Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relat...Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relationship between load amplitude,fatigue life,and damage progression in low-carbon steel assemblies.Design/methodology/approach–An experimental approach was adopted using MTS specimens fabricated from St 1203 cold-rolled steel,joined with Grade 8.8 M4 bolts.Cyclic fatigue tests were conducted under zerobased loading at seven distinct force levels.Fracture surfaces were visually analyzed to identify dominant failure mechanisms.Findings–The results revealed a strong inverse correlation between applied cyclic load and fatigue life.Three distinct failure modes were identified:bolt shear at high loads(5.4 kN),interface cracking and slippage at moderate loads(4.9–5.1 kN),and plate tearing or stable fatigue behavior at lower loads(54.1 kN).The results highlight a progressive transition in failure mechanisms,from bolt shear at high loads to plate tearing and interface cracking at lower loads,providing essential insights for fatigue-resistant bolted joint design.Originality/value–This study offers original insights into the fatigue behavior of bolted lap joints using MTS,a relatively underexplored configuration in fatigue assessment.By experimentally evaluating failure modes under varied cyclic load levels,the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load.Unlike many existing studies focused on numerical modeling or bonded joints alone,this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.展开更多
The effects of nanosecond laser shock peening without coating(LSPwC)and nanosecond stacked femtosecond laser shock peening compound strengthening(LSP-CS)on the surface integrity and fretting fatigue lifetime at 500℃o...The effects of nanosecond laser shock peening without coating(LSPwC)and nanosecond stacked femtosecond laser shock peening compound strengthening(LSP-CS)on the surface integrity and fretting fatigue lifetime at 500℃of GH 4169 dovetail component were investigated.The results show that LSP treatment does not significantly lead to changes in the grain size of GH 4169 alloy,but it introduces a large number of dislocations,resulting in the formation of a plastic deformation layer and residual compressive stress layer.The surface microhardness increased by 20.5%and 28.6%after being treated by LSPwC and LSP-CS,respectively.The surface residual compressive stresses were(-306.5±42.5)MPa and(-404.3±34.7)MPa,respectively;The depth of both the hardening layer and the residual compressive stress layer is 400μm,and along the cross-section with 0-100μm region after LSP-CS treatment has higher hardness and greater residual compressive stress.The fretting fatigue lifetime of the GH 4169 dovetail component at 500℃was increased by 346.8%and 494.9%,which is the result of the combined effects of the hardening layer and the residual stress layer.The LSP-CS treatment can effectively make up for the disadvantage of the LSPwC treatment,and further enhance the fretting fatigue lifetime of the GH 4169 dovetail component at high temperature.展开更多
Additive manufactured titanium alloys exhibit distinct microstructures and internal defects compared to forged alloys.This has a significant impact on its fatigue failure behavior and fatigue life distribution.Fatigue...Additive manufactured titanium alloys exhibit distinct microstructures and internal defects compared to forged alloys.This has a significant impact on its fatigue failure behavior and fatigue life distribution.Fatigue life dispersity and distribution characteristics of laser direct energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy were investigated by a relatively large sample fatigue test,fracture morphology characterization,and statistical analytic method.Then,the intrinsic causes of fatigue life dispersity and distribution characteristics were clarified by correlating with fatigue failure origin modes(FFOMs).The test and analysis results indicate that the existence of internal pores significantly influences FFOMs,fatigue life dispersity,and distribution pattern.The FFOMs of microstructure and interior pores have little effect on fatigue life dispersion,In contrast,FFOMs of surface and subsurface pores present a relatively lower fatigue life and are responsible for fatigue life dispersion.Besides,two competitive effects of FFOMs with different applied stress highly affect fatigue life distribution.A bimodal Weibull model is more suitable for describing fatigue life distribution with multiple FFOMs.However,if there is no fast-computing procedure for the parameter estimation of the Bimodal Weibull model,relatively conservative and simple P-S-N curves based on the Weibull distribution model are recommended in engineering applications.展开更多
To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation me...To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation method.This method utilizes a variational autoencoder(VAE)to generate low-cycle fatigue data and form an augmented dataset.The Pearson correlation coefficient(PCC)is employed to verify the similarity of feature distributions between the original and augmented datasets.Six machine learning models,namely random forest(RF),artificial neural network(ANN),support vector machine(SVM),gradient-boosted decision tree(GBDT),eXtreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost),are utilized to predict the LCF life of nickel-based superalloys.Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset,and the mean absolute error(MAE),root mean square error(RMSE),and R-squared(R^(2))values achieved using the CatBoost model,with respective values of 0.0242,0.0391,and 0.9538,are superior to those of the other models.The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.展开更多
