In the field of optoelectronics,certain types of data may be difficult to accurately annotate,such as high-resolution optoelectronic imaging or imaging in certain special spectral ranges.Weakly supervised learning can...In the field of optoelectronics,certain types of data may be difficult to accurately annotate,such as high-resolution optoelectronic imaging or imaging in certain special spectral ranges.Weakly supervised learning can provide a more reliable approach in these situations.Current popular approaches mainly adopt the classification-based class activation maps(CAM)as initial pseudo labels to solve the task.展开更多
A Double Shear Model(DSM) was used in a numerical simulation on bolted rock joint shearing performance.An entire bolt deformed as the letter'U'under a shear load between two joints.Near the bolt-joint intersec...A Double Shear Model(DSM) was used in a numerical simulation on bolted rock joint shearing performance.An entire bolt deformed as the letter'U'under a shear load between two joints.Near the bolt-joint intersection,the bolt partly deformed as the letter'Z'.There were two critical points along the bolt:one was at the bolt-joint intersection with zero bending moment and the other at the maximum bending moment(plastic hinge) with zero shear stress.The blocks on two sides slid along the bolt as it deformed. A separation area was found between the two joint contact surfaces of the middle rock block and sided block.This area of separation was related to bolt diameter and external forces.We assume that this area is related to the work of external forces.Further research is needed.展开更多
The 3D FEM numerical simulation on multi-action precision cold forging technology of universal joint cross and differential spider is done in this article using DEFORM Software, a commercial computer aided engineering...The 3D FEM numerical simulation on multi-action precision cold forging technology of universal joint cross and differential spider is done in this article using DEFORM Software, a commercial computer aided engineering software specializing in forming and heat treatment simulation technology, and suitable for cold, warm and hot forging process. The material flow properties, the dynamic variation of stress and strain in the process of deformation and the load-stroke curve have also been achieved. A good consistency is exhibited between simulation results and practical data. Based on the DEFORM simulation results, the optimized procedure has been found for forging a universal joint cross. What should be emphasized here is that a better understanding of practical forging characters and the environmental factors can greatly improve the simulation accuracy thus make the simulation results more reliable.展开更多
The joint probability distribution of wind speed and significant wave height in the Bohai Bay was investigated by comparing the Gurnbel logistic model, the Gumbel-Hougaard （GH） copula function, and the Clayton copul...The joint probability distribution of wind speed and significant wave height in the Bohai Bay was investigated by comparing the Gurnbel logistic model, the Gumbel-Hougaard （GH） copula function, and the Clayton copula function. Twenty years of wind data from 1989 to 2008 were collected from the European Centre for Medium-Range Weather Forecasts （ECMWF） database and the blended wind data of the Quick Scatterometer （QSCAT） satellite data set and re-analysis data from the United States National Centers for Environmental Prediction （NCEP）. Several typhoons were taken into account and merged with the background wind fields from the ECMWF or QSCAT/NCEP database. The 20-year data of significant wave height were calculated with the unstructured-grid version of the third-generation wind wave model Simulating WAves Nearshore （SWAN） under extreme wind process conditions. The Gumbel distribution was used for univariate and marginal distributions. The distribution parameters were estimated with the method of L-moments. Based on the marginal distributions, the joint probability distributions, the associated return periods, and the conditional probability distributions were obtained. The GH copula function was found to be optimal according to the ordinary least squares （OLS） test. The results show that wind waves are the prevailing type of wave in the Bohai Bay.展开更多
Based on CT scanning pictures from a volunteer＇s knee joint, a three-dimensional finite element model of the healthy human knee joint is constructed including complete femur, tibia, fibular, patellar and the main car...Based on CT scanning pictures from a volunteer＇s knee joint, a three-dimensional finite element model of the healthy human knee joint is constructed including complete femur, tibia, fibular, patellar and the main cartilage and ligaments. This model was validated using experimental and numerical results obtained from other authors. The pressure distribution of contact surfaces of knee joint are calculated and analyzed under the load action of ‘heel strike＇, ‘single limb stance＇ and ‘toe-off＇. The results of the gait cycle are that the contact areas of medial cartilage are larger than that of lateral cartilage; the contact force and contact areas would grow larger with the load increasing; the pressure of lateral meniscus is steady, relative to the significant variation of peak pressure in medial meniscus; and the peak value of contact pressure on all components are usually found at about 4570 of the gait cycle.展开更多
