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2012 Vol. 33, No. 2
Published:
论文
125
Dynamic Response of thermoelastic foundation with voids under a moving periodic load
DOI:
According to the linear theory of thermoelastic materials with voids, a mathematical model of dynamic response analysis of a thermoelastic foundation with voids subjected to a moving periodic loading is established, and the six kinds of necessary periodic boundary conditions on the periodic boundary are presented to analyze the dynamic response of the foundation, namely, (1)the displacements are equal; (2)the stresses are equal; (3)the volume fraction of voids and its derivative along the normal direction are equal; (4)the temperature and its derivative along the normal direction are equal. On this basis, the differential quadrature method (DQM) and the backward difference scheme are applied to discretize the governing equations on the spatial and temporal domains, respectively. As numerical examples, the dynamic response of a thermoelastic foundation with voids subjected to a plane moving periodic load is analyzed, and also the dynamic characteristics of the foundation under a limit moving vehicle load are studied. The effects of the vehicle velocity on the settlement, the volume fraction and temperature are considered. One can see that the DQM presented in this paper has advantages in solving the problems with periodic boundary conditions, such as high accuracy, efficiency, and good convergence.
2012 Vol. 33 (2): 125-135 [
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297
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136
Effect of Interface and Thermal Residual Stress on Effective Properties of Giant Magnetostriction Composites
DOI:
Based on the Mori-Tanaka theory, we considered the influence of interface effect on giant magnetostriction composites, and obtained the general analytical expression of giant magnetostriction composites effective properties. The thermal residual stress in the curing process has an impact on the effective properties of giant magnetostriction composites which is also considered. Through numerical calculation, the results show the changes of the effective modulus, the effective magnetostriction, the effective thermal expansion coefficient of high magnetostriction composites with inclusion’s aspect ratio, inclusion’s volume fraction and interfacial parameters. Interface and thermal residual stress significantly affected effective properties of giant magnetostriction composites.
2012 Vol. 33 (2): 136-145 [
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318
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146
Propagation of SH Waves in Functionally Graded Piezoelectric Sandwich Structures
DOI:
This paper investigates shear horizontal (SH ) waves propagating in a sandwich structure consisting of a piezoelectric layer and two different functionally graded piezoelectric half-spaces. The material properties of the piezoelectric half-spaces vary exponentially in the direction perpendicular to the interfaces. The closed-form expressions of electro-elastic fields for SH waves are derived. By using the continuous conditions at the interfaces, the dispersion equations are given in determinant form. Based on the dispersion equations, the numerical examples are presented to show the effects of variations of material properties, piezoelectric layer thickness and different combinations of materials on the phase velocity. The obtained results are useful for the application of functionally graded piezoelectric materials to acoustic wave devices such as plate resonators, filters and sensors.
2012 Vol. 33 (2): 146-152 [
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325
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153
Band gaps of one-dimensional magneto-electro-elastic quasi-periodic structures
DOI:
Band gaps for the two kinds of magneto-electro-elastic quasi-periodic structures with Fibonacci sequence, one is the piezoelectric/(elastic/piezomagnetic) and the other is the (piezoelectric/elastic)/piezomagnetic are studied by the transfer matrix methods. The normal incidence case for the shear waves (SV waves) is considered. The localization factors and displacement transmitted coefficients are computed and its band gaps are compared with the corresponding perfect periodic structures. The results show that the band gaps of the two structures are quite different. The band gaps for the (piezoelectric/elastic)/piezomagnetic quasi-periodic structures are indeed similar with those of the pure elastic structures with Fibonacci sequence.
