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2012 Vol. 33, No. 6
Published:
论文
557
Deformation and stress analysis of the placed stent vascular wall
Abstract: To calculate the impact of working status of vessel wall with atherosclerotic and partial blockage of plaque formation. Base on the continuity equation of blood flow , the equation of motion and vessel wall equation of blood pressure .By given the wave function on the basis of blood pressure we can obtain a narrow blood vessel wall radial displacement and hoop stress and analysis of the different degree of stenosis of the vessel wall deformation and stress of . The force required to vascular stents of under different narrow circumstances and different levels of local plaque sclerosis and calculated the vessel wall after stent implantation of the radial displacement and stress state. The results of this study for clinical and correct stenting stent stenosis on the deformation and stress analysis of reference . Can avoid congested or hardening of blood vessels transition, due to stenting of inadequate medical vascular rupture.
2012 Vol. 33 (6): 557-565 [
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531
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566
Prediction on the strength parameters of cohesive zone model for simulation composite delamination
A micromechanical model based on the periodic RVE technique is presented to predict the cohesive strength which is an important parameter in accurately modeling composite delamination via CZM (cohesive zone model) based FEM. By using major principal stress criterion to predict the crack initiation in cohesive layer, a relationship between cohesive and matrix strength is set up. A periodic displacement boundary condition has been presented on the assumption that the RVE is orthotropic in the sense of overall response. The cohesive strength of AS4/PEEK and T700/QY8911 laminates at various fibers cross angles are obtained by this model. The FEM simulations on mixed-mode-bending (MMB) and the six-point bending test are presented by applying CZM with the predicted cohesive strength. The numerical results are in fair agreement with experimental observation.
2012 Vol. 33 (6): 566-573 [
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356
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574
NUMERICAL SIMULATION OF SCALE EFFECTS ON THE RESPONSE OF COMPOSITE LAMINATED PLATE UNDER LOW-VELOCITY IMPACT
Based on scaling rules, three 3D finite element models were established for studying scale effects on the response of composite laminated plate under low-velocity impact. In the finite element model, Modified Chang-Chang criteria was used to predict interlaminar damage in a composite plate subjected by low-velocity impact, and delamination between the ply interfaces was simulated by interface elements. Material property should be degraded once impact damage generated. Three composite laminated plates of different size under low-velocity impact were analyzed with these three finite element models, and impact response under different impact velocity was compared. According to the results，some conclusions can be obtained: If the lower impact velocity did not generate damage in the composite laminated plates, the displacement and the contact force agree with the presented scaling rules; Whereas, the contact force does not agree with the scaling rules well once the impact damage was generated, moreover, if the velocity ratio between different models was equal to the square root of their scale factor, the relative delamination size in the models was nearly the same. These conclusions were agreed with experimental results. Further investigation on the in-plane damage shows that its size is not consistent with the scaling rule.
2012 Vol. 33 (6): 574-582 [
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543
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583
Approximate analytic solution of Sound radiation from stiffened finite plate coated with decoupling layers
the vibration and sound radiation of finite stiffened plate coated with decoupling layers in semi-infinite water was investigated in this paper. And Approximate analytic solution of the vibration and sound radiation of stiffened plate coated with decoupling layers were derived. Using of elasticity theory to describe the decoupling layer, response function was constructed by mode superposition theory, the material loss factor was considered by the form of complex modulus, the effects of stiffeners was treated as reverse forces, analytic model of stiffened plate with decoupling layer treatment was obtained. Using deformation harmonious conditions of the interface between stiffened plate and decoupling layer and continuity conditions of surface of fluid-structure，the vibration equation coupled by sound-fluid-structure was composed. Combined with numerical methods, the vibration and sound radiation of stiffened plate were received. Carrying out the corresponding numerical results agree well with model test results to verify the correctness of this method.