A revised displacement discontinuity method(DDM) program is developed for the simulation of rock joint propagation and dilatancy analysis. The non-linear joint model used in the program adopts Barton-Bandis normal def...A revised displacement discontinuity method(DDM) program is developed for the simulation of rock joint propagation and dilatancy analysis. The non-linear joint model used in the program adopts Barton-Bandis normal deformation model, Kulhaway shear deformation model and Mohr-Coulomb criterion. The joint propagation criterion is based on the equivalent stress intensity factor which can be obtained by regression analysis. The simulated rock joint propagation accords well with the existing knowledge. The closure and opening of joint is investigated by DDM, and it is shown that if the opening volume of propagated joint is larger than closure volume of the old joint, the joint dilatancy occurs. The dilatancy condition is mainly controlled by the normal stiffness of the rock joint. When the normal stiffness is larger than the critical value, joint dilatancy occurs. The critical normal stiffness of rock joint changes with the joint-load angle, and joint dilatancy is most possible to occur at 30°.展开更多
2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock ...2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.展开更多
The corrosion behavior of B10 copper-nickel alloy welded joints in seawater pipeline system was analyzed under local turbulence induced by weld residual height.The corrosion behavior was evaluated by array electrode t...The corrosion behavior of B10 copper-nickel alloy welded joints in seawater pipeline system was analyzed under local turbulence induced by weld residual height.The corrosion behavior was evaluated by array electrode technology,mor-phology and elemental characterization,and COMSOL Multiphysics simulation.The results provide a theoretical basis for the corrosion and leakage of B10 alloy in seawater pipeline under the action of turbulence.The results show that residual height-induced turbulence exhibits a significant effect on the corrosion behavior in different areas of welded joints in B10 alloy.Turbulence can damage some surfaces,causing polarity deflection followed by acceleration of corrosion,or it is easier to form a protective film to slow down corrosion.COMSOL Multiphysics results show that the shear rate and turbulent kinetic energy increase linearly with the increase in residual height and velocity.The corrosion behavior of alloy surface is influenced by controlling the mass transfer rate and surface state.展开更多
Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of...Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of temperature cycling profile parameters. The results show that temperature cycling history has significant effect on the stress response of the solder joint. Based on the concept of relative damage stress proposed by the authors, it is found that enough high temperature holding time is necessary for designing the temperature cycling profile in accelerated thermal fatigue test.展开更多
The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field...The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.展开更多
The analysis of the impulse voltage on the internal electric field of the cable joint plays a key role in studying the breakdown of the joint. Based on the finite element method, a three-dimensional electromagnetic fi...The analysis of the impulse voltage on the internal electric field of the cable joint plays a key role in studying the breakdown of the joint. Based on the finite element method, a three-dimensional electromagnetic field simulation model of the cable joint is established in this paper. Simulation results show that the voltage at the head of the cable joint reaches about twice the impulse voltage. The increase of the conductivity of semi-conductive material also leads to the increase of electric field intensity. Then, several points and curves at different positions are selected for further analysis in this paper. Among them, the electric field distortion at the edge of the high voltage shield is the most serious and the electric field in the air gap is the least.展开更多
