Fatigue Performance Research Articles

Combined effects of a Mediterranean diet and respiratory muscle training on higher education woodwind musicians: A randomized controlled trial

A two-factor within subjects and randomized controlled was conducted with three groups (two experimental and one control) to explore the effects of the Mediterranean diet and respiratory muscle training on ventilatory fatigue, stress, and emotional performance of woodwind musicians. 70 students from the Valencia Conservatory of Music were recruited and randomized into three groups: respiratory training group + nutrition program (RTG; n = 17), control group (CG; n = 35) and nutrition program group (NPG; n = 18). The nutritional program was based on Mediterranean a diet. Body composition, emotional intelligence, physiological stress and ventilatory response were assessed for all groups before and after intervention. Mixed ANOVA showed main effects of diet and training interventions on emotional attention (F = 8.042; p = 0.006), clarity (F = 9.306; p = 0.003), repair (F = 5.527; p = 0.022), Forced-Expiratory-Volume (F = 30.196; p < 0.000) and Forced-Vital-Capacity (F = 21.052; p < 0.000), with both interventions improving emotional intelligence and ventilatory variables. Bonferroni post-hoc analysis revealed significant differences of RTG and CG for emotional attention (MD = 4.60; p = 0.023), comprehension (MD = 5.734; p = 0.005), repair (MD = 8.576; p < 0.000), FEV1 (MD = 0.862; p = 0.005), and FCV (MD = 1.608; p < 0.001); with similar results when comparing NTG and CG: emotional attention (MD = 4.156; p = 0.041), comprehension (MD = 4.473; p = 0.033), repair (MD = 6.511; p = 0.001), Forced-Expiratory-Volume (MD = 1.608; p < 0.001), and Forced-Vital-Capacity (MD = 1.183; p < 0.001). No significant effects of experimental groups were observed for physiological stress variables (p > 0.05). This results suggests that respiratory training enhances emotional intelligence and lessens respiratory fatigue in musicians, and a combination of a Mediterranean diet and respiratory muscle training further boosts emotional intelligence, albeit with limited impact on physiological stress. This study represents a novel investigation into the approach by dietary interventions and respiratory muscle training in wind musicians since there are no studies that analyze it.

Microstructural and fatigue characterization of 316L stainless steel subjected to flow drilling and tapping: comparison with machined threads

Despite extensive research on the plastic deformation of materials to enhance their fatigue resistance, the influence of the flow tapping process on the fatigue resistance of drilled and tapped bars remains poorly understood. Herein, the fatigue performance of flow-drilled (friction-drilled) and flow-tapped 316L stainless steel bars was experimentally analyzed and compared with that of conventional material-shearing-based drilling and tapping operations. The effect of flow processes on the material properties was evaluated via microhardness tests and microstructural analyses. The results indicated that the hardness near the holes produced via flow forming was 62 % higher than that of the base metal. Moreover, grain refinement and plastic deformation were observed beneath the thread surfaces. Metallographic observations revealed the occurrence of craters and folds at the crest of the flow-formed threads. Following the ASTM F382-17 standard, four-point bending fatigue tests were performed at three stress amplitudes with a stress ratio of 0.1. No noteworthy differences were observed when the maximum bending moments applied were at 75 % and 60 % of the bending moment at yield. However, when the maximum bending moment applied was limited to 50 % of the bending moment at yield, the average fatigue life of the specimens with machined threads was longer than that of their flow-formed counterparts. Fractographic observations were used to identify the crack initiation regions and elucidate the underlying fracture mechanisms. For both types of specimens, failure originated at the crest of the first thread, beneath the surface of the maximum tensile stress. The flow-processed specimens exhibited secondary cracks at the root of the threads, where grain refinement also occurred. This study provides robust empirical evidence that using flow-forming processes to thread 316L stainless steel does not systematically improve the fatigue resistance of the material surrounding the holes. Furthermore, by optimizing the flow process and eliminating discontinuities, the threading process proposed herein could help improve the fatigue resistance of orthopedic implants.

