力学环境约束下剪切销可靠性分析及优化设计

剪切销是火工装置关键部件,其可靠性不仅表现为点火作用下可靠剪断,还表现为受力学环境激励不发生断裂。本文中以多项式混沌展开方法为基础,建立了力学环境约束下的剪切销分析模型,结合序贯优化与可靠性分析方法,提出了剪切销可靠性优化设计的思路。以某型火工作动装置为应用实例,依据实用的力学环境,进行了剪切销可靠性分析及优化设计,揭示了设计参数与力学环境之间的关系,并获得了影响可靠性的关键参数。最后,开展了优化后的火工作动装置实验测试,结果佐证了优化设计的有效性。     

Stresses around pin-loaded hole in composite laminates using direct boundary element method

This study is concerned with stresses around a pin-loaded hole in symmetrically stacked composite laminates of finite size using a two-dimensional direct boundary element method. Effects of friction and clearance between the pin and hole edge on the stresses are accounted for. Also geometric compatibility and force constraint between the pin and the plate are enforced. A new relation for geometric compatibility is proposed. Stress distributions and the contact angle with slip and no-slip regions around the pin-loaded hole corresponding to various parameters are investigated. Some interesting results are obtained. The present method is effective and simple to use which can be implemented with a personal computer.     

冲击作用下快响应光纤探针研究

为满足在特殊的环境条件下对冲击波速度、飞片速度等冲击波物理参数的精密测量要求 ,开发了一种快响应光纤探针技术。该光纤探针由一根一端镀膜的梯度石英光纤和一根金属套管构成。在测量爆轰波、飞片和冲击波到达时间的实验中 ,可达到纳秒甚至亚纳秒的时间响应。实验证明该技术是一种可靠的、高时间分辨率的测试手段。     

A new method for measuring impulsive force at contact parts

A simple method has been devised for measuring the impulsive force generated at a contact part. Special sensing plates are used to produce an effect equivalent to the embedment of small strain gages in a solid. This method is effective for measuring the impulsive force directly and sensitively, it is almost entirely free from the disturbance caused by interference with reflected waves. It is even effective for the case in which an elastic-plastic deformation may occur at the contact part and the contact area may vary with time.     

Convective heat transfer and pressure loss in rectangular ducts with drop-shaped pin fins

It has been experimentally researched that convective heat transfer and pressure loss characteristics in rectangular channels with staggered arrays of drop-shaped pin fins in crossflow of air. The effects of arrangements of pin fins on heat transfer and resistance are discussed and the row-by-row variations of the mean Nusselt numbers are presented. By means of the heat/mass transfer analogy and the naphthalene sublimation technique, the heat transfer coefficients on pin fins and on endwall (base plate) of the channel have been achieved respectively. The total mean heat transfer coefficients of pin fin channels are calculated and the resistance coefficients are also investigated. The experimental results show that heat transfer of a channel with drop-shaped pin fins is higher than that with circular pin fins while the resistance of the former is much lower than that of the latter in the Reynolds number range from 900 to 9000. Received on 20 January 1997     

Photoelastic studies on progress of separation in interference fits

Interference fits are used extensively in aircraft structural joints because of their improved fatigue performance. Recent advances in analysis of these joints have increased understanding of the nonlinear load-contact and load-interfacial slip variations in these joints. Experimental work in these problems is lacking due to difficulties in determining partial contact and partial slip along the pin-hole interface. In this paper, an experimental procedure is enumerated for determining load-contact relations in interference/clearance fits, using photoelastic models and applying a technique for detecting progress of separation/contact up to predetermined locations. The study incorporates a detailed procedure for model making, controlling interference, locating break of contact up to known locations around the interface, estimating optically the degree of interference, determining interfacial friction and evaluating stresses in the sheet. Experiments, simulating joints in large sheets, were carried out under both pin and plate loads. The present studies provide load-separation behavior in interference joint with finite interfacial friction.     

