The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron m...The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The results show that the alloy exhibits higher fatigue crack propagation(FCP) resistance in T3 condition than in T6 condition,the fatigue life is increased by 54% and the fatigue crack growth rate(FCGR) decreases significantly.The fatigue fractures of the alloy in T3 and T6 conditions are transgranular.But in T3 condition,secondary cracks occur and fatigue striations are not clear.In T6 condition,ductile fatigue striations are observed.The effect of aging conditions on fatigue behaviors is explained in terms of the slip planarity of dislocations and the cyclic slip reversibility.展开更多
Fatigue is usually the cause for the cracks identified at bridge elements in service. With an increase in the introduction of corrugated steel web girders in recent highway bridge construction, the understanding of th...Fatigue is usually the cause for the cracks identified at bridge elements in service. With an increase in the introduction of corrugated steel web girders in recent highway bridge construction, the understanding of the fatigue behaviour of welded details in such structures becomes an important issue for the design. The typical welded details were represented as welded joints assembled by longitudinal corrugated plates. All the experiments were performed under fatigue loading using a servo-control testing machine. The test results from the failure mode observation with the aid of infrared thermo-graph technology show that the failure manner of these welded joints is comparable to that of the corrugated steel web beams reported previously. It is indicated from the stiffness degradation analysis that the welded joints with larger corrugation angle have higher stiffness and greater stiffness degradation in the notable stiffness degradation range. It is shown from the test S-N relations based on the free regression and forced regression analyses that there is a good linear dependence between lg(N) and lg(ΔS). It is also demonstrated that the proposed fracture mechanics analytical model is able to give a prediction slightly lower but on the safe side for the mean stresses at 2 million cycles of the test welded joints.展开更多
基金Project(2005CB623705) supported by the National Basic Research Program of China
文摘The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The results show that the alloy exhibits higher fatigue crack propagation(FCP) resistance in T3 condition than in T6 condition,the fatigue life is increased by 54% and the fatigue crack growth rate(FCGR) decreases significantly.The fatigue fractures of the alloy in T3 and T6 conditions are transgranular.But in T3 condition,secondary cracks occur and fatigue striations are not clear.In T6 condition,ductile fatigue striations are observed.The effect of aging conditions on fatigue behaviors is explained in terms of the slip planarity of dislocations and the cyclic slip reversibility.
基金Projects(51308363,11327801)supported by the National Natural Science Foundation of ChinaProject(2013-1792-9-4)supported by the Scientific Research Foundation for the Returned Overseas Chinese ScholarsProject(YJ201307)supported by the Start-up Research Fund for Introduced Talents of Sichuan University,China
文摘Fatigue is usually the cause for the cracks identified at bridge elements in service. With an increase in the introduction of corrugated steel web girders in recent highway bridge construction, the understanding of the fatigue behaviour of welded details in such structures becomes an important issue for the design. The typical welded details were represented as welded joints assembled by longitudinal corrugated plates. All the experiments were performed under fatigue loading using a servo-control testing machine. The test results from the failure mode observation with the aid of infrared thermo-graph technology show that the failure manner of these welded joints is comparable to that of the corrugated steel web beams reported previously. It is indicated from the stiffness degradation analysis that the welded joints with larger corrugation angle have higher stiffness and greater stiffness degradation in the notable stiffness degradation range. It is shown from the test S-N relations based on the free regression and forced regression analyses that there is a good linear dependence between lg(N) and lg(ΔS). It is also demonstrated that the proposed fracture mechanics analytical model is able to give a prediction slightly lower but on the safe side for the mean stresses at 2 million cycles of the test welded joints.