Laboratory Study of Aging Characteristics of Binder Warm Mix Asphalt Chemical Additive: Rutting, Fatigue Resistance, and Chemical Composition

The research aims to comprehensively assess the impact of anti-stripping agents ZycoTherm (Zyc) and Evotherm M1 (EM1) on Warm Mix Asphalt (WMA). The study employs a range of laboratory tests to investigate the rheological and chemical properties of modified asphalt. Conventional tests such as penetration and softening points are employed alongside advanced techniques including Dynamic Shear Rheometer (DSR), and Linear Amplitude Sweep (LAS) analyses to delve into the rheological properties. Chemical properties (SARA) were analyzed using thin-layer chromatography. Both short-term aging (STA) using The Rolling Thin-Film Oven (RTFO) and long-term aging (LTA) based on the Universal Simple Aging Test are simulated under controlled laboratory conditions. It was found in conventional tests that the value changed, but not significantly. In terms of rutting and fatigue performance, Zyc 0.05% showed positive results. Fatigue behavior shows Zyc has better resistance. The asphalt fractional composition test showed changes in each age condition.

Structural Damage Model of Steel Structure Connections with Initial Defects: A Review

As the application of steel structures in construction continues to grow, research into their seismic performance is becoming increasingly important. This paper focuses on steel structure connections, specifically those between components with varying profiles such as H-profiles, box-profiles, and L-profiles. Additionally, it encompasses three core areas: seismic performance (bearing capacity, ductility, stiffness), initial defects (initial cracks, residual stresses, manufacturing imperfections), and damage models (weld fractures, bolt failures, plate buckling). In addition, this paper employs experimental testing and finite element, with a focus on conducting parametric analyses for the connections. Based on the primary findings, the presence of initial defects such as cracks, residual stresses, and manufacturing imperfections can lead to premature failure, concentrating damage near welds and exacerbating stress concentrations. This adversely affects factors like fatigue strength, fracture toughness, and buckling strength, ultimately reducing the seismic performance of the connections. Moreover, factors like bolt over-tensioning, geometric deviations in plate components, and corrosion can further impact bearing capacity, fatigue performance, and ductility. Crucially, these initial defects not only compromise the seismic resistance of structures but also increase the risk of structural failure. However, majority of existing research has focused on monotonic and cyclic loading studies, with limited exploration of connections under seismic conditions. Acknowledging this gap, this paper outlines a future research agenda aimed at refining the design of steel structure connections. This initiative seeks to mitigate potential adverse consequences stemming from formidable seismic events, thereby enhancing the overall resilience of these crucial connections.

Low-cycle fatigue behavior and microstructure evolution of ODS steel pipes at high temperatures

Oxide-dispersion-strengthened (ODS) steels are candidate materials for application in advanced nuclear reactors. In this study, the low-cycle fatigue performances of 13Cr-ODS ferritic steel pipes were investigated at 600, 700, and 800 °C. Cyclic softening was observed at high strain amplitudes with an increase in the number of fatigue cycles. However, cyclic hardening appeared first, and then cyclic softening occurred at a low strain amplitude with the increase in the number of fatigue cycles. By comparing the cyclic stress–strain curves and the monotonic stress–strain curves, it was found that cyclic softening occurred regardless of the strain amplitude. The Coffin–Manson and Basquin equations were used to predict the fatigue of the pipes. Microstructure analysis indicated that cyclic softening was induced by the dynamic recovery and recrystallization, which reduced the number of low-angle grain boundaries in the deformed grains by promoting dislocation annihilation and reorganization. A complex multi-layer core–shell structure with a large size (∼500 nm) was observed.

The synergistic effect of gradient nanostructure and residual stress induced by expansion deformation on the tension-tension fatigue performance of Ti6Al4V holes

A large number of titanium alloy structural components in aircraft are joined and assembled through holes. The complex service conditions pose high requirements for the fatigue performance of the holes. The study aims to use expansion deformation to induced gradient nanostructures and residual stress enhance the fatigue performance of Ti6Al4V holes. By studying the evolution process of the microstructure in titanium alloys, the formation mechanism of gradient nanostructures has been obtained, and their impact on various stages of fatigue fracture is analyzed. The results showed that the split sleeve cold expansion (CE) process caused severe plastic deformation on the surface of the hole, resulting in a large amount of LAB production and a transformation of the main texture components. Meanwhile, the gradient nanostructures are formed on the hole surface, which include nanocrystalline layer, superfine lath grain layer, lath grain layer and severe deformation layer. During the expansion deformation process, the slip of dislocations leads to the formation of high-density dislocation structures, which evolve into subgrain boundaries and then undergo dynamic recrystallization through subgrain rotation to achieve grain refinement. What's more, the degree of grain refinement, depth of gradient nanostructure, and residual stress increase as the expansion deformation intensifies. The depth of gradient nanostructure is 300 μm, and the maximum residual stress is −419 MPa, when the deformation is 5 %. The combined effect of gradient nanostructures and high residual compressive stress induced by expansion deformation has increased the total fatigue life and crack propagation life of CE-5 specimen by 2.9 and 3.4 times compared to NCE specimen. This work provides an effective method and theoretical analysis for improving the fatigue life of titanium alloy holes.

