Carbon-based low-dimensional materials(CLDM)with elemental carbon as the main component have unique physical and chemical properties,and become the focus of research in many fields including energy,environmental prote...Carbon-based low-dimensional materials(CLDM)with elemental carbon as the main component have unique physical and chemical properties,and become the focus of research in many fields including energy,environmental protection,and information technology.Notably,cellulose acetate,the main component of cigarette butts(CBs),is a one-dimensional precursor with a large specific surface area and aspect ratio.Still,their usefulness as building fillers has often been underestimated before.This review summarizes recent advances in CBs recycling and provides suggested guidelines for its use as a CLDM material in renewable energy.Specifically,we first describe the harmful effects of CBs as pollutants in our lives to emphasize the importance of proper recycling.We then summarize previous methods of recycling CBs waste,including clay bricks,asphalt concrete pavement,gypsum,acoustic materials,chemisorption,vector control,and corrosion control.The potential applications of CBs include triboelectric nanogenerator applications,flexible batteries,enhanced metal-organic framework material energy storage devices,and carbon-based hydrogen storage.Finally,the advantages of utilizing CBs-derived CLDM materials over conventional solutions in the energy field are discussed.This review will provide new avenues for solving the intractable problem of CBs and reducing the manufacturing costs of renewable materials.展开更多
Carbon Fiber Reinforced Thermosetting Composites(CFRTS)are crucial materials for lightweight manufacturing in the aerospace industry.To achieve high-quality butt joining between CFRTS,the Metal-Assistant-Clamping(MAC)...Carbon Fiber Reinforced Thermosetting Composites(CFRTS)are crucial materials for lightweight manufacturing in the aerospace industry.To achieve high-quality butt joining between CFRTS,the Metal-Assistant-Clamping(MAC)laser rotational welding method is proposed.In this method,two TC4 titanium alloy plates were clamped at the docking position of the CFRTS butt joint,and the TC4 titanium alloy plates were joined with the CFRTS using laser rotational welding technology.Laser cleaning and micro-textures as interface pretreatment were applied to enhance the joining strength.The impact of laser cleaning on the strength of the CFRTS butt joint was examined,revealing that epoxy resin on the CFRTS surface was effectively removed,leading to an increase in bonding strength between the CFRTS and TC4 titanium alloy.The microtextures,mechanical properties,and failure mechanism of CFRTS butt joints were investigated.The results indicate that the interface pretreatment created mechanical interlocks and chemical bonds between the CFRTS and TC4 alloy,further strengthening the CFRTS butt joint.The failure of the CFRTS butt joint was observed to occur between the Polyamide-6(PA6)resin and the surface carbon fibers of the CFRTS,predominantly through CFRTS interlayer tearing.展开更多
The dissimilar friction stir welding of pure copper/1350 aluminum alloy sheet with a thickness of 3 mm was investigated. Most of the rotating pin was inserted into the aluminum alloy side through a pin-off technique, ...The dissimilar friction stir welding of pure copper/1350 aluminum alloy sheet with a thickness of 3 mm was investigated. Most of the rotating pin was inserted into the aluminum alloy side through a pin-off technique, and sound welds were obtained at a rotation speed of 1000 r/min and a welding speed of 80 mm/min. Complicated microstructure was formed in the nugget, in which vortex-like pattern and lamella structure could be found. No intermetallic compounds were found in the nugget. The hardness distribution indicates that the hardness at the copper side of the nugget is higher than that at the aluminum alloy side, and the hardness at the bottom of the nugget is generally higher than that in other regions. The ultimate tensile strength and elongation of the dissimilar welds are 152 MPa and 6.3%, respectively. The fracture surface observation shows that the dissimilar joints fail with a ductile-brittle mixed fracture mode durin~ tensile test.展开更多
Laser-metal inert-gas(MIG)hybrid welding-brazing was applied to the butt joint of 6061-T6 aluminum alloy and 304 stainless steel.The microstructure and mechanical properties of the joint were studied.An excellent join...Laser-metal inert-gas(MIG)hybrid welding-brazing was applied to the butt joint of 6061-T6 aluminum alloy and 304 stainless steel.The microstructure and mechanical properties of the joint were studied.An excellent joint-section shape was achieved from good wettability on both sides of the stainless steel.Scanning electron microscopy,energy-dispersive spectroscopy and X-ray diffractometry indicated an intermetallic compound(IMC)layer at the 6061-T6/304 interface.The IMC thickness was controlled to be^2μm,which was attributed to the advantage of the laser-MIG hybrid method.Fe3Al dominated in the IMC layer at the interface between the stainless steel and the back reinforcement.The IMC layer in the remaining regions consisted mainly of Fe4Al13.A thinner IMC layer and better wettability on both sides of the stainless steel were obtained,because of the optimized energy distribution from a combination of a laser beam with a MIG arc.The average tensile strength of the joint with reinforcement using laser-MIG hybrid process was improved to be 174 MPa(60%of the 6061-T6 tensile strength),which was significantly higher than that of the joint by traditional MIG process.展开更多
