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Experimental studies on removal of carbon dioxide by aqueous ammonia fine spray

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Science China(Technological Sciences) 2010年第1期53卷 117-122页

作者： NIU ZhenQi,GUO YinCheng & LIN WenYi department of engineering mechanics,School of aerospace,Tsinghua University,Beijing 100084,China department of engineering mechanics School of Aerospace Tsinghua University Beijing China

Experimental studies on carbon dioxide capture in a spray scrubber were carried *** spray of aqueous ammonia was used as CO2 *** of different operating and design parameters on CO2 removal efficiency including concentration of aqueous ammonia,liquid flow rate,total gas flow rate,initial temperature and concentration of carbon dioxide were investigated.

关键词： carbon dioxide aqueous ammonia absorption removal efficiency fine spray

THE EIGENVALUE PROBLEM AND SAINT-VENANT DECAY RATE FOR A NONHOMOGENEOUS SEMI-INFINITE STRIP

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Acta Mechanica Solida Sinica 2014年第6期27卷 588-596页

作者： Qing Yang Bailin Zheng Kai Zhang Jianxin Zhu School of aerospace engineering and Applied mechanics Tongji University

The eigenvalue problem about a nonhomogeneous semi-infinite strip is investigated using the methodology proposed by Papkovich and Fadle for homogeneous plane problems. Two types of nonhomogeneity are considered：（i） the elastic modulus varying with the thickness coor- dinate x exponentially, （ii） it varying with the length coordinate y exponentially. The eigenvalues for the two cases are obtained numerically in plane strain and plane stress states, respectively. By considering the smallest positive eigenvalue, tile Saint-Venant Decay rates are estimated, which indicates material nonhomogeneity has a signifcant influence on the Saint-Venant end effect.

关键词： eigenvalue Saint-Venant decay rate nonhomogeneous semi-infinite strip

Archimedes Spiral Cracks Developed in a Nanofilm/Substrate System

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Chinese Physics Letters 2013年第3期30卷 123-126页

作者： WU Dan YIN Ya-Jun XIE Hui-Min DAI Fu-Long AML Department of Mechanics EngineeringSchool of AerospaceTsinghua UniversityBeijing 100084

Perfect Archimedes spiral cracks at micrometer scales are found in a colloid film of several hundred nanometers in thickness coated on a glass *** explain the formation of this kind of spiral crack,the relation between the geometrical properties of the Archimedes spiral and the growth kinematics of the spiral cracks are ***,the initiation and propagation of the spiral cracks are speculated upon logically from the specific material system based on sufficient *** addition,we introduce a new cracking phenomenon and provide an insight into the new mechanism for crack propagation in soft material nano films coated on stiff substrates.

关键词： crack cracking film

Tuning of non-uniform switch toughening in ferroelectric composites by an electric field

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维普期刊数据库

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Acta Mechanica Sinica 2016年第5期32卷 866-880页

作者： Xiaodong Xia Zheng Zhong School of aerospace engineering and Applied mechanics Tongji University

This paper deals with a mode III interfacial crack subject to anti-plane stress and in-plane electric fields. The analysis concentrates on the tuning of fracture toughness from non-uniform ferroelectric-ferroelastic domain switching by an electric field. The electric loading changes the size of the asymmetric switching zone. Employing the weight function method, we obtain the electrically-dependent switch toughening for stationary and quasi-static growing interfacial cracks, respectively. Multi-domain solutions are derived for non-poled and fully-poled ferroelectric composites. Numerical results are presented on the electric field tuning of the critical applied stress intensity factor. The research provides ways to optimize fracture properties of ferroelectric composites by altering the electric field.

关键词： Interfacial crack Electric field tuning Domain switching Ferroelectric-ferroelastic Toughening

Numerical simulation of two-dimensional granular shearing flows and the friction force of a moving slab on the granular media

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Chinese Physics B 2011年第2期20卷 326-331页

作者：蔡庆东陈十一盛晓伟 LTCS and CAPT Department of Mechanics and Aerospace EngineeringCollege of EngineeringPeking University department of Mechanical engineering The Johns Hopkins University

This paper studies some interesting features of two-dimensional granular shearing flow by using molecular dynamic approach for a specific granular system. The obtained results show that the probability distribution function of velocities of particles is Gaussian at the central part, but diverts from Gaussian distribution nearby the wall. The macroscopic stress along the vertical direction has large fluctuation around a constant value, the non-zero average velocity occurs mainly near the moving wall, which forms a shearing zone.. In the shearing movement, the volume of the granular material behaves in a random manner. The equivalent fl＇iction coefficient between moving slab and granular material correlates with the moving speed at low velocity, and approaches constant as the velocity is large enough.

