基于复合材料力学模型的生态复合墙体研究

生态复合墙体作为生态复合墙结构的主要受力构件,它是由生态复合墙板与隐形外框组成的墙肢或墙段。复合墙体构造上的特殊性及多种材料的使用,使其弹性常数不易确定,进而影响墙体抗侧刚度的计算。基于前期试验研究,针对墙体独特构造,结合复合材料力学理论,建立适用于生态复合墙体的弹性阶段模型——双向纤维单层复合材料模型,推导出墙体弹性模量及剪切模量实用计算公式,为生态复合墙体的实用抗侧刚度计算公式提供必要的参数;利用弹性力学对各向异性等效弹性板的抗侧刚度进行推导,理论计算与试验结果的对比分析表明:在生态复合墙体抗侧刚度计算中,复合材料力学简化模型具有实用性和有效性。

基于试验的节能砌块隐形密框墙体复合材料力学模型

该文在六片1/2比例节能砌块隐形密框墙体低周反复加载拟静力试验基础上,并结合节能砌块隐形密框墙体的特殊构造,建立了弹性阶段墙体的复合材料等效弹性板力学简化模型,其中包括两种正交各向异性复合材料计算模型,进而将墙体简化为各向同性的计算模型,给出了墙体弹性模量及剪切模量实用计算公式,为节能砌块隐形密框墙体的实用弹性刚度计算公式提供了必要的参数。将理论计算与试验结果进行对比分析,对墙体的弹性抗侧刚度的计算公式进行修正,提出了适合于节能砌块隐形密框墙体的弹性抗侧刚度的计算公式。结果表明:复合材料力学简化模型具有一定的理论依据和实用价值,能够满足实际工程计算需要。

多孔材料的力学模型和粘弹性性能研究

建立了多孔铜-铝-氧化铝复合材料力学模型.利用粘弹性理论和有限元分析方法,得到了多孔铜-铝-氧化铝复合材料的切变模量本构方程;得出了铜-铝-氧化铝复合多孔材料的压力与位移的关系、受力面的支反力与加载时间的关系是非线性关系,多孔铜-铝-氧化铝复合材料是粘弹性材料的结论;获得了铜-铝-氧化铝复合多孔材料的弹性模量为533.89MPa的结果.

发动机舱大开口口盖的结构设计和计算分析

飞机发动机舱是飞机结构的重要组成部分,考虑发动机的拆卸、安装通道,以及在日常飞行时,对发动机进行检查和维护的通道,常常需要对发动机舱进行大开口设计。研究大开口口盖的复合材料设计是航空工业发展的一项重要技术,利用复合材料的高比强度、比刚度和优良的耐腐蚀、耐疲劳特性以及可设计性,可以带来良好的减重效果和较高的结构效率。对复合材料夹心结构进行有限数值计算和冲击损伤分析,验证其用发动机舱大开口口盖采用复合材料结构设计的可行性,对以后飞机的大型口盖的结构设计有一定的指导意义。

MICRO MECHANICAL ANALYSIS OF 3-D WOVEN COMPOSITES

A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in transverse. The additional shearing introduced by bending of fiber yarn is considered. The method to determine the microstructure is also discussed. This model is applied to the analysis of a 3-D woven graphite/epoxy composite. Micro stresses of the cell are studied, and then macro modulus is obtained by employing the average method. The predictions agree well with experimental results.

INTERFACE DAMAGE ANALYSIS OF FIBER REINFORCED COMPOSITES WITH DUCTILE MATRIX

A cohesive zone model is employed to simulate the fiber/matrix interface damage of composites with ductile matrix. The study is carried out to investigate the dependence of the interface damage and the composite tensile strength on the micro parameters of the composite. These parameters contain fiber packing pattern, fiber volume fraction, and the modulus ratio of the fiber to the matrix. The investigation reveals that though the high fiber vo lume fraction, the high fiber′s modulus and the square fiber packing can supply strong reinforcement to the composite, the interface damage is susceptible in these cases. The tensile strength of the composite is dominated by the interface strength when the interface debonding occurs.

某高层建筑主楼弹塑性地震反应分析

介绍采用EPDA弹塑性分析程序对某高层建筑主楼进行罕遇地震下的弹塑性时程分析,计算结果表明结构满足“强柱弱梁”的原则以及“大震不倒”的设防要求。

INCLINED LAMINAL COMBINATION MODEL OF 3D BRAIDED COMPOSITES

As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the basic structure and the relationship between the braiding angle and geometric parameters of the fabric and fiber volume ratio are given in this paper based on two 3D braiding processes, namely, the four-step and the twostep ones. Several existing mechanical models to predict groperties of the 3D braided comPOsites are discussed and their shortcomings are pointed out herein. Then a new model called the inclined laminal combination model is proposed, which is based on the classical laminated plate theory and can predict the basic mechanical behavior of the two 3D braided composites with four-step or two-step braid. In the model, each yarn in the unit cell is regarded as an inclined laminate and then a 3D analysis is performed. It is found that the predicted mechanical properties of the 3D braided composites by the proposed model are compared well with the experimental data.

