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Aluminum alloys are primary structural materials in aircraft fuel systems, where jet fuel can influence the fatigue crack growth (FCG) behavior of materials. This paper presents a model for calculating the FCG rate of aluminum alloys in jet fuel environment. The model is based on elastoplastic fracture mechanics and revises the interaction terms in the linear superposition model by accounting for the corrosive environment and the crack closure effect. The derivation process of the model is discussed in detail. To validate the efficacy of the model, FCG tests were conducted on three types of aviation aluminum alloys, namely, 2524‐T3, 7050‐T7451, and 7075‐T62 in the jet fuel. The experimental results were compared with FCG rates in the laboratory air environment. Findings indicate that the proposed model effectively captures the primary trends observed in the experimental data. In addition, the failure surfaces of the specimens were observed using a super‐depth‐of‐field optical microscopy system. [ABSTRACT FROM AUTHOR]

Constant amplitude loading fatigue tests were carried out for 7075/2A12 dissimilar aluminum alloy friction stir welding (FSW) lap joints, and the fatigue fracture characteristics were observed accordingly. Experimental observation suggested that the effective lap sheet thickness had a salient effect on the fatigue strength of the specimen. Specimens tend to fail at the lower sheet thickness under low relatively loading, while fail at the hook root at higher loading. There exists a competition between the two failure cases, and the fracture site changes with loading levels. The stress/strain at the periphery of the weld nugget were discerned by elastic and elasto–plastic finite element analyses respectively, which were then utilized to evaluate the fatigue life by local life prediction approaches and notch stress methods. Two widely used local stress approaches, the Morrow's modified Manson-Coffin (MMC) damage model and the Smith-Watson-Topper (SWT) damage model both could give reasonable results relatively close to experimental lives within the low cycle life regime. The notch stress method could give relatively closer life in the high cycle life regime. [ABSTRACT FROM AUTHOR]

Ball burnishing (BB) is a surface finishing process that involves moving the tool while pressing it against the workpiece under rolling contact. We investigated the effects of BB on the fatigue strength of an aluminum alloy with a semicircular slit simulating an initial surface defect. After performing BB under a typical condition, compressive residual stress was induced to a depth of 0.4 mm, with a reduction in surface roughness by 81%. Consequently, the fatigue strength increased by 22%. BB prevented the fatigue strength reduction caused by the 0.1 mm deep slit. The result indicated that BB could render the below 0.1 mm deep surface defect harmless in terms of fatigue strength. The maximum depth of surface defect that can be rendered harmless is 0.18 mm according to fracture mechanics, which is in agreement with the experimental results. Highlights: Ball burnishing (BB) can introduce large compressive residual stress along with smoothing.BB can render a 0.1 mm deep slit harmless in terms of fatigue strength.Defect size rendered harmless can be estimated based on fracture mechanics.Compressive residual stress is the main factor rendering the surface defect harmless. [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. [ABSTRACT FROM AUTHOR]

The effect of anisotropy on high‐cycle fatigue (HCF) property along the rolling direction (RD) and the transverse direction (TD) of a 7××× aluminum alloy super thick plate is mainly investigated in this study. The results show a similar microstructure at different thicknesses, and the HCF properties are close as well. The fatigue fracture morphologies show that the fatigue crack sources are all located on the surfaces of the RD and TD specimens. By considering the differences in the HCF properties, there is only a slight anisotropy effect at the center thickness of the plate, which can be attributed to the tensile anisotropy caused by textures. Besides, the fatigue damage degree along the TD is slightly higher than that along the RD at the center thickness. The reason can be explained by two aspects: one is the higher probability of defect occurrence along the TD compared with that along the RD which is analyzed by the previously proposed Yield strength‐Tensile strength‐Fatigue strength model, and the other is the influence of the textures. The combination of hard and soft orientations may cause fatigue damage localization easily in the soft‐oriented grains which accelerates the fatigue failure. [ABSTRACT FROM AUTHOR]

It is well known that errors are inevitable in experimental observations, but it is equally unavoidable to eliminate errors in modeling the process leading to the experimental observations. If estimation and prediction are to be done with reasonable accuracy, the accumulated errors must be adequately managed. Research in fatigue is challenging because modeling can be quite complex. Furthermore, experimentation is time-consuming, which frequently yields limited data. Both of these exacerbate the magnitude of the potential error. The purpose of this paper is to demonstrate a procedure that combines modeling with independent experimental data to improve the estimation of the cumulative distribution function (cdf) for fatigue life. Subsequently, the effect of intrinsic error will be minimized. Herein, a simplified fatigue crack growth modeling is used. The data considered are a well-known collection of fatigue lives for an aluminum alloy. For lower applied stresses, the fatigue lives can range over an order of magnitude and up to 107 cycles. For larger applied stresses, the scatter in the lives is considerably reduced. Consequently, modeling must encompass a variety of conditions. The primary conclusion of the effort is that merging independent experimental data with a reasonably acceptable model vastly improves the accuracy of the calibrated cdfs for fatigue life, given the loading conditions. This allows for improved life estimation and prediction. For the aluminum data, the calibrated cdfs are shown to be quite good by using statistical goodness-of-fit tests, stress-life (S-N) analysis, and confidence bounds estimated using the mean square error (MSE) method. A short investigation into the effect of sample size is also included. Thus, the proposed methodology is warranted. [ABSTRACT FROM AUTHOR]

