1 Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China
2 Songshan Lake Materials Laboratory, Dongguan 523830, Guangdong, China
3 Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
4 Jiaxing Research Institute, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China
5 High Performance Computing Department, National Supercomputing Center, Shenzhen 518055, Guangdong, China
Ti-6Al-4V is a benchmark Ti alloy. Laser wire additive manufacturing (LWAM) offers advanced manufacturing capability to the alloy for applications possibly including exploration of outer space. As a typical multiple-variable process, LWAM is complex, which, however, can be analyzed, predicated or even optimized by artificial intelligence (AI) methods such as machine learning (ML). In this study, printing parameters of the Ti-6Al-4V is firstly optimized using single-track-single-layer experiments, and then single-track-multiple-layer samples are printed, whose properties in terms of hardness and compressive strength are analyzed subsequently by both experiments and ML. The two ML approaches, artificial neural network (ANN) and support vector machine (SVM), are employed to predict the experimental results, whose coefficients of determination R2 show good values. Further optimized properties are realized by adopting genetic algorithm (GA) and simulated annealing (SA) approaches, which contribute to high mechanical properties achieved, for instance, an engineering compressive strength of about 1694 MPa. The results here indicate that important mechanical properties of the LWAM-prepared Ti alloys can be well predicted and enhanced using suitable ML approaches.
laser technique laser wire additive manufacturing (LWAM) Ti-6Al-4V machine learning mechanical properties support vector machine (SVM) artificial neural network (ANN)
1 沈阳工业大学机械工程学院, 沈阳 110870
2 辽宁工业大学机械工程与自动化学院, 锦州 121000
3 齐鲁工业大学能源与动力工程学院, 济南 250353
4 中国人民解放军92942部队, 北京 100161
为解决高黏性水泥3D打印堵塞问题, 通过构建3D打印平台开展了物理模拟试验, 采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对硬化产物进行检测, 并利用有限元软件Polyflow分析打印喷头内部流场, 最后结合试验和数值仿真结果确认堵塞问题原因。结果表明: 高黏性水泥的凝结时间在10~23 min, 与普通硅酸盐水泥相比, 其会更快地硬化形成棱形晶体; 打印喷头内部的压力梯度在挤出口变径处达到峰值113.9 kPa, 并且螺槽内的浆料以塞流形式输运; 在3D打印过程中, 部分浆料黏附在螺杆表面, 并快速硬化形成的产物嵌入到螺杆微观凹凸表面中, 而未黏附的浆料在筒内高压差作用下以塞流形式输送, 在筒内变径处发生液相迁移, 最终导致打印堵塞。研究结果可为高黏性水泥3D打印喷头设计提供理论支撑。
高黏性水泥 堵塞 塞流 压力梯度 液相迁移 high viscosity cement blockage plug flow pressure gradient liquid phase migration Polyflow Polyflow
1 国网四川省电力公司电力科学研究院，四川 成都 610041
2 华东师范大学重庆研究院，重庆 401121
3 国网电力科学研究院武汉南瑞有限责任公司，湖北 武汉 430074
双光梳光谱是实现高分辨光谱分析的重要工具，其因相干特性依赖于复杂、庞大的频率锁定与反馈系统，导致成本高昂且对环境扰动敏感，应用领域受限。基于电光频率梳的双光梳系统具有装置简单、频率捷变及相干性高等优势，有利于外场的应用，但其在气体检测应用中的含量反演精度及实时性仍有待验证。为此，搭建了高相干电光双光梳系统，并利用多通气体池实现了CO和CO2气体吸收光谱测量，其结果与HITRAN数据库仿真结果一致。光谱分辨率达200 MHz，单次刷新时间仅为4 μs。实验通过对CO2吸收峰的含量反演与多峰拟合，将含量不确定度缩小至2.86%。此外，通过对CO吸收光谱的快速检测，验证了系统对混合气体含量监测的实时性，该系统有望应用于电力设备故障特征气体的实时监测。
分子光谱 电光 频率梳 双光梳光谱 气体检测 激光与光电子学进展
2023, 60(17): 1730002