Stress concentration has a significant effect on fatigue properties of welded butt joint of bogie.The influences of joint geometric parameters {weld edge transition arc radius r,weld toe inclination angle θ） on stre...Stress concentration has a significant effect on fatigue properties of welded butt joint of bogie.The influences of joint geometric parameters {weld edge transition arc radius r,weld toe inclination angle θ） on stress concentration coefficient Kt at weld toe and fatigue life N were studied based on the finite element software ABAQUS/FE-SAFE,and the parametric equations were founded based on regression analysis of Origin software.The results show that weld edge transition arc radius r plays the most important role in stress concentration coefficient Kt as well as weld toe inclination angle 0.For the same inclination angle θ,stress concentration coefficient Kt decreases gradually with transition arc radius r increasing.With inclination angle θ increases,the effect of transition arc radius r on stress concentration factor Kt is increasing continuously,also the effect of change in stress concentration coefficient Kt caused by r on fatigue life N is increasing continuously.While in the case of same weld edge transition arc radius r,stress concentration coefficient Kt increases with inclination angle θincreasing.With transition arc radius r increases,the effect of inclination angle θ on stress concentration factor Kt is decreasing constantly,the effect of change in stress concentration coefficient Kt caused by θ on fatigue life N is decreasing constantly.The associated parametric equations have important instructive significance for the improvement of stress concentration degree and fatigue life of welded butt joint for train bogie.展开更多
The microstructure and mechanical properties of pulse metal inert-gas （MIG） welded dissimilar joints between 4 mm thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates were investigated. The tensile strength ...The microstructure and mechanical properties of pulse metal inert-gas （MIG） welded dissimilar joints between 4 mm thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates were investigated. The tensile strength of the joints reached 235 MPa, which is 83% of that of 6061 aluminum alloy, and then decreased with the increase of travel speed while keeping other welding parameters constant. The microstructure, composition and fractography of joints were examined by the optical microscopy （OM）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA）. Grain boundary liquation and segregation occurred in the partially melted zone （PMZ） on 6061 aluminum alloy side, and brittle Fe-rich phases were observed in partially melted zone on A356 aluminum alloy side. The minimum microhardness appeared in heat-affected zone （HAZ） near A356 aluminum alloy substrate. The samples during tensile test failed mainly in PMZ and HAZ on A356 aluminum alloy side through mixed fracture mode with quasi cleavage and dimples on fracture surface.展开更多
An axial symmetry finite element model coupled with electricity-thermal effect was developed to study the temperature field distribution in process of the flash butt welding （FBW） of frog highmanganese steel. The in...An axial symmetry finite element model coupled with electricity-thermal effect was developed to study the temperature field distribution in process of the flash butt welding （FBW） of frog highmanganese steel. The influence of temperature dependent material properties and the contact resistance were taken into account in FEM ＇simulation. Meanwhile, the lost materials due to .splutter was resolved by using birth and death element. The result of analyzing data shows that the moddel in the FBW flashing is reasonable and feasible, and can exactly simulate the temperature field distribution. The modeling provides reference for analysis of welding technologies on the temperature field of high-manganese steel in FBW.展开更多
Under the spirit of sustainable development, ‘lightweight’ has been gradually included into the vehicle design criterion by many manufacturers and used in automobile production. Following this trend, domestic wheel ...Under the spirit of sustainable development, ‘lightweight’ has been gradually included into the vehicle design criterion by many manufacturers and used in automobile production. Following this trend, domestic wheel suppliers also begin to study the technology of lightweight wheel. One way to achieve this goal is improving strength grade of the steel and optimizing the structure design in the field of steel wheels. But there are a few problems in flash butt welding process in the application of high strength steel, leading to high rejection rates. SW400 steel is a special high strength wheel steel developed by Benxi Steel. Taking SW400 steel as the research material, this article studys the feasibility of improving the properties of rim flash butt welded joints by adding preheating process.展开更多
