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A Comparison in Laser Precision Drilling of Stainless Steel 304 with Nanosecond and Picosecond Laser Pulses

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Chinese Journal of Mechanical Engineering 2014年第5期27卷 972-977页

作者： ZHANG Hongyu DI Jianke ZHOU Ming YAN yu State Key Laboratory of Tribology Tsinghua University Center for Photon Manufacturing Science and Technology Jiangsu University Corrosion and Protection Center Beijing University of Science and Technology

Precision drilling with picosecond laser has been advocated to significantly improve the quality of micro-holes with reduced recast layer thickness and almost no heat affected ***,a detailed comparison between nanosecond and picosecond laser drilling techniques has rarely been reported in previous *** the present study,a series of micro-holes are manufactured on stainless steel 304 using a nanosecond and a picosecond laser drilling system,*** quality of the micro-holes,e.g.,recast layer,micro-crack,circularity,and conicity,etc,is evaluated by employing an optical microscope,an optical interferometer,and a scanning electron ***,the micro-structure of the samples between the edges of the micro-holes and the parent material is compared following etching *** researching results show that a great amount of spattering material accumulated at the entrance ends of the nanosecond laser drilled *** formation of a recast layer with a thickness of;5μm is detected on the side walls,associated with initiation of *** phenomenon is also observed and the circularity of the micro-holes is rather *** regard to the micro-holes drilled by picosecond laser,the entrance ends,the exit ends,and the side walls are quite smooth without accumulation of spattering material,formation of recast layer and *** circularity of the micro-holes is fairly good without observation of tapering ***,there is no obvious difference as for the micro-structure between the edges of the micro-holes and the parent *** study proposes a picosecond laser helical drilling technique which can be used for effective manufacturing of high quality micro-holes.

关键词： laser drilling nanosecond laser picosecond laser helical drilling recast layer

Laser cutting of thermoplastic film:Mechanism and processing technology

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Science China(Technological Sciences) 2022年第9期65卷 2068-2078页

作者： WU CongYi RONG YouMin HUANG yu ZHANG GuoJun State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China

The mechanism of ultraviolet(UV) nanosecond laser cutting of thermoplastic films and the influence of process parameters on process quality are systematically *** photothermal effect plays a dominant role in the interaction between the UVnanosecond laser and thermoplastic *** this photothermal reaction,a heat source with the focal point as the core is formed,around which a thermal carbonization layer,a thermal melting layer,and a thermal expansion layer are formed in order from the inside to the *** them,the thermal carbonization layer is not prevalent,and the thermal melting layer and thermal expansion layer are *** process quality can be adjusted by adjusting the cutting speed,the laser power,and the repetition number of cuts to regulate the process of heat generation and heat *** the effective range,the faster the cutting speed and the lower the laser power,the smaller the kerf width and heat-affected zone(HAZ) *** a certain range,the depth of kerf can be increased by increasing the repetition number of cuts.

关键词： laser cutting thermoplastic film mechanism process parameters

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Recent progress in superhydrophobic coating on Mg alloys:A general review

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Journal of Magnesium and Alloys 2021年第5期9卷 1479-1496页

作者： Feng Peng Dongdong Zhang Xuanyong Liu yu Zhang Department of Orthopedics Guangdong Provincial People's HospitalGuangdong Academy of Medical SciencesGuangzhou 510080GuangdongChina State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Cixi Center of Biomaterials Surface Engineering Shanghai Institute of CeramicsChinese Academy of SciencesNingbo 315300China

Magnesium(Mg)is a vital engineering material owing to its light weight and excellent mechanical ***,poor corrosion resistance limits its widely applications as well as its economic ***,surface modification is essential for Mg and its *** the various coatings,superhydrophobic coating,which is inspired by nature,has received increasing attentions in the past *** a water contact angle larger than 150°,superhydrophobic coating can provide sufficient protection for Mg-based *** model of superhydrophobic states and the protection mechanism of superhydrophobic coating are discussed in this ***,the methods for fabricating superhydrophobic coatings on Mg alloys are ***,some functional superhydrophobic coatings on Mg alloys are ***,the challenges and future directions are *** hope that this paper will provide a serviceable review for future research on superhydrophobic coatings on Mg alloys.

