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2010 Vol. 31, No. 1
Published:
论文
1
Micromechanics model for the deform behavior of Nanocrystalline materials
Nanocrystalline (NC) materials can be treated as composite materials consisting of grain and grain boundary two phases. In this paper, the incremental stress-strain relation is derived from the view point of energy balance. Finally, the stress-strain relation of different grain sizes is obtained, and also applied in pure copper under uniaxial tension. Also the effects of grain shape and statistical distribution of grain sizes on the stress-strain relation are discussed, and the results predicted by the present model are compared with experimental data.
2010 Vol. 31 (1): 1-7 [
Abstract
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651
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8
A New High-temperature Compliance Method and Fatigue Crack Growth Behavior of Nickel-chromium Alloy Welding Materials
The key problem for fatigue crack growth rates testing of metallic materials at high temperature is how to measure crack length of a compact tensile (CT) specimen accurately. A new compliance method based on the FFCT specimens at high temperature was developed, and the calculation of the real-time crack length for a CT specimen which contains two different materials was also studied using finite element analysis. According to the new compliance method, a series of fatigue crack growth rates tests for nickel-chromium alloy welding materials at room temperature and 350℃ were carried out. The results show that, the new compliance method can be commendably used for fatigue crack growth rates tests at high temperature. For a CT specimen with layered configuration, its equivalent elastic modulus is affected by the elastic modulus ratio b, height ratio m and crack length a, and it has somewhat difficult to get a explicit expression of the crack length. A developed correct method for the calculation of real-time crack length is proposed, and it presents a nicer precision. The parameters of C and m in the Paris formula vary inversely with increasing temperature. For welding rod and wire, the values of C increase and the values of m decrease, but for welding strip the change of the two parameters is reversed. The crack growth resistance of welding strip is obvious lower than the other two welding materials at 350℃. The crack growth curves of the three welding materials have a point of intersection at room temperature and 350℃.
2010 Vol. 31 (1): 8-15 [
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1292
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16
Evaluation of Asphalt Mixture Fracture Resistance Using the J-Integral
Asphalt mixture is a heterogeneous material composed of aggregates, binder and air voids, which is always treated as a kind of visco-elastic material. The mechanistic behavior is between elastic and plastic. So evaluation of asphalt mixture fracture resistance may be more plausible using elastic-plastic mechanics. J-integral theory can avoid the complicated stress-strain field of the crack tip, has distinct physical meaning and can effectively evaluate the fracture resistance of the asphalt mixture. In this study, the fracture toughnessJC was conveniently determined from load-deformation data of a simple three –point bending fracture test using notched semi-circular specimens. To evaluate the effect of the asphalt mixture material properties on the variation of JC, three kinds of mixtures with different gradations were performed by adopting the semi-circular bending test method in a MTS testing system. Based on the digital image processing techniques, the Finite Element Model was constructed to simulate the test configuration. The numerical results were compared and analyzed with the experimental results. Results suggest that the fracture toughness JC could be used as a effective indicator to evaluate the fracture resistance of the asphalt mixture.
2010 Vol. 31 (1): 16-22 [
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632
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717
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23
Study on the Response of a Composite Plate Improved by using the pseudo-elastic of Shape Memory Alloy Subjected to Low-Velocity Impact
2010 Vol. 31 (1): 23-31 [
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594
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32
RIGID-FLEXIBLE COUPLING DYNAMIC ANALYSIS OF A MICRO BEAM CONSIDERING SIZE EFFECT
Abstract: Many micro experiments have shown that the mechanical properties of materials at micro scale are size dependent. The dynamics of a rigid-flexible coupling system consisting of a rotating hub and a flexible micro beam is investigated in this paper. The dynamic characteristic of a micro beam is analyzed theoretically using couple stress theory (Cosserat theory). The governing equations of motion with the dynamic stiffening terms(referred as the first-order approximation coupling model) and the size effect term for this system are derived from Lagrange’s equations. Compared with proposed mode1，the traditional zero—order approximation model can not describe the dynamics of micro beam correctly when the hub is in high rotation speed. The size effect results in the descending of vibration amplitude and the increasing of vibration frequency of the micro beam..
