In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100℃.The phase transformation in the surface areas during the tensile process was analyzed usin...In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100℃.The phase transformation in the surface areas during the tensile process was analyzed using field emission scanning electron microscope,energy dispersive X-ray spectroscope,electron probe X-ray microanalysis,and transmission electron microscope.The phase transformation mechanism on the surface and the influence mechanism were studied through observation and dynamic calculation.During tensile tests at elevated temperatures,chemical corrosion promotes the precipitation of topologically close-packed(tcp)μphase andσphase on the alloy surface.Both the precipitation amount and size of these two phases on the surface at 1100℃are greater than those at 980℃.The precipitation of tcp phase on the alloy surface results in the formation of an influence layer on the surface area,and the distribution characteristics of alloying elements are significantly different from those of the substrate.The depth of the influence layer at 1100℃is greater than that at 980℃.The precipitation of tcp phase prompts the phase transition fromγphase toγ′phase around the tcp phase.展开更多
In recent years,the zero-span tension technique of paper and pulp-making industry was applied to wood industry for indirectly testing the longitudinal tensile strength of tracheids.In this paper,this technique was use...In recent years,the zero-span tension technique of paper and pulp-making industry was applied to wood industry for indirectly testing the longitudinal tensile strength of tracheids.In this paper,this technique was used to test the longitudinal tension strength of tracheids for Chinese fir specimens with different widths.The results showed that average tension strength was 357.39 MPa.The order of average tension strength of tracheids was:3 mm>12 mm>6 mm>9 mm>7.5 mm.But,earlywood samples frequently contained a little latewood and sample-making was difficult when the width of specimen was bigger,both the testing and the putting of samples were difficult when the width of specimen was smaller.Therefore,the width of 6 mm was chosen as the best width of specimen of Chinese fir.展开更多
Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data...Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data that mooring system designers aim to acquire.To address the need for long-term continuous monitoring of mooring tension in deep-sea marine environments,this paper presents a mooring cable tension monitoring method based on the principle of direct mechanical measurement.The developed tension monitoring sensors were installed and applied in the mooring system of the"Yongle"scientific experimental platform.Over the course of one year,a substantial amount of in-situ tension monitoring data was obtained.Under wave heights of up to 1.24 m,the mooring tension on the floating platform reached 16.5 tons.Through frequency domain and time domain analysis,the spectral characteristics of mooring tension,including waveinduced force,slow drift force,and mooring cable elastic restoring force,were determined.The mooring cable elastic restoring force frequency was approximately half of that of the wave signal.Due to the characteristics of the hinge connection structure of the dual module floating platform,under some specific working conditions the wave-induced force was the maximum of the three different frequency forces,and restoring force was the smallest.展开更多
The deformation and fracture of a third-generation single crystal superalloy during in-situ tension at room temperature were investigated at multiple scales by scanning electron microscope,electron back-scattered diff...The deformation and fracture of a third-generation single crystal superalloy during in-situ tension at room temperature were investigated at multiple scales by scanning electron microscope,electron back-scattered diffractometer,and transmission electron microscope to reveal the deformation and fracture mechanism during tension.The proportion of low angle boundaries(LABs)with angles from 2.5°to 5.5°increases during tension.The change in LABs is particularly pronounced after elongation over 7%.The initiation of microcracks is caused by{111}<110>slip systems.After initiation,the crack size along the stress direction increases whereas the size extension along slip systems is suppressed.The fracture mode of the alloy is quasi-cleavage fracture and the slip lines near the fracture are implicit at room temperature.展开更多
