Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidat...Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.展开更多
The tensile stress-strain curves of NiTi wires are obtained by tensile experiments under different heat treatments. A phenomenological physical model based on hysteresis element method is developed to describe the exp...The tensile stress-strain curves of NiTi wires are obtained by tensile experiments under different heat treatments. A phenomenological physical model based on hysteresis element method is developed to describe the experimentally determined stress-strain curves of shape memory alloy (SMA) wires. Numerical simulations are made. Simulation results show that：(1) a series of unusual changes on physical and mechanical properties of SMA wires occur when martensitic, especially R (rhombohedral) phase transformation emerge. The stress-strain relation of SMA wires is highly non-linear; (2) there are no notable yielding phenomena before NiTi wires are broken; (3) numerical results obtained by the physical model are in good agreement with experimental data.展开更多
This study focuses on the nanostructure and nanostructural changes of novel graphene/poly（lactic acid） （PLA）/ poly（butylene carbonate） （PBC） nanofibers via electrospinning, which are characterized by different...This study focuses on the nanostructure and nanostructural changes of novel graphene/poly（lactic acid） （PLA）/ poly（butylene carbonate） （PBC） nanofibers via electrospinning, which are characterized by differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile test and in situ small angle x-ray scattering. DSC indicates that the endothermic peak at 295℃ of pure PLA/PBC nanofibers shifted from 317℃ to lower 290℃ with the increasing graphene content. SEM observations reveal a fine dispersion of graphene in the nanofiber matrices. The graphene/PLA/PBC nanofiSers exhibit good improvements in mechanical property. The tensile strength of nanofibers increases with the addition of 0.01 g graphene but reduces with further addition of 0.04g graphene. The scattering intensities increase dramatically when the strain levels are higher than the yield point due to the nucleation and growth of nanovoids or crystals. However, the increasing content of graphene in the PLA/PBC matrix provokes a strong restriction to the deformation-induced crystals.展开更多
In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members o...In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation(T1b2 and T1b3)in Ma-131 well area,which learned from the successful experience of hydraulic fracturing test sites in North America(HFTS-1).Twelve horizontal wells and a high-angle coring well MaJ02 were drilled.The orientation,connection,propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans,imaging logs,direct observation of cores from Well MaJ02,and combined with tracer monitoring data.Results indicate that:(1)Two types of fractures have developed by hydraulic fracturing,i.e.tensile fractures and shear fractures.Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress,and propagate less than 50 m from perforation clusters.Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures,and some of them are in conjugated pairs.Overall,tensile fractures alternate with shear fractures,with shear fractures dominated and activated after tensile ones.(2)Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production,and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed.(3)Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters,which is smaller in the mudstone than the conglomerate.Larger fracturing scale and smaller cluster spacing lead to a higher fracture density,which are important directions to improve the well productivity.展开更多
Split Hopkinson technique has been developed to test the strength of common concrete and steel fiber reinforced concrete under dynamic tensile stress. Two types of test methods are considered, the splitting tensile te...Split Hopkinson technique has been developed to test the strength of common concrete and steel fiber reinforced concrete under dynamic tensile stress. Two types of test methods are considered, the splitting tensile test and a modified spalling test in which a specimen is loaded under uniaxial stress. The result shows that the dynamic strength enhancement of concrete is remarkable by using the reinforcing fiber. But for the common concrete, the base of compressive strength seems to show little effect on the tensile strength under dynamic loading. The experimental results also show that the resistance to tensile fracture of the steel fiber reinforced concrete for C100-mix is higher than those of C40-mix..展开更多
Asphalt-rubber pavements often become dam-aged in high-temperature regions and appear rutted or wavy, and experience slippage. To improve the high-temperature performance of the asphalt-rubber mixture, technical measu...Asphalt-rubber pavements often become dam-aged in high-temperature regions and appear rutted or wavy, and experience slippage. To improve the high-temperature performance of the asphalt-rubber mixture, technical measurements, such as, the optimal adjustment of gradation, technique of composite modification, and control of compaction were investigated. An optimal adjustment of aggregate gradation based on stone matrix asphalt improves the high-temperature stability of the asphaltrubber mixture significantly. Through composite modifi- cation, the effect of asphalt-rubber modification was enhanced, and the dynamic stability and relative defor- mation indices of the asphalt-rubber mixture were improved significantly. Furthermore, compaction parame- ters had a significant influence on the high-temperature stability of the asphalt-rubber mixture. The rolling times for compacting the asphalt-rubber mixture should be controlled to within 18-20 round-trips at a molding temperature at 180℃; if the rolling time is a 12 round-trip, the compaction temperature of the asphalt-rubber mixture should be controlled between 180 and 190℃.展开更多
