Through the investigation on traditional arc stud welding process, a new welding gun and its control system were developed in this paper. The stepping arc stud welding gun was mainly made by a stepping motor as actuat...Through the investigation on traditional arc stud welding process, a new welding gun and its control system were developed in this paper. The stepping arc stud welding gun was mainly made by a stepping motor as actuating unit and a screw-driven device as moving unit. A control system with a MCS-51 single-chip microcomputer as main control component was used to realize the new stud welding procedure. This new welding process with stepping stud welding gun is named as stepping arc stud welding. In the new welding process, the stud action can be looked as constituted by some micro steps. The setting and adjusting of the stepping arc welding gun behavior parameters are accomplished independently. It is indicated from the results of process tests and bending test that the stepping arc stud welding process is practicable.展开更多
Cold metal transfer （CMT） welding of nickel-coated Q235 steel studs with 606l Al alloy was carried out using ER4043 as filler metal. The welding process was stable, and appearance of weld formed well without surface...Cold metal transfer （CMT） welding of nickel-coated Q235 steel studs with 606l Al alloy was carried out using ER4043 as filler metal. The welding process was stable, and appearance of weld formed well without surface defect under the parameters of welding current 121 A, welding voltage 15.4 V and welding speed 6 r/min. The microstructure of fiUer metal was analyzed by means of scanning electron microscopy. The filler metal and 6061 Al alloy were fused to form fusion welding interface, the fusion zone had a good bonding without any micro defect. The steel stud did not melt and brazing interface was formed between the filler metal and steel stud. Two different reaction layers existed in the brazing interface, the Fe2Al5 layer about 10 -12 p^m formed near the steel stud side, and the other layer was mainly composed of FeAl3. Nickel-rich zone was formed in the root toe area of the fillet weld, which was mainly composed of Al3Ni2. The tensile tests showed that the maximum shearing strength of the joints was 129 MPa. The joint was brittle fractured in the intermetallic compound layer where plenty of FeAl3 were distributed continuously.展开更多
Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure...Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.展开更多
This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element(FE) mo...This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element(FE) model and analyze the behavior of push-out specimens. The modeling results are in good agreement with the experimental results. Based on parametrical analysis using the validated FE approaches, the effects of important design parameters, such as the diameter, number, length to diameter ratio, and yield strength of studs, concrete strength and steel transverse reinforcement ratio, on the load-slip relationship at the interface of composite beams are discussed. In addition, a simplified approach to model studs is developed using virtual springs with an equivalent stiffness. This approach is demonstrated to be able to predict the load-displacement response and ultimate bearing capacity of steel-concrete composite beams. The predicted results show satisfactory agreement with experimental results from the literature.展开更多
Nickel-coated 45 steel studs and 6061 aluminum alloy with 4047 A1 alloy foil as filler metal were joined by using high frequency induction brazing. The microstrueture of Fe/A1 brazed joint was studied by means of opti...Nickel-coated 45 steel studs and 6061 aluminum alloy with 4047 A1 alloy foil as filler metal were joined by using high frequency induction brazing. The microstrueture of Fe/A1 brazed joint was studied by means of optical microscopy （OM）, scanning electron microscope （SEM）, energy dispersive X-ray （EDX）, and X-ray diffraction （XRD）. Results showed that 45 steel stud and 6061 aluminum alloy could be successfully joined by high frequency induction brazing with proper processing parameters. The bonding strength of the joint was of the order of 88 MPa. Ni coating on steel stud successfully avoided the generation of Fe-AI intermetallic compound which is brittle by blocking the contact between A1 and Fe. Intermetallic compounds, i e, AI3Ni2, AlmNi0.9 and A10.3Fe3Si0.7 presented in AI side, FeNi and Fe-A1-Ni ternary eutectic structure were formed in Fe side. The micro-hardness in intermetallic compound layer was 313 HV. The joint was brittle fractured in the intermetallic compounds layer of A1 side, where plenty of A13Ni2 intermetallie compounds were distributed continuously.展开更多
In order to achieve the computerization and digitization of the daily system of stud-farm, the immunization system technology, racecourse health monitoring technologies and the stud-farm prevention technologies were c...In order to achieve the computerization and digitization of the daily system of stud-farm, the immunization system technology, racecourse health monitoring technologies and the stud-farm prevention technologies were combined to built the studfarm daily management system. By using Visual Studio 2008 and Microsoft Office Access 2003, an immunization information system was developed based on Client/Server structure and combined with the key immunization link of horses. The system included studfarm immune management and racecourse health monitoring system. The immune management contained immunization information input, the inquiry of immunization information, immunization statistics, immunization-reminding and system management. The racecourse health monitoring system included stud-farm monitoring, horses monitoring and inquiry and statistics of health monitoring. The software realized the analysis and tips of the daily information in stud-farm. The software could record the appropriate data and carry on the statistics. The stud-farm daily management system greatly improved the efficiency of the expanded program about immunization and horses＇ healthy rearing technique.展开更多
