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ABSTRACT The time domain is the most widely chosen alternative in mechanical fatigue tests to completely represent random events. However, the main disadvantages of this approach are the long time required to complete the tests and the high cost of the complex equipment. On the other hand, fatigue test in the frequency domain is a potential alternative to overcome these disadvantages. That is, it requires less sophisticated equipment, because it uses only simple actuators instead of servo actuators. Moreover, the duration of the fatigue test is reduced, because the total length of the event is replaced by constant repetitions and constant damage. The objective of this work is to propose and develop a methodology that uses the results of structural fatigue as a starting point, and through an optimization problem solved by the genetic algorithm, it determines which loads/displacements caused them in the frequency domain. The purpose is to assist future developments in fatigue tests, supplanting tests in the time domain without losing the correlation in results. [ABSTRACT FROM AUTHOR]

Highlights Assessing the mechanical properties of CFRP and aluminum specimens exposed to hygrothermal aging is vital. Moreover, it is important to develop strategies to improve these properties. This study examines the influence of fullerene and Single‐Walled Carbon Nanotubes (SWCNT) on the fatigue life and static strength of bonded and bonded/bolted joints. The research concentrates on composite‐to‐composite and composite‐to‐aluminum substrates under three‐point bending tests, both prior to and after hygrothermal aging. The samples were classified into four groups: (1) neat specimens, (2) specimens with added fullerene, (3) specimens containing SWCNT, and (4) specimens with a blend of 50% SWCNT and 50% fullerene.The findings indicated that the optimal nanoparticle ratio for bonded joints differs from that for bonded/bolted joints. Incorporating nanoparticles into the adhesive enhanced the fatigue life of single lap joints (SLJs), particularly in samples with mixed particles and SWCNT. In some instances, nanoparticles intensified the effects of hygrothermal conditions, further increasing fatigue life. The incorporation of nanoparticles and the use of bonded/bolted joints significantly enhanced joint strength, with the combination of both yielding the best results. This study improves the understanding of aging in adhesive and hybrid joints, particularly in dissimilar configurations, and offers insights into their performance under various environmental conditions. Study examines fullerene and SWCNT impacts on CTC/CTA joint strength and fatigue. Optimal nanoparticle ratios differ for bonded and bonded/bolted joints. Nanoparticles reduce moisture absorption, aging damage, and increase failure load. Nanoparticles enhance fatigue life, varying by type, volume, load, and joint. Incorporating nanoparticles significantly improves joint strength. [ABSTRACT FROM AUTHOR]

ABSTRACT A feature transfer learning (FTL)‐based model is proposed to address small‐sample problems in fatigue life prediction of additively manufactured (AM) metals. Transfer component analysis (TCA) is studied for data alignment before model training. Correspondingly, two TCA improvement strategies are further considered to aggregate training data from distinct AM processing conditions. An experimental database consisting of 103 fatigue data is built for model evaluation. The results demonstrate that the proposed model outperforms conventional machine learning models and other transfer learning‐based models in terms of accuracy and data demand, showing good applicability for AM fatigue life assessment. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue of the journal Quality & Reliability Engineering International. The issue showcases original research presented at the 2023 International Conference on Quality, Reliability, Risk, Maintenance, and Safety Engineering. The research papers cover a diverse range of topics related to reliability and safety in modern engineering systems. The papers address areas such as reliability modeling and analysis, reliability-based design and optimization, failure/safety analysis and prevention, and maintainability. The authors express their appreciation to the journal and the reviewers for their support and hope that the research presented will be valuable to researchers, engineers, scientists, and students in the field. [Extracted from the article]

Air pollution monitoring is an important issue in environmental science. The Birnbaum–Saunders (BS) distribution, originally applied to describe product failure time distribution to fatigue failures and general random wear failures, is also well to describe the pollutant concentration data due to accumulations of various pollutants in the air over time. Sulfur dioxide (SO2) is a critical factor in air pollution. Hence, it is important to monitor its concentration variation for air pollution prevention. Due to the complexity of its distribution form, there is no reliable and easy‐to‐use control chart for monitoring pollutant concentrations based on the BS distribution. We found that the SO2 concentration data follows the BS distribution. In this study, we propose a new median control chart based on the exact sampling distribution of the monitoring statistic to detect shifts in the median of BS distribution. Thus, given the false alarm rate, the control limits for such control charts can be obtained precisely satisfying a preset in‐control average run length using Monte Carlo simulations. The out‐of‐control average run lengths are calculated by simulation to evaluate the detection performance of the proposed chart when the median shifts occur. We further compare the detection performance of the proposed chart and those of the existing control charts based on asymptotic sampling distributions. In order to improve the detection ability of the proposed chart for small median shifts, an exponentially weighted moving average (EWMA) control chart is constructed. The results of numerical analyses demonstrated that the proposed EWMA chart performs much better than all existing control charts for monitoring the median of BS distribution. Finally, the proposed control charts are applied to monitor the median of SO2 concentrations for air pollution control, showing that both charts can effectively detect a shift in the median of SO2 concentrations. The proposed EWMA control chart even detects out a small shift in the median of SO2 concentrations. The results provide a continuous monitoring solution for air pollution prevention. [ABSTRACT FROM AUTHOR]

In this paper, a reasonable explanation is given to unify notch effect and geometric size effect into notch geometric feature effect (NGFE), and energy gradient is utilized to depict the influence of the NGFE on the critical distance. The correlation of energy gradient with critical distance and fatigue life is discussed respectively. The weight index of the high energy region is used to quantify the contribution of the high energy region to the fatigue damage. Finally, a model of the reconstructed critical distance theory considering the geometric notch characteristic effect is established. The fatigue test of Q355 (D) alloy steel notched components was carried out, and the evaluation precision of the presented method is compared with Yang' model and Shen' model combining with the existing fatigue test data of En8. The results indicate that prediction results of the proposed method are consistent with the test results. Highlights: Based on the energy gradient to characterize notch geometric feature effect, the critical distance theory is reconstructed.The association degree of the energy gradient with fatigue life and critical distance is discussed.The high energy region weight index is defined to quantify the contribution of high energy region to fatigue damage. [ABSTRACT FROM AUTHOR]