关键词： granular shearing flow friction molecular dynamics modeling

Time-delay identification for vibration systems with multiple feedback

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Acta Mechanica Sinica 2016年第6期32卷 1138-1148页

作者： Yi-Qiang Sun Meng-Shi Jin Han-Wen Song Jian Xu School of aerospace engineering and Applied mechanics Tongji University

An approach for time-delay identification is proposed in multiple-degree-of-freedom (MDOF) linear systems with multiple feedback. The applicability of the approach is discussed in detail. Based on the characteristics of frequency domain in feedback controlled system with multiple time-delays, this paper proposes a time-delay identification approach, which is based on the pseudo impedance function of reference point. Treating feedback time-delays as the 'frequencies' of the oscillation curve, the time-delays can be obtained from the 'frequencies' of the curve. Numerical simulation is conducted to validate the proposed approach. The application scope of the approach is discussed with regard to different forms of feedback.

关键词： Multiple time-delays Parameter identification Feedback Frequency response functions

Method of reverberation ray matrix for static analysis of planar framed structures composed of anisotropic Timoshenko beam members

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Applied Mathematics and mechanics(English Edition) 2015年第2期36卷 233-242页

作者： Jiao ZHANG Guohua NIE School of aerospace engineering and Applied mechanics Tongji University

Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for static analysis of such *** the MRRM for dynamic analysis, amplitudes of arriving and departing waves for joints are chosen as unknown quantities. However, for the present case of static analysis, displacements and rotational angles at the ends of each beam member are directly considered as unknown quantities. The expressions for stiffness matrices for anisotropic beam members are developed. A corresponding reverberation matrix is derived analytically for exact and unified determination on the displacements and internal forces at both ends of each member and arbitrary cross sectional locations in the structure. Numerical examples are given and compared with the finite element method（FEM） results to validate the present model. The characteristic parameter analysis is performed to demonstrate accuracy of the present model with the T beam theory in contrast with errors in the usual model based on the Euler-Bernoulli（EB） beam theory. The resulting reverberation matrix can be used for exact calculation of anisotropic framed structures as well as for parameter analysis of geometrical and material properties of the framed structures.

关键词： planar framed structure anisotropic Timenshenko(T) beam stiffness matrix method of reverberation ray matrix(MRRM) static analysis

Experimental study on the interfacial delamination in a thermal barrier coating system at elevated temperatures

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2010年第10期11卷 794-803页

作者： Peng-fei ZHAO Fu-lin SHANG department of engineering mechanics School of Aerospace Xi 'an Jiaotong University Xi 'an 710049 China

The failure mode and adhesion of thermal barrier coating (TBC) 8YSZ (ZrO2+8% (w/w) Y2O3) deposited on NiCoCrAlTaY bond coat by atmospheric plasma spraying were investigated. A grooved modified three-point bending specimen that can generate a single interface crack to facilitate the control of crack growth was adopted for testing, which was conducted at the ambient temperature of 100 °C. The morphology and composition of fractured surfaces were examined by means of a scanning electron microscopy (SEM) and an energy disperse spectroscopy (EDS). Images and spectrum show that cracks are initiated and propagated exclusively within YSZ layer adjacent to top/bond coat interface. The load-displacement curves obtained exhibit similar shapes that indicate two distinct stages in crack initiation and stable crack growth. Finite element analyses were performed to extract the adhesion strength of the TBCs. The delamination toughness of the plasma-sprayed 8YSZ coatings at 100 °C, in terms of critical strain energy release rate Gc, can be reliably obtained from an analytical solution.

关键词： Thermal barrier coating (TBC) Three-point bending test Finite element analysis Delamination toughness

SIF-based fracture criterion for interface cracks

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Acta Mechanica Sinica 2016年第3期32卷 491-496页

作者： Xing Ji School of aerospace engineering and Applied mechanics Tongji University

The complex stress intensity factor K governing the stress field of an interface crack tip may be split into two parts, i.e.,■ and s^（-iε）, so that K = ■ s^（-iε）, s is a characteristic length and ε is the oscillatory index. ■ has the same dimension as the classical stress intensity factor and characterizes the interface crack tip field. That means a criterion for interface cracks may be formulated directly with■, as Irwin（ASME J. Appl. Mech. 24：361–364, 1957） did in 1957 for the classical fracture mechanics. Then, for an interface crack,it is demonstrated that the quasi Mode I and Mode II tip fields can be defined and distinguished from the coupled mode tip fields. Built upon SIF-based fracture criteria for quasi Mode I and Mode II, the stress intensity factor（SIF）-based fracture criterion for mixed mode interface cracks is proposed and validated against existing experimental results.

关键词： Interface crack Stress singularity Fracture criterion Stress intensity factor