Effect of the hot forming with synchronous quenching process on high cycle fatigue properties of the 2A97 Al-Li alloy

The 2A97 Al-Li alloys have been used in aircraft to achieve lightweight, its high cycle fatigue performance is one of the important factors that determines aircraft safety. The 2A97-T8 Al-Li alloy is obtained through the 2A97-T3 Al-Li alloy undergoes the hot forming with synchronous quenching process. The 2A97-T3 and 2A97-T8 Al-Li alloys are tested for high cycle fatigue under different stress amplitudes. The fatigue crack propagation path of the 2A97-T3 Al-Li alloy is not only along the direction of maximum shear stress at 45° to the stress direction but also along the direction perpendicular to the stress axis. The fatigue crack propagation path of the 2A97-T8 Al-Li alloy propagates along the direction perpendicular to the stress axis. Under high amplitude stress, the characteristics of quasi-cleavage fracture are found in the fracture morphology of 2A97-T3 Al-Li alloy. However, the characteristics of cleavage fracture are found on the fracture morphology of 2A97-T3 Al-Li alloy under low amplitude stress. Under high amplitude stress, the quasi-cleavage characteristics and the dimples are found on the fracture morphology of 2A97-T8 Al-Li alloy. Under low amplitude stress, the small voids and the dimples are found on the fracture morphology of 2A97-T8 Al-Li alloy. The precipitated phases of the 2A97-T3 Al-Li alloy are multitudinous, fine, and dispersed δ’ phases and a few T1 phases. The precipitates of the 2A97-T8 Al-Li alloy are large, fine, and acicular T1 phases and a few δ’ phases. The hot forming with synchronous quenching process significantly improves the high cycle fatigue properties of the 2A97 Al-Li alloy. In addition, the fatigue cycles, the fatigue life rise and fall plots, the S-N curves, and the fatigue crack growth behaviors of the 2A97-T3 and 2A97-T8 Al-Li alloys are obtained.

Fatigue Performance of 3D-Printed Poly-Lactic-Acid Bone Scaffolds with Triply Periodic Minimal Surface and Voronoi Pore Structures.

Bone scaffolds serve a crucial role in tissue engineering, particularly in facilitating bone regeneration where natural repair is insufficient. Despite advancements in the fabrication of polymeric bone scaffolds, the challenge remains to optimize their mechanical resilience. Specifically, research on the fatigue behaviour of polymeric bone scaffolds is scarce. This study investigates the influence of pore architecture on the mechanical performance of poly-lactic-acid (PLA) scaffolds under quasi-static and cyclic compression. PLA scaffolds with a 60% porosity were fabricated using extrusion-based 3D printing in various designs: Gyroid, Lidinoid, Fischer-Koch, IWP, and Voronoi. Results demonstrated that Gyroid scaffolds had the highest compressive strength (6.6 MPa), followed by Lidinoid, Fischer-Koch, IWP, and Voronoi designs. Increased strut thickness was linked to higher compressive strength. However, normalized fatigue resistance showed a different pattern. While scaffolds resisted fatigue cycles at low strain amplitudes, fatigue damage was observed at higher strains. Voronoi structures exhibited the highest normalized fatigue performance, enduring around 58,000 cycles at 85% strain amplitude, followed by Gyroid, Fischer-Koch, Lidinoid, and IWP structures. Enhanced fatigue performance in different topologies correlated with the minimum cross-sectional area of scaffolds. Given the importance of both static and fatigue strength, the Gyroid topology emerges as the superior choice overall.

Hysteretic behavior optimization of hollow laminated viscoelastomer-filled steel tube damper

This study proposes a shape optimization approach for designing hollow laminated viscoelastomer-filled steel tube dampers (HLVSTDs), aiming to reduce stress concentration, enhance energy dissipation capacity, and improve low-cycle fatigue performance. The shape optimization curve is obtained based on the definition of stress contours for HLVSTD bending moments and shear forces, with the assumption that points on the same contour yield simultaneously. Cyclic loading experiments were conducted on four HLVSTDs. Numerical models were established and validated to further investigate the mechanical properties, energy dissipation capacity, and seismic performance of the shape-optimized HLVSTDs. The results demonstrate that the shape-optimized HLVSTDs specimen exhibits excellent energy dissipation capacity and improved low-cycle fatigue performance. The calculated initial stiffness and yield force closely align with experimental values. Compared to non-optimized HLVSTDs, the shape-optimized HLVSTDs exhibit more uniform stress and equivalent plastic strain distributions, effectively reducing the concentration of plastic strains. Additionally, structures equipped with shape-optimized HLVSTDs demonstrate superior seismic performance.

