Heng Yang

This study investigates the microstructure and texture inheritance of cold-pilgered Ti-3Al-2.5V titanium alloy tubes for aerospace hydraulic systems during recrystallization annealing at 590 °C, 620 °C, and 720 °C. Tubes with radial and circumferential initial textures were evaluated using Electron Backscatter Diffraction (EBSD) and uniaxial tensile tests coupled with Digital Image Correlation (DIC). The Kearns f-factor and contraction strain ratio (CSR) quantified orientation intensity and macroscopic anisotropy, respectively. Results show that microtexture distribution and intensity vary minimally during annealing. Even at 720 °C (the completion of primary recrystallization), the component and radial texture intensity remain largely consistent with the cold-pilgered state. Thus, the microstructural texture of Ti-3Al-2.5V tubes demonstrates strong inheritance characteristics during recrystallization annealing.

1. The investigated tubular joining component (TJC) is a form-fit tube–sleeve connection fabricated by elastomeric swaging and incorporated into a threaded, detachable aircraft tubing assembly. Thi...

1. Polycrystalline titanium (Ti) materials are extensively employed in modern aerospace, marine, energy and healthcare industries owing to their high specific strength, superior corrosion-resistanc...

High-strength titanium alloy tubes are widely used in advanced aircraft and engine hydraulic systems due to their high specific strength and excellent fatigue resistance. Fatigue damage in the tubes during the service process decreases the reliability of hydraulic systems, posing a serious threat to operational safety. Introducing residual compressive stress on the surface of tubes by magnetic needle grinding (MNG) process would enhance their fatigue performance. However, the failure mechanisms of the MNG-strengthened tubes in rotating-bending fatigue tests are still not fully understood. In this work, the different residual compressive stresses were first introduced on the surface of high-strength Ti-3Al-2.5V tubes by MNG process, and then the rotating-bending fatigue tests and failure analysis on the tube connection assemblies were conducted to clarify the failure mechanisms of the MNG-strengthened tubes. The main findings include: 1) With MNG process, the axial residual compressive stress on the tube surface increased from approximately 47 MPa to 298 MPa, making the fatigue life increase from roughly 360,000 cycles to 20,000,000 cycles. 2) The residual compressive stress shifts the fatigue crack initiation site from the outer surface to the subsurface, which inhibits surface crack initiation, reduces the width of fatigue striation, and improves fatigue resistance. 3) If the roughness generated by the MNG process exceeds a certain threshold, it will intensify stress concentration, accelerating crack initiation and propagation, thereby reducing fatigue life. To improve the fatigue life of titanium alloy tubes, it is essential to increase residual compressive stress and simultaneously decrease surface roughness. The insights developed in this work contribute to the advancement of high-performance tubular component manufacturing and support the safe operation of aircraft.

Tubular titanium components have been widely used in advanced equipment in aerospace, marine, energy, and healthcare fields over the past decades. For commercial pure titanium (CP-Ti) tubes with hexagonal close-packed (HCP) crystal structure, the limited slip systems and the strong texture caused by multi-pass thermal–mechanical processing make the material always exhibit a strong anisotropy in damage evolution, which easily leads to early failure of components during forming processes. The accurate characterization and modeling of anisotropic damage evolution is a non-trivial issue for excavating the forming potential of materials. In this study, firstly, by taking the large-diameter thin-walled CP-Ti tube as a case material, the uniaxial tension tests along the 0°, 45°, and 90° directions, as well as the simple shear and plane strain tension tests, were designed and conducted to obtain the anisotropic plasticity and fracture behaviors. Then, by integrating a direction-dependent damage rate multiplier and the Hill'48 yield function into the Lode-parameter dependent Lemaitre (Lode-Lemaitre) damage model, the modified Lode-Lemaitre model was established, numerically implemented, and calibrated for the description of the anisotropic damage evolution of the CP-Ti tube. Finally, the prediction ability of the modified Lode-Lemaitre model was evaluated, and the damage evolution of the CP-Ti tube under various loading conditions was analyzed. The comparisons of the experimental and simulation results show that the prediction error of fracture displacement was reduced from 43.2% to 5.48%, and the wall thickness distribution of the Y-shaped tube was accurately predicted. These results prove that the modified Lode-Lemaitre model can accurately describe the anisotropic damage evolution of the CP-Ti tube.