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Surface Integrity of Inconel 738LC Parts Manufactured by Selective Laser Melting Followed by High-speed Milling

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Chinese journal of Mechanical Engineering 2023年第1期36卷 65-79页

作者： Guanhui Ren Sai Guo bi Zhang Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen518055China Shenzhen Key Laboratory for Additive Manufacturing of High-performance Materials Shenzhen518055China Research and Development Department Shenzhen Xinjinquan Precision Techonology Co.Ltd.Shenzhen518055China School of Mechanical Engineering Shandong UniversityJinan250061China

This study is concerned with the surface integrity of Inconel 738LC parts manufactured by selective laser melting(SLM)followed by high-speed milling(HSM).In the investigation process of surface integrity,the study employs ultradepth three-dimensional microscopy,laser scanning confocal microscopy,scanning electron microscopy,electron backscatter diffractometry,and energy dispersive spectroscopy to characterize the evolution of material microstructure,work hardening,residual stress coupling,and anisotropic effect of the building direction on surface integrity of the *** results show that SLM/HSM hybrid manufacturing can be an effective method to obtain better surface quality with a thinner machining metamorphic ***-speed machining is adopted to reduce cutting force and suppress machining heat,which is an effective way to produce better surface mechanical properties during the SLM/HSM hybrid manufacturing *** general,high-speed milling of the SLM-built Inconel 738LC samples offers better surface integrity,compared to simplex additive manufacturing or casting.

关键词： Surface integrity Inconel 738LC Selective laser melting High-speed milling

Thermal fatigue behavior of 441 ferritic stainless steel in air and synthetic automotive exhaust gas

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Science China(Technological Sciences) 2022年第1期65卷 169-178页

作者： ZHAN jianMing bi HongYun LI MouCheng Materials Genome Institute Shanghai UniversityShanghai 200072China Research Institute Baoshan Iron&Steel Co.Ltd.Shanghai 200431China Institute of Materials School of Materials Science and EngineeringShanghai UniversityShanghai 200072China

The thermal fatigue behavior of 441 ferritic stainless steel was investigated in air and synthetic automotive exhaust gas by the cyclic tests under 100℃-800℃ and 900℃ *** the fracture failure,the microstructure,oxide film,and precipitated phases were analyzed using optical microscopy,X-ray diffraction,scanning electron microscopy,and transmission electron *** both atmospheres,increasing the maximum temperature from 800℃ to 900℃ results in lower strength and fatigue life and higher elongation and grain *** the same maximum temperature,the thermal fatigue life of the specimen is lower in the synthetic exhaust gas than in the *** the higher maximum temperature and the synthetic exhaust gas facilitate fatigue *** failure mechanism is discussed according to the grain size,thermal stress,high-temperature oxidation rate,and the precipitation of secondary *** precipitated carbides play an important role in the rapid fatigue failure of specimens in the synthetic exhaust gas.

关键词： stainless steel automobile exhaust gas thermal fatigue oxidation precipitation

Secure outsourcing of large matrix determinant computation

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Frontiers of Computer Science 2020年第6期14卷 141-152页

作者： jiayang LIU jingguo bi Mu LI Department of Computer Science and Technology Tsinghua UniversityBeijing 100084China Beijing Research Institute of Telemetry Beijing 100094China Institute for Advanced Study Tsinghua UniversityBeijing 100084China Space Star Technology Co. LtdBeijing 100086China

Cloud computing provides the capability to con-nect resource-constrained clients with a centralized and shared pool of resources,such as computational power and storage on *** matrix determinant computation is almost ubiquitous in computer science and requires large-scale data ***,techniques for securely outsourcing matrix determinant computations to untrusted servers are of utmost importance,and they have practical value as well as theoretical significance for the scientific *** this study,we propose a secure outsourcing method for large matrix determinant *** em-ploy some transformations for privacy protection based on the original matrix,including permutation and mix-row/mix-column operations,before sending the target matrix to the *** results returned from the cloud need to be de-clypled anul verified U ubtainl te cullett ***1 comparison with previously proposed algorithms,our new al-gorithm achieves a higher security level with greater cloud *** experimental results demonstrate the efficiency and effectiveness of our algorithm.

