Wire-fed laser-arc directed energy deposition(Wire-fed LA-DED)Technol.improves production speed while maintaining high quality and is particularly suited for manufacturing large,complex aluminum or titanium alloy comp...Wire-fed laser-arc directed energy deposition(Wire-fed LA-DED)Technol.improves production speed while maintaining high quality and is particularly suited for manufacturing large,complex aluminum or titanium alloy components.The geometry of the weld bead(height and width)is influenced by multiple intricate parameters and variables during the manufacturing process.Accurately predicting the weld bead shape enables precise control over the surface flatness of the part,helping to prevent defects such as lack of fusion.This significantly reduces dimensional redundancy,enhances printing efficiency,and optimizes material usage.In this study,a quadratic regression prediction model for weld bead geometry was developed using the response surface methodology(RSM),with predictions generated through several machine learning models.These models included the back-propagation neural network(BPNN),support vector regression(SVR),multi-output support vector regression(MOSVR),extreme learning machine(ELM),and a differential evolution-optimized MOSVR(DE-MOSVR)model.Grid search and cross-validation techniques were utilized to identify the optimal parameters for each model to achieve the best predictive performance.A comparison of these models was conducted,followed by an evaluation of their generalization capabilities using an additional 20 sets of test data.The most accurate predictive model was selected based on a comprehensive assessment.The results showed that the DE-MOSVR model outperformed the others,achieving mean squared error,root mean squared error,mean absolute error,and R^(2) values for width(height)predictions of 0.0411(0.0041),0.2028(0.0639),0.1671(0.0550),and 0.9434(0.9433),respectively.It demonstrated the smallest deviation in the validation set,with mean deviations of 1.97% and 1.68%,respectively.The model we developed was validated through the production of prototype parts,providing valuable reference and guidance for predicting and modeling weld bead morphology in the Wire-fed LA-DED process.展开更多
We report on a detailed analysis of the mode changing,nulling and subpulse drifting behavior of the conal triple pulsar B2319+60 at 1.5 GHz observed with the Nanshan 25 m radio telescope.The pulsar’s profile can be i...We report on a detailed analysis of the mode changing,nulling and subpulse drifting behavior of the conal triple pulsar B2319+60 at 1.5 GHz observed with the Nanshan 25 m radio telescope.The pulsar’s profile can be interpreted as resulting from a sightline traverse which cuts across an outer cone and tangentially grazes an inner cone.About 30 per cent of nulls are found to create alternating bunches of nulls and emission in a quasi-periodic manner with an averaged fluctuation rate of about four rotation periods(P_(1)).The presence of two distinct drift modes(A and ABN)plus a phase-stationary non-drift emission mode(B)is confirmed,and each corresponds to a different pulse profile.The mode A is dominated by a phase modulation in the trailing component with a circulation time of around 7P_(1).In addition to a 3P_(1)phase modulation in the leading component,mode ABN presents an amplitude modulation in the leading and trailing components with a period of around 40P_(1).The emission region and geometry remain constant during mode changing.The diversity seen in the individual pulse behavior of the pulsar B2319+60 provides a unique window into the emission physics.展开更多
