In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidifica...In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidification continu- ous casting (DSCC) process. theresults show that the fibrillar strengthening phase, β-Cr, orderlyarranges among the copper matrix phase along the wire direction; andmicrostructure of in-situ composite forms, which retains the basicproperty of good conductivity of the copper matrix and meanwhileobtains the strengthening effect ofβ-Cr phase.展开更多
Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure...Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure the safety of the steel-concrete composite structure, a stud connector model for the joint section was put forward. Experiments were conducted to obtain the relation between load and slip of specimen, the failure pattern of stud connector, the yield bearing capacity and ultimate bearing capacity of a single stud, etc. The whole process of the structural behavior of the specimen was comprehensively analyzed. The features of the internal force distribution in the steel-concrete composite structure and the strain distribution of stud connector under different loads were emphatically studied. The test results show that the stud connector is applicable for the steel-concrete composite structure for pylon of Jintang bridge. The stud has a good ductility performance and a obvious yield process before its destruction. The stud connector basically works in a state of elasticity under a load less than the yield load.展开更多
After driving along the opening of the lower gateway in the lower 15242 working face of Jiulong Mine, the roadway was driven along a fault with a drop of about 20m. The distance between the lower side of the roadway a...After driving along the opening of the lower gateway in the lower 15242 working face of Jiulong Mine, the roadway was driven along a fault with a drop of about 20m. The distance between the lower side of the roadway and the fault was about 5m. At the same time, the roof of the roadway was a composite roof with coal and rock interbedding. The roof of the roadway was 6-8m up and there were 3 coal seams with a thickness of 0.2-0.5m The rocks within 10m were all sandy mudstone. Therefore, due to the influence of fault residual stress and poor roof lithology, the surrounding rock pressure of the roadway is obvious, and the roof and floor of the roadway and the two sides converge greatly. In the process of tunneling, the traditional inclined-distance section of the roof of the No.2 coal seam is adopted, and the roof subsidence of the roadway is still large after the full anchor cable support. In order to ensure the safety of roadway tunneling and use, the roof of the roadway is forced to be reinforced with anchor cables through the posterior approach, which results in more labor and excess cost of supporting materials. In order to solve the above problems, it is urgent to optimize the shape of roadway drivage section and supporting parameters.展开更多
Power cables are important pieces of equipment for energy transmission,but achieving a good balance between flame retardancy and mechanical properties of cable sheaths remains a challenge.In this work,a novel intumesc...Power cables are important pieces of equipment for energy transmission,but achieving a good balance between flame retardancy and mechanical properties of cable sheaths remains a challenge.In this work,a novel intumescent flame retardant(IFR)system containing silicone-containing macromolecular charring agent(Si-MCA)and ammonium polyphosphate(APP)was designed to synergistically improve the flame retardancy and mechanical properties of ethylene-butyl acrylate copolymer(EBA)composites.The optimal mass ratio of APP/Si-MCA was 3/1 in EBA composites(EBA/APP-Si-31),corresponding to the best flame retardancy with 31.2% of limited oxygen index(LOI),V-0 rating in UL-94 vertical burning test,and 76.4%reduction on the peak of heat release rate(PHRR)in cone calorimeter test.The enhancement mechanism was attributed to the synergistic effect of APP/Si-MCA during combustion,including the radical-trapping effect,the dilution effect of non-flammable gases,and the barrier effect of the intumescent char layer.Meanwhile,the tensile results indicated that EBA/APP-Si-31 also exhibited good mechanical properties with the addition of maleic anhydride-grafted polyethylene(PE-g-MA)as the compatibilizer.Thus,the APP/Si-MCA combination is an effective IFRs system for preparing high-performance EBA composites,and it will promote their applications as cable sheath materials.展开更多
The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challe...The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.展开更多
Mechanical model and vibration equation of a cable in cable-stayed space latticed structure (CSLS) under external axial excitation were founded.Determination of the mass lumps and natural frequencies sup- plied by the...Mechanical model and vibration equation of a cable in cable-stayed space latticed structure (CSLS) under external axial excitation were founded.Determination of the mass lumps and natural frequencies sup- plied by the space latticed structure (SLS) was analyzed.Multiple scales method (MSM) was introduced to analyze the characteristics of cable's parametric vibration,and the precise time-integration method (PTIM) was used to solve vibration equation.The vibration behavior of a cable is closely relative to the frequency ratio of the cable and SLS.The cable's parametric vibration caused by the external axial excitation easily occurs if the frequency ratio of the cable and SLS is in a certain range,and the cable's vibration amplitude varies greatly even if the initial disturbance supplied by SLS changes a little.Furthermore,the mechanical model and vibration equation of the composite cable system consisting of main cables and assistant cables were studied. The parametric analysis such as the pre-tension level and arrangement of the assistant cables was carried out. Due to the assistant cables,the single-cable vibration mode can be transferred to the global vibration mode, and the stiffness and damping of the cable system are enhanced.The natural frequencies of the composite cable system with the curve line arrangement of assistant cables are higher than those with the straight-line arrangement and the former is more effective than the latter on the cable's vibration suppression.展开更多
