高架桥钢箱梁顶推施工研究

钢箱梁顶推施工技术在跨公路、铁路以及江河地段的高架桥施工中的应用优势显著。该文主要对高架桥钢箱梁顶推施工技术进行了研究,采用案例分析法,以某跨地铁高架桥工程施工为例,根据工程概况及高架桥钢箱梁结构设计,分析顶推施工技术方案及施工工艺。运用有限元进行顶推施工关键部位安全分析,结果表明顶推施工具有较高的安全性和稳定性;同时,通过对导梁、钢箱梁关键部位进行施工监测,结果表明导梁与钢箱梁最大应力值和最大应变均在允许范围内,满足施工安全要求。根据工程实际,证明高架桥刚强量顶推施工具有较高应用价值,值得借鉴。     

解析DF300型注水泵平衡系统失效原因

本文利用多级帛心式注水泵修理和使用中比较普遍的故障,运用修理和使用积累的经验,对故障现象具体的表现形式进行描述、分析的方法,对DF300型注水泵平衡系统失效的六种原凶,进行了具体分析,并提出了减缓平衡系统失效的具体建议。对轴阳力的产生、平衡系统的工作原理进行了描述。为提高修理人员修理技术、使用单位安全使用注水泵、提高运转泵效、将损失降到最低,提供了经验性的根据。     

浅谈钢箱梁顶推法的施工控制

本文总结了顶推施工方法的由来、发展、施工特点及其在钢箱梁斜拉桥中的应用情况以及存在问题。顶推施工不同于悬臂施工,其最大特点在于随着施工过程的进行,结构的坐标、边界支承条件以及相应的结构内力、变形等均在不断地发生变化。     

包装机中推料机构分析及优化

根据技术要求和基本技术参数,运用解析法对糖果包装机的推糖机构进行了结构分析,运用封闭矢量法对推糖机构中的曲柄摇杆进行运动学理论计算,利用Adams 软件进行建模与仿真分析。在分析基础上运用Ad-ams 进行优化,以压力角最小为目标函数,以曲柄摇杆的长度关系和摇杆转角24. 4°为约束条件,以曲柄长度、连杆长度、摇杆长度为设计变量,得到设计变量最优解。     

基于Triz的止推轴承创新设计

首先采用多屏幕法对止推轴承进行系统分析;其次针对设计止推轴承过程中存在的技术难题,运用矛盾矩阵表、创新发明原理等Triz工具指导设计止推轴承的创新方案,并选出最优创新方案;最后根据该优化方案设计出一种高承载力、高可靠性、易拆卸维修的止推轴承,成功应用于世界最大矿用潜水电泵(3200kW)的开发上。     

缅甸M区块上部复杂地层钻井技术研究

缅甸M区块属于推覆体构造,地层压力高,所钻地层主要是极易蠕变的软泥岩,在以前的钻井作业中事故频发。本文结合2009年在本区块成功完成的4口井的作业经验,从井身结构、钻头选型、钻头参数、钻井液和固井几个方面进行了研究,得出了应对该区块上部复杂地层的主要钻井措施和方案。实践证明,该套技术行之有效,对以后在类似地层钻井作业具有参考价值。     

采用主动式磁蓄冷器(AMR)的室温磁制冷机数值模拟

对采用主动式磁蓄冷器(AMR)的室温磁制冷机的工作进行了模拟计算,给出不同工作温区、不同磁场强度、不同换热流体时机器的制冷能力变化、COP及热力学完善度变化趋势的预测,并对在固定周期式和可变周期式下运行时的情况进行了对比,后者的制冷能力、COP及热力学完善度都优于前者.     

碰撞阻尼器系统的分岔、混沌与控制

对碰撞阻尼器振动系统推导了周期解存在的条件，并利用Poincare映射和数字仿真进行了分岔与混沌运动的研究。计算结果表明，这种非线性碰撞振动系统在特定的参数条件下，除了稳定的周期运动形态外，还会沿着倍周期分岔、HOPF分岔及拟周期环面破裂等分岔进入混沌运动。因此，为了有效地利用碰撞阻尼器特性控制振动，在设计和使用碰撞阻尼器时应考虑参数满足周期运动的条件，避免由于自身的非线性特性而产生的混沌运动。     

板坯连铸机推钢机垛板台液压系统改造

为适应生产要求,需要对3#板坯连铸机原有推钢机、垛板台进行移位,针对原设备存在的缺陷,在移位的同时,对液压系统进行改造,建立单独的液压站,缩短了液压管线。对改造后出现的问题,不断的进行优化、改进,通过加装蓄能器、管路固定等措施,使得系统运行稳定。减少了故障,延长了设备使用寿命。     

书本打包机推书机构结构动力学分析

针对图书物流中打包机的推书机构高速运动产生振动的问题,分析了推书机构的关键零部件,包括摆杆、动力轴和槽形凸轮。首先利用SolidWorks建立了推书机构的实体模型,然后分别导入ANSYS软件和ADAMS软件中进行有限元分析和动力学分析。结果表明,摆杆、动力轴和槽形凸轮的振动和运动特性满足工程实际应用要求,为推书机构的优化设计提供了必要依据。     

