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A multi-stage precipitation model is formulated to predict the microstructural evolution and explain the high performance of additive friction stir deposited aluminum alloy 7050 (AA 7050) for hole repair. The first stage is the heating process due to the high-temperature thermomechanical process of the stir. In this process, small η precipitates dissolve as they lose their stability with increasing temperature, and this causes the volume fraction of η precipitates to decrease and the concentration of Mg and Zn in the matrix to increase. The second stage is the cooling process at the end of the repair where material feeding ends and the tool is lifted away. Heterogeneous nucleation of η precipitates may occur and as the temperature cools below 250 °C, Guinier–Preston (GP) zones start to form. The final stage is the natural aging process, where the η ′ precipitate starts to grow. The volume fraction and precipitate radius are predicted for each type of precipitate. Furthermore, the fine η ′ precipitates and GP zones with a decent volume fraction improve the material strength and fatigue life. [ABSTRACT FROM AUTHOR]

The advancement of lightweight automotive technologies has necessitated the adoption of various lightweight materials, leading to the development and investigation of numerous joining techniques. Among these researches, spot joining technology plays a critical role in the automotive sector, as its fatigue performance significantly influences vehicle safety and durability while maintaining structural integrity. Research focused on this technology is essential for enhancing automotive lightweighting initiatives. This article comprehensively reviews the fatigue performance associated with spot joining technologies. It examines key factors influencing fatigue performance and outlines various methods for predicting fatigue life. The discussion encompasses the spot joining technologies currently employed in automotive lightweight sheet materials, concisely evaluating their application status and developmental trends. The fatigue testing of spot joining joints is analyzed from four distinct perspectives: environmental factors, residual stress, loading conditions, and other aspects, all of which impact the fatigue performance of the joints. Moreover, five primary methods for predicting fatigue life in spot joining technology are detailed. Finally, the article concludes by offering insights into potential future research avenues aimed at enhancing the understanding of fatigue performance in spot joining technologies. [ABSTRACT FROM AUTHOR]

This study proposes a method for assessing the effect of stochastic vibrations resulting from track irregularities which are rarely studied but significant on bridge fatigue. First, the pseudo-excitation method is utilized to determine the power spectrum density of stress. Subsequently, the trigonometric series method is employed to acquire the stress time history set. Then, a traditional fatigue life calculation method is employed for analysis. By utilizing a post-sampling method, the need for costly repetitive solutions of the vehicle-bridge coupling system is eliminated. Numerical simulations are conducted on a steel truss bridge, revealing the non-negligible effect of track irregularity on bridge fatigue performance. The study investigates the underlying mechanism, highlighting the pronounced influence of long-wave track irregularity. Moreover, the research explores the correlation between track smoothness and bridge fatigue performance, demonstrating that a decrease in track smoothness leads to an increase in fatigue loss. These findings emphasize the necessity of considering stochastic vibrations when evaluating bridge fatigue, providing valuable insights for bridge design and maintenance. [ABSTRACT FROM AUTHOR]

Ultrasonic elliptical vibration cutting (UEVC) has the advantage of extending the tool life and improving the surface finish, which can realize the precision machining of hard and brittle tungsten heavy alloys (WHAs). Combined with finite element simulation and cutting experiments, this paper studies the effect of two-phase amplitude on the stress, strain, surface morphology, and residual stress distribution of the machined surface of WHAs by UEVC and draws the following conclusions: the material removal mode of WHAs in UEVC is the "Compression-Shear-Tension" composite process, and the tool cuts into the workpiece through extrusion and then forms chips through shearing and pulling. The variation of the two-phase amplitude causes the surface morphology and plastic deformation of the machined surface to exhibit up and down fluctuations, while the surface residual stress shows an alternating distribution of tensile and compressive stress, and the tensile stress is mostly distributed on the surface bulge. Increasing the amplitude Aa along the cutting direction promotes the flatness and deformation homogeneity of the surface, effectively reducing the residual tensile stress. Increasing the amplitude Ab along the cutting depth direction reduces the surface residual tensile stress but leads to the roughening and inhomogeneous deformation of the machined surface. Therefore, from the point of view of reducing the surface roughness and improving the fatigue life, the large Aa should be selected in UEVC of WHAs. In order to suppress the deterioration of the machined surface mass as large Ab is applied, it is necessary to ensure that Aa is larger than Ab. [ABSTRACT FROM AUTHOR]

