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2015 Vol. 36, No. 1
Published: 2014-02-28
1
ELECTROMECHANICAL INSTABILITY OF INFLATED ELECTRIO-ACTIVE POLYMER SPERICAL SHELLS
Electromechanical instability of asymmetric deformations of an incompressible electro-active polymer spherical shell, subjected to an internal pressure and an electrostatic field, is examined within the framework of the finite deformation theory of continuum mechanics. The deformation curves and the distribution of stresses of the shell under different electric fields are provided. When the inflation pressure is larger than the critical value, a thin-walled shell whose thickness is smaller than the critical thickness may undergo an unstable asymmetric deformation. The critical thickness and the critical pressure for the shell to take an instability deformation are given. The effects of the electrostatic field on the critical values and the distribution of stresses are discussed.
2015 Vol. 36 (1): 1-7 [
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251
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8
The fuzzy variational principle of complex natural frequency
2015 Vol. 36 (1): 8-19 [
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191
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20
THE NUMERICAL ANALYSIS OF CRACK SHIELDING EFFECT INFLUENCED BY THE HYSTERESIS OF TRANSFORMATION
In this paper, the crack shielding effect influenced by the transformation of austenite, is studied numerically in the austenite-martensite dual material. The transformation of austenite particles embeded in the crack materialis is induced by the strain ahead of the crack tip. Considering the singular distribution of stress-strain field ahead of the crack tip and the strain induced transformation, in this study, through embedding a transformed particles in the different locations of the crack-tip area, the transformation hysteresis problem can be transferred to a problem of transformed particle location. Based on the volume expansion effect of austenite-martensite transformation, a plane stress crack problem is investigated and the influence of the location of transformed particle on the crack shielding effect is obtained. The results show that the location of transformed particles at the crack-tip area has a great influence on the crack shielding effect, the shielding effect is occurred out of the sector 86°ahead of the crack tip, which is different with the result of McMeeking and Evans based on the analysis theoretically.
2015 Vol. 36 (1): 20-27 [
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316
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28
Anti-controlling Period-doubling Bifurcation of an Inertial Impact Shaker System
In the premise of no change of periodic solutions of the original system and with consideration of the difficulties that given by the implicit Poincaré map of the impact shaker system and the classical critical criterion of mapping period-doubling bifurcation described by the properties of eigenvalues, the method of anti-control of period-doubling bifurcation of an inertial impact shaker system is proposed on basis of an explicit critical criterion without using eigenvalues calculation. Firstly, the linear feedback control is used to deduce the Poincaré map of close-loop system, and the period-doubling bifurcation explicit critical criterion without using eigenvalues calculation is applied to obtain the controlling parameters area. Then, the stability of the period-doubling bifurcation is further analyzed by utilizing the center manifold and normal formal theory. The ultimate numerical experiments verify that the stable period-doubling bifurcation solutions can be generated at an arbitrary specified parameters point by controlling.
2015 Vol. 36 (1): 28-34 [
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247
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35
Study on discrete model for evaluating failure process of concrete member
Rigid body-spring model was one of discrete analysis models, which could reflect the realistic cracking pattern of continuum material during the discontinuous process from cracking to failure. This paper introduced and programmed the rigid body-spring model for studying the cracking and failure behavior of concrete member, especially realistic crack pattern of concrete member from cracking to failure, based on the summary of existing research result. The division of rigid body element, characteristics of spring element （the constitutive law of concrete applied to spring element）, assembly of rigid body and spring element, the constitutive law of rebar, and the interaction between rebar and concrete were determined firstly. After that, the programming on cracking and failure behavior of concrete member using rigid body-spring model was implemented and verified by a shear-failed RC member. The result demonstrated that the programming could exactly reflect the realistic crack pattern of the member from cracking to failure.
2015 Vol. 36 (1): 35-41 [
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239
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42
THE SCALED BOUNDARY FINITE ELEMENT SECOND ORDER SENSITIVITY DESING AND FRACTURE MECHANICS ANALYSIS
The scaled boundary finite element method is a semi-analytical method that only needs to mesh on the boundary without fundamental solution, which makes it powerful to deal with singular and unbounded problem. This paper aims to propose a second order sensitivity analysis method for the scaled boundary finite element method, which can calculate the second order gradients of the responses with respect to the parameters accurately and efficiently. An improved first order sensitivity analysis method is presented through establishing a new Hamilton eigenproblem equation with only right eigenvectors. The second order Hamilton eigenproblem equation is constructed and the semi-analytical sensitivities of displacements and stresses are further obtained by a series of differential equation. The proposed method is then applied to the shape sensitivity analysis of linear cracked structures and corresponding uncertainty propagation analysis. Finally, two numerical examples are investigated to demonstrate the validity of the proposed method.