The purpose of the present study is to investigate the influence of different types of shear connectors on mechanical behavior of composite steel and concrete girders under negative bending moment. Two overturned simp...The purpose of the present study is to investigate the influence of different types of shear connectors on mechanical behavior of composite steel and concrete girders under negative bending moment. Two overturned simply supported steel-concrete composite girders with different shear connectors including studs and PBLs （perfo-bond strips） were tested under point load in the mid-span. Based on the experimental observations, a three-dimensional FE （finite element） model capable of analyzing the composite girders subjected to negative bending moment was built. Load and deformation response, concrete initial cracking and composite girder ultimate load bearing capacity, strain development process of reinforcing bars before and after concrete cracking were observed in the test and compared with the numerical values. Results predicted by this modeling method are in good agreement with those obtained from the tests. Furthermore, the %rack closure＂ or ＂through crack＂ load were recorded by π-ganges in the tests and compared with the code-specified ultimate load.展开更多
There are hundreds of welded studs in a car.The posture of a welded stud determines the quality of the body assembly,thus affecting the safety of cars.It is crucial to detect the posture of the welded studs.Considerin...There are hundreds of welded studs in a car.The posture of a welded stud determines the quality of the body assembly,thus affecting the safety of cars.It is crucial to detect the posture of the welded studs.Considering the lack of accurate method in detecting the position of welded studs,this paper aims to detect the weld stud’s pose based on photometric stereo and neural network.Firstly,a machine vision-based stud dataset collection system is built to achieve the stud dataset labelling automatically.Secondly,photometric stereo algorithm is applied to estimate the stud normal map which as input is fed to neural network.Finally,we improve a lightweight YOLOv4 neural network which is applied to achieve the detection of stud position,thus overcoming the shortcomings of traditional testing methods.The research and experimental results show that the stud pose detection system designed achieves rapid detection and high accuracy positioning of the stud.This research provides the foundation combining the photometric stereo and deep learning for object detection in industrial production.展开更多
The applied conditions of stud welding on body of automobile, and the current waveforms and sequence control techniques which are set to meet the quality of stud welding in the car body, are introduced in this paper. ...The applied conditions of stud welding on body of automobile, and the current waveforms and sequence control techniques which are set to meet the quality of stud welding in the car body, are introduced in this paper. The realizing method of current waveforms and sequence control based on microprocessor are also discussed in detail. The waveforms of output welding current and voltage are measured. It is proved that the techniques including current waveforms & sequence control can successfully meet the demand of automobile stud welding.展开更多
The behavior of cold⁃formed steel(CFS)stud⁃to⁃sheathing connections at elevated temperatures is an important parameter for the fire resistance design and modeling of mid⁃rise CFS structures.In this paper,three kinds o...The behavior of cold⁃formed steel(CFS)stud⁃to⁃sheathing connections at elevated temperatures is an important parameter for the fire resistance design and modeling of mid⁃rise CFS structures.In this paper,three kinds of sheathings,namely,medium⁃and low⁃density calcium⁃silicate boards and oriented strand board,were selected for double⁃shear experiments on the mechanical properties of 253 screw connections at ambient and elevated temperatures.The effects of the shear direction,screw edge distance and the number of screws on the behavior of the connections were studied.The results showed that the shear direction and the screw edge distance more significantly influenced the peak deformation,while their impacts on the peak load varied with the type of sheathings.Compared with the single⁃screw connections,the peak loads of the specimens with double⁃screw connections obviously increased but did not double.Finally,a simplified load⁃displacement curve model of stud⁃to⁃sheathing connections at elevated temperature was generated first by establishing the prediction formula for characteristic parameters,such as the peak load,the peak deformation and the elastic stiffness,and then by considering whether the curves corresponded to stiffness increase phenomena.The present investigation provides basic data for future studies on the numerical modeling of CFS structures under fire conditions.展开更多
