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2013 Vol. 34, No. 1
Published:
论文
1
Numerical simulation of macro-deformation for ionic polymer-metal composites under the electro-mechanical couple action
Based on electro-chemical-mechanical couple acting mechanism, the paper investigates the IPMC macro-deformation, as well as micro-mechanism using numerical simulating technique. With the help of developing platform of large commerical finite element program software, the user-defined subroutines have been incorporated and numerical analysis flow chart has been presented. The numerical results about the typical IPMC cantilever for deflecting deformation have achieved. The paper highlights the efficiency of blocking force for laminate, optimal thickness of metal electrode layer and heterogeneous deflecting deformation. Comparing the numerical results with those available from experimental measurements has validated the proposed technique. The results pave the way for modelling and designing more sophisticated IPMC-based products.
2013 Vol. 34 (1): 1-6 [
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283
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7
Energy principle for pit evolution and corrosion fatigue crack nucleation
As an irreversible thermodynamics process, the corrosion pit evolution of corrosion fatigue is controlled by the combined action of surface energy, elastic energy and electrochemical energy stored in the solid. Based on energy principle, the exploratory study of energy issues for corrosion fatigue pit evolution is carried on. A two-variable semi-ellipsoid model is proposed to describe the pit evolution, and shape parameter of semi-ellipsoid pit as a function of pit depth is derived in the process of corrosion fatigue. The stress intensity factor criterion is introduced to build the critical condition for pit transition to fatigue crack, At the same time, the effects of stress amplitude on corrosion fatigue crack nucleation life is discussed.
2013 Vol. 34 (1): 7-12 [
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281
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13
A finite element sub-partition method for simulating crack extension independent to global mesh
A numerical method combining finite element sub-partition and substructure is developed to simulate crack extension. In this method, crack is allowed to enter or separate an element or to extend along element side. Therefore, crack can extend along any path without the limitation of original mesh. The elements involving one crack are sub-partitioned according to the crack path and they are constructed a sub-structure. The size of substructure expands when the crack propagates. The additional freedoms introduced by element sub-partition are expressed by the freedoms of original mesh nodes via agglomeration of stiffness matrix. Therefore the total freedom dimension keeps constant whether cracks extend or new cracks appear. The crack initiation and extension laws are suggested based upon this sub-partition algorithm. This method is used to calculate the crack tip fields of central crack in infinite plane for both mono-material and bi-material to investigate its accuracy. It is further used to simulate micro-scale crack extension in particle, matrix and particle/matrix interface in a particle reinforced composite to prove its adaptability for simulating of complex path cracking.
2013 Vol. 34 (1): 13-19 [
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298
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20
APPLICATION OF NODIMENSIONAL LOAD SEPARATION METHOD IN THE DUCTIAL DUCTILE FRACTURE TOUGHNESS ESTIMATION
In view of the inconsistent dimension problem in current load separation theory, a nodimensional load separation method according to similarity principle was proposed. The universality of the nondimensional load separation properties corresponding to CT and SEB specimens has been successfully certificated by elastic plastic finite element analyses. On the basis of the new nodimensional load separation principle, improvement on the separation parameter Spb method has been conducted. The effect of the selection of reference blunt cracked specimen and calibration points on the instantaneous crack length determination for sharp cracked specimen has been eliminated by the modified Spb method. And the feasibility of this method is confirmed on comparison of unloading compliance method. By use of the modified Spb method, an assessment on the crack tip opening displacement of certain welded ball valve has been carried out.
2013 Vol. 34 (1): 20-30 [
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232
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31
NEW FRCTURE CRITERION FOR MIXED MODE CRACKS
For mixed mode I-II cracks, the plastic zone distribution around crack tips is analyzed theoretically. Two groups of parameters which can be used to evaluate the effect of stress state on crack fracturing are introduced, and the local plastic deformation is considered. In this study, we adopt the following two assumptions: (1) cracks propagate in the direction in which the plastic core region boundary is the shortest to the crack tip; (2) once the radius from crack tip to the shortest plastic core region boundary reaches the critical radius, the crack start to propagate. Based on these assumptions, a new fracture criterion is developed, and the comparisons with the existing fracture criterions and the experimental results are conducted. The results show a well-de?ned correlation between the experimental data and the results according to the new fracture criterion. In addition, some discussions on the limitations of the criterions which are established just by single KIC or single KIIC and the necessity of considering the crack tip’s stress state are presented.
2013 Vol. 34 (1): 31-37 [
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564
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38
NUMERICAL MANIFOLD ANALYSIS OF COMPLEX CRACK PROBLEMS ON POLYGONAL ELEMENTS
The numerical manifold method (NMM) can tackle both continuous and discontinuous with high efficiency and accuracy. Due to the independence of the mathematical cover system and the physical domain, the NMM is very suitable for crack problems. At the same time, the n-sided elements (n>4) are also very attractive due to their greater flexibility in meshing and higher accuracy, compared with the frequently used triangular and quadrilateral elements. In the present paper, the NMM, combined with the regular hexagonal mathematical elements, is applied to solve linear elastic complex crack problems. Through the interaction integral, the stress intensity factors at concerned crack tips are computed in typical numerical examples, and the results agree well with the reference solutions. In addition, the accuracy on different mathematical elements is also investigated and the results show that the accuracy on hexagonal elements is higher than that on regular triangular and quadrilateral elements.
