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The vast changes in temperature are what produce thermal fatigue damage to concrete. In this study, concrete specimens in three different categories—C20, C40, and C60—are tested for thermal fatigue at temperatures ranging from 10°C to 80°C in an atmosphere with constant relative humidity. Utilizing ultrasonic nondestructive testing, the elastic modulus of concrete is determined. After thermal cycling, the mass reduction and appearance of samples are also recorded. The results demonstrate that the degrading effects of thermal fatigue clearly influence concrete. As the thermal cycle lengthens, the elastic modulus of concrete rapidly decreases, and C60 concrete experiences a greater reduction in elastic modulus than C20 concrete. With thermal cycles, the damage factor increases and the ultrasonic wave velocity steadily decreases, suggesting a propagation of the concrete's interior microcracks. Additionally, the micromechanical thermal fatigue model is developed based on the experimental results. The ability to simulate and describe the physical behavior of concrete under thermal fatigue stress on the microscale is validated by the proposed micromechanical damage model. [ABSTRACT FROM AUTHOR]

The non-uniformly distributed wheel loads in orthotropic bridge decks will cause its lower components to be eccentrically loaded. By conducting numerical simulation, field measurement and fatigue tests of diaphragm-to-rib welded joints (DU), the crack-growth characteristics under eccentric loading were analyzed and compared with that under symmetric loading, through which the warning crack length for maintenance and an evaluating method for crack-growth rates were proposed. The result demonstrates that the eccentrically loaded side (ES) of DU will crack ahead of non-eccentric side (NES) with a larger growth angle. The crack performs the same three-stage features of fast-slow-rapid growth under eccentric loading with demarcations of 27 mm and 70 mm, which are obviously larger than that under symmetric loading. The weld toe on NES will be particularly prone to fatigue cracking once the crack on ES enters the third rapid-growth stage. The new initiated crack on NES will own the same growth rate as ES. The demarcation 70 mm shall be taken as the warning length for crack maintenance to avoid cracking on the other side. It is appliable to evaluate the crack-growth rate of DU by Paris formula and the maximum stress intensity factor obtained by KI and KII of mixed mode cracks. [ABSTRACT FROM AUTHOR]

Our study delves into analyzing fatigue damage in notched structures, an essential field in structural mechanics. We aim to understand how geometric and dimensional variations in the notches affect fatigue damage under different modes and amplitudes of cyclic loading, focussing on the behavior of steel. Our research methodology integrates experimental and numerical approaches. Experimental validation encompasses material properties, mesh selection, and boundary conditions. The finite element method is tailored to address steel's elastoplastic behavior, employing calibrated parameters for kinematic and isotropic cyclic hardening models within the numerical realm. Specific findings elucidate the cyclic response of notched structures, tracking damage progression to critical thresholds, including the number of cycles to failure (Nf) and the critical crack length (Lc). Hysteresis curves vividly depict stress–strain relationships, offering insight into material behavior under cyclic loading. Implications span engineering domains, focussing on reliability and durability in the aerospace, automotive, and civil engineering sectors. Future directions include real-world applications and advanced techniques such as the Extended Finite Element Method (XFEM). In conclusion, this research enriches our understanding of fatigue damage analysis in notched structures, poised to impact safety and robust engineering design. [ABSTRACT FROM AUTHOR]

Steel fiber-reinforced concrete material has garnered significant attention in structure design due to its excellent resistance to fatigue damage. The application of the plain concrete microplane model is extended to steel fiber-reinforced concrete by modifying the stress-strain boundary conditions on the microplane and then extended to fatigue damage analysis by considering fatigue-related material stiffness, mainly concerned with tensile damage, mainly concerned with tensile damage. The normal positive strain on the micro-plane is regarded as the fatigue variable, and the fatigue history variable is the accumulation of the fatigue variable during the loading. The relationship between the fatigue history variable and the material stiffness fatigue degradation function is established. In the numerical implementation, the crack band model is combined to reduce the mesh sensitivity caused by strain localization. During the numerical simulation, the parameters of plain concrete, steel fiber-reinforced concrete, and the material fatigue degradation function can be calibrated sequentially, requiring only a few benchmark tests for accurate parameter calibration. The numerical results show that this model can be used for the fatigue damage analysis of plain concrete and steel fiber-reinforced concrete material. It is expected to be used for the refined analysis of concrete structures under complex loading conditions and structural forms in the future, providing convenience to engineering design, evaluation, and optimization. [ABSTRACT FROM AUTHOR]

