Overview of finite elements simulation of temperature profile to estimate properties of materials 3D-printed by laser powder-bed fusion

Laser powder bed fusion(LPBF),like many other additive manufacturing techniques,offers flexibility in design expected to become a disruption to the manufacturing industry.The current cost of LPBF process does not favor a try-anderror way of research,which makes modelling and simulation a field of superior importance in that area of engineering.In this work,various methods used to overcome challenges in modeling at different levels of approximation of LPBF process are reviewed.Recent efforts made towards a reliable and computationally effective model to simulate LPBF process using finite element(FE)codes are presented.A combination of ray-tracing technique,the solution of the radiation transfer equation and absorption measurements has been used to establish an analytical equation,which gives a more accurate approximation of laser energy deposition in powder-substrate configuration.When this new analytical energy deposition model is used in in FE simulation,with other physics carefully set,it enables us to get reliable cooling curves and melt track morphology that agree well with experimental observations.The use of more computationally effective approximation,without explicit topological changes,allows to simulate wider geometries and longer scanning time leading to many applications in real engineering world.Different applications are herein presented including:prediction of printing quality through the simulated overlapping of consecutive melt tracks,simulation of LPBF of a mixture of materials and estimation of martensite inclusion in printed steel.     

241Am-Be中子参考辐射的蒙特卡罗模拟研究

研究用于校准场所中子剂量监测仪表的241Am-Be中子参考辐射场计量特性。采用蒙特卡罗方法模拟了空气自由中子参考辐射(FRNR),GB/T 14055规定的最小尺寸中子参考辐射(SRNR)和实际中子参考辐射(ARNR)中不同检验点处中子周围剂量当量率、散射中子占比和能谱分布特征。研究结果表明,空气对FRNR中的剂量率和能谱分布影响小,近似为理想中子参考辐射;采用5%含硼聚乙烯作屏蔽的最小尺寸SRNR可减少热中子,降低散射中子占比,影锥法不适用于小尺寸中子参考辐射中对散射中子的修正;ARNR中的散射中子更少、占比更低,影锥法所得散射中子占比与理论值基本一致。     

微型通风橱

简单介绍设计的微型通风橱在处理有毒气体上的应用，使有毒气体参与或产生的反应更环保。     

基于五氧化二钽集成非线性光波导的高重复频率 宽带平坦相干光频率梳的产生

通过波导结构设计以及色散调控,基于孤子脉冲压缩、自相位调制和光波分裂效应,用0.22 m反常色散五氧化二钽波导级联0.9 m正常色散五氧化二钽波导产生在1 520～1 580 nm波段具有4 dB平坦度、60 nm带宽的平坦光频率梳.利用X-Frog技术分析了脉冲在传输过程中的时谱演化,并且研究了产生光频率梳的相干性.时谱演化指出自相位调制和光波分裂的共同作用使得光频率梳的光谱包络变宽,并且具有良好的平坦度.一阶复互相干度计算指出光频率梳具有较好的相干性.仿真结果表明,五氧化二钽集成非线性光波导在产生高重复频率平坦相干宽带光频率梳方面具有较好的前景.     

硬脂酸/异氰酸酯摩尔比对聚丙烯/木粉复合材料性能的影响

用甲苯-2,4-二异氰酸酯(TDI)和硬脂酸(SA)复合改性木粉,在双螺杆挤出机中制备了聚丙烯(PP)基的木塑复合材料(wPC),研究了SA/TDI摩尔比对木粉表面性能、复合材料力学性能和加工性能的影响.结果表明,随着SA/TDI摩尔比的增大,改性木粉的表面张力逐渐减小,与PP的界面张力先减小后增大;与未改性的WPC相比,SA/TDI复合改性剂对WPC的拉伸强度、弯曲强度、缺口冲击强度影响不明显,但对无缺口冲击强度提升较大;当SA/TDI摩尔比为1.07时,复合材料的无缺口冲击强度和熔体质量流动速率分别达到9.74 kJ/m2和13.12 g/10 min,分别比未改性WPC提高了77％和22％.     

一种测试小分子迁移的新方法

针对高聚物材料中小分子的迁移现象,结合数字图像处理技术,提出了一种基于钠光和斐索等厚原理的光学干涉法.介绍了系统测试原理,针对光学系统的设计作了详细的分析与计算;通过实验测试,设计的光学系统能够采集到清晰的干涉条纹,且满足测试精度要求,由条纹间距随时间的变化测出了丙酮和乙醇小分子迁移时高聚物折射率的变化规律为:丙酮小分...     

邻溴苯基—2—恶唑啉的合成研究

改进了邻溴苯基－２－恶唑的合成方法，使得Ｎ－（β羟乙基）－２－溴苯甲酰胺在氯化亚砚作用了缩合成恶唑啉的收率从４０％左右提高到８４％，并避免了使用ＮａＨ试剂，为芳基－２－恶唑啉的合成提供一条方便，经济的路线。