Pinless friction stir spot welding(P-FSSW)was performed to manufacture Mg/steel lap joints.Orthogonal tests for P-FSSW of Mg/steel were investigated,and the main factors affecting the properties of Mg/steel lap joints...Pinless friction stir spot welding(P-FSSW)was performed to manufacture Mg/steel lap joints.Orthogonal tests for P-FSSW of Mg/steel were investigated,and the main factors affecting the properties of Mg/steel lap joints were derived.The shear force of the Mg/steel lap joints gradually increased and then decreased as the welding time increased.Maximum shear force was 5.3 kN.Fe-Al intermetallic compound(IMC)was formed at the Mg/steel interface near the steel side,and Mg-Al IMCs were formed at the Mg/steel interface near the Mg alloy side.Mg/steel lap joint was transformed from an initial solid-state welding to fusion-brazing welding as the welding time increased.No hole defects were formed in Mg/steel solid-state welding joints,whereas hole defects appeared in Mg/steel fusion-brazing welding joints.The temperature field of Mg/steel lap joints was simulated to analyze hole defects generated during the welding process.Hole defects can be eliminated by changing the spindle deflection angle,and the shear force decreased.Excessive spindle deflection can also lead to failure to form a stable joint.Hole defects were removed because the spindle deflection angle reduced the interfacial reaction temperature,and a solid-state welding joint was formed,which resulted in an absence of fusion-brazing welding hole formation.展开更多
Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation cou...Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation coupled motion,the horizontal vibrating-uplift rocking coupled motion,and the horizontal sliding-uplift rocking coupled motion.The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson.The numerical models of four motion modes of caisson are developed,and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment.It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.展开更多
With the development of ocean engineering, it is one of the most important factors which determine the structural safety, cost and suitable forms of engineerings to select the ocean environmental design criteria. Owin...With the development of ocean engineering, it is one of the most important factors which determine the structural safety, cost and suitable forms of engineerings to select the ocean environmental design criteria. Owing to the complexity , variation and randomness of ocean environmental conditions, the commonly used methods for determining design criteria cannot consider the joint occurring probabilities of several environmental factors ,therefore, lead to overestimate design criteria of them and result in an unnecessary overspend invest in engineering. On the basis of the measured and hindcasting data and the multi-demension joint probability theory, this paper presented the study of the joint loads of wind , wave and current on the offshore structures and its responsible joint probability level with the application of random simulation techniques, and presented the joint design criteria of environmental loads for the realistic design of engineerings.展开更多
A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion pla...A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion plane, with a socket to rotate internal/externally. At the same time a dynamic loading cycle is applied. A validation test was performed on a cemented femoral stem within a novel composite femur. The hone quality has a strong effect on the stem migration and on the integrity of the interfaces. The migration of the stem is a combination of 3-D translation and rotation of the stem. Under the same loading conditions, weak bone allows more stem migration than strong bone. There is a great decrease in the strength of the stem-cement interface after the dynamic test, and the weak bone composite exhibited a greater reduction in interfacial strength than the strong bone composite. The decrease of the interfacial strength indicates that the primary bonding between the stem and the cement mantle had deteriorated and the integrity of stem-cement interface was damaged. The study demonstrates the value of using a hip joint simulator to investigate stem migration and interface integrity within the cemented hip replacement, suggesting that method can be used for in vitro evaluation of the biomaterials used in the cemented hip replacements.展开更多
Affected by the limited interchange spacing,the operational risk of vehicles in expressway small-spacing interchanges(SSIs)is more complex compared to other interchanges.In this study,unmanned aerial vehicle(UAV)measu...Affected by the limited interchange spacing,the operational risk of vehicles in expressway small-spacing interchanges(SSIs)is more complex compared to other interchanges.In this study,unmanned aerial vehicle(UAV)measurements were integrated with joint simulation data to explore the risk characteristics of SSIs with the help of traffic conflict theory.Seven traffic flow parameters,including mainline traffic volume,were selected to evaluate their impact on traffic conflicts.The distribution of four traffic conflict indicators,such as time to collision(TTC),was analyzed,and their severity was categorized using cumulative frequency analysis and minibatch K-means clustering.By varying the spacing,the study scrutinized trends in traffic conflicts,emphasizing the influence of various traffic flow parameters,distinctions in conflict indicators,and the ratio of severe conflicts to total conflicts.Additionally,an analysis of the spatial distribution of severe conflicts was conducted.The results suggested that traffic conflicts in SSIs are influenced by multiple factors,with mainline and entry traffic volumes being the most significant.Heavy vehicle proportions and entry ramp speeds had notable effects under certain spacing conditions.Considerable variations were observed in conflict indicators across different spacings,with the maximum conflict speed being the most affected by spacing,while TTC was the least.As spacing increased,the proportion of severe conflicts decreased,with severe TTC dropping from 18%to 10%.High-density conflict zones were identified near merging points in the second and third lanes.With larger spacing,the conflict zone range narrowed while the density of conflict points intensified.展开更多