2012 Vol. 33 (2): 153-161 [
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296
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162
Diffusion-induced Stress in the Intermetallic Compound Layer of Solder Joints
DOI:
Intermetallic compound (IMC) layers formed during soldering processes have a significant effect on the reliability of solder joints. The atomic diffusion effect during reflow and isothermal aging leads to growth and morphological evolution of IMC layers, and stress is developed in the IMC layers. The changed microstructure and the stress in the IMC layer result in degradation of mechanical performance of solder joints. Based on the mechanism of atomic diffusion-reaction, the diffusion-induced stress during the growth of the IMC layer is investigated. An analytic model with two interfaces(Cu/Cu6Sn5/Solder）at the early stages of IMC formation is proposed, and then the copper concentration distribution in the IMC layer is calculated by using the Laplace transformation method. Diffusion-induced stresses are obtained analytically by transforming atomic diffusion effects into bulk strain. The results show that the diffusion-induced stress is compressive, and it reaches its peak at the Cu/Cu6Sn5 interface. The diffusion-induced stress increases with the increase of the isothermal aging time, and finally it becomes stable and changes linearly along the thickness of the IMC layer.
2012 Vol. 33 (2): 162-167 [
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332
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168
RESEARCH ON THE INFLUENCE OF STEAM PARAMETERS ON DYNAMIC CHARACTERISTICS OF PIPELINE SYSTEM
DOI:
Considering influence of fluid parameters, pressure and flow rate ,etc, on the bending motion of pipeline, the 12-equation models described straight and curve pipe conveying fluid were improved，and also were verified by numerical examples. Based on these models, dynamic problems of complex systems were solved by transfer matrix method which is convenient and feasible, and also has more advantages compared with finite element method, etc. In this paper, the influence of steam parameters on the natural characteristics of steam pipeline systems was studied. The results show that the extent of the influence of steam pressure on the natural frequencies of pipeline systems was mainly dependent on the parameters of pipe section, and the influence of flow rate was relatively not significant. These conclusions have some reference value for engineering practice.
2012 Vol. 33 (2): 168-175 [
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277
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简报
176
Study on the plate’s size effect on the explosive welding quality of large-sized plate
DOI:
Abstract: The reason for the explosion welding defects of large-sized plates is not explicitly found because of the particularity in the process of explosion welding. In this paper, the cause of the defects during the explosive welding for plates sized from 3.5m to 7.0m is investigated by the Dynamic nonlinear numerical simulation. Folding deformation can be found during the explosion welding based on the study on the changes of the flyer plate at different time. The study shows that the occurrence of the plates’ folding deformation is closely related to the size of the used plates. There are some regular relations between the duration, the position, the maximum spatial depth of folding deformation and the size of the metal plates.
2012 Vol. 33 (2): 176-181 [
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264
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182
Study on the delamination of fiber-metal laminates under low-velocity impact
DOI:
In this paper, cohesive zone model is used to study the delamination of FMLs under low-velocity impact. The model owns two main advantages: one is that no initial crack is needed to be assumed; another is that there is no need to remesh the model during the crack propagation. First, to validate the cohesive zone model in dealing with delamination of composite laminates, the delamination simulation is carried out under the low-velocity impact and a relative good agreement is achieved with the experimental data. Next, the delamination of FMLs with different metal ratios is investigated under low-velocity impact and the results are compared with that of composite laminates. Last, the effects of stacking structures and metal ratios towards the delamination of fiber/metal laminates are studied according to the principle of energy balance.
2012 Vol. 33 (2): 182-188 [
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305
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189
Topological Optimization of the Plate Structure Subjected to the Frequency Constraints
DOI:
In this paper, a model of topology optimization for the lightest plate structures with frequency constraint is constructed based on Independent, Continuous and Mapping(ICM) method. Exponential function is adopted as filtering function of the element weight, the element mass and the element stiffness. Through the first-order Taylor expansion of Rayleigh quotient, which is described by the reciprocal variables of the filtering function of the element stiffness, the frequency constraint is approximately expressed as an explicit function. The dual theory is used to convert the constrained optimization model with a large number of design variables into the quasi-unconstrained optimization model with less design variables, which is solved by the sequential quadratic programming(SQP). Therefore, the solving efficiency is improved. The MSC.Patran & Nastran software and Patran Command Language(PCL) are selected to develop the topology optimization software for plate structures with frequency constraint in there. The numerical results show that the ICM method possesses stable iteration and efficient convergence.