This study investigates the effectiveness of in-situ urea-assisted nitriding during electrical discharge machining (EDM) as a novel approach to enhance the fatigue performance of AISI 4140 steel. EDM is known to introduce surface defects and tensile residual stresses that compromise fatigue strength. By employing a urea-based dielectric solution, this method forms a protective nitride layer on the steel surface, which addresses these issues. Experimental results demonstrate significant improvements in fatigue life for nitrided specimens, with an increase of 24% at a stress amplitude of 388 MPa and up to 14-fold at 242 MPa. Additionally, surface tensile residual stresses were reduced by 26% in nitrided specimens. These enhancements are attributed to the formation of the nitride layer, which improves fatigue resistance and surface integrity. Compared to traditional nitriding methods, in-situ urea-assisted EDM nitriding offers several advantages, including the ability to simultaneously form the nitride layer and machine the component, reducing processing time and costs. This work underscores the promising potential of in-situ urea-assisted EDM nitriding as an effective strategy for improving the fatigue performance of AISI 4140 steel components and suggests directions for future research in surface modification techniques. [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]

This study focuses on the evolution of the fatigue strength of Laser Powder Bed Fusion (L‐PBF) produced Ti‐6Al‐4V as a function of the chemical etching finishing process. The aim is to identify the critical fatigue crack initiation mechanisms and the transitions between them in terms of the evolution of the surface micro‐geometry. This is done using three different geometries and six different surface states. The evolution of the crack initiation mechanisms is then used to explain the evolutions of the fatigue strength and the fatigue scatter. Chemical etching affects the fatigue life via a polishing effect, which directly influences both the finite and the high cycle fatigue domains. It is shown that chemical etching makes it possible to obtain fatigue strengths that are almost similar to those of the machined surface. However, it is also observed that etching cannot fully counteract the effects of large surface cavities caused by surface connected porosities. Highlights: Fatigue results are presented for Ti‐6Al‐4V L‐PBF with and without chemical etching.The fatigue strength sensitivity to defect size is clearly characterized.The different fatigue crack initiation mechanisms are identified.The initiation mechanisms evolution as a function of the finishing process is studied. [ABSTRACT FROM AUTHOR]

An XY-compliant mechanism is a two-degree of freedom positioner which is considered to have some distinguishing characteristics in ultra-precision technology. To ensure a long working life, it is necessary to study the fatigue life, however, in the related works of the XY-compliant mechanism, no research into design optimization for maximum fatigue life has been conducted so far. Moreover, the sample size of fatigue data is often inadequate to develop a surrogate model. This paper pioneers a new method for maximizing the fatigue life of the proposed mechanism, in the context of small-size fatigue life samples. Particularly, the Synthetic Minority Oversampling Technique is utilized to enlarge the sample size. A machine learning technique is then applied to create the surrogate model, in which fatigue life is considered the output. The Hunger Games Search is then used to maximize the output. In this study, Steel A36 and AL 6061T6 materials are utilized for the mechanism. The numerical results of two case studies show that using Synthetic Minority Oversampling Technique can predict appropriately the fatigue life, compared to using the original data. Specifically, after taking the natural logarithm of fatigue life, the average mean square error when using simulated data is 1.8 % and 36.8 % better than when using original data, for Case 1 and Case 2, respectively. The optimal fatigue life found by the proposed method compared with the baseline is about 350 % for Case 1 and 1250 % for Case 2, respectively. The optimal findings are also confirmed using ANSYS software, in which the errors of fatigue life are less than 5 % . [ABSTRACT FROM AUTHOR]

This work examines the effect of temperature on the self-healing of asphalt mixture, and various laboratory tests were performed to find out qualitative and quantitative properties of asphalt material. Asphalt fatigue life and bending strength were determined using a three-point bending test and a four-point beam fatigue test. Test specimens were heated at various temperatures ranging from 20°C to 40°C for various periods, including the 20, 40, 60, 80, and 100 s. The strength recovery ratios at temperatures 20°C, 25°C, 30°C, 35°C, 40°C were 7%, 30%, 36%, 40%, 45%, respectively. The maximum healing index values for bitumen with penetration grades of 60/70 and 80/100 were 0.4 and 0.5 at temperatures between 37°C and 40°C. A 60 s period was chosen as the ideal period for achieving the highest recovery ratio for both bitumen specimens. It was observed that critical factor affecting the asphalt's capacity for self-healing is temperature, and the maximum healing index was found at temperatures between 37°C and 40°C. [ABSTRACT FROM AUTHOR]

