The pulsed power ultrasonic-assisted gas metal arc welding(PU-GMAW)is a new development hybrid welding method.The influences of the pulsed power ultrasonic on the microstructure evolution of the welded joint of Al-Cu ...The pulsed power ultrasonic-assisted gas metal arc welding(PU-GMAW)is a new development hybrid welding method.The influences of the pulsed power ultrasonic on the microstructure evolution of the welded joint of Al-Cu alloy were investigated by using scanning electron microscopy,transmission electron microscope and electron back scattering diffraction.The results showed that the efficient heat input in the PU-GMAW was increased by above 100%compared with the traditional GMAW.The grain and eutectic of the PU-GMAW weld seam were refined compared with that of the GMAW.Cavitation and acoustic streaming induced the dendrite fragmentation(α-Al)and heterogeneous nucleation,which were the main reasons for the grain refinement.The microhardness of the PU-GMAW welded joint was improved compared with that of the GMAW owing to the change of the eutectic and grain.展开更多
Ultrasound-magnetic field coaxial hybrid Gas Tungsten Arc Welding(U-M-GTAW)is proposed as a means to control arc characteristics.The arc characteristics and the mechanism to change them,in an ultrasound-magnetic field...Ultrasound-magnetic field coaxial hybrid Gas Tungsten Arc Welding(U-M-GTAW)is proposed as a means to control arc characteristics.The arc characteristics and the mechanism to change them,in an ultrasound-magnetic field coaxial hybrid GTAW,were studied by both experimental and theoretical analyses.The results showed that a periodic rotation and compression of the arc shape were obtained in U-M-GTAW and the arc energy was also enhanced.The most obvious compression of the arc shape in U-M-GTAW was obtained,compared with GTAW,M-GTAW and U-GTAW.At the same time,a periodic rotation of the arc was observed in U-M-GTAW.The geometric parameters of the arc shape in U-M-GTAW are reduced more than double compared with traditional GTAW.The arc voltage in the hybrid GTAW was increased,especially in the U-M-GTAW.The electromagnetic force and acoustic radiation force were the main factors for the change of arc characteristics in the U-M-GTAW.展开更多
Pulsed TIG welding–brazing process was applied to join aluminum with stainless steel dissimilar metals. Major parameters that affect the joint property significantly were identified as pulsed peak current, base curre...Pulsed TIG welding–brazing process was applied to join aluminum with stainless steel dissimilar metals. Major parameters that affect the joint property significantly were identified as pulsed peak current, base current, pulse on time,and frequency by pre-experiments. A sample was established according to central composite design. Based on the sample,response surface methodology（RSM） and artificial neural networks（ANN） were employed to predict the tensile strength of the joints separately. With RSM, a significant and rational mathematical model was established to predict the joint strength.With ANN, a modified back-propagation algorithm consisting of one input layer with four neurons, one hidden layer with eight neurons, and one output layer with one neuron was trained for predicting the strength. Compared with RSM, average relative prediction error of ANN was ／10% and it obtained more stable and precise results.展开更多
In this study,the effects of ultrasonic coaxial assisted TIG welding(U-TIG)on the formation,microstructure,and mechanical properties of TC4 titanium alloy welded joints were investigated.The results indicated that at ...In this study,the effects of ultrasonic coaxial assisted TIG welding(U-TIG)on the formation,microstructure,and mechanical properties of TC4 titanium alloy welded joints were investigated.The results indicated that at optimal ultrasonic power and welding current settings,remarkable improvements of welded joint were observed.Specifically,the weld depth-to-width ratio increased by 267%compared to conventional TIG welding,reaching 0.22.Furthermore,the microhardness of the welded seam increased by 53%,reaching 550.1 HV,while the tensile strength of the welded joint rose to 1197.7 MPa,representing a 12.2%enhancement.The compressing effect of ultrasound concentrates the energy of the arc,thereby improving the penetration depth of the welded seam.In addition,ultrasonic cavitation plays a crucial role in refining the grain structure of the weld seam,consequently enhancing its strength.展开更多
A new type of compound conduit is designed and the finite element method(FEM)is applied to analyze the mechanicalperformance of a typical compound conduit.The results of the numerical simulation confirm that the distr...A new type of compound conduit is designed and the finite element method(FEM)is applied to analyze the mechanicalperformance of a typical compound conduit.The results of the numerical simulation confirm that the distributionsof the strain,stress and the flexure distortion of the conduit are reasonable under the working conditions,and thestress and strain are continuous at the interface of the crust and the pipe liner.The conduit can endure 7.4 timesof the working load before break,which fits well with that of the experiment and means that the conduit has goodability to bear overload.The peak value of the flexure distortion of the conduit(6 m)is about 3 mm in the middlebottom of the pipeline,which also accords well with that of the experiment.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51675130)the Key Program of the National Natural Science Foundation of China(No.51435004)。
文摘The pulsed power ultrasonic-assisted gas metal arc welding(PU-GMAW)is a new development hybrid welding method.The influences of the pulsed power ultrasonic on the microstructure evolution of the welded joint of Al-Cu alloy were investigated by using scanning electron microscopy,transmission electron microscope and electron back scattering diffraction.The results showed that the efficient heat input in the PU-GMAW was increased by above 100%compared with the traditional GMAW.The grain and eutectic of the PU-GMAW weld seam were refined compared with that of the GMAW.Cavitation and acoustic streaming induced the dendrite fragmentation(α-Al)and heterogeneous nucleation,which were the main reasons for the grain refinement.The microhardness of the PU-GMAW welded joint was improved compared with that of the GMAW owing to the change of the eutectic and grain.
