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Theoretical & Applied Mechanics letters 2022年第3期12卷 178-183页

作者： Yangyang zhang ji Wang Chaofeng lü Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China College of Civil Engineering and Architecture Soft Matter Research Centerand Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhou 310058China

Flexible piezoelectric energy harvesters(PEHs)have gained lots of attention in recent years,because of their potential biomechanical applications,such as powering implantable *** in vivo animal experiments have demonstrated that the output power of a flexible PEH varies remarkably with patching orientations and locations,but the underlying mechanism remains unclear ***,an electromechanical model for a flexible PEH installed on a beating heart is proposed,and a concise relationship between the output power of the device and myocardium strain is *** results demonstrate that the patching orientations have a significant impact on the output power of the PEH,and the optimal patching orientations for all patching locations are approximately 15–20 degree for PEHs mounted on the left *** simple theoretical method provided here would be universally effective for choosing the optimal patching locations and orientations of flexible PEHs installed on a nonhomogeneous deformed surface.

关键词： Biomechanical energy harvester Flexible electronics Heart motion Myocardial strain

Nonplanar flow-induced vibrations of a cantilevered PIP structure system concurrently subjected to internal and cross flows

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Acta Mechanica Sinica 2019年第6期35卷 1241-1256页

作者： z.Y.liu T.l.jiang l.Wang H.l.Dai Department of Mechanics Huazhong University of Science and TechnologyWuhan 430074China Hubei Key laboratory for Engineering Structural Analysis and Safety Assessment Wuhan 430074China

Pipe-in-pipe(PIP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PIP structure system usually consists of two concentric pipes and one softer layer for thermal insulation *** total response of the system is related to the dynamics of both pipes and the interactions between these two concentric *** the current work,a theoretical model for flow-induced vibrations of a PIP structure system is proposed and analyzed in the presence of an internal axial flow and an external cross *** interactions between the two pipes are modeled by a linear distributed damper,a linear distributed spring and a nonlinear distributed spring along the pipe *** unsteady hydrodynamic forces due to cross flow are modeled by two distributed van der Pol wake *** nonlinear partial differential equations for the two pipes and the wake are further discretized by the aid of Galerkin’s technique,resulting in a set of ordinary differential *** ordinary differential equations are further numeri cally solved by using a fourth-order Runge-Kutta integration *** portraits,bifurcation diagrams,an Argand diagram and oscillation shape diagrams are plotted,showing the existence of a lock-in phenomenon and figure-of-eight *** PIP system subjected to cross flow displays some interesting dynamical behaviors different from that of a single-pipe structure.

关键词： Cantilevered PIP structure Theoretical model Flow-induced vibration Cross flow Internal flow

Coarsening Behavior of Gamma Prime Precipitates in a Nickel Based Single Crystal Superalloy

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Journal of Materials Science & Technology 2016年第2期32卷 172-176页

作者： S.Tang l.K.Ning T.z.Xin z.zheng University of Chinese Academy of Sciences.Beijing 100049.China Superalloy Division.Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The γ/γ＇ microstructural evolution in a nickel based single crystal superalloy during load-free thermal exposure at 900 ℃ has been further investigated in this paper. The growth characteristics of γ＇ precipitates were discussed in detail. The generation of interfacial dislocations would accelerate the rate of coalescence in the dendrite arms. The average sizes of precipitates were used to compare interface with diffusion controlled growth mechanism and no mechanism seems obviously dominant, although the square rate law gives slightly better fit. The coarsening behavior may be controlled by diffusion through the ragged interface between the γ＇ precipitate and the y matrix.

关键词： Single crystal superalloy Coarsening Interfacial dislocations Rate controlling mechanism

Constitutive equation and model validation for a 31 vol.% B_4Cp/6061Al composite during hot compression

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Journal of Materials Science & Technology 2018年第10期34卷 1730-1738页

作者： l. zhou C. Cui Q.z. Wang C. li B.l. Xiao z.Y. Ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of B4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% B4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in B4C/AI composites.

关键词： Composites B4C/AI Constitutive equation Hot compression Finite element simulation

Effect of liver regeneration on malignant hepatic tumors

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World Journal of Gastroenterology 2014年第43期20卷 16167-16177页

作者： ji-Hua Shi P?l-Dag line Department of Transplantation Medicine Institute for Surgical ResearchOslo University HospitalPostboks 4950Nydalen 0424OsloNorway

liver regeneration after major surgery may activate occult micrometastases and facilitate tumor growth,leading to liver tumor *** changes during liver regeneration can provide a microenvironment that stimulates intrahepatic tumor propagation through alterations in cellular signaling pathways,where activation and proliferation of mature hepatocytes,hepatic progenitor cells,non-parenchymal liver cells might favor both liver regeneration and tumor *** review highlights recent advances of tumor growth and development in the regenerating liver,possible mechanisms and clinical implications.