Automated Fast Initial Guess in Digital Image Correlation

A challenging task that has hampered the fully automatic processing of the digital image correlation (DIC) technique is the initial guess when large deformation and rotation are present. In this paper, a robust scheme combining the concepts of a scale‐invariant feature transform (SIFT) algorithm and an improved random sample consensus (iRANSAC) algorithm is employed to conduct an automated fast initial guess for the DIC technique. The scale‐invariant feature transform algorithm can detect a certain number of matching points from two images even though the corresponding deformation and rotation are large or the images have periodic and identical patterns. After removing the wrong matches with the improved random sample consensus algorithm, the three pairs of closest and non‐collinear matching points serve for the purpose of initial guess calculation. The validity of the technique is demonstrated by both computer simulation and real experiment.     

贝叶斯残余克里金插值方法的研究

简述了贝叶斯克里金插值法的基本原理，提出了实践中求取条件变异函数及软数据变异函数参数时存在的问题，针对这些问题在贝叶斯克里金原理的基础上推导出了贝叶斯残余克里金法，最后给出了应用实例及结论。     

Issues in convergence improvement for non-linear finite element programs

Systems of non-linear equations as they arise when analysing various physical phenomena and technological processes by the implicit Finite Element Method (FEM) are commonly solved by the Newton–Raphson method. The modelling of sheet metal forming processes is one example of highly non-linear problems where the iterative solution procedure can become very slow or diverge. This paper focuses on techniques to overcome these numerical difficulties. Several methods to generate initial guesses within the radius of convergence are proposed. Appropriate stopping criteria for the iterative procedure are discussed. A combination of various line search methods with the continuation method is proposed. The efficiency and robustness of these numerical procedures are compared based on a set of test examples. A particular form of line search was identified which allows the stable and efficient solution of highly non-linear sheet metal forming problems. Even though the present investigations were motivated by the application of the implicit FEM to the simulation of sheet metal forming processes, the findings are general enough to be applicable to a wide spectrum of non-linear FEM applications. © 1997 John Wiley & Sons, Ltd.     

The Global Nonlinear Galerkin Method for the Solution of von Karman Nonlinear Plate Equations: An Optimal & Faster Iterative Method for the Direct Solution of Nonlinear Algebraic Equations F(x) = 0, using x<sup style='margin-left:-6.5px'>·</sup> = λ[αF + (1 - α)B^TF]

The application of the Galerkin method, using global trial functions which satisfy the boundary conditions, to nonlinear partial differential equations such as those in the von Karman nonlinear plate theory, is well-known. Such an approach using trial function expansions involving multiple basis functions, leads to a highly coupled system of nonlinear algebraic equations (NAEs). The derivation of such a system of NAEs and their direct solutions have hitherto been considered to be formidable tasks. Thus, research in the last 40 years has been focused mainly on the use of local trial functions and the Galerkin method, applied to the piecewise linear system of partial differential equations in the updated or total Lagrangean reference frames. This leads to the so-called tangent-stiffness finite element method. The piecewise linear tangent-stiffness finite element equations are usually solved by an iterative Newton-Raphson method, which involves the inversion of the tangent-stiffness matrix during each iteration. However, the advent of symbolic computation has made it now much easier to directly derive the coupled system of NAEs using the global Galerkin method. Also, methods to directly solve the NAEs, without inverting the tangent-stiffness matrix during each iteration, and which are faster and better than the Newton method are slowly emerging. In a previous paper [Dai, Paik and Atluri (2011a)], we have presented an exponentially convergent scalar homotopy algorithm to directly solve a large set of NAEs arising out of the application of the global Galerkin method to von Karman plate equations. While the results were highly encouraging, the computation time increases with the increase in the number of NAEs-the number of coupled NAEs solved by Dai, Paik and Atluri (2011a) was of the order of 40. In this paper we present a much improved method of solving a larger system of NAEs, much faster. If F(x) = 0 [F_i(x_j) = 0] is the system of NAEs governing the modal amplitudes x_j [j = 1, 2...N], for large N, we recast the NAEs into a system of nonlinear ODEs: x^· = λ[αF + (1 - α)B^TF], where λ and α are scalars, and B_ij = ∂F_i / ∂x_j. We derive a purely iterative algorithm from this, with optimum value for λ and α being determined by keeping x on a newly defined invariant manifold [Liu and Atluri (2011b)]. Several numerical examples of nonlinear von Karman plates, including the post-buckling behavior of plates with initial imperfections are presented to show that the present algorithms for directly solving the NAEs are several orders of magnitude faster than those in Dai, Paik and Atluri (2011a). This makes the resurgence of simple global Galerkin methods, as alternatives to the finite element method, to directly solve nonlinear structural mechanics problems without piecewise linear formulations, entirely feasible.     

