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Study on the damage-softening constitutive model of rock and experimental verification

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Acta Mechanica Sinica 2019年第4期35卷 786-798页

作者： sheng-Qi Yang bo Hu Peng Xu State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil Engineering China University of Mining and Technology Xuzhou 221116 China China Construction Third Engineering Design Bureau Co. Ltd Wuhan 430064 China

A damage-softening model is presented to describe the stress-strain curve of rock. By comparing the Hoek-Brown (H-B) and Mohr-Coulomb (M-C) yield criterion, the equivalent M-C yield criterion is selected as the strength criterion in this model. To better characterize the rock damage and failure processes with considering the relationship between damage and deformation, the concept of yield stress ratio is introduced to describe the yield strengthening deformation before rock peak stress. Damage events are described by two cumulative damage evolution laws. The evolution equations of tensile and shear damage are presented based on the equivalent plastic strains and the maximum value between tensile and shear damage represents the total damage for rock. Considering that rock cannot bear tensile load after tensile failure but still has a certain shear strength, its tensile and shear strengths are small after shear failure. The elastic modulus is affected by tensile damage, whereas the angle of internal friction, the cohesion, and dilation angles are influenced by shear damage. The proposed damage-softening model describes the strain-softening, brittle stress-drop, and residual strength of rock after peak stress, and finally the model is implemented in FLAC3D. Comparing the test and the numerical calculation results, the damage-softening model better describes the total stress-strain curve of rock.

关键词： Rock deformation Damage evolution Softening Numerical calculation

MULTI-AGENT AGGREGATION BEHAVIOR ANALYSIS: THE DYNAMIC COMMUNICATION TOPOLOGY

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Journal of Systems Science & Complexity 2008年第2期21卷 209-216页

作者： sheng CHEN Lindu ZHAO Ying han Institute of Systems Engineering Southeast University Nanjing 210018 China

The authors extend the Gazi＇s swarm model with local neighbor rules and the dynamic communication topology, and study its aggregation properties. Results of analysis show that all agents in the models aggregate and eventually form a cohesive cluster of finite size around the swarm center or the appointed point. Finally, simulations are provided to testify some of the results. Models in the paper are more applicable to the reality for the advantage that each agent only needs the partial information of the entire dynamic system when making motion decision.

关键词： Aggregation behavior dynamic communication topology local neighbor rules multi-agent system.

Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells Enhance the Osteoblastic Differentiation of Periodontal Ligament Stem Cells Under High Glucose Conditions Through the PI3K/AKT Signaling Pathway

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Biomedical and Environmental Sciences 2022年第9期35卷 811-820页

作者： YANG Shuo ZHU Biao TIAN Xiao Yu YU han Ying QIAO bo ZHAO Li sheng ZhanG Bin Department of Stomatology The First Medical CenterChinese PLA General HospitalBeijing 100853China Department of Stomatology Fuxing HospitalCapital Medical UniversityBeijing 100038China

Objective High glucose(HG)can influence the osteogenic differentiation ability of periodontal ligament stem cells(PDLSCs).Human umbilical cord mesenchymal stem cell-derived exosomes(hUCMSC-exo)have broad application prospects in tissue *** current study aimed to explore whether hUCMSC-exo could promote the osteogenic differentiation of hPDLSCs under HG conditions and the underlying *** We used a 30 mmol/L glucose concentration to simulate HG ***-8 assay was performed to evaluate the effect of hUCMSC-exo on the proliferation of *** phosphatase(ALP)staining,ALP activity,and qRT-PCR were performed to evaluate the pro-osteogenic effect of hUCMSC-exo on *** blot analysis was conducted to evaluate the underlying *** The results of the CCK-8 assay,ALP staining,ALP activity,and qRT-PCR assay showed that hUCMSC-exo significantly promoted cell proliferation and osteogenic differentiation in a dosedependent *** Western blot results revealed that hUCMSC-exo significantly increased the levels of p-PI3K and p-AKT in cells,and the effect was inhibited by LY294002(PI3K inhibitor)or MK2206(AKT inhibitor),***,the increases in osteogenic indicators induced by hUCMSC-exo were significantly suppressed by LY294002 and *** hUCMSC-exo promote the osteogenic differentiation of hPDLSCs under HG conditions through the PI3K/AKT signaling pathway.