ABSTRACT The present work shows an approach to monitor the evolution of the dislocation arrangement of a metallic material caused by cyclic plastic strain using white X‐ray radiation in combination with an energy‐dispersive detector. The method is demonstrated by single‐shot experiments performed on polycrystalline nickel and α‐brass, representing the pure wavy and the pure planar dislocation slip behavior. To correlate the resulting diffraction patterns with various dislocation arrangements of both metals, fatigue tests were carried out up to certain numbers of cycles and at predetermined plastic strain amplitudes. The differences in dislocation microstructure and internal stress distributions give rise to an appreciable change in the peak shape of Laue reflections, leading to unique characteristics in the respective diffraction patterns. Nickel reflections are elongated due to the high amount of cell structures leading to bending and misorientation of the lattice, whereas the present stacking faults in α‐brass result in powder‐like diffraction. [ABSTRACT FROM AUTHOR]

ABSTRACT Hydrogenated nitrile butyl rubber (HNBR) elastomers are widely used in high‐temperature and high‐pressure (HTHP) corrosive environments, especially in the oil and gas sector. However, fatigue failure, which is often encountered in rubber components, remains a critical issue. In this paper, the effect of HTHP aging on the fatigue damage characteristics of HNBR in an oil‐based mud environment is investigated through experiments and numerical simulations. The experimental results showed that the elongation at break of the specimens decreased by 260% and the compressive stiffness increased with strain after high‐temperature and high‐pressure exposure in the oil‐based mud. Furthermore, tear tests showed that the rate at which the aged HNBR produced unit crack surfaces was significantly accelerated. Finally, the fracture and fatigue crack extension simulation results show the similarity between the damage evolution law of HNBR materials and the stress–strain curve of typical rubber materials. [ABSTRACT FROM AUTHOR]

The Francis runner is a critical component of the Francis turbine generator unit, playing a central role in converting water energy into rotating mechanical energy that drives the generator in hydropower stations. In-depth analyses of the flow characteristics of the Francis runner under various operating conditions and avoiding fatigue damage of the Francis runner are crucial to the reliability and efficiency of hydropower operation. In this paper, the flow dynamics of a large Francis turbine runner are analyzed under three representative loading conditions—low partial load, high partial load, and full load—and the flow-induced stress of the runner is analyzed under these loading conditions. It was found that the maximum static and dynamics stresses of the runner at three representative loading conditions are located at the chamfered surface where the blade trailing edge connects to the runner crown. The maximum static stresses of the Francis runner are 284 MPa, 352 MPa, and 381 MPa at low partial load, high partial load, and full load, respectively, and they are above the allowable stress limits, as half of the yield stress of the runner material of 550 MPa. The peak-to-peak values of runner dynamic stress at low partial load, high partial load, and full load are 15 MPa, 25 MPa, and 14.6 MPa, respectively. The high stress invoked by the unsteady flow under various loading conditions in this runner was the cause of the fatigue breakage of the runner blades. The results of this investigation have important reference values for mitigating fatigue damage in similar Francis runners and optimizing unit operation. [ABSTRACT FROM AUTHOR]

Due to harsh service conditions, fatigue damage is the main reason for numerous catastrophic accidents of ships and offshore constructions. This paper uses a nonlinear ultrasonic technique to monitor the evolution of fatigue microcracks in marine steel AH36. An experimental system was established and nonlinear ultrasonic inspections were conducted on the specimens with different fatigue degrees. The microstructural changes induced by fatigue loading were also studied by microscopic observation. The experimental results demonstrate that the normalised nonlinear parameters show a closed relation to the evolution of fatigue microcracks in steel AH36. Meanwhile, microscopic observation indicates that the microcrack generation mode and grain boundary cracking are the two mechanisms for microcrack generation. Both the generation and growth of the microcracks contribute to the rise of the nonlinear effect. Consequently, the nonlinear ultrasonic techniques provide a reliable and effective method for monitoring the evolution of fatigue microcracks in marine high-strength steel. [ABSTRACT FROM AUTHOR]

