PSI - Issue 14

Ashish Vaidya et al. / Procedia Structural Integrity 14 (2019) 410–415

413

Ashish Vaidya et al. / Structural Integrity Procedia 00 (2018) 000 – 000

4

strain rate curves shown in Fig. 4 (a) and (b) respectively.

(b)

(a)

Fig. 3. (a) Creep life Vs Notch Depth; (b) Creep rupture life vs Notch acuity ratio ((t/ρ) .

(a)

(b)

Fig. 4. (a) Creep curve; (b) Strain rate curve for grade 92 steel at 195 MPa.

3.2 Fractography

Fig. 5 shows fractured surface morphologies of V-notched creep tested specimens. All notched creep specimens revealed mixed mode of fracture form notch root to the center of the specimen. Fig. 5 (a) & (b), depict dimpled morphology all over the fractured surface which shows that the mode of fracture was predominantly ductile for 0.5 mm notch depth specimen. From Fig. 5 (c) & (d), it can be seen that the fractured surface near the notch root was fine fibrous and at the center it was course fibrous. Fig. 5 (e) revealed the signature of shear fracture at the notch root due to significant constraint for elastic deformation in 2.0 mm notched creep specimen. Fig. 5 (f) shows the center of 2.0 mm notched fractured creep specimen where the dimples are covered in fine fibrous fracture.