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Process Window Expansion of Laser Chemical Machining by Using High Pressure

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Materials Sciences and Applications 2020年第5期11卷 296-304页

作者： Marcel Simons Tim Radel frank vollertsen BIAS-Bremer Institut für Angewandte Strahltechnik Bremen Germany Faculty of Production Engineering-Mechanical Engineering & Process Engineering University of Bremen Bremen Germany

Laser Chemical Machining (LCM) is a non-conventional removal process, based on a precise thermal activation of heterogeneous chemical reactions between an electrolyte and a metallic surface. Due to local overheating during the process, boiling bubbles occur, which can impair the removal quality. In order to reduce the amount of bubbles, the laser chemical process is performed at different process pressures. Removal experiments were performed on Titanium Grade 1 using the electrolyte phosphoric acid at various process pressures, machining speeds and laser powers in order to determine the limit of the process window by evaluating the characteristics of the removal cavities. As a result, the process window for non-disturbed laser chemical machining is widened at higher process pressures. The process pressures have no influence on the geometric shape of the removal. The expansion of the process window is attributed to the fact that at higher process pressures the saturation temperature of the electrolyte rises, so that bubble boiling starts at a higher surface temperature on the workpiece induced by the laser power. The removal rate could be increased by a factor of 2.48 by increasing the process pressures from ambient pressure to 6 bar, thus taking an important step towards the economic efficiency of the laser chemical machining.

关键词： Micro Machining Laser Micro Machining Laser Chemical Removal Removal Rate Process Pressure

Thermal Analysis of Laser Chemical Machining: Part I: Static Irradiation

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Materials Sciences and Applications 2017年第10期8卷 685-707页

作者： Hamza Messaoudi Sandro Eckert frank vollertsen BIAS—Bremer Institut für angewandte Strahltechnik Bremen Germany Faculty of Production Engineering-Mechanical Engineering & Process Engineering University of Bremen Bremen Germany

The laser chemical machining is a non-conventional substractive processing method. It is based on the laser-activation of a material dissolution of metals in electrolyte ambient via local-induced temperature gradients and allows a gentle and smooth processing of especially temperature-sensitive metals. However, the material removal is characterized by a narrow process window and is restricted by occurring disturbances, which are supposed to be related to the localized electrolyte boiling. In order to control the removal quality and avoid disturbances, the correlation between the laser-induced temperatures and the resulting removal geometry has to be better understood. In this work an analytical modeling of the laser-induced temperatures at the surface of titanium based on a Green-function approach is presented. The main influencing factors (laser, electrolyte, material) as well as possible heat transfer into the electrolyte are included and discussed. To verify the calculated temperatures, single spot experiments are performed and characterized for titanium in phosphoric acid solution within laser irradiation of 1 s. The correlation between the temperature distribution and the resulting removal geometry is investigated based on a spatial superposition. Thereby, the bottom limit temperature is found to range between 63°C and 70°C whereas the upper limit is related to the nucleate boiling regime. Based on the performed correlation an indicator is identified to predict the ruling removal regime and thereby to reduce the experimental expenditure.

关键词： Laser Micro Machining Laser Chemical Removal Modeling Temperature Process Stability Titanium

磁控溅射Al-Zr薄膜在微拉深成形中的拉深性能(英文)

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中国有色金属学会会刊：英文版 2012年第S2期22卷 268-274页

作者： Gerrit BEHRENS Julien KOVAC Bernd KHLER frank vollertsen Heinz-Rolf STOCK BIAS-Bremer Institut für Angewandte Strahltechnik GmbH Klagenfurter Str. 2 D-28359 Bremen Germany IWT-Stiftung Institut für Werkstofftechnik Badgasteiner Str. 3 D-28359 Bremen Germany

拉深成形可以用来制备形状复杂的零部件,甚至可达微加工水平。采用磁控溅射方法,在基底温度分别为310K和433K下,制备了厚度约为15μm的两种不同的AlZr薄膜。将这两种薄膜做为坯料,采用冲头直径为0.75mm的微拉深设备研究其拉深性能。虽... 详细信息

拉深成形可以用来制备形状复杂的零部件,甚至可达微加工水平。采用磁控溅射方法,在基底温度分别为310K和433K下,制备了厚度约为15μm的两种不同的AlZr薄膜。将这两种薄膜做为坯料,采用冲头直径为0.75mm的微拉深设备研究其拉深性能。虽然这两种材料在拉伸试验中显示出较小的最大应变,但还是成功地实现了微拉深成形。在基底温度为310K和433K制备的两种材料的极限拉深比分别为1.8和1.7。这些结果比先前采用AlSc合金的结果要好,与采用传统轧制方法所得纯铝薄膜的拉深结果相似。结果表明,采用磁控溅射方法制备的薄膜可以用来进行微拉深成形。

