An approach based on continuum damage mechanics to fatigue life prediction for structures is proposed. A new fatigue damage evolution equation is developed, in which the pa- rameters are obtained in a simple way with ...An approach based on continuum damage mechanics to fatigue life prediction for structures is proposed. A new fatigue damage evolution equation is developed, in which the pa- rameters are obtained in a simple way with reference to the experimental results of fatigue tests on standard specimens. With the utilization of APDL language on the ANSYS platform, a finite element implementation is presented to perform coupling operation on damage evolution of mate- rial and stress redistribution. The fatigue lives of some notched specimens and a Pitch-change-link are predicted by using the above approach. The calculated results are validated with experimental data.展开更多
The fatigue life prediction for components is a difficult task since many factors can affect the final fatigue life. Based on the damage evolution equation of Lemaitre and Desmorat, a revised two-scale damage evolutio...The fatigue life prediction for components is a difficult task since many factors can affect the final fatigue life. Based on the damage evolution equation of Lemaitre and Desmorat, a revised two-scale damage evolution equation for high cycle fatigue is presented according to the experimental data, in which factors such as the stress amplitude and mean stress are taken into account. Then, a method is proposed to obtain the material parameters of the revised equation from the present fatigue experimental data. Finally, with the utilization of the ANSYS parametric design language （APDL） on the ANSYS platform, the coupling effect between the fatigue damage of materials and the stress distribution in structures is taken into account, and the fatigue life of specimens is predicted. The outcome shows that the numerical prediction is in accord with the experimental results, indicating that the revised two-scale damage evolution model can be well applied for the high cycle fatigue life prediction under uniaxial loading.展开更多
This paper introduces a stiffness reduction based model developed by the authors to characterize accumulative fatigue damage in unidirectional plies and(0/θ/0)composite laminates in fiber reinforced polymer(FRP)compo...This paper introduces a stiffness reduction based model developed by the authors to characterize accumulative fatigue damage in unidirectional plies and(0/θ/0)composite laminates in fiber reinforced polymer(FRP)composite laminates.The proposed damage detection model is developed based on a damage evolution mechanism,including crack initiation and crack damage progress in matrix,matrix-fiber interface and fibers.Research result demonstrates that the corresponding stiffness of unidirectional composite laminates is reduced as the number of loading cycles progresses.First,three common models in literatures are presented and compared.Tensile viscosity,Young’s modulus and ultimate tensile stress of composites are incorporated as key factors in this model and are modified in accordance with temperature.Four types of FRP composite property parameters,including Carbon Fiber Reinforced Polymer(CFRP),Aramid Fiber Reinforced Polymer(AFRP),Glass Fiber Reinforced Polymer(GFRP),and Basalt Fiber Reinforced Polymer(BFRP),are considered in this research,and a comparative parameter study of FRP unidirectional composite laminates with different off-angle plies using control variate method are discussed.It is concluded that the relationship between the drop in stiffness and the number of cycles also shows three different regions,following the mechanism of damage of FRP composites and the matrix is the dominant factor determined by temperature,while fiber strength is the dominant factor that determine the reliability of composite.展开更多
Fatigue failure of mechanical part is treated as a random event.the fatigue reliablility problem can be solved through researching the random event.A new definition δb that measures fatigue damage quantity in a cycle...Fatigue failure of mechanical part is treated as a random event.the fatigue reliablility problem can be solved through researching the random event.A new definition δb that measures fatigue damage quantity in a cycle under cyclic stress is put forward. According to δ.the paper presents two new definitions K and D is fatigue damage strength.D is overall fatigue damage quantity.Using K and D to describe the fatigue failure of the parts,the paper puts forward a new fatigue cumulative damage probabilistic model of the mechanical parts.The model can be used to solve reliability fatigue problem.展开更多
