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2013 Vol. 34, No. 3
Published:
论文
217
Development and Application of the Theory of Nonlinear Stress Wave Propagation
Stress wave propagation theory is the basis for analyzing the dynamic response and failure characteristics of structures and materials under explosion/impact loads. It is of significant value in the defense and civil engineering. A review and some discussions on the development of the theory of nonlinear stress wave propagation and its engineering applications, carried out by the authors in nearly half a century, are presented in this paper, which includes the interaction of nonlinear stress waves and unloading failure due to the unloading stress wave, the theory of nonlinear viscoelastic wave propagation and its application, the interaction between dynamic damage/failure and stress wave, as well as the application of stress wave theory in protective engineering.
2013 Vol. 34 (3): 217-240 [
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241
The description of elasto-damage to fracture process of structures using component assembling model and comparison with cohesive zone model
The responses of structures originate from those of materials. The damage and failure process of structure corresponds to the deterioration of materials essentially. Considering the microscopic deformation mechanism of materials, based on pair functional potentials and Cauchy-Born rule, component assembling model is developed with two kinds of components, spring-buddle and cubage components. Since the essence of damage and fracture is the decrease and loss of atomic bonding force in microscopic and that the spring-buddle component is abstracted from the atomic bonds in the same direction, damage can be reflected by the force response function of spring-buddle components. Assembling the responses of two kinds of components, the elasto-damage constitutive equations are derived. This model can describe the whole deformation process of elastic, damage and failure of materials consistently. It is coded using the user subroutine UMAT and then implemented in ABAQUS to simulate the response of structures. In this paper, a numerical simulation of three point bending beam with precrack is performed to describe the crack propagation process. Comparing the response of structure using the present model with that obtained by the cohesive zone model, the stress-displacement curve are given by the present model and compared with that assumed in cohesive zone model, and a physical explanation is given to the crack propagation process in terms of damage evolution of materials.
2013 Vol. 34 (3): 241-246 [
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293
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247
INVESTIGATIONS ON THE INTRINSIC MECHANISMS OF STRAIN RATE EFFECTS OF BRITTLE GRANULAR MATERIALS
With the modified Split Hopkinson Pressure Bar (SHPB), the dynamic and quasi-static compression responses of silica sand were tested, and it exhibited obvious stress-strain effects. With diffractometry, corresponding grain size distributions of the specimens after dynamic and quasi-static loading were measured. Under the same stress level, the breakage amount in the specimen after quasi-static compression was bigger than that after dynamic compression. Building the relationship of the relative breakage to external work, the results show that the breakage efficiency of quasi-static loading was much higher, which is the intrinsic mechanism of strain rate effects for brittle granular materials.
2013 Vol. 34 (3): 247-250 [
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312
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251
The Overall Buckling Analysis on Hard Sandwich Rectangular Interlayer Board
Abstract: This article is based on the displacement mode which put forward by Reissner type theory, to amend the soft sandwich hypothesis, puts forward a hard sandwich hypothesis, namely to considering the Sandwich layer’s in-plane stiffness and bending stiffness, get the geometric equations and physical equations of hard-sandwich plate, established the balance differential equation of the hard sandwich interlayer board structure which in the in-plane parallel loads. Simplify the equation, got the analytical solution of the hard sandwich interlayer board structure’s critical load which under the condition of four simply supported, and calculate the influence of the sandwich layer material’s elastic modulus, thickness, Poisson’s ratio and density on hard sandwich board’s critical load, the results show that, the sandwich layer’s in-plane stiffness has great influence on the critical load, consider the in-plane stiffness is necessary.
2013 Vol. 34 (3): 251-258 [
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259
MICRO-MACRO HOMOGENIZATION CONDITIONS OF HETEROGENEOUS COSSERAT CONTINUUM
One of the key problems in multi-scale homogenization modeling based on the average-field theory is the proper prescription of boundary conditions on the representative volume element (RVE), with which the Hill-Mandel condition, i.e. the Hill’s macro-homogeneity condition, can be satisfied. From the existing contribution to the heterogeneous Cosserat continuum, only mixed translational displacement-surface couple boundary condition can be prescribed. While other commonly used RVE boundary conditions, such as uniform translational and rotational displacement boundary conditions and periodic RVE boundary conditions, can not be used. That holds back the development and application of the corresponding homogenization method. On the basis of derivation of a new version of Hill’s lemma, this paper gives more versatile RVE boundary conditions in the strong form. In addiction, reasonable periodic boundary conditions are successfully constructed, too. The presented RVE boundary conditions satisfy the Hill-Mandel condition and basic assumptions of the average-field theory and thus can be applied in the homogenization methods for heterogeneous Cosserat continuum
2013 Vol. 34 (3): 259-265 [
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436
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266
Constitutive model of single crystal thermal finite deformation
A constitutive model for single crystal thermo-viscoplastic deformation is presented to simulate the thermal behavior of the single crystal. Based on the single crystal thermal kinematics, we consider the thermal decomposition of total deformation gradient and obtain an evolution equation for the elastic deformation gradient. An implicit approach to integrate the equation is adopted to ensure the numerical stability. Using this model, we can reveal the thermal effect to the stress-strain relation of single crystal during its deformation.
