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ANALYTICAL AND NUMERICAL INVESTIGATIONS OF TWO SPECIAL CLASSES OF GENERALIZED CONTINUUM MEDIA

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Acta Mechanica Solida Sinica 2011年第4期24卷 326-339页

作者： Zhaohui Zhang zhanli liu Yuan Gao Junfang Nie Zhuo Zhuang Department of Engineering Mechanics School of AerospaceTsinghua UniversityBeijing 100084China Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing 100084China Naval Academy of Armament Beijing 100073China

In this paper,the micromorphic theory and the second gradient theory are proposedwhere the micromorphic model can be reduced to the second gradient model with the vanishing relative deformation between macrodeformation gradient and *** solutions for the simple shear problem in the case of a general small strain isotropic elasticity micromorphic model and the second gradient model are presented,***,uniaxial tension of a constrained layer with two different boundary conditions is also analytically ***,the micromorphic theory is implemented numerically within a two-dimensional plane strain finite element framework by developing two isoparametric elements.

关键词： micromorphic second gradient boundary layer size effect finite element

An optimized perforation clusters spacing model based on the frictional shale layer’s debonding

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Science China(Physics,Mechanics & Astronomy) 2019年第11期62卷 142-145页

作者： Tao Wang Xuan Ye zhanli liu Yue Gao Zhuo Zhuang School of Aerospace Engineering Tsinghua University

The success of hydraulic fracturing for shale gas recovery has motivated much research interest in understanding the underlying mechanisms (1-3)When hydraulic fractures (HFs) expand, multiple cracks and crack branches... 详细信息

关键词： An optimized perforation clusters spacing model based on the frictional shale layer’s debonding SRV

HIGH SNR SUM CAPACITY ANALYSIS OF BD MIMO BC SYSTEMS WITH IMPERFECT CSI

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Journal of Electronics(China) 2009年第2期26卷 145-151页

作者： Wang Jing liu zhanli Wang Yan You Xiaohu National Mobile Communications Research Lab Southeast University Nanjing 210096 China

We investigate the sum capacity of Block Diagonalization precoding Multiple Input Mul-tiple Output Broadcast Channels(BD MIMO BC) with imperfect Channel State Information(CSI) at the base *** it is difficult to obtain the exact expression,a lower and an upper bounds of the sum capacity under Gaussian channel estimation errors are drived *** show that the gap between two bounds is considerably tight at all Signal to Noise Ratio(SNR) *** the lower bound of the sum capacity,we can see that the multiplexing gain tends to be zero at high SNR region,which indicates that the BD MIMO BC system with channel estimation errors is interference-limited at high SNR.

关键词： Block Diagonalization(BD) Multiple Input Multiple Output Broadcast Channels(MIMO BC) Imperfect Channel State Information(CSI) Sum capacity Multiplexing gain

Analyzing the contribution of helmet components to underwash effect under blast load

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Acta Mechanica Sinica 2024年第11期40卷 1-12页

作者： Jiarui Zhang Zhibo Du Xinghao Wang Yue Kang Tian Ma Zhuo Zhuang zhanli liu School of Aerospace Engineering Tsinghua UniversityBeijing 100084China The Quartermaster Research Institute of General Logistics Department Beijing 100010China

Helmets exacerbate head injuries to some degree under blast load,which has been recently researched and referred to as the underwash *** studies indicate that the underwash effect is attributed to either wave interaction or wave-structure *** ongoing investigations,there is no consensus on the explanations and verification of proposed *** study conducts experiments and numerical simulations to investigate the underwash effect,resulting from the interaction among blast load,helmets,and head *** analysis of overpressure in experiments and simulations,with the developed simplified models that ignore unimportant geometric details,reveals that the underwash effect arises from the combined action of wave interaction and wave-structure *** reflected in front of the head,the blast load converges at the rear after diffraction,forming a high-pressure *** the helmet components demonstrates that the pads alleviate rear overpressure through array hindrance of the load,resulting in a potential reduction of up to 36%in the rear overpressure *** helmet shell exacerbates the rear overpressure peak through geometric restriction of the load after diffraction,leading to a remarkable 388%increase in rear *** prevailing impact of the geometric restriction imposed by the shell of the helmet leads to a significant 57%increase in overpressure when employing a complete helmet.

