The widespread adoption of aluminumalloy electric buses,known for their energy efficiency and eco-friendliness,faces a challenge due to the aluminum frame’s susceptibility to deformation compared to steel.This issue ...The widespread adoption of aluminumalloy electric buses,known for their energy efficiency and eco-friendliness,faces a challenge due to the aluminum frame’s susceptibility to deformation compared to steel.This issue is further exacerbated by the stringent requirements imposed by the flammability and explosiveness of batteries,necessitating robust frame protection.Our study aims to optimize the connectors of aluminum alloy bus frames,emphasizing durability,energy efficiency,and safety.This research delves into Multi-Objective Coordinated Optimization(MCO)techniques for lightweight design in aluminum alloy bus body connectors.Our goal is to enhance lightweighting,reinforce energy absorption,and improve deformation resistance in connector components.Three typical aluminum alloy connectors were selected and a design optimization platform was built for their MCO using a variety of software and methods.Firstly,through three-point bending experiments and finite element analysis on three types of connector components,we identified optimized design parameters based on deformation patterns.Then,employing Optimal Latin hypercube design(OLHD),parametric modeling,and neural network approximation,we developed high-precision approximate models for the design parameters of each connector component,targeting energy absorption,mass,and logarithmic strain.Lastly,utilizing the Archive-based Micro Genetic Algorithm(AMGA),Multi-Objective Particle Swarm Optimization(MOPSO),and Non-dominated SortingGenetic Algorithm(NSGA2),we explored optimized design solutions for these joint components.Subsequently,we simulated joint assembly buckling during bus rollover crash scenarios to verify and analyze the optimized solutions in three-point bending simulations.Each joint component showcased a remarkable 30%–40%mass reduction while boosting energy absorption.Our design optimization method exhibits high efficiency and costeffectiveness.Leveraging contemporary automation technology,the design optimization platform developed in this study is poised to facilitate intelligent optimization of lightweight metal components in future applications.展开更多
This paper describes the quasi-static testing and analytical modelling of the hysteretic behavior of aluminum alloy rigid bus-flexible connectors of 220 kV electrical substations.The main objective of the study is to ...This paper describes the quasi-static testing and analytical modelling of the hysteretic behavior of aluminum alloy rigid bus-flexible connectors of 220 kV electrical substations.The main objective of the study is to experimentally investigate the hysteretic behavior of six different types of rigid bus-flexible connectors 220 kV electrical substations when subjected to cyclic loading.Another objective is to theoretically study the flexibility and effectiveness of a previously proposed analytical model in fitting the experimental hysteresis loops of the tested rigid bus-flexible connectors.The experimental investigation indicates that the tested rigid bus-flexible connectors exhibit highly asymmetric hysteresis behavior along with tension stiffening effect.The theoretical study demonstrates that the generalized Bouc-Wen model has high flexibility and is effective in fitting the experimental hysteresis resisting force-displacement curves of the six tested rigid bus-flexible connectors.展开更多
A Mobile Offshore Base (MOB) is a multi-purpose logistics base, which can be stationed in coastal or international waters. In the conceptual design of the MOB, attention should be paid to the dynamic responses of the ...A Mobile Offshore Base (MOB) is a multi-purpose logistics base, which can be stationed in coastal or international waters. In the conceptual design of the MOB, attention should be paid to the dynamic responses of the inter-module connectors because tremendous loads occur in the connectors. In this paper, a study on dynamic responses of the MOB connectors is carried out by use of the Rigid Module Flexible Connector (RMFC) model which assumes that the module stiffness is significantly larger than that of the connector. In the analysis, the connector is modeled as a linear spring, which restricts relative translations but allows for relative rotations of modules. The 3-D source distribution method is adopted to determine the hydrodynamic forces of the modules, and the hydrodynamic interaction between modules is taken into account. The module motions and connector loads for 12 connector stiffness cases in regular and irregular waves are calculated with the multi-rigid-body motion equations. And the calculated results are compared with those from relative references. It is shown that the results obtained by different methods are in good agreement.展开更多
Combined multi-body dynamics with structural dynamics,a new discrete element with flexibleconnector,which is applicable for 3-D beam structures,is developed in this paper.Both the generalizedelastic coefficient matrix...Combined multi-body dynamics with structural dynamics,a new discrete element with flexibleconnector,which is applicable for 3-D beam structures,is developed in this paper.Both the generalizedelastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diag-onal in a general case.The zero-length rigid element is introduced to simulate the node at which multiple el-ements are jointed together.It may also be effective when the axes of adjacent elements are not in the sameline.The examples for eigenvalue calculation show that the model is successful.It can be extended to thegeometric nonlinear response analysis.展开更多