关键词： Hepatocellular carcinoma Colorectal cancer Recurrence liver regeneration Hepatic progenitor cell Epithelial to mesenchymal transition

Investigation on Aging-induced Softening of Eutectic Microstructure in SnBi/Cu Interconnect by Nanoindentation

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Journal of Materials Science & Technology 2006年第1期22卷 130-134页

作者： Chunzhong lIU ji CHEN P.l.liu jianku SHANG Shenyang National laboratory ior Materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China Department of Materials Engineering Shenyang Institute of Aeronautical Engineering Shenyang 110034 China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana IL 61801USA

Nanoindentation was used to probe softening of the eutectic microstructure in a SnBi/Cu interconnect following thermal aging. Tests were conducted at constant loading rates and under constant loads to characterize the flow stress and creep behavior of the eutectic microstructure. Aging was found to reduce the flow stress but to increase strain-rate sensitivity of the eutectic SnBi microstructure. While the reduction in the flow stress was related to the coarsening of the eutectic microstructure, the increased creep rate sensitivity was resulted from additional contribution of grain boundary movement to indentation creep.

关键词： Solder Interconnect Nanoindentation Creep Deformation

Prediction of Dynamic and Aerodynamic Characteristics of the Centrifugal Fan with Forward Curved Blades

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Journal of Thermal Science 2013年第6期22卷 517-521页

作者： jií Polansky lászló Kalmár Roman Gápár Univerzitní 8 306 14 PlzeňCzech Republic Miskolc-Egyetemváros MiskolcHungary

The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteristics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant contains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length[1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were performed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine characteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also partially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calculation stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition.

关键词： Centrifugal Fan CFD Pressure Coefficient Flow Coefficient

Effect of Carbon Nanotube Orientation on Mechanical Properties and Thermal Expansion Coefficient of Carbon Nanotube-Reinforced Aluminum Matrix Composites

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Acta Metallurgica Sinica(English letters) 2014年第5期27卷 901-908页

作者： z.Y.liu B.l.Xiao W.G.Wang z.Y.Ma School of Materials Science and Engineering Dalian University of Technology Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences School of Mechanical Engineering Liaoning Shihua University

Carbon nanotube-reinforced 2009Al （CNT/2009Al） composites with randomly oriented CNTs and aligned CNTs were fabricated by friction stir processing （FSP） and FSP-rolling, respectively. The CNT/2009A1 composites with aligned CNTs showed much better tensile properties at room temperature and elevated temperature compared with those with the randomly oriented CNTs, which is mainly attributed to larger equivalent aspect ratio of the CNTs and avoidance of preferential fracture problems. However, much finer grain size was not beneficial to obtaining high strength above 473 K. The aligned CNTs resulted in tensile anisotropy, with the best tensile properties being achieved along the direction of CNT aligning. As the off-axis angle increased, the tensile properties were reduced due to the weakening of the load transfer ability. Furthermore, aligned CNTs resulted in much lower coefficient of thermal expansion compared with randomly oriented CNTs.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Coefficient of thermalexpansion Friction stir processing

INFlUENCE OF lOCAl BRITTlE zONE ON THE FRACTURETOUGHNESS OF HIGH-STRENGTH lOW-AllOYEDMUlTIPASS WElD METAlS

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Acta Metallurgica Sinica(English letters) 1998年第2期11卷 87-92页

作者： z.l.zhou S.H.liu Dalian Railway Inst Dalian China

In this paper, toughness properties and microstructurc of low-alloyed multipass welds with yield strength above 700MPa have 6een studied using the weld thermal simulation and throughout thickness CTOD fracture mechanics tests. Impact testing of thermal simulated specimens showed that the primary weld metal and the fine gmmed weld metal had good toughness, while the coarse grained weld metal had the lowest toughness value as the local brittle zone (lBz) in multipass weld metals. Cleavage fracture in CTOD testing of thick multipass weld metals was initiated from martensite-austenite (MA) phases in the lBz. MA phases were distributed at the prior austenite grain boundaries and around ferrite grains. As the size of the local brittle zone along the fatigue crack front increases, CTOD frncture toughness of multipass weld metals decreases. The weakest link theory was used to evaluate effect of the local brittle zone on fracture toughness of thick multipass weld metals. The estimated curves agree well with the eaperimental data.

关键词： multipass weld metal local brittle zone weld thermal simulation CTOD fracture toughness

A NOVEl METHOD FOR EVAlUATING PlANE STRESS DYNAMIC FRACTURE TOUGHNESS OF 0Cr18Ni10Ti STAINlESS STEEl WElDED JOINTS

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Acta Metallurgica Sinica(English letters) 2008年第4期21卷 303-312页

作者： z.J. Xu Y.l. li School of Aeronautics Northwestern Polytechnical University Xi＇an 710072 China

A novel method was proposed for the evaluation of Mode I dynamic fracture toughness （DFT） under plane stress and small scale yielding conditions for welded joints of stainless steel （SS）, 0Cr18Ni10Ti. In a hybrid experimental-numerical approach, the experiments were carried out on the Hopkinson pressure bar apparatus, and three dimensional （3D） transient numerical simulations were performed by a finite element （FE） computer program. Macroscopical plastic deformation was observed at the loading and supporting points, on the specimens, after the test, which could cause a large error if omitted in the numerical simulation. Therefore, elustic-viscoplustic analysis was performed on the specimen by adopting the Johnson-Cook （J-C） model to describe the rate-dependent plastic flow behavior of the material. The material heterogeneity in the mismatched welded joints, induced by the difference in the base metal （BM） and the weld metal （WM） in yield stress, has also been taken into consideration by using the J-C models separately. Good accordance was obtained between the experimental and the computational results by the present approach. The relationship between plane stress DFT and loading rate was also obtained on the order of 108 MPa.m^1/2.s^-1.

关键词： 0Cr18Ni10Ti Welded joint High strain rate Dynamic fracture Plane stress