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ABSTRACT The brake control box beneath an EMU is exposed to dynamic and fluctuating load cases, increasing its susceptibility to vibration fatigue failure. A novel lightweight design approach was implemented to integrate structural and material optimizations. Static and fatigue tests of the T700/5429 CFRP were carried out to augment the stress analysis and predictions of the vibration fatigue life. The local stresses perpendicular and parallel to the welds were obtained to calculate the stress ratio, stress range, and allowable stress value corresponding to the stress component. The fatigue strength of the aluminum box was estimated on the basis of multiaxial criteria, and the fatigue life of the two boxes was predicted with Dirlik's theory. These computational findings unequivocally indicated a noteworthy reduction in damage to the composite box subsequent to lightweight modification, thereby successfully satisfying both the stiffness and strength criteria essential for the safety and reliability of the EMU. [ABSTRACT FROM AUTHOR]

This paper proposes a novel framework for the random vibration fatigue assessment of thin‐walled plate with multiple holes based on the fatigue damage response spectrum method. Compared with other frequency‐domain evaluation methods, this framework fully exploits the dynamic characteristics of complex structures, decoupling the external excitation characteristics from the spatial characteristics of the structural response. This approach significantly enhances evaluation efficiency by avoiding the complex calculations associated with stress response spectral moments. The proposed method is employed to evaluate the contribution of each mode to the overall damage, additionally, the stress mode shapes are used to identify and refine the mesh around fatigue hotspots. Modal damage contribution factors are proposed to identify the key modes. By leveraging both structural dimension reduction and modal reduction techniques, the proposed framework can swiftly and accurately locate fatigue hotspots within complex structures and conduct precise fatigue assessments using the Absolute Sum ‐ Square Root of the Sum of Squares hybrid method. Finite element simulation analysis is conducted on a single‐lap structure containing numerous circular openings, validating the accuracy and efficiency of the proposed stochastic vibration fatigue assessment. Highlights: A framework for assessing random vibration fatigue of thin‐walled plate with localized featuresEmploy stress modes to pinpoint the locations of critical fatigue holesUtilize modal damage contribution factors to identify key modesImplement damage combination considering the identified key modes [ABSTRACT FROM AUTHOR]

To investigate the local damage characteristics and properties of stiffness degradation in aluminum structures under vibration fatigue, an evaluation method of the fatigue property for local areas has been proposed by identifying the stiffness from the phase velocity obtained by the laser ultrasonic system. First, vibration fatigue tests were conducted on 2024‐O aluminum alloy components under four different stress levels. To address the issue of local damage characteristics under vibration fatigue, a scan window to achieve the local phase velocities within a small local region was employed, and then, the local stiffness can be calculated. By tracking the residual stiffness of the weakest region, the local damage factor was calculated. A unified model with normalized periods at different stress levels was carried out to predict the evolutionary trend. This approach offers a more efficient alternative to estimate local fatigue damage and residual life through the monitoring of local stiffness during maintenance. Highlights: A method for quantifying local damage induced by vibration fatigue is proposed.Local stiffness obtained from the phase velocity acquired by the laser ultrasonic system is used for fatigue assessment.The focus on the most vulnerable area is achieved using a local damage factor.The fatigue life of the specimen is predicted by a normalized model under different stress levels. [ABSTRACT FROM AUTHOR]

This paper proposes a novel vibration fatigue testing methodology of thin-walled specimens in the very high cycle fatigue (VHCF) regime, with the lifetime up to 109 cycles. A series of novel thin-walled specimens for the single crystal superalloy DD6 are designed, considering the thickness range from 0.5 to 1.5 mm. And the influences of the wall thickness on the S–N relations are obtained at RT and 760 °C, respectively. Subsequently, the thickness debit effect of the superalloy in terms of VHCF is presented and the relevant mechanism is discussed finally. The results show the proposed fatigue testing methodology is feasible and efficient for the thin-walled specimens. It is revealed the thickness debit effect of the superalloy at 760 °C, which shows the fatigue strengths of the 0.5 mm specimens are remarkably lower than those of other thicker specimens, especially in the VHCF regime. The thickness debit effect is mainly attributed to the fatigue crack initiation assisted by oxide penetration.