关键词： Magnesium alloys Superhydrophobic coatings Corrosion resistance

Recursive Least Square Vehicle Mass Estimation Based on Acceleration Partition

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Chinese Journal of Mechanical Engineering 2014年第3期27卷 448-459页

作者： FENG yuan XIONG Lu yu Zhuoping QU Tong School of Automotive Studies Tongji University Clean Energy Automotive Engineering Center Tongji University

Vehicle mass is an important parameter in vehicle dynamics control systems. Although many algorithms have been developed for the estimation of mass, none of them have yet taken into account the different types of resistance that occur under different conditions. This paper proposes a vehicle mass estimator. The estimator incorporates road gradient information in the longitudinal accelerometer signal, and it removes the road grade from the longitudinal dynamics of the vehicle. Then, two different recursive least square method （RLSM） schemes are proposed to estimate the driving resistance and the mass independently based on the acceleration partition under different conditions. A 6 DOF dynamic model of four In-wheel Motor Vehicle is built to assist in the design of the algorithm and in the setting of the parameters. The acceleration limits are determined to not only reduce the estimated error but also ensure enough data for the resistance estimation and mass estimation in some critical situations. The modification of the algorithm is also discussed to improve the result of the mass estimation. Experiment data on asphalt road, plastic runway, and gravel road and on sloping roads are used to validate the estimation algorithm. The adaptability of the algorithm is improved by using data collected under several critical operating conditions. The experimental results show the error of the estimation process to be within 2.6%, which indicates that the algorithm can estimate mass with great accuracy regardless of the road surface and gradient changes and that it may be valuable in engineering applications. This paper proposes a recursive least square vehicle mass estimation method based on acceleration partition.

关键词： mass estimation recursive least square method acceleration partition

Crack tip fields of piezoelectric materials under antiplane impact

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Chinese Science Bulletin 1997年第19期42卷 1615-1619页

作者： Chen, ZT yu, SW Department of Engineering Mechanics Tsinghua University Beijing 100084 China

THE fracture mechanics of piezoelectric materials is extensively studied under static mechanicalor electrical loads. However, the failure of practical smart structure always happens underdynamic loads, so it is urgently needed to study the fracture dynamics of piezoelectric materi-als. The dynamic Green’s functions for anisotropic piezoelectric materials were proposed byNorris. The dynamic representative formulas and the fundamental solutions were

关键词： crack piezoelectric material anti-plane fracture dynamics.

ANTI-PLANE CRACK MOVING ALONG THE INTERFACE OF DISSIMILAR PIEZOELECTRIC MATERIALS

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Acta Mechanica Solida Sinica 1999年第1期12卷 31-35页

作者： Chen, ZT yu, SW Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The problem of an anti-plane Griffith crack moving along the interface of dissimilar piezoelectric materials is solved by using the integral transform technique. It is shown from the result that the intensity factors of anti-plane stress and electric displacement around the crack tip are dependent on the speed of the Griffith crack as well as the material coefficients. When the two piezoelectric materials are identical, the present result will be reduced to the result far the problem of an anti-plane moving Griffith crack in homogeneous piezoelectric materials.

关键词： interface Griffith crack piezoelectric material anti-plane fracture integral transform technique

NUMERICAL SIMULATION OF THE HYDRODYNAMIC PERFORMANCE OF AN UNSYMMETRICAL FLAPPING CAUDAL FIN

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Journal of Hydrodynamics 2012年第3期24卷 354-362页

作者： ZHANG Xi SU yu-min WANG Zhao-li State Key Laboratory of Autonomous Underwater Vehicle Harbin Engineering University Harbin 150001 China

A comprehensive numerical simulation of the hydrodynamic performance of a caudal fin with unsymmetric flapping motion is carried out. The unsymmetrical motion is induced by adding a pitch bias or a heave bias. A numerical simulation program based on the unsteady panel method is developed to simulate the hydrodynamics of an unsymmetrical flapping caudal fin. A CFD code based on Navier-Stokes equations is used to analyze the flow field. Computational results of both the panel method and the CFD method indicate that the hydrodynamics are greatly affected by the pitch bias and the heave bias. The mean lateral force coefficient is not zero as in contrast with the symmetrical flapping motion. By increasing the pitch bias angle, the mean thrust force coefficient is reduced rapidly. By adding a heave bias, the hydrodynamic coefficients are separated as two parts： in one part, the amplitude is the heave amplitude plus the bias and in the other part, it is the heave amplitude minus the bias. Analysis of the flow field shows that the vortex distribution is not symmetrical, which generates the non-zero mean lateral force coefficient.