Cold regions often feature complex geological environments where various physical phenomena interact,with a particularly notable thermo-hydro-mechanical(THM)coupling.In this study,fully coupled THM cyclic tests were c...Cold regions often feature complex geological environments where various physical phenomena interact,with a particularly notable thermo-hydro-mechanical(THM)coupling.In this study,fully coupled THM cyclic tests were conducted,followed by fatigue tests,to explore how THM treatment influences the fatigue properties of damaged sandstone.Experimental results indicate that rock fatigue deformation,damage evolution,and failure characteristics are highly sensitive to initial damage caused by coupled THM treatment.Rocks subjected to multiple THM cycles exhibit lower initial irreversible strain,shorter fatigue life,lower critical total dissipated energy,and higher irreversible strain increments,indicating accelerated deterioration.After THM coupling,rock fatigue failure shows complex crack networks,with macroscopic failure modes shifting from shear to tensile failure.Polarized microscopy and acoustic emission analyses reveal that this transition stems from micro-scale transgranular to intergranular fractures.We introduced a fractional order-based damage fatigue model to quantitatively describe the rock viscoelastic parameters after different initial damage treatments.Rock viscoelastic-plastic parameters decrease with increasing coupled THM cycles.Finally,we discussed the feasibility of applying these results to the long-term stability analysis of rock slopes.This study provides unique insights and modeling tools from fully coupled THM experiments to understand the rock fatigue characteristics,offering potential applications for slope stability assessment.展开更多
The considerable uncertainty in mechanical properties of composite bolted joints not only prevents advanced composite materials from efficient applications,but also threatens the safety and reliability of the aircraft...The considerable uncertainty in mechanical properties of composite bolted joints not only prevents advanced composite materials from efficient applications,but also threatens the safety and reliability of the aircraft structures.In this paper,the uncertainty in bearing fatigue properties of a CFRP double-lap,single-bolt joint was evaluated by combing a Progressive Fatigue Damage Model(PFDM)with the interval analysis method.In the PFDM,a residualstrain-based gradual material degradation model and a strain-based fatigue failure criterion were combined with a micromechanics-based sudden material degradation model to predict fatigue properties of the joint.Based on the interval analysis,the key uncertain parameters,which were firstly picked out from eighteen structural parameters of the joint,were described by estimated intervals,and the envelope cases were determined to estimate the lower and upper bounds of fatigue properties of the joint.The predicted results have the same tendency with the experimental results in literatures,which indicates that the PFDM combined with the interval analysis shows potential in efficiently evaluating the fatigue reliability of the complex bolted joints with an adequate accuracy.展开更多
基金supported by the National Natural Science Foundation of China(No.11002010)
文摘An approach based on continuum damage mechanics to fatigue life prediction for structures is proposed. A new fatigue damage evolution equation is developed, in which the pa- rameters are obtained in a simple way with reference to the experimental results of fatigue tests on standard specimens. With the utilization of APDL language on the ANSYS platform, a finite element implementation is presented to perform coupling operation on damage evolution of mate- rial and stress redistribution. The fatigue lives of some notched specimens and a Pitch-change-link are predicted by using the above approach. The calculated results are validated with experimental data.
文摘The fatigue life prediction for components is a difficult task since many factors can affect the final fatigue life. Based on the damage evolution equation of Lemaitre and Desmorat, a revised two-scale damage evolution equation for high cycle fatigue is presented according to the experimental data, in which factors such as the stress amplitude and mean stress are taken into account. Then, a method is proposed to obtain the material parameters of the revised equation from the present fatigue experimental data. Finally, with the utilization of the ANSYS parametric design language （APDL） on the ANSYS platform, the coupling effect between the fatigue damage of materials and the stress distribution in structures is taken into account, and the fatigue life of specimens is predicted. The outcome shows that the numerical prediction is in accord with the experimental results, indicating that the revised two-scale damage evolution model can be well applied for the high cycle fatigue life prediction under uniaxial loading.