Purpose – This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie. Design/methodology/approach – Vibration fatigue of railway bogie arising from the wheel/rail high frequency vibration has become the main concern of railway operators. Previous reviews usually focused on the formation mechanism of wheel/rail high frequency vibration. This paper thus gives a critical review of the vibration fatigue of railway bogie owing to the short-pitch irregularities-induced high frequency vibration, including a brief introduction of short-pitch irregularities, associated high frequency vibration in railway bogie, typical vibration fatigue failure cases of railway bogie and methodologies used for the assessment of vibration fatigue and research gaps. Findings – The results showed that the resulting excitation frequencies of short-pitch irregularity vary substantially due to different track types and formation mechanisms. The axle box-mounted components are much more vulnerable to vibration fatigue compared with other components. The wheel polygonal wear and rail corrugation-induced high frequency vibration is the main driving force of fatigue failure, and the fatigue crack usually initiates from the defect of the weld seam. Vibration spectrum for attachments of railway bogie defined in the standard underestimates the vibration level arising from the short-pitch irregularities. The current investigations on vibration fatigue mainly focus on the methods to improve the accuracy of fatigue damage assessment, and a systematical design method for vibration fatigue remains a huge gap to improve the survival probability when the rail vehicle is subjected to vibration fatigue. Originality/value – The research can facilitate the development of a new methodology to improve the fatigue life of railway vehicles when subjected to wheel/rail high frequency vibration.

This paper proposes a novel method based on continuum damage mechanics (CDM) and machine learning (ML) models to evaluate the vibration fatigue behavior of W1‐type railway fastener clips subjected to high‐frequency vibration. Firstly, static and fatigue tests are conducted on 60Si2Mn spring steel to acquire elastic modulus, tensile strength, and P‐S‐N curves. Subsequently, a CDM model is established, and numerical simulations are performed under various working conditions to obtain the fatigue characteristics of the clips. Finally, the ML model is trained using numerical simulation results, thereby establishing a mapping model between the working conditions and fatigue characteristics. The developed ML model demonstrates high accuracy in predicting the vibration fatigue life of the clips. Moreover, the Shapley Additive Explanations (SHAP) algorithm is employed to elucidate the ML model, revealing that the vibration frequency has a greater impact on the fatigue life of the clips compared to the vibration displacement. Highlights: A novel approach is developed for vibration fatigue assessment of fastener clip.The approach effectively combines the continuum damage model and ML (ANN) model.Static and fatigue tests of 60Si2Mn spring steel are conducted.Fatigue characteristic of clips subjected to high‐frequency vibration is studied. [ABSTRACT FROM AUTHOR]

Vibration fatigue is a typical form of multiaxial fatigue. In this study, initial vibration fatigue tests were conducted on rocket turbine blades, and significant dispersion in fatigue life was found. Consistent with this finding, a novel probabilistic life prediction framework was proposed. This framework integrates sensitivity analysis and sequential sampling technology and introduces polynomial chaos expansion as a computationally efficient alternative to finite element analysis. And a continuous mechanics‐based damage evolution model was employed to examine the vibration fatigue life of turbine blades. The findings validate the effectiveness of the framework, as no significant difference was found between the experimental results and simulated predictions at the 95% confidence level. Furthermore, comparison with the Monte Carlo simulation indicated that this framework achieves comparable prediction accuracy, while significantly reducing the required samples by 2 orders of magnitude, which effectively addresses the fatigue problem of small sample data. This framework enables rapid and accurate multiaxial fatigue probabilistic life prediction, which holds important implications for the reliability design of reusable spacecraft. Highlights: This study is a novel probabilistic framework for predicting fatigue life of small sample data.The polynomial chaos expansion (PCE)‐based framework achieves the Monte Carlo simulation (MCS)‐level accuracy with less than 1% samples.The vibration fatigue tests have verified the effectiveness of proposed method. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to reduce the overall mass of the product, an improved variant of the engine oil suction pipe in hybrid design is developed and analysed as part of this paper. The vibration fatigue analysis of a simple all-metal suction pipe and the new hybrid suction pipe variant is derived using computer FEA simulations and vibration measurements on the shaker. The hybrid design of the technical components makes it possible to combine different types of materials in order to achieve the best possible properties and behaviours for the components under the influence of external loads. In our case, we combine a suction pipe made of S235JR mild steel with a 3D-printed polyamide intake funnel featuring a grid designed to prevent particles from entering the engine's lubrication circuit. This design reduces the mass and shifts the centre of gravity closer to the attachment point of the pipe, as well as to the engine crankcase, which has a positive effect on the values of natural frequencies and vibration amplitudes. The main objective of such a hybrid suction pipe is precisely to reduce vibrations, and thus extend the service life of the components. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the fatigue state estimation of the metro bogie frame is discussed based on limited sensors through frequency domain methods. The middle-frequency and high-frequency vibration fatigue damage cases of one metro bogie frame is discussed. The main excitations come from the wheel/rail interactions including wheel out-of-roundness and rail irregularities. The most common modal vibration of the bogie frame, where the transom bending deformation is dominant, is taken as the research object to study the possibilities of fatigue failure monitoring on concerned points of the bogie frame transom focusing on specific transfer paths. To eliminate unnecessary input signals which are not closely related to the occurrence of large stress amplitudes, the coherence analysis of different loads including the transmission load, carbody load and wheel-rail impact load is conducted through various methods including the short-time Fourier transform spectrum analysis, the magnitude-squared coherence analysis and the partial directed coherence analysis. Then the power spectral densities (PSDs) of the measured accelerations and cross power spectral densities (CPSDs) are calculated to obtain the transfer functions, whose output is the Y -axis stress at the concerned point. The stress PSDs are obtained using the instantly measured input accelerations and the prepared transfer function. Then the spectral moments and the stress amplitudes distribution functions are calculated through the frequency domain method to overcome the computational burden. The stress reconstructions based on inverse fast Fourier transform are analyzed and the fatigue damage results show good consistency with the experimental ones. [ABSTRACT FROM AUTHOR]