The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimen...The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimental results displayed that the tensile strength of the joint made with angular butt joint and 0.3 ram-wide gap reached 266 MPa, the joint fractured through the heat-affected zone or base metal during tensile testing, and the microstructure examination showed that no macropore appeared in the fusion zone. However, macropores in diameter of larger than 200 micron occurred for other joint designs, the tensile strength of the resultant joints decreased, and the joints fractured through the fusion zone during tensile testing. The fracture surfaces were examined by scanning electron microscopy and the microhardness distribution in the joints was measured by using a Vickers microhardness tester.展开更多
The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded c...The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded cast steel joint was analyzed to determine the optimal mesh size.Based on the stress field analysis of the finite element model of the welded cast steel joint at the weld toe and weld root,the sharp model of the extrapolation notch stress method was applied to derive the effective notch stress of the rounded model belonging to the effective notch stress method,in which the key problem is to calculate the extrapolation point C,and the extrapolation point C has an exponential function relationship with the geometric parameters of the welded cast steel joint.By setting different values of geometric parameters,the corresponding value of parameter C is calculated,and then the functional relationship between the extrapolation point C and the geometric parameters can be obtained by the multiple linear regression analysis.Meanwhile,the fatigue life evaluation of the girth butt weld within welded cast steel joints based on the effective notch stress was performed according to the guideline recommended by the IIW(International Institute of Welding).The results indicate that the extrapolation notch stress method can effectively simplify the process of calculating the effective notch stress and accurately evaluate the fatigue life of the girth butt weld within welded cast steel joints.展开更多
In order to investigate the laws of variation on tensile strength of butt welded joint post high temperatures, the wide plate tension tests for butt welded joint were conducted after cooling down from different high t...In order to investigate the laws of variation on tensile strength of butt welded joint post high temperatures, the wide plate tension tests for butt welded joint were conducted after cooling down from different high temperatures. The tests indicate that specimens appear ductile fracture at the steel plate during the tension tests after cooling down. The maximum temperatures undergone and the cooling pattern are major factors influencing tensile strength of butt welded joint post high temperatures. The tensile strength mostly reduces by 8% within 900℃. Based on the experimental results, the paper proposes the calculation formulas of tensile strength of butt welded joint post high temperatures. The conclusions of the paper supply references for evaluation damage and reinforcement of steel structure post fire.展开更多
The fatigue properties of friction stir welded （FSW） butt joint and base metal of MB8 magnesium alloy were investigated. The comparative fatigue tests were carried out using EHF-EM2OOK2-070-IA fatigue testing machin...The fatigue properties of friction stir welded （FSW） butt joint and base metal of MB8 magnesium alloy were investigated. The comparative fatigue tests were carried out using EHF-EM2OOK2-070-IA fatigue testing machine for both FSW butt joint and base metal specimens. The fatigue fractures were observed and analyzed using a scanning electron microscope of JSM-6063LA type. The experimental results show that the fatigue performance of the FSW butt joint of MB8 magnesium alloy is sharply decreased. The conditional fatigue limit （2 x 106） of base metal and welded butt joint is about 77.44 MPa and 49. 91 MPa, respectively. The conditional fatigue limit （2 x 106 ） of the welded butt joint is 64.45% of that of base metal. The main reasons are that the welding can lead to stress concentration in the flash area, tensile welding residual stress in the welded joint（ The residual stress value was 30. 5 MPa）, as well as the grain size is not uniform in the heat-affected zone. The cleavage steps or quasi-cleavage patterns present on the fatigue fracture surface, the fracture type of the FSW butt joint belongs to a brittle fracture.展开更多
In order to improve the bending load-carrying capacity （BLCC） of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors （SCF） at the wel...In order to improve the bending load-carrying capacity （BLCC） of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors （SCF） at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.展开更多
The construction of grouting butt joints of bamboo tubes is simple and efficient.However,when the joint is bent,the low tensile strength of the mortar easily leads to cracking of the mortar prior to the failure of the...The construction of grouting butt joints of bamboo tubes is simple and efficient.However,when the joint is bent,the low tensile strength of the mortar easily leads to cracking of the mortar prior to the failure of the bamboo tube.In this paper,a comparative test of the bending capacity was performed on grouting butt joints reinforced by nonperforated,fully perforated,and semiperforated steel plates embedded in bamboo tubes to obtain the loaddisplacement curves and ultimate bearing capacity of various specimens.The strengthening effect of CFRP pasted on bamboo tubes was also studied.The results show that the opening at the end of the steel plate is beneficial to resist the slip between the mortar and