This study develops a rapid algorithm coupled with the finite element method to predict the fatigue crack propagation process and select the enhancement factor for the equivalent random load spectrum of accelerated fatigue tests. The proposed algorithm is validated by several fatigue tests of an aluminum alloy under the accelerated random load spectra. In the validation process, two kinds of panels with different geometries and sizes are used to calculate the stress intensity factor, critical crack length, and crack propagation life. The simulated and experimental findings indicate that when the aluminum alloy is in a low plasticity state, the crack propagation life exhibits a linear relationship with the acceleration factor. When the aluminum alloy is in a high plasticity state, this study proposes an empirical formula to calculate the equivalent stress intensity factor and crack propagation life. The normalized empirical formula is independent of the geometry and size of different samples, although the fracture processes are different in the two kinds of panels used in our study. Overall, the numerical method proposed in this paper can be applied to predict the fatigue crack propagation life for the random spectrum of large samples based on the results of the simulated accelerated crack propagation process and the accelerated fatigue tests of small samples to reduce the cost and time of the testing. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop an analytical model to predict the fatigue life of aluminum alloy panels repaired by a carbon/epoxy patch. The study includes two parts: an experimental part where fatigue tests were conducted on notched specimens of 2024 T3 and 7075 T6 aluminum alloys repaired by unidirectional carbon/epoxy patches in order to measure the crack propagation rate (da/dN) after bonding of the patch. The second part of the work consists in numerically calculating the stress intensity factor range (ΔK) at the tips of repaired cracks. A fatigue life prediction model was established for repaired plates based on the Paris law. This model relates the Paris constants to the stiffness ratio between the patch and the aluminum plate. The model of fatigue life prediction can be useful for the patch repair designers. The obtained results show that the fatigue life is highly improved by the composite patch specially for the aluminum alloy 2024 T3. The number of cycle at failure increases with the increase of the patch thickness. The stress intensity factor at the crack tip is reduced by the patch repair which leads to a slowdown in the propagation of the crack. [ABSTRACT FROM AUTHOR]

This document is a compilation of various research papers and articles that discuss the use of machine learning and other techniques to predict fatigue lifetimes in different materials and structures. The papers cover topics such as the use of neural networks, XGBoost, and physics-informed machine learning models for fatigue prediction. The research focuses on different materials, including aluminum alloys and lead-free solders, and explores the effects of factors such as wear, lubrication, corrosion, and stress on fatigue life. The papers provide insights into the application of machine learning techniques in predicting fatigue lifetime and offer potential solutions for improving the accuracy of these predictions. [Extracted from the article]

A three‐parameter Weibull small sample aggregation method is proposed to address the problem of small sample fatigue data in practical engineering. First, based on the empirical assumption that the shape parameter is a constant and data equivalent conversion and aggregation, the small sample fatigue life data are converted into "equivalent large samples." Second, through the linear relationship between logarithmic scale parameter and stress, an iterative procedure is established to estimate the scale parameters of small sample data. At the same time, the moment and rank estimation methods are used to solve the location parameters quickly. Finally, P–S–N curves with different survival rates are given, and a 7‐series aluminum alloy is selected to verify the correctness and reliability of the method proposed in this study. The results show that the predicted life obtained by the method still has high accuracy under a high survival rate, which can provide a theoretical basis for solving practical engineering problems. Highlights: A three‐parameter Weibull small sample aggregation method is proposed.The WSSA program is used to estimate the P–S–N curve of small sample data.The fatigue data of aluminum alloys verify the effectiveness of this method. [ABSTRACT FROM AUTHOR]

Fretting fatigue is a specific fatigue phenomenon. Due to the complex mechanisms and multitude of influencing factors, it is still hard to predict fretting fatigue life accurately, despite there being many works on this topic. This paper developed a particle-swarm-optimized back propagation neural network to predict the fretting fatigue life of aluminum alloys using the test data gathered from the published literature. A commonly used critical plane model, the Smith, Watson, and Topper criterion, was used as a contrast. The analysis result shows that the proposed fretting fatigue life prediction neural network model achieves a higher prediction accuracy compared to the traditional SWT model. Experimental validation demonstrates the effectiveness of the model in improving the accuracy of fretting fatigue life prediction. This research provides a new data-driven methodology for fretting fatigue life prediction. [ABSTRACT FROM AUTHOR]

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A certain number of hole-like defects will occur in aluminum alloys under cyclic loading. The internal holes will reduce the strength of the material and cause stress concentration, which will aggravate the development of fatigue damage. A classification method of defect features based on X-ray CT damage data is proposed. The random hole distribution model is established through the linear congruence method and the region division method. The hole parameter is introduced as the intermediate variable of the 3D reconstruction model of internal defects. In the mesoscopic stage, the function relationship between the distribution of random holes and the fatigue life is established based on the coupling relationship between the number and proportion of pores and the fatigue life. In the macroscopic stage, the relationship between the random holes and the macroscopic crack growth life is established by taking the crack length as the damage variable. The crack propagation rate decreased with the increase in the number of holes. The prediction model of the whole life stage is established using the life function from microcrack initiation to macroscopic crack propagation. Finally, the validity of the whole stage fatigue life prediction model is demonstrated through the comparison and verification of experiments, which provides a certain engineering value for the life estimation of 6061-T6 aluminum alloy materials. [ABSTRACT FROM AUTHOR]

With an electroless Ni-P (EN) layer thickness of 38-40 lm and a high P content of around 18 wt.%, the fatigue and corrosion-fatigue properties of a 7075-T6 aluminium alloy have been investigated. The findings demonstrate that the EN layer significantly enhances the substrate's resistance to fatigue and corrosion fatigue, but how much this happens depends on how the testing was set up. As the amount of alternating stress increases, the rise in fatigue characteristics seen during air tests of the coated system goes down. The fatigue life is almost doubled when there are between 0.4% and 0.2% of stresses. At 0.7% to 0.2% stress, however, the system's fatigue performance is not much different from that of the uncoated base. It is said that corrosion-fatigue conditions can improve fatigue life by up to 70%, depending on how hard the stress is. It has been proven that wear cracks cause bumpy spots on the surface of the coating. More alternating pressure makes the bad effects of these abnormalities worse. Meyer's law can be used to figure out the absolute hardness of the deposit, which can be estimated to be around 4 GPa based on the EN coating's yield strength, which can be measured using the tension method. It is also shown that the EN deposit sticks onto the base very well. Still, the system is put through tensile loads higher than the yield strength. In addition to these benefits, the coated system works better under stress because the EN coating has better mechanical properties than a substrate made of aluminium alloy and can keep the structure's consistency despite exhaustion tests. [ABSTRACT FROM AUTHOR]

