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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made by machining from a block. Hence that is not hexagon shape but circular shape. The diameter of ADC nut was set 13 mm same as the A5056 nut in order to equalize the nut stiffness. Table 1 shows the mechanical properties of the test bolts and Table 2 shows the chemical compositions of the test bolts. It can be seen in Table 1 that the ultimate strength and the proof stress of A6056 bolts are significantly higher than those of A5056 bolts. Figure 3 shows a schematic illustration of fatigue tests. The grip length of bolted joint in the fatigue tests was l g =32 mm. The bolted joint was set to the fatigue testing machine as shown in Fig. 3 at first. And then the fatigue tests were started applying the load amplitude Q a to the bolted joint after the bolted joints were applied the mean load Q m as the clamp force F . The fatigue test jigs were made of stainless steel JIS SUS304.

Table 1 Mechanical properties of test bolt

Material

Ultimate strength  u

0.2% proof stress  0.2

A5056 A6056

303 MPa 425 MPa

170 MPa 350 MPa

Table 2 Chemical compositions of test bolt

Material

Cu

Fe

Si

Mn

Cr

Zn

Mg

Ti

Zr

Zr+Ti

Al

A5056 A6056

0.01 0.99

0.12 0.15

0.07 0.10

0.07 0.78

0.07 0.02

0.00 0.48

4.58 0.97

0.03 0.00

-

-

RE. RE.

0.08

0.08

Table 3 shows the mean load Q m in the fatigue tests, the mean stress  m for each mean load and stress ratios  m /  0.2 of the mean stress against the proof stress of the test bolts. The effective sectional area of M8 bolt was 36.6 mm 2 . The mean load Q m for A5056 bolts were set Q m =2 kN, 4 kN and 6 kN taking the proof stress of A5056 bolt into account. The mean load Q m for A6056 bolts were set Q m =4 kN, 5 kN, 6 kN and 8 kN. Even if Q m =8 kN, the mean stress  m was 62.5 % against the proof stress because the proof stress of A6056 bolts were significantly higher than A5056. The fatigue tests were achieved until the bolt broke or the number of cycle reached to 7 1 10  cycles. Frequency of cyclic load was 20 Hz.

Fig. 3 Schematic illustration of fatigue test.

Fig. 2 Test bolt and test nuts