steel plate,while the complete section in the middle of the steel plate is conducive to making full use of the tensile strength of the steel plate.Therefore,it is best to insert the semiperforated steel plate with openings in the end and without openings in the middle into the mortar to enhance the bending properties of the grouting butt joint,which can make the failure mode of the joint change from brittle failure of mortar to ductile compression failure of bamboo tube.In addition,pasting CFRP sheets on the external wall of the bamboo tube helps to reduce the tensile stress of the mortar,while increasing the width of the steel plate can increase the bending moment of inertia of the mixture of the steel plate and mortar.These two complementary measures are very effective in delaying the cracking of the bamboo tube and improving the bending capacity of the joint.展开更多
The disposal of discarded E-cigarette butts(E-CBs) presents significant environmental challenges due to their detrimental impacts on ecosystems. To find an environmentally sustainable method for managing this waste, t...The disposal of discarded E-cigarette butts(E-CBs) presents significant environmental challenges due to their detrimental impacts on ecosystems. To find an environmentally sustainable method for managing this waste, the potential for recycling E-CBs in asphalt pavements was investigated in this study. By focusing on the two primary components of E-CBs, namely cellulose fibre and polylactic acid(PLA), this research introduced a novel approach for recycling E-CBs in stone mastic asphalt(SMA) as a fibre additive in engineered pellet form. The prepared fibre pellets were directly added to aggregates to produce the SMA mixture. The resulting mixtures underwent a comprehensive evaluation through a series of standardized laboratory tests, including assessments of volumetric properties, indirect tensile strength(ITS), stiffness modulus, moisture susceptibility, and rutting resistance. The results were compared with SMA mixtures containing conventional cellulose fibres. Additionally, to examine the potential influence of PLA, a third mixture was prepared, incorporating both cellulose fibre and PLA. The findings indicate that the SMA using pelletized fibre can satisfy the technical specifications regarding the tests performed in this study, showing higher ITS and rutting resistance compared to the reference mixture. Moreover, the incorporation of PLA plastic reduced air void content and improved tensile strength, stiffness, and rutting resistance. This study highlights the potential for recycling E-CBs in asphalt mixtures, offering technical support for further development of sustainable recycling methods for this waste.展开更多
China ranks first in the world as the number of smokers. The environmental pollution and recycling problems of waste cigarette butts are becoming more and more serious. How to make better reuse of waste cigarette butt...China ranks first in the world as the number of smokers. The environmental pollution and recycling problems of waste cigarette butts are becoming more and more serious. How to make better reuse of waste cigarette butts has been taken action by some countries and regions in the world. In order to study the utilization value of the cigarette butt in road performance, this test takes No. 70 matrix bitumen and waste tobacco as raw material. The optimum amount of the content of the cigarette butt in the experiment is further determined based on the test performance of the modified asphalt mixture and the modified bitumen mixture is prepared by the addition method. The performance indexes of modified bituminous mixture with different dosages were tested and studied. Combined with production and economic realities, the optimum cigarette butt content of modified asphalt mixture is determined to make the road performance optimal. This paper focuses on the determination of the best bituminous content of the bituminous mixture. Through the toxicity test of the leachate published abroad to reflect the pollution of the cigarette butt to the environment and analyze the harm to the environment, combined with the development of global reusing technology and the economic benefits brought by cigarette butts, the prospect of the utilization of waste cigarette butts is forecasted.展开更多
The hardware and software design of two digital control systems based on 80C196KB MCU for flash butt welder is introduced in this paper.The welding power supply is made of six-phase half-wave rectifier.The welding out...The hardware and software design of two digital control systems based on 80C196KB MCU for flash butt welder is introduced in this paper.The welding power supply is made of six-phase half-wave rectifier.The welding outer characteristic of welding machine is realized by digital PI algorithm with the voltage close-loop feedback.The flashing curve is finished by elec- tric-hydraulic servo valve.The process control system transfers datum with power supply system by a serial communication inter- face.The parameters of the control systems are collected by photoelectrical seclusion to avoid the disturbing of the electromagnetism in welding process.展开更多
Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a dis...Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.展开更多
基金supported by Hubei Province Technology Innovation Program Project(2024BCB073)the National Natural Science Foundation of China(52402249)the China Postdoctoral Science Foundation(2021M690930).