Results of tensile and low-cycle fatigue testing of samples made of an aluminum–lithium alloy of the Al–Mg–Li system obtained by plasma-assisted laser cutting performed by a pulsed CO2 laser in an argon jet with the laser beam and optical discharge plasma simultaneously affecting the material are reported. Low-cycle fatigue tests show that the number of loading cycles survived by the sample obtained by plasma-assisted laser cutting is more than twice greater than the number of cycles survived by the samples obtained by conventional laser cutting with a continuous beam. [ABSTRACT FROM AUTHOR]

This paper evaluates the influence of contact pressure on the surface contact state, fretting damage degradation mechanism, crack initiation and propagation characteristics, and fretting fatigue life of A319‐T6 cast aluminum alloy in fretting fatigue test using bridge‐type fretting pad. For a certain range of contact pressure, the fretting fatigue life exhibits a trend of increasing and subsequently decreasing with increasing contact pressure. With finite element analysis, the fretting contact region can be divided into two characteristic zones according to the dynamic evolution of the contact status within one fatigue cycle. The contact pressure affects both the distribution of the two characteristic zones as well as the relative slip range, which results in distinct fretting damage mechanisms. The nucleation characteristics and propagation paths of fatigue cracks under three typical contact pressures were analyzed considering the effects of fretting damage and heterogeneous microstructures of the alloy, accounting for the contact pressure dependency of the fretting fatigue life. Highlights: The dynamic evolution of the contact status affected by contact pressure is considered.The fretting damage evolution with the variation of contact pressure is evaluated.The nucleation characteristics and propagation paths of fatigue cracks are elaborated.The contact pressure dependency of the fretting fatigue life is summarized. [ABSTRACT FROM AUTHOR]

Background: Extensive research was conducted to analyze the ultrasonic fatigue behavior of ASGU-T64 cast aluminum alloy under different humidity environments. The study placed particular emphasis on investigating the factors influencing crack initiation, as well as the propagation of both short and long cracks. By examining the alloy's performance in various moisture conditions, a comprehensive understanding of its fatigue behavior was achieved. Objective: The primary objective is to elucidate the mechanism underlying crack initiation and accurately predict the lifespan of short and long cracks. The ultimate goal is to determine how crack initiation size affects the percentage of crack initiation life in relation to the overall fatigue life. Method: Scanning Electron Microscope (SEM) and Electron Back Scatter Diffraction (EBSD) were employed and provided valuable insights into the characteristics of the facets. Furthermore, computational methods were utilized, employing the Paris crack growth law, to accurately determine the growth lives of both short and long cracks. By combining experimental and computational approaches, a comprehensive understanding of the fracture behavior and crack growth mechanisms was achieved, contributing to the advancement of knowledge in this field. Results: Through this study, it was discovered that fatigue cracks in the AS7GU-T64 alloy consistently initiated on the surface of the sample, primarily due to the presence of persistent slip bands (PSBs). Each facet observed on the fracture surface corresponded to an entire grain within the short crack area. While the stress intensity factor fell within the range of 3.5 to 10 MPa·√m for all three environments, it was found that the stress intensity factor in dry air exceeded that of saturated air and distilled water conditions. Importantly, the percentage of fatigue life attributed to crack initiation was found to be heavily dependent on the humidity of the testing environment and the applied stress amplitude. These insights highlight the intricate relationship between environmental conditions, stress intensity factor, crack initiation, and the overall fatigue life of the AS7GU-T64 alloy. Conclusion: Humidity negatively affects the ultrasonic fatigue life of the AS7GU-T64 alloy. Furthermore, the size of crack initiation was identified as a significant factor influencing the percentage of crack initiation life in relation to the overall fatigue life. [ABSTRACT FROM AUTHOR]

Detecting mechanical fatigue of metallic components is always a challenge in industries. In this work, we proposed to monitor the low-cycle fatigue of a 6061 aluminum alloy based on internal friction (IF) measurement, which is realized by a quantitative electromechanical impedance (Q-EMI) method using a small piezoelectric wafer bonded on the specimen. Large stress amplitude (230 MPa) was employed in the testing; thus, the fatigue life can always be below 105 cycles. It was found that except for the initial testing stage, the IF always increases steadily with the increasing fatigue cycles. Before the fatigue failure, the IF can reach 2.5–3.4 times the initial value, which is thought to be caused by the micro-cracks forming and growing. In comparison, the resonance frequency of the specimen just drops by about 2% compared with the initial value. Finally, a fatigue criterion based on IF measurement is suggested for aluminum alloys and it can also be extended to other metals. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the feasibility of joining ZEK100-O magnesium alloy to AA7072-clad high-strength AA7075-T6 aluminum alloy via solid-state ultrasonic spot welding (USW) and evaluate interfacial microstructures, tensile lap shear strength, and fatigue resistance. Distinctive "fishhook"- or "wave"-like mechanical interlocks were observed to form at the weld interface between the magnesium and aluminum alloys due to the presence of softer clad layer of AA7072 with ~ 1% Zn. This led to the enhanced tensile lap shear strength of the dissimilar welded joints, with the peak value emerging at a welding energy of 1000 J. Besides the mechanical bonding via effective interlock mechanism, a thin diffusion layer consisting of α-Mg + Al12Mg17 eutectic structure at 1000 J was also beneficial for attaining superior tensile lap shear strength and longer fatigue life, in comparison with other Mg/Al dissimilar joints without a clad layer. While interfacial failure predominated in the tensile lap shear tests, fatigue failure changed from the interfacial failure mode at the higher cyclic loading level, to a mixed mode of both interfacial and transverse through-thickness (TTT) failure at the intermediate loading level, and to full TTT failure at the lower loading level. [ABSTRACT FROM AUTHOR]

