Bi-prism-based single-lens three dimensional digital image correlation system with a long working distance: Methodology and application in extreme high temperature deformation test

As a novel three dimensional digital image correlation(3 D DIC) method, the bi-prism-based single lens(BSL) 3 D DIC method has been proposed and developed in recent years. Making use of a bi-prism, this method is able to perform a 3 D DIC measurement using only a single camera. Thus, the integration level of a BSL 3 D DIC system could be much higher than that of the double-camera3 D DIC system. In this paper, using a small-angle bi-prism and a camera with a longer focal length, a special BSL 3 D DIC system with a long working distance is designed for measurements in extreme environments. The principle of the system is first studied,and practical methods are then proposed for the system set-up and the determination of system parameters. Then, feasibility of the measurement system is verified by out-of-plane rigid-body translation tests. Finally, the BSL 3 D DIC system is proven to be capable of combining with a high-temperature testing instrument to perform deformation tests in a high-temperature environment of up to 1500°C.     

流水线联机故障自动检测系统设计

本文提出一种的联机故障自动检测系统,给出了该故障检测系统的总体设计结构,分析了其主要组成模块和实现的功能。针对其智能化的需求,首次将增量数据库技术应用于故障信息的存储和交互更新。有效地实现了检测系统的灵活、高效的工作模式。最后文章对联机故障自动检测系统的重要底层支撑模块——增量式数据库的实现进行了深入的分析和研究。     

卫星有效载荷力学特性有限元仿真

为保证卫星有效载荷仿真计算的可行性和精度、提高仿真效率,预测有效载荷在相应力学环境下的响应,用HyperMesh8．0划分整机的有限元模型网格,用MSC Nastran2005计算和分析有效载荷的过载特性、频率响应特性、冲击和随机振动．该方法对保证卫星有效载荷仿真计算的可行性和精度、提高仿真效率有重要作用;可以有效预测卫星有效载荷对力学环境的响应,较全面评估设计,进而指导改进设计．     

焊趾微观短裂纹成核及其早期扩展的寿命仿真

针对十字焊接接头,研究了焊趾微观短裂纹成核和早期扩展的行为.采用泰森多边形方法,建立了焊趾部位的一个边长为150 μm的代表性单元(RE),基于疲劳指标参量(FIP)的分布特性,构建了FIP与微观短裂纹疲劳寿命之间的联系,计算了微观短裂纹的成核及其早期扩展寿命.结果 显示焊趾微观短裂纹成核及其早期扩展的计算寿命与试验寿命数据较为吻合,表明了该种计算方法的适用性;微观短裂纹成核及其早期扩展的计算寿命均占总体疲劳寿命的比值较大,因此具有不可忽略的影响;受晶粒微观结构的影响,导致早期裂纹的扩展路径呈现明显的曲折形态.     

由两组力学实验曲线得到的启示

研究由拉伸实验和纯扭转实验得到σe—εe曲线有明显的差异的两个原因,其一为不均匀效应的影响,其二为Poisson效应的影响。论证不考虑材料的Poisson效应对拉伸等效应变的影响时,相当于使材料软化,致使σe—εe曲线落在真实的σe—εe曲线的右下方。在此基础上,应用正交流动法则和关联流动理论,合理考虑Poisson效应,推导可压缩材料的塑性增量本构关系,将之退化到不可压缩材料,可得著名塑性力学专家Hill给出的塑性本构关系。     

High-temperature fatigue crack propagation study of superalloy GH4169 by single-lens 3D digital image correlation

The characterization of fatigue crack propagation behavior is crucial for performance and reliability evaluation of aerospace materials. In this study, high-temperature (maximum: 650°C) fatigue crack propagation experiments of Ni-based superalloy GH4169 were conducted. The bi-prism-based single-lens 3D digital image correlation (BSL 3D DIC) technique was used to in-situ measure the displacement and strain fields near fatigue crack tip. Based on the deformation information, the mode I stress intensity factor range ΔK and the crack opening displacement (COD) were determined for characterizing the crack closure effect. As the major fatigue crack growth model, the parameters of modified Paris’ law were obtained based on the effective stress intensity factor range ΔKeff and the fatigue crack propagation rate (FCPR). Additionally, two kinds of J integrals, JP (path integral method) and JK (stress intensity factor K method), were used to evaluate the small-scale yielding approximation.