To accurately analyze the impact of casting pores in steel,high-resolution 3D X-ray tomography technology was used to gather detailed statistical information about micropores.These micropores were classified as gas,sh...To accurately analyze the impact of casting pores in steel,high-resolution 3D X-ray tomography technology was used to gather detailed statistical information about micropores.These micropores were classified as gas,shrinkage,and gas-shrinkage pores depending on their formation origin and morphology.Clustering tendencies and affinity parameters were defined to characterize the spatial correlations among these three types of pores.The 3D data from X-ray tomography scans were then integrated into finite element analysis(FEA)software to predict how micropore shape,size,and distribution influence stress distribution within the material.The results show that certain inflection points with small local radii within the cast pores are major contributors to stress concentration.Therefore,cast pores cannot be simply modeled as ideal spherical pores.The sphericity and volume of pores have a significant impact on the stress concentration of the model.Specifically,lower sphericity and larger pore volumes result in higher stress concentrations.Moreover,the internal pores of steel castings exhibit specific global distribution characteristics.Pores located on the surface of the specimen lead to significantly higher stress concentrations compared to those located inside the specimen.展开更多
An integrated simulation of powder effects on particle temperature and microstructural evolution in laser directed energy deposition additive manufacturing process was carried out.The spatial distribution of the flyin...An integrated simulation of powder effects on particle temperature and microstructural evolution in laser directed energy deposition additive manufacturing process was carried out.The spatial distribution of the flying powder particles was simulated by the discrete element method to calculate the energy for the flying powder particles under the laser−particle interaction with electromagnetic wave analysis.Combined with the phase field method,the influence of particle size on the microstructural evolution was studied.The microstructural evolution is validated through comparison with experimental observation.Results indicate that the narrow particle size distribution is beneficial to obtaining a more uniform temperature distribution on the deposited layers and forming smaller equiaxed grains near the side surfaces of the sample.Appropriate powder particle size is beneficial to the conversion of the electromagnetic energy into heat.Particles with small size are recommended to form equiaxed grains and to improve product quality.Appropriate powder flow rate improves the laser energy efficiency,and higher powder flow rate leads to more uniform equiaxed grains on both sides of the cross-section.展开更多
Pure commercial titanium was welded with two types of stainless steel,namely SUS 304 austenitic stainless steel and SUS 821L1 duplex stainless steel.The wavy interface of SUS 821L1 was smaller than that of SUS 304.The...Pure commercial titanium was welded with two types of stainless steel,namely SUS 304 austenitic stainless steel and SUS 821L1 duplex stainless steel.The wavy interface of SUS 821L1 was smaller than that of SUS 304.The vortex zone was observed from both longitudinal and transverse directions,and its composition was analyzed.The interface of Ti/SUS 821L11 was able to bear 401−431 MPa shear load while that of Ti/SUS 304 could withstand 352−387 MPa.The weldability window was used to analyze experimental phenomenon.Furthermore,the smoothed particle hydrodynamics(SPH)numerical simulation method was used to simulate the wavy interface.The trend of wavelength and amplitude change with strength and the stand-offs was consistent with the experimental results.展开更多
基金The National Natural Science Foundation of China(No.51578137).
文摘To accurately analyze the impact of casting pores in steel,high-resolution 3D X-ray tomography technology was used to gather detailed statistical information about micropores.These micropores were classified as gas,shrinkage,and gas-shrinkage pores depending on their formation origin and morphology.Clustering tendencies and affinity parameters were defined to characterize the spatial correlations among these three types of pores.The 3D data from X-ray tomography scans were then integrated into finite element analysis(FEA)software to predict how micropore shape,size,and distribution influence stress distribution within the material.The results show that certain inflection points with small local radii within the cast pores are major contributors to stress concentration.Therefore,cast pores cannot be simply modeled as ideal spherical pores.The sphericity and volume of pores have a significant impact on the stress concentration of the model.Specifically,lower sphericity and larger pore volumes result in higher stress concentrations.Moreover,the internal pores of steel castings exhibit specific global distribution characteristics.Pores located on the surface of the specimen lead to significantly higher stress concentrations compared to those located inside the specimen.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.11572074)the Liaoning Provincial Natural Science Foundation,China(No.2019-KF-05-07)。
文摘An integrated simulation of powder effects on particle temperature and microstructural evolution in laser directed energy deposition additive manufacturing process was carried out.The spatial distribution of the flying powder particles was simulated by the discrete element method to calculate the energy for the flying powder particles under the laser−particle interaction with electromagnetic wave analysis.Combined with the phase field method,the influence of particle size on the microstructural evolution was studied.The microstructural evolution is validated through comparison with experimental observation.Results indicate that the narrow particle size distribution is beneficial to obtaining a more uniform temperature distribution on the deposited layers and forming smaller equiaxed grains near the side surfaces of the sample.Appropriate powder particle size is beneficial to the conversion of the electromagnetic energy into heat.Particles with small size are recommended to form equiaxed grains and to improve product quality.Appropriate powder flow rate improves the laser energy efficiency,and higher powder flow rate leads to more uniform equiaxed grains on both sides of the cross-section.
文摘Pure commercial titanium was welded with two types of stainless steel,namely SUS 304 austenitic stainless steel and SUS 821L1 duplex stainless steel.The wavy interface of SUS 821L1 was smaller than that of SUS 304.The vortex zone was observed from both longitudinal and transverse directions,and its composition was analyzed.The interface of Ti/SUS 821L11 was able to bear 401−431 MPa shear load while that of Ti/SUS 304 could withstand 352−387 MPa.The weldability window was used to analyze experimental phenomenon.Furthermore,the smoothed particle hydrodynamics(SPH)numerical simulation method was used to simulate the wavy interface.The trend of wavelength and amplitude change with strength and the stand-offs was consistent with the experimental results.