2012 Vol. 33 (6): 583-591 [
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291
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542
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592
An interacting crack-mechanics based model for elastoplastic damage model of brittle materials under compression
A micro-crack elastoplastic damage model under compressive loading is presented in this work. Interactions among the cracks are modeled by self-consistent approach in which each crack experiences a stress field different from that acting on isolated cracks. The propagation of wing crack in the micro-crack tip is characterized for rock damage, and the wing crack length is obtained using Newton iteration based on the strain energy density for mixed-mode fracture. The distribution of micro-cracks is presented by the absolute volume strain with the two-parameter Weibull statistical model. The damage evolution variable of rock is employed by the distribution of micro-cracks and stress release volume described by length of wing-crack. Voyiadjis’s strain hardening function is employed as the plastic yield function and plastic potential function. The elastoplastic damage model with its numerical algorithm is proposed and the code of elastoplastic damage model is implemented by using return mapping implicit integration algorithm. The influence of rock confining pressures on the damage response in the elastoplastic damage model is analyzed. The results show that the proposed elastoplastic damage model agrees well with the experimental results for one rock test under uniaxial compression.
2012 Vol. 33 (6): 592-602 [
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397
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简报
603
Multiobjective Optimization Design for Trusses of Spacecraft Antenna
A multiobjective structure optimization method is presented for trusses of spacecraft antenna with appended structures. To set up an accurate finite element model for optimization design, the effect of appended structure stiffness on the truss dynamics characters is discussed. The structure topology configuration is decided using the surrogate model and the man-machine interactive method. For the surrogate model, optimal Latin hypercube sampling method is used as the design of experiments strategy, and radial basis functions are selected as the approximation method. The multiobjective evolutionary algorithm NSGA-II which produces a set of Pareto solu-tions is employed as the optimization strategy to trade off the minimization of weight and the maximization of natural frequency. The optimum solution is visually identified with the level diagrams which is a graphical repre-sentation of the Pareto front and the Pareto set. The results demonstrate that the weight is reduced by 29.66% with-out decreasing the natural frequency relative to the initial design scheme. This method not only can maintain good design efficiency, but also increase the global search capability. It is very useful for the multiobjective optimization design of spacecraft structures.
2012 Vol. 33 (6): 603-610 [
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342
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550
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611
The Ultimate Bearing Capacity of the Interaction Between Ice and Offshore Structures
In order to study the deformation of ice and the interaction between ice and the offshore platform structures，Smith yield criterion from geotechnical mechanics was introduced to the elasto-plastic analysis of ice. The mechanical properties of ice affected by the existence of cavity and the different tensile-compression strength ratio were analyzed in meso-mechanics, and the constitutive equation was established. Then the analytical solution of stress field caused by interaction between ice and rectangular vertical structure were deduced by structure partition method. Finally, the ultimate bearing capacity of ice was discussed with different values of pressure-sensitivity and the tension-compression ratio by numerical analysis. The results show that Smith yield criterion could reflect correctly the existence of cavities and the effect of different tension-compression yield strength on the ice mechanical properties.
2012 Vol. 33 (6): 611-616 [
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321
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617
THERMAL BENDING ANALYSIS OF SIMPLY SUPPORTED THIN PLATE BY THE HYBRID BOUNDARY NODE METHOD
Thermal bending problem of thin plate is analyzed by the hybrid boundary node method in this paper. The boundary local integral equation of isotropic thin plate is established based on thermal elastic theory and modified variational principle of thin plate. The domain variables are interpolated by fundamental solution, while the boundary variables are approximated by moving least squares. Only discrete nodes are constructed on the boundary, and no meshes are needed either for the purpose of interpolation of the solution variables, or for the numerical integration, so the present method is a truly boundary type meshless method. The numerical examples show that this approach has such advantages as high efficiency, good accuracy and high convergence rate.
2012 Vol. 33 (6): 617-622 [
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288
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623
EVALUATION OF THE STRESS SINGULARITY ORDER FOR THREE-DIMENSIONAL V-NOTCH
After the expression of displacement asymptotic expansion is introduced into the linear elasticity equilibrium equation, the characteristic differential equation with respect to the stress singularity order of 3-D V-notch is proposed. By applying the interpolating matrix method to solving the established equation, all the stress singularity orders companying with the corresponding characteristic angle functions can be yielded at a time. All the calculated stress singularity orders have the same high accuracy by comparing with the existed results. The numerical results show that, part of the singularity orders is converging to the theory resolution of the plane strain V-notch problem. However, the number of the singularity orders for 3-D V-notch is more than the one of 2-D plane strain V-notch. If the plane strain theory is used to predict the stress singularity orders of 3-D V-notch, part of the important singularity orders will be lost.
