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2012 Vol. 33, No. 5
Published:
论文
449
ANALYSIS OF THE ELECTRIC YIELDING ZONE OF THE ANTI-PLANE MODE III CRACK PROBLEM IN PIEZOELECTRIC MATERIALS
The yielding zone of the anti-plane mode III crack problem in piezoelectric materials is analyzed in this paper. Based on the strip model, the expression of the electric yielding zone is derived. The boundary conditions along the yielding segments have two types: one is the mechanical displacement continuity condition and the other one is that the stress is assumed to be constant in the electric yielding zone. The latter eliminates the singularity of the electric field and the stress at the crack tip, which is coincident with the reality. The two different conditions have the same results. The energy release rates of the two types are also derived in this paper. The electric yielding zone is also obtained based on the electric displacement relaxation model which is similar to the stress relaxation model by Irwin. Comparing the results of the two different models, the yielding zone size obtained by the strip model is approximately equal to the result of the electric displacement relaxation model. Therefore, under the condition of the small deformation, the results are effective.
2012 Vol. 33 (5): 449-455 [
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305
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456
Precipitate size and morphology effects on the creep behavior of Nickel-base superalloys
Nickel-base superalloys are used extensively in the hot regions of gas turbines, because they have excellent mechanical properties at high temperature. The morphologies and sizes of γ’ precipitates have strong effects on the creep properties of the alloys. In this paper, a crystal plasticity constitutive model is developed, which considers damage and strain gradient to reflect the size effect of the creep property. The creep behavior of Nickel-base superalloys with two different precipitate sizes and three different precipitate morphologies are studied. The results show that the model can reflect the size effect on the creep behavior of the alloy very well. At the same time, the precipitate morphologies also have important effects on the mechanical properties of the alloy. With the increase of the slenderness ratio of the precipitate, the creep life of the nickel-base superalloys is extending. This phenomenon indicates that the precipitate coarsening and morphologies influence the creep behavior of the alloy as a competitive mechanism.
2012 Vol. 33 (5): 456-464 [
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258
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465
Cohesive zone modeling of spallation in ductile metal
In this work, a cohesive zone model (CZM) is developed by means of embedding cohesive elements into FEM continuum elements, so that the energy dissipated in the separation of the fracture surfaces during spalling can be taken into account. The proposed numerical model is used to predict the rear free surface velocity profiles in flyer plate impact tests for steel samples under different impact velocities. The influences of the characteristic parameters of CZM on the computed free surface velocity profiles are discussed in detail. The simulation results indicate that the exponential damage evolution of cohesive elements is satisfied to describe the energy dissipated behavior during spalling. Once the characteristic parameters are calibrated by a reference test, the same parameters of CZM can be used to successfully predicte other free surface velocity profiles under different impact velocities. A satisfied agreement between the predictions and the experimental data , especially the oscillation frequency and decay of the free surface velocity profiles in the later phases of spalling. The results thus demonstrate that the proposed cohesive law is appropriated to characterize the energy dissipated behavior during spallation.
2012 Vol. 33 (5): 465-470 [
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337
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492
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471
Topology Optimization Design of Actuation Voltage in Plates with Active Constrained Layer Damping Treatments
A topology optimization approach is proposed to attenuate the vibration of plates with Active Constrained Layer Damping (ACLD) treatments through the optimal spatial distribution of the actuation voltage in piezoelectric actuator layer. A finite element model of laminates with two piezoelectric layers is established based on energy approach. The optimal distribution of the actuation voltage is formulated as a discrete optimization problem with two-level control voltage design variables, where structural modal damping ratio characterizing the vibration energy dissipation is to be maximized under a constraint on the control effort. Such a optimization problem is then transformed into a continuous one by introducing element-wise artificial design variables defining the topological feature of the actuation voltage distribution in piezoelectric constrained layer. A power-law function relating the design variables and the applied control voltages is proposed to penalize intermediate values of the design variables. The optimization problem is then solved effectively by using the Method of Moving Asymptote (MMA) algorithm tailored for the constrained voltage optimization problem based on the sensitivity analysis. Numerical examples demonstrate the validity of the proposed problem formulation and numerical approach.