Optimum moment to heal cracks in asphalt pavement by means of waste carbon fiber-enhanced electromagnetic induction heating during multiple damage-healing cycles

This study investigated the optimal timing for healing asphalt pavement cracks using waste carbon fibers (WCFs) reinforced electromagnetic induction (EMI) technology through multiple "damage-healing" cycles, focusing on mechanical and fatigue performance. Initially, an extensive research project was carried out to evaluate the rate of induction heating, surface temperature decline rate, and effective heating depth of the asphalt mixture. Subsequently, from a mechanical performance perspective, semi-circular bending (SCB) tests were employed. By setting four different load termination conditions, the extent of cracking in the specimens was quantitatively controlled, followed by multiple "damage-healing" tests to analyze the impact of healing timing on the mechanical properties and healing efficiency of the asphalt mixture. Lastly, from the perspective of fatigue performance, using the four-point bending fatigue test (4 PB), the fatigue damage extent of specimens was quantitatively controlled through the attenuation rate of stiffness modulus. Multiple "damage-healing" tests were carried out at four different healing timings to study the effect of healing timing on the fatigue performance and healing efficiency of the asphalt mixture. The results indicated that WCFs improved the heating performance of asphalt mixture, enabling 5 cm-thick specimens to be fully heated within 6 min. Both SCB and 4 PB tests yielded similar conclusions: in the process of multiple "damage-healing" cycles, earlier healing interventions were beneficial for the recovery and maintenance of the mechanical properties of asphalt mixtures and effectively extended their service life. However, the fatigue tests also revealed that overly early self-healing interventions, where cracks were insufficiently formed, did not fully exploit the potential of the healing process. Conversely, healing interventions conducted too late were extremely detrimental to the restoration of mechanical characteristics and the prolongation of the asphalt mixture's lifespan.

On the correlation between fatigue behaviour and the multiphase microstructure of a super duplex stainless steel

This work investigates the relationship between the multiphase microstructure and the macroscale fatigue behaviour of a cast super duplex stainless steel (SDSS). The microstructure of a cast SDSS is typically composed of a FCC γ-phase and a BCC δ-phase. However, deleterious secondary phases (SP), such as sigma and chi, may precipitate when SDSS is exposed to high-temperature ranges, jeopardising its mechanical properties, namely fatigue performance. The purpose of this investigation was to quantify the correlation between SP amounts and fatigue life of a cast SDSS (CD3MWCuN, ASTM A890). Fatigue tests were conducted using miniature specimens taken from a cast C-Ring with different SP amounts. A numerical model was proposed to calibrate the fatigue test parameters. After the tests, SEM and EBSD techniques were used to quantify the SP and analyse the fatigue-crack propagation. The microstructural analysis was complemented with hardness and tensile tests. Regression models were developed to correlate the percentage of SP, the fatigue resistance and the number of cycles to failure, and to predict the microstructural stress concentration from the amount of SP. In addition, a methodology is proposed for predicting S-N curves as a function of the amount of SP, showing a high correspondence in the increase of the percentage of SP with the decrease in fatigue life. Furthermore, the fatigue strength, for a given number of cycles to failure, tends to decrease linearly with increasing the SP, while the microstructural stress concentration factor tends to increase with an increase in SP. These findings contribute to further knowledge on predicting the behaviour of cast SDSS under different cyclic conditions, which can be valuable for optimizing design and performance in various applications.

A data-driven model for predicting fatigue performance of high-strength steel wires based on optimized XGBOOST