The application of fi ber-reinforced polymer (FRP) composites for the development of high-performance composite structural systems has received signifi cant recent research attention. A composite of FRP–recycled aggr...The application of fi ber-reinforced polymer (FRP) composites for the development of high-performance composite structural systems has received signifi cant recent research attention. A composite of FRP–recycled aggregate concrete (RAC)–steel column (FRSC), consisting of an outer FRP tube, an inner steel tube and annular RAC fi lled between two tubes, is proposed herein to facilitate green disposal of demolished concrete and to improve the ductility of concrete columns for earthquake resistance. To better understand the seismic behavior of FRSCs, quasi-static tests of large-scale basalt FRSCs with shear connectors were conducted. The infl uence of the recycled coarse aggregate (RCA) replacement percentage, shear connectors and axial loading method on the lateral load and deformation capacity, energy dissipation and cumulative damage were analyzed to evaluate the seismic behavior of FRSCs. The test results show that FRSCs have good seismic behavior, which was evidenced by high lateral loads, excellent ductility and energy dissipation capacity, indicating RAC is applicable in FRSCs. Shear connectors can signifi cantly postpone the steel buckling and increase the lateral loads of FRSCs, but weaken the deformation capacity and energy dissipation performance.展开更多
This paper investigates a simplified method to determine the optimal stiffness of flexible connectors on a mobile offshore base(MOB) during the preliminary design stage. A three-module numerical model of an MOB was us...This paper investigates a simplified method to determine the optimal stiffness of flexible connectors on a mobile offshore base(MOB) during the preliminary design stage. A three-module numerical model of an MOB was used as a case study. Numerous constraint forces and relative displacements for the connectors at rough sea states with different wave angles were utilized to determine the optimized stiffness of the flexible connectors. The range of optimal stiffnesses for the connectors was obtained based on the combination and intersection of the optimized stiffness results, and the implementation steps were elaborated in detail. The percentage reductions of the optimized and optimal stiffness of the flexible connector were determined to quantitatively evaluate the decreases of the constraint force and relative displacement of the connectors compared with those calculated by using the original range of the connector stiffnesses. The results indicate the accuracy and feasibility of this method for determining the optimal stiffness of the flexible connectors and demonstrate the rationality and practicability of the optimal stiffness results. The research ideas, calculation process, and solutions for the optimal stiffness of the flexible connectors of an MOB in this paper can provide valuable technical support for the design of the connectors in similar semisubmersible floating structures.展开更多
Researchers seldom study the optimum design of a mechanical connector for subsea oil-gas pipeline based upon the sealing performance. An optimal design method of a novel subsea pipeline mechanical connector is present...Researchers seldom study the optimum design of a mechanical connector for subsea oil-gas pipeline based upon the sealing performance. An optimal design method of a novel subsea pipeline mechanical connector is presented. By analyzing the static metal sealing mechanism, the critical condition of the sealing performance is established for this connector and the formulation method of the contact pressure on the sealing surface is created. By the method the minimum mean contact pressure of the 8.625 inch connector is calculated as 361 MPa, which is the constraint condition in the optimum design of connector.The finite element model is created in ANSYS Parametric Design Language(APDL) and the structure is optimized by the zero-order method, with variance of contact pressure as the objective function, and mean contact pressures and plastic strains as constraint variables. The optimization shows that variances of contact pressure on two sealing surfaces decrease by 72.41% and 89.33%, respectively, and mean contact pressures increase by 31.18% and 52.84%, respectively. The comparison of the optimal connectors and non-optimal connectors in the water pressure experiments and bending experiments shows that the sealing ability of optimized connectors is much higher than the rated pressure of 4.5 MPa, and the optimal connectors don't leak under the bending moment of 52.2 kN·m.This research provides the formulation to solve contact pressure on the sealing surface and a structure optimization method to design the connectors with various dimensions.展开更多
Since the previous strength prediction models for the perfobond rib connector were proposed based upon the results of push-out tests conducted on concretes with compressive strength below 50 MPa, push-out test is perf...Since the previous strength prediction models for the perfobond rib connector were proposed based upon the results of push-out tests conducted on concretes with compressive strength below 50 MPa, push-out test is performed on perfobond shear connectors applying ultra high performance concretes with compressive strength higher than 80 MPa to evaluate their shear resistance. The test variables are chosen to be the diameter and number of dowel holes and, the change in the shear strength of the perfobond rib connector is examined with respect to the strength of two types of UHPC: steel fiber-reinforced concrete with compressive strength of 180 MPa and concrete without steel fiber with compressive strength of 80 MPa. The test results reveal that higher concrete strength and larger number of holes increased the shear strength, and that higher increase rate in the shear strength was achieved by the dowel action. The comparison with the predictions obtained by the previous models shows that the experimental results are close to the values given by the model proposed by Oguejiofor and Hosain [1].展开更多