Micro-texture regions (MTR), defined as a cluster of grains with similar crystallographic orientations, have a significant detrimental effect on the fatigue life of Ti alloys. This paper proposes a novel multiscale approach, coupling the Parametrically Upscaled Constitutive Model (PUCM) for predicting component-scale deformation with the Parametrically Upscaled Crack Nucleation Model (PUCNM) for fatigue crack nucleation in polycrystalline microstructures of α / β Ti6Al4V alloy containing MTRs. The PUCMs represent higher-scale constitutive models whose coefficients are explicit functions of Representative Aggregated Microstructural Parameters (RAMPs), representing statistical functions of key morphological and crystallographic descriptors of the underlying microstructure. A novel RAMP is proposed for the quantification of the MTR intensity that incorporates a measure of the relation between the MTR crystallographic orientation and the local principal stress direction, in addition to morphological and crystallographic characteristics like MTR size, crystallographic orientation, average misorientation, and misorientation distribution within the MTR. The MTR intensity parameter is incorporated in the physics-informed PUCNM for macro-scale analysis of fatigue crack nucleation. The PUCNM is validated using experimental dwell fatigue tests with different microstructures. A WATMUS-accelerated PUCM-based FE model of a double-edged notched specimen is simulated under dwell fatigue loading to investigate the effect of notch geometry and microstructural features on dwell fatigue crack nucleation. Studies examine the interplay between the specimen geometry, macroscopic stresses, and the underlying microstructure with MTRs on the nucleation life. [ABSTRACT FROM AUTHOR]

Bridges situated in northern climate regions, which face severe environmental conditions and daily fatigue loading, are prone to accelerated deterioration and corrosion of their components. The application of carbon fiber–reinforced polymer (CFRP) sheets bonding to the surface of bridge elements has emerged as an attractive solution for enhancing bridge strength. Past studies and field implementations have effectively showcased the viability of this approach in strengthening bridges. An exceptional opportunity arises with the deconstruction of a bridge in Canada, providing a unique chance to assess and study the condition of reinforced concrete elements strengthened with CFRP. These elements have endured real service conditions, including fatigue loads and exposure to aggressive environmental factors. This paper presents the experimental results of a research program that aimed to investigate the residual fatigue life and capacity of 60-year-old reinforced concrete bridge girders, which were strengthened using CFRP sheets. The study focuses on assessing the performance of these girders under different test conditions, providing valuable insights into their remaining fatigue life and load-carrying capabilities. The two 60-year-old girders have been strengthened with CFRP for the last 10 years of the service life of the bridge. The two full-scale girders were tested under 2 million fatigue load cycles and then tested monotonically until failure at the structural lab of the University of Sherbrooke. The test results revealed that the CFRP-strengthening technique can extend the service life of the bridge element and enhance its shear capacity. The CFRP–concrete interface and CFRP sheets showed excellent bonding behavior, as no damage-debonding failure or tensile rupture occurred until the formation of the diagonal shear crack. [ABSTRACT FROM AUTHOR]

An increasing number of arch and suspension bridges have been built in railway networks. Suspender cables serve as the critical load-transmitting component in these cable-supported bridges, which are subjected to a combination of the adverse impacts of train-induced fatigue stress and a corrosive environment. However, little research effort has been made on the corrosion fatigue performance of railway bridge suspender cables. This paper proposes an approach for the corrosion fatigue evaluation of the suspenders that integrates a sophisticated fatigue stress computational model and an enhanced corrosion fatigue model. The dynamic stresses of the suspenders are computed using a three-dimensional (3D) train–bridge interaction (TBI) model, which is established to consider the train-induced flexural vibrations on the suspender. Then, the corrosion fatigue damage of steel wires is characterized by a continuum damage mechanics-based model. The condition for the transition from pitting to fatigue crack is derived. Based on this, the corrosion fatigue assessment framework for suspenders is formulated, which can describe the time-dependent damage evolution that considers significant effects. A tied-arch railway bridge is investigated to showcase the effectiveness of the proposed approach and gain insights into the corrosion fatigue performance of the suspender cables in railway bridges. The field test data are employed to validate the stress computational model. In addition, the time-dependent corrosion fatigue evolution and service life of the suspenders are obtained. The results show that the suspender flexural vibrations cause considerable variations in the equivalent stress range and number of stress cycles. The corrosion fatigue life (CFL) of the critical suspender is reduced by 25% on average due to train-induced flexural vibrations. [ABSTRACT FROM AUTHOR]