Fast mechanical switches(FMSs)are critical components of DC circuit breakers(DCCBs),which require the switch action time to break to a sufficient distance within 3 ms in the DC line breaking scenario,while ensuring a ...Fast mechanical switches(FMSs)are critical components of DC circuit breakers(DCCBs),which require the switch action time to break to a sufficient distance within 3 ms in the DC line breaking scenario,while ensuring a long service life.The breaking mechanism significantly affects the current interruption capability of DCCBs.The operation of the repulsion mechanism,along with the morphology of the arc and its transformation within the interrupter chamber,collectively influence the breaking performance of the FMSs.This paper presents a comprehensive analysis of the FMSs,which serves as the pivotal component of controlled resonance combination circuit breakers(CRCBs).This study establishes a multi physics coupling simulation analysis method based on the equivalent circuit of repulsion mechanism discharge,combined with electromagnetic and solid mechanics fields.By constructing a full cycle magnetohydrodynamic particle arc(MHP)model and using a combined simulation of Finite Element joint model(FEJM),the evolution law of arc characteristics during the superimposed current interruption process was systematically explored.The focus was on analysing the physical process of the zero zone of the superimposed arc,the multi physics field coupling relationship of the arc,and the interaction mechanism with external characteristic parameters.Further combining with optimisation design methods,the effectiveness of the model was verified through experiments,FEJM provides comprehensive technical support for effectively reflecting the stress issues of core components during the breaking process of FMS and can provide accurate theoretical references for the optimisation design of mechanical motion components in FMS.It also accurately represents the arc extinguishing process during the breaking of FMS and provides a convenient method for the selection and design of circuit parameters for the entire circuit breaker.展开更多
文摘In the field of optoelectronics,certain types of data may be difficult to accurately annotate,such as high-resolution optoelectronic imaging or imaging in certain special spectral ranges.Weakly supervised learning can provide a more reliable approach in these situations.Current popular approaches mainly adopt the classification-based class activation maps(CAM)as initial pseudo labels to solve the task.
基金Financial support from the National Natural Science Foundation of China(No.50978251)the National Government Building High-Level University Graduate Programs of the China Scholarship Council
文摘A Double Shear Model(DSM) was used in a numerical simulation on bolted rock joint shearing performance.An entire bolt deformed as the letter'U'under a shear load between two joints.Near the bolt-joint intersection,the bolt partly deformed as the letter'Z'.There were two critical points along the bolt:one was at the bolt-joint intersection with zero bending moment and the other at the maximum bending moment(plastic hinge) with zero shear stress.The blocks on two sides slid along the bolt as it deformed. A separation area was found between the two joint contact surfaces of the middle rock block and sided block.This area of separation was related to bolt diameter and external forces.We assume that this area is related to the work of external forces.Further research is needed.
文摘The 3D FEM numerical simulation on multi-action precision cold forging technology of universal joint cross and differential spider is done in this article using DEFORM Software, a commercial computer aided engineering software specializing in forming and heat treatment simulation technology, and suitable for cold, warm and hot forging process. The material flow properties, the dynamic variation of stress and strain in the process of deformation and the load-stroke curve have also been achieved. A good consistency is exhibited between simulation results and practical data. Based on the DEFORM simulation results, the optimized procedure has been found for forging a universal joint cross. What should be emphasized here is that a better understanding of practical forging characters and the environmental factors can greatly improve the simulation accuracy thus make the simulation results more reliable.
