Fatigue testing was performed using a kind of triangular shaped specimen to obtain the characteristics of numerical density evolution for short cracks at the primary stage of fatigue damage. The material concerned is ...Fatigue testing was performed using a kind of triangular shaped specimen to obtain the characteristics of numerical density evolution for short cracks at the primary stage of fatigue damage. The material concerned is a structural alloy steel. The experimental results show that the numerical density of short cracks reaches the maximum value when crack length is slightly less than the average grain diameter, indicating grain boundary is the main barrier for short crack extension. Based on the experimental observations and related theory, the expressions for growth velocity and nucleation rate of short cracks have been proposed. With the solution to phase space conservation equation, the theoretical results of numerical density evolution for short cracks were obtained, which were in agreement with our experimental measurements.展开更多
Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and d...Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.展开更多
Epoxy asphalt is widely used in steel bridge deck pavements,airport pavements,and high-grade roadways due to its superior performance,yet its fatigue damage evolution mechanisms remain insufficiently studied.This stud...Epoxy asphalt is widely used in steel bridge deck pavements,airport pavements,and high-grade roadways due to its superior performance,yet its fatigue damage evolution mechanisms remain insufficiently studied.This study investigated the fatigue performance of epoxy asphalt binder(EAB)and epoxy asphalt mixture(EAM)through linear amplitude sweep tests and four-point bending beam fatigue experiments.By analyzing fatigue parameters across varying epoxy contents and strain levels,predictive correlation models were developed between EAB and EAM fatigue performance.Furthermore,the finite element method(FEM)was employed to compare the fatigue behavior of conventional asphalt and epoxy asphalt pavements.Results demonstrate that the EAM enters a stable fatigue damage accumulation phase when the stiffness modulus decays to 75%of its initial value.Both EAB and EAM exhibit extended fatigue life with increased epoxy content or reduced strain levels,accompanied by enhanced cumulative dissipated energy(CDE)and reduced energy dissipation rates in EAM.Notably,CDE and plateau values exhibit robust logarithmic-linear correlations with EAM fatigue life(R^(2)=0.99 and R^(2)=0.97,respectively),independent of variations in strain or epoxy content.Sensitivity analysis reveals CDE as the most epoxy-content-sensitive parameter,suggesting its potential as a key control factor in fatigue design.The proposed EAB-EAM correlation model further enables accurate prediction of mixture fatigue life based on binder properties.FEM simulations demonstrate that EAM pavement structures have significantly lower tensile strain and better fatigue resistance compared to conventional asphalt mixtures,translating to reduced maintenance frequency and lower lifecycle carbon emissions.The findings of this research enhance the understanding of epoxy asphalt fatigue mechanisms while offering practical guidance for optimizing pavement design.展开更多
Fatigue failure phenomena of the concrete structures under long-term low amplitude loading have attractedmore attention.Some structures,such as wind power towers,offshore platforms,and high-speed railways,may resist m...Fatigue failure phenomena of the concrete structures under long-term low amplitude loading have attractedmore attention.Some structures,such as wind power towers,offshore platforms,and high-speed railways,may resist millions of cycles loading during their intended lives.Over the past century,analytical methods for concrete fatigue are emerging.It is concluded that models for the concrete fatigue calculation can fall into four categories:the empirical model relying on fatigue tests,fatigue crack growth model in fracture mechanics,fatigue damage evolution model based on damage mechanics and advanced machine learning model.In this paper,a detailed review of fatigue computing methodology for concrete is presented,and the characteristics of different types of fatigue models have been stated and discussed.展开更多
基金The project supported by the National Natural Science Foundation of China the Chinese Academy of Sciences.
文摘Fatigue testing was performed using a kind of triangular shaped specimen to obtain the characteristics of numerical density evolution for short cracks at the primary stage of fatigue damage. The material concerned is a structural alloy steel. The experimental results show that the numerical density of short cracks reaches the maximum value when crack length is slightly less than the average grain diameter, indicating grain boundary is the main barrier for short crack extension. Based on the experimental observations and related theory, the expressions for growth velocity and nucleation rate of short cracks have been proposed. With the solution to phase space conservation equation, the theoretical results of numerical density evolution for short cracks were obtained, which were in agreement with our experimental measurements.
文摘Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.
基金supported by the Southeast University(SEU)Innovation Capability Enhancement Plan for Doctoral Students(Grant No.CXJH_SEU 24)the Major Science and Technology Project of Nanjing(Grant No.202209012)the Carbon Peak and Carbon Neutrality Science and Technology Innovation Special Funds of Jiangsu Province(Grant No.BE2022615).
文摘Epoxy asphalt is widely used in steel bridge deck pavements,airport pavements,and high-grade roadways due to its superior performance,yet its fatigue damage evolution mechanisms remain insufficiently studied.This study investigated the fatigue performance of epoxy asphalt binder(EAB)and epoxy asphalt mixture(EAM)through linear amplitude sweep tests and four-point bending beam fatigue experiments.By analyzing fatigue parameters across varying epoxy contents and strain levels,predictive correlation models were developed between EAB and EAM fatigue performance.Furthermore,the finite element method(FEM)was employed to compare the fatigue behavior of conventional asphalt and epoxy asphalt pavements.Results demonstrate that the EAM enters a stable fatigue damage accumulation phase when the stiffness modulus decays to 75%of its initial value.Both EAB and EAM exhibit extended fatigue life with increased epoxy content or reduced strain levels,accompanied by enhanced cumulative dissipated energy(CDE)and reduced energy dissipation rates in EAM.Notably,CDE and plateau values exhibit robust logarithmic-linear correlations with EAM fatigue life(R^(2)=0.99 and R^(2)=0.97,respectively),independent of variations in strain or epoxy content.Sensitivity analysis reveals CDE as the most epoxy-content-sensitive parameter,suggesting its potential as a key control factor in fatigue design.The proposed EAB-EAM correlation model further enables accurate prediction of mixture fatigue life based on binder properties.FEM simulations demonstrate that EAM pavement structures have significantly lower tensile strain and better fatigue resistance compared to conventional asphalt mixtures,translating to reduced maintenance frequency and lower lifecycle carbon emissions.The findings of this research enhance the understanding of epoxy asphalt fatigue mechanisms while offering practical guidance for optimizing pavement design.
基金supported by the National Natural Science Foundation of China(Grant Nos.52078361 and 51678439)Innovation Program of Shanghai Municipal Education Commission(Grant No.2017-01-07-00-07-E00006).
文摘Fatigue failure phenomena of the concrete structures under long-term low amplitude loading have attractedmore attention.Some structures,such as wind power towers,offshore platforms,and high-speed railways,may resist millions of cycles loading during their intended lives.Over the past century,analytical methods for concrete fatigue are emerging.It is concluded that models for the concrete fatigue calculation can fall into four categories:the empirical model relying on fatigue tests,fatigue crack growth model in fracture mechanics,fatigue damage evolution model based on damage mechanics and advanced machine learning model.In this paper,a detailed review of fatigue computing methodology for concrete is presented,and the characteristics of different types of fatigue models have been stated and discussed.