The truss cable support technology was put forward to control the large mining height and composite mudstone strata roadway. This technique makes the steady rock in roadway slantwise top be anchor points, makes the tr...The truss cable support technology was put forward to control the large mining height and composite mudstone strata roadway. This technique makes the steady rock in roadway slantwise top be anchor points, makes the truss cable be steady support structure through special implement, and supplied rock in anchor area with horizontal and vertical pressure which strengthens the surrounding rock＇s anti-strain capability, so it can solve the support problem in roadway with the large cross section and large mining height with mudstone strata. The support mechanism of truss cable about how to make the soft strata stabilize is analyzed by use of the mechanical method. Based on the mechanism and numerical simulation method, the truss cable support project was designed and used to the large mining setting room in eleventh mining area of Bailong Mine successfully.展开更多
In this paper,the effect of gamma-ray irradiation on the electrical conductivity of polypropylene(PP)composites has been studied.The samples are prepared using PP and styrene-ethylene-butylene-styrene elastomer with c...In this paper,the effect of gamma-ray irradiation on the electrical conductivity of polypropylene(PP)composites has been studied.The samples are prepared using PP and styrene-ethylene-butylene-styrene elastomer with contents ranging from 0 wt%to 50 wt%,and exposed to Cobalt-60 gamma irradiation,with a dose from 0 to 250 kGy.Electrical conductivities at different temperatures and trap distributions are measured to observe the deterioration of insulation performance.The microstructure of the sample is estimated using differential scanning calorimetry,X-ray diffraction,thermogravimetric analysis and a scanning electron microscope.The obtained results demonstrate a correlation between the increase in electrical conductivity and the elevation in both total dose and temperature.At 250 kGy,the trap distribution tends to become shallower,accompanied by a decrease in crystallinity,melting and decomposition temperatures of the sample.The PP composite exhibits better stability against irradiation and thermal effects,primarily due to the cross-linked structures formed by irradiation.展开更多
文摘In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidification continu- ous casting (DSCC) process. theresults show that the fibrillar strengthening phase, β-Cr, orderlyarranges among the copper matrix phase along the wire direction; andmicrostructure of in-situ composite forms, which retains the basicproperty of good conductivity of the copper matrix and meanwhileobtains the strengthening effect ofβ-Cr phase.
文摘Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure the safety of the steel-concrete composite structure, a stud connector model for the joint section was put forward. Experiments were conducted to obtain the relation between load and slip of specimen, the failure pattern of stud connector, the yield bearing capacity and ultimate bearing capacity of a single stud, etc. The whole process of the structural behavior of the specimen was comprehensively analyzed. The features of the internal force distribution in the steel-concrete composite structure and the strain distribution of stud connector under different loads were emphatically studied. The test results show that the stud connector is applicable for the steel-concrete composite structure for pylon of Jintang bridge. The stud has a good ductility performance and a obvious yield process before its destruction. The stud connector basically works in a state of elasticity under a load less than the yield load.
文摘After driving along the opening of the lower gateway in the lower 15242 working face of Jiulong Mine, the roadway was driven along a fault with a drop of about 20m. The distance between the lower side of the roadway and the fault was about 5m. At the same time, the roof of the roadway was a composite roof with coal and rock interbedding. The roof of the roadway was 6-8m up and there were 3 coal seams with a thickness of 0.2-0.5m The rocks within 10m were all sandy mudstone. Therefore, due to the influence of fault residual stress and poor roof lithology, the surrounding rock pressure of the roadway is obvious, and the roof and floor of the roadway and the two sides converge greatly. In the process of tunneling, the traditional inclined-distance section of the roof of the No.2 coal seam is adopted, and the roof subsidence of the roadway is still large after the full anchor cable support. In order to ensure the safety of roadway tunneling and use, the roof of the roadway is forced to be reinforced with anchor cables through the posterior approach, which results in more labor and excess cost of supporting materials. In order to solve the above problems, it is urgent to optimize the shape of roadway drivage section and supporting parameters.
基金supported by the National Natural Science Foundation of China(52473059)Taishan Scholar Constructive Engineering Foundation of Shandong Province(tsqn202103079)Key Research and Development Plan of Shandong Province(2024TSGC0264).
