红外热成像技术在电连接器插拔磨损检测中的应用研究

接触件是电连接器的核心元件,因插拔产生的磨损会导致其电接触性能退化甚至失效。针对上述问题,提出了一种电连接器插拔磨损检测方法。基于设计的检测装置开展电连接器插拔试验,并在试验过程中对电连接器接触件进行定时红外热成像检测;同时,分析插拔过程中电连接器接触件间磨屑的分布特征及变化规律,并通过表面形貌分析和能谱分析来验证红外热成像分析结果。研究发现,电连接器插孔簧片的主要磨损区域为端部,其根部有少量磨屑且聚集区域相对分散;随着插拔次数的增加,电连接器接触件间的磨屑逐渐增多,磨损区域面积逐渐增大,且磨屑聚集的位置也随着插拔运动发生变化,随机地分布在接触件间;因存在加工误差,电连接器的插孔簧片非对称分布,使得不同插孔簧片的磨损程度存在差异。结果表明,所提出的检测方法可有效观察电连接器接触件插拔磨损的变化过程,可作为电连接器磨损程度在线监测及剩余寿命预测的有效手段。研究结果可为电连接器性能退化机理和失效分析提供依据。     

边坡坡度对路堤风吹雪影响研究

路堤边坡坡度是影响风吹雪区域路堤积雪的重要因素,利用现场模型试验以及流场数值模拟的方法,研究边坡坡度对路堤积雪影响规律,分析积雪形成机理。结果表明:路堤周围积雪范围与流场风速减弱区域存在较好的对应关系,但并非定量对应,用流场中风速减弱区域简单地定量判断积雪范围的方法误差较大;迎风边坡坡度的改变对路堤周围积雪分布影响较大,较缓的迎风边坡坡度将有效地减小路堤周围积雪量和积雪范围,路面更不易形成积雪,可以减小风雪流对路堤工程的危害;背风边坡坡度的改变对路堤周围积雪影响较小,路堤设计时可作为次要因素考虑;根据试验和模拟结果得出路面不易积雪的临界边坡坡度在40°和45°之间,保守起见,建议工程应用中取40°为路面不易积雪的临界边坡坡度。     

The dynamic indentation of an elastic-viscoplastic work-hardening slab by a rigid punch

A unified theory for elastic-viscoplastic work-hardening materials, which requires neither a yield criterion nor loading or unloading conditions, is implemented to solve two-dimensional dynamic problems. Specifically, the theory is applied to the dynamic indentation by a rigid indenter of a slab made of an elastic-viscoplastic material. The contact area between the indenter and the slab at any time is not known in advance but should be determined from the process of the solution. An iterative numerical procedure is proposed by which the complete solution is determined from the dynamic elastic-viscoplastic equations, the moving mixed boundary conditions, the requirement that the contact normal stresses are compressive and that no interpenetration occurs outside the contact area. The method is applied to the indentation problem of a viscoplastic slab by a long rigid circular cylinder, and by a wedge-shaped die. Comparisons with the corresponding perfectly elastic problems are given.     

正棱台缓冲垫结构参数对静态缓冲性能的影响

目的研究不同结构参数的正棱台缓冲垫(EPS)在接触面积相同且体积相同时静态缓冲性能的差异。方法以发泡聚苯乙烯(EPS)为试验材料,设立10组接触面积相同,体积相同,厚度及斜面倾角不同的正棱台结构样本,利用万能材料试验机对10组样本进行静态压缩试验,得到10组不同结构参数的应力-应变曲线、应变能-应变曲线、应变能-应力曲线及缓冲系数-静应力曲线。结果随着斜面倾角的增大,缓冲垫的刚度逐渐增大,能量吸收增大,当斜面倾角大于等于70°后,缓冲性能基本相同;在缓冲垫受到同等冲击强度条件下,斜面倾角为80°时正棱台缓冲垫的缓冲性能最好,应变能最大,且其产生的变形量及应力均小于普通六面体缓冲垫。结论在包装设计过程中,可将接触面的侧面设置为80°倾角,按照此结构设计包装,产品更安全,接触部位厚度可降低25.12%,真正实现了降本增效。     

High-precision measurement of a fiber connector end face by use of a Mirau interferometer

What we believe to be a new instrument for measuring the end-face geometrical parameters of fiber connectors is described. In this apparatus, a Mirau-type interferometric objective is employed to measure a small area of the connector end face and generate an interferogram corresponding to the surface profile. Various new technologies are used to ensure excellent performance and high measurement repeatability. A multipoint method is proposed to adjust the inclination of the physical contact sample stage. The physical contact angle of the sample stage is adjusted directly on the instrument by use of a special tool whose angle is calibrated with the reversal method. Measurement results of important parameters of the fiber connector end face are compared with those inspected by a commercial profiler or with a standard sample. Optical insertion losses of connectors inspected by the developed system are also evaluated.     