The Dragon Brand light steel stud used for partition is a kind of metallic framework that is continuously milled and rolled with cold formed steel shape using a cold-worked steel plate or strip, or zinc-coated plate o...The Dragon Brand light steel stud used for partition is a kind of metallic framework that is continuously milled and rolled with cold formed steel shape using a cold-worked steel plate or strip, or zinc-coated plate or strip, or coloured plastic packing steel plate, as materials. The steel stud has the features of light weight, high tension and anti-erosion. It can be used as light partition material together with plaster board, and its products or with other board materials such as GRC boards or展开更多
Vocabulary is the building material of language,and vocabulary study is therefore one of the most important aspects in any language learning.It is a key point to improve English learning through paying more attention ...Vocabulary is the building material of language,and vocabulary study is therefore one of the most important aspects in any language learning.It is a key point to improve English learning through paying more attention to vocabulary acquisition.However,vocabulary teaching is one aspect of language teaching that has not been given enough attention in China.Therefore,some issues in vocabulary teaching and learning in higher vocational colleges are being addressed at present,which are worthy of our further consideration.展开更多
The support plates including all of the inner hulls such as E grade steel, weld seams and SUS304L were considered to establish the optimal stud welding condition in LNG ship building. The stainless steel plate was esp...The support plates including all of the inner hulls such as E grade steel, weld seams and SUS304L were considered to establish the optimal stud welding condition in LNG ship building. The stainless steel plate was especially applied to the bracket on the liquid dome. The polished and etched surfaces of the welded stud and support plate were examined if the bead was properly formed. With the micrographic examination, the fusion boundary of metal weld zone formed by stud welding was analyzed to optimize the welding parameters. And also the analysis of the unacceptable welding faults such as cold and hot weld were performed. The mechanical tests such as tensile tests and bending tests were carried out to reveal any abnormal variation in the relationship of process parameters and the strength.展开更多
This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were teste...This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6d to 2d, there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.展开更多
For the sound insulation of a double-panel partition,the stud between two leaves creates a vibration transmission path,which can often be more critical and more important in the mid-frequency range than the airborne p...For the sound insulation of a double-panel partition,the stud between two leaves creates a vibration transmission path,which can often be more critical and more important in the mid-frequency range than the airborne path through the cavity.Owing to the fact that partitions with light-weight steel studs are commonly used in building construction,studies on the sound insulation effect of such studs have been conducted.Especially,a model,initiated by Gu and Wang(1983),has been widely studied during the past decades.In the model,the steel stud is considered as an elastic spring with its cross-section stiffness in the sound insulation index prediction of such a partition.Experimental results of different stud profiles have been reported from different testing laboratories and more information has been gained to understand the stiffness effect of the stud on the sound insulation of the double-leaf partitions.In this paper,the authors have given this subject a thorough review and have concluded that a critical problem needs further investigation on the determination of the stiffness of the connecting elements in the double-leaf partitions.展开更多
Statically push-out tests of 20 steel reinforced concrete short columns （SRCSC） with stud connectors on the surface of shape steel after fire and two SRCSC under ambient temperature were carried out, in order to stu...Statically push-out tests of 20 steel reinforced concrete short columns （SRCSC） with stud connectors on the surface of shape steel after fire and two SRCSC under ambient temperature were carried out, in order to study the failure mode, load-slip relationship and the interfacial shear transfer of SRC members after fire. Experimental results show that the typical failure modes and load-slip curves of SRCSC after fire are almost the same as the case under ambient temperature. The interfacial shear transfer of SRCSC declines exponentially not only with the increase of the peak temperature the specimen experienced but also with the increase of the peak temperature duration. The interfacial shear transfer of the specimens with studs arranged at the steel web is much higher than those with studs arranged at the steel flange. Empirical formulas of SRCSC interfacial shear transfer after fire are proposed, and the calculated results generally agree well with the experimental results.展开更多
文摘Through the investigation on traditional arc stud welding process, a new welding gun and its control system were developed in this paper. The stepping arc stud welding gun was mainly made by a stepping motor as actuating unit and a screw-driven device as moving unit. A control system with a MCS-51 single-chip microcomputer as main control component was used to realize the new stud welding procedure. This new welding process with stepping stud welding gun is named as stepping arc stud welding. In the new welding process, the stud action can be looked as constituted by some micro steps. The setting and adjusting of the stepping arc welding gun behavior parameters are accomplished independently. It is indicated from the results of process tests and bending test that the stepping arc stud welding process is practicable.