Throughout the composite structure’s lifespan,it is subject to a range of environmental factors,including loads,vibrations,and conditions involving heat and humidity.These factors have the potential to compromise the...Throughout the composite structure’s lifespan,it is subject to a range of environmental factors,including loads,vibrations,and conditions involving heat and humidity.These factors have the potential to compromise the integrity of the structure.The estimation of the fatigue life of composite materials is imperative for ensuring the structural integrity of these materials.In this study,a methodology is proposed for predicting the fatigue life of composites that integrates ultrasonic guided waves and machine learning modeling.The method first screens the ultrasonic guided wave signal features that are significantly affected by fatigue damage.Subsequently,a covariance analysis is conducted to reduce the redundancy of the feature matrix.Furthermore,one-hot encoding is employed to incorporate boundary conditions as features,and the resulting data undergoes preprocessing to form a sample library.A composite fatigue life prediction model has been developed,employing the aforementioned sample library as the input source and utilizing remaining life as the output metric.The model synthesizes the strengths of convolutional neural networks(CNNs)and bidirectional long short-term memory networks(BiLSTMs)while leveraging Bayesian optimization(BO)to enhance the optimization of hyperparameters.The experimental results demonstrate that the proposed BO-CNN-BiLSTM model exhibits superior performance in terms of prediction accuracy and reliability in the damage regression task when compared to both the BiLSTM and CNN-BiLSTM models.展开更多
The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF...The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L_(10)life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.展开更多
Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque(more than 100 kN m).A multi-row cam roller bearing(MCRB)is the key ...Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque(more than 100 kN m).A multi-row cam roller bearing(MCRB)is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor.However,compact geometry and complex loads render MCRB susceptible to fatigue failure,highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability.Therefore,this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life.In this method,a quasi-static model was developed to calculate the load distribution,with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution.Subsequently,a genetic algorithm was used to obtain the optimized geometry parameters,which significantly improved the fatigue life of the MCRB.Finally,a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method.This study provides a theoretical guideline for optimizing the design of MCRB,thereby increasing the fatigue life of hydraulic motors.展开更多
In the realm of engineering practice,various factors such as limited availability of measurement data and complex working conditions pose significant challenges to obtaining accurate load spectra.Thus,accurately predi...In the realm of engineering practice,various factors such as limited availability of measurement data and complex working conditions pose significant challenges to obtaining accurate load spectra.Thus,accurately predicting the fatigue life of structures becomes notably arduous.This paper proposed an approach to predict the fatigue life of structure based on the optimized load spectra,which is accurately estimated by an efficient hinging hyperplane neural network(EHH-NN)model.The construction of the EHH-NN model includes initial network generation and parameter optimization.Through the combination of working conditions design,multi-body dynamics analysis and structural static mechanics analysis,the simulated load spectra of the structure are obtained.The simulated load spectra are taken as the input variables for the optimized EHH-NN model,while the measurement load spectra are used as the output variables.The prediction results of case structure indicate that the optimized EHH-NN model can achieve the high-accuracy load spectra,in comparison with support vector machine(SVM),random forest(RF)model and back propagation(BP)neural network.The error rate between the prediction values and the measurement values of the optimized EHH-NN model is 4.61%.In the Cauchy-Lorentz distribution,the absolute error data of 92%with EHH-NN model appear in the intermediate range of±1.65%.Also,the fatigue life analysis is performed for the case structure,based on the accurately predicted load spectra.The fatigue life of the case structure is calculated based on the comparison between the measured and predicted load spectra,with an accuracy of 93.56%.This research proposes the optimized EHH-NN model can more accurately reflect the measurement load spectra,enabling precise calculation of fatigue life.Additionally,the optimized EHH-NN model provides reliability assessment for industrial engineering equipment.展开更多