关键词： Blast load Helmet Underwash effect Geometric restriction Array hindrance

Nonlinear dynamic response and stability analysis of the stapes reconstruction in human middle ear

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Applied Mathematics and Mechanics(English Edition) 2023年第10期44卷 1739-1760页

作者： Lele WANG Liang WANG Yueting ZHU zhanli liu Yongtao SUN Jie WANG Hongge HAN Shuyi XIANG Huibin SHI Qian DING Department of Mechanics Tianjin UniversityTianjin 300350China Tianjin Key Laboratory of Nonlinear Dynamics and Control Tianjin UniversityTianjin 300350China Department of Otolaryngology Head and Neck SurgeryTianjin Children's HospitalTianjin UniversityTianjin 300400China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Department of Otolaryngology Head and Neck Surgery Beijing Tongren HospitalCapital Medical UniversityBeijing 100730China Key Laboratory of Otolaryngology Head and Neck Surgery Ministry of EducationBeijing 100730China Beijing Engineering Research Center of Audiological Technology Beijing 100730China

Stapes fracture causes hearing loss and instability in the middle ear hearing system(MEHS). The material used in the stapes reconstruction restores stapes, but the effects of the nonlinear material parameters on the stability of the MEHS are still unknown. To address this challenge, the nonlinear dynamic response and stability of the stapes reconstruction are investigated using a multi-degree-of-freedom mechanical model. The material parameters of the implant are tentatively determined by analyzing the natural frequencies of the undamped system. The dynamical properties of the MEHS are characterized under different external excitations. The approximate solution of the MEHS near the resonant frequency is derived through the multiple-time-scale method(MTSM). The results show that the nonlinear stiffness of the material has little influence on the MEHS in the healthy state, but it causes resonant phenomena between the ossicle and the implant in the pathological state.

关键词： crus fracture of stapes stapes reconstruction dynamic analysis bifurcation analysis multiple-time-scale method(MTSM)

PERFORMANCE OF THE ZERO FORCING PRECODING MIMO BROADCAST SYSTEMS WITH CHANNEL ESTIMATION ERRORS

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Journal of Electronics(China) 2007年第4期24卷 490-495页

作者： Wang Jing liu zhanli Wang Yan You Xiaohu National Mobile Communications Research Lab Southeast University Nanjing 210096 China

In this paper, the effect of channel estimation errors upon the Zero Forcing (ZF) precoding Multiple Input Multiple Output Broadcast (MIMO BC) systems was studied. Based on the two kinds of Gaussian estimation error models, the performance analysis is conducted under different power allocation strategies. Analysis and simulation show that if the covariance of channel estimation errors is independent of the received Signal to Noise Ratio (SNR), imperfect channel knowledge deteriorates the sum capacity and the Bit Error Rate (BER) performance severely. However, under the situation of orthogonal training and the Minimum Mean Square Error (MMSE) channel estimation, the sum ca- pacity and BER performance are consistent with those of the perfect Channel State Information (CSI) with only a performance degradation.

关键词： Zero Forcing (ZF) Multiple Input Multiple Output BroadCast (MIMO BC) system Channel estimation errors Sum capacity

Multiscale engineered artificial compact bone via bidirectional freeze-driven lamellated organization of mineralized collagen microfibrils

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Bioactive Materials 2024年第10期40卷 168-181页

作者： Lingwenyao Kong Yonggang Zhao Yang Xiong Junlin Chen Shuo Wang Ziming Yan Huibin Shi zhanli liu Xiumei Wang State Key Laboratory of New Ceramics and Fine Processing Key Laboratory of Advanced Materials of Ministry of EducationSchool of Materials Science and EngineeringTsinghua UniversityBeijing100084China State Key Laboratory for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials Tubular Goods Research Institute of CNPCXi’an710077China Department of Orthopedics Dongzhimen HospitalBeijing University of Chinese MedicineBeijingChina School of Aerospace Engineering Tsinghua UniversityBeijing100084China

Bone,renowned for its elegant hierarchical structure and unique mechanical properties,serves as a constant source of inspiration for the development of synthetic ***,achieving accurate replication of bone features in artificial materials with remarkable structural and mechanical similarity remains a significant *** this study,we employed a cascade of continuous fabrication processes,including biomimetic mineralization of collagen,bidirectional freeze-casting,and pressure-driven fusion,to successfully fabricate a macroscopic bulk material known as artificial compact bone(ACB).The ACB material closely replicates the composition,hierarchical structures,and mechanical properties of natural *** demonstrates a lamellated alignment of mineralized collagen(MC)microfibrils,similar to those found in natural ***,the ACB exhibits a similar high mineral content(70.9%)and density(2.2 g/cm3)as natural cortical bone,leading to exceptional mechanical properties such as high stiffness,hardness,and flexural strength that are comparable to those of natural ***,the ACB also demonstrates excellent mechanical properties in wet,outstanding biocompatibility,and osteogenic properties in vivo,rendering it suitable for a broad spectrum of biomedical applications,including orthopedic,stomatological,and craniofacial surgeries.

