Edge defects significantly impact the forming quality of Mg/Al composite plates during the rolling process.This study aims to develop an effective rolling technique to suppress these defects.First,an enhanced Lemaitre...Edge defects significantly impact the forming quality of Mg/Al composite plates during the rolling process.This study aims to develop an effective rolling technique to suppress these defects.First,an enhanced Lemaitre damage model with a generalized stress state damage prediction mechanism was used to evaluate the key mechanical factors contributing to defect formation.Based on this evaluation,an embedded composite rolling technique was proposed.Subsequently,comparative validation was conducted at 350℃ with a 50% reduction ratio.Results showed that the plates rolled using the embedded composite rolling technique had smooth surfaces and edges,with no macroscopic cracks observed.Numerical simulation indicated that,compared to conventional processes,the proposed technique reduced the maximum edge stress triaxiality of the plates from-0.02 to-1.56,significantly enhancing the triaxial compressive stress effect at the edges,which suppressed void nucleation and growth,leading to a 96%reduction in damage values.Mechanical property evaluations demonstrated that,compared to the conventional rolling process,the proposed technique improved edge bonding strength and tensile strength by approximately 67.7%and 118%,respectively.Further microstructural characterization revealed that the proposed technique,influenced by the restriction of deformation along the transverse direction(TD),weakened the plastic flow in the TD and enhanced plastic flow along the rolling direction(RD),resulting in higher grain boundary density and stronger basal texture.This,in turn,improved the toughness and transverse homogeneity of the plates.In summary,the embedded composite rolling technique provides crucial technical guidance for the preparation of Mg-based composite plates.展开更多
So far, numerous numerical studies have been conducted on the behavior of Composite Reinforced Concrete-Steel （RCS） beam-to-column connections. However, the lack of studies regarding the steel joist-concrete girder ...So far, numerous numerical studies have been conducted on the behavior of Composite Reinforced Concrete-Steel （RCS） beam-to-column connections. However, the lack of studies regarding the steel joist-concrete girder connection has yet to be addressed through comprehensive finite element methods to get an understanding of influential parameters. Hence, in this paper, composite connection of embedded steel joist in concrete girder is investigated with an appropriate finite element software, namely, ABAQUS. The validity of the proposed model is examined by the comparison made with the test data in literature. Results indicate that maximum bending capacity of the connection is achieved when embedment ratio is 1.78. Moreover, double web angles in the embedment region significantly reduce the embedment length required to achieve the maximum bending capacity. Finally, damage analyses show that bending capacity of concrete girder is slightly reduced in the connection zone.展开更多
Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitorin...Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitoring.In this paper,temperature and residual strain during fatigue of a carbon fiber reinforced polymer(CFRP)are investigated.Four autoclaved CFRP beam specimens,with fiber Bragg grating(FBG)sensors and thermocouples embedded at selected locations,are subjected to three-point bending cyclic loading on the BOSE testing machine for fatigue testing.Thennocouples are used to measure the temperature while FBGs can sense the temperature and strain as well.Seven tests in total are conducted at different frequencies,and each test lasts for several days.From the experimental results,transient steep peaks of temperature increases(up to 2.3℃)are discovered at the beginning of the load.The following constant temperature increments are around 1.0℃,which is not relevant to frequencies from 0.1 Hz to 20 Hz and suspected due to fatigue.Residual strains of 1×10^-5-2×10^-5 during fatigue,fading away rapidly when unloading,are also reported.Embedded FBGs here are validated to sense temperature and strains in composite structures,which demonstrates promising potentials in structure monitoring fields.CFRP are verified to have an excellent performance during fatigue with low temperature increase and residual strain.展开更多
Laser-assisted gas nitriding of selective Ti-6Al-4V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen.Systematic variation of processing ...Laser-assisted gas nitriding of selective Ti-6Al-4V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen.Systematic variation of processing parameters allowed microdendritic Ti N surface coatings to be formed having thicknesses ranging from a few tens of microns to several hundred microns,with TiN dendrite microstructure volume fractions ranging from 0.6 to 0.75;and corresponding Vickers microindentation hardness values ranging from^7.5 GPa–9.5 GPa.Embedded TiN hard layers ranging from 50μm to 150μm thick were also fabricated in the laser-beam additively manufactured Ti-6Al-4V alloy producing prototype,hybrid,planar composites having alternating,ductile Ti-6Al-4V layers with a hardness of^4.5 GPa and a stiff,TiN layer with a hardness of^8.5 GPa.The results demonstrate prospects for fabricating novel,additively manufactured components having selective,hard,wear and corrosion resistant coatings along with periodic,planar or complex metal matrix composite regimes exhibiting superior toughness and related mechanical properties.展开更多