Fatigue damage to high-strength steel wires in cable-stayed bridges can significantly compromise bridge reliability. Previous studies have primarily focused on isolated factors such as corrosion rate or stress ratio, failing to capture the complex interactions among multiple variables. Consequently, a few researchers have developed data-driven models using machine learning methods. However, these unoptimized models exhibit limited prediction performance and convergence speed, and lack in-depth analysis of feature effects on the models. To address these shortcomings, this study combines the Gray Wolf Optimization (GWO) algorithm with the XGBoost model to create a data-driven approach for predicting the fatigue performance of high-strength steel wires under multiple influencing factors. The model is validated using both journal and experimental datasets. Results demonstrate that the proposed GWO-XGBoost model achieves high prediction accuracy (R2 = 0.94) and strong generalization ability, and exhibits rapid convergence in optimizing hyperparameters, outperforming BP neural networks and ridge regression models. Additionally, the study highlights the primary effects of wire mass loss, stress range, and average stress on fatigue life prediction, emphasizing the importance of preventing corrosion and managing stress levels to enhance wire fatigue performance. Analysis of model parameters reveals that alpha and colsample_bytree are critical for maintaining model stability and minimizing error rates, while maximum depth and learning rate significantly impact model complexity and convergence. This suggests that proper tuning of these parameters is essential for ensuring model robustness, efficiency, and generalization ability.

Research on the correlation between roughness parameters and contact stress on tooth surfaces and its dominant characteristics

The contact performance of the tooth surface is a crucial factor affecting the operational lifespan of gears. There is a significant correlation between tooth surface topography and contact stress, as well as fatigue performance. To investigate the influence of different topography parameters on tooth surface contact stress, this paper performs analytical calculations on asperity contacts of rough tooth surfaces based on reconstruction modeling. Through efficient calculations, sufficient correlation analysis data is obtained. The neural network analysis method is used to measure the degree of influence of roughness parameters on tooth surface contact performance. Research on the correlation between micro-topography parameters and maximum contact stress on tooth surfaces, as well as regression analysis, is conducted. The results show that: (1) Considering rough surfaces, the tooth surface contact stress field exhibits two stress peaks in the near-surface layer and sub-surface layer, with a maximum Mises stress increase of up to 30 % compared to a smoother surface. (2) In the case of low roughness (Sa < 0.2 μm), the amplitude of the maximum Mises stress peak in the near-surface layer is close to that in the sub-surface layer. However, as the roughness amplitude increases, the amplitude of the near-surface stress peak increases sharply. (3) Ranking the roughness parameters based on their influence on contact stress, the main parameters characterizing contact performance are identified as Spk, Vmp, and Sq. The peak characteristics of the surface are the decisive factors affecting fatigue extremes, which are stronger than the traditional surface roughness parameter Sq. This paper establishes a direct correlation model between tooth surface topography parameters and contact stress, providing a foundation for simplifying stress calculations considering complex topographies and offering new insights for fatigue-resistant design of tooth surfaces.

Effects of cutting temperature on the genes and fatigue properties of asphalt during its refining process

Asphalt binders performance is affected by refining process and crude oil. In this work, we investigated the effect of cutting temperature on the genes and fatigue properties of asphalt during asphalt refining. Five cutting temperatures (420 °C to 440 °C, interval of 5 °C) were set during the asphalt preparation, expanded the asphalt samples through ageing method. Fourier Transform Infrared (FTIR), Gel Permeation Chromatography (GPC), Nuclear Magnetic resonance Spectrum (1HNMR), Elemental analyzer, and improved Brown-Ladner method were used to characterize the asphalt genes. The fatigue performance of asphalt through Linear Amplitude Sweep (LAS) combined with the Simplified Viscoelastic Continuum Damage (S-VECD). Finally, the Pearson correlation method was used to analyze the correlation between genes and fatigue parameters of binders. The results showed that the cutting temperature and aging process changed the genes distribution of binders and these influence the fatigue properties of binders. In addition, the fatigue life of asphalt decreased at high strain levels and increased at low strain levels as the cutting temperature and the degree of ageing increased. The Pearson correlation results indicated a significant correlation between the genes and fatigue parameters of asphalt, however, the key genes affecting low-strain (2.5% and 5 %) and high-strain (10% and 20%) level fatigue in asphalt are significantly different. The outcomes of the paper provide insights about the influence of cutting temperature on the variation of asphalt genes and fatigue parameters, to allow more informed to promote of asphalt preparation.

Fatigue performance impact of hybridization on Kevlar/flax and glass/flax hybrid composites

Fatigue performance impact of hybridization on Kevlar/flax and glass/flax hybrid composites

Study on low-frequency fatigue performance of HT700P nickel–iron based high-temperature alloy

Study on low-frequency fatigue performance of HT700P nickel–iron based high-temperature alloy

Improving the fatigue life of laser powder bed fusion Scalmalloy® by friction stir processing

