PSI - Issue 36

Robert Kosturek et al. / Procedia Structural Integrity 36 (2022) 153–158 Robert Kosturek, Janusz Mierzyński, Marcin Wachowski et al. / Structural Integrity Procedia 00 (2021) 000 – 000

155

3

Low-cycle fatigue tests have been performed on Instron 8802 Servohydraulic Fatigue Testing System with three various total strain amplitudes: 0.25, 0.35, and 0.5% with strain ratio R = -1. Selected fractured samples were subjected to the observations on a scanning electron microscope (SEM) Jeol JSM-6610. 3. Results and discussion All obtained joints were defect-free and their basic mechanical properties (together with joint efficiency) have

been established in the tensile test. The results are presented below (Tab. 3). Table 3. Tensile strength and joint efficiency for the tested samples. Sample Tensile strength

Joint efficiency

M1 M2 M3 M4

223 MPa 226 MPa 236 MPa 209 MPa

93% 94% 98% 87%

In all cases, the value of joint efficiency is very high (about 90%) with the best result for the M3 sample (98%). The failures have occurred in the heat-affected zones. Low-cycle fatigue properties have been examined at three different values of total strain amplitude and the obtained plots cycles to failure vs stress amplitude are presented in Fig. 1.

a)

b)

c)

d)

Fig. 1. Cycles to failure vs stress amplitude for total strain amplitude of 0.25% (a), 0.35% (b), 0.5% (c) and stabilized hysteresis loops for 0.5% strain amplitude (d).