In order to further investigate dynamic characteristics of turbine runner blades under the coupling effect of vibration and crack, in this article, a runner blade with a crack was taken as the research object. The coupling effect of vibration and crack was analyzed, a nonlinear dynamic model considering the coupling of the runner blade was developed, and the vibration and fatigue characteristics were investigated. First, based on the contact characteristics of the breathing crack surfaces in the runner blade under hydraulic excitation, a breathing crack surface contact model was established. Subsequently, a nonlinear dynamic model considering the coupling effect of vibration and crack was obtained. The crack surface contact force and crack stiffness matrix were established and the vibration and fatigue characteristics were analyzed. Finally, the feasibility of the dynamic model was verified by a case study, and the dynamic and vibration fatigue characteristics under the coupling effect of vibration and crack were revealed. The research results show that with propagation of the crack, the crack surface contact force increases and the dynamic stress amplitude at the crack tip increases as well. When the sum of the frequency of the hydraulic excitation and the crack surface contact force acting on the runner blade is close to the natural frequency of the runner blade, a combined resonance will occur. When the coupling effect of vibration and crack is taken into consideration, the vibration fatigue crack propagation model is more accurate and can provide a basis for fatigue strength and life prediction of runner blades. [ABSTRACT FROM AUTHOR]

2.5D woven composite has great application prospect in high bypass ratio commercial turbofan engine fan blades due to its comprehensive advantages in mechanical properties and complex component forming. For the aero-engine fan blades, vibration fatigue is a working condition that can not be ignored. At present, the research on vibration fatigue behavior of 2.5D woven composite is limited, and there is a lack of numerical model for vibration fatigue behavior simulation. In this paper, a multi-scale model for the first-order flexural vibration fatigue behavior of a 2.5D woven composite cantilever beam simulating the root of engine blade was established. Adopting the fatigue loading simulation method which adopted the fixed cycle jumping strategy, and the damage initiation criterion and fatigue stiffness degradation model based on the leading fatigue failure mechanism, the vibration fatigue test processes of the wrap and weft specimens were simulated respectively. With the established multi-scale model, the stress field in the unit cell of the dangerous part of the specimen was analyzed, and the damage state of the specimen after the vibration fatigue test was predicted. The numerical simulation results are consistent with the observed fracture morphology after the test, which verifies the validity of the proposed multi-scale prediction model for vibration fatigue of 2.5D woven composite materials. In addition, based on the multi-scale prediction model of vibration fatigue proposed in this paper, the damage states in the unit cell at the working section of the wrap specimen with the accumulation of fatigue loading cycles simulated, which is helpful to understand the evolutionary mechanism of vibration fatigue damage of 2.5D woven composite materials.