The slow kinetics of the cathode CO_(2) reduction reaction and the decomposition reaction of Li2CO3,a widebandwidth insulating product,lead to difficult CO_(2) capture and high charging potential in Li-CO_(2) batterie...The slow kinetics of the cathode CO_(2) reduction reaction and the decomposition reaction of Li2CO3,a widebandwidth insulating product,lead to difficult CO_(2) capture and high charging potential in Li-CO_(2) batteries.To improve the reaction kinetics and decrease the reaction overpotential,we synthesized mesoporous Pt nanosheets with high tensile strain.The presence of many unsaturated coordinated Pt atoms around the pores gives rise to tensile strain in the mesoporous Pt nanosheets.This tensile strain plays a key role in regulating the interactions between the catalytic surface of Pt and the adsorbed intermediates.The two-dimensional structure provides more active sites on the surface for the catalytic reactions.These superiorities enable a low overpotential of 0.36 V at a cutoff capacity of 100μAh·cm^(−2) at a current density of 10μA·cm^(−2) over more than 2000 h.This study opens new possibilities for the rational design of metal-based materials with strain engineering for electrochemical energy storage.展开更多
Rough micro-nano structures and low surface energy chemical compositions are two essential conditions for constructing superhydrophobic surfaces.However,for low surface tension liquids,which are extremely easy to spre...Rough micro-nano structures and low surface energy chemical compositions are two essential conditions for constructing superhydrophobic surfaces.However,for low surface tension liquids,which are extremely easy to spread and wet on solid surfaces,the design of cantilever structures with internal concavity is the third important parameter to achieve their superomniphobic,whose negative geometrical inflections can effectively lock the solid-liquid-gas three phase contact line,maximize the upward component of capillary force of the suspended droplets,and provide a larger breakthrough pressure for the structured surfaces to avoid the low surface tension liquids from collapsing on the solid surfaces.Based on this,microfabrication was used to prepare mushroom structured surfaces.By precisely controlling the etching parameters,mushroom structures with diameter of 3μm and circular centre distance of 8μm were prepared.The mushroom structure not only achieves super-repellent from high surface tension water(72.8 mN/m)to ultra-low surface tension perfluorohexane(10 mN/m),but also achieves complete rebound even to the high-speed impact of liquid droplets,including water droplets with an impact height of 7.9 cm and perfluorohexane with a height of 3 mm.This fabrication technology helps to build a robust superomniphobic surface for use in harsh environments such as high-speed droplet impacts.展开更多
Model calculations and laboratory experiments were conducted to investigate the influence of surface tension of the molten steel on the agglomeration trend of Al_(2)O_(3) inclusions.The agglomeration trends of inclusi...Model calculations and laboratory experiments were conducted to investigate the influence of surface tension of the molten steel on the agglomeration trend of Al_(2)O_(3) inclusions.The agglomeration trends of inclusions were compared using the calculated attractiveness.When the S content in the steel increased from 2.7×10^(-6) to 789×10^(-6),the surface tension of the molten steel decreased from 1.91 to 1.39 N/m,while the attractive force between inclusions increased from 5×10^(-18) to 5×10^(-16) N,and the critical collision distance of Al_(2)O_(3) inclusions gradually increased from 30 to 70μm.A model of the relationship between the capillary force of inclusions and S content in steel was established.It was found that the capillary force calculated by the model showed the same trend as the attractive force obtained from experiments,and an increase in the S content promoted the attraction between inclusions.展开更多
The rock-concrete interface has a signifcant infuence on the stability of rock-concrete structures in coal mine roadway that are vulnerable to tensile loads.In this study,direct tension tests in combination with laser...The rock-concrete interface has a signifcant infuence on the stability of rock-concrete structures in coal mine roadway that are vulnerable to tensile loads.In this study,direct tension tests in combination with laser scanning and acoustic emission techniques were used to study the infuences of loading angle and strength contrast on tensile behavior of rock-concrete interface.Results show that peak strain and tensile strength of granite-concrete specimens are lower than those of granite and concrete.Acoustic emission(AE)characteristic of the granite-concrete specimens difers from that of concrete and granite.With the loading angle increases,peak strain and tensile strength of the granite-concrete specimens increase,and the failure mode varies from the interfacial tensile failure to mixed tensile failure due to the increased contact area and decreased tensile stress applied on the granite-concrete interface.In addition,the accumulative AE counts of the granite-concrete specimen are also signifcantly afected by the loading angle;in particular,when the loading angle is sufciently large,e.g.,55°,the accumulative AE counts sharply increase twice.Diferent strength contrasts between rock and concrete result in diferent failure characteristics of rock-concrete specimens under direct tensile loads.When tensile strength of rock is lower than that of concrete,failure often occurs in the rock section and the tensile strength and peak strain of the rock-concrete specimen is similar to that of rock.By contrast,when the tensile strength of rock is higher than of the concrete,failure appears at the interface,and rock-concrete interface dominates the tensile properties of rock-concrete specimens.The failure mode is dominated by the coupling efect of loading angle and strength contrast.The fndings in this study are helpful in understanding the mechanical behaviour of rock-concrete structures under direct tension and applicable to the design and reinforcement of rock-concrete structures in coal roadway.展开更多