In order to enhance the fatigue properties of metallic materials,a feasible rationale is to delay or prevent the interior and surface fatigue crack initiation.Based on this rationale,the study investigates the approac...In order to enhance the fatigue properties of metallic materials,a feasible rationale is to delay or prevent the interior and surface fatigue crack initiation.Based on this rationale,the study investigates the approach of improving the very high cycle fatigue properties of TC6 titanium alloys through near-βforging coupled with shot peening,conducted at 930℃and ambient temperature,respectively.To unveil the associated mechanisms,microstructure,microhardness,residual stress,and fatigue properties are thoroughly analyzed after each process.Results indicate a considerable refinement in microstructure and significant mitigation of the initially existed strong texture post near-βforging and annealing,efficiently delaying crack initiation and propagation.As a result,the very high cycle fatigue property of TC6 achieves remarkable enhancement after forging.Compared to near-βforging,shot peening might not necessarily improve the very high cycle fatigue performance,particularly beyond 10^(6)cycles.展开更多
Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of co...Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of contact fatigue failure. This paper assesses the fatigue life of a cycloidal displacement cam and a flat-faced follower under the defined loads and constraints. Computer-aided design (CAD) model of the cam-follower is developed in CATIA software and imported to ANSYS software for finite element analysis (FEA) of fatigue life. MATLAB programming is developed for determining the appropriate spring constant and pre-load force to always keep the cam and follower in contact. The fatigue life of the cam-follower has been estimated under the specified operating conditions. The analysis method can be applied to investigate the fatigue life of cams with other profiles, including the modified trapezoidal functions, polynomial functions, etc.展开更多
The fatigue properties of laser shock processing （LSP） on both side surfaces of fastener hole with diameter of 3 mm in the LY12CZ aluminum alloy specimens were investigated. The superficial residual stress was measu...The fatigue properties of laser shock processing （LSP） on both side surfaces of fastener hole with diameter of 3 mm in the LY12CZ aluminum alloy specimens were investigated. The superficial residual stress was measured by X-ray diffraction method. Fatigue experiments of specimens with and without LSP were performed, and the microstructural features of fracture of specimens were characterized by scanning electron microscopy （SEM）. The results indicate that the compressive residual stress can be induced into the surface of specimen, and the fatigue life of the specimen with LSP is 3.5 times as long as that of specimen without LSP. The location of fatigue crack initiation is transferred from the top surface to the sub-surface after LSP, and the fatigue striation spacing of the treated specimen during the expanding fatigue crack is narrower than that of the untreated specimen. Furthermore, the diameters of the dimples on the fatigue crack rupture zone of the specimen with LSP are relatively bigger, which is related to the serious plastic deformation in the material with LSP.展开更多
The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing ...The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing process of composite laminates, are the common and major reason of causing the random distributions of the static strength and the fatigue life. And there is a correlative relation between the two distributions. With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material, the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained. And then the model which is used to describe the distributions of fatigue life of composites, based on their distributions of static strength, is set up. This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates. The experimental data of three kinds of composite laminates are employed to verify this model, and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.展开更多
In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibu...In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibull distribution ad fatigue strength. First,the contact stress considering elliptical EHL is obtained by mapping film pressure onto the Hertz zone. Then,the basic strength model of rolling bearing based on the 3-parameter Weibull distribution is deduced by the series connection reliability theory. Considering the effect of the type of stress, variation of shape and fuctuation of load, the mathematical models of the 尸 -tS-TV curve of the minimum life and the characteristic life for rolling bearing are established, respectively, and thus the prediction model of fatigue life of rolling bearing based on the 3-paameter Weibull distribution and fatigue strength is further deduced. Finally, the contact fatigue life obtained by the proposed method ad the latest international standard （IS0281： 2007） about the fatigue life prediction of rolling bearing are compared with those obtained by the statistical method. Results show that the proposed prediction method is effective and its relative error is smaier than that of the latest international standard （IS0281： 2007） with reliability R 〉 0. 93.展开更多