基金supported by the Natural Science Foundation of Jiangsu Province(No.BK20131261)
文摘Cold metal transfer （CMT） welding of nickel-coated Q235 steel studs with 606l Al alloy was carried out using ER4043 as filler metal. The welding process was stable, and appearance of weld formed well without surface defect under the parameters of welding current 121 A, welding voltage 15.4 V and welding speed 6 r/min. The microstructure of fiUer metal was analyzed by means of scanning electron microscopy. The filler metal and 6061 Al alloy were fused to form fusion welding interface, the fusion zone had a good bonding without any micro defect. The steel stud did not melt and brazing interface was formed between the filler metal and steel stud. Two different reaction layers existed in the brazing interface, the Fe2Al5 layer about 10 -12 p^m formed near the steel stud side, and the other layer was mainly composed of FeAl3. Nickel-rich zone was formed in the root toe area of the fillet weld, which was mainly composed of Al3Ni2. The tensile tests showed that the maximum shearing strength of the joints was 129 MPa. The joint was brittle fractured in the intermetallic compound layer where plenty of FeAl3 were distributed continuously.
基金Project(2004G016-B) supported by the Science and Technology Development Program of Railways Department,China
文摘Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.
基金Project(2011BAJ09B02)supported by the National Key Technology R&D Program,ChinaProjects(51578548,51378511,51678576)supported by the National Natural Science Foundation of China
文摘This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element(FE) model and analyze the behavior of push-out specimens. The modeling results are in good agreement with the experimental results. Based on parametrical analysis using the validated FE approaches, the effects of important design parameters, such as the diameter, number, length to diameter ratio, and yield strength of studs, concrete strength and steel transverse reinforcement ratio, on the load-slip relationship at the interface of composite beams are discussed. In addition, a simplified approach to model studs is developed using virtual springs with an equivalent stiffness. This approach is demonstrated to be able to predict the load-displacement response and ultimate bearing capacity of steel-concrete composite beams. The predicted results show satisfactory agreement with experimental results from the literature.
基金Funded by the National Defense Basic Research Program(No.A2620110005)the Equipment Pre Research Project of Eleventh Five-Year Plan of China(No.40401050301)the Natural Science Foundation of Jiangsu Province(No.BK20131261)
文摘Nickel-coated 45 steel studs and 6061 aluminum alloy with 4047 A1 alloy foil as filler metal were joined by using high frequency induction brazing. The microstrueture of Fe/A1 brazed joint was studied by means of optical microscopy （OM）, scanning electron microscope （SEM）, energy dispersive X-ray （EDX）, and X-ray diffraction （XRD）. Results showed that 45 steel stud and 6061 aluminum alloy could be successfully joined by high frequency induction brazing with proper processing parameters. The bonding strength of the joint was of the order of 88 MPa. Ni coating on steel stud successfully avoided the generation of Fe-AI intermetallic compound which is brittle by blocking the contact between A1 and Fe. Intermetallic compounds, i e, AI3Ni2, AlmNi0.9 and A10.3Fe3Si0.7 presented in AI side, FeNi and Fe-A1-Ni ternary eutectic structure were formed in Fe side. The micro-hardness in intermetallic compound layer was 313 HV. The joint was brittle fractured in the intermetallic compounds layer of A1 side, where plenty of A13Ni2 intermetallie compounds were distributed continuously.
