Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may ca...Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality(SQ)of the workpiece.In this work,grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding wheel.The relationship between grinding speed,SQ and subsurface damage(SSD)was well studied.With increasing grinding speed,surface roughness decreased,and SQ was greatly improved.Meanwhile,the microhardness of the grinding surface declined as the grinding speed increased.The SSD depth was almost unchanged when the grinding speed was lower than 15 m/s,then it decreased with higher grinding speeds.It was attributed to the mechanical-thermal synergistic effect in the grinding process.The results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 alloy.The conclusion in the work may also provide insight into processing other hard-to-machining materials.展开更多
Additive manufacturing(AM), or 3D printing, is an emerging technology that “adds” materials up and constructs products through a layer-by-layer procedure. Laser powder bed fusion(LPBF) is a powder-bed-based AM techn...Additive manufacturing(AM), or 3D printing, is an emerging technology that “adds” materials up and constructs products through a layer-by-layer procedure. Laser powder bed fusion(LPBF) is a powder-bed-based AM technology that can fabricate a large variety of metallic materials with excellent quality and accuracy. However, various defects such as porosity,cracks, and incursions can be generated during the printing process. As the most universal and a near-inevitable defect,porosity plays a substantial role in determining the mechanical performance of as-printed products. This work presents a comprehensive review of literatures that focused on the porosity in LPBF printed metals. The formation mechanisms,evaluation methods, effects on mechanical performance with corresponding models, and controlling methods of porosity have been illustrated and discussed in-depth. Achievements in four representative metals, namely Ti-6Al-4V, 316L, Inconel 718, and Al Si10Mg, have been critically reviewed with a statistical analysis on the correlation between porosity fraction and tensile properties. Ductility has been determined as the most sensitive property to porosity among several key tensile properties. This review also provides potential directions and opportunities to address the current porosity-related challenges.展开更多
In this paper we show that a positive superfunction on a cone behaves regularly at infinity outside a minimally thin set associated with the stationary SchrSdinger operator.
In this paper,the nonlinear potential theory in the Morrey spaces on Euclidean spaces and the Lebesgue spaces on the Carnot group are studied.According to the methods of abstract harmonic analysis in Heisenberg group ...In this paper,the nonlinear potential theory in the Morrey spaces on Euclidean spaces and the Lebesgue spaces on the Carnot group are studied.According to the methods of abstract harmonic analysis in Heisenberg group and abstract potential theory in carnot group,we mainly give some characterizations for Riesz,Bessel and Wolff potentials,and the corresponding capacities in the Morrey spaces on Carnot group.Meanwhile,we also interpret the relation among Riesz and Bessel type capacities and Housdorff content in the Morrey spaces on Carnot group.All these results above generalize the related ones in the Morrey spaces on Euclidean spaces and the Lebesgue spaces on the Carnot group.展开更多
In this paper we mainly give some characterizations for the boundedness of the weight Hardy operator, maximal operator, potential operator and singular integral operator on the vanishing generalized weak Morrey spaces...In this paper we mainly give some characterizations for the boundedness of the weight Hardy operator, maximal operator, potential operator and singular integral operator on the vanishing generalized weak Morrey spaces VWLρП,φ（Ω） with bounded setΩ .展开更多
In the paper we give some precise characterizations for the quasicontinuity on weighted Sobolev spaces with variable exponent.Moreover,under the quasicontinuous meanings we obtain the uniqueness result in the weighted...In the paper we give some precise characterizations for the quasicontinuity on weighted Sobolev spaces with variable exponent.Moreover,under the quasicontinuous meanings we obtain the uniqueness result in the weighted Sobolev spaces with variable exponent.展开更多
Aiming to solve the problem of unstable crystal size during the preparation of anhydrous magnesium carbonate,a back propagation(BP)neural network was introduced to optimize the preparation process.Using magnesite as t...Aiming to solve the problem of unstable crystal size during the preparation of anhydrous magnesium carbonate,a back propagation(BP)neural network was introduced to optimize the preparation process.Using magnesite as the raw material,a four-factor,three-level orthogonal test was designed to analyze the effects of NaHCO_(3) dosage,reaction time,temperature,and Mg(HCO_(3))_(2)concentration on the particle size of the products.A three-layer BP neural network model(topology 4-10-1)was constructed based on the experimental data,and the prediction of process parameters was realized through factor-by-factor and point-by-point training.The results showed that the best process parameters obtained from the optimization were 14 g·L^(−1)NaHCO_(3) dosage,199℃,19 h,and 0.24 mol·L^(−1)Mg(HCO_(3))_(2)concentration,corresponding to a minimum particle size of 12.06μm(which was 13.2%lower than that of the results of orthogonal tests)with an average prediction error of 3.3%.X-ray diffraction(XRD),scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FT-IR),and thermogravimetric-differential thermal analysis(TG-DTA)showed that the optimized products were pure-phase rhombic anhydrous magnesium carbonate crystals with good dispersion,verifying the effectiveness of the BP neural network in process optimization.展开更多
基金Supported by Shenzhen Municipal Science and Technology Innovation Commission of China(Grant Nos.KQTD20190929172505711,JSGG20210420091802007,GJHZ20210705141807023).