In this study,a wire oscillating laser additive manufacturing(O-WLAM)process was used to deposit 2319 aluminum alloy samples.The optimization of the deposition process parameters made it possible to obtain samples wit...In this study,a wire oscillating laser additive manufacturing(O-WLAM)process was used to deposit 2319 aluminum alloy samples.The optimization of the deposition process parameters made it possible to obtain samples with smooth surfaces and extremely low porosities.The effects of the deposition parameters on the formability and evolution of the microstructure and mechanical properties before and after heat treatment were studied.The oscillating laser deposition of 2319 aluminum alloy,especially the circular oscillation mode,significantly reduced the porosity and improved the process stability and formability compared with non-oscillating laser deposition.There were clear boundaries between the deposition units in the deposition state,the interior of which was dominated by columnar crystals with many rod-and point-shaped precipitates.After the heat treatment,theθphase was significantly dissolved.The residual dot-and rod-shapedθ'phases were dispersedly distributed,exhibiting an obvious precipitation-hardening effect.The samples in the as-deposited state had a tensile strength of 245–265 MPa,an elongation of approximately 12.6%,and an 87 HV microhardness.After heat treatment at 530°C for 20 h and aging at 175°C for 18 h,the tensile strength,elongation,and microhardness reached 425–440 MPa,approximately 10%,and 153 HV,respectively.The performance improved significantly without significant anisotropy.Compared with the samples produced by wire arc additive manufacturing(WAAM),the tensile strength increased by approximately 10%,and the strength and microhardness were significantly improved.展开更多
采用电弧熔丝增材制造(WAAM)制备了圆柱面双层金字塔点阵结构,分析了圆柱面金字塔点阵结构的空间特征,建立了单元杆杆长数学模型,进行了圆柱面切片和路径规划,揭示了送丝速度、冷金属过渡技术(cold metal transfer, CMT)周期数和电弧枪...采用电弧熔丝增材制造(WAAM)制备了圆柱面双层金字塔点阵结构,分析了圆柱面金字塔点阵结构的空间特征,建立了单元杆杆长数学模型,进行了圆柱面切片和路径规划,揭示了送丝速度、冷金属过渡技术(cold metal transfer, CMT)周期数和电弧枪偏移量与单元杆直径和倾角的关系。结果表明,圆柱面金字塔点阵结构具有旋转体的空间特征,其单元杆杆长随着点阵层数的增加而逐渐增加,圆柱面切片可获得增材制造路径点,通过调节送丝速度和CMT周期数可实现在2.20~5.02 mm的范围内精确控制单元杆直径,通过调节送丝速度和电弧枪偏移量可实现在30°~90°的范围内精确控制单元杆倾角。利用WAAM制备了包含300个点阵单胞的圆柱面双层金字塔点阵结构,其单元杆直径最大误差不超过2.3%,单元杆倾角最大误差不超过1.8%。展开更多
基金supported by Natural Science Foundation of Shandong Province(Grant No.ZR202212010161)Natural Science Foundation of Qingdao(Grant No.23-2-1-83-zyyd-jch)+1 种基金Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515110116)the National Natural Science Foundation of China(Grant No.52405359).
文摘Wire-fed laser-arc directed energy deposition(Wire-fed LA-DED)Technol.improves production speed while maintaining high quality and is particularly suited for manufacturing large,complex aluminum or titanium alloy components.The geometry of the weld bead(height and width)is influenced by multiple intricate parameters and variables during the manufacturing process.Accurately predicting the weld bead shape enables precise control over the surface flatness of the part,helping to prevent defects such as lack of fusion.This significantly reduces dimensional redundancy,enhances printing efficiency,and optimizes material usage.In this study,a quadratic regression prediction model for weld bead geometry was developed using the response surface methodology(RSM),with predictions generated through several machine learning models.These models included the back-propagation neural network(BPNN),support vector regression(SVR),multi-output support vector regression(MOSVR),extreme learning machine(ELM),and a differential evolution-optimized MOSVR(DE-MOSVR)model.Grid search and cross-validation techniques were utilized to identify the optimal parameters for each model to achieve the best predictive performance.A comparison of these models was conducted,followed by an evaluation of their generalization capabilities using an additional 20 sets of test data.The most accurate predictive model was selected based on a comprehensive assessment.The results showed that the DE-MOSVR model outperformed the others,achieving mean squared error,root mean squared error,mean absolute error,and R^(2) values for width(height)predictions of 0.0411(0.0041),0.2028(0.0639),0.1671(0.0550),and 0.9434(0.9433),respectively.It demonstrated the smallest deviation in the validation set,with mean deviations of 1.97% and 1.68%,respectively.The model we developed was validated through the production of prototype parts,providing valuable reference and guidance for predicting and modeling weld bead morphology in the Wire-fed LA-DED process.
