CRITICAL PLANE APPROACHES IN HIGH-CYCLE FATIGUE: ON THE DEFINITION OF THE AMPLITUDE AND MEAN VALUE OF THE SHEAR STRESS ACTING ON THE CRITICAL PLANE

Critical plane approaches are useful methods when designing against long-term fatigue of machine components made from metals. Somewhat surprisingly, the very basic problem of the evaluation of the amplitude and mean value of the shear stress acting on the critical plane is still not resolved satisfactorily for non-proportional cyclic loading conditions. In the present paper, existing proposals for solving this problem are briefly reviewed and their weaknesses highlighted. Then it is shown, through particular examples, that application of these proposals can lead to ambiguous results. Therefore, new definitions of the amplitude and mean value of the shear stress acting on the critical plane are formulated here. These new definitions are free from any ambiguity because they are based on the construction of the unique minimum-circumscribed circle to the path described by the shear stress on the critical plane. The centre of this circle defines the mean shear stress, whereas its radius provides the corresponding shear stress amplitude. The algorithm yielding this minimum-circumscribed circle is presented in some detail.     

波折腹板工形构件翼缘稳定性能研究

提出了研究波折腹板工形构件翼缘稳定性能的合理简化模型,探讨了翼缘弹性屈曲应力与翼缘名义宽厚比、腹板波形的关系;基于翼缘屈曲时可能出现的2种屈曲模态,分别解释了其发生机理并给出了相应的临界荷载计算公式;提出了2种屈曲模态的判断依据,通过一系列弹塑性分析考察了不同屈曲模态下构件承载力随宽厚比的变化特点.结果表明,屈曲模态Ⅰ对构件的翼缘稳定十分不利,应尽量避免.基于屈曲模态Ⅱ的屈曲应力,提出可用于工程设计的合理宽厚比限值.     

Determination of Elastic Characteristics of Structural Metals in Micro- and Macroelastic Strain Regions

Precision methods and devices for determining Young's moduli and transverse strain factors of structural metals in the range of microstrains (~10^-7) and strains corresponding to operating stresses are described. The accuracy of experimental results is adequate for solving both scientific (determination of second-order transitions in these metals) and practical problems.     

Numerical prediction of the effect of catalyst layer Nafion loading on the performance of PEM fuel cells

Numerical simulations are performed to investigate the effect on PEM fuel cell performance of Nafion loading in the catalyst layer. The investigation also considers variations of geometric parameters. A model that accounts for the volume fractions of Nafion, the solid catalyst particles, and the void space inside the catalyst layers is incorporated into a three-dimensional computational fluid dynamics code, capable of resolving three-dimensional mass, momentum, and species transport phenomena as well as the electron- and proton-transfer processes in a PEMFC. Numerical results are first compared with experiments, showing close agreement between predictions and measurements. A parametric study on the effects of Nafion loading and geometric parameters variation is carried out to evaluate the performance of PEMFC for various parameter combinations.     

Effect of stitching and weave architecture on the high strain rate compression response of affordable woven carbon/epoxy composites

In this study, experimental investigations on stitched and unstitched woven carbon/epoxy laminates under high strain rate compression loading are discussed. Stitched/unstitched laminates are fabricated with aerospace grade plain and satin weave fabrics with room temperature curing SC-15 epoxy resin using affordable vacuum assisted resin infusion molding process. The samples are subjected to high strain rate loading using modified compression split Hopkinson’s pressure bar at three different strain rates ranging from 320 to 1149 s⁻¹. Results are discussed in terms of unstitched/stitched configuration, fabric type and loading directions. Dynamic compression properties are compared with those of static loading. Failure mechanisms are characterized through optical and scanning microscopy.     

嵌入式系统中引导程序的实现

给出了基于ARM7嵌入式系统引导程序的实现流程，并针对嵌入式系统中目标文件的分布装载等技术难点进行详细分析。     

变频调速蝶阀

介绍了变频调速蝶阀的性能，分析了其组合结构特点，阐述了主要设计参数选取方法，论述了其应用状况。     

Determination of rock mass deformation modulus by means of traveling load tests—Part I: Theory of the traveling load test in an open pit

A new scheme named the Traveling Load Test is proposed to measure the macroscopic deformation modulus of the floor rock mass in an open pit, covering a volume of rock mass much larger than conventional loading tests. Facility of the test includes extra-large excavators as load-sources on the flat surface and high-resolution borehole tilt-meters installed in rock to detect the microscopic tilt induced by the load. Emphasis is given to the theory of deformation modulus determination, which is applicable to the field where the floor is fully covered by an accumulation of loose blocks of stone produced by blasting damage and/or stress relief. The relation between the induced tilt and the traveling load is formulated, and subsequently it is shown how the deformation modulus is determined by analyzing the induced tilt-loading distance curve, within acceptable engineering accuracy.     

整车振动试验台加载装置分析

介绍了整车振动试验台的加载装置 .对加载装置的横向干扰问题进行了分析 ,得出了补偿量的计算方法 .并对加载装置进行了运动分析 ,建立了速度和加速度的数学模型     

Solaris10操作系统在SUN V890服务器中的安装方法

钟吉太，岳淑华，杨志仁．Solaris10操作系统在SUN V890服务器中的安装方法，物探装备，2006，16（4）：298-300 SUN V890服务器具有强大的处理、解释功能，是在物探地震资料解释中起重要作用的高性能的工作站服务器。为了充分发挥SUN V890服务器的强大功效，必须为服务器安装Solaris操作系统，本文对Solaris操作系统在SUN V890服务器中的安装方法进行了详细地介绍。