文摘Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality(SQ)of the workpiece.In this work,grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding wheel.The relationship between grinding speed,SQ and subsurface damage(SSD)was well studied.With increasing grinding speed,surface roughness decreased,and SQ was greatly improved.Meanwhile,the microhardness of the grinding surface declined as the grinding speed increased.The SSD depth was almost unchanged when the grinding speed was lower than 15 m/s,then it decreased with higher grinding speeds.It was attributed to the mechanical-thermal synergistic effect in the grinding process.The results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 alloy.The conclusion in the work may also provide insight into processing other hard-to-machining materials.
基金the National Key Research and Development Program of China[grant number 2018YFB1106301]Research and Development Program Project in Key Areas of Guangdong Province[grant number 2019B090907001 and 2019B010943001]+2 种基金Shenzhen Science and Technology Innovation Commission[grant number JCYJ20180504165824643]Natural Science Foundation of Guangdong Province[grant number 2020A1515011373]the National Natural Science Foundation of China[grant number 51971108].
文摘Additive manufacturing(AM), or 3D printing, is an emerging technology that “adds” materials up and constructs products through a layer-by-layer procedure. Laser powder bed fusion(LPBF) is a powder-bed-based AM technology that can fabricate a large variety of metallic materials with excellent quality and accuracy. However, various defects such as porosity,cracks, and incursions can be generated during the printing process. As the most universal and a near-inevitable defect,porosity plays a substantial role in determining the mechanical performance of as-printed products. This work presents a comprehensive review of literatures that focused on the porosity in LPBF printed metals. The formation mechanisms,evaluation methods, effects on mechanical performance with corresponding models, and controlling methods of porosity have been illustrated and discussed in-depth. Achievements in four representative metals, namely Ti-6Al-4V, 316L, Inconel 718, and Al Si10Mg, have been critically reviewed with a statistical analysis on the correlation between porosity fraction and tensile properties. Ductility has been determined as the most sensitive property to porosity among several key tensile properties. This review also provides potential directions and opportunities to address the current porosity-related challenges.
基金Supported by the National Natural Science Foundation of China(Grant Nos.1127104511261041+2 种基金11461053)the Natural Science Foundation of Ningxia University(Grant No.NDZR1301)Startup Foundation for Doctor Scientific Research of Ningxia University
文摘In this paper we show that a positive superfunction on a cone behaves regularly at infinity outside a minimally thin set associated with the stationary SchrSdinger operator.
基金Supported by the Natural Science Foundation of Ningxia(Grant No.2023AAC03001)the National Natural Science Foundation of China(Grant No.12261068)。
文摘In this paper,the nonlinear potential theory in the Morrey spaces on Euclidean spaces and the Lebesgue spaces on the Carnot group are studied.According to the methods of abstract harmonic analysis in Heisenberg group and abstract potential theory in carnot group,we mainly give some characterizations for Riesz,Bessel and Wolff potentials,and the corresponding capacities in the Morrey spaces on Carnot group.Meanwhile,we also interpret the relation among Riesz and Bessel type capacities and Housdorff content in the Morrey spaces on Carnot group.All these results above generalize the related ones in the Morrey spaces on Euclidean spaces and the Lebesgue spaces on the Carnot group.
基金Supported by the Natural Science Foundation of Ningxia(Grant No.NZ15055)Institution of Higher Education Scientific Research Project in Ningxia(Grant No.NGY2017011)the National Natural Science Foundation of China(Grant Nos.11261041,11361044)
文摘In this paper we mainly give some characterizations for the boundedness of the weight Hardy operator, maximal operator, potential operator and singular integral operator on the vanishing generalized weak Morrey spaces VWLρП,φ（Ω） with bounded setΩ .
基金Supported by the National Natural Science Foundation of China(Grant Nos.1126104111271045+2 种基金11361044)the Natural Science Foundation of Ningxia(Grant No.NZ15055)Research Starting Funds for Imported Talents of Ningxia University
文摘In the paper we give some precise characterizations for the quasicontinuity on weighted Sobolev spaces with variable exponent.Moreover,under the quasicontinuous meanings we obtain the uniqueness result in the weighted Sobolev spaces with variable exponent.
基金financially supported by National Natural Science Foundation of China(No.52374271&No.52404290)Liaoning Province'Xing Liao Ying Cai Program'Outstanding Young Talents Project(XLYC2403010)+1 种基金Liaoning Provincial Engineering Research Center for High-Value Utilization of Magnesite(LMKK20240101)Research Fund Project of Liaoning Provincial Education Department(SYLUGXRC+12&LJMKZ20220585).
文摘Aiming to solve the problem of unstable crystal size during the preparation of anhydrous magnesium carbonate,a back propagation(BP)neural network was introduced to optimize the preparation process.Using magnesite as the raw material,a four-factor,three-level orthogonal test was designed to analyze the effects of NaHCO_(3) dosage,reaction time,temperature,and Mg(HCO_(3))_(2)concentration on the particle size of the products.A three-layer BP neural network model(topology 4-10-1)was constructed based on the experimental data,and the prediction of process parameters was realized through factor-by-factor and point-by-point training.The results showed that the best process parameters obtained from the optimization were 14 g·L^(−1)NaHCO_(3) dosage,199℃,19 h,and 0.24 mol·L^(−1)Mg(HCO_(3))_(2)concentration,corresponding to a minimum particle size of 12.06μm(which was 13.2%lower than that of the results of orthogonal tests)with an average prediction error of 3.3%.X-ray diffraction(XRD),scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FT-IR),and thermogravimetric-differential thermal analysis(TG-DTA)showed that the optimized products were pure-phase rhombic anhydrous magnesium carbonate crystals with good dispersion,verifying the effectiveness of the BP neural network in process optimization.