A major concern about parts produced by laser powder bed fusion (L-PBF) are intrinsic defects or porosities that are difficult to overcome by simply optimizing the process parameters. As these defects and porosities play a crucial role in the mechanical behaviour, especially in fatigue, additive manufactured parts are often subjected to thermo-mechanical post-treatments. To this end, this work proves Friction Stir Processing (FSP) to be an effective post-treatment to drastically reduce the porosity level. FSP leads to an improvement of 60 % of the technical fatigue strength and by two orders of magnitude of the fatigue life of L-PBF Scalmalloy® specimens. The fatigue performances obtained on FSPed and heat-treated specimens are equivalent or even better than the best fatigue life reported in the literature, whatever their L-PBF conditions and post-treatments, while avoiding Hot Isostatic Pressing. However, FSP reduces the beneficial effect of the conventional strengthening heat-treatment applied to L-PBF Scalmalloy®, lowering the high tensile strength for which the alloy is normally reputed. Advanced characterisation by X-ray microtomography and Transmission Electron Microscopy allows us to reach a better understanding of the involved phenomena: drastic reduction of the biggest defects and heterogeneous nucleation of Sc- and Zr-rich precipitates on grain boundaries and dislocations.

Numerical study and experimental validation of heat transfer capacity of flat-type divertor for fusion reactor

The divertor must simultaneously withstand unprecedented high heat fluxes of up to 20 MW/m2 and high-energy neutron irradiation of 14-MeV during fusion reactor operation. Accordingly, it is necessary to simultaneously meet the excellent heat dissipation capacity of the divertor and maintain good material performance in harsh neutron irradiation environments. The flat-type divertor demonstrates better heat transfer performance compared to monoblock divertor. Nevertheless, under the condition of a heat flux of 20 MW/m2, the heat transfer and thermal fatigue performance of flat-type divertor using advanced materials are still unidentified. In this study, we conducted a thorough analysis of the heat transfer capabilities and thermal fatigue characteristics of potassium-doped tungsten (KW)/Cu/Oxide dispersion strengthened copper (ODS-Cu)/reduced activation ferritic/martensitic (RAFM) divertor mockup adopts hypervaportron (HV) structure by numerical simulations combined with experiments. The numerical results indicate that the flat-type KW/Cu/ODS-Cu/RAFM divertor mockup expresses excellent heat transfer capacity. The contact area between the edge of the fins and the bottom surface of the ODS-Cu heat sink induces a significant increase in water flow velocity to ∼15 m/s. The peak temperature of loaded KW surface is only ∼985 °C under the flow rate of 5 t/h and inlet temperature of 20 °C. During the high heat flux tests, the prepared flat-type divertor mockup successful endured 1000 cycles of 20 MW/m2 with the peak temperature of 883 °C, and the surface temperature experienced a fluctuation of 2.4 % during the thermal fatigue tests. This study can provide a strong data reference and technical support for the development of fusion reactors, and is of great significance in advancing the commercialization of fusion energy.

Fatigue performance of bonding‐assisted fillet weld roots by inserting adhesive material

AbstractThis 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.

Study of tensile‐tensile fatigue behavior of patch repaired carbon‐glass hybrid composite

AbstractAside from the numerous benefits of fiber‐reinforced composites, these materials are prone to impact damage, reducing structure's strength and stiffness. In this case, composite repair offers a unique and cost‐effective alternative for restoring structural integrity. In this work, post‐repair performance of the carbon‐glass hybrid composite is investigated in tensile‐tensile fatigue loading environments. To analyze repair performance, two distinct parent configurations (H1:G2C4G2 and H2: C2G4C2) and four patch configurations (Repaired1: CG3, Repaired2: C2G2, and Repaired3: C3G, Repaired4: G4) are considered. The digital image correlation approach and acoustic emission sensors are used to examine the specimens' damage behavior. First, fatigue tests are performed for drilled specimens, the H2 specimen dissipate more energy during fatigue cycles than the drilled H1 specimen due to the early damage initiation in the H2 specimen. The repaired specimens with the parent H1 laminate performed better than the parent H2 laminate. The Repaired4 configuration with H1 parent laminate sustained 300% higher cycles than the drilled H1 without final failure, which showed the highest fatigue life among all the repaired configurations. Patches with fewer glass plies outperformed all hybrid patches. The damage events recorded by acoustic emission sensors indicate that delamination damage considerably impacts fatigue life.Highlights Post‐repair fatigue behavior of carbon‐glass hybrid composite was examined. Effect of parent laminate stacking sequence and patch configuration was studied. Fatigue performance was analyzed using the damage mode and energy loss factor. Digital image correlation technique and acoustic emission sensors were utilized. Delamination damage showed a higher impact on the fatigue life of the sample.