Libraries at large academic medical centers in the United States are undergoing a transformation from their traditional role as knowledge repositories to a new role as connectors to knowledge. This transformation is f...Libraries at large academic medical centers in the United States are undergoing a transformation from their traditional role as knowledge repositories to a new role as connectors to knowledge. This transformation is fueled by the move away from library-held print resources as the primary source of information used by researchers,clinicians and students. Knowledge resources critical to the missions of academic medical centers now include online books and journals,very large data sets,software tools,and expertise far beyond the walls of the library. This article illustrates how Bernard Becker Medical Library at Washington University in St. Louis has seized the opportunity to recast itself as a connector to knowledge beyond literature and strengthen its vital role within the university as a catalyst for learning and discovery.展开更多
Based on the bent ligand 1 H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole(3,4?-Hbpt) with Co(Ⅱ) ions as well as a series of polycarboxylate co-ligands, three new coordination polymers were yielded, namely, {[Co(op)(3,4...Based on the bent ligand 1 H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole(3,4?-Hbpt) with Co(Ⅱ) ions as well as a series of polycarboxylate co-ligands, three new coordination polymers were yielded, namely, {[Co(op)(3,4?-Hbpt)(H_2O)_3]?2 H_2O}n(1), [Co(cyc)(3,4′-Hbpt)(H_2O)]n(2) and [Co(pro)(3,4′-Hbpt)(H_2O)]n(3)(here, op = o-phthalic anion, cyc = 1,1-cyclobutanedicarboxylic anion, pro = propanedioic anion). In cooperation with the auxiliary polycarboxylate co-ligands, a variety of Co(Ⅱ) coordination networks, such as 1-D chain 1 and 2-D layer 2 and 3 have been assembled. The magnetic behaviors of compounds 1～3 were studied. All of them indicated the existence of interesting spin-canting behavior.展开更多
There are two connection modes between escalator step and step drive chain of outer roller,connector type A and type B.Connector type B after a period of running was found that the fixing bolt on the connector has loo...There are two connection modes between escalator step and step drive chain of outer roller,connector type A and type B.Connector type B after a period of running was found that the fixing bolt on the connector has loosened,which causes safety risks.In order to eliminate this security issue,the finite element modeling is proposed to analyze the relationship between the force generated by the connector type A or type B during the step band running and the assembly clearance or the assembly mode.So as to find out the root cause of fixing bolt loosening phenomenon,by redesigning the assembly clearance between the connector shaft and the chain hole,the fixing bolt of the connector is prevented from loosening during the step band running,ensuring the safe operation of escalators to avoid injury accidents.展开更多
The present work reports a Hybrid Modular Floating Structure(HMFS)system with typical malfunction conditions.The effects of both fractured mooring lines and failed connectors on main hydrodynamic responses(mooring lin...The present work reports a Hybrid Modular Floating Structure(HMFS)system with typical malfunction conditions.The effects of both fractured mooring lines and failed connectors on main hydrodynamic responses(mooring line tensions,module motions,connector loads and wave power production)of the HMFS system under typical sea con-ditions are comparatively investigated.The results indicate that the mooring tension distribution,certain module motions(surge,sway and yaw)and connector loads(Mz)are significantly influenced by mooring line fractures.The adjacent mooring line of the fractured line on the upstream side suffers the largest tension among the remaining mooring lines,and the case with two fractured mooring lines in the same group on the upstream side is the most dangerous among all cases of two-line failures in view of mooring line tensions,module motions and connector loads.There-fore,one emergency strategy with appropriate relaxation of a proper mooring line has been proposed and proved effective to reduce the risk of more progressive mooring line fractures.In addition,connector failures substantially affect certain module motions(heave and pitch),certain connector loads(Fz and My)and wave power production.The present work can be helpful and instructive for studies on malfunction conditions of modular floating structure(MFS)systems.展开更多
Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC compo...Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC composite decks was investigated by conducting push⁃out tests.The test parameter is the presence of reinforcement in the deck.The load⁃slip curves and shear behavior of the push⁃out specimens were obtained and discussed.The test results indicate that as compared with plain concrete specimens,the limit slip of reinforced specimens decreased by 32%and the shear stiffness increased by 10%,but the ultimate shear capacity was almost the same.The use of UHPC influenced the failure process as it was observed that the OST connector was sheared off at its lower semi⁃tube,followed by the pull⁃out failure of the upper semi⁃tube.A finite element model was verified by tests and was then used to analyze the deformation and failure behaviors of the composite deck with open tubes.The model demonstrates that there is a stress concentration zone at the connector root,and the lower semi⁃tube is the main component that is subject to loads.展开更多
