By means of analysis technique such as scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),and transmission electron microscopy(TEM),deep metallurgy failure analysis for an early fractur...By means of analysis technique such as scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),and transmission electron microscopy(TEM),deep metallurgy failure analysis for an early fracture engine intake valve made of the martensite material of 85Cr18Mo2V was performed through macroscopical and microcosmic as well as chemical composition angles.According to the result of SEM,this valve belonged to fatigue fracture.The crack sources of dense micro-holes near the surface of intake valve and SiO2 impurity are the direct reasons to cause the valve failure.The EDS analysis for the fatigue source region approved that superfluous Si,O and Al impurity existed.The TEM observation of the slice cut from the region closing to the fracture surface showed that deep areas near the surface of valve were oxidized severely.The material structure got brittle due to the generation of Fe3O4.Cracks will be produced in these oxidation areas under high cycle fatigue loading.Consequently,the synthetical action of various factors finally caused the fracture of valve.展开更多
As the outfield load spectrum is so complicated that it cannot be used directly for test study in laboratory.This paper presents a method to determine load spectrum for high and low cycle combined fatigue of turbine m...As the outfield load spectrum is so complicated that it cannot be used directly for test study in laboratory.This paper presents a method to determine load spectrum for high and low cycle combined fatigue of turbine mortise at elevated temperature through experimental and numerical method.First of all,the low cycle load spectrum with duration time is determined through cumulative damage rule.The rain flow counting method is applied to obtain main cycles and sub cycles,and then the stress cycle is converted into pulsation cycle(stress ratio=0)based on the S-N curve and the Goodman curve;Secondly,three groups of different amplitudes tests are established to determine the high cycle amplitude.Finally,another three groups of the high-low combined cycle fatigue(HLCCF)tests for turbine mortise of a certain type engine are carried out.The results show that the macro and micro failure modes are identical with outfield's,which verifies the accuracy of the conversion method.展开更多
基金NSFC(50975285,50735006)Advanced Maintenance Research Project(9140A270304090C8501)
文摘By means of analysis technique such as scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),and transmission electron microscopy(TEM),deep metallurgy failure analysis for an early fracture engine intake valve made of the martensite material of 85Cr18Mo2V was performed through macroscopical and microcosmic as well as chemical composition angles.According to the result of SEM,this valve belonged to fatigue fracture.The crack sources of dense micro-holes near the surface of intake valve and SiO2 impurity are the direct reasons to cause the valve failure.The EDS analysis for the fatigue source region approved that superfluous Si,O and Al impurity existed.The TEM observation of the slice cut from the region closing to the fracture surface showed that deep areas near the surface of valve were oxidized severely.The material structure got brittle due to the generation of Fe3O4.Cracks will be produced in these oxidation areas under high cycle fatigue loading.Consequently,the synthetical action of various factors finally caused the fracture of valve.
基金This work is supported by National Natural Science Foundation of China(51305012)Doctoral Fund of Ministry of Education of China(20111102120011)National Natural Science Foundation of China(51375031).The writers are grateful。
文摘As the outfield load spectrum is so complicated that it cannot be used directly for test study in laboratory.This paper presents a method to determine load spectrum for high and low cycle combined fatigue of turbine mortise at elevated temperature through experimental and numerical method.First of all,the low cycle load spectrum with duration time is determined through cumulative damage rule.The rain flow counting method is applied to obtain main cycles and sub cycles,and then the stress cycle is converted into pulsation cycle(stress ratio=0)based on the S-N curve and the Goodman curve;Secondly,three groups of different amplitudes tests are established to determine the high cycle amplitude.Finally,another three groups of the high-low combined cycle fatigue(HLCCF)tests for turbine mortise of a certain type engine are carried out.The results show that the macro and micro failure modes are identical with outfield's,which verifies the accuracy of the conversion method.