The paper aims to investigate the fatigue behavior of the widely used AA2024‐T351 aluminum alloy in the aircraft industry. An experimental program was conducted to study the fatigue life and damage behavior under symmetrical tensile‐compressive loading. Cyclic tests in the low cycle fatigue regime were performed under fully reversed total strain amplitudes from 0.6% to 1.2%. The AA2024‐T351 alloy exhibited cyclic hardening until failure. Symmetric high cycle fatigue tests were also performed and the parameters for fatigue life estimation using the Manson–Coffin–Basquin model were identified. Elasto‐plastic behavior was analyzed through stress–strain hysteresis loops, evaluating kinematic and isotropic hardenings. Kinematic hardening was found to be strain amplitude dependent, unlike the isotropic hardening. The evolution of the isotropic variable with the percentage of fatigue life could be described by an exponential law. Fractography investigations showed crack initiation at the specimen border with quasi‐cleavage and then crack propagating by striation before ductile fracture. Highlights: Low cycle and high cycle fatigue of the AA2024‐T351 aluminum alloy was investigated.The fatigue life was described by the Manson–Coffin–Basquin law.Isotropic and kinematic hardenings were used to model elasto‐plastic cyclic behavior.Fractography investigations using scanning electron microscopy were conducted. [ABSTRACT FROM AUTHOR]

Fatigue strength tests of Ti-coated aluminum alloys with a thickness of 1 µm, 3 µm, and 5 µm were conducted to investigate the effect of the coating thickness on fatigue strength. Under the same applied stress amplitude, the optimum thickness with the most-extended fatigue life was around the coating thickness of 5 µm. This may be attributed to the good resistance to surface cracks under repeated loads. The results suggested that a lower fatigue life of a coating thickness of 1 µm results from the fracture of the coating layer under the strong influence of the deformation of the substrate. This could be due to the higher tensile residual stress induced in the substrate near the coating layer and substrate interface. The titanium coating restricted the initiation of offsets and cracks beneath the surface of the specimen, which may be attributed to the high strength of the Al–5%Si substrate, good flexibility, and strong adhesion, which provided sufficient compressive stress to suppress slip band protrusions. The fatigue life and fatigue limit increased proportionally to the thickness of the titanium coating due to changes in the surface roughness and adhesion capability. [ABSTRACT FROM AUTHOR]

To accurately predict the fatigue life of cast aluminum alloy wheels, based on the results of finite element calculation and simulation, this work selected the rim area, inner flange and spoke areas to conduct systematic tensile and high‐cycle fatigue tests. The results show that the tensile properties of A356‐T6 cast aluminum alloy wheels are similar in various areas, but the fatigue properties are significantly different. Plastic deformation can improve the fatigue strength of the aluminum alloy, but the fatigue properties are also affected by deformation uniformity and other factors. Based on the difference of mechanical properties in different areas, this study also selected the characteristic loading spectrum to predict the fatigue life of wheels. A linear and a nonlinear damage accumulation were employed. The above methods are not only applicable to the wheel, but also provides a new idea for the life prediction of key parts in the engineering field. Highlights: Systematically test and characterize the difference of fatigue performance of each part of casting and spinning aluminum alloy wheel.The smaller the SDAS is, the better the fatigue performance is not necessarily. The coordinated deformation ability and plastic deformation will have a significant impact on the fatigue performance.Based on LBF load spectrum, the fatigue life of casting and spinning wheel is predicted, and the influence of different damage models on the fatigue life prediction results is analyzed. [ABSTRACT FROM AUTHOR]

Nowadays, engine components are subjected to higher loads at elevated temperatures due to the increasing requirements regarding weight, performance, and exhaust gas emission. Thus, fatigue due to simultaneous thermal and mechanical loading became a determinant among the damage forms. The effect of a thermal barrier coating (TBC) on the thermal stress and fatigue life in a gasoline engine piston with considering stress gradient was studied. For this purpose, coupled thermo-mechanical analysis of a gasoline engine piston was performed. Then fatigue life of the component was predicted using a standard stress-life analysis and results were compared to the original piston. The results of finite element analysis (FEA) indicated that the stress and number of cycles to failure have the most critical values at the upper portion of piston pin and piston compression grooves. The obtained thermomechanical analysis results proved that the TBC system reduces the stress distribution in the piston by about 2.4 MPa and 8.5 MPa at engine speeds of 1000 rpm and 5000 rpm, respectively. The fatigue life results showed that the number of cycles of failure for the coated piston is approximately 12% and 31% higher than the original piston at engine speeds of 1000 rpm and 5000 rpm, respectively. To evaluate properly of results, stress analysis and fatigue life results is compared with experimental damaged piston and it has been shown that critical identified areas, match well with areas of failure in the experimental sample. [ABSTRACT FROM AUTHOR]

In this paper, the hardness, ultimate tensile strength, yield strength, elongation E100, S−N curves, and fatigue performance of 7075 aluminum alloy were obtained after aged at 170 °C for different times (10 h, 15 h, and 20 h). Additionally, the microstructure and fatigue fracture of the alloy were observed. The investigation results show that as the forming time increased, the hardness, ultimate tensile strength, and yield strength decreased, the elongation first decreased, then increased, and the fatigue limit increased. As the forming time increased, the metastable phase gradually transformed into a steady phase and coarsened, the width of precipitate free zone increased, and the width of the fatigue strip decreased. After creep age forming for 20 h, the precipitate free zone was the widest, approximately 100 nm. [ABSTRACT FROM AUTHOR]