This paper aims to develop an innovative multiaxial fatigue criterion based on the stress invariant, in order to perform the fatigue damage analysis of engineering structures subjected to random vibrations. First, the change rule of structural vibration fatigue lifetime under different load correlation conditions is systemically studied by experiments. Then, the finite element analysis of such a structure, including the modal analysis and the spectral analysis, is implemented in order to compute the response stress power spectral density (PSD) functions at the critical fatigue‐prone location under coupled random acceleration base excitations. Finally, the influence rule of load correlation on the vibration fatigue damage of such a symmetrical structure is theoretically illustrated through formula derivation. Moreover, combined with the critical distance theory point method, the proposed time/frequency‐domain multiaxial fatigue criterion is applied for vibration fatigue lifetime evaluation of the structure. The lifetime prediction accuracy of the proposed multiaxial fatigue criterion is verified by comparing with the vibration fatigue test results. Highlights: A novel time‐domain multiaxial vibration fatigue analysis method is developed.A novel frequency‐domain multiaxial vibration fatigue analysis method is developed.Influence of load correlation on vibration fatigue damage is investigated.Validity of proposed method is confirmed by fatigue life prediction result. [ABSTRACT FROM AUTHOR]

Rail corrugation can cause the vibration fatigue failure of the bogie, especially in the metro vehicle. Whereas the existing maintenance limit of rail corrugation is mainly based on operating safety and wheel-rail noise emission and neglects the vibration fatigue failure problems arising from the rail corrugation. It is thus desirable to develop a maintenance limit for rail corrugation from the vibration fatigue failure point of view. Considering that the axle box acceleration spectrum defined in IEC 61373 serves as a basic input for the evaluation of the vibration fatigue life of the bogie, the axle box acceleration thus can be taken as a basic boundary condition for the high-frequency vibration of wheel-rail. This paper thus developed a methodology to determine the maintenance limit based on the axle box acceleration spectrum and the transfer function of the wheel-rail system. In this method, the transfer function was identified by the measured rail corrugation and axle box acceleration. Subsequently, the maintenance limit was derived by the axle box acceleration spectrum defined in IEC 61373 together with the transfer function. The newly developed maintenance limit is considered more reliable to suppress the vibration fatigue failure of the bogie arising from the rail corrugation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a novel mechanical environmental test method that multi-output random strain responses are replicated instead of acceleration responses. In this work, the positive-definite strain reference spectral matrix and reference kurtoses for multiple control channels are defined first, and then three types of strain random signals including stationary Gaussian, stationary non-Gaussian, and non-stationary are generated. The inverse Fourier transform is used to obtain the stationary Gaussian strain random signals and the stationary non-Gaussian strain signals are obtained by the zero-memory nonlinear transformation. To synthetize non-stationary strain random signals, an amplitude modulation function is introduced with time-varying root mean square values. The correction algorithms are employed to update the drive signals for matching the strain responses compared with corresponding reference values. The simulation and experimental results prove the effectiveness and feasibility of the proposed strain response control procedure. The presented work provides new perspectives to investigate the fatigue behavior and life estimation of structure under controlled strain response environments for vibration fatigue tests. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Three-dimensional braided Cf/Al composites prepared by vacuum pressure infiltration method have good mechanical properties and great potential in aerospace applications. In this paper, the three-dimensional braided Cf/Al composites were taken as the research object, and the vibration fatigue tests were carried out under different loading stresses, and the microstructure of the fracture was observed after the fatigue tests. The test results show that the greater the loading stress is, the greater the percentage of natural frequency decrease is when T-shaped part reaches reach the fatigue stability stage, that is, the more significant the damage to the internal structure of T-shaped part is. By fitting the fatigue data under different loading stresses and drawing the S-N curve, the mathematical model of vibration fatigue damage evolution law of T-shaped part is obtained, which can be used to predict the life of three-dimensional braided Cf/Al composites. It is found that T-shaped part after the experiment shows typical brittle fracture characteristics through the macroscopic and microscopic analysis of the fracture .

