In this paper,the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100℃/130 MPa.The alloy exhibited typical creep curve including primary,ste...In this paper,the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100℃/130 MPa.The alloy exhibited typical creep curve including primary,steady,and tertiary three creep stages.The microstructural evolution at different stages of the creep were analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that theγ′phases transform into rafted structure at the early stage of the steady creep and keep stable during the steady creep stage.As the creep goes on,the rafted structure further coarsens and the topological inversion occurs.In addition,at the primary creep,the dislocations mainly move in theγmatrix and pile up in theγ/γ′interface since the matrix channels widen slightly.The formation of the regular interfacial dislocation networks occurs at the early stage of the steady creep.Under the low stress,the dominated deformation mechanism during steady creep stage is the climbing of the〈010〉type edge dislocation.Furthermore,the effect of the deformation mechanism on creep property was discussed in detail.展开更多
The physics phenomena of copper and stainless steel in the process of forming friction welding joint are recorded and observed by the interrupted test method.The test shows that the butt friction welding process of co...The physics phenomena of copper and stainless steel in the process of forming friction welding joint are recorded and observed by the interrupted test method.The test shows that the butt friction welding process of copper and stainless steel bar can be divided into three stages approximately: the adhesion at the beginning friction stage, the friction inside the copper and the plastic ring expansion, and the friction on the bound surface of copper-stainless steel and in stainless steel. During the process,the friction surface was transformed twice.展开更多
The current interruption test based on an LC resonance circuit for hybrid DC circuit breakers(HVDC CBs)is widely employed to characterize the current interruption capability of CBs.In order to ensure a high-fidelity r...The current interruption test based on an LC resonance circuit for hybrid DC circuit breakers(HVDC CBs)is widely employed to characterize the current interruption capability of CBs.In order to ensure a high-fidelity replica of the fault current in a high voltage application,this paper first proposes an equivalent model of the test circuit,where not only parasitic resistances but also the threshold voltages and on-state resistances of various semiconductor devices are considered.Moreover,the analytical formula of the test current is derived by including the working principle of the HVDC CB.Secondly,the parameter extraction method,which combines finite element analysis and measurements by an impedance analyzer,is given in this paper.The extracted result implies that,in current interruption transients,equivalent resistances of 500 kV CB are as large as 535 mS,which have a significant influence on current waveforms.Thirdly,the 34 kV/25 kA current interruption test for the 500 kV CB is conducted.The measured results are proved to be consistent with the analytical results obtained from the proposed model,and the relative error is less than 2%.展开更多
基金This study was financially supported by the National Natural Science Foundation of China(No.51471014).
文摘In this paper,the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100℃/130 MPa.The alloy exhibited typical creep curve including primary,steady,and tertiary three creep stages.The microstructural evolution at different stages of the creep were analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that theγ′phases transform into rafted structure at the early stage of the steady creep and keep stable during the steady creep stage.As the creep goes on,the rafted structure further coarsens and the topological inversion occurs.In addition,at the primary creep,the dislocations mainly move in theγmatrix and pile up in theγ/γ′interface since the matrix channels widen slightly.The formation of the regular interfacial dislocation networks occurs at the early stage of the steady creep.Under the low stress,the dominated deformation mechanism during steady creep stage is the climbing of the〈010〉type edge dislocation.Furthermore,the effect of the deformation mechanism on creep property was discussed in detail.
文摘The physics phenomena of copper and stainless steel in the process of forming friction welding joint are recorded and observed by the interrupted test method.The test shows that the butt friction welding process of copper and stainless steel bar can be divided into three stages approximately: the adhesion at the beginning friction stage, the friction inside the copper and the plastic ring expansion, and the friction on the bound surface of copper-stainless steel and in stainless steel. During the process,the friction surface was transformed twice.
基金supported by Science and Technology Project of State Grid Corporation of China(No.520201190095).
文摘The current interruption test based on an LC resonance circuit for hybrid DC circuit breakers(HVDC CBs)is widely employed to characterize the current interruption capability of CBs.In order to ensure a high-fidelity replica of the fault current in a high voltage application,this paper first proposes an equivalent model of the test circuit,where not only parasitic resistances but also the threshold voltages and on-state resistances of various semiconductor devices are considered.Moreover,the analytical formula of the test current is derived by including the working principle of the HVDC CB.Secondly,the parameter extraction method,which combines finite element analysis and measurements by an impedance analyzer,is given in this paper.The extracted result implies that,in current interruption transients,equivalent resistances of 500 kV CB are as large as 535 mS,which have a significant influence on current waveforms.Thirdly,the 34 kV/25 kA current interruption test for the 500 kV CB is conducted.The measured results are proved to be consistent with the analytical results obtained from the proposed model,and the relative error is less than 2%.