The effects of artificial‐aging time on monotonic properties and torsional fatigue of AA6351 aluminum alloy were studied in this paper. Fatigue tests were carried out by the strain‐controlled condition. Monotonic and cyclic torsional behavior, fatigue life, and estimation methods were verified. Results showed the distance between monotonic and cyclic curves progressively decreased as aging time increased from 1 to 2 and 6 h at 170°C. The yield strength values were subsequently 74.5, 110.7, and 142.5 MPa for monotonic torsion and 127, 145, and 160 MPa for cyclic torsion test (half‐life). Alloy in all aging times showed similar fatigue life in high cycle (N f > 105 cycles), and time 1 h, longer fatigue life in low cycle (Nf < 104 cycles). All specimens presented cyclic hardening at strain amplitudes ranges tested. The estimation methods showed good prediction for the fatigue parameters. Highlights: Torsional fatigue of AA6351 alloy for different artificial aging times was studied.Monotonic and cyclic behavior, fatigue life, and estimation methods were verified.The alloy with 1 h of aging presented continuous cyclic hardening and longer fatigue life in LCF.Estimation methods showed good prediction for the fatigue parameters. [ABSTRACT FROM AUTHOR]

The fatigue failure mechanism of bending fretting for cyclic softening material 6061-T6 aluminum alloy was researched by experiment and finite element method. The influence of cyclic load on bending fretting fatigue was researched and the damage characteristics under different cycles was discussed experimentally though SEM images. In the simulation, a normal load transformation method was employed to obtain a simplified two-dimensional model used for simulating the bending fretting fatigue from a three-dimensional model. An advanced constitutive equation with the Abdel–Ohno rule and isotropic hardening evolution was transplanted into ABAQUS by UMAT subroutine to consider the ratchetting behavior and cyclic softening characteristics. The peak stain distributions under various cyclic loads were discussed. Additionally, the bending fretting fatigue lives and crack initiation locations referring to a critical volume method were estimated using the Smith–Watson–Topper critical plane approach and reasonable results were obtained. [ABSTRACT FROM AUTHOR]

Fatigue crack growth in thick‐section metals is typically controlled by an internal plane strain region where strong triaxial constraint of the crack tip occurs. However, the crack tip stress state in this region is challenging to measure. We have used neutron diffraction to study the plane strain section of fatigue crack tips in situ. A stroboscopic form of neutron diffraction using a moving frame‐of‐reference was developed to measure crack tip strains as a function of phase in the fatigue loading cycle without interrupting the cyclic load. Using point measurements of near‐tip strain in 7475‐T7351 aluminium alloy in conjunction with finite element analysis, we can estimate the extent of the crack tip plastic zone, verifying that it is small for this material and set of loading conditions. Highlights: We demonstrate stroboscopic neutron diffraction with an Eulerian frame‐of‐reference.This measures strain at the interior of a fatigue specimen without interrupting a test.Cyclic crack tip strains during fatigue of a 7xxx aluminium alloy have been observed.This near‐tip strain information can be used to validate FEA models of fatigue. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive experimental investigation of the high-cycle fatigue (HCF) behaviour of the ductile aluminium alloy AA 5083-H111. The analysed specimens were fabricated in the rolling direction (RD) and transverse direction (TD). The HCF tests were performed in a load control (load ratio R = 0.1) at different loading levels under the loading frequency of 66 Hz up to the final failure of the specimen. The experimental results have shown that the S–N curves of the analysed Al-alloy consist of two linear curves with different slopes. Furthermore, RD-specimens demonstrated longer fatigue life if compared to TD-specimens. This difference was about 25% at the amplitude stress 65 MPa, where the average fatigue lives 276,551 cycles for RD-specimens, and 206,727 cycles for TD-specimens were obtained. Similar behaviour was also found for the lower amplitude stresses and fatigue lives between 106 and 108 cycles. The difference can be caused by large Al6(Mn,Fe) particles which are elongated in the rolling direction and cause higher stress concentrations in the case of TD-specimens. The micrography of the fractured surfaces has shown that the fracture characteristics were typical for the ductile materials and were similar for both specimen orientations. [ABSTRACT FROM AUTHOR]

Anodizing process is largely performed on aluminum alloys to enhance corrosion and wear resistances. However, this process can significantly reduce the fatigue resistance of aluminum alloys depending on the alloy and the process parameters. This paper deals with the influence of anodizing process on fatigue resistance of the aeronautical aluminum alloy 2618-T851. The anodic film has been characterized after each step using scanning electron microscopy (SEM). This analysis showed that the anodic layer was crazed just after impregnation operation with micro-cracks extending from the surface up to half the anodic layer. Simultaneously, uniaxial fatigue tests under tension or torsion loadings have been conducted in order to evaluate the effect of each process step in relation with loading nature. The results showed that the anodizing step has a detrimental effect on fatigue life of 2618 alloy when specimens are subjected to tensile loading. However, anodizing process has no effect on fatigue life under torsion loading. Fractographic observations have been conducted in order to get an insight on the mechanisms involved in each case. [ABSTRACT FROM AUTHOR]

It is sparse and inconclusive that research on the subject whether the fatigue life of the structure will be reduced by shot peening strengthening before shot peen forming (S + F), and this study investigates accordingly. First, the crack growth rate test of the machine-processing plate and shot peening strengthening before shot peen forming plate demonstrate that both plates' final crack growth rate and length are similar. However, the test shows the "fluctuation phenomenon" of crack growth rate and the "intersection phenomenon" in the Paris curve. This study is based on a self-developed simulation plugin for crack growth paths. The results verify that "fluctuation" causes the differential distribution of the overall stress intensity factor in the strengthened (4.5% increase compared to machine-processing) and formed (9.8% decrease compared to machine-processing) crater areas of the shot peening strengthening before shot peen forming plate. Comparing to the full coverage strengthening area, the forming area (only 30% coverage) in the early stage of growth as well as the gain amplitude of the residual stress in the late stage of growth gradually decrease and tend to be the same as that of the machine-processing, as validated by the "intersection phenomenon". [ABSTRACT FROM AUTHOR]