PREDICTION OF TEXTILE FABRIC REINFORCED COMPOSITE PROPERTIES BASED ON NODE INTERPOLATION CELL METHOD

Node interpolation cell method（NICM）is a micromechanics method employing the virtual displacement principle and the representative volume element（RVE）scheme to obtain the relationship between the global and the local strain.Mechanical properties of 2-D textile fabric reinforced ceramic matrix composites are predicted by NICM.Microstructures of 2-D woven and braided fabric reinforced composite are modeled by two kinds of RVE scheme.NICM is used to predict the macroscopic mechanical properties.The fill and warp yarns are simulated with cubic B-spline and their undulating forms are approximated by sinusoid.The effect of porosity on the fiber and matrix are considered as a reduction of elastic module.The connection of microstructure parameters and fiber volume fraction is modeled to investigate the reflection on the mechanical properties.The results predicted by NICM are compared with that by the finite element method（FEM）.The comparison shows that NICM is a valid and feasible method for predicting the mechanics properties of 2-D woven and braided fabric reinforced ceramic matrix composites.

Mechanical analysis of fixed geosynthetic technique of GRPS embankment

To overcome the deficiencies of conventional geosynthetic-reinforced and pile-supported (GRPS) embankment, a new improvement technique, fixed geosynthetic technique of GRPS embankment (FGT embankment), was developed and introduced. Based on the discussion about the load transfer mechanism of FGT embankment, a simplified check method of the requirement of geosynthetic tensile strength and a mechanical model of the FGT embankment were proposed. Two conditions, the pile cap and pile beam conditions are considered in the mechanical model. The finite difference method is used to solve the mechanical model owing to the complexity of the differential equations and the soil strata. Then, the numerical procedure is programmed. Finally, a field test is conducted to verify the mechanical model and the calculated results are in good agreement with field measured data.

A mesomechanical ductility model of SiC_p/Al composite

Based on tensile cracking of SiC_p and decohesion of the interface between SiC_p and Al matrix, a mesomechanical model for tensile deformation of SiC_p/Al composites was developed. The microcracks and multi-scale second phase particles were assumed to distribute homogeneously. A nonlinear quantitative relationship between tensile ductility and volume fraction of SiC_p was established based on the model. The tensile ductility values of 2xxx SiC_p/Al and 6xxx SiC_p/Al composites predicted by the model are in good agreement with the experimental values. The analysis of effects of multi-scale second phases on the ductility of the composites indicates that the ductility decreases with the increase of the volume fraction of SiC_p and precipitates in Al matrix and is almost independent of constituents and dispersoids.

An elastic mechanics model and computation method for geotechnical material

Internal friction characteristic is one of the basic properties of geotechnical materials and it exists in mechanical elements all the time. However,until now internal friction is only considered in limit analysis and plastic mechanics but not included in elastic theory for rocks and soils. We consider that internal friction exists in both elastic state and plastic state of geotechnical materials,so the mechanical unit of friction material is constituted. Based on study results of soil tests,the paper also proposes that cohesion takes effect first and internal friction works gradually with the increment of deformation. By assuming that the friction coefficient is proportional to the strain,the internal friction is computed. At last,by imitating the linear elastic mechanics,the nonlinear elastic mechanics model of friction material is established,where the shear modulus G is not a constant. The new model and the traditional elastic model are used simultaneously to analyze an elastic foundation. The results indicate that the displacements computed by the new model are less than those from the traditional method,which agrees with the fact and shows that the mechanical units of friction material are suitable for geotechnical material.

Three-Dimensional Thermal-Stress Analysis of Semi-infinite Transversely Isotropic Composites

By making use of the direct integration method,an exact analysis of the general three-dimensional thermoelasticity problem is performed for the case of a transversely isotropic homogeneous half-space subject to local thermal and force loadings.The material plane of isotropy is assumed to be parallel to the limiting surface of the halfspace.By reducing the original thermoelasticity equations to the governing ones for individual stress-tensor components,the effect of material anisotropy in the stress field is analyzed with regard to the feasibility requirement,i.e.,the finiteness of the stress field at a distance from the disturbed area.As a result,the solution is constructed in the form of explicit analytical dependencies on the force and thermal loadings for various kinds of transversely isotropic materials and agrees with the basic principles of the continua mechanics.The solution can be efficiently used as a benchmark one for the direct computation of temperature and thermal stresses in transversely isotropic semi-infinite domains,as well as for the verification of solutions constructed by different means.

A Simulation Software for the Prediction of Thermal and Mechanical Properties of Wood Plastic Composites

Modelling and simulation has become an important tool in research and development. Simulation models are used to develop better understanding of the internal properties and impact of various parameters on the final quality of the product or process. Simulation model reduces the number of experiments and saves the wastage of material, time and money and are widely used in automobile industry, aircrafts manufacturing, process engineering, training for military, health care sector and many more. Wood Plastic Composite （WPC） is a bio-composite made by mixing wood fibers and plastic granules together at high temperature by compression molding or injection molding. A large quantity of WPC is rejected due to poor quality and low mechanical strength. There is a need to improve the understanding of the wood plastic composites, with both theoretical and experimental analysis. The impact of various parameters and processing conditions on the final product is not known to the industry people, due to less simulation models in this field. A new simulation software WPC Soft is developed to predict the mechanical and thermal properties of WPC. The software can predict the mechanical and thermal properties of WPC. The simulation results were validated with the experimental results and it was observed that the predicted values are quite close to the experimental values and with the further refining of the model, prediction can be further improved. The present simulation software can be easily used by the industry people and it requires very little knowledge of computers or modeling for its operation.