The U.S.imposition of high tariffs on Chinese goods has triggered short-term strains on China’s exports.At the same time,it has also accelerated its strategic pivot toward technological self-reliance,regional integra...The U.S.imposition of high tariffs on Chinese goods has triggered short-term strains on China’s exports.At the same time,it has also accelerated its strategic pivot toward technological self-reliance,regional integration,and domestic demand expansion.展开更多
The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165℃for different time.The results indicated that the c...The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165℃for different time.The results indicated that the creep deformation under tensile stress was greater than that under compressive stress.As the stress level increases,the compressive creep rate showed more significant increase.The yield strength after compressive stress creep-ageing was higher than that after stress-free ageing,with the lowest strength observed in the tensile-aged sample.Overall,the average phase length after compressive stress creep-ageing was larger than after tensile stress ageing.Under tensile stress,the number and size of precipitates at small angles to the stress direction were larger than those perpendicular to the stress direction.In contrast,under compressive stress,this relationship was reversed,and the preferential orientation of phases became more pronounced with ageing time.A unified,physics-based creep-ageing constitutive model,accounting for the orientation of precipitation,was developed for both tensile and compressive stress conditions.The predicted results were in good agreement with the experimental data.These findings,along with the developed model,provide a theoretical and simulation basis for precise creep-ageing forming of components under complex stresses.展开更多
The tension leg platform is a typical compliant platform that is connected to the seabed through tension leg tendons.However,it is hard to characterize tension leg tendons due to the complexity of their force and moti...The tension leg platform is a typical compliant platform that is connected to the seabed through tension leg tendons.However,it is hard to characterize tension leg tendons due to the complexity of their force and motions as well as the lack of full-scale test methods.We performed a finite element analysis and full-scale four-point bending fatigue tests on tension leg tendons and connectors to study the fatigue properties of the tension leg tendons(made using 36in-X70 steel pipes)used in the Gulf of Mexico.The maximum deflection and the maximum stress of samples under complex loading were estimated through finite element simulation to ensure the testing requirements,including load intensity,load method,load path,and frequency.The maximum equivalent strain and the corresponding position were then determined through testing,which were further compared with simulation results to verify their accuracy and applicability.The maximum strain amplitude from simulations was 761.42με,while the equivalent strain amplitude obtained through tests was 734.90με,which is close to the simulation result.In addition,when the number of fatigue cycles reached 1.055 million,sample damage did not occur.It confirms that the fatigue performance of the tendon steel pipe weld is better than the C1 curve value shown in the DNV RP C203 specification.The proposed full-scale approach to study the fatigue properties of tension leg tendons can provide a reference for domestic engineering design and manufacture of tension leg tendons as well as promote the localization of test equipment.展开更多
The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase...The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase of applied stress,the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious.However,the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples.Dislocation density,dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process.In addition,the tensile and compressive stresses have little effect on the width of the precipitate-free zone(PFZ).It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy,the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress.In the field of civil aviation aircraft component manufacturing,the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.展开更多