Severe casting defects exist on the cavity surface of aero-engine integral casting casing, leading to substandard cleanliness and surface integrity, which restricts the service performance of the casing. The finishing process for the complex cavity of casting casing is one of the technical bottlenecks in aero-engine manufacturing. Vibratory finishing has excellent potential for closed cavities because of the process media's fluidized nature. In this work, taking the particle separator main casing of turboshaft aero-engine as a practice, based on the principle of vibratory finishing, a new idea of pre-loading the media and changing the spatial posture of the casing was proposed, and processing experiments were carried out. The vibration acceleration of the casing and the dynamic stress generated on the surface were measured, and the unfinished and finished surfaces were analyzed. The dynamic stress on the casing surface is far less than the fatigue strength of aluminum alloy (AlSi7Mg), which proves the feasibility of vibratory finishing for the casting casing. Meanwhile, the collision and scratching of the steel shot caused the surface roughness of the cavity to drop by 2 ~ 4 grades, and most of the carbon elements were removed. The finished surfaces had better surface morphology and cleanliness. Denser oxide film and lower surface roughness significantly improved the service performance of the casing, in which the corrosion resistance and mechanical properties were improved considerably. This process can provide a new approach for cavity finishing of other types of casings. [ABSTRACT FROM AUTHOR]

Defects such as porosity and cracking are serious problems in the joining of aluminium and its alloys by melt welding methods. In this case, it is important that the aluminum pairs are welded by friction stir welding (FSW), which is depend on joining at a temperature below the melting temperature by means of a stirrer pin. In this study, AA5182 pairs were joined in the different welding parameters by FSW. The effects of tool pin profily, feed rate and rotation speed on the temperature, force and vibration formed during welding were experimentally investigated. As the rotation speed rised, the temperature increased and the welding force decreased. But, with increasing feed rate, the temperature decreased and welding force and vibration have increased. Mechanical properties of the joints were adversely affected by low temperature, high welding force and high vibration. [ABSTRACT FROM AUTHOR]

Self-piercing riveting (SPR) is a suitable technology to join various materials and has attracted more attention in the automotive industry. In this work, the effects of forming parameters on the forming qualities and mechanical properties of B1500HS steel/AA5052 aluminum alloy SPR joints were analyzed. The results show that the sheet stack sequence has little influence on the peak tensile load and rigidity of SPR joints. When the steel sheet is placed on the aluminum sheet, the failure displacement, energy absorption, and ductility factor are, respectively, 2.77, 2.13, and 2.28 times larger than those of the joints with the aluminum sheet placed on the steel sheet. The SPR joints with steel sheets placed on aluminum sheets have better mechanical stability. Meanwhile, when the steel sheet is placed on the aluminum sheet, the fatigue life of the joint can be increased by about 98.4%, 88.3%, and 118.1%, respectively, under high, medium, and low fatigue loads. A joint with opposite riveting direction has the optimal fatigue performance and the fatigue life is 1.64 and 2.14 times those of the other two-rivet joints. Generally, the fatigue fractures of aluminum alloy sheets in SPR joints occurred in fatigue tests. The fatigue fracture of a joint with a steel sheet stacked on an aluminum sheet extends uni-directionally to the edge of the sheet from the riveting point, while a symmetric fatigue crack of aluminum occurs for joints with the opposite sequence. The distribution of fatigue cracks is related to fatigue load, and fatigue cracks mainly originate in the fretting wear area of the contact interface between the rivet leg, upper sheet, and lower sheet. [ABSTRACT FROM AUTHOR]

Crack tip shielding mechanisms, such as crack branching or crack closure, may also affect FCG rate (da/dN). Impurities hindered crack propagation, changed its direction, and demonstrated a stepped fatigue strip distribution morphology; in the process of the main crack propagation, the initiation and propagation of small cracks were easily restricted and hindered by the main crack. Steel structures are widely used in engineering structures due to their high strength, light weight, and good ductility; however, under strong earthquakes, steel structures will encounter fracture damage due to ultra-low cycle fatigue (ULCF). This study assesses the feasibility of using the laser cladding technique for light rail applications and establishes the most suitable cladding alloys and laser cladding process parameters. [Extracted from the article]

Objective This study aims to investigate the influences of aluminum alloy lining structure parameters on the overall fatigue performance of type Ⅲ hydrogen cylinder, and obtain the optimal design scheme of lining which can improve the long-term performance of gas cylinder. Methods Based on orthogonal test and numerical simulation, the fatigue life of composite material gas cylinder is calculated by Brown-Miller algorithm. Through correlation analysis, the influences of cylinder wall thickness, length-diameter ratio and head ellipsoid ratio on fatigue performance are comprehensively evaluated, and the main factor is confirmed to be cylinder wall thickness. Based on Goodman average stress correction equation, the variation of lining stress amplitude with the increase of wall thickness is analyzed. The optimal design is verified by the normal temperature pressure cycle test. Results The actual fatigue life of cylinders is in good agreement with the simulation results, and the final cycle times are 5.7%, which is different from the simulation results. The fatigue failure position of gas cylinder appears in the lining cylinder body, and the fatigue failure of aluminum alloy lining is earlier than that of fiber winding layer. Conclusions The fatigue life of the optimized composite material gas cylinder is 44.7% longer than that of the standard. It is feasible to optimize the lining structure parameters of type III hydrogen cylinder by orthogonal test. [ABSTRACT FROM AUTHOR]