复杂曲面五轴加工局部干涉处理技术研究

针对复杂曲面环形刀五轴数控加工中的局部干涉问题,提出了一种基于曲率匹配及网格点的干涉处理技术。首先,利用曲率匹配原则选出合理的刀具半径,以保证在切触点处沿任何方向上刀具与被加工曲面之间不会发生干涉,然后在各个切触点处通过比较刀具曲面最小主曲率与加工曲面最大主曲率确定出刀具的初始倾角。为了判断切触点邻近区域是否存在干涉问题,采用了网格点来快速自动生成检测区域及初始检测点。文中对有效检测点的筛选以及干涉的判断和处理技术分别进行了详细论述。最后,以非均匀有理B样条曲面为加工实例,对上述算法进行了测试和验证。     

基于线性回归的单柱塞泵单向阀参数优化

针对单柱塞泵系统中配流单向阀参数不合理所导致的吸油不充分、系统响应慢等问题,提出了一种基于线性回归的多参数优化方法。首先,通过AMESim软件进行单柱塞泵系统仿真分析,并利用MATLAB拟合工具箱分别探讨了不同单向阀参数（弹簧预紧力、弹簧刚度和阀芯质量）与进油口流量的关系。然后,在利用主成分分析法消除各参数之间相关性的基础上,以进油口流量为因变量,弹簧预紧力、弹簧刚度和阀芯质量为自变量,各参数的取值范围为约束条件,建立了基于线性回归的单向阀参数优化模型,并采用遗传算法进行优化求解。最后,根据优化前后的单向阀参数,对单柱塞泵系统进行仿真分析和实验验证。仿真结果表明,优化后进油口流量提高了21.3%;实验结果表明,优化后进油口的实际流量提高了16.8%。研究表明,所提出的多参数优化方法是一种有效的方法,可为单柱塞泵系统中配流单向阀的参数优化提供参考。     

Inclined toroidal surface that fits an off-axis conic section

We developed a formulation using the continuous least-squares method to determine the inclined toroidal surface that best fits a given off-axis conic section. A toroid with a known curvature is used to obtain an analytic equation for the angle of inclination of the axis with respect to the normal to the center of the off-axis section.     

电流密度对CNTs-Ag-MoS2-G复合材料滑动电摩擦磨损性能的影响

滑动电接触材料应具有良好的耐磨性能以及出色的导电性能,在航空航天领域中,制造先进的电接触材料尤为重要.实验中采用粉末冶金法制备CNTs-Ag-MoS2-G复合材料,研究了复合材料电摩擦磨损过程中的接触电阻及磨损率的变化,并通过扫描电子显微镜观察材料磨损后表面形貌.实验结果表明:在电流密度从5A/cm2增加到15A/cm2的过程中,复合材料接触电阻下降,体积磨损量增加,并且由于电弧侵蚀作用的影响,正刷的磨损量大于负刷,碳纳米管的特殊的基体增强作用及一定的导电导热能力使得CNTs-Ag-MoS2-G复合材料磨损量小于Ag-MoS2-G复合材料磨损量.     

Analytical approximations to the viscous glass-flow problem in the mould-plunger pressing process, including an investigation of boundary conditions