A bottom–up multi-scale performance transfer chain is developed to ascertain the gradual change in the law of vibration characteristics in spatial steel truss structures under fatigue loading. This chain derives the interrelationship between vibration characteristics and the performance of each structural component. Based on the evolution characteristics of the performance model of the member scale in the transfer chain, a new analytical model of the shape function is established. Building on these foundations, a refined model was formulated to depict the gradual change of vibration characteristics in spatial steel truss systems under fatigue loading. This model integrates the cumulative damage rule, the structural residual performance rule, the finite element method and other pertinent theories. The gradual change in vibration characteristics of a steel truss girder bridge subjected to train loads was analyzed using a self-developed three-dimensional finite element analysis framework tailored explicitly for assessing gradual change issues in spatial steel truss structures. The analysis results indicate that the effective residual cross-sectional area and the structural frequency continuously decline as the service time increases. This comprehensive study advances the understanding of fatigue-induced changes in spatial steel truss structures. It offers analytical perspectives for predicting and mitigating the long-term impacts of dynamic loads on large-scale infrastructural components. [ABSTRACT FROM AUTHOR]

Purpose: This work proposes a multilayer methodology for assessing the lifetime of steam turbine blades based on damage calculation, fracture mechanics considerations, and probabilistic analysis. Methods: The life consumption of steam turbine components is determined through evaluation of steady-state stresses (thermal and centrifugal) and transient stresses. Transient stress analysis is conducted for cold start, warm start, and hot start scenarios, utilizing startup curves derived from available site information and operation manuals. Temperature and stress distributions are determined, followed by life estimation calculations for Creep life damage and fatigue damage using modified Miner and Palmgren's rule. Results: Analysis reveals that maximum damage occurs during cold start due to the generation of maximum transient stresses. Critical crack size and time to failure assuming a notch are calculated through fracture mechanics considerations. Conclusion: The proposed multilayer methodology offers a comprehensive approach to assessing the lifetime of steam turbine blades, integrating damage calculation, fracture mechanics, and probabilistic analysis. This approach enhances understanding of blade performance under various operating conditions and aids in optimizing maintenance strategies for steam turbine systems. [ABSTRACT FROM AUTHOR]

Fatigue damage is a notable distress of asphalt pavements. However, monitoring the development process of such distresses in real-time remained challenges for researchers. In this paper, the self-developed sensing facility has been utilized to obtain aggregate kinematic response of semi-circular specimen during the fatigue loading process in the upper-middle (H/2), lower-middle (L/2) and lower-right (L/3) positions of the specimen. Angle and acceleration variation in the X, Y, and Z directions were analysed independently at three positions. The correlation between the kinematic characteristic of the aggregate and the vertical deformation of the asphalt mixture specimen is established. The results illustrated that the asphalt mixture viscoelasticity attenuation during fatigue test caused the angle accumulation and acceleration response change of the specimen. The angle accumulation in the X-axis direction and acceleration variation in Y-axis direction of the aggregate at the H/2 position exhibited a significant three-stage change. Angle-Accumulation Rate (AAR) of change is suggested as a long-term monitoring index for the fatigue development of the asphalt mixture. The proposal of AAR index creatively combines the long-term kinematic behaviour and mechanical behaviour of asphalt mixture, making long-term and real-time monitoring of the asphalt pavement health from the perspective of kinematics become possible. [ABSTRACT FROM AUTHOR]

The fatigue damage evolution of rocks subjected to cyclic loading and unloading has always been a hot spot that receives worldwide attention in the field of rock mechanics. Recent studies that rely on advanced nondestructive testing (NDT) techniques enable accurate monitoring and assessment of the dynamic damage in cyclically loaded rocks, and well contribute to revealing the complicated failure mechanism. These works are critical to ensure safe underground tunnelling and mining activities. As a promising NDT technique, the electromechanical impedance method (EMI) has been successfully applied to many aspects in structure health monitoring. In this paper, the EMI method was extended to measuring the rock fatigue damage. Firstly, uniaxial cyclic compression tests with increasing amplitude were performed on three types of cylindrical rock specimens, including sandstone, granite and carbonaceous shale. The varying mechanical properties and energy conversion characteristics were analyzed. In particular, the damage evolution characterized by elastic energy dissipation was determined. Concurrently with cyclic tests, conductance signatures in response to two excitation modes of the surface-bonded piezoelectric transducers were collected, and the spectral localized and overall variations were analyzed. It is discovered that the resonant frequency shift and the statistic metric MAPD within the transverse mode-dominated frequency range could accurately indicate the rock fatigue damage. This research sufficiently confirms the effectiveness and reliability of the EMI method in quantifying the accumulative damage of different rocks under uniaxial cyclic loading and unloading. Highlights: The damage evolution based on energy dissipation of rocks under uniaxial cyclic compression was studied. The localized and overall variations of conductance spectra of PZT transducers were tracked and analyzed. The resonance frequency shift is consistent with the fatigue damage evolution of cyclically loaded rocks. The metric MAPD under the d33-dominated mode serves as an excellent indicator of rock fatigue damage. [ABSTRACT FROM AUTHOR]