基金supported by the Fundamental Research Funds for the Central Universities of China(No.2572021BF02).
文摘Ultrasound-magnetic field coaxial hybrid Gas Tungsten Arc Welding(U-M-GTAW)is proposed as a means to control arc characteristics.The arc characteristics and the mechanism to change them,in an ultrasound-magnetic field coaxial hybrid GTAW,were studied by both experimental and theoretical analyses.The results showed that a periodic rotation and compression of the arc shape were obtained in U-M-GTAW and the arc energy was also enhanced.The most obvious compression of the arc shape in U-M-GTAW was obtained,compared with GTAW,M-GTAW and U-GTAW.At the same time,a periodic rotation of the arc was observed in U-M-GTAW.The geometric parameters of the arc shape in U-M-GTAW are reduced more than double compared with traditional GTAW.The arc voltage in the hybrid GTAW was increased,especially in the U-M-GTAW.The electromagnetic force and acoustic radiation force were the main factors for the change of arc characteristics in the U-M-GTAW.
基金financially supported by the National Natural Science Foundation of China (No. 50874033)
文摘Pulsed TIG welding–brazing process was applied to join aluminum with stainless steel dissimilar metals. Major parameters that affect the joint property significantly were identified as pulsed peak current, base current, pulse on time,and frequency by pre-experiments. A sample was established according to central composite design. Based on the sample,response surface methodology（RSM） and artificial neural networks（ANN） were employed to predict the tensile strength of the joints separately. With RSM, a significant and rational mathematical model was established to predict the joint strength.With ANN, a modified back-propagation algorithm consisting of one input layer with four neurons, one hidden layer with eight neurons, and one output layer with one neuron was trained for predicting the strength. Compared with RSM, average relative prediction error of ANN was ／10% and it obtained more stable and precise results.
基金supported by the National Natural Science Foundation of China(No.52305362)the State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology(No.AWJ-20M06).
文摘In this study,the effects of ultrasonic coaxial assisted TIG welding(U-TIG)on the formation,microstructure,and mechanical properties of TC4 titanium alloy welded joints were investigated.The results indicated that at optimal ultrasonic power and welding current settings,remarkable improvements of welded joint were observed.Specifically,the weld depth-to-width ratio increased by 267%compared to conventional TIG welding,reaching 0.22.Furthermore,the microhardness of the welded seam increased by 53%,reaching 550.1 HV,while the tensile strength of the welded joint rose to 1197.7 MPa,representing a 12.2%enhancement.The compressing effect of ultrasound concentrates the energy of the arc,thereby improving the penetration depth of the welded seam.In addition,ultrasonic cavitation plays a crucial role in refining the grain structure of the weld seam,consequently enhancing its strength.
文摘A new type of compound conduit is designed and the finite element method(FEM)is applied to analyze the mechanicalperformance of a typical compound conduit.The results of the numerical simulation confirm that the distributionsof the strain,stress and the flexure distortion of the conduit are reasonable under the working conditions,and thestress and strain are continuous at the interface of the crust and the pipe liner.The conduit can endure 7.4 timesof the working load before break,which fits well with that of the experiment and means that the conduit has goodability to bear overload.The peak value of the flexure distortion of the conduit(6 m)is about 3 mm in the middlebottom of the pipeline,which also accords well with that of the experiment.
