PSI - Issue 14

6 6

Nevil Martin Jose et al. / Procedia Structural Integrity 14 (2019) 403–409 Nevil Martin Jose t.al/ Structural Integ ity P ocedia 00 (2018) 00–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000

408

Master Curve Fracture Toughness data from Mini‐CT Tests Master Curve Fracture Toughness data from Mini‐CT Tests

100 120 140 160 180 200 100 120 140 160 180 200

Kjc (median) Kjc (median)

Tested/censo red Values Tested/censo red Values Uncensored Kjc Uncensored Kjc

40 60 80 40 60 80

Kjc 2% Kjc 2%

Fracture Toughness, Kjc (MPa.m^0.5) Fracture Toughnes , Kjc (MPa.m^0.5)

Kjc 98% Kjc 98%

‐50 ‐50

‐30 ‐30

‐10 ‐10

10 10

30 30

50 50

T‐To (degree celsius) T‐To (degree celsius)

Fig. 5. Master curve obtained from the experimental data of this work for different cumulative probabilities of failure viz., 2%, 98% and 50%-median 3.2 Fractography The fracture surface of MINI-CT-5 was examined using scanning electron microscopy. The fracture surface consisted of three regions viz., 1) Fatigue crack growth region, 2) A very small region showing ductile crack growth evidenced by void formation and second phase particles and 3) The large brittle fracture region showing river patterns of trans granular cleavage. These are shown in the images below Fig. 5. Master curve obtained from the experimental data of this work for different cumulative probabilities of failure viz., 2%, 98% and 50%-median 3.2 Fractography The fracture surface of MINI-CT-5 was examined using scanning electron microscopy. The fracture surface consisted of three regions viz., 1) Fatigue crack growth region, 2) A very small region showing ductile crack growth evidenced by void formation and second phase particles and 3) The large brittle fracture region showing river patterns of trans granular cleavage. These are shown in the images below

Fig. 6. Fracture surface of MINI-CT-5 showing three regions Fig. 6. Fracture surface of MINI-CT-5 showing three regions

Fig. 7. Enlarged view of region 1 in Fig.5; shows striations due to fatigue crack growth Fig. 7. Enlarged view of region 1 in Fig.5; shows striations due to fatigue crack growth

Fig. 8. Enlarged view of region 2, showing voids and second phase particles inside them. This region shows ductile crack growth. Fig. 8. Enlarged view of region 2, showing voids and second phase particles inside them. This region shows ductile crack growth.

Fig. 9 Enlarged view of region 3, showing trans-granular cleavage – brittle fracture Fig. 9 Enlarged view of region 3, showing trans-granular cleavage – brittle fracture