In this study,nitrogen doped electrochemically exfoliated reduced graphene oxide and carbon black supported platinum(Pt/Nr EGO_(2)-CB_(3))has been prepared to enhance the performance and durability of hightemperature ...In this study,nitrogen doped electrochemically exfoliated reduced graphene oxide and carbon black supported platinum(Pt/Nr EGO_(2)-CB_(3))has been prepared to enhance the performance and durability of hightemperature PEMFCs with lower Pt loading.On the one hand,Pt/Nr EGO_(2)-CB_(3)with the strong interaction between the Pt and nitrogen(N)prevent agglomeration of Pt particles and Pt particles is 5.46±1.46 nm,which is smaller than that of 6.78±1.34 nm in Pt/C.Meanwhile,ECSA of Pt/Nr EGO_(2)-CB_(3)decrease 13.65%after AST,which is much lower than that of 97.99%in Pt/C.On the other hand,the Nr EGO flakes in MEAac act as a barrier to mitigate phosphoric acid redistribution,which improves the formation of triple-phase boundaries(TPBs)and gives stable operation of the MEAacwith a lower decay rate of 0.02 mV h^(-1)within100 h.After steady-state operation,the maximum power density of Pt/Nr EGO_(2)-CB_(3)(0.411 W cm^(-2))is three times higher than that of conventional Pt/C(0.134 W cm^(-2))in high-temperature PEMFCs.After AST,the mass transfer resistance of Pt/Nr EGO_(2)-CB_(3)electrode(0.560Ωcm^(2))is lower than that in Pt/C(0.728Ωcm^(2)).展开更多
In-plane shear properties of composite material laminates are very important in structural design of composite material. Four commonly used in-plane shear test methods were introduced in this paper. In order to study ...In-plane shear properties of composite material laminates are very important in structural design of composite material. Four commonly used in-plane shear test methods were introduced in this paper. In order to study the differences of various shear test methods, two ASTM standard in-plane shear test methods for composite material laminates were experimentally investigated. They are ±45° tensile shear test (ASTM D3518) and V-notched rail shear test (ASTM D7078). Five types of composite material laminates composed of E-glass fiber fabric and vinyl ester resin were utilized, whose stacking sequences are 03s, 0/903s, CSM/0/902s, ±453s and (0/90)2/(±45)2/(0/90)2s, respectively. The test results indicate that the ±45° tensile shear test can predict shear moduli of composite material laminates accurately. However, the predictions of shear strength using ±45° tensile shear test are significantly lower than those of V-notched rail shear test.展开更多
基金supported by the National Key Research and Development Program of China(2022YFB3809005)by SINOPEC(120060-6,121027,and 122042).
文摘Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.
文摘The tensile stress-strain curves of NiTi wires are obtained by tensile experiments under different heat treatments. A phenomenological physical model based on hysteresis element method is developed to describe the experimentally determined stress-strain curves of shape memory alloy (SMA) wires. Numerical simulations are made. Simulation results show that：(1) a series of unusual changes on physical and mechanical properties of SMA wires occur when martensitic, especially R (rhombohedral) phase transformation emerge. The stress-strain relation of SMA wires is highly non-linear; (2) there are no notable yielding phenomena before NiTi wires are broken; (3) numerical results obtained by the physical model are in good agreement with experimental data.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11405199,U1432104,U1332107,10835008,11305198 and U1232203the Project of Education Department of Heilongjiang Province under Grant Nos 135109211 and 135109214
文摘This study focuses on the nanostructure and nanostructural changes of novel graphene/poly（lactic acid） （PLA）/ poly（butylene carbonate） （PBC） nanofibers via electrospinning, which are characterized by differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile test and in situ small angle x-ray scattering. DSC indicates that the endothermic peak at 295℃ of pure PLA/PBC nanofibers shifted from 317℃ to lower 290℃ with the increasing graphene content. SEM observations reveal a fine dispersion of graphene in the nanofiber matrices. The graphene/PLA/PBC nanofiSers exhibit good improvements in mechanical property. The tensile strength of nanofibers increases with the addition of 0.01 g graphene but reduces with further addition of 0.04g graphene. The scattering intensities increase dramatically when the strain levels are higher than the yield point due to the nucleation and growth of nanovoids or crystals. However, the increasing content of graphene in the PLA/PBC matrix provokes a strong restriction to the deformation-induced crystals.
基金Supported by the National Natural Science Foundation of China(52274051)CNPC-China University of Petroleum(Beijing)Strategic Cooperative Project(ZLZX2020-01).