文摘Carbon-based low-dimensional materials(CLDM)with elemental carbon as the main component have unique physical and chemical properties,and become the focus of research in many fields including energy,environmental protection,and information technology.Notably,cellulose acetate,the main component of cigarette butts(CBs),is a one-dimensional precursor with a large specific surface area and aspect ratio.Still,their usefulness as building fillers has often been underestimated before.This review summarizes recent advances in CBs recycling and provides suggested guidelines for its use as a CLDM material in renewable energy.Specifically,we first describe the harmful effects of CBs as pollutants in our lives to emphasize the importance of proper recycling.We then summarize previous methods of recycling CBs waste,including clay bricks,asphalt concrete pavement,gypsum,acoustic materials,chemisorption,vector control,and corrosion control.The potential applications of CBs include triboelectric nanogenerator applications,flexible batteries,enhanced metal-organic framework material energy storage devices,and carbon-based hydrogen storage.Finally,the advantages of utilizing CBs-derived CLDM materials over conventional solutions in the energy field are discussed.This review will provide new avenues for solving the intractable problem of CBs and reducing the manufacturing costs of renewable materials.
基金the financial support by the Ningbo"Science and Technology Innovation Yongjiang 2035"Key Research and Development Program,China(Nos.2025Z188,2025Z016)"The 14th Five Year Plan"Major Technical Research and Development Project of Zhenhai District,China(No.2023001)the CAS Youth Interdisciplinary Team,China(No.2023-135)。
文摘Carbon Fiber Reinforced Thermosetting Composites(CFRTS)are crucial materials for lightweight manufacturing in the aerospace industry.To achieve high-quality butt joining between CFRTS,the Metal-Assistant-Clamping(MAC)laser rotational welding method is proposed.In this method,two TC4 titanium alloy plates were clamped at the docking position of the CFRTS butt joint,and the TC4 titanium alloy plates were joined with the CFRTS using laser rotational welding technology.Laser cleaning and micro-textures as interface pretreatment were applied to enhance the joining strength.The impact of laser cleaning on the strength of the CFRTS butt joint was examined,revealing that epoxy resin on the CFRTS surface was effectively removed,leading to an increase in bonding strength between the CFRTS and TC4 titanium alloy.The microtextures,mechanical properties,and failure mechanism of CFRTS butt joints were investigated.The results indicate that the interface pretreatment created mechanical interlocks and chemical bonds between the CFRTS and TC4 alloy,further strengthening the CFRTS butt joint.The failure of the CFRTS butt joint was observed to occur between the Polyamide-6(PA6)resin and the surface carbon fibers of the CFRTS,predominantly through CFRTS interlayer tearing.
基金Project (2009ZM0264) supported by the Fundamental Research Funds for the Central Universities,China
文摘The dissimilar friction stir welding of pure copper/1350 aluminum alloy sheet with a thickness of 3 mm was investigated. Most of the rotating pin was inserted into the aluminum alloy side through a pin-off technique, and sound welds were obtained at a rotation speed of 1000 r/min and a welding speed of 80 mm/min. Complicated microstructure was formed in the nugget, in which vortex-like pattern and lamella structure could be found. No intermetallic compounds were found in the nugget. The hardness distribution indicates that the hardness at the copper side of the nugget is higher than that at the aluminum alloy side, and the hardness at the bottom of the nugget is generally higher than that in other regions. The ultimate tensile strength and elongation of the dissimilar welds are 152 MPa and 6.3%, respectively. The fracture surface observation shows that the dissimilar joints fail with a ductile-brittle mixed fracture mode durin~ tensile test.