关键词： Exosomes Human umbilical cord mesenchymal stem cell Periodontal ligament stem cell Osteogenic differentiation High glucose PI3K/AKT

Mobile-robotic machining for large complex components:A review study

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Science China(Technological Sciences) 2019年第8期62卷 1388-1400页

作者： TAO bo ZHAO XingWei DING han State Key Laboratory of Digital Manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and Technology

Even though the robotic machining has achieved great success in machining of small components, it lacks the competence to machine large complex components, such as wind turbine blade, train carriage, and aircraft wing. In order to cope with this issue,the mobile machining robot system, which consists of a robot arm integrated with a mobile platform, is proposed to achieve the large workspace and high dexterity, and thus has the potential to machine the large complex components. However, due to the limitation of motion accuracy and structural stiffness, the current mobile-robots are hard to satisfy the high precision requirement of machining tasks. In this paper, some historical mobile-robotic machining systems are reviewed firstly, followed by some key techniques related to structure optimization, dynamics of the machining process, localization, and control techniques, which are fundamental for the structural stiffness and motion accuracy of mobile-robots. Finally, the prospect of mobile-robotic machining and the open questions are addressed.

关键词： robotic machining industrial robot mobile-robot accuracy stiffness

Backstepping Based Global Exponential Stabilization of a Tracked Mobile Robot with Slipping Perturbation

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Journal of Bionic Engineering 2011年第1期8卷 69-76页

作者： bo Zhou Jianda han Xianzhong Dai Key Laboratory of Measurement and Control of CSE (School of Automation Southeast University) Ministry of Education Nanjing 210096 P. R. China Shenyang Institute of Automation CAS Shenyang 110016 P. R. China

While the nonholonomic robots with no-slipping constraints are studied extensively nowadays, the slipping effect is inevitable in many practical applications and should be considered necessarily to achieve autonomous navigation and control purposes especially in outdoor environments. In this paper the robust point stabilization problem of a tracked mobile robot is discussed in the presence of track slipping, which can be treated as model perturbation that violates the pure nonholonomic constraints. The kinematic model of the tracked vehicle is created, in which the slipping is assumed to be a time-varying pa- rameter under certain assumptions of track-soil interaction. By transforming the original system to the special chained form of nonholonomic system, the integrator backstepping procedure with a state-scaling technique is used to construct the controller to stabilize the system at the kinematic level. The global exponential stability of the final system can be guaranteed by Lyapunov theory. Simulation results with different initial states and slipping parameters demonstrate the fast convergence, robustness and insensitivity to the initial state of the proposed method.

关键词： tracked mobile robot nonholonomic system stabilization backstepping Lyapunov function

Effects of Hot Bending Parameters on Microstructure and Mechanical Properties of Weld Metal for X80 Hot Bends

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Journal of Iron and Steel Research International 2014年第12期21卷 1129-1135页

作者： Xu WANG bo LIAO Da-yong WU Xiu-lin han Yuan-sheng ZhanG Fu-ren XIAO Key Laboratory of Metastable Materials Science and Technology College of Materials Science and EngineeringYanshan University CNPC bohai Petroleum Equipment Manufacture Co. Ltd. China Petroleum Technology and Development Corporation

Mechanical properties of weld metal are the key factors affecting the quality of heavy-wall X80 hot induction bends. The effects of bending parameters on the mechanical properties of weld metal for hot bends were investigated by simulation conducted on a Gleeble 3500 thermal simulator. Continuous cooling transformation （CCT） dia- grams of the weld metal were also constructed. The influences of hot bending parameters （such as reheating temperature, cooling rate, and tempering temperature） on the microstructure and mechanical properties of weld metal were also analyzed. Results show that the strength of all weld metal specimens is higher than the value indicated in the technical specification and increases with the increase of reheating temperature, cooling rate, and tempering tempera ture. The impact toughness is apparently related to the variation of reheating temperature, cooling rate, and tempering temperature.