关键词： flapping caudal fin caudal fin shape numerical simulations hydrodynamic experiments hydrodynamic performance

Peri-implant gas accumulation in response to magnesium-based musculoskeletal biomaterials:Reframing current evidence for preclinical research and clinical evaluation

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Journal of Magnesium and Alloys 2024年第1期12卷 59-71页

作者： yu Sun Heike Helmholz Regine Willumeit-Römer Institute of Metallic Biomaterials Helmholtz-Zentrum HereonMax-Planck-Str.1Geesthacht 21502Germany

Historically,the rapid degradation and massive gas release from magnesium(Mg)implants resulted in severe emphysema and mechanical *** the advent of new alloys and surface treatment methods,optimized Mg implants have re-entered clinics since last decade with reliable ***,the optimization aims at slowing down the degradation process,rather than exemption of the gas *** study involved a systematic evaluation of current preclinical and clinical evidence,regarding the physical signs,symptoms,radiological features,pathological findings and complications potentially associated with peri±implant gas accumulation(PIGA)after musculoskeletal Mg *** literature search identified 196 potentially relevant publications,and 51 papers were enrolled for further analysis,including 22 preclinical tests and 29 clinical studies published from 2005 to *** Mg-based materials have been evaluated in animal research,and the application of pure Mg and Mg alloys have been reported in clinical follow-ups involving multiple anatomical sites and musculoskeletal *** tissue and intraosseous PIGA are common in both animal tests and clinical follow-ups,and potentially associated with certain adverse *** examinations especially micro-CT and clinical CT scans provide valuable information for quantitative and longitudinal *** according to simulation tests involving Mg implantation and chemical processing,tissue fixation could lead to an increase in the volume of gas cavity,thus the results obtained from ex vivo imaging or histopathological evaluations should be interpreted with *** still lacks standardized procedures or consensus for both preclinical and clinical evaluation of ***,by providing focused insights into the topic,this evidence-based study will facilitate future animal tests and clinical evaluations,and support developing biocompatible Mg implants for the treatment of musculoskeletal

关键词： Magnesium implant Degradation Hydrogen Gas release Postoperative follow-up

DYNAMIC CHARACTERISTIC ANALY-SIS OF PRECISE LONG STROKE LINEAR MOTOR WITH AIR-BEARING IN OPTICAL LITHOGRAPHY

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Chinese Journal of Mechanical Engineering 2008年第2期21卷 17-22页

作者： CHEN Xuedong yu Xianzhong HE Xueming YAN Tianhong State Key Laboratory of Digital Manufacturing Equipment ＆ Technology Huazhong University of Science and Technology Wuhan 430074 China National Optical Lithography Equipment R ＆ D Center Shanghai 201203 China

Dynamic characteristic is presented by identifying the model and the dynamic parameters of a precise long stroke linear motor （PLSLM） with the air-bearing in optical lithography. The PLSLM is supported by air-bearing on the stator, and is driven by on-board two large linear motors in a cross-configuration. Firstly, a model of the PLSLM is established by finite element method （FEM）. Secondly, based on the model, the natural frequencies and model shapes are discusse＆ And the contribution of each active mode is evaluated by computing the modal participation factors （MPF）, which indicates the major vibration direction. Furthermore, by the experimental modal analysis, the experimental results are in agreement with simulation results, which it is sure that the FEM is reasonable. What＇s more, comparing with the effects on the frequency due to the air-bearing stiffness, the relations of the natural frequencies with the air-bearing stiffness are found. It is found that the frequency response curve is fluctuant with the air-bearing stiffness in each direction. Finally, it is conclusion that the natural frequency of the PLSLM is largely affected by the air-bearing stiffness variety. This research is contributed to the dynamic characteristics resulted from the air-beating stiffness. Further work will include better optimization on the dynamic parameter in the controller design through the control algorithm for the precise long stroke motor.

关键词： Dynamic analysis Air-bearing stiffness Precise long stroke linear motor Frequency response