钢丝绳中缺陷的描述方法

研究钢丝绳及钢丝绳中缺陷的描述方法.基于对钢丝绳结构和承载特性的分析,提出一个描述钢丝绳结构的矢量,这个矢量由6个结构参数构成,它们是股层号、股号、股的旋转角(简称股旋角)、钢丝层号、钢丝号和钢丝的旋转角(简称丝旋角).为了引申出缺陷的描述方法,定义钢丝绳中距离的广义度量;定义钢丝、钢丝绳、断丝和磨损,钢丝用8个参数描述,它们是上述的6个结构参数和新增加的两个参数,新增加的两个参数是丝旋角变动和钢丝直径;钢丝绳定义成钢丝的集合;断丝用上述的6个结构参数和新增加的两个参数描述,新增加的两个参数是断口宽度和钢丝直径;磨损用上述的6个结构参数和新增加的两个参数描述,新增加的两个参数是丝旋角变动和磨损比.以密封钢丝绳和六股钢丝绳为例,说明该描述方法的应用.实例表明,在新描述方法的支持下,钢丝绳中的缺陷可以被抽象地用数学语言进行描述.     

Evaluation model for multi-process capabilities of stranded wire

Stranded wire is the most important component of familiar mechanical equipment such as elevators, cable cars, and cranes. The quality of these products that are used on a daily basis are mainly affected by the tensile strength of stranded wire. In order to attain the purpose of economical design and a long life span of stranded wire, a less relaxation property of strand type is suitable for manufactured tools. Thus, the manufacturing industries of stranded wire need to reach the goals of high tensile strength and low relaxation. To ensure the required quality of stranded wire, the strand pull test and the long period relaxation test are two important quality assurance tests. There are three specific items of the tensile strength test that belong to the larger-the-better quality type. The quality type of the smaller-the-better is for the long period relaxation test. However, many existing methods are able to measure process capability for the product with a single quality characteristic although it cannot be applied to most products with multiple properties. Thus, the indices of C_pu and C_pl, for the larger-the-better and the smaller-the-better quality type respectively proposed by Kane [5], are quoted and combined to propose a new index to evaluate the quality of multiple characteristics of stranded wire in this article. The principle of statistics is then used to derive the one-to-one mathematical relationship of this new index and ratio of satisfactory production process. Finally, the procedure and criteria to evaluate the quality of stranded wire is proposed. This integrated multi-quality property capability analysis model can be used to evaluate the multi-process capabilities and provide continuous improvements on the manufacturing process of stranded wire.     

缓凝预应力筋包覆试验

在预应力钢筋上连续包裹一层缓凝砂浆是新型缓粘结预应力混凝土体系得以工程应用的关键.利用螺旋输送挤出、模具成型原理,开发出缓凝预应力筋包覆装置,并进行缓凝预应力筋包覆试验.基于流变学理论,分析缓凝砂浆连续包覆过程.理论和试验结果表明:要成功实现自动连续一次完成在预应力钢绞线上均匀密实包裹缓凝砂浆同时包覆塑料(密封砂浆),宾汉姆体的缓凝砂浆在螺旋输送槽和钢绞线与塑料护套形成的环形通道内必须完全处于一种流动状态,而保持流态的条件则是螺旋转数和包覆速度均满足临界值要求.     

基于高温铸坯蠕变规律的连铸坯幂函数连续矫直法

根据国内外近年来高温铸坯蠕变规律研究成果,建立了矫直区内铸坯变形的数学模型,由此推导出矫直区内铸坯连续矫直曲线方程。辊列按照该矫直曲线布置,完全满足高温铸坯蠕变变形规律。矫直区内的铸坯在中间段实现了等应变速率变化规律,起始段和末尾段实现幂函数形式的应变速率变化规律。利用实验辊列装置对该矫直曲线进行了实验研究,采用一种常温完全蠕变锡铋合金代替高温铸坯,对实验铸坯所受矫直力与铸坯应变进行测量,所测结果与理论计算结果相吻合。     

A steady-state combustion modelling of composite solid propellants

By depicting the transfer of heat and combustion reaction to take place within thin gas layers close to the propellant surface burning in a steady-state fashion, a mathematical equation has been deduced to describe the burning rate of solid propellant as a function of initial grain temperature and chamber pressure. It has been also assumed that chemical reaction could take place in premixing-diffusing zone but were carried out mainly in the reaction-flame zone. All these phenomena taken place in each zone of combustion have been assumed to be steady-state. In the present investigation, the equation, γ=k·(1/R(T _i +C))ⁿ. exp (-E _a/R(T _i +C)(P/z) is being presented and it is compared with experimental data. The proposed model has been tested and evaluated vis-a-vis strand burner data for three different propellants based on CTPB, and it has been found that the deviation of the computed burning rates from the measured rates ranged up to 2%.     