With the rising importance of virtual engineering in an increasingly competitive marketplace, there is a growing need for simplified representations of finite element (FE) modeling for spot joints in lightweight structures without losing accuracy in structural life evaluation. For this purpose, this paper presents a spot weld element with an implicit weld representation and its numerical implementation as a user element for deployment in commercial FE code for reliably computing traction structural stress in a mesh‐insensitive manner. The spot weld element is formulated by degenerating conventional first‐order four‐nodes shell elements by imposing kinematic constraints with respect to a series of virtual nodes placed in the region around a spot weld. The simplicity and effectiveness of the spot weld element have been validated by comparing with the explicit weld representation for computing mesh‐insensitive structural stresses and fatigue life correlation of welded components. Highlights: A robust method is proposed to accurately determine structural stress around spot welds.A special shell element formulation is provided for implicitly modeling of spot welds.A user element subroutine of spot weld element is programmed for FEM solver.The spot weld element is validated for correlating fatigue test data [ABSTRACT FROM AUTHOR]

This work investigates the impact of temperature on the fatigue life All Aluminum Alloy Conductors (AAAC) made of 6201‐T81. A heating chamber was developed to simulate thermal effects induced by electric current passage. Wöhler fatigue curves were generated under isothermal conditions at 75 and 150°C and later compared with the one at 20°C. The conductor exhibited similar fatigue life at 20 and 75°C; however, a significant increase of life was observed for tests at 150°C. Hardness tests and failure analysis of wire breakages were carried out on samples extracted from the conductor coil and on artificially aged samples maintained at controlled temperatures. The analyses revealed that at a temperature of 150°C, there is formation of small precipitates of magnesium and silicon within the aluminum matrix, which impeded the propagation of discontinuities, increasing the material's hardness and fatigue resistance. Highlights: The designed heating chamber simulates thermal effects during fatigue tests on conductors.S‐N curves at 20, 75, and 150°C reveal enhanced conductor life at higher temps.Failure analysis present similar patterns across all temperature fatigue failures.Samples' hardness on conductor wires shows a temperature‐induced mechanical changes. [ABSTRACT FROM AUTHOR]

In this paper, a modified theory of critical distance (TCD) method (i.e., Gradient‐TCD method) is proposed, which combines fatigue parameter gradient and the TCD, to estimate fretting fatigue life of dovetail joints. The advantage of Gradient‐TCD method lies in utilizing the gradient parameters to effectively characterize the local effect zone caused by fretting, thereby enabling the determination of a suitable critical distance length independent of material fatigue parameters. The reliability and predictive capability of the method is validated through experimental results. Furthermore, this method demonstrates insensitivity to mesh size, resulting in an 83.6% reduction in computational time while maintaining the predictions within the two‐times scatter band. The novel Gradient‐TCD method may provide an efficient and reliable approach for fretting fatigue life prediction, which holds promise for evaluating complex full‐scale fretting problems. Highlights: A Gradient‐TCD method was proposed to determine the length of critical distance.The Gradient‐TCD method effectively predicts the dovetail joints fretting fatigue life.Its insensitivity to mesh size results in an 83.6% reduction in computation time.It provides a promising solution for full‐scale fretting fatigue evaluation. [ABSTRACT FROM AUTHOR]

An enhanced nonlinear fatigue damage cumulative model proposed is based on the strength degradation characteristics of composites, aiming to investigate damage progression under fatigue loading. Building upon this foundation, given the assumption of a linear correlation between fatigue cumulative damage and stress level, a methodology is presented for extrapolating the damage curve of untested stress levels from that of tested stress levels. The model substantiates its reliability by validating against experimental data from several distinct material types. The reliability of the model has been validated using experimental data from multiple groups of materials. The experimental results indicate that the model can effectively reflect the fatigue damage development characteristics of composite materials. Simultaneously, the predicted stress levels derived from the proposed methodology show lesser deviation from the fitted data. Finally, a life prediction method founded on the proposed model is introduced, validated for its high prediction accuracy through experimentation. Highlights: An enhanced fatigue damage model of composites is established.A novel residual strength model for composites has been established.Present a methodology for calculating the stress level damage curve.The fatigue life prediction method of the proposed model is developed. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) has revolutionized the production industry by offering design freedom with shorter lead times and reduced material wastage. However, the damage tolerance (DT) of AM parts is a significant concern due to their microstructural and geometric complexities, which affect their mechanical performance. This article aims to provide a comprehensive overview of the manufacturing parameters affecting the components produced by AM specifically selective laser melting (SLM). Detailed discussions are presented on the effects of manufacturing attributes on the microstructure, defects, and mechanical characteristics of AM parts. Depending on these aspects, basic concepts are studied and critically explained specifically for AM materials. The basic criterion for damage‐tolerant component design, the criterion for fatigue and fracture properties, and the effect of the defects on fatigue life are critically presented. In addition, the effect of different types of gradation on the crack growth behavior of samples processed by SLM is also investigated in depth. There is currently a lack of a specific review study in the literature that establishes a connection between process attributes and metallographic properties, and their impact on the damage behavior of additively manufactured parts. This gap in research highlights the need for a comprehensive review to bridge this knowledge deficit and provide valuable insights for understanding the relationships between manufacturing processes, material characteristics, and the structural integrity of additively manufactured components. This review concludes by addressing the challenges and opportunities in designing and qualifying AM parts for damage tolerance. [ABSTRACT FROM AUTHOR]

ABSTRACT Aiming at the issue of fatigue test data for large‐scale mechanical components of building steel are very limited, a method for fitting P‐S‐N curves under small sample data of notched specimens is proposed to predict fatigue life. First, a fatigue life subsample augmented and its reliability assessment method are established, based on Bayesian hierarchical modeling and modified Monte Carlo method. Second, a clustering combination weighting method is proposed, to define weights of hidden variables of the binomial mixture Weibull distribution, and the expectation–maximization algorithm is used to determine probability density function of the distribution. Finally, the P‐S‐N curves under various failure probabilities are fitted with Weibull distributed life models, and the convergence and prediction accuracy of the different models are compared. The results show that the fatigue data of small samples can be predicted better by using mixed Weibull distribution, and the fitting P‐S‐N curve is more reliable and accurate. [ABSTRACT FROM AUTHOR]

ABSTRACT This study presents a procedure based on constant amplitude (CA) fatigue data to predict the statistical fatigue lifetime of glass/orthopolyester composites subjected to repeated ordered and random two, three, and six sequences of block loadings. A numerical routine was developed to detect cycle‐by‐cycle the statistical strength degradation progression until failure, assuming that the strength at the end of a block cycle equals the strength at the start of the successive one and that the individual samples' static strength, the amount of degraded strength, and fatigue life share the same rank in their respective cumulative distribution function. Predictions conform to the statistically undetectable loading sequence effects and lightly overestimate the lifetimes of random and ordered high‐to‐low (1/100 cycles) repeated two‐block loadings. The vanishing effect of the loading sequence when the block extents remain fixed, the block extent effects for a given three‐block sequence, and the lifetimes of three‐block loadings were fully predicted. The six‐block sequence's experimental lifetimes with different block loading orders and block extent fell within the predicted lifetimes' cumulative distribution function. A reliable damage rule based on residual strength was proposed and compared to the Miner's rule. [ABSTRACT FROM AUTHOR]

