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The nonlocal solution of two parallel cracks in functionally graded materials subjected to harmonic anti-plane shear waves

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Acta Mechanica Sinica 2007年第4期23卷 427-435页

作者： Jun Liang Shiping Wu Shanyi Du center for composite materials and Structure,Harbin Institute of Technology,Harbin 150001,China center for composite materials and Structure Harbin Institute of Technology Harbin China

In this paper, the dynamic interaction of two parallel cracks in functionally graded materials （FGMs） is investigated by means of the non-local theory. To make the analysis tractable, the shear modulus and the material density are assumed to vary exponentially with the coordinate vertical to the crack. To reduce mathematical difficulties, a one-dimensional non-local kernel is used instead of a twodimensional one for the dynamic problem to obtain stress fields near the crack tips. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations, in which the unknown variables are the jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displacements across the crack surfaces are expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularity is present at the crack tips. The non-local elastic solutions yield a finite hoop stress at the crack tips. The present result provides theoretical references helpful for evaluating relevant strength and preventing material failure of FGMs with initial cracks. The magnitude of the finite stress field depends on relevant parameters, such as the crack length, the distance between two parallel cracks, the parameter describing the FGMs, the frequency of the incident waves and the lattice parameter of materials.

关键词： Crack The non-local theory Stress waves Functionally graded materials

Mesh-dependence of Material with Softening Behavior

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Chinese Journal of Aeronautics 2010年第1期23卷 46-53页

作者： Fu Li,Du Xingwen center for composite materials,Harbin Institute of Technology,Harbin 150001,China center for composite materials Harbin Institute of Technology Harbin 150001 China

The issue of mesh-dependence emerges when the conventional continuum damage model is applied to handling the softening behavior. In order to circumvent the mesh-dependence, the non-local theory is introduced into the conventional damage model and the finite element formulas are derived for two-dimensional gradient-enhanced damage model. A new element is proposed in which the basic unknown quantities are displacement, non-local equivalent strain and the gradient of non-local equivalent strain. The element and constitutive equation proposed in this article are added to the finite element software ABAQUS through user subroutine UEL. Numerical results show that the gradient-enhanced damage model can eliminate the mesh-dependence and is effective for dealing with the issue of softening behavior.

关键词： non-local theory gradient dependence softening behavior mesh-dependence Hermitian element finite element method

Di-PEGylated insulin:A long-acting insulin conjugate with superior safety in reducing hypoglycemic events

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Acta Pharmaceutica Sinica B 2024年第6期14卷 2761-2772页

作者： Zhipeng Zeng Runcheng Tan Shi Chen Haolin Chen Zhijia Liu Lixin Liu Mingqiang Li Yongming Chen Laboratory of Biomaterials and Translational Medicine Center for NanomedicineThe Third Affiliated HospitalSun Yat-sen UniversityGuangzhou 510630China School of materials Science and Engineering Center of Functional BiomaterialsKey Laboratory of Polymeric Composite Materials and Functional Materials of Ministry of EducationSun Yat-sen UniversityGuangzhou 510275China

Although the discovery of insulin 100 years ago revolutionized the treatment of diabetes,its therapeutic potential is compromised by its short half-life and narrow therapeutic index.Current long-acting insulin analogs,such as insulin-polymer conjugates,are mainly used to improve pharmacokinetics by reducing renal clearance.However,these conjugates are synthesized without sacrificing the bioactivity of insulin,thus retaining the narrow therapeutic index of native insulin,and exceeding the efficacious dose still leads to hypoglycemia.Here,we report a kind of di-PEGylated insulin that can simultaneously reduce renal clearance and receptor-mediated clearance.By impairing the binding affinity to the receptor and the activation of the receptor,di-PEGylated insulin not only further prolongs the half-life of insulin compared to classical mono-PEGylated insulin but most importantly,increases its maximum tolerated dose 10-fold.The target of long-term glycemic management in vivo has been achieved through improved pharmacokinetics and a high dose.This work represents an essential step towards long-acting insulin medication with superior safety in reducing hypoglycemic events.

