, according to Figure 5(a), strain accumulation at both ends of the notch stands out and fluctuates significantly. There are multiple strain peaks in the curve. With the increase of notch aspect ratio, the lamellar structure also aggregates at one point with high strain accumulation. It means that, the lamellar structure can improve fatigue performance by adjusting strain-bearing area, but as the aspect ratio of the notch increases, the adjustment ability degrades accordingly.

Lamellar;a=30,b=15 No lamellar;a=30,b=15 No lamellar;a=30,b=15

Lamellar;a=30,b=25 No lamellar;a=30,b=25 No lamellar;a=30,b=25

Lamellar;a=30,b=20 No lamellar;a=30,b=20 No lamellar;a=30,b=20

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055

0.12

0.10

0.08

0.06

LE

LE

LE

0.04

0.02

0.00

0

5

10 15 20 25 30 35 40 45

0

5 10 15 20 25 30 35 40 45

0

5

10 15 20 25 30 35 40 45

A

A

A

B

B

B

Path Length/μm

Path Length/μm

Path Length/μm

(a)

(b)

(c)

Fig.5 Circular strain distribution at both sides of the elliptical notch

5. Conclusions Within the framework of CPFE modelling, bimodal RVE models with elliptical notches are established to study the effect of lamellar structure distribution for Ti-6Al-4V titanium alloy. The main findings are summarized as follows Lamellar structure around notch causes strain uniformity and thus avoid continuous strain and formation of in through cracks. Fatigue performance of bimodal Ti-6Al-4V can be enhanced by lamellar structure distribution around notch. Lamellar structure distribution leads to strain oscillation and enlarge load-bearing area. Fatigue resistance of the notch can be improved. Influence of notch size on whole RVE model is negligible, while local strain accumulation differs for varying notch sizes. As the notch aspect ratio increases, the adjustment ability of lamellar structure appreciably declines.