PSI - Issue 13

Ho-Wan Ryu et al. / Procedia Structural Integrity 13 (2018) 1932–1939 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

1934

3

2. Experiment 2.1. Materials and tensile properties

The materials used in this study are SA312 TP316 SS and CF8A CASS and Table 1 lists the chemical composition of both materials. Tensile tests were performed using smooth bar specimen under a quasi-static loading rate at room temperature (RT). Fig. 1(a) and Fig. 2(a) show the tensile stress versus strain curves for each TP316 SS and CF8A CASS material.

Table 1. Chemical compositions of SA312 TP316 SS and CF8A CASS (wt%). C Mn P S Si Ni Cr Mo

Co

N

Fe

SA312 TP316

0.021 1.25

0.038 0.004 0.45

12.21 16.31 2.06

-

-

-

CF8A

0.04

0.60

0.03

0.02

1.20

8.5

20.5

0.0

0.1

0.04

Balance

2.2. Hysteresis loops Cyclic round bar tensile tests were performed under strain-controlled loading to characterize a hardening behavior under low cycle fatigue (LCF) conditions. In these tests, specimen geometry and loading rate are the same with those in monotonic tensile test. Tests for SA312 TP316 SS material were conducted at three different strain amplitudes, 0.4%, 0.8% and 1.2%. For CF8A CASS material, six tests were performed ranged from 0.29% to 1.2%. As a result, hysteresis loops in Fig. 1(b) and Fig. 2(b) were obtained for each material. SA312 TP316 SS and CF8A CASS materials show significant cyclic hardening while consecutive cycles are accumulated.

(a)

(b)

(c) (d) Fig. 1. SA312 TP316 SS material; (a) monotonic tensile property, (b) cyclic hysteresis loops, (c) cyclic fracture toughness test results with R =-0.5 and (d) R =-1.0.