This study presents a numerical investigation of shallow water wave dynamics with particular emphasis on the role of surface tension.In the absence of surface tension,shallow water waves are primarily driven by gravit...This study presents a numerical investigation of shallow water wave dynamics with particular emphasis on the role of surface tension.In the absence of surface tension,shallow water waves are primarily driven by gravity and are well described by the classical Boussinesq equation,which incorporates fourth-order dispersion.Under this framework,solitary and shock waves arise through the balance of nonlinearity and gravity-induced dispersion,producing waveforms whose propagation speed,amplitude,and width depend largely on depth and initial disturbance.The resulting dynamics are comparatively smoother,with solitary waves maintaining coherent structures and shock waves displaying gradual transitions.When surface tension is incorporated,however,the dynamics become significantly richer.Surface tension introduces additional sixth-order dispersive terms into the governing equation,extending the classical model to the sixth-order Boussinesq equation.This higher-order dispersion modifies the balance between nonlinearity and dispersion,leading to sharper solitary wave profiles,altered shock structures,and a stronger sensitivity of wave stability to parametric variations.Surface tension effects also change the scaling laws for wave amplitude and velocity,producing conditions where solitary waves can narrow while maintaining large amplitudes,or where shock fronts steepen more rapidly compared to the tension-free case.These differences highlight how capillary forces,though often neglected in macroscopic wave studies,play a fundamental role in shaping dynamics at smaller scales or in systems with strong fluid–interface interactions.The analysis in this work is carried out using the Laplace-Adomian Decomposition Method(LADM),chosen for its efficiency and accuracy in solving high-order nonlinear partial differential equations.The numerical scheme successfully recovers both solitary and shock wave solutions under the sixth-order model,with error analysis confirming remarkably low numerical deviations.These results underscore the robustness of the method while demonstrating the profound contrast between shallow water wave dynamics without and with surface tension.展开更多
CO_(2)/N_(2) injection in heavy oil reservoirs has been demonstrated to enhance oil recovery(EOR)and facilitate CO_(2) capture,utilization,and storage(CCUS).Interfacial tension(IFT)is a crucial parameter for character...CO_(2)/N_(2) injection in heavy oil reservoirs has been demonstrated to enhance oil recovery(EOR)and facilitate CO_(2) capture,utilization,and storage(CCUS).Interfacial tension(IFT)is a crucial parameter for characterizing oil recovery,but it can be influenced by real-time changes in reservoir pressure and temperature during gas injection.The impact of the CO_(2)/N_(2) ratio on the oil-gas IFT under varying temperature and pressure conditions remains unclear.Therefore,a systematic study was conducted to investigate the effects of multiple parameters on the oil-gas IFT during development processes,and a three-dimensional(3D)database and a regression model of IFT were established using experimental data.The results show that IFT is strongly correlated with density difference,moderately correlated with pressure and CO_(2) proportion,weakly correlated with saturates content and resin content,and nonlinearly correlated with temperature,aromatics content,and asphaltene content,respectively.Moreover,it has been observed that an increase in pressure or CO_(2) proportion can lead to a reduction in IFT.However,the impact of temperature changes on IFT varies across different pressure ranges.We introduce a new parameter,the equivalent interfacial tension pressure during temperature changes(EITP),to characterize this effect and discuss the reasons for the emergence of EITP,providing new insight into optimizing the CO_(2)/N_(2) injection ratio in the reservoir.This study aims to reveal the advantages of oil-gas interface characteristics under the influence of multiple parameters in promoting low-carbon and efficient development of heavy oil reservoirs,and to explore the significance of CO_(2)/N_(2) for enhancing heavy oil recovery.展开更多
文摘In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100℃.The phase transformation in the surface areas during the tensile process was analyzed using field emission scanning electron microscope,energy dispersive X-ray spectroscope,electron probe X-ray microanalysis,and transmission electron microscope.The phase transformation mechanism on the surface and the influence mechanism were studied through observation and dynamic calculation.During tensile tests at elevated temperatures,chemical corrosion promotes the precipitation of topologically close-packed(tcp)μphase andσphase on the alloy surface.Both the precipitation amount and size of these two phases on the surface at 1100℃are greater than those at 980℃.The precipitation of tcp phase on the alloy surface results in the formation of an influence layer on the surface area,and the distribution characteristics of alloying elements are significantly different from those of the substrate.The depth of the influence layer at 1100℃is greater than that at 980℃.The precipitation of tcp phase prompts the phase transition fromγphase toγ′phase around the tcp phase.
