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Influence of Strut Cross-section of Stents on Local Hemodynamics in Stented Arteries

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Chinese Journal of Mechanical engineering 2016年第3期29卷 624-632页

作者： JIANG Yongfei ZHANG Jun ZHAO Wanhua State Key Laboratory for Manufacturing System Engineering Xi'an Jiaotong University

Stenting is a very effective treatment for stenotic vascular diseases, but vascular geometries altered by stent implantation may lead to flow disturbances which play an important role in the initiation and progression of restenosis, especially in the near wall in stented arterial regions. So stent designs have become one of the indispensable factors needed to be considered for reducing the flow disturbances. In this paper, the structural designs of strut cross-section are considered as an aspect of stent designs to be studied in details. Six virtual stents with different strut cross-section are designed for deployments in the same ideal arterial model. Computational fluid dynamics（CFD） methods are performed to study how the shape and the aspect ratio（AR） of strut cross-section modified the local hemodynamics in the stented segments. The results indicate that stents with different strut cross-sections have different influence on the hemodynamics. Stents with streamlined cross-sectional struts for circular arc or elliptical arc can significantly enhance wall shear stress（WSS） in the stented segments, and reduce the flow disturbances around stent struts. The performances of stents with streamlined cross-sectional struts are better than that of stents with non-streamlined cross-sectional struts for rectangle. The results also show that stents with a larger AR cross-section are more conductive to improve the blood flow. The present study provides an understanding of the flow physics in the vicinity of stent struts and indicates that the shape and AR of strut cross-section ought to be considered as important factors to minimize flow disturbance in stent designs.

关键词： stent restenosis wall shear stress hemodynamics computational fluid dynamics

Design of 3D-printed Cable Driven Humanoid Hand Based on Bidirectional Elastomeric Passive Transmission

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Chinese Journal of Mechanical engineering 2021年第4期34卷 225-235页

作者： Teru Chen Xingwei Zhao Guocai Ma Bo Tao Zhouping Yin state key laboratory of Digital manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China state key laboratory of Intelligent manufacturing system Technology Beijing Institute of Electronic System EngineeringBeijing 100854China

Motion control of the human hand is the most complex part of the human body.It has always been a challenge for a good balance between the cost,weight,responding speed,grasping force,finger extension,and dexterity of prosthetic hand.To solve these issues,a 3D-printed cable driven humanoid hand based on bidirectional elastomeric passive transmission(BEPT)is designed in this paper.A semi-static model of BEPT is investigated based on energy conservation law to analyze the mechanical properties of BEPT and a dynamical simulation of finger grasping is conducted.For a good imitation of human hand and an excellent grasping performance,specific BEPT is selected according to human finger grasping experiments.The advantage of BEPT based humanoid hand is that a good balance between the price and performance of the humanoid hand is achieved.Experiments proved that the designed prosthetic hand’s single fingertip force can reach 33 N and the fastest fingertip grasping speed realized 0.6 s/180°.It also has a good force compliance effect with only 430g’s weight.It can not only grab fragile objects like raw eggs and paper cup,but also achieve strong grasping force to damage metal cans.This humanoid hand has considerable application prospects in artificial prosthesis,human-computer interaction,and robot operation.

关键词： Humanoid hand Bidirectional elastomeric passive transmission Artificial prosthesis

Extended DMPs Framework for Position and Decoupled Quaternion Learning and Generalization

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Chinese Journal of Mechanical engineering 2022年第4期35卷 227-239页

作者： Zhiwei Liao Fei Zhao Gedong Jiang Xuesong Mei State Key Laboratory for Manufacturing System Engineering Xi’an Jiaotong UniversityXi’an 710049China Shaanxi key laboratory of Intelligent Robots and School of Mechanical engineering Xi’an Jiaotong UniversityXi’an 710049China

Dynamic movement primitives(DMPs)as a robust and efcient framework has been studied widely for robot learning from demonstration.Classical DMPs framework mainly focuses on the movement learning in Cartesian or joint space,and can’t properly represent end-efector orientation.In this paper,we present an extended DMPs framework(EDMPs)both in Cartesian space and 2-Dimensional(2D)sphere manifold for Quaternion-based orientation learning and generalization.Gaussian mixture model and Gaussian mixture regression(GMM-GMR)are adopted as the initialization phase of EDMPs to handle multi-demonstrations and obtain their mean and covariance.Additionally,some evaluation indicators including reachability and similarity are defned to characterize the learning and generalization abilities of EDMPs.Finally,a real-world experiment was conducted with human demonstrations,the endpoint poses of human arm were recorded and successfully transferred from human to the robot.The experimental results show that the absolute errors of the Cartesian and Riemannian space skills are less than 3.5 mm and 1.0°,respectively.The Pearson’s correlation coefcients of the Cartesian and Riemannian space skills are mostly greater than 0.9.The developed EDMPs exhibits superior reachability and similarity for the multi-space skills’learning and generalization.This research proposes a fused framework with EDMPs and GMM-GMR which has sufcient capability to handle the multi-space skills in multi-demonstrations.