基金supported by the Science Fund for Creative Research Groups of the National Natural ScienceFoundation of China (Grant No. 51021004)the National High Technology Research and DevelopmentProgram of China (863 Program, Grants No. 2012AA112509 and 2012AA051702)
文摘The joint probability distribution of wind speed and significant wave height in the Bohai Bay was investigated by comparing the Gurnbel logistic model, the Gumbel-Hougaard （GH） copula function, and the Clayton copula function. Twenty years of wind data from 1989 to 2008 were collected from the European Centre for Medium-Range Weather Forecasts （ECMWF） database and the blended wind data of the Quick Scatterometer （QSCAT） satellite data set and re-analysis data from the United States National Centers for Environmental Prediction （NCEP）. Several typhoons were taken into account and merged with the background wind fields from the ECMWF or QSCAT/NCEP database. The 20-year data of significant wave height were calculated with the unstructured-grid version of the third-generation wind wave model Simulating WAves Nearshore （SWAN） under extreme wind process conditions. The Gumbel distribution was used for univariate and marginal distributions. The distribution parameters were estimated with the method of L-moments. Based on the marginal distributions, the joint probability distributions, the associated return periods, and the conditional probability distributions were obtained. The GH copula function was found to be optimal according to the ordinary least squares （OLS） test. The results show that wind waves are the prevailing type of wave in the Bohai Bay.
基金supported by the National Natural Science Foundation of China(No.10702048).
文摘Based on CT scanning pictures from a volunteer＇s knee joint, a three-dimensional finite element model of the healthy human knee joint is constructed including complete femur, tibia, fibular, patellar and the main cartilage and ligaments. This model was validated using experimental and numerical results obtained from other authors. The pressure distribution of contact surfaces of knee joint are calculated and analyzed under the load action of ‘heel strike＇, ‘single limb stance＇ and ‘toe-off＇. The results of the gait cycle are that the contact areas of medial cartilage are larger than that of lateral cartilage; the contact force and contact areas would grow larger with the load increasing; the pressure of lateral meniscus is steady, relative to the significant variation of peak pressure in medial meniscus; and the peak value of contact pressure on all components are usually found at about 4570 of the gait cycle.
基金Project(2009318000046) supported by the Western Transport Technical Program of the Ministry of Transport,China
文摘A revised displacement discontinuity method(DDM) program is developed for the simulation of rock joint propagation and dilatancy analysis. The non-linear joint model used in the program adopts Barton-Bandis normal deformation model, Kulhaway shear deformation model and Mohr-Coulomb criterion. The joint propagation criterion is based on the equivalent stress intensity factor which can be obtained by regression analysis. The simulated rock joint propagation accords well with the existing knowledge. The closure and opening of joint is investigated by DDM, and it is shown that if the opening volume of propagated joint is larger than closure volume of the old joint, the joint dilatancy occurs. The dilatancy condition is mainly controlled by the normal stiffness of the rock joint. When the normal stiffness is larger than the critical value, joint dilatancy occurs. The critical normal stiffness of rock joint changes with the joint-load angle, and joint dilatancy is most possible to occur at 30°.
基金supported by the National Natural Science Foundation of China(NSFC)(41941018).
文摘2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.
基金support from the National Natural Science Foundation of China(Grant No.42176209)the Natural Science Foundation of Shandong Province(Grant No.ZR2021MD064)the Fundamental Research Funds for the Central Universities(Grant No.19CX05001A).