关键词： Al-Zr薄膜微拉深成形成形极限磁控溅射

Influence of Laser-Induced Bubble Formation on Laser Chemical Machining

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Journal of Surface Engineered Materials and Advanced Technology 2020年第2期10卷 21-33页

作者： Marcel Simons Tim Radel Raj Shanta Kajsaravally frank vollertsen BIAS-Bremer Institut für angewandte Strahltechnik Bremen Germany Department of Communications Engineering Bremen Germany Faculty of Production Engineering-Mechanical Engineering & Process Engineering University of Bremen Bremen Germany

Laser Chemical Machining (LCM) is a non-conventional processing method, which enables very accurate and precise ablation of metallic surfaces. Material ablation results from laser-induced thermal activation of heterogeneous chemical reactions between electrolytes and a metallic surface. However, when processing metallic surfaces with LCM, large fluctuations in ablation quality can occur due to rising bubbles. The for-mation of bubbles during laser chemical machining and their influence on the ablation quality has not been investigated. For a more detailed investigation of the bubbles, ablation experiments on Titanium and Ce-ramic under different thermal process conditions were performed. The experiments were recorded by a high-speed camera. The evaluation of the video sequences was performed using Matlab. The resulting bubbles were analyzed regarding their size and frequency. The results show that boil-ing bubbles formed on both materials during processing. Titanium also produces smaller bubbles, which can be identified as process bubbles ac-cording to their size. Furthermore, it was found that undisturbed laser chemical ablation can be achieved in the presence of a boiling process, since both boiling bubbles and process bubbles were detected during machining within the process window.

关键词： Micro Machining Laser Micro Machining Laser Chemical Removal Nucleate Boiling Highspeed Videography

Solving traffic data occlusion problems in computer vision algorithms using DeepSORT and quantum computing

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第1期11卷 1-15页

作者： frank Ngeni Judith Mwakalonge Saidi Siuhi Department of Engineering South Carolina State UniversityOrangeburgSC 29117USA

Inaccuracies of traffic sensors during traffic counting and vehicle classification have persisted as transportation agencies have been prompted to calibrate sensors *** of multiple objects,heavy occlusions,and similar appearances in congested places are some causes of computer vision model *** paper used the YOLOv5 model for detection and the DeepSORT model for tracking *** to the nature of the reported problem caused by many misses and mismatches,the power of quantum computing with the alternating direction method of multipliers(ADMM)optimizer was leveraged.A basic Kalman filter and the Hungarian algorithm features were used in combination with a quantum optimizer to present robust multiple object tracking(MOT)*** hybrid combination of the classical and quantum model has fastened learning the occludes during frame matching of tracks and detections by generating minimum quantum cost function *** with the existing models indicated a significant increase in the primary MOT metric multiple object tracking accuracy(MOTA)by 16%more than the regular YOLOv5-DeepSORT model when using a quantum ***,a 6%multiple object tracking precision(MOTP)increases and a 6%identification metrics(F_(1))score increase were observed using the quantum optimizer with identity switching reduced from 6 to *** model is expected to assist transportation officials in improving the accuracy of traffic counts and vehicle classification and reduce the need for regular computer vision software calibration.

关键词： Traffic classification Traffic counting DeepSORT YOLOv5 Quantum computing

Guaranteed Cost Attitude Tracking Control for Uncertain Quadrotor Unmanned Aerial Vehicle Under Safety Constraints

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IEEE/CAA Journal of Automatica Sinica 2024年第6期11卷 1447-1457页

作者： Qian Ma Peng Jin frank L.Lewis School of Automation Nanjing University of Science and TechnologyNanjing 210094China UTA Research Institute University of Texas at ArlingtonFort WorthTexas 76118 USA IEEE

In this paper,guaranteed cost attitude tracking con-trol for uncertain quadrotor unmanned aerial vehicle(QUAV)under safety constraints is ***,an augmented system is constructed by the tracking error system and reference *** transformation aims to convert the tracking control prob-lem into a stabilization control ***,control barrier function and disturbance attenuation function are designed to characterize the violations of safety constraints and tolerance of uncertain disturbances,and they are incorporated into the reward function as penalty *** on the modified reward function,the problem is simplified as the optimal regulation problem of the nominal augmented system,and a new Hamilton-Jacobi-Bellman equation is ***,critic-only rein-forcement learning algorithm with a concurrent learning tech-nique is employed to solve the Hamilton-Jacobi-Bellman equa-tion and obtain the optimal *** proposed algorithm can not only ensure the reward function within an upper bound in the presence of uncertain disturbances,but also enforce safety *** performance of the algorithm is evaluated by the numerical simulation.