In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the ou...In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.展开更多
Ni3Al-based superalloy IC10 is widely used in high temperature components of aeroengines because of its superior mechanical properties.In this paper,the creep feed grinding properties of IC10 were investigated experim...Ni3Al-based superalloy IC10 is widely used in high temperature components of aeroengines because of its superior mechanical properties.In this paper,the creep feed grinding properties of IC10 were investigated experimentally.The effects of grinding parameters on the grinding forces and temperature were examined.Moreover,the influences of surface roughness and hardening on the high-cycle fatigue life of IC10 specimens were studied.To control the creep feed grinding parameters and enhance the fatigue life of IC10 components,the experimental results were summarized to offer a useful reference point.It is concluded that,the grinding depth is the most important factor which influencing the grinding forces and temperature;the surface roughness is the main and unfavorable factor on the fatigue life of IC10,while the surface hardening has a positive influence on the fatigue life;to obtain a better surface quality and improve the fatigue life of IC 10,the recommended grinding parameter domain involves wheel speed 2[15,20]m/s,feed rate∈[150,200]mm/min,and grinding depth∈[0.4,0.5]mm.展开更多
To predict the fatigue life for oblique hyperbola-and bilinear-mode S-N curves of metallic materials with various strengths,a machine-learning approach for direct analysis was employed.Additionally,to determine the fa...To predict the fatigue life for oblique hyperbola-and bilinear-mode S-N curves of metallic materials with various strengths,a machine-learning approach for direct analysis was employed.Additionally,to determine the fatigue limit of the utilized materials(AISI 316,AISI 4140 and CA6 NM series)with different S-N curve modes using finite-fatigue life data,a Bayesian optimization-based inverse analysis was performed.The results indicated that predictions of the fatigue life for the utilized datasets via the random forest(RF)algo rithm for AISI 4140 and CA6 NM,and artificial neural network(ANN)for AISI 316,distribute within 2 factor error lines for most data.In the Bayesian optimization-based inverse analysis,the specific explanatory variables corresponding to the optimized maximum fatigue life were treated as the fatigue limits.The predicted fatigue limits either approximated to or slightly underestimated the experimental results,except for several cases with large errors.Using the inverse analysis to predict the fatigue limit for both S-N curve modes is applicable for current employed data-set.However,the explored maximum fatigue lives via BO corresponding to the predicted fatigue limit were underestimated for AISI 4140 and CA6 NM,and was overestimated for AISI 316 because of effect of shape of S-N curves.By combining the ANN or RF direct and BO inverse algorithms,whole S-N curves(including the fatigue limit)were evaluated for the S-N curve shapes of the oblique hyperbola and bilinear modes.展开更多
The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of ...The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn.展开更多
In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this pap...In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.展开更多
In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in ...In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area （FGA） centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.展开更多
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
文摘Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relationship between load amplitude,fatigue life,and damage progression in low-carbon steel assemblies.Design/methodology/approach–An experimental approach was adopted using MTS specimens fabricated from St 1203 cold-rolled steel,joined with Grade 8.8 M4 bolts.Cyclic fatigue tests were conducted under zerobased loading at seven distinct force levels.Fracture surfaces were visually analyzed to identify dominant failure mechanisms.Findings–The results revealed a strong inverse correlation between applied cyclic load and fatigue life.Three distinct failure modes were identified:bolt shear at high loads(5.4 kN),interface cracking and slippage at moderate loads(4.9–5.1 kN),and plate tearing or stable fatigue behavior at lower loads(54.1 kN).The results highlight a progressive transition in failure mechanisms,from bolt shear at high loads to plate tearing and interface cracking at lower loads,providing essential insights for fatigue-resistant bolted joint design.Originality/value–This study offers original insights into the fatigue behavior of bolted lap joints using MTS,a relatively underexplored configuration in fatigue assessment.By experimentally evaluating failure modes under varied cyclic load levels,the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load.Unlike many existing studies focused on numerical modeling or bonded joints alone,this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.
