Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer ...Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.展开更多
Calotropis procera(Aiton)W.T.Aiton,belonging to the family Apocynaceae,is C3 evergreen plant species in arid and semi-arid areas of the Punjab Province,Pakistan.It grows in a variety of habitats like salt affected and...Calotropis procera(Aiton)W.T.Aiton,belonging to the family Apocynaceae,is C3 evergreen plant species in arid and semi-arid areas of the Punjab Province,Pakistan.It grows in a variety of habitats like salt affected and waterlogged area,desert/semi-desert,roadside,wasteland,graveyard,forest,crop field,coastline,and river/canal bank.A total of 12 populations growing in different ecological regions were sampled to evaluate their growth,physio-biochemical,and anatomical responses to specific environmental condition.Population adapted to desert/semi-desert showed vigorous growth(plant height,shoot length,and number of leaves),enhanced photosynthetic level(chlorophyll a,chlorophyll b,carotenoids,and total chlorophyll),and apparent anatomical modifications such as increased stem radius,cuticle thickness,storage parenchyma tissues(cortex and pith),and vascular bundles in stems,while the maximum of midrib and lamina thickness,epidermal cells,cuticle thickness,cortical proportion,abaxial stomatal density,and its area in leaves.There was high plasticity in structural and functional features of these populations,which enable them to survive and tolerate under such hot and dry desert environment.Population of saline areas exhibited very critical modifications to sustain under salt prone environment.At physiological level,it possesses the maximum amount of organic osmolytes(glycine betaine and proline)and antioxidants(superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)),while at anatomical level,it showed intensive sclerification,large phloem region(inner and outer),pith parenchyma cells,and metaxylem vessels in stems and leaves.The population of dry mountains showed very distinctive features,such as increased shoot ionic contents(K+and Ca2+),collenchyma and sclerenchyma thickness in stems,trichomes size,and numerous small stomata on abaxial surface of leaves.It is concluded that no definite or precise single character can be taken as a yardstick for adjudging the biomass production in this rubber bush weed population.展开更多
The failure rate of crankpin bearing bush of diesel engine under complex working conditions such as high temperature,dynamic load and variable speed is high.After serious wear,it is easy to deteriorate the stress stat...The failure rate of crankpin bearing bush of diesel engine under complex working conditions such as high temperature,dynamic load and variable speed is high.After serious wear,it is easy to deteriorate the stress state of connecting rod body and connecting rod bolt,resulting in serious accidents such as connecting rod fracture and body damage.Based on the mixed lubrication characteristics of connecting rod big endbearing shell of diesel engine under high explosion pressure impact load,an improved mixed lubrication mechanism model is established,which considers the influence of viscoelastic micro deformation of bearing bush material,integrates the full film lubrication model and dry friction model,couples dynamic equation of connecting rod.Then the actual lubrication state of big end bearing shell is simulated numerically.Further,the correctness of the theoretical research results is verified by fault simulation experiments.The results show that the high-frequency impact signal with fixed angle domain characteristics will be generated after the serious wear of bearing bush and the deterioration of lubrication state.The fault feature capture and alarm can be realized through the condition monitoring system,which can be applied to the fault monitoring of connecting rod bearing bush of diesel engine in the future.展开更多
The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carr...The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carried out.Based on the experimental data,a ternary quadratic regression equation was established by orthogonal experiment.The Ramberg-Osgood constitutive model of tin-bronze connecting rod bushing was obtained.Referred to the constitutive relation of macroscopic incremental,the incremental elastoplastic constitutive relation of spinning parts was deduced based on the Mises yield criterion and kinematic hardening model.The results can be applied to the elastoplastic analysis in finite element numerical simulation.展开更多
基金National Natural Science Foundation of China under Grant No.51878508。
文摘Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.
文摘Calotropis procera(Aiton)W.T.Aiton,belonging to the family Apocynaceae,is C3 evergreen plant species in arid and semi-arid areas of the Punjab Province,Pakistan.It grows in a variety of habitats like salt affected and waterlogged area,desert/semi-desert,roadside,wasteland,graveyard,forest,crop field,coastline,and river/canal bank.A total of 12 populations growing in different ecological regions were sampled to evaluate their growth,physio-biochemical,and anatomical responses to specific environmental condition.Population adapted to desert/semi-desert showed vigorous growth(plant height,shoot length,and number of leaves),enhanced photosynthetic level(chlorophyll a,chlorophyll b,carotenoids,and total chlorophyll),and apparent anatomical modifications such as increased stem radius,cuticle thickness,storage parenchyma tissues(cortex and pith),and vascular bundles in stems,while the maximum of midrib and lamina thickness,epidermal cells,cuticle thickness,cortical proportion,abaxial stomatal density,and its area in leaves.There was high plasticity in structural and functional features of these populations,which enable them to survive and tolerate under such hot and dry desert environment.Population of saline areas exhibited very critical modifications to sustain under salt prone environment.At physiological level,it possesses the maximum amount of organic osmolytes(glycine betaine and proline)and antioxidants(superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)),while at anatomical level,it showed intensive sclerification,large phloem region(inner and outer),pith parenchyma cells,and metaxylem vessels in stems and leaves.The population of dry mountains showed very distinctive features,such as increased shoot ionic contents(K+and Ca2+),collenchyma and sclerenchyma thickness in stems,trichomes size,and numerous small stomata on abaxial surface of leaves.It is concluded that no definite or precise single character can be taken as a yardstick for adjudging the biomass production in this rubber bush weed population.
基金Supported by the National Natural Science Foundation of China(No.52101343)the Aeronautical Science Foundation(No.201834S9002).
文摘The failure rate of crankpin bearing bush of diesel engine under complex working conditions such as high temperature,dynamic load and variable speed is high.After serious wear,it is easy to deteriorate the stress state of connecting rod body and connecting rod bolt,resulting in serious accidents such as connecting rod fracture and body damage.Based on the mixed lubrication characteristics of connecting rod big endbearing shell of diesel engine under high explosion pressure impact load,an improved mixed lubrication mechanism model is established,which considers the influence of viscoelastic micro deformation of bearing bush material,integrates the full film lubrication model and dry friction model,couples dynamic equation of connecting rod.Then the actual lubrication state of big end bearing shell is simulated numerically.Further,the correctness of the theoretical research results is verified by fault simulation experiments.The results show that the high-frequency impact signal with fixed angle domain characteristics will be generated after the serious wear of bearing bush and the deterioration of lubrication state.The fault feature capture and alarm can be realized through the condition monitoring system,which can be applied to the fault monitoring of connecting rod bearing bush of diesel engine in the future.
基金Project(2012011023-2)supported by the Natural Science Foundation of Shanxi Province,China
文摘The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carried out.Based on the experimental data,a ternary quadratic regression equation was established by orthogonal experiment.The Ramberg-Osgood constitutive model of tin-bronze connecting rod bushing was obtained.Referred to the constitutive relation of macroscopic incremental,the incremental elastoplastic constitutive relation of spinning parts was deduced based on the Mises yield criterion and kinematic hardening model.The results can be applied to the elastoplastic analysis in finite element numerical simulation.
