Fatigue & Fracture of Engineering Materials & Structures最新文献

This study investigated the fatigue property of DD6 nickel-based single crystal superalloy using in situ scanning electron microscopy (SEM), focusing on the coupled effects of secondary orientations ([010] and [110]) and recrystallization defects, representing the first comprehensive report of this synergistic interaction. Surface recrystallization significantly deteriorated fatigue resistance, with crack nucleation preferring recrystallized regions. [110]-oriented specimens exhibited superior fatigue durability compared to [010]-oriented counterparts in both pristine and recrystallized conditions. [010]-oriented specimens showed pronounced cross-slip activity, while [110]-oriented samples maintained single-slip deformation. Fatigue crack propagation in [010] orientation was governed by multi-octahedral slip system activation. Combined electron backscatter diffraction (EBSD) analysis and crystal plasticity finite element modeling (CPFEM) demonstrated that [010]-oriented specimens accumulated higher cumulative shear strain (CSS) under equivalent stress conditions compared to [110]-oriented samples, directly correlating with reduced fatigue life. A unified fatigue life prediction model incorporating orientation and recrystallization effects was developed for cyclic loading evaluation.

Retained austenite is prevalently observed in advanced high-strength steels and significantly affects the mechanical properties via transformation-induced plasticity (TRIP) effect. How the characteristics of retained austenite, including the volume fraction, stability, and distribution of retained austenite on the fatigue crack growth behavior is of critical importance in practical applications and needs to be explored. In this paper, typical C-Si-Mn TRIP steels were quenched at different temperatures to obtain retained austenite of different volume fractions. Higher volume fractions and higher stability of retained austenite with lower spacing are all beneficial to improving fatigue cracking resistance. The austenite of high plasticity contributes to a high fatigue crack growth threshold, and while moderate TRIP effect would generate plasticity-induced crack closure, the decrease of interfacial mismatch and local stress concentration relief step by step slow down the fatigue crack growth rate by eliminating early cracking induced by easy and abundant transformation of blocky austenite.

This paper investigates the crack propagation behavior of aluminum alloys under broadband random loading and proposes a life prediction framework based on the extended Kalman filter. The prior fatigue life model employs a frequency-domain method to calculate the stress probability density function of broadband random signals. The extended Kalman filter framework is established by integrating measurement data from the early stage of crack propagation with the prior model, aiming to reduce the uncertainties. Vibration fatigue experiments were performed to evaluate the effectiveness of the proposed approach. Comparing the model with experimental results demonstrates that the extended Kalman filter algorithm enhances the accuracy of life prediction. Through the integration of real-time health monitoring techniques, the proposed method is capable of accurately predicting crack growth life and facilitating the development of an effective maintenance strategy.

Extreme thermomechanical service conditions may induce failure of the reactor pressure vessel (RPV), potentially causing catastrophic accidents. This study presents a reduced-order peridynamics (ROPD) model to rapidly investigate thermomechanical damage behaviors of RPVs. A fully coupled thermomechanical peridynamics (PD) model is employed to overcome the limitations of mesh-based numerical methods in solving RPV fracture problems. To enhance computational efficiency, the PD governing equations are projected onto low-dimensional feature subspaces for solution, significantly reducing the degrees of freedom of the original PD system. The crack initiation and evolution of the RPV under combined thermomechanical loading are comprehensively investigated. The accuracy of ROPD is validated by comparing its results with reference solutions. ROPD achieves significant computational simplification and acceleration.

This study investigates fatigue crack initiation and propagation in nickel–aluminum bronze (NAB) single-edge notched three-point bending specimens under artificial seawater conditions based on strain gauge arrays technique. Two strain gauge configurations were designed and combined with a multilayer waterproofing strategy (conformal coating + silicone gel) to ensure stable signal acquisition in artificial seawater environments. A theoretical relationship between strain evolution and crack initiation was established, supported by test data in air. Based on these findings, a crack initiation criterion was established, revealing a characteristic “decrease-then-increase” pattern in peak strain values, which was validated against metallographic replication data. The criterion was then applied to fatigue tests in an artificial seawater environment to predict fatigue life; the accuracy of the predictions supported the effectiveness of the proposed criterion. The proposed strain-based methodology can provide a reliable solution for crack monitoring of NAB in artificial seawater environments and under the combined effect of fatigue loads. The crack initiation criterion proposed in this study needs to be verified through conducting more experiments in actual marine structures.

The dynamic high seepage pressure environment caused by reservoir storage and discharge during the operation of large-scale power stations is an important factor leading to the deterioration of rock structure and the intensification of creep deformation during excavation unloading of hydraulic bank slopes. Based on the unloaded rock mass caused by segmented excavation of reservoir bank slopes, creep tests were conducted on unloaded samples with the same unloading level under different seepage pressures. The creep mechanical properties, seepage evolution laws, and crack propagation laws and mechanisms of unloaded samples under graded loading conditions were analyzed. The one-dimensional creep model of the Hausdorff derivative was introduced and extended to a three-dimensional form. The applicability of the three-dimensional extension form of the creep model was verified by test data. Through parameter sensitivity analysis, the correlation between derivative order and damage factor with time-dependent deformation characteristics and creep stages of rock was revealed.

This study investigates the effects of aggregate gradation and freeze–thaw cycles on the fracture toughness of hot-mix asphalt (HMA) and stone mastic asphalt (SMA). Edge-notched disc bend specimens were prepared using three aggregate gradations with nominal maximum aggregate sizes (NMAS) of 19, 12.5, and 9.5 mm, and PG 64-22 binder. Fracture toughness was evaluated at −15 °C under three loading modes (I, II, and III), and the influence of 0–9 freeze–thaw cycles was examined. Results showed that increasing NMAS enhanced fracture toughness under mode I but had no significant effect under modes II and III. Freeze–thaw cycles reduced fracture toughness in both mixtures, stabilizing after the seventh cycle. SMA mixtures generally exhibited lower toughness than HMA with the same NMAS. Overall, fracture resistance was highest in mode I and lowest in mode III. The findings suggest that SMA mixtures with larger NMAS (e.g., 19 mm) can be effective alternatives to HMA in cold regions.