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Revealing and predicting the long-term biomechanical response of orthokeratology by developing a patient-specific computational model

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 156-168页

作者： Yifeng Li Zhuoran Yang Ziming Yan Huibin Shi zhanli liu Kaijie Wang Department of Engineering Mechanics School of Aerospace Engineering Tsinghua University Beijing Tongren Eye Center Beijing Tongren Hospital Capital Medical University Beijing Ophthalmology & Visual Sciences Key Lab

Orthokeratology(OK) is widely used for effective myopia correction and control. However, the incomplete understanding of its biomechanical mechanisms makes OK lens fitting rely heavily on clinician judgment, complicating accurate predictions of treatment outcomes. In this paper, we performed clinical experiments and numerical analysis to study corneal deformation modes and long-term changes in central corneal thickness. Clinical experiments were conducted on 194 Chinese myopic patients under OK treatment for 3 months. Based on the experimental data, a patient-specific computational biomechanical model for OK was established and validated. Specifically, 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 response. The results show that corneal thickness reduction in OK is primarily due to out-of-plane shear deformation,influenced by the cornea's low shear resistance. Modeling the extended corneal relaxation time is crucial for predicting long-term biomechanical responses. The 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

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A Crystal Plasticity Model with Irradiation Effect for the Mechanical Behavior of FCC Metals

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Acta Mechanica Solida Sinica 2019年第6期32卷 675-687页

作者： Jnnfeng Nie Yunpeng liu Pandong Lin Qihao Xie zhanli liu Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Minis try of EducationTsinghua UniversityBeijing 100084China Applied Mechanics Lab. School of Aerospace EngineeringTsinghua UniversityBeijing 100084China Data Science and Information Technology Research Center Tsinghua-Berkeley Shenzhen InstituteShenzhen 518055China

In this paper,a crystal plasticity model considering the irradiation effect based on the thermal activation theory is *** evolutions of screw dislocations,edge dislocations,and stacking fault tetrahedrals(SFTs)(induced by irradiation)are included into the *** interactions between dislocations and irradiation-induced SFTs are also *** constitutive model is numerically implemented on the ABAQUS platform through UMAT subroutine and applied to study the irradiation effect on the mechanical behavior of pure *** mechanical properties of single and polycrystalline copper are studied,and the simulation results show that the constitutive model can properly predict the mechanical behavior of irradiated pure *** for polycrystalline copper,the simulation results are in good agreement with the experimental data.

关键词： Crystal plasticity Irradiation effect Uniaxial tension Dislocation FCC crystal

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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

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On the material constants measurement method of a fluid-saturated transversely isotropic poroelastic medium

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Science China(Physics,Mechanics & Astronomy) 2019年第1期62卷 69-75页

作者： Yue Gao zhanli liu Zhuo Zhuang Keh-Chih Hwang AML Department of Engineering Mechanics Tsinghua University Center for Mechanics and Materials Tsinghua University

The fluid-saturated transversely isotropic poroelastic medium could be widely found in nature, e.g., the sedimentary rocks underground. To determine the eight independent material constants for the transversely isotropic poroelastic medium, a series of tests are discussed. Two undrained tests and one drained test are suggested as a set of tests of the least amount. For the verification purpose, two additional drained tests are also introduced as an option. The atmospheric dried test is discussed as a replacement of the traditional infiltrated drained test to save the time waiting for an equilibrium state. Some microscopic material constants, i.e.,the unjacketed bulk coefficients, the porosity, and the compressibility of porous fluid, are measurable but unnecessary to determine the independent material constants of a poroelastic medium.

关键词： poroelastic constitutive model material constants measurement transversely isotropic medium

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Theoretical aspects of selecting repeated unit cell model in micromechanical analysis using displacement-based finite element method

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Chinese Journal of Aeronautics 2017年第4期30卷 1417-1426页

作者： Lijun GAO Chengyu WANG zhanli liu Zhuo ZHUANG Department of Engineering Mechanics School of Aerospace Engineering Tsinghua University Beo'ing 100084 China

Repeated Unit Cell（RUC）is a useful tool in micromechanical analysis of composites using Displacement-based Finite Element（DFE）method,and merely applying Periodic Displacement Boundary Conditions（PDBCs）to RUC is almost a standard practice to conduct such *** basic questions arising from this practice are whether Periodic Traction Boundary Conditions（PTBCs,also known as traction continuity conditions）are guaranteed and whether the solution is independent of selection of *** paper presents the theoretical aspects to tackle these questions,which unify the strong form,weak form and DFE method of the micromechanical problem ***,the solution’s independence of selection of RUCs is dealt with on the strong form side,PTBCs are derived from the weak form as natural boundary conditions,and the validity of merely applying PDBCs in micromechanical Finite Element（FE）analysis is proved by referring to its intrinsic connection to the strong form and weak *** points in the theoretical aspects are demonstrated by illustrative examples,and the merits of setting micromechanical FE analysis under the background of a clear theoretical framework are highlighted in the efficient selection of RUCs for Uni Directional（UD）fiber-reinforced composites.