基金Supported by 12th Five-year Science and Technology Plan in Rural Areas(2012BAD46B00)
文摘In order to achieve the computerization and digitization of the daily system of stud-farm, the immunization system technology, racecourse health monitoring technologies and the stud-farm prevention technologies were combined to built the studfarm daily management system. By using Visual Studio 2008 and Microsoft Office Access 2003, an immunization information system was developed based on Client/Server structure and combined with the key immunization link of horses. The system included studfarm immune management and racecourse health monitoring system. The immune management contained immunization information input, the inquiry of immunization information, immunization statistics, immunization-reminding and system management. The racecourse health monitoring system included stud-farm monitoring, horses monitoring and inquiry and statistics of health monitoring. The software realized the analysis and tips of the daily information in stud-farm. The software could record the appropriate data and carry on the statistics. The stud-farm daily management system greatly improved the efficiency of the expanded program about immunization and horses＇ healthy rearing technique.
文摘The purpose of the present study is to investigate the influence of different types of shear connectors on mechanical behavior of composite steel and concrete girders under negative bending moment. Two overturned simply supported steel-concrete composite girders with different shear connectors including studs and PBLs （perfo-bond strips） were tested under point load in the mid-span. Based on the experimental observations, a three-dimensional FE （finite element） model capable of analyzing the composite girders subjected to negative bending moment was built. Load and deformation response, concrete initial cracking and composite girder ultimate load bearing capacity, strain development process of reinforcing bars before and after concrete cracking were observed in the test and compared with the numerical values. Results predicted by this modeling method are in good agreement with those obtained from the tests. Furthermore, the %rack closure＂ or ＂through crack＂ load were recorded by π-ganges in the tests and compared with the code-specified ultimate load.
基金The work is partly supported by the Natural Science Basic Research Plan in Shaanxi Province of China(No.2016JM6041).
文摘There are hundreds of welded studs in a car.The posture of a welded stud determines the quality of the body assembly,thus affecting the safety of cars.It is crucial to detect the posture of the welded studs.Considering the lack of accurate method in detecting the position of welded studs,this paper aims to detect the weld stud’s pose based on photometric stereo and neural network.Firstly,a machine vision-based stud dataset collection system is built to achieve the stud dataset labelling automatically.Secondly,photometric stereo algorithm is applied to estimate the stud normal map which as input is fed to neural network.Finally,we improve a lightweight YOLOv4 neural network which is applied to achieve the detection of stud position,thus overcoming the shortcomings of traditional testing methods.The research and experimental results show that the stud pose detection system designed achieves rapid detection and high accuracy positioning of the stud.This research provides the foundation combining the photometric stereo and deep learning for object detection in industrial production.
文摘The applied conditions of stud welding on body of automobile, and the current waveforms and sequence control techniques which are set to meet the quality of stud welding in the car body, are introduced in this paper. The realizing method of current waveforms and sequence control based on microprocessor are also discussed in detail. The waveforms of output welding current and voltage are measured. It is proved that the techniques including current waveforms & sequence control can successfully meet the demand of automobile stud welding.
基金the National Natural Science Foundation of China(Grant No.51978655)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20201347)+1 种基金the Xuzhou Science and Technology Project(Grant No.KC20175)the China Postdoctoral Science Foundation Funded Project(Grant No.2019M652007).