基金Project(2022YFB3401900)supported by the the National Key R&D of ChinaProject(2025YFHZ0163)supported by the the Science and Technology Projects in Sichuan Province,ChinaProject(2682024GF004)supported by Fundamental Research Funds for the Centeral University,China。
文摘The effects of nanosecond laser shock peening without coating(LSPwC)and nanosecond stacked femtosecond laser shock peening compound strengthening(LSP-CS)on the surface integrity and fretting fatigue lifetime at 500℃of GH 4169 dovetail component were investigated.The results show that LSP treatment does not significantly lead to changes in the grain size of GH 4169 alloy,but it introduces a large number of dislocations,resulting in the formation of a plastic deformation layer and residual compressive stress layer.The surface microhardness increased by 20.5%and 28.6%after being treated by LSPwC and LSP-CS,respectively.The surface residual compressive stresses were(-306.5±42.5)MPa and(-404.3±34.7)MPa,respectively;The depth of both the hardening layer and the residual compressive stress layer is 400μm,and along the cross-section with 0-100μm region after LSP-CS treatment has higher hardness and greater residual compressive stress.The fretting fatigue lifetime of the GH 4169 dovetail component at 500℃was increased by 346.8%and 494.9%,which is the result of the combined effects of the hardening layer and the residual stress layer.The LSP-CS treatment can effectively make up for the disadvantage of the LSPwC treatment,and further enhance the fretting fatigue lifetime of the GH 4169 dovetail component at high temperature.
基金supported by the National Natural Science Foundation of China(Nos.51775018&52090044)。
文摘Additive manufactured titanium alloys exhibit distinct microstructures and internal defects compared to forged alloys.This has a significant impact on its fatigue failure behavior and fatigue life distribution.Fatigue life dispersity and distribution characteristics of laser direct energy deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy were investigated by a relatively large sample fatigue test,fracture morphology characterization,and statistical analytic method.Then,the intrinsic causes of fatigue life dispersity and distribution characteristics were clarified by correlating with fatigue failure origin modes(FFOMs).The test and analysis results indicate that the existence of internal pores significantly influences FFOMs,fatigue life dispersity,and distribution pattern.The FFOMs of microstructure and interior pores have little effect on fatigue life dispersion,In contrast,FFOMs of surface and subsurface pores present a relatively lower fatigue life and are responsible for fatigue life dispersion.Besides,two competitive effects of FFOMs with different applied stress highly affect fatigue life distribution.A bimodal Weibull model is more suitable for describing fatigue life distribution with multiple FFOMs.However,if there is no fast-computing procedure for the parameter estimation of the Bimodal Weibull model,relatively conservative and simple P-S-N curves based on the Weibull distribution model are recommended in engineering applications.
基金Financial support from the Fundamental Research Funds for the Central Universities(ZJ2022-003,JG2022-27,J2020-060,and J2021-060)Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance(GAMRC2021YB08)the Young Scientists Fund of the National Natural Science Foundation of China(No.52105417)is acknowledged.
