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Science China(Physics,mechanics & Astronomy) 2025年第1期68卷 152-164页

作者： Yifeng Li Zhuoran Yang Ziming Yan Huibin Shi Zhanli Liu Kaijie Wang Department of Engineering mechanics School of Aerospace EngineeringTsinghua UniversityBeijing 100084China Beijing Tongren Eye Center Beijing Tongren HospitalCapital Medical UniversityBeijing Ophthalmology&Visual Sciences Key LabBeijing 100730China

Orthokeratology(OK)is widely used for effective myopia correction and ***,the incomplete understanding of its biomechanical mechanisms makes OK lens fitting rely heavily on clinician judgment,complicating accurate predictions of treatment *** this paper,we performed clinical experiments and numerical analysis to study corneal deformation modes and long-term changes in central corneal *** experiments were conducted on 194 Chinese myopic patients under OK treatment for 3 *** on the experimental data,a patient-specific computational biomechanical model for OK was established and ***,the anisotropic mechanical properties of the cornea were incorporated into the model to describe the significant difference between its shear modulus(29.5 kPa)and tensile modulus(768.4 kPa).Additionally,a viscohyperelastic material model with a prolonged corneal relaxation time of 5.6 h was developed to capture the long-term deformation *** results show that corneal thickness reduction in OK is primarily due to out-of-plane shear deformation,influenced by the cornea’s low shear *** the extended corneal relaxation time is crucial for predicting long-term biomechanical *** computational model effectively captures long-term changes in central corneal thickness,potentially improving OK lens fitting accuracy.

关键词： orthokeratology computational biomechanical model long-term viscoelasticity myopia correction

From earthquake resistance structure to earthquake resilience city–urban seismic resilience assessment

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Earthquake Engineering and Engineering Vibration 2025年第1期24卷 1-13页

作者： Xie Lili Zhao Yonggang Wen Weiping Zhai Changhai Key lab.of Structures Dynamic Behaviour and Control of the Ministry of Education Harbin Institute of TechnologyHarbin 150090China Key lab.of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of TechnologyHarbin 150090China Institute of Engineering mechanics China Earthquake AdministrationHarbin 150080China

Earthquakes pose significant perils to the built environment in urban *** avert the calamitous aftermath of earthquakes,it is imperative to construct seismic resilient *** to the intricacy of the concept of urban seismic resilience(USR),its assessment is a large-scale system engineering *** assessment of USR should be based on the notion of urban seismic capacity(USC)assessment,which includes casualties,economic loss,and recovery time as *** loss is also included in the assessment of USR in addition to these *** assessment indicator system comprising five dimensions(building and lifeline infrastructure,environment,society,economy,and institution)and 20 indicators has been devised to quantify *** analytical hierarchy process(AHP)is utilized to compute the weights of the criteria,dimensions,and indicators in the urban seismic resilience assessment(USRA)indicator *** the necessary data for a city are obtainable,the seismic resilience of that city can be assessed using this *** illustrate the proposed methodology,a moderate-sized city in China was selected as a case *** assessment results indicate a high level of USR,suggesting that the city possesses strong capabilities to withstand and recover from potential future earthquakes.

关键词： urban seismic capacity urban seismic resilience assessment analytic hierarchy process functionality loss

XFEM modeling of hydraulic fracture in porous rocks with natural fractures

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Science China(Physics,mechanics & Astronomy) 2017年第8期60卷 45-59页

作者： Tao Wang ZhanLi Liu QingLei Zeng Yue Gao Zhuo Zhuang applied mechanics lab. School of Aerospace Engineering Tsinghua University

Hydraulic fracture （HF） in porous rocks is a complex multi-physics coupling process which involves fluid flow, diffusion and solid deformation. In this paper, the extended finite element method （XFEM） coupling with Biot theory is developed to study the HF in permeable rocks with natural fractures （NFs）. In the recent XFEM based computational HF models, the fluid flow in fractures and interstitials of the porous media are mostly solved separately, which brings difficulties in dealing with complex fracture morphology. In our new model the fluid flow is solved in a unified framework by considering the fractures as a kind of special porous media and introducing Poiseuille-type flow inside them instead of Darcy-type flow. The most advantage is that it is very convenient to deal with fluid flow inside the complex frac^xre network, which is important in shale gas extraction. The weak formulation for the new coupled model is derived based on virtual work principle, which includes the XFEM formulation for multiple fractures and fractures intersection in porous media and finite element formulation for the unified fluid flow. Then the plane strain Kristianovic-Geertsma-de Klerk （KGD） model and the fluid flow inside the fracture network are simulated to validate the accuracy and applicability of this method. The numerical results show that large injection rate, low rock permeability and isotropic in-situ stresses tend to lead to a more uniform and productive fracture network.