基金the National Natural Science Key Foundation of China"The Constructing and Application of Token System for MechanicsProperties of Wood Cell Wall(C02060102)"
文摘In recent years,the zero-span tension technique of paper and pulp-making industry was applied to wood industry for indirectly testing the longitudinal tensile strength of tracheids.In this paper,this technique was used to test the longitudinal tension strength of tracheids for Chinese fir specimens with different widths.The results showed that average tension strength was 357.39 MPa.The order of average tension strength of tracheids was:3 mm>12 mm>6 mm>9 mm>7.5 mm.But,earlywood samples frequently contained a little latewood and sample-making was difficult when the width of specimen was bigger,both the testing and the putting of samples were difficult when the width of specimen was smaller.Therefore,the width of 6 mm was chosen as the best width of specimen of Chinese fir.
文摘Mooring cable tension is a crucial parameter for evaluating the safety and reliability of a floating platform mooring system.The real-time mooring tension in an actual marine environment has always been essential data that mooring system designers aim to acquire.To address the need for long-term continuous monitoring of mooring tension in deep-sea marine environments,this paper presents a mooring cable tension monitoring method based on the principle of direct mechanical measurement.The developed tension monitoring sensors were installed and applied in the mooring system of the"Yongle"scientific experimental platform.Over the course of one year,a substantial amount of in-situ tension monitoring data was obtained.Under wave heights of up to 1.24 m,the mooring tension on the floating platform reached 16.5 tons.Through frequency domain and time domain analysis,the spectral characteristics of mooring tension,including waveinduced force,slow drift force,and mooring cable elastic restoring force,were determined.The mooring cable elastic restoring force frequency was approximately half of that of the wave signal.Due to the characteristics of the hinge connection structure of the dual module floating platform,under some specific working conditions the wave-induced force was the maximum of the three different frequency forces,and restoring force was the smallest.
文摘The deformation and fracture of a third-generation single crystal superalloy during in-situ tension at room temperature were investigated at multiple scales by scanning electron microscope,electron back-scattered diffractometer,and transmission electron microscope to reveal the deformation and fracture mechanism during tension.The proportion of low angle boundaries(LABs)with angles from 2.5°to 5.5°increases during tension.The change in LABs is particularly pronounced after elongation over 7%.The initiation of microcracks is caused by{111}<110>slip systems.After initiation,the crack size along the stress direction increases whereas the size extension along slip systems is suppressed.The fracture mode of the alloy is quasi-cleavage fracture and the slip lines near the fracture are implicit at room temperature.
基金supported by the National Natural Science Foundation of China(52002366,22075263,22571288)the Fundamental Research Funds for the Central Universities(WK2060000091,WK2060250115,WK2060000039)the Students’Innovation and Entrepreneurship Foundation of USTC(CY2023C021).