关键词： Diabetes Insulin Therapeutic index Hypoglycemia PEGylation Receptor-mediated clearance Half-life Diabetic nephropathy

Valence electron structure and bonding features of RuB2 and OSB2: The empirical electron theory calculations

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Science China(Technological Sciences) 2010年第7期53卷 1877-1885页

作者： LUO XiaoGuang, LI JinPing, HU Ping & DONG ShanLiang center for composite materials, Harbin Institute of Technology, Harbin 150001, China center for composite materials Harbin Institute of Technology Harbin China

The valence electron structure (VES) of RuB2 and OsB2 were calculated by the empirical electron theory (EET) of solids and molecules and compared with the results derived from the first-principles calculations. The distributions of covalent electrons in different bonds indicate that B-B and B-Me have remarkably covalent bonding characters. Lattice electrons cruising around Me-Me layers are found to have great influences on electronic conductivity and high temperature plasticity. The ultra-high values of elastic constant Cn in the two compounds originate from close-packed covalent bonding along the c axis. Uneven bond strengths and distributions of covalent bonds, especially for B-Afe bonds, yield significant anisotropy. Low ratios of lattice electrons to covalent electrons suggest the intrinsic embrittlement in crystals. The fact that the calculated cohesive energies well agree with experimental results demonstrates the good suitability of the EET calculations in estimating cohesive energy for transition-metal borides.

关键词： empirical electron theory (EET) of solid and molecules valence electron structure (VES) cohesive energy anisotropy diborides of ruthenium and osmium (RuB2 and OsB2)

Valence electron structure and properties of the ZrO_2

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Science China(Technological Sciences) 2008年第11期51卷 1858-1866页

作者： LI JinPing, MENG SongHe, HAN JieCai & ZHANG XingHong center for composite materials, Harbin Institute of Technology, Harbin 150001, China center for composite materials Harbin Institute of Technology Harbin China

To reveal the properties of ZrO2 at the atom and electron levels, the valence elec- tron structures of three ZrO2 phases were analyzed on the basis of the empirical electron theory of solids and molecules. The results showed that the hybridization levels of Zr and O atoms in the m-ZrO2 were the same as those in the t-ZrO2, while those in the c-ZrO2 rose markedly. The electron numbers and bond energies on the strongest covalent bonds in the m-ZrO2 phase were the greatest, the values were 0.901106 and 157.5933 kJ/mol, respectively. Those in the t-ZrO2 phase took second place, which were 0.722182 and 123.9304 kJ/mol, and those in the c-ZrO2 phase were the smallest, which were 0.469323 and 79.0289 kJ/mol. According to the product of the bond energy on the strongest covalent bond and equivalent bond number (this value reflected the crystal cohesive energy), the order from the greatness to smallness was the c-ZrO2> t-ZrO2 > m-ZrO2. This showed that the m-phase bonds were the tightest, their energy was the smallest, the crystal cohe- sive energy of the m-phase was the largest, and the m-phase existed most stably at room temperature. So it must need energy or higher temperature to take apart the stronger covalent bonds to form a new phase.

关键词： ZrO2 empirical electron theory bond length difference valence electron structure properties

Valence electron structure and properties of stabilized ZrO_2

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Science China(Technological Sciences) 2008年第7期51卷 1008-1016页

作者： LI JinPing, HAN JieCai, MENG SongHe & ZHANG XingHong center for composite materials, Harbin Institute of Technology, Harbin 150001, China center for composite materials Harbin Institute of Technology Harbin China

To reveal the properties of stabilizers in ZrO2 on nanoscopic levels, the valence electron structures of four stable ZrO2 phases and c-ZrO2 were analyzed on the basis of the empirical electron theory of solids and molecules. The results showed that the hybridization levels of Zr atoms in c-ZrO2 doped with Ca and Mg dropped from B17 to B13, the hybridization levels of Zr atoms in c-ZrO2 doped with Y and Ce dropped from B17 to B15, and that the four stabilizing atoms all made the hybridization levels of O atoms drop from level 4 to level 2. The numbers of covalent electrons in the strongest covalent bond in the descending order are c-ZrO2>Zr0.82Ce0.18O2> Zr0.82Y0.18O1.91>Zr0.82Mg0.18O1.82>Zr0.82Ca0.18O1.82. The bond energies of the strongest covalent bond and the melting points of the solid solutions in the descending order are Zr0.82Ce0.18O2> c-ZrO2>Zr0.82Y0.18O1.91>Zr0.82Mg0.18O1.82>Zr0.82Ca0.18O1.82. The percent-ages of the total number of covalent electrons in the descending order are c-ZrO2>Zr0.82Y0.18O1.91> Zr0.82Ce0.18O2>Zr0.82Mg0.18O1.82> Zr0.82Ca0.18O1.82. From the above analysis, it can be concluded that the stabilizing degrees of the four stabilizers in the descending order are CaO> MgO>Y2O3>CeO2.