Subsea wellhead connector is the key equipment for offshore oil and gas production. The working water depth is generally more than 500 m, so it has higher requirements for its sealing performance. In this paper, the V...Subsea wellhead connector is the key equipment for offshore oil and gas production. The working water depth is generally more than 500 m, so it has higher requirements for its sealing performance. In this paper, the VX gasket matched with H-4 subsea wellhead connector is taken as the research object, and the mechanical analysis under preload and production conditions is carried out. The finite element model of subsea wellhead connector is established by ABAQUS software, and the influence of axial preload, production pressure and material properties on the sealing performance of VX gasket is studied. The results show that the greater the axial preload, the greater the contact stress on the gasket surface;the contact stress decreases first and then increases linearly with the increase of production pressure;the material properties of the gasket are also an important factor affecting its sealing performance, 316L stainless steel is more suitable for gasket material than 304 stainless steel and Inconel625.展开更多
As few or no failures occur during accelerated life test,it is difficult to assess reliability for long-life products with traditional life tests.Reliability assessment using degradation data of product performance ov...As few or no failures occur during accelerated life test,it is difficult to assess reliability for long-life products with traditional life tests.Reliability assessment using degradation data of product performance over time becomes a significant approach.Aerospace electrical connector is researched in this paper.Through the analysis of failure mechanism,the performance degradation law is obtained and the statistical model for degradation failure is set up;according to the research on statistical analysis methods for degradation data,accelerated life test theory and method for aerospace electrical connector based on performance degradation is proposed by improving time series analysis method,and the storage reliability is assessed for Y11X series of aerospace electrical connector with degradation data from accelerated degradation test.The result obtained is basically consistent with that obtained from accelerated life test based on failure data,and the two estimates of product's characteristic life only have a difference of 8.7%,but the test time shortens about a half.As a result,a systemic approach is proposed for reliability assessment of highly reliable and long-life aerospace product.展开更多
The metal sealing performance of subsea X-tree wellhead connectors is crucial for the safety and reliability of subsea X-trees. In order to establish the theoretical relation between metal sealing ring's contact s...The metal sealing performance of subsea X-tree wellhead connectors is crucial for the safety and reliability of subsea X-trees. In order to establish the theoretical relation between metal sealing ring's contact stress and its structural parameters and working pressure, a mechanical analysis method for double-cone sealing of high pressure vessels is applied in analyzing the metal sealing ring under the condition of preload and operation. As a result, the formula of the unit sealing load for the metal sealing ring under operation with residual preload is shown in this paper, which ensures that the metal sealing ring has an excellent sealing effect and can prevent the metal sealing ring from yielding. Besides, while analyzing the sealing process of the metal sealing ring, the change rule of contact stress and working pressure is concluded here, putting forward that the structural parameters of the metal sealing ring are the major factors affecting the change rule. Finally, the analytical solution through theoretical analysis is compared with the simulation result through finite element analysis in a force feedback experiment, and both are consistent with each other, which fully verifies for the design and calculation theory on metal sealing ring's contact stress and its structural parameters and working pressure deduced in this paper. The proposed research will be treated as an applicable theory guiding the design of metal seal for subsea X-tree wellhead connectors.展开更多
Thermal analysis and thermal diagnose are important for small power connector especially in electronic devices since their structure is usually compact. In this paper thermal behavior of small power connector was inve...Thermal analysis and thermal diagnose are important for small power connector especially in electronic devices since their structure is usually compact. In this paper thermal behavior of small power connector was investigated. It was found that the contact resistance increased due to the Joule heating, and that increased contact resistance produced more Joule heating; this mutual action causes the connector to lose efficiency. The thermal distribution in the connector was analyzed using finite element method (FEM). The failure mechanism is discussed. It provides basis for improving the structure. The conclusion was verified by experimental results.展开更多
Pin and socket contacts are the key parts of electrical connector as aerospace electronic components. The contacts are also the direct carriers for signal transmitting of electronic equipments, passing the signal from...Pin and socket contacts are the key parts of electrical connector as aerospace electronic components. The contacts are also the direct carriers for signal transmitting of electronic equipments, passing the signal from the input end to the output end of electrical connector. The reliability of pin and socket contacts directly influences signal transmission. The goal of this study is to enhance the contact reliability of aerospace electrical connector. Computer simulation analysis was made on contacts performance data by utilizing the simulation system developed by PCL Language of MSC software. Furthermore, the results were experi- mentally validated so as to realize the objective of optimizing contacts design.展开更多
基金the National Natural Science Foundation of China(Grant Number 52075553)the Postgraduate Research and Innovation Project of Central South University(School-Enterprise Association)(Grant Number 2021XQLH014).
