PSI - Issue 10

A. Karanika et al. / Procedia Structural Integrity 10 (2018) 66–72 A. Karanika et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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4

can be seen in Fig.3, while the respective mechanical properties are summarized in average values in Table 1. It is evident that by employing AA2060 in aircraft structures, an essential increase of almost 100 MPa (from approximate 400 to almost 500 MPa) can be achieved in terms of yield stress. This difference of 100 MPa can also be noticed for the case of ultimate tensile strength, where the new Al-Li alloy shows improved mechanical quasi static properties.

16

12

8

Load [kN]

4

0

0 2 4 6

8 10 12 14

Tensile strain (%)

Fig. 3. Tensile curves of reference specimens of AA2060-T8E30 coupons on the L direction.

Table 1. Tensile test details and results on AA2060-T8E30 L direction and comparison with 2024-T851. 2060-T8E30

2024 T851*

UTS (MPa)

Yield stress (MPa)

Ultimate Tensile Strength – UTS (MPa)

Tensile strain at UTS (%)

Conv. yield stress (Offset 0.2%) (MPa)

Young Modulus (GPa)

A/A

1 2 3 4 5

541 542 542 544 541

> 8.41 > 7.97 > 8.78 > 7.99 > 9.11

496 496 495 492 490

73.563 70.770 72.118 73.270 71.634

455*

400*

Table 2. and Fig.4 summarize the results of the constant amplitude fatigue tests. Fatigue tests have been performed with maximum applied stress being at specific ratios of yield stress, namely 40, 45, 55, 70 and 80%. The results show that fatigue endurance limit is around 200 MPa for the Al-Li alloy, while lower value can be retrieved from the literature for the ‘conventional’ AA2024.

Table 2. Fatigue test results performed on 2060-T8E30 – L Direction.

Max stress for 2060 T8E30 (MPa)

Max stress for 2024 T351 (MPa)*

Failure (yes/no)

Specimen ID

Static yield load (%)

maximum load (N)

minimum load (N)

amount load cycles

F1 F2 F3 F4 F5

80 70 55 45 40

9879 8644 6792 5557 4939

988 864 679 556 494

2.61E+04 5.78E+04 1.47E+05 1.00E+06 1.00E+06

395 346 272 198 148

y y y n n

280 240 180

110

* https://www.aircraftspruce.com/catalog/pdf/aluminumalloy.pdf