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Laser additively manufactured (LAM) Ti-6Al-4V alloy has huge application potential in aerospace structural parts such as turbine blades. However, there are few studies on the fatigue properties of such LAM parts under vibration loading, particularly with regard to anisotropy. In this paper, vibration fatigue properties of LAM Ti-6Al-4V by laser melted deposition were investigated along the transversely deposited (TD) and parallelly deposited (PD) directions. Through the first-order bending vibration experiments, the LAM Ti-6Al-4V alloy exhibits obvious anisotropic fatigue properties and significant dispersion in fracture position. The fracture morphology analysis reveals that the vibration fatigue failure was mainly dominated by process-induced defects and microstructure. The fatigue strength at 106 cycles of the samples with defect-free failure features (DFF) at initiation sites is 470.9 MPa in PD and 434.2 Mpa in TD, while that of the samples with defect-related failure features (DRF) at initiation sites is 364.2 Mpa in PD and 381.0 Mpa in TD. For the DFF group, the fatigue behavior is controlled by the prior β columnar grains with preferential orientation, which leads to enhanced fatigue crack propagation resistance for the PD samples. For the DRF group, which has lower fatigue lives, the fatigue anisotropy strongly depends on the projection area of the lack-of-fusion defects relative to the loading direction, resulting in better fatigue performance for the TD samples. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the development and validation of a low-cost device for real-time detection of fatigue damage of structures subjected to vibrations. The device consists of an hardware and signal processing algorithm to detect and monitor variations in the structural response due to damage accumulation. The effectiveness of the device is demonstrated through experimental validation on a simple Y-shaped specimen subjected to fatigue loading. The results show that the device can accurately detect structural damage and provide real-time feedback on the health status of the structure. The low-cost and easy-to-implement nature of the device makes it promising for use in structural health monitoring applications in various industrial sectors. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Shanghai Jiaotong University (Science) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A stress severity factor method for vibration fatigue life analysis of joints is proposed for the problems of stress concentration and contact nonlinearity, which is based on stress severity factor (SSF) method of quasi-static fatigue analysis for stress concentration and contact. The method can be extended to random vibration. An equivalent SSF model is used to calculate the stress response. An example shows that the calculation errors of vibration fatigue life under two excitation spectrums are 27.3% and 30.7% respectively. It indicates that the SSF method is fast and accurate, and meets the requirements of rapid estimation of vibration fatigue life of joints in engineering. [ABSTRACT FROM AUTHOR]

Three-dimensional braided Cf/Al composites prepared by vacuum pressure infiltration method have good mechanical properties and great potential in aerospace applications. In this paper, the three-dimensional braided Cf/Al composites were taken as the research object, and the vibration fatigue tests were carried out under different loading stresses, and the microstructure of the fracture was observed after the fatigue tests. The test results show that the greater the loading stress is, the greater the percentage of natural frequency decrease is when T-shaped part reaches reach the fatigue stability stage, that is, the more significant the damage to the internal structure of T-shaped part is. By fitting the fatigue data under different loading stresses and drawing the S-N curve, the mathematical model of vibration fatigue damage evolution law of T-shaped part is obtained, which can be used to predict the life of three-dimensional braided Cf/Al composites. It is found that T-shaped part after the experiment shows typical brittle fracture characteristics through the macroscopic and microscopic analysis of the fracture . [ABSTRACT FROM AUTHOR]

In this paper, the dynamic behavior of a hip level joint device of an active exoskeleton used in the medical field is analyzed. The finite element method is used in order to determine the first frequencies and the eigenmodes, necessary for the fatigue testing in the resonance regime. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Vibration fatigue failure behavior of Ni-based single crystal FCH structure at high temperature were studied. • Crack initiation mechanism of FCH structure is oxidative cracking nucleation in stress concentration area. • Crack propagation mechanism is the competition mechanism of dislocation slip and dislocation climbing. • Vibration fatigue life prediction model considering stress concentration and high-temperature oxidation was proposed. • Life prediction accuracy is within 2.5-time scatter band, so life prediction model proposed has high prediction accuracy. The vibration fatigue failure behavior and fatigue life of the film cooling hole (FCH) structure of Ni-based single crystal superalloy were investigated at high temperature. The vibration fatigue test of the FCH specimens were carried out based on the paired staircase method. The cracks are mostly initiated in the stress concentration area at the edge of the FCH, and may also be initiated in non-stress concentrated areas with large defects. At high temperature, the crack initiation mechanism of the FCH specimens of Ni-based single crystal superalloy is oxidative cracking nucleation in stress concentration area, and the crack propagation mechanism is the competition mechanism of dislocation slip and dislocation climbing. Based on the Fatigue Indicator Parameter (FIP) of the critical plane method, a vibration fatigue life prediction model for FCH structures considering stress concentration and high temperature oxidation damage is proposed. The life prediction model proposed in this paper is applied to the vibration fatigue life prediction of FCH specimens. The deviation between the predicted results and the experimental results is within 2.5 times at 850℃, and the deviation is within 2 times at 980℃. Besides, the life prediction method proposed is compared with other two FIP life prediction methods, and the high accuracy and effectiveness of the proposed life prediction method are verified. [ABSTRACT FROM AUTHOR]