Floating ice loading is a severe natural hazard for offshore wind turbines (OWTs) operating in cold sea regions. The long-term ice-induced vibration resulting from winter drift ice presents a significant threat to the fatigue reliability of OWTs. Machine learning not only exhibits robust data-driven capabilities but also efficiently handles complex relationships among multiple factors. Through effective learning and utilization of diverse features, a comprehensive assessment of the fatigue reliability of structures becomes achievable, consequently resulting in increased efficiency, accuracy, and adaptability of the assessment. This study conducts ice-induced vibration simulations on a 5-MW monopile OWT. Employing orthogonal experimental methods, the study investigates the influence of three critical ice parameters, i.e., ice thickness, ice velocity, and ice crushing strength, on the fatigue damage caused by ice loading on OWTs. Additionally, it explores the effects of ice loading exceedance probability on extreme fatigue damage values of OWTs under combined ice and wind loadings. Furthermore, a surrogate model based on support vector machine (SVM) is developed to effectively capture the intricate mapping relationship between fatigue damage and various random environmental parameters. By conducting a comprehensive evaluation that considers the probabilistic characteristics of ice loading, wind loading, and the S-N curve, this study assesses the fatigue reliability under combined ice and wind. Moreover, this study analyzes the impact of operational duration during winter drift ice on the fatigue reliability index of OWTs. The findings of this study can provide a theoretical basis for devising operational strategies for OWTs operating in icy sea regions. [ABSTRACT FROM AUTHOR]

In order to calculate the fatigue deflection of prestressed concrete (PC) beams, a fatigue variable stiffness distribution (VSD) model based on crack development pattern extracted from fatigue test is presented in this study. Firstly, a linear strain distribution model along the transfer length of concrete and steel bar was established. And the stress analysis of different cross-sections along the transfer length was performed in order to calculate the average moment of inertia in the fatigue crack zone of PC beam. Then, combined with the characterization model of concrete fatigue modulus, a fatigue VSD model for PC beams was established. The model validation shows that the calculated deflections are in good agreement with the measured deflections, and the deviation does not exceed ±10%. Furthermore, the quantitative reverse deduction of fatigue damage based on stiffness index was carried out. And the multi-stage development laws of stiffness degradation and damage evolution under fatigue loading were summarized. Finally, combined with the setting of fatigue failure threshold, the critical point of the PC beam entering the failure state can be reasonably determined. which provides a reference for the assessment of structural service status. The stiffness threshold of the fatigue failure criterion is about 70%, and the damage threshold is about 0.6 for this study. The research results can provide a theoretical basis for the structural performance analysis and failure assessment for PC beams. [ABSTRACT FROM AUTHOR]