基金Project(51405398) supported by the National Natural Science Foundation of China
文摘Laser-metal inert-gas(MIG)hybrid welding-brazing was applied to the butt joint of 6061-T6 aluminum alloy and 304 stainless steel.The microstructure and mechanical properties of the joint were studied.An excellent joint-section shape was achieved from good wettability on both sides of the stainless steel.Scanning electron microscopy,energy-dispersive spectroscopy and X-ray diffractometry indicated an intermetallic compound(IMC)layer at the 6061-T6/304 interface.The IMC thickness was controlled to be^2μm,which was attributed to the advantage of the laser-MIG hybrid method.Fe3Al dominated in the IMC layer at the interface between the stainless steel and the back reinforcement.The IMC layer in the remaining regions consisted mainly of Fe4Al13.A thinner IMC layer and better wettability on both sides of the stainless steel were obtained,because of the optimized energy distribution from a combination of a laser beam with a MIG arc.The average tensile strength of the joint with reinforcement using laser-MIG hybrid process was improved to be 174 MPa(60%of the 6061-T6 tensile strength),which was significantly higher than that of the joint by traditional MIG process.
基金supported by the National Natural Science Foundation of China(No.51365014)Natural Science Foundation of Jiangxi Province(No.20151BAB206007)
文摘Stress concentration has a significant effect on fatigue properties of welded butt joint of bogie.The influences of joint geometric parameters {weld edge transition arc radius r,weld toe inclination angle θ） on stress concentration coefficient Kt at weld toe and fatigue life N were studied based on the finite element software ABAQUS/FE-SAFE,and the parametric equations were founded based on regression analysis of Origin software.The results show that weld edge transition arc radius r plays the most important role in stress concentration coefficient Kt as well as weld toe inclination angle 0.For the same inclination angle θ,stress concentration coefficient Kt decreases gradually with transition arc radius r increasing.With inclination angle θ increases,the effect of transition arc radius r on stress concentration factor Kt is increasing continuously,also the effect of change in stress concentration coefficient Kt caused by r on fatigue life N is increasing continuously.While in the case of same weld edge transition arc radius r,stress concentration coefficient Kt increases with inclination angle θincreasing.With transition arc radius r increases,the effect of inclination angle θ on stress concentration factor Kt is decreasing constantly,the effect of change in stress concentration coefficient Kt caused by θ on fatigue life N is decreasing constantly.The associated parametric equations have important instructive significance for the improvement of stress concentration degree and fatigue life of welded butt joint for train bogie.
基金financially supported by the National Natural Science Foundation of China(No.51374048)the Fundamental Research Funds for the Central Universities(No.DUT16RC(3)009)
文摘The microstructure and mechanical properties of pulse metal inert-gas （MIG） welded dissimilar joints between 4 mm thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates were investigated. The tensile strength of the joints reached 235 MPa, which is 83% of that of 6061 aluminum alloy, and then decreased with the increase of travel speed while keeping other welding parameters constant. The microstructure, composition and fractography of joints were examined by the optical microscopy （OM）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA）. Grain boundary liquation and segregation occurred in the partially melted zone （PMZ） on 6061 aluminum alloy side, and brittle Fe-rich phases were observed in partially melted zone on A356 aluminum alloy side. The minimum microhardness appeared in heat-affected zone （HAZ） near A356 aluminum alloy substrate. The samples during tensile test failed mainly in PMZ and HAZ on A356 aluminum alloy side through mixed fracture mode with quasi cleavage and dimples on fracture surface.
文摘An axial symmetry finite element model coupled with electricity-thermal effect was developed to study the temperature field distribution in process of the flash butt welding （FBW） of frog highmanganese steel. The influence of temperature dependent material properties and the contact resistance were taken into account in FEM ＇simulation. Meanwhile, the lost materials due to .splutter was resolved by using birth and death element. The result of analyzing data shows that the moddel in the FBW flashing is reasonable and feasible, and can exactly simulate the temperature field distribution. The modeling provides reference for analysis of welding technologies on the temperature field of high-manganese steel in FBW.
基金supported by the Key Science and Technology of Jilin Province(Grant No.20140204070GX)
文摘Under the spirit of sustainable development, ‘lightweight’ has been gradually included into the vehicle design criterion by many manufacturers and used in automobile production. Following this trend, domestic wheel suppliers also begin to study the technology of lightweight wheel. One way to achieve this goal is improving strength grade of the steel and optimizing the structure design in the field of steel wheels. But there are a few problems in flash butt welding process in the application of high strength steel, leading to high rejection rates. SW400 steel is a special high strength wheel steel developed by Benxi Steel. Taking SW400 steel as the research material, this article studys the feasibility of improving the properties of rim flash butt welded joints by adding preheating process.