关键词： Finite element method Micromechanics of composites Periodic boundary condition Repeated unit cell Theoretical aspect Traction continuity

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Recent advances in the extended finite element method (XFEM) and isogeometric analysis (IGA)

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Science China(Physics,Mechanics & Astronomy) 2016年第12期59卷 80-81页

作者： DanDan Xu zhanli liu Zhuo Zhuang School of Aerospace Engineering Tsinghua University

The finite element method （FEM） is one of the most popular and efficient methods for computational modeling in scien- tific research and engineering . To expand its application to more complex problems, lots of new ... 详细信息

关键词： XFEM IGA Recent advances in the extended finite element method and isogeometric analysis

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Study on interaction between induced and natural fractures by extended finite element method

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Science China(Physics,Mechanics & Astronomy) 2017年第2期60卷 24-37页

作者： DanDan Xu zhanli liu Zhuo Zhuang QingLei Zeng Tao Wang School of Aerospace Engineering Tsinghua University Beijing 100084 China

Fracking is one of the kernel technologies in the remarkable shale gas revolution. The extended finite element method is used in this paper to numerically investigate the interaction between hydraulic and natural fractures, which is an important issue of the enigmatic fracture network formation in fracking. The criteria which control the opening of natural fracture and crossing of hydraulic fracture are tentatively presented. Influence factors on the interaction process are systematically analyzed, which include the approach angle, anisotropy of in-situ stress and fluid pressure profile.

关键词： hydraulic fracturing natural fracture interaction criterion fluid pressure extended finite element method

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Modeling stationary and moving cracks in shells by X-FEM with CB shell elements

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Science China(Technological Sciences) 2014年第7期57卷 1276-1284页

作者： ZENG QingLei liu zhanli XU DanDan ZHUANG Zhuo School of Aerospace Tsinghua University

The continuum-based(CB)shell theory is combined with the extended finite element method(X-FEM)in this paper to model crack propagation in shells under static and dynamic *** jump function and asymptotic crack tip solution are adopted for describing the discontinuity and singularity of the crack in *** set method(LSM)is used to represent the crack surface and define the enriched shape *** intensity factors(SIFs)are calculated by the displacement interpolation technique to prove the capability of the method and the maximum strain is applied for the fracture ***,an efficient integration scheme for the CB shell element with cracks is proposed.

关键词： CB shell element X-FEM level set method crack propagation

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Finite element analysis for inclined wellbore stability of transversely iso-tropic rock with HMCD coupling based on weak plane strength criterion

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Science China(Technological Sciences) 2017年第4期60卷 624-637页

作者： WANG YongLiang ZHUANG Zhuo liu zhanli YANG HengLin LI ChenFeng Applied Mechanics Laboratory School of Aerospace Engineering Tsinghua University Zienkiewicz Centre for Computational Engineering & Energy Safety Research Institute College of Engineering Swansea University Drilling Research Institute China National Petroleum Corporation

The finite element analysis(FEA) technology by hydraulic-mechanical-chemical-damage(HMCD) coupling is proposed in this paper for inclined wellbore stability analysis of water-sensitive and laminated rock, developed basing on the recently established FEA technology for transversely isotropic rock with hydraulic-mechanical-damage(HMD) coupling. The chemical activity of the drilling fluid is considered as phenomenological hydration behavior, the moisture content and parameters of rock considering hydration could be determined with time. The finite element(FE) solutions of numerical wellbore model considering the chemical activity of drilling fluid, damage tensor calculation and weak plane strength criterion for transversely isotropic rock are developed for researching the wellbore failure characteristics and computing the time-dependent collapse and fracture pressure of laminated rock as shale reservoirs. A three-dimensional FE model and elastic solid deformation and seepage flow coupled equations are developed, and the damage tensor calculation technology for transversely isotropic rock are realized by introducing effect of the hydration and the stress state under the current load. The proposed method utilizing weak plane strength criterion fully reflects the strength parameters in rock matrix and weak plane. To the end, an effective and reliable numerically three-step FEA strategy is well established for wellbore stability analysis. Numerical examples are given to show that the proposed method can establish efficient and applicable FE model and be suitable for analyzing the timedependsolutions of pore pressure and stresses, and the evolution region considering the hydration surrounding wellbore,furthermore to compute the collapse cycling time and the safe mud weight for collapse and fracture pressure of transversely isotropic rock.

关键词： finite element analysis wellbore stability transversely isotropic rock hydraulic-mechanical-chemical-damage coupling weak plane strength criterion

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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

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