Numerical simulation of fatigue crack growth in welded joints is not well represented in the literature, especially from the point of view of material heterogeneity in a welded joint. Thus, several case studies are presented here, including some focusing on fracture, presented by two case studies of mismatched high-strength low-alloyed (HSLA) steel welded joints, with cracks in the heat affected zone (HAZ) or in weld metal (WM). For fatigue crack growth, the extended finite element method FEM (XFEM) was used, built in ABAQUS and ANSYS R19.2, as presented by four case studies, two of them without modelling different properties of the welded joint (WJ). In the first one, fatigue crack growth (FCG) in integral (welded) wing spar was simulated by XFEM to show that its path is partly along welded joints and provides a significantly longer fatigue life than riveted spars of the same geometry. In the second one, an integral skin-stringer panel, produced by means of laser beam welding (LBW), was analysed by XFEM in its usual form with stringers and additional welded clips. It was shown that the effect of the welded joint is not significant. In the remaining two papers, different zones in welded joints (base metal—BM, WM, and HAZ) were represented by different coefficients of the Paris law to simulate different resistances to FCG in the two cases; one welded joint was made of high-strength low-alloyed steel (P460NL1) and the other one of armour steel (Protac 500). Since neither ABAQUS nor ANSYS provide an option for defining different fatigue properties in different zones of the WJ, an innovative procedure was introduced and applied to simulate fatigue crack growth through different zones of the WJ and evaluate fatigue life more precisely than if the WJ is treated as a homogeneous material. [ABSTRACT FROM AUTHOR]

ABSTRACT Cyclic pressures can cause fatigue failure in the brazed joints and plates of the plate heat exchangers (PHEs). This study examines the fatigue behavior of PHEs made from 316L and 304L steels brazed with copper foils employing strain‐controlled fatigue tests to explore if 304L could replace 316L in the existing production line for cost reduction. Fatigue tests were conducted at four different load levels with a stress ratio of zero and a frequency of 5 Hz. Finite Element Analysis was used to assess strain distribution and estimate PHE lifespan based on generated strain versus number of cycles to failure curves. The microstructural analysis revealed that copper diffuses more easily into 316L than 304L, and using 50 μm thick foil causes more defects compared with 100 μm foil. It was shown that 316L joints have a significantly increased fatigue life compared with 304L. Both 316L and 304L met the 15‐year lifetime requirement set by manufacturers. [ABSTRACT FROM AUTHOR]

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]

Cold expansion is a mechanical method for creating residual stresses. This method is a proven technique to increase the fatigue life, and checking the residual stress on it, is of particular importance. A cold expansion process is widely used to generate beneficial residual stresses into an annular region around the hole. In the present research work, AA 6016-T6 and AA 1100 aluminum alloys which are two strain rate sensitive materials, were subjected to cold expansion process with different mandrel velocities. In fact, the effect of mandrel velocity on the created residual stresses has been investigated. The constants of the Johnson-Cook material model have been determined for them and the process has been investigated, experimentally and numerically. The obtained results revealed that the values of the residual stresses created in the sheets depend on the velocity of the process especially at the edge of the sheets holes. By increasing the mandrel velocity from 5 to 500 mm/min, depending on the distance from the hole to the edge of the sheet, it is possible to enhance the hoop residual stress by 37.3–41.2% in AA 1100 aluminum alloy and by 37.6–38.1% in AA 6016-T6 aluminum alloy. This research showed that in all cases, the radial residual stresses created around the holes are negative. Also, it was cleared that due to the existence of material constraints and the movement of the sheet material, the amount of hoop residual stress created in the mid-thickness is more than the exit face and in the exit face is also more than the entrance face, exactly unlike the size of their zones. [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]

High performance bolts, made of continuous fiber reinforced silicon carbide composites (C/SiC), are crucial to the design and preparation of the hot-end C/SiC components with large complex structures both in aerospace and aeronautical fields. In this work, in-situ grown SiC whiskers were uniformly introduced into the porous laminated 3DN C/SiC countersunk bolt, in order to improve the brittle nature of the 3DN C/SiC threads. Results showed that 7 % increase of tensile strength of the 3DN C/SiC countersunk bolts was achieved via in-situ grown SiC whiskers, and a fatigue life of 106 cycles was also passed. The stud fracture morphologies indicated that the SiC whiskers grew within the woven pores and toughened the layered SiC matrix, so that the load transfer between the layered SiC matrix and carbon fibers was improved under tension. Further high temperature tests showed that the tensile and the shear strengths of the in-situ toughened 3DN C/SiC countersunk bolts were degraded to 64.74 % and 28.83 % at 1000 °C in air respectively. During the thermal exposure, the carbon fibers were largely consumed by oxidation, while the SiC whiskers grew slender and formed a fluffy layer to partially reinforce the SiC matrix. The synergy effect of SiC whiskers and carbon fibers to hinder crack propagation and to toughen the SiC matrix contributes to the above mechanical properties of the bolts. [ABSTRACT FROM AUTHOR]