2013 Vol. 34 (1): 38-46 [
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229
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简报
47
MINIMUM COMPLIANCE DESIGN OF PERIODIC LATTICE MATERIALS BASED ON EXTENDED MULTISCALE FINITE ELEMENT METHOD
The paper deals with the problem of minimum compliance design of structures composed of periodic lattice materials with the sectional area of micro components as design variables under volume constraints with Extended Multiscale Finite Element Method. Considering unit cells with finite size, optimization model which adapts to the structure with complex geometry and loading conditions has been established. The size effect of micro-structure of the lattice materials is discussed. Cantilever and L-shaped beams under linear boundary condition and periodic boundary condition are optimized with sequential quadratic programming algorithm. The reliability of the optimization model and algorithm are verified by the numerical examples. The paper presents a new approach for optimization of lattice materials to compose engineering constructions.
2013 Vol. 34 (1): 47-54 [
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392
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55
LAMB WAVES PROPAGATION ALONG NON-PRINCIPAL DIRECTIONS IN ORTHOTROPIC PLATE
Based on linear three-dimensional elasticity, the equations of wave motion for coupled Lamb waves are derived by using a Legendre orthogonal polynomial approach when waves propagate along non-principal directions of the material, and the coupled equations of wave motion are also solved numerically. Firstly, for verifying the applicability and validity of this proposed method, this approach is applied to isotropic material and obtained results are compared to known results. Then, the phase dispersion curves of coupled Lamb waves along different non-principal directions are calculated, and the effects of the different propagation directions on fundamental modes and high-order modes are investigated. Finally, the distributions of phase and group velocities of fundamental modes are shown respectively, which have the great potential for structural health monitoring of anisotropic materials.Simultaneously, the reason that S0 mode is the most sensitive to the change of the propagation direction is illustrated with considering of both displacement distribution of fundamental modes and material’s anisotropy property.
2013 Vol. 34 (1): 55-62 [
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281
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63
ENERGY AND CONTACT FORCE STUDY OF COMPOSITE LAMINATE IMPACT DAMAGE RESPONSE
Abstract： Three layups of Composite laminate are tested about dropping weight and CAI. The impact response is recorded, and parameters like contact force and energy are analyzed on their characteristics and diversity. It is discovered that the shape of contact force versus time curve apparently changes while the energy level increases, relative to the laminate’s damage resistant ability. Impact energy, absorbed energy and damage dissipated energy are obtained and their relationships with dent, delamination and CAI strength are analyzed and discussed. Results show that damage is more linearly relevant to impact energy than absorbed energy, although the latter seems to be more account theoretically. Maximum contact force is no way to characterize damage, for the test data tell that it is only a threshold due to the laminate’s resistant ability. Additionally, the impact is simulated via ABAQUS. Response curves are obtained and damage is predicted, both of which fit the testing results.
2013 Vol. 34 (1): 63-72 [
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262
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73
Modeling and elastoplastic simulation of hollow particle filled composites
Syntactic foams are particulate composites obtained by filling a polymeric matrix with hollow glass microballons (HGMs). RSA (Random Sequential Adsorption) method was used to generate the representative volume element models of syntactic foams. Through the finite element analysis, the stress-strain relationship of each type of syntactic foams was obtained. Material properties of syntactic foams were simplified to bilinear kinematic hardening model. The effects of HGM filling ratio and wall-thickness to the elastic constants and yield stress of syntactic foams were analyzed. Results show that wall-thickness ratio of HGM plays a crucial role in the effective Young’s modulus and yield stress. The higher specific modulus and specific strength characterize the good performances of syntactic foams. Distributions of stress and plastic strain depend on the HGMs wall-thickness also.
2013 Vol. 34 (1): 73-82 [
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294
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83
Structural damage detection based on reconstructed phase space
In this paper, the technology of phase space reconstruction in chaotic theory is introduced and applied in the structural damage detection and health monitoring. The feasibility of the damage detection method based on the topology of phase space is analyzed using a 1-demention oscillator. The results indicate that the differences of topology of phase spaces are obvious between the initial system and the damaged ones with changing stiffness. Using the technology of phase space reconstruction in nonlinear chaotic attractor field, the dynamic responses are directly displayed into phase space. Using the changes of phase space topology of intact and damaged responses，a new damage feature is extracted. In order to demonstrate the method, a dynamic experiment on circular arch is designed. The experimental results indicate that this method can successfully identify the location and the quantification of the damage, and the new feature is much more sensitive than signature analysis approaches. This method can calculate the value of the feature using single dynamic response, which can be used in the structural health monitoring as a global damage feature to monitor the existence of damage and the structural health status.
2013 Vol. 34 (1): 83-92 [
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313
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93
Collapse simulation of the subway structure during the earthquake based on the two-scale coupled method
Based on the improved discrete-continuum soil model, simulation of the collapse process of the Daikai station and the large deformation of the surrounding soil is performed. This paper improves the optimization model which is solved by the Lagrange multiplier method and is utilized to enforce force continuity on the coupling boundary. Then this improved model is applied to the discrete-continuum model. The continuity between the discrete and continuum domains is fulfilled by interchanging velocities and forces between them. By performing the free vibration column simulation and numerical cyclic biaxial tests, the degradation curve for the particle assembly is fully obtained and applied to the continuum model. Damage pattern obtained from the simulation is very similar to the collapsed situation of the subway station after the earthquake. Besides, from a quantitative perspective, the subway station column’s horizontal differential displacement obtained from simulation is compared with that from existed paper. It is shown that, coupled macro-micro approach can efficiently reduce particle numbers and provide a micro perspective on soil and the structure experiencing damages in the concerned zone.
2013 Vol. 34 (1): 93-102 [
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228
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374
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