2012 Vol. 33 (2): 189-198 [
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420
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199
Research on the coupling of anisotropic damage and plasticity constitutive model for quasi-brittle materials
DOI:
Strength softening and stiffness degradation, unilateral effects, strength enhanced under confine and soften upon tension and compression, irreversible deformation, dilation and non-elastic expansion, all of above non-linear properties were considered, and within the framework of the thermal-dynamics, the coupling of anisotropic damage and plasticity constitutive model for the quasi-brittle materials has been established in this paper. The deformation mechanisms of brittle materials and damage-induced anisotropy have been interpreted; meanwhile the relations among various physical quantities between the damage configuration and effective configuration have been developed. The plastic yield criterion and the different plastic kinematic hardening rule and isotropic hardening law for the tension and compression have been studied in effective stress space. Within the damage configuration, adopted strain energy release rate, the tension and compression damage criteria have been established, and the different kinematic hardening rule and the isotropic hardening law for the tension and compression damage have been studied simultaneously. Based on the plastic yield criterion and damage criterion, the plastic potential functions and the damage potential function were constructed. The evolution of strengthening effect plastic and damage internal state variables have been derived through the orthogonal principle, at the same time, the evolution of the internal state variables, which described the plastic flow and damage evolution, have been developed through combination of plastic yield surface and damage loading surface. Integrated the damage mechanics and plasticity, the strain-driven stress-strain incremental constitutive relation has been established, and the key points of the numerical integration about the constitutive equations were given. The identification and calibration of constitutive material constants have been accomplished through uniaxial loading - unloading cyclic loading test, and the uniaxial monotonic test, uniaxial loading - unloading cyclic loading, two-axis pressure, two-axis tension and compression tests and triaxial compression tests Were predicted and compared with experimental results. The results show that the constitutive model has good predictive ability for nonlinear material properties of quasi-brittle materials.
2012 Vol. 33 (2): 199-208 [
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536
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209
Coupled Movement Electromechanical Coupling Model of Multi-Stage Inductive Coil Gun
DOI:
Abstract: For Multi-stage synchronous inductive coil gun, the more mature model in the past literature is electromechanical model based on current filament method. Its merit is that calculation speed is very fast, but its defect that it does not consider the effect of peripheral structure and material of coil gun. Against this case, this paper sets up the 3D transient electromagnetic field-circuit-moving model of Multi-stage inductive coil gun, which uses vector magnetic potential 、current in the circuit. The force is calculated by nodal force method. According to kinematics model of armature, finite element analysis(FEA) model coupled circuit field and movement used in analyzing Multi-stage inductive coil gun is presented in this paper. The performance of a 5 stage inductive coil gun is analyzed using above model. The calculation result is very close to the measure results, which verifies the model precision.
2012 Vol. 33 (2): 209-218 [
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317
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219
The transient response of cylindrical lining in poroelastic saturated half-space
DOI:
Buried lined tunnels are often subject to internal dynamic loading, such as blast loading and impact loading. The dynamic stress concentration of lining structure due to various dynamic sources is a special concern in practical engineering. The transient dynamic response of a cylindrical lining subjected to sudden internal uniform loading has been presented with the Laplace transform and the method of the separation of variables. The wave potentials in a homogeneous saturated half-space were expanded in Fourier-Bessel series using the wave function expansion method. A convex approximation was used to replace the straight boundary of the half-space. In terms of continuity conditions and boundary conditions of the problem, the unknown coefficients in potentials were determined by coordinate transform. The dynamic responses of the lining structure in saturated half-space are discussed for the different buried depth of lining. The study is reasonable for engineering practice and provides an effective method for analyzing the similar problem about dynamic response of underground structure.
2012 Vol. 33 (2): 219-226 [
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278
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