文摘The widespread adoption of aluminumalloy electric buses,known for their energy efficiency and eco-friendliness,faces a challenge due to the aluminum frame’s susceptibility to deformation compared to steel.This issue is further exacerbated by the stringent requirements imposed by the flammability and explosiveness of batteries,necessitating robust frame protection.Our study aims to optimize the connectors of aluminum alloy bus frames,emphasizing durability,energy efficiency,and safety.This research delves into Multi-Objective Coordinated Optimization(MCO)techniques for lightweight design in aluminum alloy bus body connectors.Our goal is to enhance lightweighting,reinforce energy absorption,and improve deformation resistance in connector components.Three typical aluminum alloy connectors were selected and a design optimization platform was built for their MCO using a variety of software and methods.Firstly,through three-point bending experiments and finite element analysis on three types of connector components,we identified optimized design parameters based on deformation patterns.Then,employing Optimal Latin hypercube design(OLHD),parametric modeling,and neural network approximation,we developed high-precision approximate models for the design parameters of each connector component,targeting energy absorption,mass,and logarithmic strain.Lastly,utilizing the Archive-based Micro Genetic Algorithm(AMGA),Multi-Objective Particle Swarm Optimization(MOPSO),and Non-dominated SortingGenetic Algorithm(NSGA2),we explored optimized design solutions for these joint components.Subsequently,we simulated joint assembly buckling during bus rollover crash scenarios to verify and analyze the optimized solutions in three-point bending simulations.Each joint component showcased a remarkable 30%–40%mass reduction while boosting energy absorption.Our design optimization method exhibits high efficiency and costeffectiveness.Leveraging contemporary automation technology,the design optimization platform developed in this study is poised to facilitate intelligent optimization of lightweight metal components in future applications.
基金National Natural Science Foundation of China under Grant No.51978397。
文摘This paper describes the quasi-static testing and analytical modelling of the hysteretic behavior of aluminum alloy rigid bus-flexible connectors of 220 kV electrical substations.The main objective of the study is to experimentally investigate the hysteretic behavior of six different types of rigid bus-flexible connectors 220 kV electrical substations when subjected to cyclic loading.Another objective is to theoretically study the flexibility and effectiveness of a previously proposed analytical model in fitting the experimental hysteresis loops of the tested rigid bus-flexible connectors.The experimental investigation indicates that the tested rigid bus-flexible connectors exhibit highly asymmetric hysteresis behavior along with tension stiffening effect.The theoretical study demonstrates that the generalized Bouc-Wen model has high flexibility and is effective in fitting the experimental hysteresis resisting force-displacement curves of the six tested rigid bus-flexible connectors.
基金This work was finarcially supported by the National Natural Science Foundation of China(Grant No.50039016)
文摘A Mobile Offshore Base (MOB) is a multi-purpose logistics base, which can be stationed in coastal or international waters. In the conceptual design of the MOB, attention should be paid to the dynamic responses of the inter-module connectors because tremendous loads occur in the connectors. In this paper, a study on dynamic responses of the MOB connectors is carried out by use of the Rigid Module Flexible Connector (RMFC) model which assumes that the module stiffness is significantly larger than that of the connector. In the analysis, the connector is modeled as a linear spring, which restricts relative translations but allows for relative rotations of modules. The 3-D source distribution method is adopted to determine the hydrodynamic forces of the modules, and the hydrodynamic interaction between modules is taken into account. The module motions and connector loads for 12 connector stiffness cases in regular and irregular waves are calculated with the multi-rigid-body motion equations. And the calculated results are compared with those from relative references. It is shown that the results obtained by different methods are in good agreement.