文摘To overcome the challenges of limited experimental data and improve the accuracy of empirical formulas,we propose a low-cycle fatigue(LCF)life prediction model for nickel-based superalloys using a data augmentation method.This method utilizes a variational autoencoder(VAE)to generate low-cycle fatigue data and form an augmented dataset.The Pearson correlation coefficient(PCC)is employed to verify the similarity of feature distributions between the original and augmented datasets.Six machine learning models,namely random forest(RF),artificial neural network(ANN),support vector machine(SVM),gradient-boosted decision tree(GBDT),eXtreme Gradient Boosting(XGBoost),and Categorical Boosting(CatBoost),are utilized to predict the LCF life of nickel-based superalloys.Results indicate that the proposed data augmentation method based on VAE can effectively expand the dataset,and the mean absolute error(MAE),root mean square error(RMSE),and R-squared(R^(2))values achieved using the CatBoost model,with respective values of 0.0242,0.0391,and 0.9538,are superior to those of the other models.The proposed method reduces the cost and time associated with LCF experiments and accurately establishes the relationship between fatigue characteristics and LCF life of nickel-based superalloys.
基金funded by the Key Technologies R&D Program of CNBM(2023SJYL01)Postgraduate Research&Practice Innovation Program of Jiangsu Province(SJCX24_1356).
文摘Throughout the composite structure’s lifespan,it is subject to a range of environmental factors,including loads,vibrations,and conditions involving heat and humidity.These factors have the potential to compromise the integrity of the structure.The estimation of the fatigue life of composite materials is imperative for ensuring the structural integrity of these materials.In this study,a methodology is proposed for predicting the fatigue life of composites that integrates ultrasonic guided waves and machine learning modeling.The method first screens the ultrasonic guided wave signal features that are significantly affected by fatigue damage.Subsequently,a covariance analysis is conducted to reduce the redundancy of the feature matrix.Furthermore,one-hot encoding is employed to incorporate boundary conditions as features,and the resulting data undergoes preprocessing to form a sample library.A composite fatigue life prediction model has been developed,employing the aforementioned sample library as the input source and utilizing remaining life as the output metric.The model synthesizes the strengths of convolutional neural networks(CNNs)and bidirectional long short-term memory networks(BiLSTMs)while leveraging Bayesian optimization(BO)to enhance the optimization of hyperparameters.The experimental results demonstrate that the proposed BO-CNN-BiLSTM model exhibits superior performance in terms of prediction accuracy and reliability in the damage regression task when compared to both the BiLSTM and CNN-BiLSTM models.
基金supported by the National Natural Science Foun-dation(Grant No.52031013)the National Key Research and Development Program(Grant No.2018YFA0702900).
文摘The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L_(10)life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.
基金Supported by National Key R&D Program of China(Grant No.2021YFB3400501).
文摘Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque(more than 100 kN m).A multi-row cam roller bearing(MCRB)is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor.However,compact geometry and complex loads render MCRB susceptible to fatigue failure,highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability.Therefore,this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life.In this method,a quasi-static model was developed to calculate the load distribution,with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution.Subsequently,a genetic algorithm was used to obtain the optimized geometry parameters,which significantly improved the fatigue life of the MCRB.Finally,a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method.This study provides a theoretical guideline for optimizing the design of MCRB,thereby increasing the fatigue life of hydraulic motors.
基金Supported by National Natural Science Foundation of China(Grant No.51805447)Natural Science Foundation of Jiangsu Higher Education of China(Grant No.22KJB460010)+2 种基金Jiangsu Provincial Innovation and Promotion Project of Forestry Science and Technology of China(Grant No.LYKJ[2023]06)Yangzhou Science and Technology Plan(City School Cooperation Project)of China(Grant No.YZ2022193)Cyan Blue Project of Yangzhou University of China。
文摘In the realm of engineering practice,various factors such as limited availability of measurement data and complex working conditions pose significant challenges to obtaining accurate load spectra.Thus,accurately predicting the fatigue life of structures becomes notably arduous.This paper proposed an approach to predict the fatigue life of structure based on the optimized load spectra,which is accurately estimated by an efficient hinging hyperplane neural network(EHH-NN)model.The construction of the EHH-NN model includes initial network generation and parameter optimization.Through the combination of working conditions design,multi-body dynamics analysis and structural static mechanics analysis,the simulated load spectra of the structure are obtained.The simulated load spectra are taken as the input variables for the optimized EHH-NN model,while the measurement load spectra are used as the output variables.The prediction results of case structure indicate that the optimized EHH-NN model can achieve the high-accuracy load spectra,in comparison with support vector machine(SVM),random forest(RF)model and back propagation(BP)neural network.The error rate between the prediction values and the measurement values of the optimized EHH-NN model is 4.61%.In the Cauchy-Lorentz distribution,the absolute error data of 92%with EHH-NN model appear in the intermediate range of±1.65%.Also,the fatigue life analysis is performed for the case structure,based on the accurately predicted load spectra.The fatigue life of the case structure is calculated based on the comparison between the measured and predicted load spectra,with an accuracy of 93.56%.This research proposes the optimized EHH-NN model can more accurately reflect the measurement load spectra,enabling precise calculation of fatigue life.Additionally,the optimized EHH-NN model provides reliability assessment for industrial engineering equipment.