Industrial glass is produced at temperatures above 600°C, where glass becomes a highly viscous incompressible fluid, usually considered as Newtonian. In the production two phases may be distinguished, namely the pressing phase and the blowing phase. This study will be concerned with glass flow in the pressing phase, which is called thus because a blob of fluid glass (called a gob) is pressed in a mould by a plunger, such that the glass flows between mould and plunger, in order to obtain the preform of a bottle or jar, called a parison. In the blowing phase (not considered here) the parison is subsequently blown into the final shape of the product. By application of the slender geometry of mould and plunger and a cylindrical symmetry, a form of Reynolds's lubrication flow equations is obtained. These equations are solved by utilizing the incompressibility of the glass, by which the flux at any axial cross section is determined for prescribed plunger velocity, leading to analytical results in closed form for velocity field and pressure gradient. The glass level is implicitly defined by the integral over the varying volume which is to remain constant. The pressure may then be determined by integration. Special attention is given to the required boundary conditions. It is known that, depending on several problem parameters like temperature, pressure, and smoothness of the wall, the glass flow slips, to some extent, along the wall. Therefore, this study includes a general formulation of the boundary condition of partial slip in the form of a linear relation between shear stress and slip velocity, also known as Navier's slip condition. The coefficient of this relation, a positive number, may vary in our solution with axial position, but depends on the problem and is to be obtained from (for example) experiment. Two special cases, which seem to be relevant in practice, are considered as examples: (i) no slip on both plunger and mould; (ii) no slip on the mould and full slip (zero friction) on the plunger. The results are compared with fully numerical (FEM) solutions of a Stokes-flow model, and the agreement is good or excellent. Since in any practical situation it is not the plunger velocity which is prescribed, but (within practical limits) the force applied by the plunger, the problem of a prescribed plunger force has also been investigated.     

Process-dependent Thermal-Mechanical Behaviors of an Advanced Thin-Flip-Chip-on-Flex Interconnect Technology with Anisotropic Conductive Film Joints

User experiences for electronic devices with high portability and flexibility, good intuitive human interfaces and low cost have driven the development of semiconductor technology toward flexible electronics and display. In this study proposes, an advanced flexible interconnect technology is proposed for flexible electronics, in which an ultra-thin IC chip having a great number of micro-bumps is bonded onto a very thin flex substrate using an epoxy-based anisotropic conductive film (ACF) to form fine-pitch and reliable interconnects or joints (herein termed ACF-typed thin-flip-chip-on-flex (TFCOF) technology). The electrical and thermal -mechanical performances of the micro-joints are the key to the feasibility and effectiveness of the technology. Thus, the main goal of the study is to assess the process-induced thermal-mechanical behaviors of the interconnect technology during the bonding process. To undertake the process modeling, a process-dependent simulation methodology that integrates both thermal and nonlinear thermal-mechanical finite element (FE) analyses together with ANSYS^® birth-death modeling technique is proposed. The validity of the process modeling is confirmed through various temperature and warpage measurements. Subsequently, the contact behaviors of the ACF joints under four-point bending and static bending tests are characterized through FE modeling. The simulated contact stresses are further correlated with the measured electrical resistance data using four-point probe method, by which the minimum threshold contact stress for achieving a reliable contact electrical performance is determined.     

Shape design sensitivity analysis and optimization of two-dimensional periodic thermal problems using BEM

 A general procedure to perform shape design sensitivity analysis for two-dimensional periodic thermal diffusion problems is developed using boundary integral equation formulation. The material derivative concept to describe shape variation is used. The temperature is decomposed into a steady state component and a perturbation component. The adjoint variable method is used by utilizing integral identities for each component. The primal and adjoint systems are solved by boundary element method. The sensitivity results compared with those by finite difference show good accuracy. The shape optimal design problem of a plunger model for the panel of a television bulb, which operates periodically, is solved as an example. Different objectives and amounts of heat flux allowed are studied. Corresponding optimum shapes of the cooling boundary of the plunger are obtained and discussed. Received 15 August 2001 / Accepted 28 February 2002     

Microscale modeling of effective mechanical and electrical properties of textiles

A computational framework for assisting in the development of novel textiles is presented. Electronic textiles are key in the rapidly growing field of wearable electronics for both consumer and military uses. There are two main challenges to the modeling of electronic textiles: the discretization of the textile microstructure and the interaction between electromagnetic and mechanical fields. A director‐based beam formulation with an assumed electrical current is used to discretize the fabric at the level of individual fibrils. The open‐source package FEniCS was used to implement the finite element model. Contact integrals were added into the FEniCS framework so that multiphysics contact laws can be incorporated in the same framework, leveraging the code generation and automated differentiation capabilities of FEniCS to produce the tangents needed by the implicit solution method. The computational model is used to construct and determine the mechanical, thermal, and electrical properties of a representative volume elements of a plain woven textile. Dynamic relaxation to solve the mechanical fields and the electrical and thermal fields is solved statically for a given mechanical state. The simulated electrical responses are fit to a simplified Kirchhoff network model to determine effective resistances of the textile. Copyright © 2016 John Wiley & Sons, Ltd.     