2012 Vol. 33 (5): 471-479 [
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347
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480
ANALYSIS OF RESONANCE RELIABILITY SENSITIVITY FOR PIPES CONVEYING NON-UNIFORM AXIAL FLUID
Adopting the method of weighted residual, the natural frequencies of pipe conveying non-uniform axial fluid were calculated. In the process of analyzing, the trial function was also constituted via the order Galerkin truncation. After establishing the performance function of the resonance reliability of pipe conveying fluid, the resonance reliability sensitivity was deduced from the weighted nonlinear response surface method and Monte-Carlo reliability sensitivity estimation. The example results show that the proposed method is reasonable, high efficiency and high precision. The research in this paper is valuable for anti-resonance design and reliability sensitivity estimation of pipe conveying non-uniform axial fluid.
2012 Vol. 33 (5): 480-486 [
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305
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435
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487
Nonconforming Isogeometric Analysis based on NURBS with Exact Geometry
Inspired by the idea of the nonconforming finite element method, and intending to address the incompatible CAD geometry for isogeometric analysis, a new isogeometric method called Nonconforming Isogeometric Analysis (NIGA) is proposed in this paper. The main purpose is to apply the isogeometric analysis directly to the trimmed NURBS models for structural analysis. This can lead to an efficient method for the isogeometric analysis of both a general and complicated engineering structure.
2012 Vol. 33 (5): 487-492 [
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419
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493
Numerical simulation of damage in fiber reinforced composite laminates under high velocity impact
According to the macrostructure and microstructure of the composite laminates, a 3D finite element model for analyzing high velocity impact damage of composite laminates was established based on ABAQUS software platform. The cohesive elements were involved between two layers to simulate delaminations of the composite laminates, and a 3D visco-elastic constitutive model, coupled with Hashin failure criteria was used to predict the in-plane failure of composite laminates. By adopting this model, the ballistic performance and damage characteristics of composites laminates under high velocity impact were studied. The numerical results agree well with the experimental results. Parametric studies were conducted to study the effects of the strength parameters on the damage of composite laminates under high velocity impact. Some valuable conclusions were obtained.
2012 Vol. 33 (5): 493-500 [
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294
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简报
501
ELASTIC ANALYSIS OF MISFIT DISLOCATION DIPOLES IN AN ANNULAR COATING LAYER ON A CYLINDRICAL NANOWIRE
The interaction between misfit dislocation dipoles in the nanoscale coating layer and the nanowire is investigated. The analytical solutions of complex potential functions in the coating layer and the nanowire are derived by means of the complex variable method. With the aid of the Peach-Koehler formula, the explicit expression of the image force and the mismatch stress acting on the screw dislocation dipoles are given. The results show that the impact of the interface stress and the mismatch stress on the motion of misfit dislocation dipoles is very significant. Under certain conditions, the presence of the interface stress and mismatch stress can change the interaction mechanism between the misfit dislocation dipoles and nanowire. Compared to the macroscale linear materials, the equilibrium position of misfit dislocation dipoles in the nanoscale coating layer will increase for considering the interface effect, the coating layer is more easy to generate misfit dislocation dipoles. The equilibrium postion of misfit dislocation dipoles in the nanoscale coating layer will increase for considering the effect of nanowire lattice mismatch. It can be seen, we can control the generation of misfit dislocation dipoles by reducing the effect of nanowire lattice mismatch.