有限尺寸多钉连接件钉传载荷计算的解析方法

提供一种确定多钉连接件中钉传载荷的解析方法，这个方法将被连接件看作弹性体，以经典结构力学以及弹性理论平面问题复变函数解法为基础，建立了求解钉传载荷的线性代数方程组并给出了若干算例。这个方法不仅具有合理的力学模型，而且具有计算的简捷性与适用的广泛性。     

Whole-field strain measurement in a pin-loaded plate by electronic speckle pattern interferometry and the finite element method

The strain field in an epoxy plate loaded in tension through a steel pin is determined using electronic speckle pattern interferometry (ESPI) and the finite element method (FEM). In a dual-beam illumination speckle interferometer, the in-plane component of the displacement at the plate's surface is accurately measured using a four-step phase-shifting algorithm. Digital image processing algorithms have been developed for noise reduction and strain calculation directly in the computer from the phase map with a strain gage length of about 0.4 mm. A whole-field strain map is obtained, as well as distributions of strain concentration factor, in critical regions near the hole of the plate. FEM is used to perform a nonlinear contact analysis accounting for friction effects at the pin/hole interface. The agreement between experimental results and numerical predictions is good. In terms of speed, accuracy and ease of use, dual-beam ESPI appears to be a superior method of whole-field strain analysis.     

有限尺寸多钉连接件钉传载荷计算的解析方法

提供一种确定多钉连接件中钉传载荷的解析方法，这个方法将被连接件看作弹性体，以经典结构力学以及弹性理论平面问题复变函数解法为基础，建立了求解钉传载荷的线性代数方程组并给出了若干算例。这个方法不仅具有合理的力学模型，而且具有计算的简捷性与适用的广泛性。     

Effect of friction in a contact problem for a plate with a pin

A solution is obtained for a contact problem concerning the tension of a rectangular elastic plate with a circular hole into which a rigid stationary pin has been inserted. There is a small gap between the hole and the pin, which is of circular cross section. Friction acts in the contact region in accordance with the Coulomb law. The finite-element method and the Boussinesq principle are used to determine the load that realizes a specified contact region. Two variants of boundary conditions on the contour of the hole are examined. Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 4, pp. 184–192, July–August, 1998.     

一种通过改进Canny算子提取光弹条纹骨架线的方法

光弹性法是确定应力集中系数的有效手段，在实际工程中应力参数都是通过分析光弹干涉条纹图获得的，由于光弹干涉条纹图的复杂性，且影响成像质量的因素较多，因此如何从光弹干涉条纹图中撇开其复杂性，较高精度的提取骨架线，是一项较困难的工作，本文提出一种由改进的Canny算子对条纹方位图进行直接运算提取光弹条纹骨架线的算法，实验表明此方法对光弹条纹图很有效。     

正交各向异性板孔销接触问题的复变函数解法

本文提出一个计及轴销变形与接触区摩擦效应的弹性轴销模型,并采用弹性理论的复变函数解法,研究了正交各向异性无限大板的孔销接触问题.分析表明,板件的孔边应力分布与板件、轴销的材料性能密切相关,而且,摩擦系数的大小对应力分布也存在明显影响.     

基于Bayes方法的多元正态应力强度可靠度分析

实际工程中,应力和强度是多维相关的,且相关信息很难获得,使用传统的单维应力-强度干涉模型很难进行可靠度分析,需要研究多元应力-强度干涉模型的可靠度计算问题。描述了两种多元应力-强度干涉模型,针对应力、强度服从正态分布的情形,使用Bayes方法,充分利用验前信息,由多元应力-强度干涉模型获得分布参数验后分布,并基于多元统计学知识,采用仿真抽样方法,进行可靠度验后预报。巡航弹可用过载的仿真算例验证Bayes方法在应力、强度试验信息较少的情况下,可高精度地预测可靠度的验后分布。     

Experimental investigation on circumferential and axial temperature gradient over fuel channel under LOCA

In a nuclear reactor temperature rises drastically in fuel channels under loss of coolant accident due to failure of primary heat transportation system. Present investigation has been carried out to capture circumferential and axial temperature gradients during fully and partially voiding conditions in a fuel channel using 19 pin fuel element simulator. A series of experiments were carried out by supplying power to outer, middle and center rods of 19 pin fuel simulator in ratio of 1.4:1.1:1. The temperature at upper periphery of pressure tube (PT) was slightly higher than at bottom due to increase in local equivalent thermal conductivity from top to bottom of PT. To simulate fully voided conditions PT was pressurized at 2.0 MPa pressure with 17.5 kW power injection. Ballooning initiated from center and then propagates towards the ends and hence axial temperature difference has been observed along the length of PT. For asymmetric heating, upper eight rods of fuel simulator were activated and temperature difference up-to 250 °C has been observed from top to bottom periphery of PT. Such situation creates steep circumferential temperature gradient over PT and could lead to breaching of PT under high pressure.     