To quickly obtain the fatigue life of cranes in service, the metal structure that determines the crane life is anchored. Meanwhile, the fast prediction method of fatigue life of crane metal structures based on the Stacking ensemble learning model is proposed. Firstly, in line with the structural stress method, the global rough model of the metal structure is established by the co-simulation technology to obtain the fatigue damage regions of the structure. The local fine model is constructed by local cutting and boundary condition transplantation to determine the critical weld at the failure regions. Secondly, through weld definition, equivalent structural stress acquisition, and fatigue life calculation, the sample data set with lifting load and trolley running position as input and fatigue life cycle times as output is constructed. Then, the Stacking integrated learning model combining gradient boosting, ridge regression, Extra Trees, and linear is built. On this basis, combined with the Miner theory, the rapid prediction of crane fatigue life is realized. Finally, the proposed method is applied to the QD40t × 22.5 m × 9 m general bridge crane. The results show that the life sample set constructed by the structural stress method is more accurate and reasonable than the nominal, hot spot, and fracture mechanics methods. The life prediction results of the Stacking integration model were improved by 6.3 to 49.2% compared to the single model. The method has theoretical and practical significance in reducing accidents and ensuring the safe operation of cranes. [ABSTRACT FROM AUTHOR]

The large mining-height hydraulic support test-bed serves as a crucial tool for heavy hydraulic support factory inspections and type testing. With the successful development of the ZY29000/45/100D hydraulic support, the need for a large high-mining hydraulic support test-bed has become evident. This paper combines the theory of rigid-flexible coupling in virtual prototypes and ADAMS multi-body dynamic simulation technology to analyze the strength of the 50,000 kN hydraulic support test-bed. ANSYS classic modules were employed to address the flexibility of key components within the test-bed. The fatigue life of the test-bed was analyzed using NSOFT software, the von Mises yield criterion, and the Goodman modified curve. The S-N curve of material parameters for the test-bed components was used to conduct a shrinkage test. The results indicate that the lowest position is the most vulnerable during the shrinkage test. Among the key components, the stress on the pin bearing is 356.6 MPa, which is 167.9 %, 123.3 %, and 41.6 % higher than that of the pillar, movable beam, and base, respectively. The fatigue life of the base under low, medium, and high shrinkage conditions is1.1×107, 4.0×108, and 1.7×108, with damage values of 8.8×10-8, 2.5×10-9, and 5.7×10-9, respectively. The base’s life under low shrinkage conditions is the shortest, followed by that under high shrinkage conditions. These research findings provide technical guidance and an optimization foundation for the successful development of a 50000 kN hydraulic support test-bed. They also offer a new method and approach for analyzing and predicting the fatigue life of key components in large-scale industrial and mining equipment operating under complex conditions, with promising practical applications. [ABSTRACT FROM AUTHOR]

New materials have emerged in the dental field to replace the cobalt-chrome (CoCr) alloy used for the metal frameworks in removable partial denture (RPD) such as Titanium (Ti) and PolyEtherEtherKetone (PEEK). However, few studies have demonstrated their mechanical and biological performance. The purpose of this systematic review was to compare the performance of Ti and PEEK in RPD using CoCr metal framework as a reference. This review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three data bases were analyzed, including PubMed/MEDLINE, Embase and Web of Science before March 2024. Only studies assessing the mechanical and/or biological properties of RPD in Ti, PEEK and CoCr were included. The quality of the studies was assessed by using the software Rayyan. The risks of bias were assessed with the methodological index for nonrandomized studies (MINORS). The mechanical (retention force, fatigue life, deformation strength, machinability, rigidity, porosity and surface roughness) and biological (plaque indices, ion release and biocompatibility) aspects were assessed. Among 138 articles identified, only 18 studies were included in this review. Majority had a low to moderate risk of bias. Retention forces and fatigue were significantly lower for Ti and PEEK than for CoCr, and the same was true for Ti rigidity. PEEK showed less deformation. Both materials were suitable for machining. In terms of biological properties, both materials showed adequate biocompatibility for clinical use. Ti and PEEK seems to be promising as alternative materials to CoCr frameworks for RPD, in terms of both their mechanical and biological performance. However, additional studies are needed to better understand their clinical and long-term limitations to enable the best-informed clinical choice for the patients and the professionals. [ABSTRACT FROM AUTHOR]