文摘The slow kinetics of the cathode CO_(2) reduction reaction and the decomposition reaction of Li2CO3,a widebandwidth insulating product,lead to difficult CO_(2) capture and high charging potential in Li-CO_(2) batteries.To improve the reaction kinetics and decrease the reaction overpotential,we synthesized mesoporous Pt nanosheets with high tensile strain.The presence of many unsaturated coordinated Pt atoms around the pores gives rise to tensile strain in the mesoporous Pt nanosheets.This tensile strain plays a key role in regulating the interactions between the catalytic surface of Pt and the adsorbed intermediates.The two-dimensional structure provides more active sites on the surface for the catalytic reactions.These superiorities enable a low overpotential of 0.36 V at a cutoff capacity of 100μAh·cm^(−2) at a current density of 10μA·cm^(−2) over more than 2000 h.This study opens new possibilities for the rational design of metal-based materials with strain engineering for electrochemical energy storage.
基金funded by the Postdoctoral Fellowship Program of CPSF under Grant Number GZC20233434the Key Cultivation Program of the Harbin Institute of Technology FUEA0400400523.
文摘Rough micro-nano structures and low surface energy chemical compositions are two essential conditions for constructing superhydrophobic surfaces.However,for low surface tension liquids,which are extremely easy to spread and wet on solid surfaces,the design of cantilever structures with internal concavity is the third important parameter to achieve their superomniphobic,whose negative geometrical inflections can effectively lock the solid-liquid-gas three phase contact line,maximize the upward component of capillary force of the suspended droplets,and provide a larger breakthrough pressure for the structured surfaces to avoid the low surface tension liquids from collapsing on the solid surfaces.Based on this,microfabrication was used to prepare mushroom structured surfaces.By precisely controlling the etching parameters,mushroom structures with diameter of 3μm and circular centre distance of 8μm were prepared.The mushroom structure not only achieves super-repellent from high surface tension water(72.8 mN/m)to ultra-low surface tension perfluorohexane(10 mN/m),but also achieves complete rebound even to the high-speed impact of liquid droplets,including water droplets with an impact height of 7.9 cm and perfluorohexane with a height of 3 mm.This fabrication technology helps to build a robust superomniphobic surface for use in harsh environments such as high-speed droplet impacts.
基金the National Natural Science Foundation of China(Grant No.U22A20171)the National Key Research and Development Program Project of China(2023YFB3709900)+1 种基金the China Baowu Low Carbon Metallurgical Innovation Fund(BWLCF202315)the Pangang-USTB Vanadium and Titanium Research Institute Research Project,the High Steel Center(HSC)at North China University of Technology,Yanshan University and University of Science and Technology Beijing,China.
文摘Model calculations and laboratory experiments were conducted to investigate the influence of surface tension of the molten steel on the agglomeration trend of Al_(2)O_(3) inclusions.The agglomeration trends of inclusions were compared using the calculated attractiveness.When the S content in the steel increased from 2.7×10^(-6) to 789×10^(-6),the surface tension of the molten steel decreased from 1.91 to 1.39 N/m,while the attractive force between inclusions increased from 5×10^(-18) to 5×10^(-16) N,and the critical collision distance of Al_(2)O_(3) inclusions gradually increased from 30 to 70μm.A model of the relationship between the capillary force of inclusions and S content in steel was established.It was found that the capillary force calculated by the model showed the same trend as the attractive force obtained from experiments,and an increase in the S content promoted the attraction between inclusions.
基金supported by National Key R&D Program of China(2022YFC3004602)National Natural Science Foundation of China(52325404)+2 种基金Program for Guangdong Introducing Innovative and Entrepreneurial Teams(2019ZT08G315)Shenzhen Science and Technology Program(JCYJ20220818095605012)Shenzhen University 2035 Initiative(2022B001).
