Due to the layer-by-layer manufacturing characteristics,metallurgical process of selective laser melting(SLM)is inherently dif-ferent in the building direction because of varying conditions,thereby resulting inter-lay...Due to the layer-by-layer manufacturing characteristics,metallurgical process of selective laser melting(SLM)is inherently dif-ferent in the building direction because of varying conditions,thereby resulting inter-layer heterogeneity.To mitigate such anisotropy,it is of great significance to understand the effects of processing parameters on the property evolution and thus metallurgy of fabrication process.This research proposes one-factor-at-a-time experiment to investigate the influences of laser power and scanning speed on the surface qual-ity,microstructures and mechanical properties of selective laser melted Ti-6Al-4V parts.Surface quality is assessed by roughness around the printings while mechanical properties are evaluated through microhardness and tensile strengths.Phases in microstructure are quantified by XRD to correlate with mechanical properties.Fracture morphology is analyzed to understand the effect of defects and microstructure on mechanical performance.The optimized parameter corresponding to best surface quality and mechanical properties has been found respect-ively in laser power of 190 W and scanning speed of 800 mm/s.After optimization,surface roughness has decreased by 44.47%for upper surface.Yielding strength,tensile strength and elongation rate have improved by 13.17%,43.34%and 64.51%,respectively,with similar hardness and Young’s modulus.In addition,heterogeneity of mechanical properties has great improvement by a range of 31.63%-92.68%.展开更多
多段气化炉反应器主体由下部鼓泡床和上部快速床组成,是一种新型的煤分级转化集成技术。针对三维全循环多段气化炉,采用MP-PIC(mult-phase particle in cell,Barracuda)方法模拟了多粒径煤粉颗粒的循环流化过程,研究了鼓泡床高度对气化...多段气化炉反应器主体由下部鼓泡床和上部快速床组成,是一种新型的煤分级转化集成技术。针对三维全循环多段气化炉,采用MP-PIC(mult-phase particle in cell,Barracuda)方法模拟了多粒径煤粉颗粒的循环流化过程,研究了鼓泡床高度对气化炉内流动特性的影响。研究发现:①在适当范围内,降低鼓泡床高度,床体更快达到稳定操作状态;②快速床上部颗粒浓度随鼓泡床构体高度增加而降低;③鼓泡床高度的增加使得过渡段上部和快速床下部的细颗粒(<1 000μm)含量增加;④靠近快速床出口截面处最小颗粒的含量随鼓泡床高度增大而单调增加。这些规律对多段气化炉的设计和优化具有参考意义。展开更多
采用MP-PIC (multi-phase particle in cell)方法模拟了三维多段气化炉(上部快速床,下部鼓泡床)多粒径煤粉的循环流化过程,研究了分布板不同进气方向对气化炉内颗粒分布的影响。结果表明:分布板开孔与水平方向夹角越大,物料进入快速床...采用MP-PIC (multi-phase particle in cell)方法模拟了三维多段气化炉(上部快速床,下部鼓泡床)多粒径煤粉的循环流化过程,研究了分布板不同进气方向对气化炉内颗粒分布的影响。结果表明:分布板开孔与水平方向夹角越大,物料进入快速床并形成流化状态越快,但对成形后的流化形态影响较小;分布板进气方向对分布板处的轴向颗粒浓度分布影响较大,对快速床内轴向颗粒浓度分布影响较小;随着分布板进气方向与水平夹角的减小,鼓泡床下部颗粒浓度增大,固相颗粒通量增大;分布板进气方向对旋风分离效率影响较小。因此,工程上可根据需要适当减小分布板进气方向与水平方向的夹角来增加分布板上部颗粒浓度分布。展开更多
基金Project was supported by the Natural Science Foundation of Fujian Province(Grant No.2020J01873)Science and Technology Major Project of Fujian Province(Grant No.2020HZ03018)+1 种基金Fujian Provincial Foreign Cooperation Project of Science and Technology(Grant No.2020I1003)Fujian Provincial Special Project for Marine Economy Development(Grant No.2021-517).
文摘Due to the layer-by-layer manufacturing characteristics,metallurgical process of selective laser melting(SLM)is inherently dif-ferent in the building direction because of varying conditions,thereby resulting inter-layer heterogeneity.To mitigate such anisotropy,it is of great significance to understand the effects of processing parameters on the property evolution and thus metallurgy of fabrication process.This research proposes one-factor-at-a-time experiment to investigate the influences of laser power and scanning speed on the surface qual-ity,microstructures and mechanical properties of selective laser melted Ti-6Al-4V parts.Surface quality is assessed by roughness around the printings while mechanical properties are evaluated through microhardness and tensile strengths.Phases in microstructure are quantified by XRD to correlate with mechanical properties.Fracture morphology is analyzed to understand the effect of defects and microstructure on mechanical performance.The optimized parameter corresponding to best surface quality and mechanical properties has been found respect-ively in laser power of 190 W and scanning speed of 800 mm/s.After optimization,surface roughness has decreased by 44.47%for upper surface.Yielding strength,tensile strength and elongation rate have improved by 13.17%,43.34%and 64.51%,respectively,with similar hardness and Young’s modulus.In addition,heterogeneity of mechanical properties has great improvement by a range of 31.63%-92.68%.
文摘多段气化炉反应器主体由下部鼓泡床和上部快速床组成,是一种新型的煤分级转化集成技术。针对三维全循环多段气化炉,采用MP-PIC(mult-phase particle in cell,Barracuda)方法模拟了多粒径煤粉颗粒的循环流化过程,研究了鼓泡床高度对气化炉内流动特性的影响。研究发现:①在适当范围内,降低鼓泡床高度,床体更快达到稳定操作状态;②快速床上部颗粒浓度随鼓泡床构体高度增加而降低;③鼓泡床高度的增加使得过渡段上部和快速床下部的细颗粒(<1 000μm)含量增加;④靠近快速床出口截面处最小颗粒的含量随鼓泡床高度增大而单调增加。这些规律对多段气化炉的设计和优化具有参考意义。
文摘采用MP-PIC (multi-phase particle in cell)方法模拟了三维多段气化炉(上部快速床,下部鼓泡床)多粒径煤粉的循环流化过程,研究了分布板不同进气方向对气化炉内颗粒分布的影响。结果表明:分布板开孔与水平方向夹角越大,物料进入快速床并形成流化状态越快,但对成形后的流化形态影响较小;分布板进气方向对分布板处的轴向颗粒浓度分布影响较大,对快速床内轴向颗粒浓度分布影响较小;随着分布板进气方向与水平夹角的减小,鼓泡床下部颗粒浓度增大,固相颗粒通量增大;分布板进气方向对旋风分离效率影响较小。因此,工程上可根据需要适当减小分布板进气方向与水平方向的夹角来增加分布板上部颗粒浓度分布。
基金Talents Training Program of Pudong Hospital affiliated to Fudan University(PX201705)The Key Discipline Group of Pudong District Health and Family Planning Commission-Tertiary Prevention and Treatment of Cerebrovascular Disease(PWZxq2017-09)