The multi-parameter characteristics of the physical model pose a challenge to the fatigue life prediction of 2024-T3 aluminum (Al) alloy. In response to this issue, a parameter-solving method that integrates particle swarm optimization (PSO) with extreme gradient boosting (XGBoost) is proposed in this study. The fatigue performance and failure mechanism of the 2024-T3 Al alloy are analyzed. Furthermore, the fatigue life prediction physical model of the 2024-T3 Al alloy is established by using the energy method of fracture mechanics. The physical model incorporates critical physical parameters. Meanwhile, the PSO algorithm optimizes the hyperparameters of the XGBoost model based on fatigue data of the 2024-T3 Al alloy. Eventually, the optimized XGBoost model is used to solve the parameters of the physical model. Furthermore, the analytical equation of the fatigue life prediction model is obtained. This paper provides a new method for solving the parameters of the fatigue life prediction model, which reduces the error and cost of obtaining the model parameters in the experiment and shortens the time required. [ABSTRACT FROM AUTHOR]

This study experimentally assessed the shear performance of reinforced concrete (RC) beams strengthened with U-shaped High-Performance Fibre-Reinforced Concrete (HPFRC) under static and fatigue loading. Key parameters included HPFRC jacket thickness and beam shear span–depth (a/d) ratio. Five beams were tested under static loads to determine ultimate shear strengths, followed by fatigue tests on identical beams at 30–70% of ultimate shear strengths at 4 Hz. In static loading experiments, all the HPFRC jacketing proved effective, increasing the shear strength of RC beams by 95% to 130%. Although the strengthening system did not change the failure mode of the beams, the strengthened beams exhibited pseudo-ductile behaviour. As the a/d increased, the shear enhancement capability of the HPFRC jackets decreased. In fatigue loading experiments, all the HPFRC systems improved the fatigue life of RC beams. Specifically, in beams with an a/d ratio of 2.0, the fatigue life was extended from 75 cycles to a maximum of 951 cycles, while in beams with an a/d ratio of 3.5, it increased from 12,525 cycles to 48,786 cycles. In addition, a predictive model has been developed for the fatigue life of HPFRC/UHPFRC shear-strengthened beams, utilising the maximum fatigue load and the design's ultimate shear strength under static loading conditions. [ABSTRACT FROM AUTHOR]

The stress state of the primary circuit main pipeline is very complex mixed constant stress and periodic cyclic stress during the operation of nuclear power plants, which often affects the failure behavior of the stainless steel (SS) pipe. The fatigue behavior of 304LN SS under mixed constant stress and cyclic stress was investigated, and it was found that the coupling effect of constant stress and cyclic stress has a significant collaborative acceleration on the fatigue behavior. The research results showed that the cracks in the 304LN SS did not propagate even after 78 days under both constant load conditions of 5 KN and 7.5 KN, while the crack growth rate (CGR) of the specimen increased by about an order of magnitude when coupled with a cyclic fatigue load. The fatigue life of 304LN SS was the longest under 200 °C high-temperature water, and its life was roughly the same under 250 °C and 300 °C water. In a 300 °C high-temperature water environment, the fatigue life under the coupling of constant stress and cyclic fatigue stress is significantly lower than that under symmetric cyclic stress alone. There is a synergistic acceleration effect on the fatigue life of 304LN SS when constant stress is coupled with periodic cyclic stress, which is attributed to the combined effect of a corrosion environment and mechanical factors. [ABSTRACT FROM AUTHOR]

The operational practice of the design of the Bozena 5 demining machine has shown that its belts are the critical component that fundamentally affects the functionality of the entire machine. This article is a practical continuation and extension of the previous research results from the point of view of materials (research of the uniaxial fatigue life in bending and torsion), calculation (creation of the necessary mathematical, analytical and numerical models for the research) and construction (i.e., patented design of the belt tensioning of this machine). All these actions are aimed at a single objective—to achieve a condition that guarantees a sufficient service life without malfunctions, since repairing these machines in the field is often impossible. Therefore, this study examined the fatigue life of welded joints (uniaxial bending and torsion) of S960 QL and S500MC steels welded by MAG technology. Subsequently, the data were compared with previous results (electron and laser welds) and the influence of each type of weld on the fatigue life relative to the base material was discussed. It was found that conventional MAG technology had a more significant negative impact on the fatigue life of the base material than non-conventional technologies. This trend was particularly true for the bending stress. At the same time, the bending stress was identified by the FEM analysis as the dominant load on the belt. The maximum stress in the belt link under the considered boundary conditions was approximately 240 MPa (in bending). This stress corresponded to the continuous fatigue life (more than 107 cycles) for both base materials tested (S960QL, S500MC). In the whole studied spectrum of controlled deformation amplitudes (Manson–Coffin), the life of MAG welds was lower in comparison with the base material and with welds made by unconventional technologies. All the activities carried out so far (research on microstructure, hardness, strength, residual stresses, tribological properties and fatigue life) have shown that the original belt design (S500MC) using MAG technology has significant deficiencies in the state of optimal life. It is expected that the proposed material change (use of S960QL instead of S500MC) and work with advanced technologies will bring this state significantly closer. [ABSTRACT FROM AUTHOR]