The response of wire rope strands to axial tensile loads—Part II. Comparison of experimental results and theoretical predictions

Carefully instrumented tests were performed on straight single steel strands of seven-wire construction subjected to axial loads and with various end restraints. The strands have a practical range of lay angles between 9.2 and 17.0° with core and helical wire diameters of 3.94 and 3.73 mm, respectively. A mathematical model of a strand was developed to explore the change of helix angle under load, Poisson ratio effects in wires, wire flattening under interwire pressure and the effect of friction between the core and helical wires. A companion article (Part II) [Int. J. Mech. Sci. 29, 621–636 (1987)] compares the theoretical predictions with previously published analytical work and with the corresponding experimental results reported in this article.     

A concise finite element model for three-layered straight wire rope strand

A concise finite element model (FEM) of three-layered straight helical wire rope strand under axial loads (tensile and torsional) is presented in this paper. Three-dimensional solid elements were used for structural discretization. The helical symmetry of the strand was used to establish accurate boundary conditions. Contact, friction and plastic yielding were also taken into account. For the global behaviour of wire rope strand, i.e. load vs. strain and load vs. torque (fixed-end) or load vs. strand twist rate (free-end), the finite element results showed better agreement with the experimental results of Utting and Jones (Journal of Strain Analysis for Engineering Design 1988;23(2):79–86) than those calculated using the analytical strand model of Costello (Theory of Wire Rope, 2nd ed. New York: Springer, 1997). In addition, the FE model allows the localised stress distribution to be determined. In particular, this model reveals the non-uniform stress distribution in the outer layer helical wires caused by the trellis point contact. This is particularly relevant in the fixed-end case, where the present analysis predicts an axial tensile rigidity in good agreement with the experimental observations (Utting and Jones), whereas Costello’s model predicts a significantly higher rigidity.     

A concise finite element model for pure bending analysis of simple wire strand

A concise finite element model for simple wire strand under pure bending is presented in this paper. Accurate bending symmetric boundary condition has been developed and applied to the periodic artificial cross-sectional end boundaries of the wire strand finite element model. To achieve better analysis accuracy, full three-dimensional solid elements were used for structural discretization. For the global behaviour of the wire strand, i.e. bending moment vs. bending curvature, the finite element results showed good agreement with the analytical elastic strand model of Costello (Theory of wire rope, 2nd ed. New York: Springer-Verlag; 1997) in elastic loading regime. Furthermore, the finite element model can predict the detailed progressive nonlinear plastic behaviour of the wire strand.     

Application of confocal laser scanning microscopy to analysis of H2O2-induced DNA damage in human cells

Confocal laser scanning microscopy (CLSM) offers improved depth discrimination and spatial resolution to the analysis of biologic samples. We demonstrate in this paper that such technology is valuable in examining DNA single-strand breaks in human cells. The single-cell-gel (SCG) assay is a new technique for measuring DNA strand breaks in individual cells. Cells embedded in lowmelting-point agarose are treated with varying concentrations of hydrogen peroxide to induce DNA strand breaks. Following cell lysis and alkaline electrophoresis, which enables single-stranded break detection, analysis of the resulting “comets” provides an accurate method of comparing changes in DNA migration patterns, which have been shown to reflect the DNA damage levels. A statistically significant difference (p < 0.01) in single-stranded DNA damage levels was detected in cells exposed to hydrogen peroxide concentrations as low as 10 nm for 2 min. LSM analysis of the SCG technique allows rapid, sensitive and reproducible quantitation of single-stranded breaks of cellular DNA.     

Statistical methods for in situ hybridization: identification of autoradiographically labelled cells and structures

In situ hybridization experiments frequently use autoradiography to identify labelled structures. Ideally, labelled cells will be overlain with a dense accumulation of particles, allowing one to discriminate them from unlabelled cells easily. However, if noise is high or the density of labelling is low, it can be difficult to distinguish bona fide labelling ‘by eye’. In such situations, labelled cells could be overlooked. This paper evaluates two statistical solutions to this problem: (1) a parametric method proposed by Hashimoto and co‐workers and (2) Wang & Wessendorf's non‐parametric method using contingency testing (i.e. the chi‐square or Fisher's exact tests). The Hashimoto method determines the mean and standard deviation of the density of background labelling, using sense‐strand controls as the source of background levels. Cells labelled at densities greater than two standard deviations above the mean (P < 0.0455) are defined as significantly labelled. Contingency testing determines whether the grain density over a cell is significantly higher than that over the remainder of the image. When compared, the two methods gave similar results. The Hashimoto method may be more sensitive if most cells are labelled but contingency testing requires no assumptions about the uniformity of non‐specific labelling.     