基金supported by the State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology (Project No.09009)
文摘The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimental results displayed that the tensile strength of the joint made with angular butt joint and 0.3 ram-wide gap reached 266 MPa, the joint fractured through the heat-affected zone or base metal during tensile testing, and the microstructure examination showed that no macropore appeared in the fusion zone. However, macropores in diameter of larger than 200 micron occurred for other joint designs, the tensile strength of the resultant joints decreased, and the joints fractured through the fusion zone during tensile testing. The fracture surfaces were examined by scanning electron microscopy and the microhardness distribution in the joints was measured by using a Vickers microhardness tester.
基金The National Key Research and Development Program of China(No.2017YFC0805100),the National Natural Science Foundation of China(No.51578137)the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Open Research Fund Program of Jiangsu Key Laboratory of Engineering Mechanics.
文摘The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded cast steel joint was analyzed to determine the optimal mesh size.Based on the stress field analysis of the finite element model of the welded cast steel joint at the weld toe and weld root,the sharp model of the extrapolation notch stress method was applied to derive the effective notch stress of the rounded model belonging to the effective notch stress method,in which the key problem is to calculate the extrapolation point C,and the extrapolation point C has an exponential function relationship with the geometric parameters of the welded cast steel joint.By setting different values of geometric parameters,the corresponding value of parameter C is calculated,and then the functional relationship between the extrapolation point C and the geometric parameters can be obtained by the multiple linear regression analysis.Meanwhile,the fatigue life evaluation of the girth butt weld within welded cast steel joints based on the effective notch stress was performed according to the guideline recommended by the IIW(International Institute of Welding).The results indicate that the extrapolation notch stress method can effectively simplify the process of calculating the effective notch stress and accurately evaluate the fatigue life of the girth butt weld within welded cast steel joints.
文摘In order to investigate the laws of variation on tensile strength of butt welded joint post high temperatures, the wide plate tension tests for butt welded joint were conducted after cooling down from different high temperatures. The tests indicate that specimens appear ductile fracture at the steel plate during the tension tests after cooling down. The maximum temperatures undergone and the cooling pattern are major factors influencing tensile strength of butt welded joint post high temperatures. The tensile strength mostly reduces by 8% within 900℃. Based on the experimental results, the paper proposes the calculation formulas of tensile strength of butt welded joint post high temperatures. The conclusions of the paper supply references for evaluation damage and reinforcement of steel structure post fire.
基金supported by the National Natural Science Foundation(No.51265013)the Natural Science Foundation of Jiangxi Province(No.20151BAB206007)
文摘The fatigue properties of friction stir welded （FSW） butt joint and base metal of MB8 magnesium alloy were investigated. The comparative fatigue tests were carried out using EHF-EM2OOK2-070-IA fatigue testing machine for both FSW butt joint and base metal specimens. The fatigue fractures were observed and analyzed using a scanning electron microscope of JSM-6063LA type. The experimental results show that the fatigue performance of the FSW butt joint of MB8 magnesium alloy is sharply decreased. The conditional fatigue limit （2 x 106） of base metal and welded butt joint is about 77.44 MPa and 49. 91 MPa, respectively. The conditional fatigue limit （2 x 106 ） of the welded butt joint is 64.45% of that of base metal. The main reasons are that the welding can lead to stress concentration in the flash area, tensile welding residual stress in the welded joint（ The residual stress value was 30. 5 MPa）, as well as the grain size is not uniform in the heat-affected zone. The cleavage steps or quasi-cleavage patterns present on the fatigue fracture surface, the fracture type of the FSW butt joint belongs to a brittle fracture.
基金The authors are grateful to be financially supported by Projects of Natural Science Foundation of Heilongjiang Province （No. E201458） , State Key Lab of Advanced Welding and Joining, Har- bin Institute of Technology （AWJ-M13-14） and Hei longjiang Prov- ince Department of Education （12541679）.
文摘In order to improve the bending load-carrying capacity （BLCC） of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors （SCF） at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.