2013 Vol. 34 (3): 266-271 [
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272
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272
GENERALIZED THERMOELASTIC MODEL AND ASYMPTOTIC ANALYSIS FOR ELASTIC MEDIA WITH TEMPERATURE-DEPENDENT
Based on the Clausius inequality and L-S generalized thermoelasticity theory, the coupled model for the generalized thermoelasticity in an elastic media with temperature-dependent properties is established by the higher expansion of the free energy. The linear equations are reduced for the homogeneous and isotropic materials with the boundary subjected to thermal shock. In accordance with the transient behaviors of thermal shock, the asymptotic solutions of the temperature, displacement and stress for one dimensional problem are obtained via the Laplace transform and inverse transform and its limit theorem. Numerical simulation is conducted for a semi-infinite copper rod, the distribution of each physical field and the influence of the temperature-dependent properties on these thermoelastic response are obtained. The results show that the temperature-dependent properties have some influence on the locations, intervals and peak values of jumps, and it is notable that the influence on the temperature is very litter than that on the displacement and stress.
2013 Vol. 34 (3): 272-278 [
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279
Study on dynamic response of corrugated shells shooting structure
Abstract: With the LS-DYNA non-linear and dynamic finite program, the dynamic expansion process of corrugated pipe, the major composition of energy conversion in submunition dispersing, under uniform internal pressure was numerically simulated, and its regular behaviors of dynamic response were achieved. The influences of various factors on deformation law of corrugated pipe are particularly investigated. The rule of coupled deformation for the corrugated pipe, the dispersion rule of submunition under internal pressure and external bullet cluster with the simulation of interior ballistic dispersing process was studied. The result of numerical simulation is elementarily accord with experiments.
2013 Vol. 34 (3): 279-285 [
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286
Structural damage identification method based on strain energy equivalence index
In order to solve structural multi-damage identification problem, a damage detection method based on strain energy equivalence index is presented. First, the change of modal strain energy (MSE) before and after damage occurs and dissipation ratio formulas are given. Then, considering that the strain energy dissipation and the change of MSE should be equivalent, we deduced a quartic equation. Finally, four roots of the equation are obtained and a strain energy equivalence index is presented, which can conveniently calculate structural damage locations and extent. The simulation results demonstrate that the proposed strain energy equivalence index method can identify structural damage locations and extent with good accuracy and the identification precision of the proposed method is obviously better than that of modal strain energy dissipation ration method.
2013 Vol. 34 (3): 286-291 [
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292
Active control method of power flow and experimental research for frame structure based on wave method
To study power flow transmission and active control of the frame structure under the influence of disturbance, firstly, the kinetic model of frame structure is established by wave method and the accurate dynamic response is obtained, then power flow transmission of structure is determined. The power flow is used as the objective function, and we will get optimized control force magnitude and phase by optimization algorithm, which is applied to the frame structure. Ultimately, active control of power flow for frame structure is realized. Based on active control method of power flow for frame structure, the numerical analysis and experimental validation is made. The results show that the dynamic response results of frame structure by wave method are accurate and reliable; Active control method of power flow can efficiently reduce the jitter of the frame structure in the whole frequency domain by numerical calculation and experiment research, and it proves that active control of power flow by wave method is right and valid.
2013 Vol. 34 (3): 292-298 [
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305
Euler-Bernoulli beam formulation using multiwavelets based on the quintic Hermie spline function on the interval
The quintic Hermie spline function on the interval was adopted to formulate multiwavlets scaling functions for the boundary and the middle nodes of a three-node beam respectively. Then, based on the wavelet multiresolution concept, the multiresolution function bases for the approximate spaces of the element displacement were erected. After that, the principle of minimum potential energy was used to establish the beam equilibrium equations, thus a beam element was formulated using multiwavelets based on the quintic Hermie spline function on the interval. The practical example result shows that the accuracy of the element could be automatically adjusted by changing scaling level or grid partitioning, and be the same as the traditional beam element with the equivalent grid. Compared with other wavelet beam elements, this element possesses such advantages as to be more compact clearly, more definite physically and easier to understand.
2013 Vol. 34 (3): 305-310 [
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311
The identification method of critical information for rock brittle failure
The phenomena caused by rock brittle fracture can be divided into two types. One is related to the changes in physical-mechanical parameters and structual characteristics, which can be described as the rock fracture, reducing of bearing capacity and modulus, increasing of permeability and deformation, and the mutation of wave velocity parameter and resistivity. The another type is related to the releasing of energy and change of physical parameters, which is reflected as the increasing of AE, electromagnetic emission and infrared radiation. Experiment and theoretical rest is shown that the stress ratio between crtical point of brttle failure and and peaking point has a value range 70% to 80%, which has a value of nearly to 75%. From this research, one can use the cpmprehensive information source to indentify the critical point of brittle fracture.
2013 Vol. 34 (3): 311-319 [
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296
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