Variation of mixed modes stress intensity factors of an inclined semi-elliptical surface crack

In this paper, a singular integral equation method is applied to calculate the stress intensity factor along crack front of a 3D inclined semi-elliptical surface crack in a semi-infinite body under tension. The stress field induced by displacement discontinuities in a semi-infinite body is used as the fundamental solution. Then, the problem is formulated as a system of integral equations with singularities of the form r ^–3. In the numerical calculation, the unknown body force doublets are approximated by the product of fundamental density functions and polynomials. The results show that the present method yields smooth variations of mixed modes stress intensity factors along the crack front accurately for various geometrical conditions. The effects of inclination angle, elliptical shape, and Poisson's ratio are considered in the analysis. Crack mouth opening displacements are shown in figures to predict the crack depth and inclination angle. When the inclination angle is 60 degree, the mode I stress intensity factor F _I has negative value in the limited region near free surface. Therefore, the actual crack surface seems to contact each other near the surface.     

Solution of an elastoplastic contact problem on the dynamic penetration of a conical indenter with an arbitrary angle at the tip

An analytical study is made of the physicomechanical nature of the dynamic hardness coefficient for a cone with an arbitrary angle at the tip, this coefficient being the main criterion for substantiation of the method of double dynamic indentation. A relationship is established between the criterion and strength, as well as the elastoplastic strain properties of metals. A study was made of the laws governing the distribution of pressure and stress over the surface of elastoplastic contact of a conical indenter with a half-space, with allowance for strain-hardening. The study results were used to establish a theoretical foundation for developing a quick and highly accurate method of checking the hardness of metal products on the basis of parameters characterizing elastoplastic contact strain.Translated from Problemy Prochnosti, No. 5, pp. 44–52, May, 1992.     

Tangential-displacement effects in the wedge indentation of an elastic half-space – an integral-equation approach

The idea of considering tangential-displacement effects in a classical elastostatic contact problem is explored in this paper. The problem involves the static frictionless indentation of a linearly elastic half-plane by a rigid wedge, and its present formulation implies that the tangential surface displacements are not negligible and should thus be coupled with the normal surface displacements in imposing the contact zone boundary conditions. L.M. Brock introduced this idea some years ago in treating self-similar elastodynamic contact problems, and his studies indicated that such a formulation strongly influences the contact-stress behavior at half-plane points making contact with geometrical discontinuities of the indentor. The present work again demonstrates, by studying an even more classical problem, that the aforementioned considerations eliminate contact-stress singularities and therefore yield a more natural solution behavior. In particular, the familiar wedge-apex logarithmic stress-singularity encountered within the standard formulation of the problem (i.e. by avoiding the tangential displacement in the contact boundary condition) disappears within the proposed formulation. The contact stress beneath the wedge apex takes now a finite value depending on the wedge inclination angle and the material constants. By utilizing pertinent integral relations for the displacement/stress field in the half-plane, an unusual mixed boundary-value problem results whose solution is obtained through integral equations.     

Numerical solution for multiple crack problem in an infinite plate under compression

This paper investigates a numerical solution for multiple crack problem in an infinite plate under remote compression. The influence of friction is taken into account. In the first step of the solution, we make a full contact assumption on the crack faces. The full contact assumption means that one component of the dislocation distribution vanishes, and the first mode stress intensity factors (K ₁) at the crack tips become zero. On the above-mentioned assumption, the problem can be solved by using integral equation method, and the second mode stress intensity factors (K ₂) at the crack tips can be evaluated. Meantime, after solving the integral equation the normal contact stress on the crack faces can be evaluated. The next step is to examine the full contact assumption. If the contact stresses on the crack faces are definitely negative, the solution is true. Otherwise, the obtained solution is not true. It is found from present study that in most cases the full contact condition is satisfied, and only in a few cases the full contact condition is violated. Numerical examples are given. It is found that the friction can lower the stress intensity factors at crack tips in general.     

Cooling of a plane slab of an absorbing gray medium with simultaneous conduction and radiation heat transfer

A method for calculating transient heat transfer by radiation and conduction in a slab of a gray absorbing medium is discussed. The results are given from calculations of the cooling of a slab having a transparent upper boundary and a diffusely reflecting lower boundary in contact with an opaque material.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 5, pp. 874–879, November, 1981.