Tartaric–sulfuric acid (TSA) anodizing is an electrochemical process used for generating an anodic layer on the surface of aluminum alloys for aerospace applications. It must provide corrosion resistance and ensure no detrimental effect on the required fatigue properties for structural applications. This work aimed at analyzing the properties of the anodic layer and evaluating its influence on the fatigue behavior of the AA 7050‐T7451. The film properties were analyzed using optical and scanning electron microscopies. The surface residual stress (SRS) field in the as‐machined and anodized conditions was evaluated by the X‐ray diffraction technique. The results showed that TSA induces an appreciable reduction in the fatigue life, especially at lower values of stress amplitude, due to the presence of defects at the interface between the substrate and the anodic film. No correlation was observed between the presence of the anodic layer and the development of a tensile SRS field. Highlights: The effects of TSA anodizing on fatigue properties of AA 7050‐T7451 were studied.An overall reduction of the lifetime at all stress levels was observed due to anodizing.The presence of surface defects strongly affects the HCF behavior of anodized components.No significant influence of anodizing on residual surface stresses was observed. [ABSTRACT FROM AUTHOR]

It has been previously noted that the development of aerospace material technology and breakthroughs are inseparable when obtaining great achievements in the aerospace industry. Materials are the basis and precursor of modern high technology and industry. As one of the most powerful aluminium alloys, 7050 is widely used in the aerospace field. In this manuscript, the vibration fatigue behaviour of aircraft aluminium alloy 7050 is studied based on experiments. A vibration fatigue experiment and the traditional fatigue testing of aluminium alloy 7050 were performed. We found that there was an extreme difference between the vibration fatigue and the traditional fatigue curves. In addition, the experimental end criteria for the vibration fatigue experiment of aluminium alloy 7050 was obtained from the acceleration reduction and the frequency reduction value. For the acceleration experimental end criterion, 2% was the acceleration reduction value for the vibration fatigue experimental end criteria of aluminium alloy 7050. For the frequency experimental end criterion, 2% was the frequency reduction value for the vibration fatigue experimental end criteria of aluminium alloy 7050. [ABSTRACT FROM AUTHOR]

Aluminum alloys were widely used in the construction, automotive, marine, and aviation industries due to their low specific strength, ease of manufacture, and low weight. The fatigue behavior of aluminum alloys at different temperatures is investigated. Thanks to the rapid development of armament in recent years, 7XXX ultra-high strength aluminum alloys are now used more frequently because of their non-corrosive qualities and low weight. Aluminum alloy 7001-T6 behavior is examined at the Company State for Engineering, Rehabilitation, and Inspection (SIER) in Iraq, where chemical analysis of the AA7001 is supported. Most engineering components that operate at high temperatures will eventually fail from fatigue strain, creep damage is a time-dependent process that is primarily influenced by the history of stress and temperature applied to the component. When the two damaging factors combine their effects, This study used AA7001-T6 to conduct experiments on mechanical characteristics (UTS, YS, E, and ductility) and the interaction between creep and fatigue at four distinct temperatures: room temperature (25, 150, 280, and 330) °C, the UTS, YS, and E were lowered by 37.2, 37.2, and 24) %, respectively, as compared to the result at room temperature, but the ductility increased by 28.27 %. It has been noted that rising temperatures cause mechanical and fatigue characteristics to decline. Experimental S-N fatigue test findings showed a significant loss of fatigue strength, After 107 cycles, the endurance fatigue limit was reduced from 208 MPa at (RT) to 184 MPa at 330 °C, an 11.5 % reduction. Overall, it can be said that AA7001-T6 demonstrates a significant drop in mechanical and fatigue properties at high temperatures [ABSTRACT FROM AUTHOR]

There are several constituents that cause die fractures in the die casting process. Several features can be managed to a certain level with the help of specialists like geometry experts, production specialists and engineers. In the die casting procedure, the main loading feature is the fluctuating nature of thermal conditions; therefore, the effect of further forces is comparatively negligible. In order to achieve cost-efficient manufacturing for die casting, different metals' essentiality of die's high operational life is required. Expenditure on die substitution is very high and it increases the manufacturing period. Failure of die can be recognised when fracture line appears on the die surface and it grows during further manufacturing. The main objective of this work is to find out thermal fatigue analysis of aluminium alloy (A02240) dies during the pressure die casting procedure. The location of cooling channels from base is varying (0.5–5 mm). Thus, we get six geometry models for every material. By using ANSYS workbench 17.1, we find three major factors related to this analysis: work temperature distribution, fatigue life and normal stresses generated in dies. [ABSTRACT FROM AUTHOR]

In this paper, a previously developed modification of the Sines model of multiaxial fatigue is reduced to an invariant form. Model constants were determined for different sets of setup experiments. It was supposed to introduce an additional summand to account for the phase shift between loading modes. The model is used to describe the fatigue behavior of the 2024 aluminum alloy. Low-cycle fatigue tests under biaxial loading conditions are presented, with one mode changing cyclically and the other mode remaining constant in magnitude throughout the test. The results of cyclic durability prediction by the modified model provide good convergence. [ABSTRACT FROM AUTHOR]

Fatigue performance is always an important factor affecting the application of aluminum alloys. The service life of the 7B04 aluminum alloy tends to reduce under continuous alternating loads. Therefore, a new method is urgently needed to improve fatigue performance. Laser shock peening (LSP) is a widely proposed method to enhance fatigue performance. It is found that LSP can prolong the fatigue life of 7B04 by improving the surface stress state. During the strengthening process, the residual stress is mainly attributed to the change in microstructure, which the statistical results of grain size can reflect. The microhardness of the treated 7B04 is 22.7% higher than that of the untreated sample. In addition, there is a significant residual compressive stress from the specimen surface to its interior of about 1500 µm after the process of laser shock peening. The fatigue life is extended to 93%, and the ultimate fracture changes macroscopically. The fatigue performance of 7B04 is greatly improved by the LSP treatment. The strengthening mechanism of LSP is established to reveal the relationship between microstructure and stress state to improve the fatigue performance of metal parts of any shape. [ABSTRACT FROM AUTHOR]