关键词： cloud computing large-scale data computation matrix determinant computation secure outsourcing

Non-isothermal Kinetic Analysis on the Thermal Decomposition of the Phase 517 from Hydration Product of Magnesium Sulfide Cement

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journal of Wuhan University of Technology(Materials Science) 2023年第2期38卷 374-380页

作者： CUI Baodong GUAN Yan bi Wanli School of Materials and Metallurgy University of Science and TechnologyLiaoningAnshan110325China School of Materials Science and Engineering Shenyang Ligong UniversityShenyang110159China

In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was *** of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa *** to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal *** DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide *** three stages correspond to different activation ***,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.

关键词： magnesium sulfide cement comprehensive thermal analysis nonisothermal dynamics 517 phase

Several Properties of a Nonstandard Renewal Counting Process and Their Applications

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journal of Systems Science & Complexity 2020年第1期33卷 122-136页

作者： LI Rong bi Xiuchun ZHANG Shuguang Institute of Statistics and Applied Mathematics Anhui University of Finance and EconomicsBengbu 233030China Department of Statistics and Finance University of Science and Technology of ChinaHefei 230022China

This paper proposes a nonstandard renewal counting process based on web Markov skeleton process,called web renewal process,which allows applications in the field of natural science and social *** with the standard renewal counting process,some properties of the web renewal process and the corresponding web renewal reward processes,are *** limit properties,including the tail of the exponential moments of the web renewal process,and the results of precise large deviations and moderate deviations for the web renewal reward processes are derived.

关键词： Dependence moderate deviations precise large deviations web renewal process web renewal reward process

Subsurface Defect Evaluation of Selective-Laser-Melted Inconel 738LC Alloy Using Eddy Current Testing for Additive/Subtractive Hybrid Manufacturing

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Chinese journal of Mechanical Engineering 2021年第6期34卷 224-239页

作者： Sai Guo Guanhui Ren bi Zhang Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhenGuangdongChina State Key Laboratory of Ultra-precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityKowloonHong KongChina

New materials and manufacturing technologies require applicable non-destructive techniques for quality assurance so as to achieve better *** study comprehensively investigated the effect of influencing factors includ-ing excitation frequency,lift-off distance,defect depth and size,residual heat,and surface roughness on the defect EC signals of an Inconel 738LC alloy produced by selective laser melting(SLM).The experimental investigations recorded the impedance amplitude and phase angle of EC signals for each defect to explore the feasibility of detecting sub-surface defects by merely analyzing these two key ***,this study revealed preliminary qualitative and roughly quantitative relationships between influencing factors and corresponding EC signals,which provided a prac-tical reference on how to quantitively inspect subsurface defects using eddy current testing(ECT)on SLMed parts,and also made solid progress toward on-line ECT in additive/subtractive hybrid manufacturing(ASHM)for fabricating SLMed parts with enhanced quality and better performance.

关键词： Eddy current testing Subsurface defect Additive/subtractive hybrid manufacturing Selective laser melting Inconel 738LC alloy

A high-entropy spinel ceramic oxide as the cathode for proton-conducting solid oxide fuel cells

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journal of Advanced Ceramics 2022年第5期11卷 794-804页

作者： Yangsen XU Xi XU Lei bi School of Resource Environment and Safety Engineering University of South ChinaHengyang 421001China Department of Materials Imperial College London SW72BPUK