关键词： hot induction bend X80 steel weld metal heat treatment microstructure

Embedding ensemble tracking in a stochastic framework for robust object tracking

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第10期10卷 1476-1482页

作者： Yu GU Ping LI bo han Institute of Industrial Process Control Zhejiang University Hangzhou 310027 China

We propose an algorithm of embedding ensemble tracking in a stochastic framework to achieve robust tracking performance under partial occlusion,illumination changes,and abrupt *** operates on likelihood images generated by the ensemble method,and combines mean shift and particle filtering in a principled way,where a better proposal distribution is de-signed by first propagating particles via a motion model,and then running mean shift to move towards their local peaks in the likelihood *** observation model in the particle filter incorporates global and local information within a region,and an adaptive motion model is adopted to depict the evolution of the object *** algorithm needs fewer particles to manage the tracking task compared with the general particle filter,and recaptures the object quickly after occlusion *** on two image sequences demonstrate the effectiveness and robustness of the proposed algorithm.

关键词： Ensemble tracking Particle filter Mean shift Likelihood mean

Annealing Effect on Wear Resistance of Nanostructured 316L Stainless Steel Subjected to Dynamic Plastic Deformation

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Journal of Materials Science & Technology 2012年第10期28卷 871-877页

作者： bo Wang Bin Yao Zhong han Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang110016China

Bulk nanostructured 316L austenitic stainless steel （SS） samples with nano-scale twin bundles embedded in nano-sized grains were synthesized by using dynamic plastic deformation （DPD）. Subsequent thermal an-nealing of the as-DPD sample leads to a single austenitic structure with static recrystallized （SRX） grains in nanostructured matrix. Oil-lubricated sliding tests of ball-on-disc type were carried out for the as-DPD and the as-annealed DPD steel samples in comparison with coarse grained （CG） steel samples. Experimental results show that the as-DPD 316L steel exhibits a little enhanced wear resistance under a load of 10 N, and nearly identical wear resistance under a load of 30 N relative to that of the CG sample. After annealing, the wear resistance roughly follows the Archard equation under a load of 10 N. However, the wear resistance increases with increasing hardness, and decreases with a further increase in hardness under a load of 30 N. The highest wear resistance can be found in the DPD sample annealed at 750 ℃ for about 20 min, which is more than 46% higher than that of the CG steel sample. This phenomenon is originated from the microstructure with an optimized combination of strength and ductility as a result of moderate plastic deformation in SRX grained regions.

关键词： Nanostructrued metals Stainless steel Wear resistance Annealing Subsurfacemicrostructure

Microstructure evolution of an ultra-high strength metal alloy with tempering temperature

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Rare Metals 2012年第5期31卷 442-445页

作者： WU Sujun HU Bin han bo School of Materials Science and Engineering Beijing University of Aeronautcs and Astronautics Beijing 100191 China

Optical microscopy (OM) and transmission electron microscopy (TEM) were used to investigate the effect of tempering temperature on the experimental extra-high carbon steels. It is found that tempering reaction can reduce austenite content and influence the stability of the austenite. As-normalized microstructure is a mixture of twinned martensite and retained austenite. Tempered at 250 °C for 2 h, lath martensite can occasionally be found nearby the diffusionally decomposed austenite area. It also is found that tempering at 650 °C for 2 h, nanoparticles of carbides precipitate in the martensite and decomposed austenite. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

关键词： Austenite Carbides Carbon steel High strength alloys Martensite Microstructure Optical microscopy Transmission electron microscopy