文摘The corrosion behavior of B10 copper-nickel alloy welded joints in seawater pipeline system was analyzed under local turbulence induced by weld residual height.The corrosion behavior was evaluated by array electrode technology,mor-phology and elemental characterization,and COMSOL Multiphysics simulation.The results provide a theoretical basis for the corrosion and leakage of B10 alloy in seawater pipeline under the action of turbulence.The results show that residual height-induced turbulence exhibits a significant effect on the corrosion behavior in different areas of welded joints in B10 alloy.Turbulence can damage some surfaces,causing polarity deflection followed by acceleration of corrosion,or it is easier to form a protective film to slow down corrosion.COMSOL Multiphysics results show that the shear rate and turbulent kinetic energy increase linearly with the increase in residual height and velocity.The corrosion behavior of alloy surface is influenced by controlling the mass transfer rate and surface state.
文摘Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of temperature cycling profile parameters. The results show that temperature cycling history has significant effect on the stress response of the solder joint. Based on the concept of relative damage stress proposed by the authors, it is found that enough high temperature holding time is necessary for designing the temperature cycling profile in accelerated thermal fatigue test.
文摘The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.
文摘The analysis of the impulse voltage on the internal electric field of the cable joint plays a key role in studying the breakdown of the joint. Based on the finite element method, a three-dimensional electromagnetic field simulation model of the cable joint is established in this paper. Simulation results show that the voltage at the head of the cable joint reaches about twice the impulse voltage. The increase of the conductivity of semi-conductive material also leads to the increase of electric field intensity. Then, several points and curves at different positions are selected for further analysis in this paper. Among them, the electric field distortion at the edge of the high voltage shield is the most serious and the electric field in the air gap is the least.
基金supported by the National Natural Science Foundation of China(Grant Number 52001141).
文摘Pinless friction stir spot welding(P-FSSW)was performed to manufacture Mg/steel lap joints.Orthogonal tests for P-FSSW of Mg/steel were investigated,and the main factors affecting the properties of Mg/steel lap joints were derived.The shear force of the Mg/steel lap joints gradually increased and then decreased as the welding time increased.Maximum shear force was 5.3 kN.Fe-Al intermetallic compound(IMC)was formed at the Mg/steel interface near the steel side,and Mg-Al IMCs were formed at the Mg/steel interface near the Mg alloy side.Mg/steel lap joint was transformed from an initial solid-state welding to fusion-brazing welding as the welding time increased.No hole defects were formed in Mg/steel solid-state welding joints,whereas hole defects appeared in Mg/steel fusion-brazing welding joints.The temperature field of Mg/steel lap joints was simulated to analyze hole defects generated during the welding process.Hole defects can be eliminated by changing the spindle deflection angle,and the shear force decreased.Excessive spindle deflection can also lead to failure to form a stable joint.Hole defects were removed because the spindle deflection angle reduced the interfacial reaction temperature,and a solid-state welding joint was formed,which resulted in an absence of fusion-brazing welding hole formation.
基金supported by the National Natural Science Foundation of China(Grant No.50979069)the Science and Technology Project of West China Traffic Construction(Grant No.200632800003-06)
文摘Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation coupled motion,the horizontal vibrating-uplift rocking coupled motion,and the horizontal sliding-uplift rocking coupled motion.The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson.The numerical models of four motion modes of caisson are developed,and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment.It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.
文摘With the development of ocean engineering, it is one of the most important factors which determine the structural safety, cost and suitable forms of engineerings to select the ocean environmental design criteria. Owing to the complexity , variation and randomness of ocean environmental conditions, the commonly used methods for determining design criteria cannot consider the joint occurring probabilities of several environmental factors ,therefore, lead to overestimate design criteria of them and result in an unnecessary overspend invest in engineering. On the basis of the measured and hindcasting data and the multi-demension joint probability theory, this paper presented the study of the joint loads of wind , wave and current on the offshore structures and its responsible joint probability level with the application of random simulation techniques, and presented the joint design criteria of environmental loads for the realistic design of engineerings.
