Statistical aspects of fatigue crack growth life of base metal, weld metal and heat affected zone in FSWed 7075-T651 aluminum alloy

The fatigue crack growth of longitudinal SAW welds of a API 5L X42 steel pipe was evaluated using curved three point bend test specimens, where the radius of curvature of the specimens was equal to the pipe radius, so that no extensive machining or flattening was required. The fatigue crack growth tests were done in a servohydraulic closed loop machine under load control, in air at room temperature. The da/dN vs ∆K plots and Paris’s equation constants were obtained for the base metal, deposited metal and heat affected zone in the CR orientation, which corresponds to the short transverse direction of the pipe. The greater resistance to fatigue crack growth was the base metal, whereas the deposited metal showed the least resistance to the fatigue crack propagation. The deposited metal and the heat affected zone behaved according to Paris’s law, unlike the base metal, that showed a high dispersion of the fatigue crack growth rates. This behavior was due to the propagation of the crack in the direction transverse to the banded microstructure. Furthermore, the differences in fatigue crack growth rates among each zone were also related to the roughness of the fracture surfaces and fracture toughness.

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Evaluation of Crack Growth of Ni-Base Alloys Under Long Term Cyclic Loading in BWR Environment

Volume 1A: Codes and Standards ◽

10.1115/pvp2015-45458 ◽

2015 ◽

Author(s):

Masao Itatani ◽

Takuya Ogawa

Keyword(s):

Growth Rate ◽

Fatigue Crack ◽

Cyclic Loading ◽

Crack Growth Rate ◽

Fatigue Crack Growth ◽

Weld Metal ◽

Crack Growth ◽

Base Metal ◽

Test Data

Crack growth test data of Ni-base alloys under cyclic loading in simulated boiling water reactor (BWR) environment including the effects of load rising time (tr) were evaluated in the view points of both fatigue and stress corrosion cracking (SCC). When the test data were plotted in the relationship between da/dt and Kmax, da/dt monotonically decreased with increasing tr and the stress ratio (R). For alloy 182 weld metal under short tr and/or low R, the crack growth rate assuming SCC is much lower than those of the test data. For alloy 182 under tr = 30 and 1000 s at R = 0.8, the crack growth rate assuming SCC almost coincided with test data. For heat affected zone (HAZ) of alloy 600 base metal (600HAZ), the crack growth rate assuming SCC had much different slope of da/dN-ΔK relationship compared with the test data in the tested range of tr up to 3000 s. From these observations, the contribution of SCC is relatively small and the main mechanism of crack growth is thought to be fatigue for the tested range (tr=1 to 1000 s for weld metal, tr=1 to 3000 s for base metal and R = 0.1 to 0.8). It was assured that the fatigue crack growth formula proposed by the authors accounts the effect of SCC adequately at long tr. Additionally, the applicability of the fatigue crack growth rate formula for austenitic stainless steels to the long term cyclic load was investigated and it was found that the formula can be applied to tr=30000 s.

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Fatigue crack growth at the representative zones in friction stir welding of a heat-treatable aluminum alloy at 200oC

Vietnam Journal of Science and Technology ◽

10.15625/2525-2518/56/1/10091 ◽

2018 ◽

Vol 56 (1) ◽

pp. 39 ◽

Cited By ~ 1

Author(s):

Tran Hung Tra

Keyword(s):

Aluminum Alloy ◽

Fatigue Crack ◽

Friction Stir Welding ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Base Metal ◽

Comparable Amount ◽

Friction Stir ◽

Fine Grain ◽

Aluminum Alloy 6063

Aluminum alloy 6063-T5 plates were joined by friction stir welding technique. The fatigue crack growth (FCG) in the thermo-mechanical affected zone (TMAZ) and in the heat affected zone (HAZ) of the welding was examined at 200oC. Although the grain microstructure of the TMAZ was significantly refined in comparison with that of BM, the FCG rate in TMAZ and base metal was shifted a comparable amount when the test temperature was elevated from room temperature to 200oC. In the metallurgical view, the FCG rate in the fine grain TMAZ was higher than that in coarse grain HAZ and base metal site.

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