Based on analysis of the main forming methods for double-layer tube,a new short-term forming process called thixo-co-extrusion was put forward in producing double-layer tube by combining the semi-solid forming technol...Based on analysis of the main forming methods for double-layer tube,a new short-term forming process called thixo-co-extrusion was put forward in producing double-layer tube by combining the semi-solid forming technology and multi-billet extrusion technology.By means of forward extrusion with shaft,a finite element model of thixo-co-extrusion with A356/AZ91 was constructed by ABAQUS FEM software.The distributions of temperature field and velocity field as well as the contact force during thixo-co-extrusion were studied.The diffusion on the interfaces between inner and outer metals was analyzed.The simulation results show that,in the beginning of thixo-co-extrusion,the uneven wall thickness can appear.To thickness ratio of 5:5,a double layer tube with good inner and outer wall combination can be realized if VA356 is 0.12 m/s and VAZ91 is 0.20 m/s.展开更多
Electric double-layer capacitors(EDLCs)with fast frequency response are regarded as small-scale alternatives to the commercial bulky aluminum electrolytic capacitors.Creating carbon-based nanoarray electrodes with pre...Electric double-layer capacitors(EDLCs)with fast frequency response are regarded as small-scale alternatives to the commercial bulky aluminum electrolytic capacitors.Creating carbon-based nanoarray electrodes with precise alignment and smooth ion channels is crucial for enhancing EDLCs’performance.However,controlling the density of macropore-dominated nanoarray electrodes poses challenges in boosting the capacitance of line-filtering EDLCs.Herein,a simple technique to finely adjust the vertical-pore diameter and inter-spacing in three-dimensional nanoporous anodic aluminum oxide(3D-AAO)template is achieved,and 3D compactly arranged carbon tube(3D-CACT)nanoarrays are created as electrodes for symmetrical EDLCs using nanoporous 3D-AAO template-assisted chemical vapor deposition of carbon.The 3D-CACT electrodes demonstrate a high surface area of 253.0 m^(2) g^(−1),a D/G band intensity ratio of 0.94,and a C/O atomic ratio of 8.As a result,the high-density 3D-CT nanoarray-based sandwich-type EDLCs demonstrate a record high specific areal capacitance of 3.23 mF cm^(-2) at 120 Hz and exceptional fast frequency response due to the vertically aligned and highly ordered nanoarray of closely packed CT units.The 3D-CT nanoarray electrode-based EDLCs could serve as line filters in integrated circuits,aiding power system miniaturization.展开更多
The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and ...The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.展开更多
To reveal the reason of weld-line movement in hydroforming of a tailor-welded tube (TWT) with dissimilar thickness,the stress ratio of axial stress to circumferential stress is derived by mechanical analysis and analy...To reveal the reason of weld-line movement in hydroforming of a tailor-welded tube (TWT) with dissimilar thickness,the stress ratio of axial stress to circumferential stress is derived by mechanical analysis and analyzed between the thicker and thinner tubes,as well as the property of the axial strain. During TWT hydroforming,tensile strain along axial direction happens on the thinner tube. On the contrary,compressive strain happens on the thicker tube. Experiments are conducted to varify the weld-line movement regularity and strain distribution. It indicates that the weld-line moves from the thinner part to the thicker during TWT hydroforming. The thinning ratio of the thinner tube is bigger than that of the thicker tube,especially in the zone near weldline. Stress ratio difference between the thicker tube and the thinner tube is the main reason of weld-line movement and non-uniform thinning ratio distribution.展开更多
The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formabilit...The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formability of the QSTE340 welded tube. The results show that the wall thinning degree, cross-sectional deformation and springback angle increase significantly as the weld line is located on the outside of the bend compared with that located on the middle and inside, and the welded tubes produce nearly identical performance as the weld line is located on the middle and inside. The wall thickening degree decreases much as the weld line is located on the inside of the bend. So the welded tube can acquire good bending formability as the weld line is located in the region away from the outside of the bend.展开更多
Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials a...Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials and also to minimize the effect of intermetallics formed at the joint interface. The process parameters that govern FWTPET process are plunge rate, rotational speed, plunge depth, axial load and flash trap profile. Among them, the flash trap profile of the tube has a significant influence on the joint integrity. Various flash trap profiles like vertical slots, holes, zig-zag holes, and petals were made on the titanium tube welded to the stainless steel tube plate. Macroscopic and microscopic studies reveal defect-free joints. The presence of copper interlayer and intermetallics was evident from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies. The microhardness survey was presented across and along the interface. A novel test procedure called “plunge shear test” was developed to evaluate the joint properties of the welded joints. The highest shear fracture load of 31.58 kN was observed on the sample having petals as flash trap profile. The sheared surfaces were further characterized using SEM for fractography.展开更多
In cold roll forming, steel pipes are welded with different technology parameters in order to improve the steel pipe＇s quality, thus we should optimize the technology parameters for producing steel pipes. By means of...In cold roll forming, steel pipes are welded with different technology parameters in order to improve the steel pipe＇s quality, thus we should optimize the technology parameters for producing steel pipes. By means of metallographic examination, scanning electron microscope examination, hardness test, impact test, bend test, tensile test and so on, the microstructure and mechanical properties of the steel pipes were investigated. The test results show that welding defects such as crack and blowholes are not found. The microstructure of the welded metal is Widmanstatten ; the microstructure of the heat affected zone is Widmanstatten, pearlite and proeutectoid ferrite, and the base metal is pearlite and ferrite. The highest of the metal Brinell hardness is in the weld seam, followed by the heat affected zone, and the lowest is in the base metal. The microstructure of the weld metal is coarse, which results in that the toughness of the weld is the lowest, but the hardness of the welds is the highest in the weld zone. The bend angles of the weld metal present a mountainous shape with the surface energy. Only when the surface energy is of the best value, the mechanical properties of the weld metal is the best.展开更多
基金Project (2007AA03Z119) supported by the National High Technology Research and Development Program of ChinaProjects (2102029,2072012) supported by Beijing Natural Science Foundation
文摘Based on analysis of the main forming methods for double-layer tube,a new short-term forming process called thixo-co-extrusion was put forward in producing double-layer tube by combining the semi-solid forming technology and multi-billet extrusion technology.By means of forward extrusion with shaft,a finite element model of thixo-co-extrusion with A356/AZ91 was constructed by ABAQUS FEM software.The distributions of temperature field and velocity field as well as the contact force during thixo-co-extrusion were studied.The diffusion on the interfaces between inner and outer metals was analyzed.The simulation results show that,in the beginning of thixo-co-extrusion,the uneven wall thickness can appear.To thickness ratio of 5:5,a double layer tube with good inner and outer wall combination can be realized if VA356 is 0.12 m/s and VAZ91 is 0.20 m/s.
基金supported by the National Natural Science Foundation of China(91963202,52072372,52372241,52232007,12325203)HFIPS Director’s Fund(BJPY2023A07,YZJJ-GGZX-2022-01).
文摘Electric double-layer capacitors(EDLCs)with fast frequency response are regarded as small-scale alternatives to the commercial bulky aluminum electrolytic capacitors.Creating carbon-based nanoarray electrodes with precise alignment and smooth ion channels is crucial for enhancing EDLCs’performance.However,controlling the density of macropore-dominated nanoarray electrodes poses challenges in boosting the capacitance of line-filtering EDLCs.Herein,a simple technique to finely adjust the vertical-pore diameter and inter-spacing in three-dimensional nanoporous anodic aluminum oxide(3D-AAO)template is achieved,and 3D compactly arranged carbon tube(3D-CACT)nanoarrays are created as electrodes for symmetrical EDLCs using nanoporous 3D-AAO template-assisted chemical vapor deposition of carbon.The 3D-CACT electrodes demonstrate a high surface area of 253.0 m^(2) g^(−1),a D/G band intensity ratio of 0.94,and a C/O atomic ratio of 8.As a result,the high-density 3D-CT nanoarray-based sandwich-type EDLCs demonstrate a record high specific areal capacitance of 3.23 mF cm^(-2) at 120 Hz and exceptional fast frequency response due to the vertically aligned and highly ordered nanoarray of closely packed CT units.The 3D-CT nanoarray electrode-based EDLCs could serve as line filters in integrated circuits,aiding power system miniaturization.