关键词： Learning from demonstration Dynamic movement primitives 2D sphere manifold Gaussian mixture model Gaussian mixture regression Quaternion-based orientation

Transfer film effects induced by 3D-printed polyether-ether-ketone with excellent tribological properties for joint prosthesis

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Bio-Design and manufacturing 2024年第1期7卷 43-56页

作者： Yang Li Jibao Zheng Changning Sun Dichen Li State Key Laboratory for Manufacturing System Engineering School of Mechanical EngineeringXi’an Jiaotong UniversityXi’an 710054China National Medical Products Administration(NMPA)key laboratory for Research and Evaluation of Additive manufacturing Medical Devices Xi’an Jiaotong UniversityXi’an 710054China

Based on the building principle of additive manufacturing,printing orientation mainly determines the tribological properties of joint prostheses.In this study,we created a polyether-ether-ketone(PEEK)joint prosthesis using fused filament fabrication and investigated the effects of printing orientation on its tribological properties using a pin-on-plate tribometer in 25% newborn calf serum.An ultrahigh molecular weight polyethylene transfer film is formed on the surface of PEEK due to the mechanical capture of wear debris by the 3D-printed groove morphology,which is significantly impacted by the printing orientation of PEEK.When the printing orientation was parallel to the sliding direction of friction,the number and size of the transfer film increased due to higher steady stress.This transfer film protected the matrix and reduced the friction coefficient and wear rate of friction pairs by 39.13%and 74.33%,respectively.Furthermore,our findings provide a novel perspective regarding the role of printing orientation in designing knee prostheses,facilitating its practical applications.

关键词： 3D printing orientation Transfer film Tribological properties Polyether-ether-ketone Knee prosthesis

Robotic mobile and mirror milling of large-scale complex structures

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National Science Review 2023年第5期10卷 10-13页

作者： Zenghui Xie Fugui Xie Limin Zhu Xin-Jun Liu state key laboratory of Tribology in Advanced Equipment Department of Mechanical Engineering(DME) Tsinghua University Beijing key Lab of Precision/Ultra-precision manufacturing Equipments and Control Tsinghua University state key laboratory of Mechanical system and Vibration School of Mechanical EngineeringShanghai Jiao Tong University

Large-scale complex structures,such as spacecraft cabins,aircraft composite skins and launch vehicle fuel tanks,are the core components of the equipment in aerospace,energy,shipbuilding and other fields.Their milling quality and efficiency are factors directly affecting the performance and productivity of spacecraft,aircraft and other key equipment.This kind of structure generally features large dimension,high accuracy,

关键词： COMPENSATION PARTS

A Dual-Platform Laser Scanner for 3D Reconstruction of Dental Pieces

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engineering 2018年第6期4卷 796-805页

作者： Shuming Yang Xinyu Shi Guofeng Zhang Changshuo Lv State Key Laboratory for Manufacturing System Engineering Xi’an Jiaotong UniversityXi’an 710049China

This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional(3D)laser-scanning method.The scanner combines translation and rotation platforms to perform a holistic scanning.A hybrid calibration method for laser scanning is proposed to improve convenience and precision.This method includes an integrative method for data collection and a hybrid algorithm for data processing.The integrative method conveniently collects a substantial number of calibrating points with a stepped gauge and a pattern for both the translation and rotation scans.The hybrid algorithm,which consists of a basic model and a compensation network,achieves strong stability with a small degree of errors.The experiments verified the hybrid calibration method and the scanner application for the measurement of dental pieces.Two typical dental pieces were measured,and the experimental results demonstrated the validity of the measurement that was performed using the dual-platform scanner.This method is effective for the 3D reconstruction of dental pieces,as well as that of objects with irregular shapes in engineering fields.