文摘Power cables are important pieces of equipment for energy transmission,but achieving a good balance between flame retardancy and mechanical properties of cable sheaths remains a challenge.In this work,a novel intumescent flame retardant(IFR)system containing silicone-containing macromolecular charring agent(Si-MCA)and ammonium polyphosphate(APP)was designed to synergistically improve the flame retardancy and mechanical properties of ethylene-butyl acrylate copolymer(EBA)composites.The optimal mass ratio of APP/Si-MCA was 3/1 in EBA composites(EBA/APP-Si-31),corresponding to the best flame retardancy with 31.2% of limited oxygen index(LOI),V-0 rating in UL-94 vertical burning test,and 76.4%reduction on the peak of heat release rate(PHRR)in cone calorimeter test.The enhancement mechanism was attributed to the synergistic effect of APP/Si-MCA during combustion,including the radical-trapping effect,the dilution effect of non-flammable gases,and the barrier effect of the intumescent char layer.Meanwhile,the tensile results indicated that EBA/APP-Si-31 also exhibited good mechanical properties with the addition of maleic anhydride-grafted polyethylene(PE-g-MA)as the compatibilizer.Thus,the APP/Si-MCA combination is an effective IFRs system for preparing high-performance EBA composites,and it will promote their applications as cable sheath materials.
基金supported by the National Natural Science Foundation of China(Grant No.51874311,52174096)。
文摘The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.
基金The National Natural Science Foundation of China(No.10572091)The Key Project of Fund of Science and Technology Development of Shanghai(No.07JC14023)
文摘Mechanical model and vibration equation of a cable in cable-stayed space latticed structure (CSLS) under external axial excitation were founded.Determination of the mass lumps and natural frequencies sup- plied by the space latticed structure (SLS) was analyzed.Multiple scales method (MSM) was introduced to analyze the characteristics of cable's parametric vibration,and the precise time-integration method (PTIM) was used to solve vibration equation.The vibration behavior of a cable is closely relative to the frequency ratio of the cable and SLS.The cable's parametric vibration caused by the external axial excitation easily occurs if the frequency ratio of the cable and SLS is in a certain range,and the cable's vibration amplitude varies greatly even if the initial disturbance supplied by SLS changes a little.Furthermore,the mechanical model and vibration equation of the composite cable system consisting of main cables and assistant cables were studied. The parametric analysis such as the pre-tension level and arrangement of the assistant cables was carried out. Due to the assistant cables,the single-cable vibration mode can be transferred to the global vibration mode, and the stiffness and damping of the cable system are enhanced.The natural frequencies of the composite cable system with the curve line arrangement of assistant cables are higher than those with the straight-line arrangement and the former is more effective than the latter on the cable's vibration suppression.
文摘The truss cable support technology was put forward to control the large mining height and composite mudstone strata roadway. This technique makes the steady rock in roadway slantwise top be anchor points, makes the truss cable be steady support structure through special implement, and supplied rock in anchor area with horizontal and vertical pressure which strengthens the surrounding rock＇s anti-strain capability, so it can solve the support problem in roadway with the large cross section and large mining height with mudstone strata. The support mechanism of truss cable about how to make the soft strata stabilize is analyzed by use of the mechanical method. Based on the mechanism and numerical simulation method, the truss cable support project was designed and used to the large mining setting room in eleventh mining area of Bailong Mine successfully.
基金National Natural Science Foundation of China,Grant/Award Number:NSFC52077151State Key Laboratory of Electrical Insulation and Power Equipment,Grant/Award Number:EIPE23208Key Laboratory of Engineering Dielectrics and Its Application,Ministry of Education,Grant/Award Number:KFM202203。
文摘In this paper,the effect of gamma-ray irradiation on the electrical conductivity of polypropylene(PP)composites has been studied.The samples are prepared using PP and styrene-ethylene-butylene-styrene elastomer with contents ranging from 0 wt%to 50 wt%,and exposed to Cobalt-60 gamma irradiation,with a dose from 0 to 250 kGy.Electrical conductivities at different temperatures and trap distributions are measured to observe the deterioration of insulation performance.The microstructure of the sample is estimated using differential scanning calorimetry,X-ray diffraction,thermogravimetric analysis and a scanning electron microscope.The obtained results demonstrate a correlation between the increase in electrical conductivity and the elevation in both total dose and temperature.At 250 kGy,the trap distribution tends to become shallower,accompanied by a decrease in crystallinity,melting and decomposition temperatures of the sample.The PP composite exhibits better stability against irradiation and thermal effects,primarily due to the cross-linked structures formed by irradiation.