2015 Vol. 36 (1): 42-54 [
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277
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55
A Model for Failure Prediction of A Composite-Metal-Weld Joint
A macro-micro model was developed for the prediction of the strength and failure modes of Composite-Metal-Weld (Comeld) joints subjected to static tensile loading. A suitable representative volume element (RVE) was selected according to the distribution of protrusions. The unit cell model of the protrusion layer was established and a unified periodical boundary condition was applied to the model. The average stiffness of the protrusion layer was obtained by finite element method (FEM). The strength and failure modes of the unit cell were analyzed based on the cumulative damage theory. Equivalent material parameters of the protrusion layer were then applied to the whole models to obtain the tensile strength and failure modes of the joints. The results show that the strength and failure modes of the Comeld joints are affected by the density and height of protrusions, lap size of the joints and so on. The Comeld joints could have higher strength by adjusting parameters.
2015 Vol. 36 (1): 55-62 [
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253
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63
Analysis of the electric yielding zone of the anti-plane mode Ⅲ crack in piezoelectric materials of one-dimensional hexagonal quasicrystals
Abstract: Based on the anti-plane equations of piezoelectricity of one-dimensional hexagonal quasicrystals,the electric yielding zone of the anti-plane mode Ⅲ crack problem is analysed in this paper. The expression of the electric yielding zone is obtained by using the strip model and assuming the shear stress is a constant in the electric yielding zone.This method eliminates the singularity of the electric field and the stress field at the crack tip.The conclution is in accord with the reality and it will provide a theoretical foundation for the fracture analysis of the piezoelectricity of one-dimensional hexagonal quasicrystals.
2015 Vol. 36 (1): 63-68 [
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268
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69
DESIGN OF FLUTTER OPTIMIZATION FOR MISSILE’S PUCKER RUDDER STRUCTURE BASED ON TOPOLOGY OPTIMIZATION TECHNOLOGY
On the high-speed flight condition, the pucker rudder of missiles may have flutter problems that lead to damage even collapse of the structure in a few seconds. To improve the flutter characteristic of the pucker rudder and make the process more scientific and efficient, based on topology optimization technology, the program was developed to obtain a pucker rudder structure with higher critical flutter speed. The results show that the method has the following advantages: the traditional method like matching mass is left behind, on topology optimization technology, a new structure is achieved efficiently and accurately. The topology optimization is creatively applied to improve the flutter characteristic of the missile’s pucker rudder and the structural strength is checked after design. The flutter problem, a fluid-solid coupling problem, is simplified and the dynamics problem is innovatively transformed into statics problem so that it will be solved efficiently.
2015 Vol. 36 (1): 69-75 [
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349
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76
Evaluation of plastic stress singularities of anti-plane V-notches in hardening materials
Abstract: The interpolating matrix method for the determination of higher order stress and displacement fields for antiplane shear loading of power-law hardening materials is presented. First the asymptotic displacement field in terms of radial coordinates at the notch tip is adopted. When the material near the notch tips arises in plastic deformation, the Von Mises yield criterion and the plastic ‘total strain’ theory are used. By introducing the displacement expressions into the governing differential equations of the plastic theory, it results in a set of the eigenvalue problem of nonlinear ordinary differential equations with the stress singularity orders and the associated eigenfunctions. Then the interpolating matrix method is used to solve the eigenvalue problem by an iteration process. The several leading plastic stress singularity orders of antiplane V-notches and cracks have been obtained. Simultaneously the associated eigenvectors of the displacement and stress fields in the notch tip region have been determined with the same degree of accuracy. The validity of the present method is confirmed by comparing with the existed results in the numerical examinations.
2015 Vol. 36 (1): 76-84 [
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257
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85
Elastic analysis of elliptical cavity expansion
Cavity expansion theory have been widely used in geotechnical engineering problem as a mature theory tool. However, it is not applicable to the elliptical cavity expansion problem. Based on the conformal mapping method, the outer region of the initial elliptical cavity on the physical plane is mapped to the outer region of unit circle on the phase plane, and the displacement caused by the elliptical cavity expansion on the physical plane is transformed to the phase plane. The elastic solution of elliptical cavity expansion is presented by plane complex variable elasticity method. This degeneration solution of elliptical cavity is compared with the conventional circular cavity expansion and the reliability of the elliptical cavity expansion elastic solutions is verified. Then, the elastic mechanics characteristics of the elliptical cavity expansionare analyzed by application of an example. The results show that the degeneration solution of elliptical cavityis in agreement with the conventional cavity expansion elastic solution. It is more difficult to expand in the semi-major direction rather than semi-minor and the required expand pressure in the semi-major direction is larger than that in the semi-minor direction. In addition, when the expansion ratea2/a1=0.11/0.1=1.1, the effect radius of expansion equals to the 10 times of the cavity radius.
2015 Vol. 36 (1): 85-91 [
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404
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