ABSTRACT The milled surface of TC4 titanium alloy was treated by laser shock peening (LSP) and laser shock wave planishing (LSWP) to investigate the effect of compressive residual stress (CRS) and surface roughness (SR) on the vibration fatigue performance. The results demonstrate that although the amplitude of CRS induced by LSWP is lower than that of LSPed specimens, the vibration fatigue life of LSWPed specimens increased by 63.78% due to a significant reduction in SR from Sa 14.1 μm to Sa 4.21 μm. When the SR is low, increasing the amplitude of CRS is more advantageous to enhance fatigue life. The fractographic analysis further confirmed that compared with LSPed and T0.2‐LSWPed specimens, T0.1‐LSWPed specimens have considerably less initial fatigue crack initiation, and the crack initiation location is deeper. The fatigue striation spacing of T0.1‐LSWPed specimens is the smallest (0.25 μm), greatly lowering the fatigue crack growth rate. [ABSTRACT FROM AUTHOR]

ABSTRACT Accurately and efficiently predicting the fatigue life of rubber materials has been a long‐standing challenge due to limited understanding of the fatigue mechanism. In this study, a variational assimilation‐based machine learning method assisted with incremental crack propagation model is proposed to predict the fatigue life of rubber materials. Firstly, according to the fracture mechanics theory, a new rubber fatigue life prediction model based on incremental crack propagation and sparse experimental data is established, which owns higher accuracy than the classical crack energy density model. Further, a rubber fatigue life solver coupled incremental crack propagation model and nonlinear finite element method is introduced to generate a dense fatigue life dataset of rubber materials with high accuracy. Finally, the artificial neural network model is trained, cross‐validated, and tested using the dense dataset, and the three‐dimensional variational assimilation model is employed to merge the predicted values of artificial neural network with experimental data. By comparing against the experimental data, the effectiveness of the proposed method was verified; thereby, we offer an accurate and efficient approach to predict the rubber fatigue life. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper assesses the impact of utilizing statistically defined residual stress fields from cold expansion (Cx) in linear elastic, multi‐point fracture mechanics analyses using the spatial analysis of residual stress (SpARS) methodology. There is significant value and interest in leveraging the increased fatigue life afforded by Cx, but it is imperative to quantify the variability of the residual stress to understand the expected variability in benefit due to Cx. Comparisons of the predicted fatigue lives from SpARS‐produced statistical residual stress fields are made to fatigue test data. Results demonstrated that the less compressive 95% upper bound from the mean residual stress would be a reasonable strategy as it supplies a compromise between safety and inherent material and process variability while still producing a sizable improvement in predicted fatigue life. In this study, using SpARS to incorporate statistically representative residual stress fields in fatigue crack growth analyses demonstrates a methodology to aircraft structural engineers for improved fleet management and allow increased aircraft availability through fewer inspections. [ABSTRACT FROM AUTHOR]

ABSTRACT X‐ray computed tomography (XCT) is extremely useful for the non‐destructive analysis of additively manufactured (AM) components. AM components often show manufacturing defects such as lack‐of‐fusion (LoF), which are detrimental to the fatigue life of components. To better understand how cracks initiate and propagate from internal defects, we fabricated Ti‐6Al‐4V samples with an internal cavity using electron beam powder bed fusion. The samples were tested in high‐cycle and very high‐cycle fatigue regimes. XCT was used to locate crack initiation sites and to determine characteristic properties of cracks and defects with the aid of deep learning segmentation. LoF defects exposed to the outer surface of the samples after machining were found to be as detrimental to fatigue life as the internal artificial defects. This work can benefit industries that utilize the AM of high‐strength, lightweight alloys, in the design and manufacturing of components to improve part reliability and fatigue life. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigated the fatigue fracture mechanisms and life prediction of clinched joints made from titanium alloy TA1. The fatigue tests revealed that TA1 titanium alloy clinched joints exhibited failure characterized by fracture of the lower plate at three distinct fatigue load levels. Additionally, finite element analysis indicated that cold work hardening enhanced the fatigue performance of these joints. Observations of fracture surfaces using scanning electron microscopy identified the crack source and its propagation path, which correlated with the location of maximum principal stress from the finite element simulations. Fretting wear was also observed in this critical region. Furthermore, fatigue life predictions for TA1 titanium alloy clinched joints were made using Paris' law and the local strain approach. Both methods closely matched experimental results across different fatigue life intervals. Overall, the local strain approach exhibited superior predictive capability compared to Paris' law, taking into account various influencing factors. [ABSTRACT FROM AUTHOR]

ABSTRACT When a structure is randomly excited by its installation base, significant vibration stress may be caused within it, thus causing damage to the structure. The authors find in the vibration fatigue test that when the notched slender beam specimen is excited by stationary Gaussian random base movement, the measured acceleration response and strain response of the specimen have obvious nonstationary characteristics. The vibration responses of the specimen under Gaussian and non‐Gaussian random base excitations are calculated by the finite element method and corresponding vibration fatigue tests were completed. The nonstationary characteristics of the responses from calculations and experiments are analyzed. Finally, a method for calculating the fatigue life of the specimen under nonstationary response is given, and the calculated results are compared with the measured data. The results indicate that the method proposed in this article performed excellent calculation fatigue life with measured strain data. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, the low‐cycle fatigue fracture behavior and life prediction of Cr–Ni–Mo–V gun steel at room temperature and 600 °C are studied. The results indicated that at room temperature and 600 °C, the Cr–Ni–Mo–V gun steel exhibited obvious monotonic softening and cyclic softening. This behavior could be attributed to the formation of dislocation networks, dislocation walls, dynamic recovery, and dynamic recrystallization. As the temperature increased, the failure mode gradually shifted from mixed transgranular and intergranular fractures to intergranular fractures possibly owing to the reduced grain boundary strength and easy oxidation of the grain boundary at high temperatures. In addition, the fatigue life prediction model considering the influence of temperature is established by using the energy dissipation quadratic function, offering a practical method to improve the fatigue performance evaluation of Cr–Ni–Mo–V gun steel at various temperature. [ABSTRACT FROM AUTHOR]