文摘The rock-concrete interface has a signifcant infuence on the stability of rock-concrete structures in coal mine roadway that are vulnerable to tensile loads.In this study,direct tension tests in combination with laser scanning and acoustic emission techniques were used to study the infuences of loading angle and strength contrast on tensile behavior of rock-concrete interface.Results show that peak strain and tensile strength of granite-concrete specimens are lower than those of granite and concrete.Acoustic emission(AE)characteristic of the granite-concrete specimens difers from that of concrete and granite.With the loading angle increases,peak strain and tensile strength of the granite-concrete specimens increase,and the failure mode varies from the interfacial tensile failure to mixed tensile failure due to the increased contact area and decreased tensile stress applied on the granite-concrete interface.In addition,the accumulative AE counts of the granite-concrete specimen are also signifcantly afected by the loading angle;in particular,when the loading angle is sufciently large,e.g.,55°,the accumulative AE counts sharply increase twice.Diferent strength contrasts between rock and concrete result in diferent failure characteristics of rock-concrete specimens under direct tensile loads.When tensile strength of rock is lower than that of concrete,failure often occurs in the rock section and the tensile strength and peak strain of the rock-concrete specimen is similar to that of rock.By contrast,when the tensile strength of rock is higher than of the concrete,failure appears at the interface,and rock-concrete interface dominates the tensile properties of rock-concrete specimens.The failure mode is dominated by the coupling efect of loading angle and strength contrast.The fndings in this study are helpful in understanding the mechanical behaviour of rock-concrete structures under direct tension and applicable to the design and reinforcement of rock-concrete structures in coal roadway.
文摘The U.S.imposition of high tariffs on Chinese goods has triggered short-term strains on China’s exports.At the same time,it has also accelerated its strategic pivot toward technological self-reliance,regional integration,and domestic demand expansion.
基金Project(JCKY2023205B003)supported by the Defense Industrial Technology Development Program,China。
文摘The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165℃for different time.The results indicated that the creep deformation under tensile stress was greater than that under compressive stress.As the stress level increases,the compressive creep rate showed more significant increase.The yield strength after compressive stress creep-ageing was higher than that after stress-free ageing,with the lowest strength observed in the tensile-aged sample.Overall,the average phase length after compressive stress creep-ageing was larger than after tensile stress ageing.Under tensile stress,the number and size of precipitates at small angles to the stress direction were larger than those perpendicular to the stress direction.In contrast,under compressive stress,this relationship was reversed,and the preferential orientation of phases became more pronounced with ageing time.A unified,physics-based creep-ageing constitutive model,accounting for the orientation of precipitation,was developed for both tensile and compressive stress conditions.The predicted results were in good agreement with the experimental data.These findings,along with the developed model,provide a theoretical and simulation basis for precise creep-ageing forming of components under complex stresses.
基金supported by the Innovation Capability Improvement Project of Scientific and Technological Small and Medium-sized Enterprises in Shandong Province,China(2021TSGC1415).
文摘The tension leg platform is a typical compliant platform that is connected to the seabed through tension leg tendons.However,it is hard to characterize tension leg tendons due to the complexity of their force and motions as well as the lack of full-scale test methods.We performed a finite element analysis and full-scale four-point bending fatigue tests on tension leg tendons and connectors to study the fatigue properties of the tension leg tendons(made using 36in-X70 steel pipes)used in the Gulf of Mexico.The maximum deflection and the maximum stress of samples under complex loading were estimated through finite element simulation to ensure the testing requirements,including load intensity,load method,load path,and frequency.The maximum equivalent strain and the corresponding position were then determined through testing,which were further compared with simulation results to verify their accuracy and applicability.The maximum strain amplitude from simulations was 761.42με,while the equivalent strain amplitude obtained through tests was 734.90με,which is close to the simulation result.In addition,when the number of fatigue cycles reached 1.055 million,sample damage did not occur.It confirms that the fatigue performance of the tendon steel pipe weld is better than the C1 curve value shown in the DNV RP C203 specification.The proposed full-scale approach to study the fatigue properties of tension leg tendons can provide a reference for domestic engineering design and manufacture of tension leg tendons as well as promote the localization of test equipment.