A high-entropy ceramic oxide is used as the cathode for the first time for proton-conducting solid oxide fuel cells(H-SOFCs).The Fe_(0.6)Mn_(0.6)Co_(0.6)Ni_(0.6)Cr_(0.6)O_(4)(FMCNC)high-entropy spinel oxide has been successfully prepared,and the in situ chemical stability test demonstrates that the FMCNC material has good stability against CO_(2).The first-principles calculation indicates that the high-entropy structure enhances the properties of the FMCNC material that surpasses their individual components,leading to lower O_(2)adsorption energy for FMCNC than that for the individual *** HSOFC using the FMCNC cathode reaches an encouraging peak power density(PPD)of 1052 mW·cm^(-2)at 700℃,which is higher than those of the H-SOFCs reported *** comparison was made between the high-entropy FMCNC cathode and the traditional Mn_(1.6)Cu_(1.4)O_(4)(MCO)spinel cathode without the high-entropy structure,revealing that the formation of the high-entropy material allows the enhanced protonation ability as well as the movement of the O p-band center closer to the Fermi level,thus improving the cathode catalytic *** a result,the high-entropy FMCNC has a much-decreased polarization resistance of 0.057Ω·cm^(2)at 700℃,which is half of that for the traditional MCO spinel cathode without the high-entropy *** excellent performance of the FMCNC cell indicates that the high-entropy design makes a new life for the spinel oxide as the cathode for HSOFCs,offering a novel and promising route for the development of high-performance materials for H-SOFCs.

关键词： proton-conducting oxides high-entropy oxides cathode solid oxide fuel cells(SOFCs)

Field PMU Test and Calibration Method–Part I:General Framework and Algorithms for PMU Calibrator

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journal of Modern Power Systems and Clean Energy 2022年第6期10卷 1507-1518页

作者： Sudi Xu Hao Liu Tianshu bi State Key Lab of Alternate Electric Power System with Renewable Energy Sources(North China Electric Power University) BeijingChina State Grid jiangsu Electric Power CO. LTD.Research InstituteNanjingChina

Laboratory testing of phasor measurement units(PMUs)guarantees their performance under laboratory ***,many factors may cause PMU measurement problems in actual power systems,resulting in the malfunction of PMU-based ***,field PMUs need to be tested and calibrated to ensure their performance and data *** this paper(Part I),a general framework for the field PMU test and calibration in different scenarios is *** framework consists of a PMU calibrator and an analysis center,where the PMU calibrator provides the reference values for PMU error *** steps are implemented to ensure the calibrator accuracy for complex field signals:①by analyzing the frequency-domain probability distribution of random noise,a Fourier-transform-based signal denoising method is proposed to improve the anti-interference capability of the PMU calibrator;and②a general synchrophasor estimation method based on complex bandpass filters is presented for accurate synchrophasor estimations in multiple *** and experimental test results demonstrate that the PMU calibrator has a higher accuracy than that of other calibrator algorithms and is suitable for field PMU *** analysis center for evaluating the performance of field PMUs and the applications of the proposed field PMU test system are provided in detail in Part II of the next-step research.

关键词： Phasor measurement unit(PMU) calibration synchrophasor signal denoising field PMU test

Fault Feature Extraction of Diesel Engine Based on bispectrum Image Fractal Dimension

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Chinese journal of Mechanical Engineering 2018年第2期31卷 216-226页

作者： jian Zhang Chang-Wen Liu Feng-Rong bi Xiao-Bo bi Xiao Yang State Key Laboratory of Engines Tianjin University

Fault feature extraction has a positive effect on accurate diagnosis of diesel engine. Currently, studies of fault feature extraction have focused on the time domain or the frequency domain of signals. However, early fault signals are mostly weak energy signals, and time domain or frequency domain features will be overwhelmed by strong back?ground noise. In order consistent features to be extracted that accurately represent the state of the engine, bispectrum estimation is used to analyze the nonlinearity, non?Gaussianity and quadratic phase coupling(QPC) information of the engine vibration signals under different conditions. Digital image processing and fractal theory is used to extract the fractal features of the bispectrum pictures. The outcomes demonstrate that the diesel engine vibration signal bispectrum under different working conditions shows an obvious differences and the most complicated bispectrum is in the normal state. The fractal dimension of various invalid signs is novel and diverse fractal parameters were utilized to separate and characterize them. The value of the fractal dimension is consistent with the non?Gaussian intensity of the signal, so it can be used as an eigenvalue of fault diagnosis, and also be used as a non?Gaussian signal strength indicator. Consequently, a symptomatic approach in view of the hypothetical outcome is inferred and checked by the examination of vibration signals from the diesel motor. The proposed research provides the basis for on?line monitoring and diagnosis of valve train faults.

关键词： Engine fault diagnosis bispectrum image processing Fractal Signal processing