1 华东师范大学精密光谱科学与技术国家重点实验室，上海 200062
2 华东师范大学重庆研究院精密光学重庆市重点实验室，重庆 401120
3 上海朗研光电科技有限公司，上海 201108
4 中国空间技术研究院西安分院空间微波技术国家级重点实验室，陕西 西安 710100
检测灵敏度是衡量一项检测技术的重要参数。为了提高激光诱导击穿光谱技术（LIBS）的检测灵敏度，搭建了三光丝耦合诱导击穿光谱（TIBS）系统，对土壤中的微量铬元素进行检测，并将检测结果与等离子体光栅诱导击穿光谱（GIBS）系统、光丝诱导击穿光谱（FIBS）系统进行对比。TIBS系统的谱线信号强度比GIBS系统增强了2倍，比FIBS系统增强了7~11倍。研究了FIBS、GIBS、TIBS系统的谱线强度随样品位置的变化，发现TIBS系统的激发稳定性与GIBS系统相近。此外，在对土壤中重金属铬的定量研究中，发现FIBS、GIBS、TIBS系统对土壤中铬元素的检出限分别为22.18×10-6、8.68×10-6、5.06×10-6。TIBS系统相较于GIBS系统能进一步提高检测灵敏度。
光谱学 激光诱导击穿 等离子体光栅 超快飞秒脉冲 重金属 检出限
1 华东师范大学, 精密光谱科学与技术国家重点实验室, 上海 200062
2 华东师范大学重庆研究院, 精密光学重庆市重点实验室, 重庆 401121
随着电力系统向高压、 大容量、 信息技术应用等方向发展, 电力设备的高效运维对于保障电力系统安全运行和经济平稳增长具有重大意义。 对六氟化硫气体分解产物的检测是电气绝缘设备检漏及判断故障类型的有效手段。 基于光学频率梳的双光梳光谱检测技术具有高分辨、 高精度、 宽光谱、 高速动态等优势, 有望在电力设备漏气故障检修中, 为判断特征气体种类及定量分析提供可靠手段。 搭建了基于两台集成掺铒光纤光梳的双光梳光谱检测装置。 通过精密频率控制及精细温控, 光梳重复频率抖动从18.37 Hz降低至607.72 μHz, 光梳梳齿稳定度控制在10-12。 装置具有长时间稳定和小型化集成的特点, 对外界环境干扰免疫性强, 在室外环境运行两小时, 光梳的重复频率及载波包络相位信号仍能保持相位锁定, 两台光梳相干性无明显劣化。 在光谱检测方面, 结合使用超灵敏多通气室, 对CO与CO2混气进行了测量, 在ms量级时间内实现了1 540～1 590 nm波段内CO和CO2吸收峰的同时成谱检测, 光谱分辨率达1 pm。 分别以CO和CO2在1 585.47、 1 581.946 nm和1 580.5、 1 579.575 nm的特征吸收峰为例, 通过洛伦兹数据拟合反演出相应分子数密度。 CO和CO2的气体分子数密度的多峰测量不确定度分别为0.32%与0.24%, 较单峰测量结果(2%)降低了近1个量级。 该研究推进了双光梳光谱技术及系统在电力设备漏气故障特征气体非接触实时检测中的应用。 传统接触式检测存在检测气体种类单一、 积分时间长、 难以做到长期在线实时监测的缺点, 而双光梳光谱检测能够在ms量级对多组分气体的多峰非接触式同时成谱检测, 在缩短检测时间的同时提高了检测精度, 为电力设备漏气故障的及时排查及故障类型的诊断提供了有效途径。
光学频率梳 双光梳光谱 特征气体检测 Optical frequency comb Dual-comb spectroscopy Characteristic gas detection
1 华东师范大学精密光谱科学与技术国家重点实验室，上海 200062
2 中国计量大学光学与电子科技学院，浙江 杭州 310018
3 南开大学现代光学研究所，天津 300071
探索了一种基于两束相向传播飞秒光丝诱导荧光的光谱检测方法。实验结果表明，该方法能够延长荧光衰减时间，增强物质特征谱线强度。将该方法应用于盐水溶液中金属离子（K+、Na+、Mg2+）特征峰及含量的检测，其对Na+含量的检测灵敏度为4.3×10-6，较相同激发脉冲能量下的单丝诱导荧光检测技术提升了4倍，且具有良好的线性度。该方法有望为污染物检测提供新途径。
光谱学 光丝 荧光光谱 飞秒激光
高帧频CMOS图像传感器具有集成度高、帧频高、功耗低、抗干扰抗辐照能力强等特性，在科学实验中应用广泛。为提高外同步触发瞬态成像模式下的成像性能，首先介绍了基于高帧频CIS(5T像素，超大快门)的瞬态成像系统构成及其工作模式；从像素结构出发，对该款CIS在不同工作模式下的成像性能进行了理论分析；搭建了基于EMVA1288的标准化测试平台，对瞬态工作模式下的多项关键性能指标进行了测试，并与稳态工作模式下的性能进行了对比。分析结果表明：与稳态工作模式相比，瞬态成像模式下图像传感器具有更大的暗本底和固定模式噪声，但传感器的时序噪声、光响应非均匀性优于稳态工作模式，具有更高的信噪比和动态范围，与理论分析基本吻合。测试分析结果可用于指导科学成像系统设计与性能优化。
高帧频CMOS图像传感器 瞬态成像 性能分析 响应非均匀性 high-speed CMOS image sensor transient imaging performance analysis PRNU 红外与激光工程
2022, 51(8): 20210694
Author Affiliations
Abstract
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 AlSi10Mg, 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.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 AlSi10Mg, 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.
additive manufacturing laser powder bed fusion selective laser melting porosity defects mechanical performance metallic materials perspectives Opto-Electronic Advances
2022, 5(10): 210058
1 华东师范大学精密光谱科学与技术国家重点实验室，上海 200062
2 中国空间技术研究院西安分院空间微波技术国家级重点实验室，陕西 西安 710100
3 华东师范大学重庆研究院，重庆 401147
利用双光梳飞行时间法对小口径太赫兹天线及反射器面形进行了三维测量。实验中，单像素点测量时间为8 μs，纵向测量误差为1.3 μm。相较于传统的激光干涉法，双光梳法兼具了模糊距离大、测量精度高以及数据更新快等优势，为微波/太赫兹器件的面形测量提供了新途径。
测量 太赫兹 干涉 相干 成像系统 中国激光
2022, 49(17): 1704001