Forced convective heat transfer enhancement with perforated pin fins

Increasing miniaturization of high speed multi-functional electronics demands ever more stringent thermal management. The present work investigates experimentally and numerically the use of staggered perforated pin fins to enhance the rate of heat transfer in these devices. In particular, the effects of the number of perforations and the diameter of perforation on each pin are studied. The results show that the Nusselt number for the perforated pins is 45 % higher than that for the conventional solid pins and it increases with the number of perforation. Pressure drop with perforated pins is also reduced by 18 % when compared with that for solid pins. Perforations produce recirculations in the x–y as well as the x–z planes downstream of the pins which effectively increase convective heat transfer. However, thermal dissipation decreases significantly when the ratio of pin diameter to perforation diameter exceeds 0.375. This is due to both a reduction in the number of perforation per pin and the decrease in the axial heat conduction along the pin.     

深孔台阶爆破近区振动信号趋势项去除方法

基于深孔台阶爆破近区大量实测振动信号,总结了趋势项产生的原因主要为大振幅脉冲输入下的非线性失真及低频干扰叠加,在此基础上以测试仪器有效监测范围作为识别趋势项组成部分的判别准则。利用集合经验模态分解（ensemble empirical mode decomposition,EEMD）、小波分解等信号分析手段,提出了以固有模态函数（intrinsic mode function,IMF）的频带分布为指标、人工判别的趋势项去除方法,以及基于自相关分析识别噪声特征的小波阈值去噪方法。实例证明该方法切实有效,可实现爆破信号的批量化预处理。     

Investigation of the pin joints in composites by the moiré method

A method combining moiré-fringe patterns with strain-gage measurements is applied to the analysis of strain distribution in a double-lap joint specimen under pin load. The specimens are crossplied and woven-fabric graphite/epoxy composites. Fiber orientations for both of the composites are 0 deg/90 deg, and ±45 deg to the load direction. The results indicate that the strain distributions in the specimen are greatly influenced by the fiber orientation. In this experiment, these specimens were collapsed at the pin-hole edge by the pin load. However, the failure load is not always dependent on the fiber orientation.     

Behaviors of a single crack in multiple bolted joints

This paper examines the pin load ratios and the stress intensity factors (SIFs) of a single crack in the multiple bolted joints by using finite element analyses. Cubic-spline contact elements and rigid links were used to model the contact surface between the bolt and the rigid pin. The least-squares method was used to determine the SIFs. The finite element results indicate that the cracked hole can still sustain the major part of the original loading at the uncracked condition. The first hole sustains the largest pin load and mode-I SIF, which are reduced little for crack propagation. This critical condition cannot be reduced by the arrangement of more pins in the plate. In this paper, two simple formulae were also investigated to fit the load ratios and SIFs of the multiple bolted-joints problems.     

直流磁场下销盘摩擦接触区的电磁感应现象

为了研究直流磁场对45钢销盘摩擦副的摩擦磨损特性的影响,根据磁场销盘摩擦试验机的结构和销盘摩擦副在摩擦过程中的实际接触情况,建立了二维微凸峰接触静态磁场和瞬态磁场有限元模型,分析了销盘摩擦接触区的电磁感应现象,得出以下结论:磁感应强度B在摩擦接触区分布不均,在微凸峰接触点区域的磁感应强度B值较大;摩擦试验中,在销盘磨痕和磨屑的微凸峰接触区将产生较高频率的动态磁化,同时在微凸峰上产生较大的感应电流,这些现象促进了销盘磨痕表面和磨屑的氧化.     

An optical dilatometer

Summary An instrument is described which enables displacements of 2 × 10⁻⁶ cm to be determined by means of interference phenomena of monochromatic light. The measuring pin is pushed against the specimen with a force of 4000 dynes. The instrument setting remains stable for a period of several hours.