2012 Vol. 33 (6): 623-630 [
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314
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631
Impact crushing probability of coal particles based on fractal statistical strength theory
The impact crushing probability of coal particles was investigated based on fractal statistical strength theory. The function relations between impact crushing probability of coal particles and maximum contact pressure stress were obtained by the hypothesis of the Hertz contact. Combined with the impact dynamics theory, the fractal model of impact crushing probability was established. The impact crushing experiments of coal particles in different mines were taken. The statistical analysis shows that the impact crushing probability and impact velocity are linear relation on the logarithmic coordinate, which indicates that the impact crushing probability of coal particles is well described by the fractal model. The impact crushing probability of coal particles under different impact velocity and the needed impact velocity crushing all coal particles, which provide the theoretical direction for the evaluation of impact crushing effect and the determination of the impact velocity, can be both obtained after the fractal dimension and the crushing constant of the fractal model are determined by experiments.
2012 Vol. 33 (6): 631-636 [
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306
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637
Frequency Responses of a Partial Sealed Tunnel with Fractional Derivative Viscoelastic Lining
The concrete lining has viscoelastic properties, none of previous classic Kelvin model, theory of elastic and shell can describe the whole process of its creep. Based on saturated porous medium theory, the steady state dynamic responses of a partial sealed tunnel with fractional derivative type viscoelastic lining in saturated viscoelastic soil are investigated in the frequency domain subject to the axisymmetric radial traction and interior water pressure. On the basis of introducing a partial permeable boundary condition, the analytical solutions of stress, displacement and pore pressure of the lining and saturated soil are respectively obtained by the inner boundary of the lining and continuity conditions of the interface, besides, the stress and displacement constitutive behavior of the lining is described by fractional derivative viscoelastic constitutive model. The influences of the order of fractional derivative, the material parameter of the lining, relative permeability coefficient on the dynamic characteristics of the system are examined.. It is shown that the order of fractional derivative has a greater influence on the system dynamic responses, and it depends on material parameter of the lining. In addition, relative permeability coefficient has significant effects on the system responses.
2012 Vol. 33 (6): 637-643 [
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282
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644
A REGULARIZED BOUNDARY ELEMENT METHOD FOR ORTHOTROPIC ELASTIC PROBLEMS
yao ming zhang
This presentation is mainly devoted to the research on the regularization of indirect boundary integral equations (IBIEs) for orthotropic elastic problems and establishes the new theory and method of the regularized BEM. Some integral identities depicting the characteristics of the fundamental solution of the considered problems and a novel decomposition technique to the fundamental solution are proposed. Based on this, together with a limit theorem for the transformation from domain integral equations into boundary integral equations (BIEs), the regularized BIEs with indirect unknowns, which don’t involve the direct calculation of CPV and HFP integrals, are presented for orthotropic elastic problems. The presented method can solve the considered problems directly instead of transforming them into isotropic ones, and for this reason, no inverse transform is required. In addition, this method doesn’t require to calculate multiple integral as the Galerkin method. Furthermore, the proposed stress BIEs are suited for the computation of displacement gradients on the boundary, and not only limited to tractions. Also, they are independent of the displacement gradient BIEs and, as such, can be collocated at the same locations as the displacement gradient BIEs. This provides additional and concurrently useable equations for various purposes. A systematic approach for implementing numerical solutions is produced by adopting the discontinuous quadratic elements to approximate the boundary quantities and the quadratic elements to depict the boundary geometry. Especially, for the boundary value problems with elliptic boundary, an exact element is developed to model its boundary with almost no error. The convergence and accuracy of the proposed algorithm are investigated and compared for several numerical examples, demonstrating that a better precision and high computational efficiency can be achieved.
2012 Vol. 33 (6): 644-654 [
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344
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545
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