基金financial support from the National Science and Technology Major Project(Grant No.J2019-IV-0010-0078)the National Natural Science Foundation of China(Grant Nos.12172139 and 11972012)funding from the Fundamental Research Funds for the Central Universities(Grant No.2019kfyXJJS141).
文摘In order to enhance the fatigue properties of metallic materials,a feasible rationale is to delay or prevent the interior and surface fatigue crack initiation.Based on this rationale,the study investigates the approach of improving the very high cycle fatigue properties of TC6 titanium alloys through near-βforging coupled with shot peening,conducted at 930℃and ambient temperature,respectively.To unveil the associated mechanisms,microstructure,microhardness,residual stress,and fatigue properties are thoroughly analyzed after each process.Results indicate a considerable refinement in microstructure and significant mitigation of the initially existed strong texture post near-βforging and annealing,efficiently delaying crack initiation and propagation.As a result,the very high cycle fatigue property of TC6 achieves remarkable enhancement after forging.Compared to near-βforging,shot peening might not necessarily improve the very high cycle fatigue performance,particularly beyond 10^(6)cycles.
文摘Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of contact fatigue failure. This paper assesses the fatigue life of a cycloidal displacement cam and a flat-faced follower under the defined loads and constraints. Computer-aided design (CAD) model of the cam-follower is developed in CATIA software and imported to ANSYS software for finite element analysis (FEA) of fatigue life. MATLAB programming is developed for determining the appropriate spring constant and pre-load force to always keep the cam and follower in contact. The fatigue life of the cam-follower has been estimated under the specified operating conditions. The analysis method can be applied to investigate the fatigue life of cams with other profiles, including the modified trapezoidal functions, polynomial functions, etc.
基金Project (51175002) supported by the National Natural Science Foundation of ChinaProject (090414156) supported by the Natural Science Foundation of Anhui Province,China
文摘The fatigue properties of laser shock processing （LSP） on both side surfaces of fastener hole with diameter of 3 mm in the LY12CZ aluminum alloy specimens were investigated. The superficial residual stress was measured by X-ray diffraction method. Fatigue experiments of specimens with and without LSP were performed, and the microstructural features of fracture of specimens were characterized by scanning electron microscopy （SEM）. The results indicate that the compressive residual stress can be induced into the surface of specimen, and the fatigue life of the specimen with LSP is 3.5 times as long as that of specimen without LSP. The location of fatigue crack initiation is transferred from the top surface to the sub-surface after LSP, and the fatigue striation spacing of the treated specimen during the expanding fatigue crack is narrower than that of the untreated specimen. Furthermore, the diameters of the dimples on the fatigue crack rupture zone of the specimen with LSP are relatively bigger, which is related to the serious plastic deformation in the material with LSP.
文摘The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing process of composite laminates, are the common and major reason of causing the random distributions of the static strength and the fatigue life. And there is a correlative relation between the two distributions. With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material, the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained. And then the model which is used to describe the distributions of fatigue life of composites, based on their distributions of static strength, is set up. This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates. The experimental data of three kinds of composite laminates are employed to verify this model, and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.