输电导线机械破损的红外检测与故障诊断

借助红外辐射理论,建立了破损导线的热辐射场和红外传感器对其输入响应的模型。研制和开发了一种新型的导线破损的红外检测与故障诊断仪。提出了基于峰峰值邻域特征参数的综合识别判据在线识别断股故障信号以及用二进小波对突变信号奇异性检测来离线识别断一股信号和股波信号,这种故障识别方法既可以提高故障识别效率又可以保证故障识别的精度。     

Tumor necrosis factor-alpha induced DNA cleavage in human articular chondrocytes may involve multiple endonucleolytic activities during apoptosis

Apoptosis has been documented in chondrocytes both in the growth plates of young, healthy cartilages and in osteoarthritic cartilages; little, however, is known about apoptosis in chondrocytes of normal adult articular cartilage. For the current study, apoptosis in adult chondrocytes was evaluated by labeling DNA fragments using the ISEL in situ end labeling of 3'-recessed strand breaks) or TUNEL (5'-recessed or blunt-ended strand breaks with terminal deoxynucleotidyl transferase-mediated nick end labeling) techniques in primary cultures of chondrocytes in monolayer. Apoptosis was induced in the chondrocytes by either Tumor Necrosis Factor alpha (TNF alpha), Interleukin 1-beta (IL-1 beta), or anti-Fas antibody but only after 48 hours in culture. At 4 and 24 hours, there was no detectable DNA fragmentation. With TNF alpha, IL1 beta, and anti-Fas antibody, chondrocytes show evidence of at least two types of DNA strand breaks within the same cell (as assessed by simultaneous labeling with ISEL and TUNEL). Therefore, some pathways leading to apoptosis in chondrocytes appear to involve more than one type of endonuclease activity. When the chondrocytes were cultured as explants with the articular matrix intact (ex vivo), neither IL-1 beta, TNF alpha, the anti-Fas antibody, nor fibronectin fragments were able to induce apoptosis in the chondrocytes. In normal human adult cartilage that was untreated and uncultured (in situ), DNA fragmentation was undetectable; however, a significant number of chondrocytes in osteoarthritic cartilage did contain strand breaks. These data suggest that apoptosis occurs in chondrocytes in which the matrix has been disrupted experimentally or destroyed by the osteoarthritic disease process. The results of these studies suggest that the ECM may be an essential survival factor for chondrocytes.     

Effects of Abrasive Types on Grinding of Chopped Strand Mat Glass Fiber-Reinforced Polymer Composite Laminates

A grindability study of chopped strand mat glass fiber reinforced polymer laminates (CSM GFRP) has been carried out to evaluate the effects of abrasive types on grinding force ratio and area roughness at varying grinding parameters such as speed, feed and depth of cut. Performances of alumina (Al₂O₃) and cubic boron nitride (CBN) wheels were compared. Both wheels delivered the maximum grinding force ratios at low speed, high feed and low depth of cut. Alumina wheel produced smoother surface when grinding at low speed, low feed and high depth of cut. CBN wheel, on the other hand, gave smoother surface at high feed and low depth of cut conditions, regardless of speed. With CBN wheel, it is likely that a single grinding condition exists that maximizes grinding force ratio and minimizes area roughness. The findings indicate that CBN wheel exhibited higher grinding force ratio than alumina grinding wheel in general. CBN grinding wheel also outperformed alumina grinding wheel by producing smoother ground surface in most cases.     

Methylamine tungstate and tannic acid in fixation for high contrast and preservation of fine structure: application to myxomycete plasmodia

The effects of several fixation methods for electron microscopy were compared, using macro-plasmodia of Badhamia utricularis (myxomycete) as test objects. A brief osmium tetroxide (Os) exposure followed by a mixture of glutaraldehyde (GA) and tannic acid (TA) with subsequent treatment with methylamine tungstate (MAT) overcame most commonly encountered difficulties in fixing these structures. Lead staining of the sections was necessary to bring out the range of densities inherent in the delicate detail of ground cytoplasm, membranes, and organelle structure retained by Os/GA-TA/MAT. Microfilaments were well preserved with good contrast and little evidence of breakage. Although GA as the initial fixative gave good organelle preservation, Os pretreatment was required to prevent artefactual changes in plasmodial strand morphology. The several fixation procedures tested gave pronounced differences in mitochondrial appearance, in some cases giving a negative stained appearance to the cristae. Some advantages in interpretation may result from such reversed contrast. The high contrast and range of densities achieved following the Os/GA-TA/MAT schedule permitted routine use of thin (silver-grey) sections, thereby potentially increasing the resolution.     