The fatigue behavior of metal specimens is influenced by defects, material properties, and loading. This study aims to establish a multi-scale fatigue crack growth model that describes physically short crack (PSC) and long crack (LC) behavior. The model allows the calculation of crack growth rates for uniaxial loading at different stress ratios based on the material properties and specimen geometry. Furthermore, the model integrates the Gaussian distribution theory to consider material heterogeneity and the experimental measurement errors that cause fatigue scatter. The crack growth rate and fatigue life of metal specimens with different notch geometry were predicted. The curves generated by the multi-scale model were mainly consistent with the test data from the published literature at the PSC and LC stages. [ABSTRACT FROM AUTHOR]

Biodegradable implants as bone fixations may present a safe alternative to traditional permanent implants, reducing the risk of infections, promoting bone healing, and eliminating the need for removal surgeries. Structural integrity is an important consideration when choosing an implant material. As a biodegradable implant is being resorbed, until the natural bone has regrown, the implant material needs to provide mechanical stability. However, the corrosive environment of the human body may affect the fatigue life of the material. Conversely, mechanical stress can have an effect on electrochemical corrosion processes. This is known as corrosion fatigue. In the presented work, an experimental setup and methodology was established to analyze the corrosion fatigue of experimental bioresorbable materials while simultaneously monitoring the electrochemical processes. A double-walled measurement cell was constructed for a three-point bending test in Dulbecco's Phosphate-Buffered Saline (DPBS− −), which was used as simulated body fluid (SBF), at 37 ± 1 °C. The setup was combined with a three-electrode setup for corrosion measurements. Rod-shaped zinc samples were used to validate the setup's functionality. Preliminary static and dynamic bending tests were carried out as per the outlined methodology to determine the test parameters. Open-circuit as well as potentiostatic polarization measurements were performed with and without mechanical loading. For the control, fatigue tests were performed in an air environment. The tested zinc samples were inspected via scanning electron microscopy (SEM). Based on the measured mechanical and electrochemical values as well as the SEM images, the effects of the different environments were investigated, and the setup's functionality was verified. An analysis of the data showed that a comprehensive investigation of corrosion fatigue characteristics is feasible with the outlined approach. Therefore, this novel methodology shows great potential for furthering our understanding of the effects of corrosion on the fatigue of biodegradable implant materials. [ABSTRACT FROM AUTHOR]

Mechanical failure of biological nanostructures due to sustained force application has been studied in great detail. In contrast, fatigue failure arising from repeated application of subcritical stresses has received little attention despite its prominent role in engineering and potentially biology. Here, paclitaxel-stabilized microtubules are up to 256 times bent into sinusoidal shapes of varying wavelength and the frequency of breaking events are observed. These experiments allow the calculation of fatigue life parameters for microtubules. Repeated buckling due to 12.5% compression–equal to the compression level experienced by microtubules in contracting cardiomyocytes – results in failure after in average 5 million cycles, whereas at 20.0% compression failure occurs after in average one thousand cycles. The fatigue strength (Basquin) exponent B is estimated as − 0.054±0.009. [ABSTRACT FROM AUTHOR]

Mechanical characteristics, instability precursors, and fatigue life prediction of rocks under fatigue loading are significant for the prediction and prevention of mining disasters. Taking the porous siltstone widely distributed in the mining area of western China as the research object, a characteristic stress determination method based on the evolution characteristics of the multiphase volumetric strain of porous rocks was established. Referring to the characteristic stress interval, bivariate fatigue damage-controlled tests with different upper limit loads and different numbers of cycles were conducted. The results indicate that the strengthening and the weakening of the macroscopic strength of siltstone under fatigue loading are caused by the competition of two mesostructure effects, namely the "weak structure failure effect" and the "compaction embedment effect". The dominant effect varies with different upper limit loads and different numbers of cycles. Importantly, the transition of the bulk compliance from positive to negative is an early precursor of fatigue failure, while the simultaneous sudden increase in cumulative acoustic emission count, acoustic emission bk value, and energy dissipation ratio is an imminent precursor of fatigue failure. The evolution characteristics of the strain, acoustic emission, and energy dissipation indicate that the crack damage stress of siltstone is a reliable indicator of its fatigue strength. Furthermore, a nonlinear viscoplastic damage element was introduced to construct a nonlinear fatigue rheological damage model, and model validation and quantitative analysis of parameter effects were conducted. Finally, by determining the accelerated rheological start threshold and the accelerated rheological failure threshold, a rapid prediction method for the fatigue life was established. Highlights: A characteristic stress determination method suitable for porous rock. Mesoscopic mechanism of strength strengthening and weakening. Early and imminent precursors of fatigue rheological failure. A nonlinear fatigue rheological damage model. [ABSTRACT FROM AUTHOR]