• A combined model which can predict the residual strength curve under random fatigue loadings is proposed. • The proposed model can predict the residual strength probability density function under random fatigue loadings. • This probabilistic prediction method can effectively consider the loading randomness and the dispersion of composites strength. A new method based on combined residual stiffness-strength degradation is developed to predict the failure probability of plain weave composites subjected to random fatigue loadings. All the parameters presented in the proposed analytical model are characterized using the outcomes from quasi-static and constant amplitude fatigue testing. The evolution of residual strength is obtained based on combined residual stiffness-strength degradation model, which can greatly reduce the cost of the experiments. The Weibull distribution with two parameters is used to account for the dispersion of residual strength. Combing with randomness statistics of the fatigue loadings and the interference criterion of stress-strength, the fatigue failure behavior and failure probability are obtained. The narrow-band random vibration experiments were conducted to generate the random loadings and validate the predicted results. The approach proposed in this paper takes full advantage of residual stiffness or residual strength method and has better accuracy. [ABSTRACT FROM AUTHOR]

• Field Test: Conducted a field test to understand failure mechanisms of the railway bogie lifeguard due to wheel/rail high frequency impact. • High Frequency Transfer Analysis: The nonlinear properties of hydraulic damper up to 80 Hz were explored through field test and laboratory tests. • Random Vibration Model: Developed a random vibration model to reproduce high frequency vibration of bogie system. • Structural Optimization: A new designed structure for the lifeguard of metro bogie was proposed and validated through the simulation of the proposed numerical model considering measured axle box acceleration. The sub-components of railway bogie have been frequently reported to be subjected to the vibration fatigue due to the wheel/rail high frequency vibration. An efficiency numerical model is thus desirable to simulate the high frequency vibration of railway bogie, which can substantially enhance the design efficiency of railway bogie system considering the vibration fatigue. Therefore, this paper aims to proposing a modelling methodology for simulating the high frequency vibration of railway bogies' subcomponents, and a lifeguard of metro bogie was taken as an example. Firstly, a field test measurement of lifeguard for the metro bogie was primarily introduced to demonstrate the high frequency vibration characteristics and the related failure mechanisms arising from the wheel/rail high frequency impact. Subsequently, a random vibration model for the railway bogie system and the lifeguard based on the rigid/flexible coupled dynamics were developed to simulate the high frequency vibration and the dynamic stress developed at the lifeguard. This method was subsequently employed in the structural optimization for the lifeguard. The results showed that the proposed methodology can effectively simulate the high frequency vibration of lifeguard of bogie system based on the measured axle box acceleration, and the optimized structure can effectively increase the service lifetime under the excitation of wheel/rail high frequency vibration. [ABSTRACT FROM AUTHOR]

• The fatigue performance of DZ125L alloy under bimodal random processes was studied. • The distribution of fatigue damage in bimodal random processes was analyzed. • The bimodal random vibration fatigue crack propagation mechanism was proposed. • The proposed new model is more suitable for the life prediction of bimodal processes. During actual service, aviation aircraft often experience multiple complex alternating loads coupled with each other. If the frequency range of the excitation load spectrum covers the first two resonance frequencies of the structure, it can significantly impact the vibration fatigue life of the structure. In this study, bimodal random vibration fatigue tests were conducted on thin plates composed of DZ125L directionally solidified superalloy. The impact of low-frequency and high-frequency vibration signal intensities on the vibration fatigue behavior of DZ125L alloy thin plates was investigated separately during bimodal random processes. The crack propagation mechanism of bimodal random vibration fatigue was proposed based on the fracture morphology observed in DZ125L alloy thin plates that failed due to vibration fatigue. The study findings indicate that the number and location of crack initiation zones can influence the mechanism of fatigue crack propagation. Additionally, a new model was developed in this study to enhance the sensitivity of the frequency domain method to the intensity of low-frequency and high-frequency vibration signals in bimodal random processes. Compared to traditional frequency domain methods used for broadband and bimodal processes, the new model can effectively describe the variation characteristics of bimodal fatigue life with different component process intensities. Furthermore, it has broader applicability for predicting the vibration fatigue life of bimodal random processes with varying vibration signal intensities. [ABSTRACT FROM AUTHOR]