ABSTRACT To investigate fatigue life of the two‐layered Ti‐6Al‐4V alloys with additively manufactured layer and conventional wrought layer, fatigue tests were conducted under constant amplitude loading. The effect of post heat treatment on fatigue life was also examined. Three types of specimens were used as test materials: specimens without heat treatment (As‐built material), specimens with solution aging treatment (STA), and specimens with heat treatment (1100AC). Compared at the same stress amplitude, there was a tendency that STA material has a longer fatigue life because of the lower initial stress of STA specimens at the attachment of the fatigue testing machine. However, As‐built material had the longest and 1100AC material had the shortest fatigue lives compared at the same σswt. And a comparison of the fatigue limits showed that As‐built and STA materials have almost the same values. [ABSTRACT FROM AUTHOR]

Highlights The CFRP/Ti multi‐bolt joints are commonly used in important structural parts of aircraft. These structure often adopts an integrated drilling method to improve manufacturing efficiency and avoid assembly problems. However, significant differences in material properties between CFRP and titanium alloy can affect hole accuracy, leading to deviations in hole‐size that impact joint performance. In response to these challenges, this study conducted experiments on the hole‐making process for CFRP/Ti laminated multi‐bolt joints and analyzed hole‐size characteristics and precision. The research investigated the effect of hole‐making processes on the static tensile and fatigue performance of CFRP/Ti three‐bolt single‐lap joints specimens and revealed the influence of hole‐size characteristics on load distribution among bolts. Results indicated that titanium alloy chip formation during CFRP hole drilling induced a microcutting effect on CFRP hole walls, resulting in stepped holes. The use of low‐frequency vibration‐assisted drilling improved chip removal and enhanced hole‐making precision. The use of the LDR‐LDR‐CD combined hole‐making process can mitigate the secondary bending phenomenon of critical bolt in CFRP/Ti three‐bolt, single‐lap joints specimens, thereby reducing local stress concentrations. This process combination effectively distributes bolt loads evenly, resulting in a reduction of the bolt load ratio in critical holes by 6.2%, and increases ultimate load and fatigue life by 6.7% and 47.7%, respectively. Therefore, in the hole‐making process of CFRP/Ti multi‐bolt joints, it is crucial to ensure that the precision of critical holes is lower than that of auxiliary holes to decrease the bolt load ratio in critical holes and enhance structural joint performance. Novel method for uniformly distributing load based on controlling drilling precision. The formation process of CFRP/Ti hole diameter characteristics in different processes. The LDR‐LDR‐CD can optimize load distribution, improve ultimate load and fatigue life. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper evaluates the capability of the theory of critical distances (TCD) coupled with the Fatemi–Socie (FS), Smith–Watson–Topper (SWT), and normal stress range (S‐N) criteria for the lifetime estimation of combined fretting fatigue, that is, the combination of bending and axial loading modes, for 316L stainless steel along with the effect of increasing the grain size of the material. After evaluating the stress field, the point, line, area, and volume methods have been implemented to estimate the lifetimes of fretting fatigue experiments based on the dependency of the critical distance on the number of cycles to failure. Whereas the area and volume methods were overestimating the lifetimes, the point and line methods were more accurate. FS and SWT criteria were proper in lifetime estimation, but the normal stress range (S‐N) criterion was not a safe criterion. At the same time, increasing the grain size of the material leads the TCD to be more conservative. [ABSTRACT FROM AUTHOR]

The electromagnetic force dynamic installation (DI) method of interference fit fasteners has significant advantages in improving the quality of the assembly interface of composite structure. This study aims to investigate how improving assembly interface quality may help in achieving high‐precision interference‐fit joints in composites. Single‐lap joint specimens were prepared using electromagnetic installation technique, the fatigue life and failure behaviors of the joints under different bolt‐hole clearances were measured and analyzed experimentally. In addition, a three‐dimensional finite element model was developed to predict the radial pre‐compression stresses around the hole and the progressive failure behavior of various typical damage modes in carbon fiber‐reinforced polymer induced by the interference. The results show that the critical interference range for the DI‐composite bolted structure is 1.0%–1.2%. The fatigue life of the best interference (1.0%) and the worst interference (0%, neat fit) have a difference of 36 times in amplitude. The residual stress with uniform distribution and high amplitude reduces the stress concentration of the hole wall and improves the failure evolution of the loaded hole. The contribution of this study provides vital guidance for improving the fatigue performance of CFRP bolted structures using a novel DI method. Highlights: I = 1.0% is the critical damage‐enhancing interference size for dynamically installation interference fit bolts with electromagnetic forces.The residual stress amplitude introduced by the interference does not increase uniformly as the interference size increases. Excessive interference significantly reduces the uniformity and magnitude of residual stresses.Under subsequent cyclic loading, the fifth layer near the inlet and outlet of the extruded lower laminate appears to be the critical ply of extrusion deformation, and severe damage is concentrated in the critical ply of deformation.The decrease of stress amplitude and the variation of mean stress are the mechanisms of fatigue life enhancement in interference fit joints under external cyclic loading. [ABSTRACT FROM AUTHOR]

The load history exerts a considerable impact on the low cycle fatigue (LCF) life of turbine discs. Thus, oversimplifying the load history leads to substantial errors in fatigue life prediction. This study introduces a probabilistic fatigue life prediction method for turbine discs, accounting for the randomness inherent in LCF load history. The method involves quantifying the randomness of load history through numerical simulation and employing a surrogate model enhanced with learning functions to balance computational efficiency and accuracy. The probabilistic LCF life prediction of full‐scale turbine disc was conducted, demonstrating that the fatigue life scatter predicted by the proposed method more closely aligns with experimental data compared to the original approach. By refining the numerical simulation process, the proposed method better accounts for uncertainties in load history while maintaining computational efficiency, offering significant insights for the fatigue reliability design of turbine discs. [ABSTRACT FROM AUTHOR]

The effect of shot peening (SP) on pre‐fatigue tested carburized steel was investigated. Plane‐bending fatigue tests were conducted on carburized CrMo steel that was pre‐fatigue tested and treated with SP. Fatigue cracks were induced by pre‐fatigue tests with a stress amplitude of σa = 1000 MPa, and the number of the pre‐fatigue test cycles was 2.0 × 104 (L5 test) and 4.0 × 104 (L15 test). We compared the fatigue lives of the fatigue‐damaged and smooth specimens without fatigue damage treated with the same SP. The fatigue life of the L5 tested specimens with SP was longer than that of the non‐fatigue damaged smooth specimens after SP. Therefore, the fatigue cracks introduced by the L5 test can be rendered harmless by SP. Furthermore, near‐surface material properties were evaluated and the mechanisms of rendering surface cracks harmless were investigated. HIGHLIGHTS: (1) Fatigue cracks were induced by pre‐fatigue tests on carburized CrMo steel. (2) The fatigue cracks could be rendered harmless by shot peening. (3) The mechanisms of rendering surface cracks harmless were investigated. (4) Shot peening is expected to be utilized in remanufacturing. [ABSTRACT FROM AUTHOR]