关键词： hydraulic fracture XFEM porous media fluid flow multi-physics coupling

ENRICHED GOAL-ORIENTED ERROR ESTIMATION applied TO FRACTURE mechanics PROBLEMS SOLVED BY XFEM

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Acta Mechanica Solida Sinica 2012年第4期25卷 393-403页

作者： Zhijia Lin Zhuo Zhuang Xiaochuan You Heng Wang Dandan Xu applied mechanics lab. School of AerospaceTsinghua UniversityBeijing 100084China

Based on the concept of constitutive relation error along with the residual of both origin and dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed in this paper. It leads to high quality local error bounds in the problem of fracture mechanics simulation with extended finite element method （XFEM）, which involves enrichment to solve a stress singularity in the crack. Since goal-oriented error estimation with enriched degrees of freedom gives us a chance to evaluate the XFEM simulation, the stress intensity factor calculated by two kinds of XFEM programs developed by ourselves and by commercial code ABAQUS are compared in this work. By comparing the reliability of the stress intensity factor calculation, the accuracy of two programs in different cases is evaluated and the source of error is discussed. A 2-dimensional XFEM example is given to illustrate the computational procedure.

关键词： goal-oriented error estimation extended finite element method fracture mechanics error bounds

Fundamental problem in optimizing the biaxial testing specimen

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Science China(Technological Sciences) 2019年第5期62卷 773-780页

作者： IMTIAZ Haroon FANG YaoPeng DU JianBin LIU Bin Department of Engineering mechanics Applied Mechanics Lab Tsinghua University

Most of the elements in structural design are subjected to the complex loading conditions that need to be predicted in advance for a reliable design. The failure prediction of these structural elements is based on the failure theories that employ the experimental data of the uniaxial, the biaxial and the shear tests. Among these tests, the biaxial testing is used to model the behavior of the structure loaded in more than one direction. In this study, we discover an interesting fact for the biaxial tension specimen that the thickness reduction of the measuring region cannot increase the stress to a high level. This behavior of the biaxial testing is different from the uniaxial testing where the thickness reduction of the measuring region always increases its stress to a higher level. Therefore, we further investigate the biaxial testing specimen via related fundamental problem, i.e., an axisymmetric plate with varying thickness under axisymmetric tension. We perform the shape optimization based on our analytical solution and the FEM results. For an infinite axisymmetric disk, the optimized design should include a low slope diverging section connecting the inner to outer region. On the contrary, the larger inner measuring region for finite axisymmetric disk would result in higher corresponding stress. These conclusions can be used as a guideline for the design of a biaxial testing specimen.

关键词： uniaxial testing biaxial testing axisymmetric disk problem optimization

Hierarchical model for strain generalized streaming potential induced by the canalicular fluid flow of an osteon

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Acta Mechanica Sinica 2015年第1期31卷 112-121页

作者： Xiao-Gang Wu Wei-Lun Yu Hai-Peng Cen Yan-Qin Wang Yuan Guo Wei-Yi Chen College of mechanics Shanxi Key Lab. of Material Strength & Structural Impact Taiyuan University of Technology Institute of applied mechanics and Biomedical Engineering Taiyuan University of Technology

A hierarchical model is developed to predict the streaming potential （SP） in the canaliculi of a loaded os teon. Canaliculi are assumed to run straight across the os teon annular cylinder wall, while disregarding the effect of lacuna. SP is generalized by the canalicular fluid flow. Ana lytical solutions are obtained for the canalicular fluid veloc ity, pressure, and SP. Results demonstrate that SP amplitude （SPA） is proportional to the pressure difference, strain am plitude, frequency, and strain rate amplitude. However, the key loading factor governing SP is the strain rate, which is a representative loading parameter under the specific phys iological state. Moreover, SPA is independent of canalicu lar length. This model links external loads to the canalicu lar fluid pressure, velocity, and SP, which can facilitate fur ther understanding of the mechanotransduction and electro mechanotransduction mechanisms of bones.