The Manson-Halford (M-H) nonlinear cumulative damage model is widely applied for fatigue life analysis problems under multi-level loading. In this model, the influence of loading sequence on the fatigue life can be better considerer, but the loading interaction effect is ignored. An improved whale optimization algorithm (IWOA) by integrating multiple strategies is proposed. The ability of global search and local exploitation is balanced and improved through nonlinear convergence factor, adaptive weighting factors and the Cauchy reverse learning strategies. In order to fully account for loading interaction effect, loading weighting factors are introduced to modify the M-H model, and the parameters are optimized through the global search properties of IWOA. The model is evaluated on multi-level loading fatigue experimental data from five metal materials and two aluminum alloy welded joints. The results suggest that the proposed IWOA has better optimization accuracy compared to the standard whale optimization algorithm (WOA). The proposed modified M-H model has better prediction performance compared to the four traditional cumulative damage models, which can be effectively applied to multi-level loading fatigue life analysis problems under actual working conditions. The proposed model is useful for the study of fatigue life evaluation methods. [ABSTRACT FROM AUTHOR]

Purpose: The present paper aims to study the influence of the substrate system on the thermomechanical response of various lead-free die attach materials used in power electronics using nonlinear finite element simulations. Design/methodology/approach: Particularly, three ceramic substrate systems, including direct copper bonded (DCB) and aluminum nitride (AlN) – as well as silicon nitride (Si3N4) –based insulated metal substrate (IMS) configurations are examined in this study. Additionally, three die attach systems, namely, silver-tin transient liquid phase (TLP), sintered silver (Ag) and sintered copper (Cu) are included in the analysis. ANSYS software is employed to build the finite element models of the power modules and to conduct the nonlinear thermomechanical investigations. Findings: The simulation results revealed that the IMS, Si3N4 and DCB-based power modules end up with significantly lower interconnect inelastic strains and inelastic strain energies suggesting better fatigue life performance. Additionally, the bonding layer stresses and expected failure mechanism are not influenced by the substrate configuration rather than the bond material. For instance, the silver-tin TLP joints develop high stresses and hence brittle failures are expected. Nonetheless, the sintered Ag and sintered Cu have significantly lower stresses which could lead to fatigue-induced failures. Originality/value: Power electronics use various ceramic-based substrate systems because of their improved thermal conductivity, electrical insulation and heat resistance properties. The proper selection of the substrate structure could highly enhance the thermal fatigue of the power modules. Markedly, the findings of this research are useful for designing highly reliable and effective power modules continuously subjected to thermomechanical loadings. [ABSTRACT FROM AUTHOR]

The uniformity and efficiency of ultrasonic needle peen-forming (UNPF) cannot be achieved by a handheld single-needle peening device. Thus, a novel robotized UNPF system is designed in this paper with a multi-needle peening device. By taking the aluminum alloy 2024-T3 specimens as an example, the peening device's travel velocity and standoff distance are first determined to balance processing efficiency and safety. Thereafter, the resulting arc height for Almen-size specimens with respect to other manipulated variables (MVs), such as the vibration amplitude, the air pressure, and the number of peening passes, are fitted by the data-driven models. As the radius of curvature at the saturation state is identical for small and large specimens with similar shapes, its relationship with the arc height and at the saturation state is represented by a function of elliptic paraboloid for understanding the limit of UNPF capability. It is shown that specimens of different sizes but the same aspect ratio have a consistent radius of curvatures after being treated with the same MVs. Notably, by increasing the vibration amplitude from 21 to 35 μ m , the ratios of peening time required for achieving full coverage to its counterpart for achieving saturation state reduced from 76 to 8.3%, showing a significant improvement in forming productivity and capability. Furthermore, increasing the number of peening passes, from 1 to 32 significantly reduces surface roughness by up to 86.4%, approaching the as-received specimen's smoothness. Moreover, the maximum compressive residual stress after UNPF is - 500 MPa at a depth of 1.2 mm, and the hardness is drastically increased by 45.4% for specimens of thickness 1.5 mm, improving their fatigue life. [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]