文摘The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.
基金Sponsored by the National Natural Science Foundation of China(Grant No 50575051)Program for New Century Excellent Talents in University(Grant No NCET-07-0237)
文摘To reveal the reason of weld-line movement in hydroforming of a tailor-welded tube (TWT) with dissimilar thickness,the stress ratio of axial stress to circumferential stress is derived by mechanical analysis and analyzed between the thicker and thinner tubes,as well as the property of the axial strain. During TWT hydroforming,tensile strain along axial direction happens on the thinner tube. On the contrary,compressive strain happens on the thicker tube. Experiments are conducted to varify the weld-line movement regularity and strain distribution. It indicates that the weld-line moves from the thinner part to the thicker during TWT hydroforming. The thinning ratio of the thinner tube is bigger than that of the thicker tube,especially in the zone near weldline. Stress ratio difference between the thicker tube and the thinner tube is the main reason of weld-line movement and non-uniform thinning ratio distribution.
基金Supported by National Natural Science Foundation of China (No. 50875216)
文摘The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formability of the QSTE340 welded tube. The results show that the wall thinning degree, cross-sectional deformation and springback angle increase significantly as the weld line is located on the outside of the bend compared with that located on the middle and inside, and the welded tubes produce nearly identical performance as the weld line is located on the middle and inside. The wall thickening degree decreases much as the weld line is located on the inside of the bend. So the welded tube can acquire good bending formability as the weld line is located in the region away from the outside of the bend.
基金financial support provided by UGC-DAE-CSR (CSR-KN/CRS-04/201213/738) through fellowship
文摘Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials and also to minimize the effect of intermetallics formed at the joint interface. The process parameters that govern FWTPET process are plunge rate, rotational speed, plunge depth, axial load and flash trap profile. Among them, the flash trap profile of the tube has a significant influence on the joint integrity. Various flash trap profiles like vertical slots, holes, zig-zag holes, and petals were made on the titanium tube welded to the stainless steel tube plate. Macroscopic and microscopic studies reveal defect-free joints. The presence of copper interlayer and intermetallics was evident from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies. The microhardness survey was presented across and along the interface. A novel test procedure called “plunge shear test” was developed to evaluate the joint properties of the welded joints. The highest shear fracture load of 31.58 kN was observed on the sample having petals as flash trap profile. The sheared surfaces were further characterized using SEM for fractography.
文摘In cold roll forming, steel pipes are welded with different technology parameters in order to improve the steel pipe＇s quality, thus we should optimize the technology parameters for producing steel pipes. By means of metallographic examination, scanning electron microscope examination, hardness test, impact test, bend test, tensile test and so on, the microstructure and mechanical properties of the steel pipes were investigated. The test results show that welding defects such as crack and blowholes are not found. The microstructure of the welded metal is Widmanstatten ; the microstructure of the heat affected zone is Widmanstatten, pearlite and proeutectoid ferrite, and the base metal is pearlite and ferrite. The highest of the metal Brinell hardness is in the weld seam, followed by the heat affected zone, and the lowest is in the base metal. The microstructure of the weld metal is coarse, which results in that the toughness of the weld is the lowest, but the hardness of the welds is the highest in the weld zone. The bend angles of the weld metal present a mountainous shape with the surface energy. Only when the surface energy is of the best value, the mechanical properties of the weld metal is the best.