Dynamic analytic model of mechanism with links fabricated from symmetric laminates

A four-bar linkage mechanism with links fabricated from symmetric laminates was studied. The mass matrix of the beam dement was obtained in light of the mass distribution characteristics of composite materials. The stiffness matrix of the beam element was derived from the constitutive equations of each layer and the relationship between the strain distribution and the node displacement of the beam element. The specific damping capacity of the beam element was analyzed according to the strain distribution of the beam element and the strain energy dissipation caused by vibration in each direction of each layer; and the damping coefficients were obtained according to the principle that the total energy dissipation of the beam element was equal to the work done by the equivalent damping force during a cycle of vibration, from which the damping matrix of the dynamic equations was obtained. Using the finite element method, the dynamic analytic model of the mechanism was obtained. The dynamic responses and natural frequency of the mechanism were obtained by simulation, respectively, and those of the simulation obtained by the proposed model were analyzed and compared with the results obtained by the conventional model. The work provides theoretical basis to a certain extent for the further research on nonlinear vibration characteristics and optimum design of this kind of mechanism.

Constitutive description for casting magnesium alloy involving void evolution

In order to investigate the effect of microvoids on the mechanical behavior of casting magnesium alloy,a spherical void-cell model of the material was presented.The velocity and strain fields of the model were obtained from the assumption that the material matrix is homogeneous and incompressible.The hardening and softening functions,which respectively reflect the deformation-hardening and void-softening behaviors of the material,were presented and introduced to an endochronic constitutive equation for describing the mechanical behavior of the material including microvoids.The corresponding numerical algorithm and finite element procedure were developed and applied to the analyses of the elastoplastic response and the porosity of casting magnesium alloy ZL102.The computed results show satisfactory agreement with experimental data.

Mathematical Model of Dynamics of Micropolar Orthotropic Elastic Thin Bars with Free Fields of Displacements and Rotations

In the present paper, initial-boundary value problem of plane stress state of micropolar theory of elasticity is considered for orthotropic material in the domain of thin rectangle. General hypotheses are formulated, which are the qualitative results of the asymptotic method of integration of the stated initial-boundary value problem. On the basis of the accepted hypotheses general applied one-dimensional models of dynamics of bending deformation of micropolar orthotropic elastic thin bars with free fields of displacements and rotations are constructed with and without consideration of shear deformations. With the help of the constructed models different dynamic problems of micropolar bars can be studied. Here concrete problems of free and forced vibrations of hinged supported micropolar orthotropic elastic thin bar are studied. Numerical analysis is done and specific features of dynamic characteristics of micropolar material are revealed. Particularly, it is shown that there is a frequency of vibrations of the micropolar bar that does not depend on bar sizes.

Two Kinds of Calculation Methods in Whole Process and a Best New Comprehensive Figure of Metallic Material Behaviors

Based on the viewpoint that there are similarities to the genetic principles in the mechanics and the engineering fields; based on data in some referents and author＇s theoretical approach, this paper is to consider the microscopic-damage and the macroscopic-damage behaviors of materials that are distinct differences, thereby to propose computing models and methods of subsection calculations in whole process; to consider the behaviors between the short cracks and long ones both of which are always continuous, thereby to propose some computing models and methods of the successive calculations. These computing models refer to formulas of the threshold sizes of cracks （or threshold values of damages）; the propagating rates of cracks; the predicting calculations of lifetime; Particularly, in which it provides a best new comprehensive figure that it could be including mid describing all problems mentioned above. So it may be as a bridge to link the traditional material mechanics, the material discipline and the modem mechanics on fatigue-damage-fracture; perhaps, it can also be as route diagram to guide designs and calculations to some materials and structures. Therefore, above works realize calculations of the strength problems, the growth rate of cracks （damages） mid prediction of lifetime in whole process that would have practical significances.

A Novel Method for the Fabrication of Granular Hydroxyapatite-bentonite Composite Adsorbents for the Removal of Pb2＋ from an Aqueous Solution

Granular HApB composite adsorbents, with dimensions of 4 mm × 4 mm, were prepared for the removal of lead from an aqueous solution. The effectiveness of the composites for Pb2＋ removal from an aqueous solution with different initial concentrations, adsorbent doses and reaction times were examined. The Langmuir isotherms, Freundlich isotherm models and pseudo-second order kinetic model were used in this analysis. It was found that the Langmuir model fitted the experimental data better than the Freundlich model, with a maximum adsorption capacity of 93.37 mg.g-1. The pseudo-second order kinetic model also fit the experiment data well with an adsorption capacity of 70.73 mg.g-1 after being reused for 3 times. Furthermore, the composites may possibly be used in processes for industrial water treatment.