基金The project was financially supported by the National Natural Science Foundation of China
文摘Combined multi-body dynamics with structural dynamics,a new discrete element with flexibleconnector,which is applicable for 3-D beam structures,is developed in this paper.Both the generalizedelastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diag-onal in a general case.The zero-length rigid element is introduced to simulate the node at which multiple el-ements are jointed together.It may also be effective when the axes of adjacent elements are not in the sameline.The examples for eigenvalue calculation show that the model is successful.It can be extended to thegeometric nonlinear response analysis.
基金National Natural Science Foundation of China under Grant No.11472084Science and Technology Project of Guangdong Province under Grant No.2017B020238006+1 种基金Science and Technology Planning Project of Guangzhou City under Grant No.201704030057Fundamental Research Funds for the Central Universities under Grant No.21619327
文摘The application of fi ber-reinforced polymer (FRP) composites for the development of high-performance composite structural systems has received signifi cant recent research attention. A composite of FRP–recycled aggregate concrete (RAC)–steel column (FRSC), consisting of an outer FRP tube, an inner steel tube and annular RAC fi lled between two tubes, is proposed herein to facilitate green disposal of demolished concrete and to improve the ductility of concrete columns for earthquake resistance. To better understand the seismic behavior of FRSCs, quasi-static tests of large-scale basalt FRSCs with shear connectors were conducted. The infl uence of the recycled coarse aggregate (RCA) replacement percentage, shear connectors and axial loading method on the lateral load and deformation capacity, energy dissipation and cumulative damage were analyzed to evaluate the seismic behavior of FRSCs. The test results show that FRSCs have good seismic behavior, which was evidenced by high lateral loads, excellent ductility and energy dissipation capacity, indicating RAC is applicable in FRSCs. Shear connectors can signifi cantly postpone the steel buckling and increase the lateral loads of FRSCs, but weaken the deformation capacity and energy dissipation performance.
基金financially supported by the National Key Research and Development Program of China(Grant Nos.2016YFC0802204and 2016YFC0802201)the National Natural Science Foundation of China(Grant No.51679166)+2 种基金the National Natural Science Fund for Innovative Research Groups Science Foundation(Grant No.51321065)the Construction Science and Technology Project of the Ministry of Transport of the People’s Republic of China(Grant No.2014328224040)the Innovative Research Program for Graduate Students at Chongqing Jiaotong University(Grant No.20140104)
文摘This paper investigates a simplified method to determine the optimal stiffness of flexible connectors on a mobile offshore base(MOB) during the preliminary design stage. A three-module numerical model of an MOB was used as a case study. Numerous constraint forces and relative displacements for the connectors at rough sea states with different wave angles were utilized to determine the optimized stiffness of the flexible connectors. The range of optimal stiffnesses for the connectors was obtained based on the combination and intersection of the optimized stiffness results, and the implementation steps were elaborated in detail. The percentage reductions of the optimized and optimal stiffness of the flexible connector were determined to quantitatively evaluate the decreases of the constraint force and relative displacement of the connectors compared with those calculated by using the original range of the connector stiffnesses. The results indicate the accuracy and feasibility of this method for determining the optimal stiffness of the flexible connectors and demonstrate the rationality and practicability of the optimal stiffness results. The research ideas, calculation process, and solutions for the optimal stiffness of the flexible connectors of an MOB in this paper can provide valuable technical support for the design of the connectors in similar semisubmersible floating structures.
基金Supported by National Natural Science Foundation of China(Grant Nos.51279042,51105088)
文摘Researchers seldom study the optimum design of a mechanical connector for subsea oil-gas pipeline based upon the sealing performance. An optimal design method of a novel subsea pipeline mechanical connector is presented. By analyzing the static metal sealing mechanism, the critical condition of the sealing performance is established for this connector and the formulation method of the contact pressure on the sealing surface is created. By the method the minimum mean contact pressure of the 8.625 inch connector is calculated as 361 MPa, which is the constraint condition in the optimum design of connector.The finite element model is created in ANSYS Parametric Design Language(APDL) and the structure is optimized by the zero-order method, with variance of contact pressure as the objective function, and mean contact pressures and plastic strains as constraint variables. The optimization shows that variances of contact pressure on two sealing surfaces decrease by 72.41% and 89.33%, respectively, and mean contact pressures increase by 31.18% and 52.84%, respectively. The comparison of the optimal connectors and non-optimal connectors in the water pressure experiments and bending experiments shows that the sealing ability of optimized connectors is much higher than the rated pressure of 4.5 MPa, and the optimal connectors don't leak under the bending moment of 52.2 kN·m.This research provides the formulation to solve contact pressure on the sealing surface and a structure optimization method to design the connectors with various dimensions.