关键词： Attitude tracking control quadrotor unmanned aerial vehicle(QUAV) reinforcement learning safety constraints uncertain disturbances.

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金属板材激光弯曲成形规律的研究

中国激光 1998年第9期25卷 859-864页

作者：李纬民 Manfred Geiger frank vollertsen 燕山大学机械工程学院锻压所德国Erlangen-Nuerberg大学

用大变形弹塑性有限元法对金属板材柔性成形新工艺——激光弯曲进行了动态数值模拟。论证了板料的几何参数和工艺参数与变形的相互关系。模拟结果与试验吻合较好。

关键词：激光弯曲柔性成形数值模拟金属板材激光加工

Seed-assisted growth for high-performance perovskite solar cells:A review

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Journal of Energy Chemistry 2024年第9期96卷 588-610页

作者： Zhimin Fang Ting Nie Jianning Ding Shengzhong(frank)Liu Institute of Technology for Carbon Neutralization Yangzhou UniversityYangzhou 225127JiangsuChina Dalian National Laboratory for Clean Energy iChEMDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina Key Laboratory of Applied Surface and Colloid Chemistry Ministry of EducationShaanxi Key Laboratory for Advanced Energy DevicesShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi’an 710119ShaanxiChina

The rapid increase in the power conversion efficiency(PCE)of perovskite solar cells(PSCs)is closely related to the development of deposition techinique for perovskite *** high-quality perovskite film enables efficient charge transportation and less trap states,which are eventually translated into enhanced device ***-assisted growth(SAG)is a potential technique for depositing highly-crystallized perovskite films with preferential crystal orientation among the numerous approaches related to crystallization *** this review,we summarize the recent advances in the SAG technique for both one-step and two-step processed perovskite ***,seeding at the buried interface and on the top surface are also *** present different seeds and their corresponding seeding mechanism in detail,such as inorganic nanomaterials,organic ammoniums,alkali metal halides,and perovskite ***,challenges and perspectives are proposed to investigate the potential expansion of seeding engineering in high-performance PSCs,particularly large-area devices.

关键词： Perovskite solar cell Seed Crystallization Efficiency

Monitoring and evaluation of the water quality of the Lower Neches River, Texas, USA

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Water Science and Engineering 2024年第1期17卷 21-32页

作者： Qin Qian Mengjie He frank Sun Xinyu Liu Department of Civil and Environmental Engineering Lamar UniversityBeaumontTX 77710USA Department of Industry Engineering Lamar UniversityBeaumontTX 77710USA Department of Computer Science Lamar UniversityBeaumontTX 77710USA

Increasing bacteria levels in the Lower Neches River caused by Hurricane Harvey has been of a serious *** study is to analyze the historical water sampling measurements and real-time water quality data collected with wireless sensors to monitor and evaluate water quality under different hydrological and hydraulic *** statistical and Pearson correlation analysis on historical water samples determines that alkalinity,chloride,hardness,conductivity,and pH are highly correlated,and they decrease with increasing flow rate due to *** flow rate has positive correlations with Escherichia coli,total suspended solids,and turbidity,which demonstrates that runoff is one of the causes of the elevated bacteria and sediment loadings in the *** correlation between *** and turbidity indicates that turbidity greater than 45 nephelometric turbidity units in the Neches River can serve as a proxy for *** to indicate the bacterial outbreak.A series of statistical tools and an innovative two-layer data smoothing filter are developed to detect outliers,fill missing values,and filter spikes of the sensor *** correlation analysis on the sensor data illustrates that the elevated sediment/bacteria/algae in the river is either caused by the first flush rain and heavy rain events in December to March or practices of land use and land ***,utilizing sensor measurements along with rainfall and discharge data is recommended to monitor and evaluate water quality,then in turn to provide early alerts on water resources management decisions.

关键词： Water quality Pearson correlation analysis Lower Neches River YSI wireless sensors Non-point pollution