Stretchable organic light-emitting diodes(OLEDs)are important components for flexible/wearable electronics.However,the efficiency of the existing stretchable OLEDs is still much lower as compared with their rigid coun...Stretchable organic light-emitting diodes(OLEDs)are important components for flexible/wearable electronics.However,the efficiency of the existing stretchable OLEDs is still much lower as compared with their rigid counterparts,one of the main reasons being the lack of ideal flexible transparent electrodes.Herein,we propose and develop a printed embedded metal composite electrode(PEMCE)strategy that enables the fabrication of ultra-thin,highly flexible transparent electrodes with robust mechanical properties.With the flexible transparent electrodes serves as the anodes,flexible/stretchable white OLEDs have been successfully constructed,achieving a current efficiency of up to 77.4 cd A^(-1)and a maximum luminance of 34787 cd m^(-2).The current efficiency of the resulting stretchable OLEDs is the highest ever reported for flexible/stretchable white OLEDs,which is about 1.2 times higher than that of the reference rigid devices based on ITO/glass electrodes.The excellent optoelectronic properties of the printed embedded transparent electrodes and the light extraction effect of the Ag-mesh account for the significant increase in current efficiency.Remarkably,the electroluminescence performance still retains~83%of the original luminance even after bending the device 2000 cycles at a radii of~0.5 mm.More importantly,the device can withstand tensile strains of up to~100%,and even mechanical deformation of 90%tensile strain does not result in a significant loss of electroluminescence performance with current efficiency and luminance maintained at over 85%.The results confirm that the PEMCE strategy is effective for constructing ultra-flexible transparent electrodes,showing great promise for use in a variety of flexible/stretchable electronics.展开更多
基金supported by National Key Research and Development Program(2018YFA0707300)Major Program of National Natural Science Foundation of China(U22A20188).
文摘Edge defects significantly impact the forming quality of Mg/Al composite plates during the rolling process.This study aims to develop an effective rolling technique to suppress these defects.First,an enhanced Lemaitre damage model with a generalized stress state damage prediction mechanism was used to evaluate the key mechanical factors contributing to defect formation.Based on this evaluation,an embedded composite rolling technique was proposed.Subsequently,comparative validation was conducted at 350℃ with a 50% reduction ratio.Results showed that the plates rolled using the embedded composite rolling technique had smooth surfaces and edges,with no macroscopic cracks observed.Numerical simulation indicated that,compared to conventional processes,the proposed technique reduced the maximum edge stress triaxiality of the plates from-0.02 to-1.56,significantly enhancing the triaxial compressive stress effect at the edges,which suppressed void nucleation and growth,leading to a 96%reduction in damage values.Mechanical property evaluations demonstrated that,compared to the conventional rolling process,the proposed technique improved edge bonding strength and tensile strength by approximately 67.7%and 118%,respectively.Further microstructural characterization revealed that the proposed technique,influenced by the restriction of deformation along the transverse direction(TD),weakened the plastic flow in the TD and enhanced plastic flow along the rolling direction(RD),resulting in higher grain boundary density and stronger basal texture.This,in turn,improved the toughness and transverse homogeneity of the plates.In summary,the embedded composite rolling technique provides crucial technical guidance for the preparation of Mg-based composite plates.
文摘So far, numerous numerical studies have been conducted on the behavior of Composite Reinforced Concrete-Steel （RCS） beam-to-column connections. However, the lack of studies regarding the steel joist-concrete girder connection has yet to be addressed through comprehensive finite element methods to get an understanding of influential parameters. Hence, in this paper, composite connection of embedded steel joist in concrete girder is investigated with an appropriate finite element software, namely, ABAQUS. The validity of the proposed model is examined by the comparison made with the test data in literature. Results indicate that maximum bending capacity of the connection is achieved when embedment ratio is 1.78. Moreover, double web angles in the embedment region significantly reduce the embedment length required to achieve the maximum bending capacity. Finally, damage analyses show that bending capacity of concrete girder is slightly reduced in the connection zone.