文摘Since the previous strength prediction models for the perfobond rib connector were proposed based upon the results of push-out tests conducted on concretes with compressive strength below 50 MPa, push-out test is performed on perfobond shear connectors applying ultra high performance concretes with compressive strength higher than 80 MPa to evaluate their shear resistance. The test variables are chosen to be the diameter and number of dowel holes and, the change in the shear strength of the perfobond rib connector is examined with respect to the strength of two types of UHPC: steel fiber-reinforced concrete with compressive strength of 180 MPa and concrete without steel fiber with compressive strength of 80 MPa. The test results reveal that higher concrete strength and larger number of holes increased the shear strength, and that higher increase rate in the shear strength was achieved by the dowel action. The comparison with the predictions obtained by the previous models shows that the experimental results are close to the values given by the model proposed by Oguejiofor and Hosain [1].
文摘Libraries at large academic medical centers in the United States are undergoing a transformation from their traditional role as knowledge repositories to a new role as connectors to knowledge. This transformation is fueled by the move away from library-held print resources as the primary source of information used by researchers,clinicians and students. Knowledge resources critical to the missions of academic medical centers now include online books and journals,very large data sets,software tools,and expertise far beyond the walls of the library. This article illustrates how Bernard Becker Medical Library at Washington University in St. Louis has seized the opportunity to recast itself as a connector to knowledge beyond literature and strengthen its vital role within the university as a catalyst for learning and discovery.
基金The project was supported by the National Natural Science Foundation of China(21461003)the Guangxi Natural Science Foundation of China(2016GXNSFFA380010 and 2016GXNSFAA380206)the Project of Guangxi Education Department(KY2016LX235)
文摘Based on the bent ligand 1 H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole(3,4?-Hbpt) with Co(Ⅱ) ions as well as a series of polycarboxylate co-ligands, three new coordination polymers were yielded, namely, {[Co(op)(3,4?-Hbpt)(H_2O)_3]?2 H_2O}n(1), [Co(cyc)(3,4′-Hbpt)(H_2O)]n(2) and [Co(pro)(3,4′-Hbpt)(H_2O)]n(3)(here, op = o-phthalic anion, cyc = 1,1-cyclobutanedicarboxylic anion, pro = propanedioic anion). In cooperation with the auxiliary polycarboxylate co-ligands, a variety of Co(Ⅱ) coordination networks, such as 1-D chain 1 and 2-D layer 2 and 3 have been assembled. The magnetic behaviors of compounds 1～3 were studied. All of them indicated the existence of interesting spin-canting behavior.
文摘There are two connection modes between escalator step and step drive chain of outer roller,connector type A and type B.Connector type B after a period of running was found that the fixing bolt on the connector has loosened,which causes safety risks.In order to eliminate this security issue,the finite element modeling is proposed to analyze the relationship between the force generated by the connector type A or type B during the step band running and the assembly clearance or the assembly mode.So as to find out the root cause of fixing bolt loosening phenomenon,by redesigning the assembly clearance between the connector shaft and the chain hole,the fixing bolt of the connector is prevented from loosening during the step band running,ensuring the safe operation of escalators to avoid injury accidents.
基金supported by Shenzhen Science and Technology Program(Grant No.KQTD20210811090112003)the National Natural Science Foundation of China(Grant No.52161041).
文摘The present work reports a Hybrid Modular Floating Structure(HMFS)system with typical malfunction conditions.The effects of both fractured mooring lines and failed connectors on main hydrodynamic responses(mooring line tensions,module motions,connector loads and wave power production)of the HMFS system under typical sea con-ditions are comparatively investigated.The results indicate that the mooring tension distribution,certain module motions(surge,sway and yaw)and connector loads(Mz)are significantly influenced by mooring line fractures.The adjacent mooring line of the fractured line on the upstream side suffers the largest tension among the remaining mooring lines,and the case with two fractured mooring lines in the same group on the upstream side is the most dangerous among all cases of two-line failures in view of mooring line tensions,module motions and connector loads.There-fore,one emergency strategy with appropriate relaxation of a proper mooring line has been proposed and proved effective to reduce the risk of more progressive mooring line fractures.In addition,connector failures substantially affect certain module motions(heave and pitch),certain connector loads(Fz and My)and wave power production.The present work can be helpful and instructive for studies on malfunction conditions of modular floating structure(MFS)systems.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51478120)。
文摘Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC composite decks was investigated by conducting push⁃out tests.The test parameter is the presence of reinforcement in the deck.The load⁃slip curves and shear behavior of the push⁃out specimens were obtained and discussed.The test results indicate that as compared with plain concrete specimens,the limit slip of reinforced specimens decreased by 32%and the shear stiffness increased by 10%,but the ultimate shear capacity was almost the same.The use of UHPC influenced the failure process as it was observed that the OST connector was sheared off at its lower semi⁃tube,followed by the pull⁃out failure of the upper semi⁃tube.A finite element model was verified by tests and was then used to analyze the deformation and failure behaviors of the composite deck with open tubes.The model demonstrates that there is a stress concentration zone at the connector root,and the lower semi⁃tube is the main component that is subject to loads.