文摘This paper introduces a stiffness reduction based model developed by the authors to characterize accumulative fatigue damage in unidirectional plies and(0/θ/0)composite laminates in fiber reinforced polymer(FRP)composite laminates.The proposed damage detection model is developed based on a damage evolution mechanism,including crack initiation and crack damage progress in matrix,matrix-fiber interface and fibers.Research result demonstrates that the corresponding stiffness of unidirectional composite laminates is reduced as the number of loading cycles progresses.First,three common models in literatures are presented and compared.Tensile viscosity,Young’s modulus and ultimate tensile stress of composites are incorporated as key factors in this model and are modified in accordance with temperature.Four types of FRP composite property parameters,including Carbon Fiber Reinforced Polymer(CFRP),Aramid Fiber Reinforced Polymer(AFRP),Glass Fiber Reinforced Polymer(GFRP),and Basalt Fiber Reinforced Polymer(BFRP),are considered in this research,and a comparative parameter study of FRP unidirectional composite laminates with different off-angle plies using control variate method are discussed.It is concluded that the relationship between the drop in stiffness and the number of cycles also shows three different regions,following the mechanism of damage of FRP composites and the matrix is the dominant factor determined by temperature,while fiber strength is the dominant factor that determine the reliability of composite.
文摘Fatigue failure of mechanical part is treated as a random event.the fatigue reliablility problem can be solved through researching the random event.A new definition δb that measures fatigue damage quantity in a cycle under cyclic stress is put forward. According to δ.the paper presents two new definitions K and D is fatigue damage strength.D is overall fatigue damage quantity.Using K and D to describe the fatigue failure of the parts,the paper puts forward a new fatigue cumulative damage probabilistic model of the mechanical parts.The model can be used to solve reliability fatigue problem.
基金supported by the National Natural Science Foundation of China(Grant No.42372326)supported by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2023Z015)supported by the Sichuan Science and Technology Program(Grant No.2024YFFK0416).
文摘Cold regions often feature complex geological environments where various physical phenomena interact,with a particularly notable thermo-hydro-mechanical(THM)coupling.In this study,fully coupled THM cyclic tests were conducted,followed by fatigue tests,to explore how THM treatment influences the fatigue properties of damaged sandstone.Experimental results indicate that rock fatigue deformation,damage evolution,and failure characteristics are highly sensitive to initial damage caused by coupled THM treatment.Rocks subjected to multiple THM cycles exhibit lower initial irreversible strain,shorter fatigue life,lower critical total dissipated energy,and higher irreversible strain increments,indicating accelerated deterioration.After THM coupling,rock fatigue failure shows complex crack networks,with macroscopic failure modes shifting from shear to tensile failure.Polarized microscopy and acoustic emission analyses reveal that this transition stems from micro-scale transgranular to intergranular fractures.We introduced a fractional order-based damage fatigue model to quantitatively describe the rock viscoelastic parameters after different initial damage treatments.Rock viscoelastic-plastic parameters decrease with increasing coupled THM cycles.Finally,we discussed the feasibility of applying these results to the long-term stability analysis of rock slopes.This study provides unique insights and modeling tools from fully coupled THM experiments to understand the rock fatigue characteristics,offering potential applications for slope stability assessment.
基金supported by the National Natural Science Foundation of China(Nos.U1864208,11772028,11872131 and 11702012)。
文摘The considerable uncertainty in mechanical properties of composite bolted joints not only prevents advanced composite materials from efficient applications,but also threatens the safety and reliability of the aircraft structures.In this paper,the uncertainty in bearing fatigue properties of a CFRP double-lap,single-bolt joint was evaluated by combing a Progressive Fatigue Damage Model(PFDM)with the interval analysis method.In the PFDM,a residualstrain-based gradual material degradation model and a strain-based fatigue failure criterion were combined with a micromechanics-based sudden material degradation model to predict fatigue properties of the joint.Based on the interval analysis,the key uncertain parameters,which were firstly picked out from eighteen structural parameters of the joint,were described by estimated intervals,and the envelope cases were determined to estimate the lower and upper bounds of fatigue properties of the joint.The predicted results have the same tendency with the experimental results in literatures,which indicates that the PFDM combined with the interval analysis shows potential in efficiently evaluating the fatigue reliability of the complex bolted joints with an adequate accuracy.