Concrete structures are subjected to static and fatigue loads during long-term service, and temperature changes can cause changes in the volume of concrete, leading to stress changes and fatigue damage, which affect the mechanical properties and service life of a structure. In response to the current lack of three-dimensional analysis and the exploration of the mechanical behavior and damage evolution processes of concrete structures under variable temperature environmental conditions, this paper relies on the Fenghuangjing Pump Station project involving the Yangtze River and Huaihe River and constructs a concrete thermo-mechanical-fatigue-damage model based on the power exponent function damage constitutive model. By using multiple coupled simulation calculations to predict the performance of concrete structures; analyzing the stress, deformation, and fatigue damage of structures from construction to operation; comparing measured data; dynamically optimizing inversion to obtain concrete thermal parameters; proposing key control parameters; and warning indicators and thresholds, the research results can provide reference for the long-term safe operation of similar projects. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper evaluates the applicability of Neuber's and equivalent strain energy density (ESED) rules to predict the material response below the root of a sharp U‐notch under variable‐amplitude (VA) loading for crack propagation simulations. The Voce–Chaboche (V‐C) combined hardening constitutive model, coupled with the above‐mentioned approximation rules, is used to resolve the elasto‐plastic response over a range of depths below the notch root. The response at each load reversal is extracted, and the maximum and minimum stress and strain quantities are used to evaluate fatigue damage using the Smith–Watson–Topper parameter. Results from approximation rules are compared to finite element method (FEM) at and below the notch root. Prediction accuracy varied at different points below the root depending on the size of the plastic zone, with predictions made using the original Neuber's and ESED rules being less accurate below the root. Applying stress redistribution correction to the stress field improves its accuracy below the root; however, strain values are significantly amplified as a result. A modified Neuber's rule with stress redistribution and constraint corrections predicts the distribution of the material response and fatigue damage with consistent accuracy. [ABSTRACT FROM AUTHOR]

AbstractThis study presents an innovative numerical approach for predicting pressurized welded pipelines’ cyclic behavior and failure mechanisms under complex loading conditions. Focusing on X52 steel pipelines subjected to internal pressure and three-point bending, we investigate the interplay between structural integrity, weld joint positioning, and boundary conditions. Our methodology integrates advanced finite element analysis with a sophisticated material model capturing isotropic and kinematic hardening. The constitutive behavior is calibrated using the Voce model, accurately representing the material’s cyclic response. We employ the von Mises yield criterion to characterize the multiaxial stress state within the pipeline. A key innovation is our application of the eXtended Finite Element Method (XFEM) coupled with the calibrated hardening model, enabling high-fidelity simulation of crack initiation and propagation. Our model’s predictive capabilities are rigorously validated against experimental data, demonstrating excellent agreement across various loading scenarios. Through comprehensive parametric studies, we elucidate the critical influences of internal pressure, end-fixation conditions, and weld joint locations on the pipeline’s structural response. Force-displacement hysteresis curves reveal complex, nonlinear behaviors significantly impacting fatigue life and failure modes. This research advances the understanding of cyclic plasticity and fatigue in welded pressurized pipelines, providing a robust computational framework for predicting long-term performance. The insights gained have far-reaching implications for enhancing critical energy-transportation infrastructure’s safety, reliability, and longevity, potentially informing future design criteria and regulatory guidelines. [ABSTRACT FROM AUTHOR]

A finite element model, combined with a damage accumulation method, was developed to explore the mesoscale effects of microstructure on the evolution of low-cycle fatigue damage in AA 2024-T3 aluminum alloy. In this model, the maximum shear strain of the slip systems was computed as the damage criterion using crystal plasticity (CP) theory combined with continuum damage mechanics (CDM), the slip strength is related to the evolution of dislocation density, and the nonlinear kinematic hardening rule was used to capture the cyclic response. This constitutive model was capable of quantifying the local fatigue damage in 3D microstructural applied to the Voronoi polycrystals like the AA2024 Al alloy. The results show that grains with high Schmid factors usually suffer more severe damage than those with lower Schmid factors, while grains with lower Schmid factors mainly suffer damage at grain boundaries. The proposed constitutive model demonstrates the ability to capture the fatigue damage evolution of polycrystalline metal. [ABSTRACT FROM AUTHOR]

The fatigue performance of emulsified asphalt mastics directly affects the long-term service performance of emulsified asphalt cold recycled pavement. Fatigue properties of 24 different mastics before and after short-term aging composed by the combination of 3 different fillers and 4 filler-binder ratios (F-B) were evaluated based on the viscoelastic continuum damage (VECD) model. Atomic force microscopy (AFM) was employed to analyze the surface morphology of the mastics and determine the interaction between filler and asphalt. The results show that increasing the F-B or the aging effect reduce the stress–strain withstand capacity of emulsified asphalt mastic, increase its integrity damage rate, and further reduce the fatigue life. Comparing three mastics, limestone mastic with a low F-B exhibits a better fatigue performance. The limestone mastic is more affected by short-term aging, while cement mastic and coal gangue mastic are significantly affected by F-B. Filler types, F-B and aging can obviously change the surface morphology of mastics. The microscopic morphology change of coal gangue mastic with a low F-B is dominated by the dispersing effect of the filler, whereas the microscopic morphology of mastic with a high F-B is dominated by the adsorption effect. [ABSTRACT FROM AUTHOR]