关键词： Artificial compact bone Bidirectional freeze-casting Mineralized collagen microfibril Hierarchical structures

Numerical study on dynamic mechanism of brain volume and shear deformation under blast loading

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Acta Mechanica Sinica 2019年第5期35卷 1104-1119页

作者： Zhijie Li Zhibo Du Xiaochuan You zhanli liu Jian Cheng Chengcheng Luo Dongyang Chu Shaowu Ning Yue Kang Ce Yang Zhuo Zhuang School of Aerospace Engineering Tsinghua UniversityBeijing 100084China School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Daping Hospital Army Medical UniversityChongqing 400038China

Blast-induced traumatic brain injury(b-TBI)is a kind of significant injury to soldiers in the current military ***,the mechanism of b-TBI has not been well understood,and even there are some contradictory *** is crucial to reveal the dynamic mechanism of brain volume and shear deformations under blast loading for better understanding of *** this paper,the numerical simulation method is adopted to carry out comprehensive and in-depth researches on this issue for the first *** on the coupled Eulerian-Lagrangian method,the fluid-structure coupling model of the blast wave and human head is developed to simulate two situations,namely the head subjected to the frontal and lateral *** simulation results are analyzed to obtain the underlying dynamic mechanisms of brain *** brain volume deformation is dominated by the local bending vibration of the skull,and the corresponding frequency for the forehead skull under the frontal impact and the lateral skull faced to the lateral impact is as high as 8 kHz and 5 kHz,*** leads to the high-frequency fluctuation of brain pressure and the large pressure gradient along the skull,totally different from the dynamic response of brain under head *** the brain shear deformation mainly depends on the relative tangential displacement between the skull and brain and the anatomical structure of inner skull,being not related to the brain pressure and its *** further comparing the medical statistics,it is inferred that diffuse axonal injury and brain contusion,the two most common types of b-TBI,are mainly attributed to brain shear *** the von Mises stress can be adopted as the indicator for these two brain *** study can provide theoretical guidance for the diagnosis of b-TBI and the development of protective equipment.

关键词： Blast-induced traumatic brain injury Numerical head model Fluid-structure coupling model Diffuse axonal injury Brain contusion

Finite element analysis for wellbore stability of transversely isotropic rock with hydraulic-mechanical-damage coupling

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Science China(Technological Sciences) 2017年第1期60卷 133-145页

作者： WANG YongLiang liuzhanli YANG HengLin ZHUANG Zhuo Drilling Research Institute China National Petroleum Corporation Beijing 100195 China

The finite element analysis （FEA） technology by hydraulic-mechanical-damage （HMD） coupling is proposed in this paper for wellbore stability analysis of transversely isotropic rock, developed basing on the recently established FEA technology for iso- tropic rock. The finite element （FE） solutions of numerical wellbore model, damage tensor calculation and Pariseau strength criterion for transversely isotropic rock are developed for researching the wellbore failure characteristics and computing the collapse and fracture pressure of laminated rock as shale reservoirs. The classic Blot constitutive for rock as porous medium is introduced to establish a set of FE equations coupling with elastic solid deformation and seepage flow. To be in accord with the inclined wellbore situation, the coordinate transformation for global, wellbore, in-situ stress and transversely isotropic for- mation coordinate systems is established for describing the in-situ stress field and the results in laminated rock. To be in accord with the practical situation, a three-dimensional FIE model is developed, in which several other auxiliary technologies are com- prehensively utilized, e.g., the typical Weibull distribution function for heterogeneous material description and adaptive tech- nology for mesh refinement. The damage tensor calculation technology for transversely isotropic rock are realized from the well-developed continuum damage variable of isotropic rock. The rock is subsequently developed into a novel conceptual and practical model considering the stress and permeability with the damage. The proposed method utilizing Parisean strength cri- terion fully reflects the strength parameters parallel or perpendicular to bedding of the transversely isotropic rock. To this end, an effective and reliable numerically three-step FEA strategy is well established. Numerical examples are given to show that the proposed method can establish efficient and applicable FE model and be suitable for analyz

关键词： finite element analysis wellbore stability transversely isotropic rock damage tensor hydraulic-mechanical-damagecoupling