Vibration is the main factor causing high cycle fatigue. The macro-response stress and strain of the structure under the excitation of vibration load are generally in the elastic stage. However, fatigue failure still occurs due to long-term cyclic load, which is unexplainable by the macro-plastic accumulation method. Therefore, a two-scale nonlinear damage accumulation model is proposed for vibration fatigue based on the physical characteristics of multi-scale fatigue damage evolution. In this model, two-scale elastic-plastic constitutive equations based on the equivalent inclusion theory are built, and a two-stage damage accumulation strategy with two critical damages is designed. A resonance fatigue life prediction algorithm is established based on the proposed model, and a validation test is carried out using the cantilever beam made of GH4169 alloy. The results show that the deviation between the vibration fatigue life prediction and test results is within a scatter band of factor 2, indicating that the two-scale nonlinear damage accumulation model is effective in the vibration fatigue region. • Two-scale equations with equivalent inclusion theory are built for vibration fatigue. • Cross-scale damage accumulation strategy with two critical damages is first proposed. • Vibration life predictions and test results are within a scatter band of factor 2. [ABSTRACT FROM AUTHOR]

The overall stiffness and modal frequency of the car body of a rapid box car are reduced by the design of the full-side open movable side door structure. The vibration fatigue performance of the welded structure in this car body needs to be verified. The rigid-flexible coupling model of the rapid box wagon was established first, and the model was verified by modal test data. By the application of the virtual iteration method on this model, the displacement excitation loads of this vehicle were acquired. The effectiveness of the load reverse obtaining technology was verified through the comparison between calculated data and the experimental data. Based on the rigid-flexible coupling model and the load obtained by reverse engineering, the fatigue life of the welded structure in the car body was evaluated through the modal structural stress method. The calculated results show that the car body structure obtains obvious modal vibration, which leads to short fatigue life in several weld lines. According to the application requirements of this wagon, the local improvement scheme was proposed, and the effect of the improvement program was evaluated. In this paper, a new fatigue evaluation technology based on the load reverse method of test data was proposed, which provides a theoretical basis for the structural design and program improvement of railway vehicles. [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]

When applied to transportation systems, fuel cell structures are exposed to external mechanical disturbance including shocks and harmonic excitations from operating components. To minimize performance degradation from machine operations, the fuel cell structure needs to be examined via vibration reliability tests. In this study, the reduction in the clamping force of the stack by random vibrations was investigated by experiments. The stack mass and gasket were clamped with bolts for vibration tests. The vibration induced shear movements between clamped stacks. To estimate the vibration input magnitudes, the Dirlik method was used. The reduction in the stack clamping force was estimated using the Basquin's power law. The clamping force decreased by the shear vibration input to the stack structure. The degree of clamping force reduction was larger for the heavier stack. When the stacks were separated by the gasket the reduction became smaller. Through the Dirlik method, the vibration reliability of the stack was evaluated. This information provides severity of the external vibration on the stack functionality. • The shear force applied to the stack by external vibration reduced the clamping force. • Dirlik method was used to estimate the random vibration input magnitudes. • Clamping force reduction was larger for heavier stack. • Clamping force variation was smaller when gaskets were inserted between stacks. • Vibration-induced damage to Stack follows the Basquin power law. [ABSTRACT FROM AUTHOR]

A vibration‐based bending fatigue test based on electrodynamic shaker is conducted in order to study the high cycle and very high cycle fatigue (VHCF) behaviors of a titanium alloy TC17 with a sort of novel specimens. After obtaining a full S‐N curve covering the lifetime up to 109 cycles, several fatigue crack initiation and failure process modes are revealed based on the observation of the fracture surfaces. Especially, the statistical distribution characteristics of the fatigue lifetime and some relevant factors are discussed. The results indicate that the obtained S‐N curve does not exhibit a plateau region in the VHCF regime. And the present crack initiation mechanism involves the facets formed by the primary α‐phase cleavage and the development of microcracks. Moreover, the scatter of the fatigue lifetime can be obviously influenced by the resonance frequency range of the specimens. [ABSTRACT FROM AUTHOR]