In order to understand the fatigue damage characteristics of anchor windproof cables under strong winds, a comprehensive finite element model of the tower conductor windproof cable system was constructed based on the 110 kV Caoyang line in Turpan. The wind-induced vibration response of windproof cables under strong wind loads was analyzed, based on which a finite element model of cable segments at the outlet of the cable clamp was established. The spatial distribution law of fatigue stress of cable strands was studied, and the fatigue damage of windproof cables in strong wind areas was analyzed. The research results indicate that wind speed has a significant impact on the axial deformation and stress of windproof guy wires. The axial amplitude time history changes of the outer and inner strands of the guy wire are highly consistent. The axial amplitude time history of the outer and inner strands of the guy wire exhibits strong fluctuations under the action of strong winds. Specifically, the higher the wind speed, the greater the stress fluctuation of the inner and outer steel strands of the guy wire. Additionally, the axial stress borne by the inner steel strands of windproof cables is relatively small under wind load, while the stress on the outer steel strands is relatively large. As the wind speed increases, the stress on the windproof cable also increases, and the stress fluctuations of the inner and outer layer strands of the cable become more severe. The fatigue damage of the inner and outer steel strands of the windproof guy wire under strong winds is different, and the fatigue damage of the inner layer of the guy wire is smaller than that of the outer layer. [ABSTRACT FROM AUTHOR]

A three-point bending fatigue experiment was conducted on a component consisting of an I-beam and a welded steel plate. The magnetic leakage signal at the position of the weld was continuously collected during the process of fatigue; the factors influencing magnetic leakage signal were analyzed to explore its change law. Moreover, the characteristic parameters based on magnetic leakage signal were proposed to analyze the fatigue process and fatigue damage of weld. The results indicate that increasing the distance between the magnetic probe and weld will weaken the distribution characteristics of the magnetic leakage signal, then reducing the accuracy of the detection results. The change characteristics of the magnetic characteristic parameter G with the load are analyzed. The change of G presents three development stages with the increase in the load. The loading conditions of the experiment specimen can be determined by observing the change in the value of G. At different fatigue stages, the magnetic leakage signals of the weld show different trends. And the variation law of magnetic eigenvalue K extracted from the magnetic leakage signal can essentially match with the fatigue process of weld, and the magnitude of the eigenvalue can approximately characterize the fatigue damage of the weld. The time node of the state deterioration for the weld can also be approximately judged by the change node of eigenvalue, and the state of weld can be warned in time. Besides, A quantitative relationship between the damage index m and the residual fatigue life R is established. [ABSTRACT FROM AUTHOR]

Lazy wave risers (LWRs) are designed with equidistant buoyancy blocks attached in the lower half of the riser, allowing the riser to take on an arch shape under the buoyancy forces provided by buoyancy blocks. This arch configuration can provide flexibility to the LWR arrangement and effectively isolate the dynamic responses between the offshore floating structure and the riser's touchdown zone (TDZ). Its design and application aim to address the issues of dynamic response and fatigue damage that traditional steel catenary risers (SCRs) face in deep water and complex marine environments. Given that research on the LWRs in the field of ocean engineering is not sufficiently abundant, the structural characteristics, hydrodynamic loads, global responses, fatigue damage assessment, and structural optimization progress of LWRs are systematically reviewed in this paper to provide references for researchers in related fields. Among these topics, the global response of LWRs is the main point of this review. This section details the theoretical analysis and numerical modeling methods employed in the study of LWRs' global response, explores the research advancements in the vortex-induced vibration (VIV) related to LWRs, and discusses corresponding experimental studies. Finally, the installation, transfer, and repair processes of LWRs are investigated. Additionally, the importance of leveraging advanced technologies from other fields and combining them with current advanced algorithms is emphasized in efforts to assess fatigue damage and optimize the structures of LWRs, ultimately achieving complementary advantages. [ABSTRACT FROM AUTHOR]