捻距单股钢丝绳侧丝与股芯的应力场研究

基于SolidWorks-Ansys平台,以IWRC1×7线接触单股钢丝绳为研究对象,在侧丝与股芯之间建立一种新的凹凸匹配小面接触模型,对已建立的有限元模型施加合适的边界条件和载荷,对奇偶捻距侧丝以及多捻距侧丝与股芯进行应力场分析,从而得到侧丝以及绳股在单向拉伸载荷作用下各自的应力场分布。分析表明:捻距数目为偶数的侧丝应力集中的最大应力值要小于捻距数目为奇数侧丝的最大应力值;多捻距单股钢丝绳应力最大值发生在施加载荷端第一个捻距中部,一个捻距的应力最大值明显大于多个捻距的应力最大值,并且随着捻距数目的增加,最大接触应力值成波浪式下降趋势。     

三角股钢丝绳应力平衡分析及提高捻制质量的研究

实施以应力平衡为主,消除应力为辅取代传统单一的消除应力的生产方式。研究发现三角股钢丝绳捻制应力产生的关键环节是三角股的捻制,利用捻制三角股的特殊装备,采取工字轮后翻身的方式,促成钢丝的正向预应力来平衡捻股产生的负向捻制应力,实现三角股捻制应力的有效控制。应用盘式成绳预变形器,采用一次预变形工艺替代传统两次预变形的生产方式,使三角股钢丝绳六股变形率一致性得以稳定提高。     

钢丝绳弱磁探伤数值模拟及实验研究

在对绞线钢丝绳3D建模的基础上,采用有限元技术,分析了弱磁励磁状态下,钢丝绳复杂表面的磁场分布;对钢丝绳周围空气中的漏磁场矢量进行了仿真,研究了缺陷对钢丝绳表面及空间漏磁场分布的影响。仿真分析结果表明:在无缺陷状态下,钢丝绳周边空气中的漏磁场分布与其绳股形状相对应,其圆周方向的漏磁场呈周期性变化,周期为绳股节距;当缺陷存在时,漏磁场分布的周期性被破坏,且幅值大幅增加。依据理论分析结果,搭建了基于弱磁励磁的钢丝绳无损探伤实验平台,得到了不同断丝缺陷的漏磁场实测波形,实验结果验证了仿真分析结果的正确性。     

Validity and limitations of linear analytical models for steel wire strands under axial loading, using a 3D FE model

In the field of cable modeling, many models have been proposed to describe the mechanical behavior of simple straight strands under axial loading, and the predictions of these models have been compared to experimental data when available. However, the validity domain of these models has not been evaluated yet because the experimental results reported in the literature are very limited. This problem is addressed here, the results from nine linear elastic models of a 6+1 wire single layered strand (simple straight strand) subjected to static axial loads being compared with values from 3D finite element modeling. The analytical models are shown to give satisfactory estimations of the elastic stiffness constants for lay angles below 20°.     

预应力钢绞线中超声导波声弹性效应的试验研究

钢绞线中应力损失直接威胁到预应力结构的整体安全,实现钢绞线中预应力的无损、在役测量在工程中显得十分重要。对基于超声导波技术的钢绞线中的预应力测量方法进行理论分析和试验研究。根据波动理论和声弹性理论,得到不同应力状况下钢绞线中纵波和横波波速,分析建立钢绞线中最低阶纵向模态L(0,1)群速度与钢绞线承载的应力之间的对应关系。采用自行研制的磁致伸缩传感器在不同应力状态下公称直径17.80mm的7芯钢绞线上进行超声导波L(0,1)模态的激励接收试验。试验测定不同应力状态下钢绞线中L(0,1)模态导波的群速度,得到实际中L(0,1)模态的群速度和应力之间的关系曲线。结果表明,应力在0.5GPa以上时,钢绞线中L(0,1)模态的群速度会随着应力增大呈近似线性下降,与理论分析结果较为吻合。这为超声导波应用于钢绞线预应力大小的测量奠定了基础。     

Novel apparatus to measure hyperthermal heavy ion damage to DNA: strand breaks, base loss, and fragmentation

We have developed a novel apparatus that allows us to irradiate nonvolatile organic films of high mass (1-100 microg range) spread out over a large surface area (42 cm(2)) with low energy (kT-100 eV) heavy ions and to quantitatively analyze the film substance via standard biochemical techniques afterwards. Here we discuss the details of the apparatus and method and show that it allows us to measure substantial damage to double stranded DNA molecules (plasmids) and its fundamental subunits induced by heavy ions with unprecedented low energies, i.e., 2.5 eV/amu; these energies correspond to track end energies of stopping ions or secondary ions created along primary ion tracks. We find that hyperthermal Ar(+) ions interacting with plasmid DNA will lead to the formation of single and double strand breaks, as well as fragmentation of nucleosides, which also involve chemical modifications and site specific rupture along the N1-C1 glycosidic bond, resulting in base release. In cells, such localized clustered damage will enhance the severity of DNA strand lesions, thus making them harder to repair.