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<p>Four-point bend fatigue tests were conducted on AA2024-T7 aluminum alloy plates (10&#xa0;mm thickness) on L-T (Longitudinal-Transverse), L-S (Longitudinal-Short transverse) and T-S planes, respectively. The fatigue strengths in these directions were measured to be approximately 225.3&#xa0;MPa, 245.8&#xa0;MPa and 180&#xa0;MPa, respectively. The fatigue strengths along the L-direction differ by 25% from that along the T-direction. It was found that the number of surface cracks observed in these specimens followed a Weibull function dependent on the applied maximum cyclic stress, enabling the quantification of the density and strength distribution of fatigue crack initiation&#xa0;sites. The crack initiation&#xa0;site densities measured on the L-T, L-S and T-S planes were 48 mm<sup>2</sup>, 50 mm<sup>2</sup> and 18 mm<sup>2</sup>, respectively, demonstrating significant fatigue damage anisotropy in the Al alloy&#xa0;plates. SEM examinations revealed that cracks preferably were initiated at the pre-fractured Fe-containing particles in surface when cyclic loading was in the L direction, such as in L-S and L-T samples. In comparison, in T-S samples loaded along the T direction, cracks were predominantly originated at Si-containing particles or sometimes grain boundaries&#xa0;in surface. In L-T and L-S samples, crack propagation was predominantly transgranular, with a minor proportion of a crack being intergranular. In contrast, crack propagation in T-S samples was primarily intergranular.</p>

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The Anisotropy of Fatigue Crack Initiation and Propagation in an AA2024-T7 Al Alloy Plate

  • 期刊论文

  • 发表日期：

    2026年2月28日

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  • Huiru Shang,
  • Fuqiang Guo,
  • Min Cui,
  • Yihang Li,
  • Conghui Xu,
  • Tongguang Zhai

摘要

Four-point bend fatigue tests were conducted on AA2024-T7 aluminum alloy plates (10 mm thickness) on L-T (Longitudinal-Transverse), L-S (Longitudinal-Short transverse) and T-S planes, respectively. The fatigue strengths in these directions were measured to be approximately 225.3 MPa, 245.8 MPa and 180 MPa, respectively. The fatigue strengths along the L-direction differ by 25% from that along the T-direction. It was found that the number of surface cracks observed in these specimens followed a Weibull function dependent on the applied maximum cyclic stress, enabling the quantification of the density and strength distribution of fatigue crack initiation sites. The crack initiation site densities measured on the L-T, L-S and T-S planes were 48 mm2, 50 mm2 and 18 mm2, respectively, demonstrating significant fatigue damage anisotropy in the Al alloy plates. SEM examinations revealed that cracks preferably were initiated at the pre-fractured Fe-containing particles in surface when cyclic loading was in the L direction, such as in L-S and L-T samples. In comparison, in T-S samples loaded along the T direction, cracks were predominantly originated at Si-containing particles or sometimes grain boundaries in surface. In L-T and L-S samples, crack propagation was predominantly transgranular, with a minor proportion of a crack being intergranular. In contrast, crack propagation in T-S samples was primarily intergranular.