基金Project(2021YFB3400900)supported by the National Key R&D Program of ChinaProjects(51905551,52205435)supported by the National Natural Science Foundation of China Youth Foundation+1 种基金Project(2022ZZTS0196)supported by the Fundamental Research Founds for the Central Universities,ChinaProject(CX20220282)supported by the Hunan Provincial Innovation Foundation for Postgraduate,China。
文摘The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase of applied stress,the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious.However,the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples.Dislocation density,dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process.In addition,the tensile and compressive stresses have little effect on the width of the precipitate-free zone(PFZ).It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy,the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress.In the field of civil aviation aircraft component manufacturing,the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.
文摘This study presents a numerical investigation of shallow water wave dynamics with particular emphasis on the role of surface tension.In the absence of surface tension,shallow water waves are primarily driven by gravity and are well described by the classical Boussinesq equation,which incorporates fourth-order dispersion.Under this framework,solitary and shock waves arise through the balance of nonlinearity and gravity-induced dispersion,producing waveforms whose propagation speed,amplitude,and width depend largely on depth and initial disturbance.The resulting dynamics are comparatively smoother,with solitary waves maintaining coherent structures and shock waves displaying gradual transitions.When surface tension is incorporated,however,the dynamics become significantly richer.Surface tension introduces additional sixth-order dispersive terms into the governing equation,extending the classical model to the sixth-order Boussinesq equation.This higher-order dispersion modifies the balance between nonlinearity and dispersion,leading to sharper solitary wave profiles,altered shock structures,and a stronger sensitivity of wave stability to parametric variations.Surface tension effects also change the scaling laws for wave amplitude and velocity,producing conditions where solitary waves can narrow while maintaining large amplitudes,or where shock fronts steepen more rapidly compared to the tension-free case.These differences highlight how capillary forces,though often neglected in macroscopic wave studies,play a fundamental role in shaping dynamics at smaller scales or in systems with strong fluid–interface interactions.The analysis in this work is carried out using the Laplace-Adomian Decomposition Method(LADM),chosen for its efficiency and accuracy in solving high-order nonlinear partial differential equations.The numerical scheme successfully recovers both solitary and shock wave solutions under the sixth-order model,with error analysis confirming remarkably low numerical deviations.These results underscore the robustness of the method while demonstrating the profound contrast between shallow water wave dynamics without and with surface tension.
基金supported by National Natural Science Foundation of China(52204068 and U20B6003)the Program for Scientific Research Innovation Team of Young Scholars in Colleges and Universities of Shandong Province(2022KJ067)。
文摘CO_(2)/N_(2) injection in heavy oil reservoirs has been demonstrated to enhance oil recovery(EOR)and facilitate CO_(2) capture,utilization,and storage(CCUS).Interfacial tension(IFT)is a crucial parameter for characterizing oil recovery,but it can be influenced by real-time changes in reservoir pressure and temperature during gas injection.The impact of the CO_(2)/N_(2) ratio on the oil-gas IFT under varying temperature and pressure conditions remains unclear.Therefore,a systematic study was conducted to investigate the effects of multiple parameters on the oil-gas IFT during development processes,and a three-dimensional(3D)database and a regression model of IFT were established using experimental data.The results show that IFT is strongly correlated with density difference,moderately correlated with pressure and CO_(2) proportion,weakly correlated with saturates content and resin content,and nonlinearly correlated with temperature,aromatics content,and asphaltene content,respectively.Moreover,it has been observed that an increase in pressure or CO_(2) proportion can lead to a reduction in IFT.However,the impact of temperature changes on IFT varies across different pressure ranges.We introduce a new parameter,the equivalent interfacial tension pressure during temperature changes(EITP),to characterize this effect and discuss the reasons for the emergence of EITP,providing new insight into optimizing the CO_(2)/N_(2) injection ratio in the reservoir.This study aims to reveal the advantages of oil-gas interface characteristics under the influence of multiple parameters in promoting low-carbon and efficient development of heavy oil reservoirs,and to explore the significance of CO_(2)/N_(2) for enhancing heavy oil recovery.