文摘Subsea wellhead connector is the key equipment for offshore oil and gas production. The working water depth is generally more than 500 m, so it has higher requirements for its sealing performance. In this paper, the VX gasket matched with H-4 subsea wellhead connector is taken as the research object, and the mechanical analysis under preload and production conditions is carried out. The finite element model of subsea wellhead connector is established by ABAQUS software, and the influence of axial preload, production pressure and material properties on the sealing performance of VX gasket is studied. The results show that the greater the axial preload, the greater the contact stress on the gasket surface;the contact stress decreases first and then increases linearly with the increase of production pressure;the material properties of the gasket are also an important factor affecting its sealing performance, 316L stainless steel is more suitable for gasket material than 304 stainless steel and Inconel625.
基金supported by National Natural Science Foundation of China (Grant No. 50935002,Grant No. 51075370,Grant No. 51105341)National Hi-tech Research and Development Program of China (863 Program,Grant No. 2007AA04Z409)Civil Aerospace Science and Technology Pre-research Project of China (Grant No. B122006 2302)
文摘As few or no failures occur during accelerated life test,it is difficult to assess reliability for long-life products with traditional life tests.Reliability assessment using degradation data of product performance over time becomes a significant approach.Aerospace electrical connector is researched in this paper.Through the analysis of failure mechanism,the performance degradation law is obtained and the statistical model for degradation failure is set up;according to the research on statistical analysis methods for degradation data,accelerated life test theory and method for aerospace electrical connector based on performance degradation is proposed by improving time series analysis method,and the storage reliability is assessed for Y11X series of aerospace electrical connector with degradation data from accelerated degradation test.The result obtained is basically consistent with that obtained from accelerated life test based on failure data,and the two estimates of product's characteristic life only have a difference of 8.7%,but the test time shortens about a half.As a result,a systemic approach is proposed for reliability assessment of highly reliable and long-life aerospace product.
基金Supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2012AA09A205)
文摘The metal sealing performance of subsea X-tree wellhead connectors is crucial for the safety and reliability of subsea X-trees. In order to establish the theoretical relation between metal sealing ring's contact stress and its structural parameters and working pressure, a mechanical analysis method for double-cone sealing of high pressure vessels is applied in analyzing the metal sealing ring under the condition of preload and operation. As a result, the formula of the unit sealing load for the metal sealing ring under operation with residual preload is shown in this paper, which ensures that the metal sealing ring has an excellent sealing effect and can prevent the metal sealing ring from yielding. Besides, while analyzing the sealing process of the metal sealing ring, the change rule of contact stress and working pressure is concluded here, putting forward that the structural parameters of the metal sealing ring are the major factors affecting the change rule. Finally, the analytical solution through theoretical analysis is compared with the simulation result through finite element analysis in a force feedback experiment, and both are consistent with each other, which fully verifies for the design and calculation theory on metal sealing ring's contact stress and its structural parameters and working pressure deduced in this paper. The proposed research will be treated as an applicable theory guiding the design of metal seal for subsea X-tree wellhead connectors.
文摘Thermal analysis and thermal diagnose are important for small power connector especially in electronic devices since their structure is usually compact. In this paper thermal behavior of small power connector was investigated. It was found that the contact resistance increased due to the Joule heating, and that increased contact resistance produced more Joule heating; this mutual action causes the connector to lose efficiency. The thermal distribution in the connector was analyzed using finite element method (FEM). The failure mechanism is discussed. It provides basis for improving the structure. The conclusion was verified by experimental results.
文摘Pin and socket contacts are the key parts of electrical connector as aerospace electronic components. The contacts are also the direct carriers for signal transmitting of electronic equipments, passing the signal from the input end to the output end of electrical connector. The reliability of pin and socket contacts directly influences signal transmission. The goal of this study is to enhance the contact reliability of aerospace electrical connector. Computer simulation analysis was made on contacts performance data by utilizing the simulation system developed by PCL Language of MSC software. Furthermore, the results were experi- mentally validated so as to realize the objective of optimizing contacts design.