文摘Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitoring.In this paper,temperature and residual strain during fatigue of a carbon fiber reinforced polymer(CFRP)are investigated.Four autoclaved CFRP beam specimens,with fiber Bragg grating(FBG)sensors and thermocouples embedded at selected locations,are subjected to three-point bending cyclic loading on the BOSE testing machine for fatigue testing.Thennocouples are used to measure the temperature while FBGs can sense the temperature and strain as well.Seven tests in total are conducted at different frequencies,and each test lasts for several days.From the experimental results,transient steep peaks of temperature increases(up to 2.3℃)are discovered at the beginning of the load.The following constant temperature increments are around 1.0℃,which is not relevant to frequencies from 0.1 Hz to 20 Hz and suspected due to fatigue.Residual strains of 1×10^-5-2×10^-5 during fatigue,fading away rapidly when unloading,are also reported.Embedded FBGs here are validated to sense temperature and strains in composite structures,which demonstrates promising potentials in structure monitoring fields.CFRP are verified to have an excellent performance during fatigue with low temperature increase and residual strain.
基金provided through the MSI STEM Research&Development Consortium sponsored by the U.S.Army via cooperative agreement#W911SR-14-2-0001 project number 0025。
文摘Laser-assisted gas nitriding of selective Ti-6Al-4V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen.Systematic variation of processing parameters allowed microdendritic Ti N surface coatings to be formed having thicknesses ranging from a few tens of microns to several hundred microns,with TiN dendrite microstructure volume fractions ranging from 0.6 to 0.75;and corresponding Vickers microindentation hardness values ranging from^7.5 GPa–9.5 GPa.Embedded TiN hard layers ranging from 50μm to 150μm thick were also fabricated in the laser-beam additively manufactured Ti-6Al-4V alloy producing prototype,hybrid,planar composites having alternating,ductile Ti-6Al-4V layers with a hardness of^4.5 GPa and a stiff,TiN layer with a hardness of^8.5 GPa.The results demonstrate prospects for fabricating novel,additively manufactured components having selective,hard,wear and corrosion resistant coatings along with periodic,planar or complex metal matrix composite regimes exhibiting superior toughness and related mechanical properties.
基金National Natural Science Foundation of China,Grant/Award Numbers:21835003,21422402,21674050,62005126National Key Basic Research Program of China,Grant/Award Numbers:2014CB648300,2017YFB0404501+7 种基金Natural Science Foundation of Jiangsu Province,Grant/Award Numbers:BE2019120,BK20140060Program for Jiangsu Specially-Appointed Professor,Grant/Award Number:RK030STP15001Six Talent Peaks Project of Jiangsu Province,Grant/Award Number:TD-XCL-009333 Project of Jiangsu Province,Grant/Award Number:BRA2017402Leading Talent of Technological Innovation of National Ten-Thousands Talents Program of ChinaExcellent Scientific and Technological Innovative Teams of Jiangsu Higher Education Institutions,Grant/Award Number:TJ217038NUPT Scientific Foundation,Grant/Award Number:NY220152Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Stretchable organic light-emitting diodes(OLEDs)are important components for flexible/wearable electronics.However,the efficiency of the existing stretchable OLEDs is still much lower as compared with their rigid counterparts,one of the main reasons being the lack of ideal flexible transparent electrodes.Herein,we propose and develop a printed embedded metal composite electrode(PEMCE)strategy that enables the fabrication of ultra-thin,highly flexible transparent electrodes with robust mechanical properties.With the flexible transparent electrodes serves as the anodes,flexible/stretchable white OLEDs have been successfully constructed,achieving a current efficiency of up to 77.4 cd A^(-1)and a maximum luminance of 34787 cd m^(-2).The current efficiency of the resulting stretchable OLEDs is the highest ever reported for flexible/stretchable white OLEDs,which is about 1.2 times higher than that of the reference rigid devices based on ITO/glass electrodes.The excellent optoelectronic properties of the printed embedded transparent electrodes and the light extraction effect of the Ag-mesh account for the significant increase in current efficiency.Remarkably,the electroluminescence performance still retains~83%of the original luminance even after bending the device 2000 cycles at a radii of~0.5 mm.More importantly,the device can withstand tensile strains of up to~100%,and even mechanical deformation of 90%tensile strain does not result in a significant loss of electroluminescence performance with current efficiency and luminance maintained at over 85%.The results confirm that the PEMCE strategy is effective for constructing ultra-flexible transparent electrodes,showing great promise for use in a variety of flexible/stretchable electronics.