2010 Vol. 31 (1): 32-39 [
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628
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543
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40
An assumed stress method for zero-energy mode suppression in hybrid finite elements
A set of simple deformation modes that can be used to describe the arbitrary deformation for hybrid elements are directly derived from the element displacement field. It is shown that the nonzero deformation mode appears to be kinematic when it is orthogonal to all the assumed stress modes. Thus the spurious kinematic mode of a given element can be easily determined and suppressed by using the proposed simple deformation modes. Based upon the orthogonality relationship between the initial stress modes and the simple deformation modes, an assumed stress method is presented and the related systematic procedure is illustrated in details. Since the stress modes given by iso-function method are adopted here to derive the initial stress modes, one can find the necessary stress modes to represent the special stress distribution for different problems and the corresponding hybrid element is guaranteed from hour-glass modes. In the numerical examples several assumed stress fields for 2D-4 node and 3D-8 node elements are constructed by the proposed method and the results show that the method is very effective.
2010 Vol. 31 (1): 40-47 [
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677
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48
Damage Detection in Rod from Measured Dynamic Responses
In this paper, finite element analysis is used for the forced vibration analysis of the rod structure. The dynamic response sensitivity with respect to the physical parameter (elemental tensile stiffness) is then derived. In the inverse analysis, the local damages in the rod are identified from dynamic response sensitivity-based finite element model updating method. It is found that the local damage(s) can be identified successfully from several dynamic response measurements. The effect of artificial measurement noise on the identified results is also discussed. Numerical simulation shows that the proposed method is insensitive to the measurement noise and with very good accuracy. And it has the potential for practical application.
2010 Vol. 31 (1): 48-52 [
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599
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53
Buckling analysis of rectangular plates under parabolic edge compressions in Hamilton system
The distribution of in-plane stresses and buckling of thin rectangular elastic plates with all edges simply supported (SSSS), under nonlinearly distributed in-plane loadings along two opposite edges are studied by using the Hamilton system of elasticity and Galerkin method. Based on the Hamilton system of plane elasticity in a rectangular domain, the general solutions of the in-plane stress distribution in terms of undetermined constants corresponding to the zero and nonzero eigen-values are obtained by using the symplectic eigen-solution expansion method. After applying all stress boundary conditions, the formulae determining the in-plane stress distribution in a thin rectangular plate under parabolic distributed compressive edge loads along two opposite sides are derived. Due to the complexity of the in-plane stress distribution, it is impossible to obtain analytical buckling load for a simply supported plates under parabolic edge compressions. Therefore, the Galerkin method is employed for obtaining the buckling loads of rectangular plates with various aspect ratios. The present results agree very well with existing DQ (differential quadrature) data confirms the validity of the proposed method. Based on the results reported herein, one may conclude that the symplectic eigen-solution expansion method could provide a new way for obtaining in-plane stress expressions of thin rectangular plates subjected nonlinearly distributed in-plane edge loadings.
2010 Vol. 31 (1): 53-59 [
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667
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598
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简报
60
A HYBRID-STRESS FEM FOR ELLIPTICAL INCLUSION PROBLEMS
This paper presents a novel hybrid-stress finite element method for solving elastic fields around elliptical inclusions. A super polygonal-sided element containing an inclusion is constructed to reflect elastic behavior around the inclusion in terms of the variational principle of modified Hellinger-Reissner functionals. Displacement and stress fields in the element are expressed as complex series with Laurent series and Faber series by using the Muskhelishvili complex potential method and the conformal transformation technique. The super element is in conjunction with standard 4-node hybrid-stress elements to establish a new hybrid-stress finite element method. Benchmark example in the paper shows present method is rather general and efficient, as well as yields numerical results with higher accuracy and fewer elements. As an extended application of the method, an infinite isotropic plate containing two inclusions is analyzed under remote tension load. Effects of two inclusion span and elastic stiffness ratio on stress concentration coefficient are also discussed.