Aluminum‐lithium alloys are a class of advanced materials designed to reduce weight and improve performance in aerospace and other high‐tech applications. This paper presents a research investigation on the in‐phase and out‐of‐phase multiaxial fatigue behaviors of the third‐generation AW2099‐T83 aluminum‐lithium alloy that have not been addressed before. Additional hardening was observed under nonproportional loading condition at high strain amplitudes. Fatigue lives were estimated using von Mises equivalent strain and two critical plane models: the Fatemi‐Socie (FS) and the Smith‐Watson‐Topper (SWT). In addition, a supervised machine‐learning model (support vector machine—SVM) was employed to predict the fatigue life under the above‐mentioned loading conditions. The FS criterion was found to yield better fatigue life predictions than SWT. The estimations of FS model mostly fall within ±3× scatter bands with some data falling within the conservative and non‐conservative regions. The SVM model resulted in excellent predictions within ±2× scatter bands. Highlights: An experimental program was performed to investigate the behavior of aluminum lithium alloy AW2099‐T83 under strain‐controlled, in‐phase (IP), and 90° out‐of‐phase (OP), multiaxial fatigue loading.Fatigue life variation with different combinations of axial and shear strains and loading phase angles was determined.The material exhibited additional hardening under 90° OP loading.Fatemi‐Socie model was found to consolidate fatigue life curves in narrower scatter bands than Smith‐Watson and Topper model, while machine learning SVM‐predicted results were in good agreement with experimental results. [ABSTRACT FROM AUTHOR]

In this study, the fatigue behavior of FDM‐3D printed polylactic acid (PLA) materials was investigated by rotary bending fatigue tests and finite element studies with varying printing speed and raster angle parameters. Fatigue test specimens were manufactured at five different raster angles (0°, 30°, 45°, 60°, and 90°) and two different printing speeds (20 and 80 mm/s). The effect of printing speed was evaluated at high print speed variation range (20 and 80 mm/s print speeds). It was noticed that the change in raster angle affects the fatigue life very significantly. The highest fatigue life was obtained at 30° raster angle, while the lowest fatigue life was found at 90° raster angle. Increasing the printing speed from 20 to 80 mm/s decreased the fatigue life of all specimens. The derived results from the finite element analyses were consistent with the experimental results. Highlights: The fatigue behavior of 3D printed polylactic acid (PLA) materials was examined by rotary bending fatigue tests and FEAs with different printing speed and raster angle parameters.Fatigue test specimens were manufactured at five different raster angles (0°, 30°, 45°, 60°, and 90°) and two different printing speeds (20 and 80 mm/s).The highest fatigue life was achieved at 30° raster angle, while the lowest fatigue life was found at 90° raster angle.Increasing the printing speed from 20 to 80 mm/s decreased the fatigue life of all specimens. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method based on a numerical simulation approach and fatigue fracture theory to analyze the fracture behavior and assess the fatigue life of spring clips. To this end, the finite element (FE) model of the vehicle‐track‐foundation system was developed including the key parts of the type II fastening system. Meanwhile, the spring clip FE model was validated through the natural vibration characteristics. Subsequently, the numerical simulations were performed under various working conditions to obtain the fatigue characteristics of the spring clips. The fatigue crack initiation life and damage were analyzed using FE results for the spring clips with ε‐N curve and Brown‐Miller criterion. Moreover, based on the initial crack geometry of the spring clips, the maximum circumferential stress criterion with the Paris equation was employed to analyze the crack extension behavior and assess the fatigue crack extension life. Highlights: A novel approach is developed for fatigue assessment of spring clip.A FE model of vehicle‐track‐foundation system was built including fastening system.The Fracture behavior of the spring clip was reproduced.Fatigue characteristic of spring clips subjected to axle load is studied. [ABSTRACT FROM AUTHOR]

This study proposes a novel method to prevent fatigue cracks at the root of fillet welds in steel bridge supports by inserting epoxy resin as an adhesive material. A total of 36 specimens, categorized into welded‐only and bonding‐assisted types, were subjected to a series of four‐point bending fatigue tests to simulate cyclic tensile stress conditions. Additionally, finite element analysis was employed to investigate the impact of epoxy insertion on stress distribution near the weld root. The results demonstrated that bonding‐assisted specimens exhibited significantly improved fatigue life compared to welded‐only specimens, with a notable reduction in tensile stress at the weld root. Furthermore, a displacement‐based method was employed to evaluate weld root fatigue performance, yielding consistent results. These findings highlight the potential of integrating adhesive bonding in fillet welds to improve the durability and service life of steel bridge structures by effectively mitigating fatigue‐related issues. Highlights: Preventing fatigue cracks in fillet weld root through epoxy insertion.Inserted rubber prevents welding defects caused by epoxy burning during welding.The combination of welding and bonding reduces the opening displacement of the weld root.Displacement‐based method can effectively evaluate weld root fatigue life. [ABSTRACT FROM AUTHOR]

To assess the contribution of residual stress to the improvement of high‐cycle fatigue (HCF) properties, HCF tests are performed on Ti‐6Al‐4V specimens with different residual stress levels but no other evident surface state modification induced by machining. Results indicate that compressive residual stress induced by machining significantly improves the HCF performance of Ti‐6Al‐4V specimens. Of all the specimens, the fatigue strength of specimens with a surface residual stress level of −400 MPa is increased by approximately 16.4%. Furthermore, to accurately predict the fatigue life based on three mean stress correction equations (e.g., Walker, Goodman, and Smith–Watson–Topper), the method of reducing surface residual stress by a reduction factor and then adding to the mean stress is proposed. A reduction factor of 0.55 is found to be appropriate for the alloy under the test condition, with majority of the predicted data falling within a factor of three scatter band. Highlights: Isolate residual stress from other surface integrity parameters by machining.Compressive residual stress improves both the fatigue life and strength.Effect of residual stress is considered by introducing a reduction factor in mean stress.Develop a life prediction method based on mean stress correction model. [ABSTRACT FROM AUTHOR]

