光弹性—数字散斑相关混合法在光弹条纹主应力分解中的应用

光弹性法是研究结构内部应力分布问题的一个有效方法.光弹性实验中,通常可以方便地得到等色线条纹图.确定了等色线条纹级数以后,为获得平面模型中任意点的应力完全解,需要借助其它方法给出一个补充方程.本文将光弹性法与数字散斑相关法相结合,提出一种用于光弹性法分离主应力的新方法:光弹性-数字散斑相关混合法.在理论研究的基础上,设计了光弹性-数字散斑相关混合法实验系统,并通过相应的三点弯曲实验对该方法和实验系统的有效性做出分析和论证.该研究为光弹全场应力分解以及动态光弹性-数字散斑相关混合法提供了理论和实验基础.     

Photoelastic Stress Analysis by Use of Hybrid Technique and Fringe Phase Shifting Method

0Introduction Photoelasticityisanopticalmeasurementmethodforstressanalysis.Itcanperformwhole field measurementduetotwo dimensionalsignalprocessingoflight.Alsoitcanperformnon contact measurementbecauseoftransmissionorreflectionoflightonaspecimen.Photoelast…     

The application of evolutionary and maximum entropy algorithms to photoelastic spectral analysis

Over the past 10 years, spectral analysis has been shown to have the potential to be a reliable means of automating photoelasticity. However, the four methods of analyzing the spectra that have previously been proposed are slow and, in some cases, inaccurate. This paper describes three new methods for spectral analysis based on the maximum entropy method, a genetic algorithm and a memetic algorithm. Thirty-five spectra for known fringe orders were recorded and used in testing the four existing methods and the three new ones. It was found that the new methods were all considerably faster than the existing methods, although less accurate than the best existing method. By combining the maximum entropy method with either the genetic algorithm or the memetic algorithm, spectra could be analyzed up to 30 times as fast as they could with any of the existing methods and with comparable accuracy.     

Theoretical analysis,numerical calculation and experimental measurement of transient elastic waves in strips subjected to dynamic loadings

In this study, the transient response of an elastic strip subjected to dynamic in-plane loadings on the surface is investigated in detail. One of the objectives of this study is to develop an effective analytical method for determining transient solutions in a strip. By applying Laplace transform, the analytical solution in the transformed domain is derived and expressed in matrix form. The solution is then decomposed into infinite wave groups in which the multiple reflected waves with the same reflection are involved. Each multi-reflected wave can be identified by a coding method and be verified by the theory of generalized ray. The inverse transform is performed by using the well-known Cagniard method. The transient solutions in time domain for stresses and displacements are expressed in a closed form and are discussed in detail by an example. The experimental results show that the early time transient responses of displacements on the surface agree very well with the numerical calculations based on the theoretical solutions.     

列车分布式吸能系统的波传播特性和参数分析

建立了考虑车厢中弹性波传播影响的列车分布式吸能系统的简化理论模型。基于一维应力波理论,对碰撞过程中各吸能器的响应进行了理论分析,得到相关的控制方程并求解。观察到各吸能器界面上典型的阶段性、平台样的速度响应,并分析了其机理,进而对如何合理设置和排布吸能器进行了分析。结果表明:对于相邻的吸能器,碰撞前端吸能器的压垮强度应高于后端,否则后端吸能器无法同时发挥作用;各吸能器的平台应力的大小和排布是决定吸能系统作用效果的控制参量,能够决定各吸能器的吸能时长和吸能总量。具体分析了相邻吸能器的平台应力分布对系统吸能性能的影响,得到了在所研究的情况下使总吸能量最大的优化设计参数。该研究可为列车分布式吸能系统的优化设计提供理论指导。     

碳纤维约束高强混凝土圆柱压弯构件非线性全过程分析

为分析塑性铰区碳纤维约束高强混凝土圆柱的抗震性能,编制了可得到荷载-位移曲线软化段的非线性全过程分析程序,保护层和箍筋约束混凝土采用Mander本构模型,碳纤维约束混凝土采用ACI 440.2R-08给出的本构关系,将程序计算结果与试验结果进行比较,两者吻合较好;利用该程序分析了轴压比、混凝土强度、碳纤维包裹长度及层数、纵筋配筋率等参数对碳纤维约束混凝土圆柱荷载-位移关系的影响规律,结果表明:当轴压比超过0.55后,柱构件的水平承载力开始降低,柱的破坏形式由延性的受拉破坏向脆性的受压破坏转变;剪跨比大于3的圆柱,碳纤维在塑性铰区包裹长度大干1.2倍柱直径时,即可达到与全柱包裹基本一致的效果;对混凝土强度为50 MPa～80 MPa的高强混凝土圆柱,以包裹3～4层碳纤维为宜;随着纵筋配筋率的增加,柱的水平极限承载力及延性均有所提高.