•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.
•The high-frequency vibrations and stresses of bogie cowcatchers under rail corrugation is investigated by full-scale field test.•The resonance between the modal vibration and rail corrugation for ...bogie cowcatchers is found to be the main contributor to the fatigue failure.•The vehicle system dynamic model is developed and validated based on the rigid-flexible coupled dynamic theory and stress recovery approach.•Parametric studies are conducted to reveal the effects of rail grinding and structural modification on the high-frequency performance.
This paper describes the high-frequency vibration fatigue failure of metro bogie cowcatchers due to short-pitch track irregularities through field testing and numerical simulations. Firstly, the dynamic stress and vibrational environment of bogie cowcatchers are investigated by full-scale testing. The acceleration spectrum density and fatigue strength of cowcatchers are evaluated. Secondly, the internal and external contributors to this issue are preliminarily analyzed through modal experiments and track irregularity measurements. Then, the rigid-flexible coupled dynamic model of the vehicle is established based on the modal synthesis method and stress recovery technique. The calculated and measured vibration and stress of the bogie cowcatchers are compared for model verification. Finally, potential solutions, i.e. rail grinding and new structure design, are proposed and verified to solve the fatigue failure issue. It is found that the modal stress at hot spot locations around the weld lines of cowcatchers can be easily excited in operations and even coincides with the frequency of the rail corrugation. One efficient treatment of this issue is the rail grinding, another one is to increase the modal frequency and eliminate stress concentration with a new structure design.
•An innovative RSM is developed for fatigue life assessment with high efficiency.•The FDRS is defined to quantify the mode damage contribution of the MDOF system.•The MRS format is proposed, with ...partial consideration of mode cross-correlation.•The applicability of three formats of the RSM to the engineering problem is verified.
In this paper, a new response spectrum method is proposed for high-cycle fatigue damage assessment of a linear multi-degree-of-freedom system subjected to random base acceleration. Mode damage response can be accessed by separating the modal participation factor and stress mode from the contribution of a mode to the total damage, assessed by the Single Moment method. The fatigue damage response spectrum is defined as the family of curves formed by the mode damage response with the variation of the frequency and modal damping ratio, which is irrelevant to the spatial characteristics of the load and structure. Three calculation formats of the response spectrum method are formed by considering different cross-correlation hypotheses of each mode (i.e. the Complete Quadratic Combination format, the Square Root of the Sum of Squares format, and the Modified Square Root of the Sum of Squares format). The proposed method has higher computational efficiency than other frequency-domain methods because of avoiding the calculation of power spectral density function and spectral moment of stress responses. The spatial and frequency information of the structure are decoupled from each other in the implementation, which can effectively reduce the computational cost of reanalysis. Compared to the result of the Dirlik method (self-compiled program and MSC.Patran/Nastran) and the Single Moment method, the correctness and efficiency of the proposed method are verified, and the influences of the material and load spectrum form on the response spectrum method are investigated.
To investigate the improvement in vibration fatigue and the strengthening mechanism of laser shock peening, a nanosecond laser was used to strengthen the 2024-T351 aluminium alloy. Accordingly, the ...microstructure, residual stress, nanohardness and surface roughness of the treated alloy were measured. Subsequently, the vibration fatigue damage and fatigue life were evaluated, and the vibration fracture morphology was observed. The results showed that the grains in the peened surface were refined. A residual stress of −141 MPa and a nanohardness of 3.1 GPa were obtained by laser shock peening. Based on the relationship between the peened microstructure and fracture morphology, it was deduced that an increase in the grain boundaries led to a lower crack initiation rate and a higher crack initiation life. The compressive residual stress decreased the crack growth rate and increased the crack growth life. Therefore, laser shock peening increases the total vibration fatigue life by about 63.5%.
•The distribution of microstructure had important effects on fatigue fracture process.•The mechanism of vibration fatigue life extension induced by LSP was studied.•Vibration fatigue damage was decreased and fatigue life was increased by LSP.
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•Theoretical and experimental research on non-Gaussianity and non-stationarity excitation.•High-cycle fatigue of flexible structures excited close to natural ...frequencies.•Non-stationarity excitation significantly impacts the fatigue life.•Non-stationary vs non-Gaussian excitation were found much more important.
In vibration fatigue, flexible structures operate at or close to their natural frequencies. Therefore, it is common to consider the input excitation as well as the stress/strain response of the structure to be Gaussian and stationary. In reality, a non-Gaussian and non-stationary excitation is frequently observed, resulting in a possibly non-Gaussian and non-stationary response. The importance of this non-Gaussianity (typically observed via the kurtosis) has resulted in significant research on the relevance of the Gaussian assumption in fatigue life. For dynamic structures the prior research was mainly theoretically and numerically focused. This work researches the importance of non-Gaussianity and non-stationarity theoretically, numerically and experimentally. Y-shaped specimens were used in this research. The excitation close to the natural frequency is random and in all the researched cases with the same power spectral density (PSD). While the PSD was kept the same, the rate of non-Gaussianity and the non-stationarity were changed. The results show that when the excitation is stationary and non-Gaussian, the fatigue life is not significantly impacted, and that standard frequency-counting methods are applicable. However, for the case of a non-stationary, non-Gaussian excitation, the fatigue life was found to be significantly impacted and the Gaussian theoretical approach is questionable.