In order to solve fatigue fracture problem of the transverse stabilizer bar link of a pickup truck, taking the measured load spectrum as support, the fatigue analysis and structural improvement of bar link was carried out based on multi-body dynamics load decomposition method. The load spectrum acquisition test of stabilizer bar link was carried out, and the correlation analysis between sensor signals was conducted, and the validity of the collected signals was verified. Through the kinematics compliance（KC） test, the accuracy of suspension dynamics model was verified, by using virtual iteration method, the accuracy of the vehicle dynamic model is verified by the measured load spectrum signal as excitation. The critical load of bar link was obtained by means of multi-body dynamics load decomposition method, compression rod instability theory method and bench test method respectively, the strength of link was checked and compared with the measured load value, and the accuracy of the three methods was evaluated. The results show that multi-body dynamics load decomposition method can accurately predict the critical load, the bench test method have some errors, and the the compression rod instability theory cannot be directly used for strength check of link. Fatigue simulation and optimization of link were carried out by combining nominal stress method and load spectrum of multi-body dynamics decomposition. The fatigue mileage predicted by simulation is 12 143 km, the relative error value with real life is 14%, which proves validity of simulation method. The structural improvement of the dangerous part of link body port eliminates stress concentration of it, and makes the design life of link meet the service requirements.

The stable protection of the walls of high-temperature geothermal wells is a challenging issue for sustainably exploiting geothermal resources. However, the cement stone filling layer of the cemented portion of the well deteriorates gradually during geothermal mining due to the dry-wet cycles of the saline geothermal water, reducing the service life of the geothermal well. For this, this paper presented five groups of cement stone cylinders with salt contents of 0%, 1%, 6%, and 11%, which were subjected to heating to 300 °C and 1–5 dry-wet cycles. Nuclear magnetic resonance (NMR) and nonmetallic detection were used to test and analyze the porosity and wave velocity. Additionally, the damage evolution induced by dry-wet cycles was captured based on acoustic emission (AE) data. The experimental results indicated that the heating process primarily resulted in mineral and salt crystal expansion, which in turn caused damage. The damage threshold due to the salt content was found to be 6%. The sudden increase in the thermal stress caused by cooling and deterioration of the tensile strength of the cement column were the key factors in the damage during the cooling process. As the number of cycles increased, the accumulated AE energy moved forward and backward, with decreasing and increasing temperature, respectively. The threshold of signal mutation in the heating process is 200 °C, and the accumulated AE energy decreases by 11.7%. When the salt content was 0%, 1%, 6% and 11%, the wave velocity decreased by 19%, 27.3%, 35.5% and 35.9%, respectively. This study also proposed a damage model, which could provide theoretical support for long-term health monitoring and safety protection of geothermal wells.

With the continuous increase of bridge spans, wind-induced vibrations will pose serious problems to structural integrity and serviceability. Among the many vibration sources of long-span bridges, buffeting, which results from impinging turbulence, affects the fatigue life of the bridge structure, and when coupled with other wind-induced loads, might lead to severe structural problems. With climate change, buffeting-induced fatigue might significantly increase due to higher wind speeds and turbulence intensities. Therefore, it is important to assess the cumulative fatigue damage generated by buffeting loads under changing climate scenarios. In this study, the buffeting response of a single-span suspension bridge is investigated in the frequency domain under the Worst-case climate scenario RCP8.5. A simplified bridge model will be used to capture key dynamic and aerodynamic characteristics, with a time-dependent Weibull distribution accounting for nonstationarity in wind speed. The analysis of fatigue damage accumulation under buffeting will involve the rain-flow cycle counting method and the Palmgren–Miner damage law. Three Canadian cities, Montreal, Toronto, and Vancouver, will be included in the study to assess how location, along with the climate scenario, influences the life-cycle buffeting-induced accumulated damage over a 100-year period. [ABSTRACT FROM AUTHOR]

Aviation aircraft will be subjected to a large number of complex random vibration loads during service， and its structure is prone to vibration fatigue，which leads to damage or even failure，which can cause serious losses. The stress intensity factor（SIF）solution method for cracked beams under random vibration loading is investigated，and a time-domain method based on Hudson's theory is proposed to estimate the vibration fatigue crack growth life by combining with the Paris formula. The theoretical analysis and vibration fatigue test are conducted on a typical cantilever beam as an object. The results show that the life prediction results of the proposed time-domain method based on the Hudson's theory is better than that of the experimental estimation results，which can verify that the method can effectively describe the random vibration crack growth behavior.