Fiber-reinforced resin-based plastics are widely used in structural composites for aerospace and automotive applications, and they often face extreme load conditions in actual working environments. It is challenging to monitor the damage of the structure during the vibration process. This study was aimed at using buckypaper (BP) sensors to monitor the structural health status of composite structures under ambient vibrations. First, the feasibility of flexible printed circuit instead of wire is verified by the tensile experiment. Then the vibration monitoring experiment of the composite cantilever beam is carried out by using BP sensors systematically. The sweep frequency experiment determines the excitation frequency of the cantilever beam. Low-period vibration fatigue cycle and high-period vibration fatigue cycle experiments are designed to verify the vibration monitoring method using BP sensors. Besides, the signal response of BP sensors in the vibration experiment is analyzed, and the relationship between ΔR/R0 and vibration acceleration is obtained. Finally, through the change law of ΔR/R0 of the sensor, the cumulative damage caused by vibration fatigue is visualized. It is demonstrated that the monitoring method based on BP sensors can be applied to study the damage behavior of composite structure under the vibration environment. Abbreviations: FRP, fiber-reinforced resin-based plastics; SHM, structural health monitoring; SEM, scanning electron microscopic; FPC, flexible printed circuit; FBG, Fiber Bragg Grating; AE, acoustic emission.

• DSOLSP processing is proposed for the small-sized blisk. • DSOLSP causes a two-way bending deformation of the blade. • The gradient microstructure and full-thickness CRS are induced by DSOLSP. • The vibration fatigue strength of the DSOLSPed blades increased by 25.9%. • The anti-fatigue mechanism of DSOLSP is elucidated. Double-sided symmetric oblique laser shock peening (DSOLSP) was adopted to experiment on a small-sized blisk with restricted space. The influences of different laser energies on the shape deviation, surface roughness, microhardness, and residual stress of the blades were studied. The optimum process parameters were selected based on the shape deviation results of the blades and the microstructural evolution of the surface layers was investigated. The strengthening effect of DSOLSP treatment on notched blades was evaluated by vibration fatigue tests. It was found that DSOLSP can effectively cover the fatigue vulnerable regions without interference. Two-way bending deformation was formed after DSOLSP, and the shape deviation of the blades could be controlled within ±0.02 mm. With the increase of laser energy, the surface roughness and the depth of work-hardened layer increased. The full-thickness compressive residual stress (CRS) field was induced. A gradient microstructure was generated on the surface of the blade, and the size of average nanograins on the topmost surface is approximately 36.5 nm. The fatigue strength of the DSOLSP treated blades with notches was increased by 25.9 %. The enhancement can be attributed to the synergistic strengthening of CRS and gradient microstructure. [ABSTRACT FROM AUTHOR]

• We present a data-driven framework to establish spectral multiaxial fatigue criteria. • The method can be used for multiaxial fatigue analysis in the frequency domain. • The method explicitly addresses the non-proportional multiaxial stress effect. • Different time-domain multiaxial fatigue criteria can be adopted into their spectral equivalent. • Various data-driven models can be incorporated into the framework. Random vibration fatigue of structures is intrinsically multiaxial, driven by complex stress states. Non-proportional multiaxial stresses exacerbate fatigue damage compared to proportional stresses. Frequency domain fatigue analysis is generally more efficient for structures operating near natural frequencies. However, handling non-proportional multiaxial stress effects in the frequency domain remains challenging. This paper introduces a data-driven framework that reformulates time domain multiaxial fatigue failure criteria into their frequency domain counterparts, explicitly addressing non-proportional effects. The method introduces a non-proportional correction factor into the power spectral density of equivalent stress, determined through a data-driven approach, converting various time domain multiaxial fatigue criteria into their frequency domain equivalents. Combined with modal decomposition analysis, this approach efficiently evaluates multiaxial vibration fatigue for engineering structures, effectively accounting for non-proportional stress effects. [ABSTRACT FROM AUTHOR]