文摘The behavior of cold⁃formed steel(CFS)stud⁃to⁃sheathing connections at elevated temperatures is an important parameter for the fire resistance design and modeling of mid⁃rise CFS structures.In this paper,three kinds of sheathings,namely,medium⁃and low⁃density calcium⁃silicate boards and oriented strand board,were selected for double⁃shear experiments on the mechanical properties of 253 screw connections at ambient and elevated temperatures.The effects of the shear direction,screw edge distance and the number of screws on the behavior of the connections were studied.The results showed that the shear direction and the screw edge distance more significantly influenced the peak deformation,while their impacts on the peak load varied with the type of sheathings.Compared with the single⁃screw connections,the peak loads of the specimens with double⁃screw connections obviously increased but did not double.Finally,a simplified load⁃displacement curve model of stud⁃to⁃sheathing connections at elevated temperature was generated first by establishing the prediction formula for characteristic parameters,such as the peak load,the peak deformation and the elastic stiffness,and then by considering whether the curves corresponded to stiffness increase phenomena.The present investigation provides basic data for future studies on the numerical modeling of CFS structures under fire conditions.
文摘The Dragon Brand light steel stud used for partition is a kind of metallic framework that is continuously milled and rolled with cold formed steel shape using a cold-worked steel plate or strip, or zinc-coated plate or strip, or coloured plastic packing steel plate, as materials. The steel stud has the features of light weight, high tension and anti-erosion. It can be used as light partition material together with plaster board, and its products or with other board materials such as GRC boards or
文摘Vocabulary is the building material of language,and vocabulary study is therefore one of the most important aspects in any language learning.It is a key point to improve English learning through paying more attention to vocabulary acquisition.However,vocabulary teaching is one aspect of language teaching that has not been given enough attention in China.Therefore,some issues in vocabulary teaching and learning in higher vocational colleges are being addressed at present,which are worthy of our further consideration.
文摘The support plates including all of the inner hulls such as E grade steel, weld seams and SUS304L were considered to establish the optimal stud welding condition in LNG ship building. The stainless steel plate was especially applied to the bracket on the liquid dome. The polished and etched surfaces of the welded stud and support plate were examined if the bead was properly formed. With the micrographic examination, the fusion boundary of metal weld zone formed by stud welding was analyzed to optimize the welding parameters. And also the analysis of the unacceptable welding faults such as cold and hot weld were performed. The mechanical tests such as tensile tests and bending tests were carried out to reveal any abnormal variation in the relationship of process parameters and the strength.
文摘This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6d to 2d, there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.
文摘For the sound insulation of a double-panel partition,the stud between two leaves creates a vibration transmission path,which can often be more critical and more important in the mid-frequency range than the airborne path through the cavity.Owing to the fact that partitions with light-weight steel studs are commonly used in building construction,studies on the sound insulation effect of such studs have been conducted.Especially,a model,initiated by Gu and Wang(1983),has been widely studied during the past decades.In the model,the steel stud is considered as an elastic spring with its cross-section stiffness in the sound insulation index prediction of such a partition.Experimental results of different stud profiles have been reported from different testing laboratories and more information has been gained to understand the stiffness effect of the stud on the sound insulation of the double-leaf partitions.In this paper,the authors have given this subject a thorough review and have concluded that a critical problem needs further investigation on the determination of the stiffness of the connecting elements in the double-leaf partitions.
基金Acknowledgements This research is supported by the National Science Foundation of China （Grant Nos. 50908118 and No. 51308307）, Ningbo Science Foundation （No. 2013A610194） and Ningbo Key Scientific Projects （No. XKL11D2079）.
文摘Statically push-out tests of 20 steel reinforced concrete short columns （SRCSC） with stud connectors on the surface of shape steel after fire and two SRCSC under ambient temperature were carried out, in order to study the failure mode, load-slip relationship and the interfacial shear transfer of SRC members after fire. Experimental results show that the typical failure modes and load-slip curves of SRCSC after fire are almost the same as the case under ambient temperature. The interfacial shear transfer of SRCSC declines exponentially not only with the increase of the peak temperature the specimen experienced but also with the increase of the peak temperature duration. The interfacial shear transfer of the specimens with studs arranged at the steel web is much higher than those with studs arranged at the steel flange. Empirical formulas of SRCSC interfacial shear transfer after fire are proposed, and the calculated results generally agree well with the experimental results.
