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Framework and development of data-driven physics based model with application in dimensional accuracy prediction in pocket milling

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Chinese Journal of Aeronautics 2021年第6期34卷 162-177页

作者： Zhanying CHEN Liping WANG Jiabo ZHANG Guoqiang GUO Shuailei FU Chao WANG Xuekun LI Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China State Key Lab of Tribology Tsinghua UniversityBeijing 100084China Beijing Spacecrafts China Academy of Space TechnologyBeijing 100094China Shanghai Spaceflight Precision Machinery Institute Shanghai 201600China

In the manufacturing of thin wall components for aerospace industry,apart from the side wall contour error,the Remaining Bottom Thickness Error(RBTE)for the thin-wall pocket component(e.***.rocket shell)is of the same importance but overlooked in current research.If the RBTE reduces by 30%,the weight reduction of the entire component will reach up to tens of kilograms while improving the dynamic balance performance of the large component.Current RBTE control requires the off-process measurement of limited discrete points on the component bottom to provide the reference value for compensation.This leads to incompleteness in the remaining bottom thickness control and redundant measurement in manufacturing.In this paper,the framework of data-driven physics based model is proposed and developed for the real-time prediction of critical quality for large components,which enables accurate prediction and compensation of RBTE value for the thin wall components.The physics based model considers the primary root cause,in terms of tool deflection and clamping stiffness induced Axial Material Removal Thickness(AMRT)variation,for the RBTE formation.And to incorporate the dynamic and inherent coupling of the complicated manufacturing system,the multi-feature fusion and machine learning algorithm,i.***.kernel Principal Component Analysis(kPCA)and kernel Support Vector Regression(kSVR),are incorporated with the physics based model.Therefore,the proposed data-driven physics based model combines both process mechanism and the system disturbance to achieve better prediction accuracy.The final verification experiment is implemented to validate the effectiveness of the proposed method for dimensional accuracy prediction in pocket milling,and the prediction accuracy of AMRT achieves 0.014 mm and 0.019 mm for straight and corner milling,respectively.

关键词： Data-driven physics based model Thin-wall component Pocket milling Remaining bottom thickness error

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Nearshore regional behavior of lightning interaction with wind turbines

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Journal of Ocean Engineering and Science 2016年第1期1卷 66-76页

作者： Gilbert A.Malinga John M.Niedzwecki Zachary Department of Civil Engineering Texas A&M UniversityCollege StationTXUSA

The severity of lightning strikes on offshore wind turbines built along coastal and nearshore regions can pose safety concerns that are often overlooked.In this research study the behavior of electrical discharges for wind turbines that might be located in the nearshore regions along the East Coast of China and Sea of Japan were characterized using a physics-based model that accounted for a total of eleven different geometrical and lightning parameters.Utilizing the electrical potential field predicted using this model it was then possible to estimate the frequency of lightning strikes and the distribution of electrical loads utilizing established semi-empirical relationships and available data.The total number of annual lightning strikes on an offshore wind turbine was found to vary with hub elevation,extent of cloud cover,season and geographical location.The annual lightning strike rate on a wind turbine along the nearshore region on the Sea of Japan during the winter season was shown to be moderately larger compared to the lightning strike frequency on a turbine structure on the East Coast of China.Short duration electrical discharges,represented using marginal probability functions,were found to vary with season and geographical location,exhibiting trends consistent with the distribution of the electrical peak current.It was demonstrated that electrical discharges of moderately long duration typically occur in the winter months on the East Coast of China and the summer season along the Sea of Japan.In contrast,severe electrical discharges are typical of summer thunderstorms on the East Coast of China and winter frontal storm systems along the West Coast of Japan.The electrical charge and specific energy dissipated during lightning discharges on an offshore wind turbine was found to vary stochastically,with severe electrical discharges corresponding to large electrical currents of long duration.

关键词： Nearshore wind turbines physics based model Lightning strikes Electrical current Strike frequency Electrical charge.

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