2012 Vol. 33 (5): 501-507 [
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281
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496
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508
Total reflection tunnel and multi-channel filtering of square solid- liquid phononic crystal
In order to study total reflection tunnel effect of elastic wave in 1D square solid- liquid phononic crystal , Use the transition matrix method to calculate the transmissivity of elastic wave when incident angle greater than full reflection angle. Total reflection tunnel effect is found in the transmission wave and there is a good multi-channel filtering characteristics. Obtained the change rule of the properties of total reflection tunnel effect filtering with period and quantum number and side of square. Provided a theoretical basis for designing the good performance of phononic crystal filter.
2012 Vol. 33 (5): 508-514 [
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230
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515
Dynamic Response of Cylindrical Shells under Two Kinds of Non-axisymmetric Synchronous Moving Loads
Bai Xiang-zhong
Dynamic response of a length-limited elastic cylindrical shell is researched to meet engineering requirements, on which non-axisymmetric loads include a moving concentrated load and an uniformly distributed load with synchronously increasing range of action. Dynamic differential equations with symmetrical forms are derived, and the two kinds of synchronous moving loads are expressed by the Dirac function and the Heaviside function. Based on the assumed displacement functions, the analytical dynamic solutions to the displacement and stress of the cylindrical shell are obtained by means of the Galerkin method and Laplace transformation. The algorithm is verified through the comparative analysis of the analytical solutions and the ANSYS numerical solutions for a specific example.
2012 Vol. 33 (5): 515-522 [
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374
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523
Analytic study on 1:3 internal resonance dynamics of honeycomb sandwich panels with completed clamped supported boundaries
The honeycomb core of cells was modeled as a layer of orthotropic material whose physical and the mechanical properties were determined by using the corrected Gibson’s formula．According to the classical plate theory and the large deformation, the governing equations of motion are established for the honeycomb sandwich panels subjected to the transversal excitation force by using the Hamilton’s principle. The transversal damping is taken into consideration. The method of normalization is utilized to transform the nonlinear vibration equations for the honeycomb sandwich panels to nonlinear system with double modes of freedom. Using the homotopy analysis method (HAM) solves the nonlinear vibration equations of the honeycomb sandwich panels and analyzes the change of amplitude with excitation frequency and vibration parameters. The case of the 1:3 internal resonance are considered. In addition, motion stability analysis of honeycomb sandwich panels is studied in this thesis. The result of the study offers the theoretical foundation and the numerical reference for the design and the practical application of Honeycomb Sandwich.
2012 Vol. 33 (5): 523-532 [
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260
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548
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533
the Optimal Structural Design of Stuffed Shields with Basalt and Kevlar Fiber Clothes against Hypervelocity Impacting
The impact ballistic performances of stuffed whipple shields with basalt and kevlar fiber clothes are investigated by two-stage light gas gun facilities. Protective performance、damage morphology and mechanism of stuffed material and cabin walls are obtained, compared with the impact limit curve of Nextel/Kevlar stuffed whipple shields. Also, the influences of epoxy resin coating on the protective performance are discussed. The data shows that stuffed whipple shields with basalt and kevlar fiber clothes have excellent protective properties in the high impact velocity. Coating with epoxy resin glue improve the prevention performance. Basalt fibers absorb energy by breaking projectile. Kevlar fibers have plastic deformation and fracture. Melting and carbonation process appear in the hypervelocity regions.
2012 Vol. 33 (5): 533-540 [
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265
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518
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541
Research on AE variation of sandstone brittle failure with along loading by uniaxial compression
Aiming at the changing of AE in sandstone, it was analyzed the AE accumulation counts and emission. Analyzing the relationship of AE and rock compression process under loading, it is classified the AE into five stages according the different deformation stages, which are the density stage, the elastic stage, crack stable growth stage, crack unsteady growth stage and the damage stage. Combining rock uniaxial compression results, it is shown that the strain ratio between the AE mutation of critical state and peaking state has a value range 74%and 78%, but the stress ratio has a larger discrete, which has a vaerage value nearly to 73%. In this article, it is discussed the new method to analysis of instability for rock brittle failure based on AE.
2012 Vol. 33 (5): 541-547 [
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244
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536
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