关键词： Canaliculi Streaming potential (SP) - Poroe-laticity Fluid flow

Damage evaluation of reinforced concrete frame based on a combined fiber beam model

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Science China(Physics,mechanics & Astronomy) 2014年第4期57卷 723-730页

作者： SHANG Bing LIU ZhanLi ZHUANG Zhuo applied mechanics lab School of Aerospace Tsinghua University

In order to analyze and simulate the impact collapse or seismic response of the reinforced concrete(RC)structures,a combined fiber beam model is proposed by dividing the cross section of RC beam into concrete fiber and steel *** stress-strain relationship of concrete fiber is based on a model proposed by concrete codes for concrete *** stress-strain behavior of steel fiber is based on a model suggested by *** constitutive models are implemented into a general finite element program ABAQUS through the user defined subroutines to provide effective computational tools for the inelastic analysis of RC frame *** fiber model proposed in this paper is validated by comparing with experiment data of the RC column under cyclical lateral *** damage evolution of a three-dimension frame subjected to impact loading is also investigated.

关键词： RC frame structure fiber model beam-column element dynamic response impact

On determination of the damping factor of linear viscoelastic materials using dynamic indentation:a theoretical study

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Science China(Physics,mechanics & Astronomy) 2011年第4期54卷 598-605页

作者： CAO YanPing JI XiangYing FENG XiQiao applied mechanics lab Department of Engineering Mechanics Tsinghua University Beijing 100084 China

In this study,we theoretically investigate the dynamic indentation for measuring the loss (damping) factor of a linear viscoelastic material from its indentation response.A rigid indenter with arbitrary tip profile is assumed to indent into a viscoelastic substrate with arbitrary *** perform a theoretical analysis and identify the conditions under which the loss factor of the material can be determined from the phase angle between the applied harmonic indentation load and the corresponding harmonic displacement,a directly measurable quantity in a dynamic indentation *** validate the conclusion drawn from our theoretical analysis,a series of numerical experiments are performed,including the spherical indentation of a soft layer with irregular surface morphology bonded to a rigid substrate,a conical indenter with tip defects indenting into a half-spherical particle,and the indentation of porous *** study may facilitate the use of the dynamic indentation technique to evaluate the damping properties of linear viscoelastic materials,including some advanced polymers and biological soft tissues.

关键词： dynamic indentation damping properties viscoelastic materials f'mite element simulation

STRAIN REGULARITY IN REINFORCERS OF SHORT-FIBER/ WHISKER REINFORCED COMPOSITE AND ITS APPLICATION

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Chinese Journal of Aeronautics 2000年第4期13卷 204-210页

作者：王迺鹏刘秋云刘晓宇 Stt. Key lab. Nonlinear mechanics Institute of Mechanics CAS Beijing 100080 China

Based on the study of strain distribution in short-fiber/whisker reinforced metal matrix composites, a deformation characteristic parameter λ is defined as the ratio of the root-mean-square strain of reinforcers to the macro-linear strain along the same direction. Quantitative relation between λ and microstructure parameters of the composite is obtained. As an example of applying and verifying λ, the stress-strain curve of ［AlBO］w/Al composite under tensile loading is predicted and favorably compared with experiments. By using λ, the stiffness modulus of the composite with arbitrary reinforcer orientation under any loading condition is predicted from the microstructure parameters of material.

关键词： short-fiber/whisker reinforced composite strain distribution stiffness prediction

CHARACTERIZATION OF THERMO-MECHANICAL FATIGUE PROPERTIES FOR PARTICULATE REINFORCED COMPOSITES

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 534-541页

作者： H.J.Shi H.X.Mei R.Guo G.Mesmacque Key lab. of Failure mechanics Department of Engineering Mechanics Tsinghua University Beijing 100084 ChinaKey Lab. of Failure Mechanics Department of Engineering Mechanics Tsinghua University Beijing 100084 ChinaKunming University of Science and Technology Kunming 650093 ChinaLab. of Mechanics of Lille University of Lille 1 Villeneuve d'Ascq 59500 France

A Voronoi cell dement, formulated with creep, thermal and plastic strain was applied for investigation of thermo-mechanical fatigue behavior for particulate reinforced composites. Under the in-phase fatigue loading, the maximum of tensile deformation at the maximum given loading are larger than that at the same maximum under the out-phase fatigue. The stiffness decreases nonlinearly with the increasing of the phase angle, which results in increasing of the area of fatigue loop curve and the decrease in fatigue life. The spatially centralizing of inclusions results in decreasing of the plastic strain amplitude and the area of fatigue loop curve, which will also reduce the consumption of single-circle plastic strain energy and prolong the fatigue life.

关键词： thermo-mechanical fatigue particulate reinforced composites,voronoi element phase angle