锚栓群锚抗拉性能试验研究

通过对膨胀型锚栓、扩底型锚栓、普通化学锚栓及特殊倒锥型化学锚栓进行单锚、两锚、四锚和八锚的抗拉试验,研究了群锚抗拉的破坏模式及受力性能,并对群锚受拉承载力的试验值与计算值进行了比较分析.结果表明,锚栓群锚抗拉破坏状态主要有:混凝土锥体破坏、锚栓钢材破坏,承载力试验值与《混凝土结构后锚固技术规程》计算值基本吻合.     

复合材料波纹夹层圆柱壳设计及轴压性能

结构轻量化是航空航天发展的永恒主题, 波纹夹层圆柱壳作为常见的轻质结构形式, 在航空航天领域具有很大的发展空间。采用模具热压法, 制备出纵向和环向碳纤维复合材料波纹夹层圆柱壳, 其中芯子整体成型, 面板分瓣制备。采用经典板壳屈曲理论, 分析纵向和环向波纹夹层圆柱壳的轴压力学性能, 得到了欧拉屈曲、整体屈曲、局部屈曲和面板压溃4种失效模式下的极限载荷理论公式。绘制出结构的失效机制图, 直观显示出了失效模式与试件尺寸之间的关系。通过对纵向和环向波纹夹层圆柱壳的轴向压缩试验, 获得了结构的载荷-位移曲线及局部屈曲和面板压溃2种失效模式。结果表明:纵向波纹夹层圆柱壳的轴向承载能力及载荷/质量效率优于环向波纹夹层圆柱壳, 在一定范围内增加圆柱壳面板的厚度、减小圆柱壳的高度可提高结构的载荷/质量效率。      

The dynamic behavior of two collinear cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves

The dynamic behavior of two collinear cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves is studied using the Schmidt method for the permeable crack surface conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of the displacements across the crack surfaces. In solving the triple integral equations, the jump of the displacements across the crack surface is expanded in a series of Jacobi polynomials. It can be obtained that the stress field is independent of the electric field and the magnetic flux.     

Si对Ni基非晶合金玻璃形成能力及热稳定性的影响

研究Si对NiCuTiZrAl非晶合金的玻璃形成能力及热稳定性的影响。利用铜模铸造制备NiCuTiZrAlSi非晶合金,3.5%Si的添加显著改善非晶合金的玻璃形成能力。在DSC、DTA、XRD及TEM分析的基础上,利用SEM(EDS)技术对类金属Si提高非晶合金的玻璃形成能力及热稳定性进行深入分析。适量元素Si添加不仅可以延缓熔体中初生相Ni(TiZr)和(TiZr)(CuAl)2形成,而且可抑制元素O的有害作用,这为类金属提高非晶合金的玻璃形成能力提供有效证据。利用Kissinger方程进行不同含Si量的NiCuTiZrAl非晶合金晶化动力学研究表明,放热峰Tp处晶化激活能随着Si量增加而增大。     

Experiments and simulation of low-velocity impact characteristics on carbon fiber composite lattice core sandwich structures

Since composite sandwich structures are susceptible to low-velocity impact damage,a thorough characterization of the loading and damage process during impact is important.In the present paper,the low-velocity impact response of carbon fiber composites lattice structures is investigated by experimental and numerical methods.Impact tests on composite plates are performed using an instrumented drop-weight machine(Instron 9250HV)and a new damage mode is observed.A three-dimensional finite element model is built by ABAQUS/Explicit and user subroutine(VUMAT)to predict the peak loading and simulate the complicated damage problem.The numerical predictions are in good agreement with the experimental results.     

Buckling of carbon fiber composite pyramidal truss core sandwich columns

This paper deals with the theoretical prediction of global buckling loads for carbon fiber composite pyramidal truss core sandwich columns. Different from thin plate structures, transverse shear effect can not be neglected for sandwich structures. In addition, the attributes of the laminated face sheets are considered in the present paper. A zig-zag displacement approximation is made. Based on the principle of minimum potential energy, equilibrium equations and boundary conditions are derived via the variational method. The critical buckling loads under various boundary conditions are presented. In order to validate the reasonableness of the equivalent-core method, the strain energies stored in the actual discrete truss members and the equivalent continuous homogenous core layer are calculated respectively and compared, and a good agreement is obtained. The proposed analytical method is verified by comparing with the published theoretical predictions and experimental results.     

夹芯结构的设计及制备现状

由于夹芯结构具有比强度高、比模量大等众多优点,目前被广泛应用在航空航天等领域.从面板、芯子和面芯界面加强技术等三个方面对夹芯结构的设计和制备现状进行了介绍.重点对蜂窝夹芯结构、泡沫夹芯结构、点阵夹芯结构、格栅夹芯结构和整体夹芯结构等的设计和制备工艺以及为了提高面芯界面结合强度而不断被提出的包括Z-Pin,Stitch和Embedding等在内的面芯界面增强工艺进行了较为系统的介绍.     

大挠度功能梯度压杆的后屈曲分析

对一端固定一端自由功能梯度压杆的后屈曲问题进行了分析。依据组份材料的体积含量,假设材料的物性参数沿杆件的厚度按幂函数变化。基于Kirchhoff大变形理论,推导了大挠度功能梯度压杆后屈曲分析的控制微分方程和边界条件。采用微分求积法对所得控制微分方程和边界条件进行数值计算,得到压杆后屈曲时的自由端转角和自由端位移。分析了载荷、梯度指数和截面边长比对杆件后屈曲平衡路径的影响。     

材料内部存在初始应力条件下弹性张量的确定

With respect to small deformation gradient tensor,the displacement gradientmoduli Φ_(iLjM)~* at the reference system are introduced by taking into account the rela-tion of the first Piola-Kirchhoff stress tensor T_(iL) and displacement gradient tensor u_(jM)in the paper.Then the specific expression of Φ_(iLjM) is derived by the comparison of theexpansion terms of Helmholtz free energy H.Finally,the coefficients (?)_(iLjM) related toΦ_(iLjM) are obtained by using ultrasonic measurement and the elastic tensor C_(iLjM) whichdepends on (?)_(iLjM) and initial stresses in the reference system are given.     

正交各向异性复合材料圆筒中残余应力的分析

复合材料成型过程中,各种组分变形不协调,这样在复合材料内部就产生了残余应力。本文研究了轴对称正交各向异性复合材料圆筒中残余应力的分布,並且给出了轴向应力(σ_z)、径向应力(σ_r),环向应力(σθ)和剪应力(τ_zθ)的分布情况。为了减小材料内部残余应力的影响,本文以应变能最小为条件,提出了如何加外载来减小残余应力的影响。