PSI - Issue 19

Shinji Hashimura et al. / Procedia Structural Integrity 19 (2019) 204–213 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Table 3 Experimental conditions

Bolt

Mean load Q m [kN]

Mean stress  m [MPa]

 m /  0.2 [%]

2.0 4.0 6.0 4.0 5.0 6.0 8.0

54.6 109 164 109 137 164 219

32.1 64.3 96.4 31.2 39.0 46.8 62.5

A5056 bolts

A6056 bolts

4. Experimental results 4.1. A5056 bolt

Figure 4 shows fatigue test results of A5055 bolts. In Fig. 4, the ordinate is the stress amplitude at the root of the first thread and the abscissa is the number of cycles to failure. The triangle symbol shows the results for Q m =2 kN and the square symbols shows those for Q m =4 kN. The circle symbol shows the results for Q m =6 kN. In each symbol, the black colour shows that the bolts broke at the first thread root. The grey colour shows the bolts broke at the incomplete thread root under bolt head. The symbols with an arrow show that the bolts did not break until 7 1 10  cycles. It can be seen in Fig. 4 that the fatigue strengths of A5056 bolts decrease with an increase in the mean load Q m . It is difficult to find significant differences in the fatigue lives although it tends that the fatigue lives are long if the mean load Q m is low. The fracture points of the bolt which broke by the stress amplitude just above the fatigue limits were the root of the incomplete thread under bolt head for Q m =4 kN and 6 kN and was the root of the first thread for Q m =2 kN. If the stress amplitude was comparatively low, the most fracture points were the root of the incomplete thread. 4.2. A6056 bolt Figure 5 shows fatigue test results of A6055 bolts. The ordinate and the abscissa in Fig. 5 is the same as Fig. 4. In Fig. 5, the triangle symbol shows the results for Q m =4 kN and the rhomboid symbols shows the results for Q m =5 kN.

Fig. 4 S-N diagram for aluminium alloy A5056 bolts

Fig. 5 S-N diagram for aluminium alloy A6056 bolts