文摘In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing,a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation(T1b2 and T1b3)in Ma-131 well area,which learned from the successful experience of hydraulic fracturing test sites in North America(HFTS-1).Twelve horizontal wells and a high-angle coring well MaJ02 were drilled.The orientation,connection,propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans,imaging logs,direct observation of cores from Well MaJ02,and combined with tracer monitoring data.Results indicate that:(1)Two types of fractures have developed by hydraulic fracturing,i.e.tensile fractures and shear fractures.Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress,and propagate less than 50 m from perforation clusters.Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures,and some of them are in conjugated pairs.Overall,tensile fractures alternate with shear fractures,with shear fractures dominated and activated after tensile ones.(2)Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production,and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed.(3)Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters,which is smaller in the mudstone than the conglomerate.Larger fracturing scale and smaller cluster spacing lead to a higher fracture density,which are important directions to improve the well productivity.
文摘Split Hopkinson technique has been developed to test the strength of common concrete and steel fiber reinforced concrete under dynamic tensile stress. Two types of test methods are considered, the splitting tensile test and a modified spalling test in which a specimen is loaded under uniaxial stress. The result shows that the dynamic strength enhancement of concrete is remarkable by using the reinforcing fiber. But for the common concrete, the base of compressive strength seems to show little effect on the tensile strength under dynamic loading. The experimental results also show that the resistance to tensile fracture of the steel fiber reinforced concrete for C100-mix is higher than those of C40-mix..
文摘Asphalt-rubber pavements often become dam-aged in high-temperature regions and appear rutted or wavy, and experience slippage. To improve the high-temperature performance of the asphalt-rubber mixture, technical measurements, such as, the optimal adjustment of gradation, technique of composite modification, and control of compaction were investigated. An optimal adjustment of aggregate gradation based on stone matrix asphalt improves the high-temperature stability of the asphaltrubber mixture significantly. Through composite modifi- cation, the effect of asphalt-rubber modification was enhanced, and the dynamic stability and relative defor- mation indices of the asphalt-rubber mixture were improved significantly. Furthermore, compaction parame- ters had a significant influence on the high-temperature stability of the asphalt-rubber mixture. The rolling times for compacting the asphalt-rubber mixture should be controlled to within 18-20 round-trips at a molding temperature at 180℃; if the rolling time is a 12 round-trip, the compaction temperature of the asphalt-rubber mixture should be controlled between 180 and 190℃.
基金supported by the Engineering and Physical Sciences Research Council(EPSRC)(EP/P009050/1 and EP/S021531/1)Tthe Henry Royce Institute for Advanced Materials,funded through the EPSRC grants(EP/R00661X/1,EP/S019367/1,EP/P025021/1 and EP/P025498/1)。
文摘In this study,nitrogen doped electrochemically exfoliated reduced graphene oxide and carbon black supported platinum(Pt/Nr EGO_(2)-CB_(3))has been prepared to enhance the performance and durability of hightemperature PEMFCs with lower Pt loading.On the one hand,Pt/Nr EGO_(2)-CB_(3)with the strong interaction between the Pt and nitrogen(N)prevent agglomeration of Pt particles and Pt particles is 5.46±1.46 nm,which is smaller than that of 6.78±1.34 nm in Pt/C.Meanwhile,ECSA of Pt/Nr EGO_(2)-CB_(3)decrease 13.65%after AST,which is much lower than that of 97.99%in Pt/C.On the other hand,the Nr EGO flakes in MEAac act as a barrier to mitigate phosphoric acid redistribution,which improves the formation of triple-phase boundaries(TPBs)and gives stable operation of the MEAacwith a lower decay rate of 0.02 mV h^(-1)within100 h.After steady-state operation,the maximum power density of Pt/Nr EGO_(2)-CB_(3)(0.411 W cm^(-2))is three times higher than that of conventional Pt/C(0.134 W cm^(-2))in high-temperature PEMFCs.After AST,the mass transfer resistance of Pt/Nr EGO_(2)-CB_(3)electrode(0.560Ωcm^(2))is lower than that in Pt/C(0.728Ωcm^(2)).
基金the Natural Science Foundation of China (No.50308008)Western Transportation Science and Technology Foundation of China (No.200431882021).
文摘In-plane shear properties of composite material laminates are very important in structural design of composite material. Four commonly used in-plane shear test methods were introduced in this paper. In order to study the differences of various shear test methods, two ASTM standard in-plane shear test methods for composite material laminates were experimentally investigated. They are ±45° tensile shear test (ASTM D3518) and V-notched rail shear test (ASTM D7078). Five types of composite material laminates composed of E-glass fiber fabric and vinyl ester resin were utilized, whose stacking sequences are 03s, 0/903s, CSM/0/902s, ±453s and (0/90)2/(±45)2/(0/90)2s, respectively. The test results indicate that the ±45° tensile shear test can predict shear moduli of composite material laminates accurately. However, the predictions of shear strength using ±45° tensile shear test are significantly lower than those of V-notched rail shear test.