We performed rotating bending tests and axial (tension‐compression) load‐increase and constant amplitude high‐cycle fatigue tests in air and Hanks' balanced salt solution (HBSS) on the β‐metastable titanium alloy Ti‐5Al‐5Mo‐5V‐3Cr, processed by laser powder bed fusion (LPBF‐M), solution‐treated and aged, and shot‐peened. Rotating bending loading in air revealed a strong influence of process‐induced flaws on fatigue endurance. Especially in the high‐cycle fatigue range and the transition region, the stochastic distribution of the flaws and flaw sizes led to a high scatter of the number of cycles to failure. The axial load‐increase tests yielded a good fatigue life estimation, with a negligible difference between air and HBSS. The cyclic deformation behavior in HBSS was also strongly influenced by the local microstructure and defect distribution, and, thus, by crack formation and propagation. Plastic deformation and microcrack growth interact, and their relative amount resulted in different progressions of the plastic strain amplitude over the number of cycles for different specimens. Changes in the free corrosion potential and the corrosion current were highly sensitive indicators for fatigue‐induced damage on the rough surfaces, which was correlated to the microscopic examination, fracture surface features, and the fatigue crack development. Highlights: Failure starts at stochastically distributed inner flaws, yielding high scatter of Nf.Cyclic deformation behavior in HBSS depends on local microstructure and flaws.Simultaneous plastic deformation and microcrack growth influence εa,p levels.Microscopy, electrochemistry, and surface fracture illustrate fatigue crack development. [ABSTRACT FROM AUTHOR]

Welded components are highly vulnerable to fatigue failures due to stress concentrations and material imperfections. This study develops an analytical framework that predicts both high‐cycle (HCF) and low‐cycle (LCF) fatigue lives of welded joints using a structural strain parameter. By employing a linear hardening model, the method effectively translates structural stress into structural strain, providing a reliable metric for assessing fatigue life, especially in LCF conditions. Validated against experimental data from 62 longitudinal gusset joints, the approach proves both reliable and practical. This simplified method facilitates easier fatigue assessments, encouraging its wider use and potential standardization in engineering, thus improving the predictability of welded structures' performance. Highlights: An analytical framework is presented to assess the fatigue behavior of welded structures.The linear hardening law is introduced to capture the material hardening behavior.The analytical solutions for plane stress and plane strain conditions are provided.The method is applied to analyze 62 weldment fatigue data in both HCF and LCF regime. [ABSTRACT FROM AUTHOR]

Random meso‐scale defects within welded joints can affect the structural damage process and cause dispersion in the fatigue lifetime of welded joints. In this paper, a meso‐scale stochastic damage approach is used to investigate the effect of random, meso‐scale defects on the fatigue damage lifetime of welded joints under different loads. First, we established an elastic–plastic fatigue damage model considering meso‐defects in the weld metal. Secondly, the fatigue lifetimes for gas tungsten arc welding and gas metal arc welding welded joints were predicted, with most of the predictions within the twofold dispersion factor. Thirdly, the Monte Carlo simulation method was used to investigate the influence of meso‐defect size on the fatigue lifetime dispersion degree, and the fatigue lifetime distribution under different loads was statistically analyzed. Established a fatigue life prediction model considering random meso‐defects in welds.The dispersion effect of meso‐scale random defect size on fatigue life was analyzed.Fatigue life prediction of welded specimens of other materials is also possible. [ABSTRACT FROM AUTHOR]

Digital data management for maintenance in offshore wind farms The DiMoWind‐Inspect research project explored the essential requirements for implementing digital methods in the maintenance of offshore wind turbines. Currently, data from all stages of the turbines' lifecycles are underutilized, leading to suboptimal maintenance actions being taken in terms of location, timing, and cost. A consistent structuring of previously often unstructured construction and maintenance data developed in the project enables their cross‐disciplinary, user‐specific availability. To accomplish this, the principles of the Reference Designation System for Power Plants RDS‐PP are applied. In this way, additional information, such as maintenance measures or defects, can be structured alongside components. The components of the structures are directly linked with information from inspections and other maintenance activities, following the Building Information Modeling approach. This allows for processing operational information about the condition of the structure and providing it for relevant calculations and assessments. As a use case, a two‐stage concept is presented, utilizing maintenance information to assess the fatigue life of a corrosion‐damaged structural detail in the support structure of an offshore wind turbine. [ABSTRACT FROM AUTHOR]

The addition of graphene nanoplatelets as a nanofiller on the surface of pristine and oxidized carbon fiber for making reinforced polymer composites has shown improvement in monotonic flexural properties. However, the fatigue response of these laminates under bending loads has not been investigated so far. The current study aims to examine the monotonic and fatigue behavior of the graphene nanoplatelets (GNPs) coated bi‐directional pristine and oxidized carbon fiber epoxy composites under bending loads. Eight layers of fabrics were used to manufacture the laminates through vacuum‐assisted resin transfer molding technique (VARTM). An optimum amount of GNP addition on oxidized fiber leads to ~830‐fold enhanced fatigue life at higher stresses as compared to pristine laminates. However, excessive GNP addition on pristine as well as oxidized fiber leads to a deterioration in fatigue life. In‐situ optical microscopic examination was done to observe the crack initiation and propagation of all the specimens with respect to the number of cycles coupled with post‐mortem SEM images of the fracture surfaces. [ABSTRACT FROM AUTHOR]

Despite ensuring the integrity of bogie frames for railway vehicles via nondestructive inspections during periodic maintenance, the possibility of fatigue cracks occurring at locations other than the predetermined inspection points cannot be dismissed. Therefore, fatigue cracks can be prevented more efficiently by assessing the overall degree of fatigue damage to the entire bogie frame and determining the results via nondestructive inspections. In this study, dynamic stresses in the bogie frame during running were estimated via finite element dynamic analysis by using the axle box acceleration as input, and the degree of fatigue damage and life were calculated from the waveform of the estimated stresses. Furthermore, we developed a bogie frame fatigue prediction system based on a high‐speed and high‐precision stress calculation method. The developed system visualized the overall relative life. [ABSTRACT FROM AUTHOR]

316 Austenitic stainless steel (AusSS) is extensively utilized in high‐temperature industrial applications such as boiler tubes and nuclear reactor pressure vessels. These components commonly experience failure under high‐temperature and high‐pressure conditions, attributed to either creep or fatigue. Existing classical models for creep and fatigue life prediction focus on a singular failure mode (either creep or fatigue) and consider physical features only. This study aims to develop a unified life prediction model for both creep and fatigue phenomena. It synthesizes information from 12 additional unexplored chemical and microstructural features from the National Institute of Materials Science (NIMS), Japan database, and previously published literature. Machine learning (such as decision tree, random forest, and XGBoost) and deep learning (like deep neural network) algorithms are employed in the modeling process. The trained models have been cross‐validated against unseen creep and fatigue life data, demonstrating superior prediction accuracy of 96.1% for deep neural network compared with classical models. Highlights: Unified prediction model for both creep and fatigue life prediction.Investigated the effect of up to 20 physical, chemical, and microstructural features.Multiple ML and DL prediction models were developed and compared with classical ones. [ABSTRACT FROM AUTHOR]