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•A novel fatigue response spectrum method is proposed for high-cycle fatigue.•The quasi-static response is introduced to modify the modal truncation error.•The complete SRSS rule is ...adopted to reduce the cost of cross-correlation analysis.•The impact factors of modal truncation error in fatigue assessment are investigated.
In this paper, a more accurate and efficient format of the fatigue response spectrum method is further proposed considering modal truncation error. Firstly, the quasi-static response of higher-order modes is taken into account to modify the modal truncation error. Then, an analytical description of the cross-correlation between the modal responses as well as quasi-static response is developed by two coefficients associated with the natural frequency and modal damping ratio. Finally, the expected damage rate is transformed into a summation of modal damage responses strictly, resulting in a dual improvement in accuracy and efficiency. In numerical examples, the correctness and efficiency are verified and the influences of load spectrum and material fatigue properties on the modal truncation error are further investigated.
•A frequency method based on Gaussian expansion has been proposed for vibration fatigue analysis of acoustic black hole structures.•The most dangerous point of ABH beam varies with load types and it ...is not safer with the increase of truncation thickness.•The existence of ABH will reduce the fatigue strength of ABH plate while using the damping layer could solving this problem.
The acoustic black hole (ABH) effect has shown great application potential in vibration reduction, energy harvesting, etc. However, it may face the problem of structural strength due to the small thickness in local area. In this study, a frequency method based on Gaussian expansion has been proposed for fatigue analysis of ABH structure. Fatigue damage is directly estimated in the frequency domain through the properties of the modal model of ABH structures. Numerical results show that the proposed method can well deal with both 1D and 2D ABH structures with a good accuracy.
•High frequency vibration of antenna beam has been investigated experimentally.•Rail corrugation induced vibration fatigue has been analyzed through the measurements.•Coupled vehicle/track dynamic ...model is formulated considering the flexibility of antenna beam to optimize the structural of antenna beam.•A novel design is proposed to enhance the fatigue lifetime of antenna beam.
This paper investigated on the high frequency vibration-induced fatigue failure of antenna beam through both field tests and numerical simulation. In the field tests, the dynamic stress, acceleration, and operational modal of bogie system as well as the short pitch irregularities of rail were measured to identify the primary contributor to the fatigue failure of antenna beam. The result suggested that the rail corrugation- induced impact with the passing frequency of 78 Hz serves as the main driving force of the modal resonance for bogie frame and antenna beam in the bogie system, which can emphasis the bending of antenna beam and further contribute to the reduced fatigue lifetime. To better understanding the failure mechanism and the associated mitigation method, a rigid/flexible coupled dynamic model of rail vehicle, considering the flexibility of bogie frame, wheelset and antenna beam as well as coil spring, was developed by using the modal synthesis method. Based on the developed model, the influence of elastic rubber mounts located on both ends of antenna beam was investigated, and a new design was proposed to relief the bending movement- induced stress concentration in the antenna beam. This is expected to mitigate the vibration fatigue problem of antenna beam arising from the rail corrugation-induced high frequency wheel/rail impact.
During thermal barrier coatings (TBCs) service, high-temperature and vibration are environmental factors that cannot be ignored. The vibration fatigue damage mode of TBCs under operating conditions ...that couple vibrations with high temperatures is unclear. In this paper, a high-temperature vibration coupled environment simulator was developed to investigate the evolution of high-temperature vibration fatigue damage modes of LaZrCeO/7-YSZ(LZC/YSZ) TBCs under alternating loads by employing acoustic emission detection. The results show that in the initial fatigue stage, the damage appears as discrete micro-cracks formed by the initial defects in the TBCs. With the increase in the number of cycles, the initiation of transverse microcracks began to occur inside the LZC layer and at the LZC/YSZ interface. When the transverse microcracks accumulate to the critical value, the applied alternating loads accelerate the propagation of opening interfacial cracks. Finally, the columnar crystal structures of the ceramic layers fracture at different heights under cyclic loading by high-temperature vibrations.
•A high-temperature vibration-coupled environmental simulator was developed.•Damage accumulation and failure of TBCs were monitored using acoustic emission.•Vibratory alternating loads accelerate the extension of opening interfacial cracks.
The mechanical failure of battery-pack systems (BPSs) under crush and vibration conditions is a crucial research topic in automotive engineering. Most studies evaluate the mechanical properties of ...BPSs under a single operating condition. In this study, a dual-objective optimization method based on non-dominated sorting genetic algorithm II (NSGA-II) is proposed to evaluate the crushing stress of BPS modules and the vibration fatigue life of the BPS. This method can obtain better combinations of the thicknesses of the BPS components, which helps engineers achieve robust and efficient designs. First, a nonlinear finite element (FE) model of a BPS is developed and experimentally verified. The crush and vibration simulations are performed, and the FE analysis data are obtained. Second, two third-order response surface models are created to characterize the relationship between the input (thicknesses of the BPS components) and the output (crushing stress of the BPS modules and vibration fatigue life of the BPS). Finally, a linear weighting model and an NSGA-II model are used to conduct dual-objective optimization. The solution of the linear weighting method and the non-dominated Pareto solution set of the thicknesses of the BPS components are obtained and compared. Furthermore, a reasonable interval in the Pareto frontier is defined and considered the best solution to the dual-objective optimization problem. Therefore, the reliability of the BPS is improved to ensure the safety of electric vehicles in crushing and vibration environments. This method offers an effective solution to the problem of evaluating the mechanical responses of BPSs under various operating conditions. It can be used to generate a robust design for safe and durable BPSs.