基金The authors are grateful for the financial support of the National Key Research and Development Program of China(2017YFC0703500).
文摘The construction of grouting butt joints of bamboo tubes is simple and efficient.However,when the joint is bent,the low tensile strength of the mortar easily leads to cracking of the mortar prior to the failure of the bamboo tube.In this paper,a comparative test of the bending capacity was performed on grouting butt joints reinforced by nonperforated,fully perforated,and semiperforated steel plates embedded in bamboo tubes to obtain the loaddisplacement curves and ultimate bearing capacity of various specimens.The strengthening effect of CFRP pasted on bamboo tubes was also studied.The results show that the opening at the end of the steel plate is beneficial to resist the slip between the mortar and steel plate,while the complete section in the middle of the steel plate is conducive to making full use of the tensile strength of the steel plate.Therefore,it is best to insert the semiperforated steel plate with openings in the end and without openings in the middle into the mortar to enhance the bending properties of the grouting butt joint,which can make the failure mode of the joint change from brittle failure of mortar to ductile compression failure of bamboo tube.In addition,pasting CFRP sheets on the external wall of the bamboo tube helps to reduce the tensile stress of the mortar,while increasing the width of the steel plate can increase the bending moment of inertia of the mixture of the steel plate and mortar.These two complementary measures are very effective in delaying the cracking of the bamboo tube and improving the bending capacity of the joint.
基金the funding support from China Scholarship Council under the grant CSC No. 202106150028。
文摘The disposal of discarded E-cigarette butts(E-CBs) presents significant environmental challenges due to their detrimental impacts on ecosystems. To find an environmentally sustainable method for managing this waste, the potential for recycling E-CBs in asphalt pavements was investigated in this study. By focusing on the two primary components of E-CBs, namely cellulose fibre and polylactic acid(PLA), this research introduced a novel approach for recycling E-CBs in stone mastic asphalt(SMA) as a fibre additive in engineered pellet form. The prepared fibre pellets were directly added to aggregates to produce the SMA mixture. The resulting mixtures underwent a comprehensive evaluation through a series of standardized laboratory tests, including assessments of volumetric properties, indirect tensile strength(ITS), stiffness modulus, moisture susceptibility, and rutting resistance. The results were compared with SMA mixtures containing conventional cellulose fibres. Additionally, to examine the potential influence of PLA, a third mixture was prepared, incorporating both cellulose fibre and PLA. The findings indicate that the SMA using pelletized fibre can satisfy the technical specifications regarding the tests performed in this study, showing higher ITS and rutting resistance compared to the reference mixture. Moreover, the incorporation of PLA plastic reduced air void content and improved tensile strength, stiffness, and rutting resistance. This study highlights the potential for recycling E-CBs in asphalt mixtures, offering technical support for further development of sustainable recycling methods for this waste.
文摘China ranks first in the world as the number of smokers. The environmental pollution and recycling problems of waste cigarette butts are becoming more and more serious. How to make better reuse of waste cigarette butts has been taken action by some countries and regions in the world. In order to study the utilization value of the cigarette butt in road performance, this test takes No. 70 matrix bitumen and waste tobacco as raw material. The optimum amount of the content of the cigarette butt in the experiment is further determined based on the test performance of the modified asphalt mixture and the modified bitumen mixture is prepared by the addition method. The performance indexes of modified bituminous mixture with different dosages were tested and studied. Combined with production and economic realities, the optimum cigarette butt content of modified asphalt mixture is determined to make the road performance optimal. This paper focuses on the determination of the best bituminous content of the bituminous mixture. Through the toxicity test of the leachate published abroad to reflect the pollution of the cigarette butt to the environment and analyze the harm to the environment, combined with the development of global reusing technology and the economic benefits brought by cigarette butts, the prospect of the utilization of waste cigarette butts is forecasted.
文摘The hardware and software design of two digital control systems based on 80C196KB MCU for flash butt welder is introduced in this paper.The welding power supply is made of six-phase half-wave rectifier.The welding outer characteristic of welding machine is realized by digital PI algorithm with the voltage close-loop feedback.The flashing curve is finished by elec- tric-hydraulic servo valve.The process control system transfers datum with power supply system by a serial communication inter- face.The parameters of the control systems are collected by photoelectrical seclusion to avoid the disturbing of the electromagnetism in welding process.
文摘Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.
