PSI - Issue 19

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

8

R.B. Kalombo et al. / Procedia Structural Integrity 19 (2019) 688–697

695

39

N = 10 6 Cycles

38

37

34 Bending stress, s a (MPa) 35 36

33

AAC Orchid

AAAC 823 MCM

Cable type

Fig. 5. Constant fatigue life diagram for the two cables at 10 6 cycles.

Macroscopic and microscopic analysis of broken strands were also carried out. This information is important as it provides valuable data to compare with a numerical model for the fatigue of the cable/suspension clamp system in order to understand this fatigue phenomenon more accurately. Three types of strand fractures were observed; the quasi planar (QP), 45°, and the V type. One could conclude that the two cables presented a similar behaviour in terms of the percentage of the strand fracture, despite small differences (Fig. 6).

70%

AAC Ochid_Aluminium 1350

AAAC 823 MCM_Aluminium 1120

60%

50%

50%

44%

38%

40%

36%

30%

10% Purcentage of broken strands 20%

18%

14%

0%

QP

45°

V

Type of broken strand

Fig. 6. Percentage of type of broken strands for the two cables.

It is clear that both cables presented a similarity in the crack propagation in the strands during its fatigue (Fig. 7). To understand the fatigue phenomena better, the microscopic analysis of the fracture area was performed. The results indicate that the crack always originated at the fretting mark caused by the small relative movement between cable