基金partially supported by the National Natural Science Foundation of China(NSFC,Grant Nos.U1631106,U1838109,12133004,12041304 and 12041301)the National SKA Program of China(2020SKA0120100)+5 种基金supported by the 2021 project Xinjiang Uygur Autonomous Region of China for Tianshan elitessupported by the Natural Science Foundation of Shanxi Province(20210302123083)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2021L470)supported by the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2021L480)supported by the CAS Jianzhihua projectsupported by the 2018 project of Xinjiang Uygur Autonomous Region of China for flexibly fetching upscale talents。
文摘We report on a detailed analysis of the mode changing,nulling and subpulse drifting behavior of the conal triple pulsar B2319+60 at 1.5 GHz observed with the Nanshan 25 m radio telescope.The pulsar’s profile can be interpreted as resulting from a sightline traverse which cuts across an outer cone and tangentially grazes an inner cone.About 30 per cent of nulls are found to create alternating bunches of nulls and emission in a quasi-periodic manner with an averaged fluctuation rate of about four rotation periods(P_(1)).The presence of two distinct drift modes(A and ABN)plus a phase-stationary non-drift emission mode(B)is confirmed,and each corresponds to a different pulse profile.The mode A is dominated by a phase modulation in the trailing component with a circulation time of around 7P_(1).In addition to a 3P_(1)phase modulation in the leading component,mode ABN presents an amplitude modulation in the leading and trailing components with a period of around 40P_(1).The emission region and geometry remain constant during mode changing.The diversity seen in the individual pulse behavior of the pulsar B2319+60 provides a unique window into the emission physics.
基金National Natural Science Foundation of China(Grant No.52175370).
文摘In this study,a wire oscillating laser additive manufacturing(O-WLAM)process was used to deposit 2319 aluminum alloy samples.The optimization of the deposition process parameters made it possible to obtain samples with smooth surfaces and extremely low porosities.The effects of the deposition parameters on the formability and evolution of the microstructure and mechanical properties before and after heat treatment were studied.The oscillating laser deposition of 2319 aluminum alloy,especially the circular oscillation mode,significantly reduced the porosity and improved the process stability and formability compared with non-oscillating laser deposition.There were clear boundaries between the deposition units in the deposition state,the interior of which was dominated by columnar crystals with many rod-and point-shaped precipitates.After the heat treatment,theθphase was significantly dissolved.The residual dot-and rod-shapedθ'phases were dispersedly distributed,exhibiting an obvious precipitation-hardening effect.The samples in the as-deposited state had a tensile strength of 245–265 MPa,an elongation of approximately 12.6%,and an 87 HV microhardness.After heat treatment at 530°C for 20 h and aging at 175°C for 18 h,the tensile strength,elongation,and microhardness reached 425–440 MPa,approximately 10%,and 153 HV,respectively.The performance improved significantly without significant anisotropy.Compared with the samples produced by wire arc additive manufacturing(WAAM),the tensile strength increased by approximately 10%,and the strength and microhardness were significantly improved.
文摘采用电弧熔丝增材制造(WAAM)制备了圆柱面双层金字塔点阵结构,分析了圆柱面金字塔点阵结构的空间特征,建立了单元杆杆长数学模型,进行了圆柱面切片和路径规划,揭示了送丝速度、冷金属过渡技术(cold metal transfer, CMT)周期数和电弧枪偏移量与单元杆直径和倾角的关系。结果表明,圆柱面金字塔点阵结构具有旋转体的空间特征,其单元杆杆长随着点阵层数的增加而逐渐增加,圆柱面切片可获得增材制造路径点,通过调节送丝速度和CMT周期数可实现在2.20~5.02 mm的范围内精确控制单元杆直径,通过调节送丝速度和电弧枪偏移量可实现在30°~90°的范围内精确控制单元杆倾角。利用WAAM制备了包含300个点阵单胞的圆柱面双层金字塔点阵结构,其单元杆直径最大误差不超过2.3%,单元杆倾角最大误差不超过1.8%。