关键词： Laser scanning Hybrid calibration Neural network Dental pieces

Nonlinear impedance control with trajectory adaptation for collaborative robotic grinding

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Science China(Technological Sciences) 2023年第7期66卷 1928-1936页

作者： HAN FengTao TAM SikYuen CAO ZhiHong ZHAO XingWei TAO Bo DING Han state key laboratory of Intelligent manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China state key laboratory of Intelligent manufacturing system Technology for Complex Products Beijing Institute of Electronic System EngineeringBeijing 100854China ROKAE(Beijing)Technology Co. Ltd.Beijing 100193China

Stiffness adjustment is an important feature of human arm control.The adaptive variable impedance control can adapt to the robotic stiffness,but may result in a large overshoot.In this paper,nonlinear impedance control is proposed for collaborative robotic grinding,where nonlinear force feedback is designed to compensate for the nonlinear stiffness of the environment.Thus,the interaction system can be linearization to ensure the system stability.Moreover,a target trajectory adaptation strategy is studied to ensure the force tracking requirement.Then,switching law between trajectory tracking and force tracking is proposed when the robot performs a complex grinding task.The stability of the switch control as well as the trajectory adaptation law is proved.Experiments are conducted in a robotic grinding test rig,where the robot is used to grind a turbine blade.Experimental results show that the nonlinear impedance control can obtain stable grinding force,and have better grinding quality than the linear impedance control.

关键词： impedance control robotic grinding trajectory adaptation force tracking

High-Efficiency Dynamic Scanning Strategy for Powder Bed Fusion by Controlling Temperature Field of the Heat-Affected Zone

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Chinese Journal of Mechanical engineering 2024年第1期37卷 203-214页

作者： Xiaokang Huang Xiaoyong Tian Qi Zhong Shunwen He Cunbao Huo Yi Cao Zhiqiang Tong Dichen Li state key laboratory of manufacturing systems engineering Xi’an Jiaotong UniversityXian 710049China

Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature field using an infrared thermal imager has been established and integrated into a four-laser PBF equipment with a working area of 2000 mm×2000 mm.The heat-affected zone(HAZ)temperature field has been controlled by adjusting the scanning speed dynamically.Simultaneously,the relationship among spot size,HAZ temperature,and part performance has been established.The fluctuation of the HAZ temperature in four-laser scanning areas was decreased from 30.85℃to 17.41℃.Thus,the consistency of the sintering performance of the produced large component has been improved.Based on the controllable temperature field,a dynamically adjusting strategy for laser spot size was proposed,by which the fabrication efficiency was improved up to 65.38%.The current research results were of great significance to the further industrial applications of large-scale PBF equipment.

关键词： Powder bed fusion Efficiency Large-scale Spot size Heat-affected zone(HAZ)

Oxidation behavior of 4774DD1 Ni-based single-crystal superalloy at 980℃ in air

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China Foundry 2024年第2期21卷 116-124页

作者： Yu Fang Ya-zhou Li Qiang Yang Qun-gong He Xiu-fang Gong Qian Duan Hai-yang Song Fu Wang Qiong-yuan Zhang Hong Zeng state key laboratory of Long-Life High Temperature Materials Dongfang Turbine Co.Ltd.Deyang 618000SichuanChina State Key Laboratory for Manufacturing System Engineering School of Mechanical EngineeringXi’an Jiaotong UniversityXi’an 710049China

The oxidation behavior of a novel Ni-based single-crystal 4774DD1 superalloy for industrial gas turbine applications was investigated by the isothermal oxidation at 980℃ and discontinuous oxidation weight gain methods.The phase constitution and morphology of surface oxides and the characteristics of the crosssection oxide film were analyzed by XRD,SEM and EDS.Results show that the oxidation kinetics of the 4774DD1 superalloy follows the cubic law,indicating its weak oxidation resistance at this temperature.As the oxidation time increases,the composition of the oxide film evolves as following:One layer consisting of a bottom Al_(2)O_(3)sublayer and an upper(Al_(2)O_(3)+NiO)mixture sublayer after oxidized for 25 h.Then,two layers composed of an outermost small NiO discontinuous grain layer and an internal layer for 75 h.This internal layer is consisted of the bottom Al_(2)O_(3)sublayer,an intermediate narrow CrTaO_(4)sublayer,and an upper(Al_(2)O_(3)+NiO)mixture sublayer.Also two layers comprising an outermost relative continuous NiO layer with large grain size and an internal layer as the oxidation time increases to 125 h.This internal layer is composed of the upper(Al_(2)O_(3)+NiO)mixture sublayer,an intermediate continuous(CrTaO_(4)+NiWO_(4))mixture sublayer,and a bottom Al_(2)O_(3)sublayer.Finally,three layers consisting of an outermost(NiAl2O_(4)+NiCr2O_(4))mixture layer,an intermediate(CrTaO_(4)+NiWO_(4))mixture layer,and a bottom Al_(2)O_(3)layer for 200 h.

关键词： nickel-base single crystal superalloy oxidation kinetics oxide film microstructure mechanism