关键词： c-ZrO2 empirical electron theory bond length difference valence electron structure properties

Effects of heat treatment on mechanical properties of ODS nickel-based superalloy sheets prepared by EB-PVD

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Rare Metals 2011年第1期30卷 76-80页

作者： CHEN Song QU Shoujiang LIANG Jun HAN Jiecai center for composite materials Harbin Institute of TechnologyHarbin 150001China

A Y2O3 dispersion strengthened nickel-based superalloy sheet（0.15 mm thick） was prepared by electron beam physical vapor deposition（EB-PVD） technology.Different heat treatments were used to improve the mechanical properties of the alloy sheet.Differential thermal analysis（DTA） was used to examine the thermal stability of the as-deposited sheet.Element contents,phase composition and microstructure investigations on as-deposited and heat treated specimens were performed by X-ray fluorescence spectrometer（XRF）,X-ray diffraction（XRD） and scanning electron microscopy（SEM）.Tensile tests were conducted at room temperature on specimens as-deposited and heat treated.The results show that the as-deposited sheet is composed of equiaxed grains on the substrate side and columnar grains on the evaporation side.The as-deposited sheet shows poor ductility due to micropores between columnar grains.The strength and ductility can be improved effectively by annealing at 800°C for 3 h.For samples treated at 1100°C,the strength drops down due to the precipitates of Y3Al5O12（YAG）.

关键词： superalloys nickel alloys mechanical properties heat treatment electron beams physical vapor deposition

Valence electron structure of the(ZrTi)B_2 solid solutions calculated by the three models

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Science China(Technological Sciences) 2009年第5期52卷 1195-1201页

作者： LI JinPing,HAN JieCai,MENG SongHe & WANG BaoLin center for composite materials,Harbin Institute of Technology,Harbin150001,China center for composite materials Harbin Institute of Technology Harbin China

The Zr-rich(Zr0.8Ti0.2)B2 and the Ti-rich(Ti0.8Zr0.2)B2 solid solutions are formed when TiB2 and ZrB2 are hot-pressed.To forecast the properties of the two solid solutions,their valence electron structure was analyzed based on the empirical electron theory(EET) of solids and molecules.We used three different models,the average atom model,the average cell model and the real cell model,and compared with the calculation results from the three models.In the real cell model,the lattice constants of the solid solu-tions were supposed to be changed or unchanged.The results showed that different models could only result in slight change in the hybridization levels of the metal atoms in the two solid solutions and little difference between the calculation values.However,they can not change the variant trend of the va-lence electron structure nor the properties of the solid solutions.Thus,the three models and the methods are appropriate and the calculation results are reasonable and consistent.

关键词： (ZrTi)B2 solid solutions empirical electron theory the calculation models

Three-dimensional Cure Simulation of Stiffened Thermosetting composite Panels

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Journal of materials Science & Technology 2010年第5期26卷 467-471页

作者： Guangquan Yue,Boming Zhang ,Fuhong Dai and Shanyi Du center for composite materials,Harbin Institute of Technology,Harbin 150080,China center for composite materials Harbin Institute of Technology Harbin 150080 China

Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensional cure simulation of T-shape stiffened thermosetting composite panels was presented.Flexible tools and locating tools were considered in the cure simulation.Temperature distribution in the composites was predicted as a function of the autoclave temperature history.A nonlinear transient heat transfer finite element model was developed to simulate the curing process of stiffened thermosetting composite panels.And a simulation example was presented to demonstrate the use of the present finite element procedure for analyzing composite curing process.The glass/polyester structure was investigated to provide insight into the nonuniform cure process and the effect of flexible tools and locating tools on temperature distribution.Temperature gradient in the intersection between the skin and the flange was shown to be strongly dependent on the structure of the flexible tools and the thickness of the skin.

关键词： Thermosetting composite Stiffened panels Co-curing Numerical simulation