2010 Vol. 31 (1): 60-66 [
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597
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67
Vibration analysis of multi-span fluid conveying pipe with wave propagation method
A wave propagation method for vibration analysis of multi-span fluid conveying pipe that based on Timoshenko beam model is presented in this paper. By imposing the continuity and force balance condition, the wave reflection matrices are obtained for clamped supported end, simply supported end and free end respectively. The recursive algorithms are proposed for reflection matrices of intermediate supports. The frequency characteristic equation is deduced by using wave-train closure principle for the pipe supported at two ends. Finally, the present method is applied to calculate the first five natural frequencies of a seven span, 40 meters long pipe at four different cases. The results show that the proposed method is suitable for computer coding and has a high degree of accuracy.
2010 Vol. 31 (1): 67-73 [
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654
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791
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80
Stress analysis of Anisotropic finite thin plates with elliptical holes
Using the complex potential method in the bending theory of elasticity for anisotropic body, the stress distribution in a finite laminate containing the elliptical holes is proposed with the help of Faber series expansion. The effects of parameter are studied in detail. Some conclusions are drawn.
2010 Vol. 31 (1): 80-85 [
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619
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562
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86
RESEARCH ON UNCERTAIN MULTI-OBJECTIVE OPTIMIZATION METHOD BASED ON INTERVAL
Abstract：A new uncertain multi-objective optimization method is developed based on a nonlinear interval number programming(NINP) and an interval analysis method. Based on order relation of interval number and possibility degree of interval number, the uncertain multi-objective optimization is transformed into a deterministic non-constraint multi-objective optimization in terms of a penalty function. To improve the optimization efficiency, The quadratic polynomial response surface approximation is created based on the Latin Hypercube Design(LHD) .the NINP method is combined with an approximation to form an efficient uncertain multi-objective optimization method. Pareto optimal set is proposed. Two numerical examples are presented to demonstrate the effectiveness of the present method and practicability of the project.
2010 Vol. 31 (1): 86-93 [
Abstract
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633
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673
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94
结构损伤的非概率区间识别方法
基于结构时域加速度响应，利用区间分析方法对具有外界激励和测量数据不确定性的结构系统进行损伤识别。不确定性量被处理为有界区间数，基于参考有限元模型和被测加速度响应，经过提出的两步模型参数的区间修正方法分别得到了未损伤和损伤结构区间模型，进而通过定义的PoDE（Possibility of Damage Existence）确定了结构各单元的损伤可能性。最后以十杆平面桁架系统为例，对区间方法与概率方法的损伤识别结果进行对比，讨论了损伤程度和不确定度对识别结果的影响，结果表明了本文方法的可行性与有效性。
2010 Vol. 31 (1): 94-100 [
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613
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661
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101
Study on the multiaxial fatigue life prediction model based on the critical plane approach
Based on the critical plane approach, the drawbacks of the WB model are analyzed. It is discovered that, the normal strain excursion between adjacent turning points of the maximum of shear strain cannot reflect the effects of the additional cyclic hardening well; in the meantime, the empirical constant contained in the WB model is a life-correlated parameter which cannot be completely determined by the tensional and torsional fatigue limit. In addition, a new multiaxial fatigue damage parameter is developed to overcome the drawbacks of the WB model. The new damage parameter integrates the strain parameter with the energy parameter which the normalized stress range is used, and moreover, a new stress-correlated factor is introduced to account for the additional cyclic hardening which were caused by the non-proportional loading. It is convenient for engineering application because of no empirical constants in this parameter.
2010 Vol. 31 (1): 101-108 [
Abstract
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599
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533
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