• The mapping relationship between sandwich composite structure damping and fatigue performance is explored; • The influence of skin material and composite material on fatigue life is studied; • The influence of damping layer thickness on fatigue performance at ultra-low temperature is studied. The aim is to investigate the influence of aluminum content in the FeCoCrNiAlx series high-entropy alloys, different aluminum alloy damping layers, and the thickness of damping layers on the fatigue performance of sandwich structure composite material plates after room temperature and low-temperature aging treatment. By using abaqus/fe-safe simulation, as well as liquid nitrogen low-temperature aging treatment and fatigue tensile testing, the differences in fatigue performance between composite materials treated with low-temperature aging and those untreated at room temperature were observed. The increase in aluminum content significantly improves the lifespan of the composite materials, and after low-temperature aging treatment, the change in strength is even more pronounced. Keeping the thickness and material of the upper and lower layers constant, the tensile life of the material, both untreated and treated at low temperatures, shows a significant increasing trend as the thickness of the middle damping layer increases. Other conditions being equal, the iMPact of different damping layer aluminum alloys on fatigue performance is also very evident. In terms of tensile cycles, the ranking is as follows: 7075 > 2A12 > 6061. After low-temperature treatment, the fatigue tension cycles of the 2A12, 6061, and 7075 damping layers under a force of 100 N are respectively 8.66, 7.43, and 2.01 times those of the untreated composite materials. [ABSTRACT FROM AUTHOR]

• MFC increased significantly the hardness of aluminum alloys without T6 treatment. • MFC generated compressive residual stress on the surface of aluminum alloys. • MFC improved the fatigue properties of aluminum alloys. • The fatigue strength of MFC-treated aluminum alloys showed same as T6 treated one. • The fatigue strength of MFC-treated aluminum alloys was estimated. The effect of natural aging by multifunction cavitation (MFC) on the fatigue behaviour of heat-treatable Al-Si7Mg aluminum alloys was examined. Surface observation and plane bending fatigue tests were conducted for the MFC-treated aluminum alloys at a stress ratio, R , of −1. The hardness of aluminum alloy without T6 treatment was significantly increased by MFC due to both the work hardening and natural aging. MFC treatment improved the fatigue lives and the fatigue strength at N = 107 cycles of aluminum alloys due to the generation of compressive residual stress and increasing the surface hardness; however, surface pits were large enough to easily nucleate an initial fatigue crack. In addition, the fatigue strength at N = 107 cycles of MFC-treated aluminum alloys can be estimated considering the residual stress, pit size and surface hardness. [ABSTRACT FROM AUTHOR]

This study investigates the influence of corrosion fatigue on the fatigue strength of the aluminium alloy EN AW-6082 T6 with regard to the stress gradient. The experimental design involves varying loading conditions and specimen geometries to facilitate testing under three distinct stress gradients: tension/compression (0 mm-1), rotary bending (0.2 mm-1), notched rotary bending (5.3 mm-1). Reference constant loading tests in air as well as continuously irrigated corrosion fatigue tests in a 5 wt% NaCl-solution are conducted with a constant stress ratio of R = − 1. The results reveal a substantial reduction in fatigue strength due to corrosion fatigue across all three stress gradients. The slope of the S-N curves drops by a factor of at least two and no second slope of the S-N curves is found within the tested load cycle range (up to 107). The study demonstrates a significant increase in the support factor for tests conducted in the corrosive environment. This discrepancy becomes more pronounced towards higher stress gradients and lower load cycle numbers. The application of the support factor derived from tests in a non-corrosive atmosphere is shown to be conservative, emphasizing the significance of accounting for corrosion effects in assessing fatigue behaviour. • Salt corrosion reduces the fatigue strength of EN AW-6082 T6. • No long life fatigue limit due to corrosion fatigue. • Strength reduction depends on the stress gradient. • Support factor increases due to corrosion fatigue. [ABSTRACT FROM AUTHOR]

• Five shot peening treatments with varied shot size and intensity are investigated. • The impact of residual stresses and surface roughness is evaluated. • A fatigue prediction model based on averaged strain energy density is developed. • Shot peening promotes sub-superficial crack initiation. • Low-intensity peening treatments with small shots are more effective. This study addresses the complex interplay of shot peening-induced effects on the fatigue strength of high-strength aluminum alloys. The inherent poor fatigue properties of aluminum alloys, particularly exacerbated in components manufactured through additive processes, pose significant challenges. Shot peening, a recognized surface treatment, proves effective in enhancing fatigue resistance through mechanisms such as compressive residual stresses, work hardening, and microstructural changes. However, optimizing shot peening and developing accurate fatigue prediction models remain challenging due to the intricate and unclear contributions of the individual mechanisms. In this investigation, five distinct shot peening treatments were employed to emphasize specific effects. Experimental results, analyzed through a strain energy density approach, shed light on the crucial role of compressive residual stresses in maximizing fatigue strength. This comprehensive exploration contributes with valuable insights for designing shot peening treatments to optimize the fatigue performance of high-strength aluminum alloys. [ABSTRACT FROM AUTHOR]

In the aviation industry, fretting fatigue represents a significantly hazardous form of fatigue failure, thus warranting substantial research attention. A key area of focus lies in enhancing the fretting fatigue resistance of aluminium alloys. This study investigates the feasibility of using Friction Stir Processing (FSP) to enhance fretting fatigue lifetime. After FSP, large-size inclusions in the Base Material (BM) are shattered, clustered inclusions are dispersed, and the preferred orientation of inclusions is disrupted. Consequently, areas of stress concentration, damage concentration and merging of hazardous zones become less, and the peak values of stress, stress triaxiality, and damage are decreased with 6–10 %. Compared to BM, the results show that the fretting fatigue lifetime of Friction Stir Processed (FSPed) material is increased by 50.1 %. Hence, FSP could emerges as a highly promising surface treatment technique for enhancing fretting fatigue performance. [ABSTRACT FROM AUTHOR]