This research aims to detect and analyze critical internal and surface defects in metal components manufactured by powder bed fusion of metals using a laser beam (PBF‐LB/M). The aim is to assess their impact on the fatigue behavior. Therefore, a combination of methods, including image processing of micro‐computed tomography (μCT) scans, fatigue testing, and machine learning, was applied. A workflow was established to contribute to the nondestructive assessment of component quality and mechanical properties. Additionally, this study illustrates the application of machine learning to address a classification problem, specifically the categorization of pores into gas pores and lack of fusion pores. Although it was shown that internal defects exhibited a reduced impact on fatigue behavior compared with surface defects, it was noted that surface defects exert a higher influence on fatigue behavior. A machine learning algorithm was developed to predict the fatigue life using surface defect features as input parameters. Highlights: Established workflow for extracting surface and internal features.Developed pore classification ML algorithm with 92.4% accuracy.Effectively developed ML algorithm for predicting fatigue life. [ABSTRACT FROM AUTHOR]

To accurately evaluate the fatigue performance of a full‐scale deep‐water steel catenary riser (SCR) using small‐size specimens, six fatigue testing strategies were explored, considering the effect of welding residual stress. Through a comparison with the full‐scale resonant bending fatigue testing results, the most equivalent strategy using small‐scale specimens was identified. The results indicate that the test strategies applying constant stress underestimated the fatigue life, compared with that of a full‐scale specimen; meanwhile, fatigue life values obtained from the low‐stress ratio testing strategy were higher, particularly in the low‐stress range region. Comparatively, the fatigue lives obtained for the 100 mm‐wide specimens without cutting were higher in the high‐stress range region. The variable‐applied mean stress strategy using the 25 mm‐wide welded joint specimen was the most suitable for equivalence with the full‐scale fatigue testing, with only a 9.7% difference in the fatigue life testing results. The difference between the applied mean stress and the actual transverse welding residual stress under various fatigue testing strategies is the key factor affecting the equivalence of the fatigue testing results. Highlights: Fatigue testing results between the full‐scale and small‐scale pipeline welded joint specimens were compared.Six types of fatigue testing strategies were systematically explored using small‐scale welded joints properly.The variable mean stress fatigue testing strategy was proposed, and its equivalency with the full‐scale pipeline joint was confirmed.Mechanisms on the difference of fatigue testing results between full‐scale and small‐scale pipeline joints were analyzed. [ABSTRACT FROM AUTHOR]

This review explores uniaxial ultrasonic fatigue (USF) testing as a common and dependable method for quantifying the extended fatigue life of fiber‐reinforced polymer (FRP) composites. The objective is to explain the complexities governing the fatigue life behavior of FRPs, particularly in the realm of very high cycle fatigue (VHCF) where the number of loading cycles exceeds 107. To this end, this review encompasses the analysis of VHCF behavior, including the derivation and interpretation of stress–life (S–N) data, the evaluation of various fatigue damage mechanisms (i.e., controlling mechanisms of crack initiation and propagation) exhibited in FRP composites, and a thorough investigation of the frequency‐dependent effects on fatigue responses. Furthermore, this review tries to analyze the microscopic intricacies intrinsic to the VHCF failure of FRP composites, encompassing aspects such as fiber‐matrix de‐bonding, matrix cracking, and delamination, unveiling their modes and effects in a detailed manner. This review also underscores the pivotal integration of simulations, machine learning, and modeling techniques, emphasizing their crucial role in explaining both macroscopic and microscopic interactions governing the VHCF of FRPs. Highlights: CFRPs' very high cycle fatigue (VHCF) is poorly understood but critical in many sectors.Testing CFRPs' VHCF using ultrasonic fatigue (USF) addresses long, complex procedures.Environment‐dependent USF testing shows how conditions like corrosion impact CFRPs.Advanced modeling and machine learning enhance understanding of CFRPs' VHCF behavior. [ABSTRACT FROM AUTHOR]

Fatigue‐induced clip fractures are the most common type of damage in railway systems, and they are exacerbated by rail corrugation. This research investigated the development of rail corrugation through long‐term measurements and examined the impact of rail corrugation on the fatigue life of e‐clips using a finite element model. The examination included different corrugation wavelengths, namely, short‐pitch corrugation (SPC), long‐pitch corrugation (LPC), and a new form of corrugation called superposed SPC and LPC. The results showed that increasing corrugation amplitude reduces an e‐clip's fatigue life and alters the region in the clip where fatigue damage occurs. A short corrugation wavelength shortens fatigue life. On railway tracks with superposed SPC and LPC, a significant increase in LPC amplitude sharply reduces a clip's fatigue life, even under minuscule SPC amplitude. Effective measures are proposed to prolong the fatigue life of e‐clips subjected to the effects of rail corrugation. Highlights: Studying the impact of three types of rail corrugation on e‐clip's fatigue life.Long‐term tracking investigation on rail corrugation and fastening system failures.Two measures for prolonging e‐clip's fatigue life were proposed.Establishment and verification of the whole solid‐element wheel–track system model. [ABSTRACT FROM AUTHOR]

The exploitation of fatigue life prediction methods based on fatigue indicator parameters revealed the influence of the defect size, position, and morphology on the fatigue life and fatigue behavior of additively manufactured metals. Meanwhile, Data‐driven life prediction methods are time‐efficient but inexplainable. Current machine learning‐based fatigue life prediction methods call for not only the accuracy but also the interpretability and stability of prediction results. Thus, the fusion of physical methods and machine learning methods has been a prevailing research topic in fatigue life prediction. In this study, a novel physics‐informed neural network framework is proposed by integrating a fatigue indicator parameter based on defects into the physical constraints term of a loss function. This method outperforms conventional machine learning methods in high‐cycle and very high‐cycle regimes, exhibiting superior prediction performance and generalization ability. Furthermore, the prediction results can be explained from a physical standpoint, correlating with the applicability range of the introduced physical equation describing defect positions. Highlights: A novel machine learning framework integrating a fatigue index parameter is proposed.The physics‐informed neural network has the best fatigue life prediction results.The prediction can be partially interpreted by the introduced physical model. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the failure mechanism of Ti60 titanium alloy in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) at 500°C. Ti60 specimens were characterized before and after the 500°C VHCF test, and the fracture surfaces were observed. The results show that there are three different fatigue failure mechanisms at 500°C: (i) equiaxed primary α phase (αp) cleavage, forming small unsmooth facets and rough fracture area (RA), and fusion of non‐adjacent facets to grow into the main crack. (ii) αp grains gather into large grain with triple junction, and large grain slip to form large fusion facet. (iii) Oxide shedding and then cracks form. A dynamic recurrent neural network model is used to predict the fatigue life of Ti60 alloy, 91% of the overall predictions were within the scatter band of 3.0, and 100% were within the scatter band of 5.0. Highlights: Characterization yields three fatigue fracture mechanisms of Ti60 alloy at 500°C.Haigh diagrams evaluate the empirical formulas and constant life curves.Characterization reveals multiple triple junctions within the large αp grains after fatigue test.A dynamic recurrent neural network model predicts the fatigue life. [ABSTRACT FROM AUTHOR]