文摘A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion plane, with a socket to rotate internal/externally. At the same time a dynamic loading cycle is applied. A validation test was performed on a cemented femoral stem within a novel composite femur. The hone quality has a strong effect on the stem migration and on the integrity of the interfaces. The migration of the stem is a combination of 3-D translation and rotation of the stem. Under the same loading conditions, weak bone allows more stem migration than strong bone. There is a great decrease in the strength of the stem-cement interface after the dynamic test, and the weak bone composite exhibited a greater reduction in interfacial strength than the strong bone composite. The decrease of the interfacial strength indicates that the primary bonding between the stem and the cement mantle had deteriorated and the integrity of stem-cement interface was damaged. The study demonstrates the value of using a hip joint simulator to investigate stem migration and interface integrity within the cemented hip replacement, suggesting that method can be used for in vitro evaluation of the biomaterials used in the cemented hip replacements.
基金supported in part by the National Natural Science Foundation of China(No.52172340).
文摘Affected by the limited interchange spacing,the operational risk of vehicles in expressway small-spacing interchanges(SSIs)is more complex compared to other interchanges.In this study,unmanned aerial vehicle(UAV)measurements were integrated with joint simulation data to explore the risk characteristics of SSIs with the help of traffic conflict theory.Seven traffic flow parameters,including mainline traffic volume,were selected to evaluate their impact on traffic conflicts.The distribution of four traffic conflict indicators,such as time to collision(TTC),was analyzed,and their severity was categorized using cumulative frequency analysis and minibatch K-means clustering.By varying the spacing,the study scrutinized trends in traffic conflicts,emphasizing the influence of various traffic flow parameters,distinctions in conflict indicators,and the ratio of severe conflicts to total conflicts.Additionally,an analysis of the spatial distribution of severe conflicts was conducted.The results suggested that traffic conflicts in SSIs are influenced by multiple factors,with mainline and entry traffic volumes being the most significant.Heavy vehicle proportions and entry ramp speeds had notable effects under certain spacing conditions.Considerable variations were observed in conflict indicators across different spacings,with the maximum conflict speed being the most affected by spacing,while TTC was the least.As spacing increased,the proportion of severe conflicts decreased,with severe TTC dropping from 18%to 10%.High-density conflict zones were identified near merging points in the second and third lanes.With larger spacing,the conflict zone range narrowed while the density of conflict points intensified.
基金State Grid Corporation Headquarters Science and Technology Project,Grant/Award Number:5500-20220110A-1-1-ZN。
文摘Fast mechanical switches(FMSs)are critical components of DC circuit breakers(DCCBs),which require the switch action time to break to a sufficient distance within 3 ms in the DC line breaking scenario,while ensuring a long service life.The breaking mechanism significantly affects the current interruption capability of DCCBs.The operation of the repulsion mechanism,along with the morphology of the arc and its transformation within the interrupter chamber,collectively influence the breaking performance of the FMSs.This paper presents a comprehensive analysis of the FMSs,which serves as the pivotal component of controlled resonance combination circuit breakers(CRCBs).This study establishes a multi physics coupling simulation analysis method based on the equivalent circuit of repulsion mechanism discharge,combined with electromagnetic and solid mechanics fields.By constructing a full cycle magnetohydrodynamic particle arc(MHP)model and using a combined simulation of Finite Element joint model(FEJM),the evolution law of arc characteristics during the superimposed current interruption process was systematically explored.The focus was on analysing the physical process of the zero zone of the superimposed arc,the multi physics field coupling relationship of the arc,and the interaction mechanism with external characteristic parameters.Further combining with optimisation design methods,the effectiveness of the model was verified through experiments,FEJM provides comprehensive technical support for effectively reflecting the stress issues of core components during the breaking process of FMS and can provide accurate theoretical references for the optimisation design of mechanical motion components in FMS.It also accurately represents the arc extinguishing process during the breaking of FMS and provides a convenient method for the selection and design of circuit parameters for the entire circuit breaker.