基金The National Defense Advance Research Program(No.81302XXX)
文摘In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibull distribution ad fatigue strength. First,the contact stress considering elliptical EHL is obtained by mapping film pressure onto the Hertz zone. Then,the basic strength model of rolling bearing based on the 3-parameter Weibull distribution is deduced by the series connection reliability theory. Considering the effect of the type of stress, variation of shape and fuctuation of load, the mathematical models of the 尸 -tS-TV curve of the minimum life and the characteristic life for rolling bearing are established, respectively, and thus the prediction model of fatigue life of rolling bearing based on the 3-paameter Weibull distribution and fatigue strength is further deduced. Finally, the contact fatigue life obtained by the proposed method ad the latest international standard （IS0281： 2007） about the fatigue life prediction of rolling bearing are compared with those obtained by the statistical method. Results show that the proposed prediction method is effective and its relative error is smaier than that of the latest international standard （IS0281： 2007） with reliability R 〉 0. 93.
文摘In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.
基金supported by NSAF(No.U1830122)the National Natural Science Foundation of China(No.51775443)。
文摘Ni3Al-based superalloy IC10 is widely used in high temperature components of aeroengines because of its superior mechanical properties.In this paper,the creep feed grinding properties of IC10 were investigated experimentally.The effects of grinding parameters on the grinding forces and temperature were examined.Moreover,the influences of surface roughness and hardening on the high-cycle fatigue life of IC10 specimens were studied.To control the creep feed grinding parameters and enhance the fatigue life of IC10 components,the experimental results were summarized to offer a useful reference point.It is concluded that,the grinding depth is the most important factor which influencing the grinding forces and temperature;the surface roughness is the main and unfavorable factor on the fatigue life of IC10,while the surface hardening has a positive influence on the fatigue life;to obtain a better surface quality and improve the fatigue life of IC 10,the recommended grinding parameter domain involves wheel speed 2[15,20]m/s,feed rate∈[150,200]mm/min,and grinding depth∈[0.4,0.5]mm.
文摘To predict the fatigue life for oblique hyperbola-and bilinear-mode S-N curves of metallic materials with various strengths,a machine-learning approach for direct analysis was employed.Additionally,to determine the fatigue limit of the utilized materials(AISI 316,AISI 4140 and CA6 NM series)with different S-N curve modes using finite-fatigue life data,a Bayesian optimization-based inverse analysis was performed.The results indicated that predictions of the fatigue life for the utilized datasets via the random forest(RF)algo rithm for AISI 4140 and CA6 NM,and artificial neural network(ANN)for AISI 316,distribute within 2 factor error lines for most data.In the Bayesian optimization-based inverse analysis,the specific explanatory variables corresponding to the optimized maximum fatigue life were treated as the fatigue limits.The predicted fatigue limits either approximated to or slightly underestimated the experimental results,except for several cases with large errors.Using the inverse analysis to predict the fatigue limit for both S-N curve modes is applicable for current employed data-set.However,the explored maximum fatigue lives via BO corresponding to the predicted fatigue limit were underestimated for AISI 4140 and CA6 NM,and was overestimated for AISI 316 because of effect of shape of S-N curves.By combining the ANN or RF direct and BO inverse algorithms,whole S-N curves(including the fatigue limit)were evaluated for the S-N curve shapes of the oblique hyperbola and bilinear modes.
基金supported by the High Technology Research and Development Program of China (863 Program,Grant Nos.2006AA09Z356 and 2007AA09Z313)
文摘The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn.
基金Supported by the NSF of China(69971016) Supported by the Shanghai Higher Learning Science Supported by the Technology Development Foundation(00JC14507)
文摘In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.
基金supported by the National Basic Research Program of China (Grant 2012CB937500)the National Natural Science Foundations of China (Grants 11172304 and 11202210)
文摘In this paper, ultrasonic （20 kHz） fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue （VHCF） regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area （FGA） centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.