There is a growing number of welded steel bridges in the world that are reaching the end of their design life. Repair of fatigue damage (cracks) or replacement with new modern designs is becoming an increasing issue. Fatigue damage is now one of the main design and construction risks associated with the construction of new dynamically stressed steel structures. Fatigue damage is now one of the main design and engineering risks associated with the construction of new dynamically stressed steel structures. Increasing fatigue life can be achieved by HFMI treatment that can be applied to new weld as well as existing welded joints. This paper presents the results of experiments focused on HFMI treatment to new and repaired butt welds of higher thicknesses. [ABSTRACT FROM AUTHOR]

Nickel aluminum bronze (NAB) is a complex alloy used extensively in the marine environment. Fatigue strength of NAB is reduced by welding and prior seawater corrosion. This study investigated the combined effect of corrosion and plasma welding on the fatigue behavior of NAB. Natural seawater corroded samples were used in tension‐tension cyclic loading tests to observe fatigue crack initiation, propagation, and failure. Fatigue cracks initiated from corrosion pits at the weld toe. Stress corrosion and fatigue cracks propagated along the path of β′ and κIII phases. A short crack growth model (SCGM) predicted fatigue strength using experimentally obtained material properties and corrosion pit dimensions. Model predictions were used to develop S‐N curves and were within 30% of experimental results. The SCGM produced accurate and reliable fatigue life results that could be applied by industry to aid in revalidation decision making and inspection scheduling. [ABSTRACT FROM AUTHOR]

The effects of vibratory peening (VP), shot peening (SP), and SP followed by vibratory finishing (SPVF) on the surface and fatigue properties of Ti‐6Al‐4 V were compared to conventional low‐stress grinding (LSG). VP processing produced seven times smoother surface finish than SP and 66% deeper compressive residual stresses (CRS) but with 12% lower magnitudes. SPVF produced optimal surface properties with a perfectly flat surface and CRS‐like SP. All three mechanical surface treatments generated similar fatigue life improvements (108–122%) over LSG when the cyclic stress was below the yield stress. Above the yield stress, most of the CRS relaxed during the first cycle in VP specimens, resulting in up to 97% fatigue life improvement over LSG. The CRS relaxed more gradually in SP specimens leading to larger (up to 239%) fatigue life improvement. This shows the need to amplify CRS magnitudes produced in VP to maximize fatigue life improvement. Highlights: Vibratory peening (VP) provides 7X better surface finish than shot peening (SP).VP generates 66% deeper compressive residual stresses (CRS) compared to SP.VP increases fatigue life up to 122% relative to low‐stress grinding.SP generates higher CRS and longer fatigue life above the yield stress than VP. [ABSTRACT FROM AUTHOR]

The surface morphology has a significant influence on the fatigue behavior of components. For austenitic stainless steels (ASSs), this issue is even more pronounced due to their metastability. Based on the complex deformation mechanisms of metastable ASSs, which include dislocation slip, deformation twinning, and deformation‐induced martensitic phase transformation, the metastable stainless steel AISI 347 was investigated in this study together with the stable AISI 904L as a reference material. Four‐point bending fatigue tests with load ratio R = 0.1 and testing frequency f = 10 Hz at ambient temperature were carried out on specimens with five technically relevant surface morphologies: mechanical polished, milled, microshot peened, laser shock‐peened, and ultrasonic modified. Systematic material characterizations were carried out to elucidate the crucial role of surface roughness and deformation‐induced α′‐martensite in the fatigue behavior of both metastable and stable materials. While surface roughness is a well‐known key factor in conventional fatigue cases, deformation‐induced martensite layers implemented by various surface modification methods were proven to improve the fatigue life in metastable austenitic steels, opening new perspectives to extend the lifetime of ASS components. Highlights: Investigated surface morphology's impact on four‐point bending fatigue in ASSs.Diverse surface treatments to achieve various surface morphologies. [ABSTRACT FROM AUTHOR]

Laser‐based powder bed fusion (PBF‐LB) has gained prominence in the realm of additive manufacturing of metals. This technique utilizes a laser beam to consolidate powder layers, which inherently introduces high thermal gradients and rapid cooling rates. This results in characteristic process effects, including inhomogeneities, surface roughness, anisotropy, and residual stress, which play a pivotal role in altering the fatigue properties of the manufactured components. This paper presents fatigue tests involving samples of AlSi10Mg manufactured using PBF‐LB with varying surface roughness and residual stress. An approach to predict fatigue life based on stress amplitude, residual stress, and crack size is presented, using a smooth sample as a reference. An empirical model for fatigue life prediction is developed from experimentally measured values of fatigue life, peak surface roughness, and residual stress. Highlights: Novel method predicts fatigue life using residual stress and surface roughness.Surface roughness initiates cracks in as‐built specimens.Reference S‐N curve from smooth, untreated samples is crucial for prediction.Equivalent stresses can be used to predict fatigue life. [ABSTRACT FROM AUTHOR]

The high‐temperature fretting fatigue damage characteristics of dovetail specimens strengthened by nanosecond laser (NL) and nanosecond combined femtosecond laser (F‐NL) were investigated. The results show that the fretting fatigue life of the NL strengthened sample (NL sample) is improved by 211.2% compared to the base metal samples (BM sample). The lifetime of the nanosecond combined femtosecond strengthened sample (F‐NL sample) was increased by 319.6%. It was attributed to the strengthening introducing hardened layers, residual compressive stress field, and high density of dislocations. The combined strengthening process reduces the surface roughness of the NL strengthened surfaces, while the strengthening influence layer is further increased. The fracture morphology shows that the crack source of the strengthened specimen has changed from multi‐source sprouting to single‐source sprouting, and the crack source sprouted on the subsurface. The fatigue strip morphology similarly confirms that a reduction in the crack propagation rate occurs. Highlights: Dovetail specimens were subjected to fretting fatigue testing at 500°C.Composite laser peening reduces surface roughness and stress concentrations.Mechanism of fatigue property enhancement after combined laser peening revealed. [ABSTRACT FROM AUTHOR]