The Global Nonlinear Galerkin Method for the Analysis of Elastic Large Deflections of Plates under Combined Loads: A Scalar Homotopy Method for the Direct Solution of Nonlinear Algebraic Equations

In this paper, the global nonlinear Galerkin method is used to perform an accurate and efficient analysis of the large deflection behavior of a simply-supported rectangular plate under combined loads. Through applying the Galerkin method to the governing nonlinear partial differential equations (PDEs) of the plate, we derive a system of coupled third order nonlinear algebraic equations (NAEs). However, the resultant system of NAEs is thought to be hard to tackle because one has to find the one physical solution from among the possible multiple solutions. Therefore, a suitable initial guess is required to lead to the real solution for given load conditions. The feature of this paper is that we apply the global nonlinear Galerkin method to the governing PDEs and solve the resultant NAEs directly in each load step. To keep track of the physical solution, the initial guess for the current load step is provided by taking the solution of the NAEs for the last step as the initial guess. Besides, the size of the NAEs grows dramatically larger, with the increase of the number of terms of the trial functions, which will cost much more computational efforts. An exponentially convergent scalar homotopy algorithm (ECSHA) is introduced to solve the large set of NAEs. The approach in the present paper is more direct and simpler than either the incremental global Galerkin method, or the incremental local Galerkin method (finite element method) based on a symmetric incremental weak-form; both of which methods lead to the inversion of tangent stiffness matrices and Newton-Raphson iterations in each load step. The present method of exponentially convergent scalar homotopy of directly solving the NAEs is much better than the quadratically convergent Newton-Raphson method. Several numerical examples are provided to validate the feasibility and efficiency of the proposed scheme.     

鼓式制动器制动不稳定时变特性分析

由于工作环境复杂多变,制动器工作不稳定而导致振动和噪声,鼓式制动器制动时的温度变化对制动不稳定性影响较大,研究制动不稳定性影响因素及其制动不稳定时变特性具有实际工程意义。基于鼓式制动器四自由度接触模型,分别在Hypermesh和ABAQUS中建立鼓式制动器制动鼓和制动蹄总成模型与摩擦制动接触模型并进行试验验证;通过热机耦合动态分析,研究制动鼓温度对制动应力的影响;分析弹性模量和热膨胀系数对鼓式制动器制动不稳定时变特性的影响。分析表明：制动不稳定性是摩擦力耦合所致;制动过程中制动鼓温度与应力相互作用且均先快速上升后缓慢下降;鼓式制动器制动不稳定时变特性主要体现在不稳定模态个数及不稳定倾向系数（tendency of instability, TOI）值的变化,制动温度变化导致弹性模量变化,引起不稳定模态个数和TOI值略有变化,弹性模量对鼓式制动器制动不稳定时变特性影响较小;制动温度变化导致热膨胀系数变化,引起不稳定模态个数和TOI值先大幅降低后略有升高,热膨胀系数对鼓式制动器制动不稳定时变特性影响较大。研究结果对改善汽车制动声品质具有一定指导意义。     

基于贝叶斯-GO综合法的快递配送系统可靠性研究

提出用贝叶斯-GO综合方法分析快递配送系统可靠性。首先综合考虑配送系统对时间、品质、服务可靠性的要求,详细分析配送工作流程及其影响因素,建立GO图;然后根据映射规则转换为贝叶斯网络,最后通过案例分析,利用贝叶斯网络正反向推理和敏感度分析,得到系统的薄弱环节及其主要影响因素。研究结果表明：贝叶斯-GO综合法克服了单独使用GO法逻辑运算复杂繁琐的缺点,能够快速找到快递配送系统的薄弱环节及其主要影响因素,其中收件子系统故障率最高,快递员的配送不及时、寄件损坏、丢失是主要影响因素。     

Untersuchung von Schmelz‐ und Rekristallisationsprozessen sowie Riss‐, Oxid‐ und Porenbildung beim Schweißen

Investigation of melting and re‐crystallization processes and of crack, oxide and pore formation during welding In the paper some known investigation methods of the primary re‐crystallization and of the structure of the crystallization front are discussed. All these methods have disadvantages, in some cases they cause a limited validity or are expensive. The presented new method is based on the micrographic recording of the melting and solidifying metal surfaces. The method overcomes the above‐mentioned disadvantages. It is able to investigate in the welding seams not only the primary re‐crystallization processes but also the secondary ones including the formation of cracks and pores and the appearance of non‐metallic inclusions like oxides. The facilities of the method are demonstrated on some examples of use.     

Damage production, accumulation and materials performance in radiation environment

Collisions of energetic projectile particles with host atoms produce atomic displacements in the target materials. Subsequently, some of these displacements are transformed into lattice defects and survive in the form of single defects and defect clusters. Depending on the ambient temperature, these defects and their clusters diffuse, interact, annihilate, segregate and accumulate in various forms and are responsible for the evolution of the irradiation-induced microstructure. Naturally, both physical and mechanical properties and thereby the performance and lifetime of target materials are likely to be determined by the nature and the magnitude of the accumulated defects and their spatial dispositions. A multitude of processes covering a variety of temporal and spatial scales contribute to the evolution of the global microstructure. Results of computer simulations as well as theoretical modelling describing some of these processes will be reviewed and discussed. The framework within which the influence of irradiation on void swelling, radiation hardening and loss of ductility can be treated will be discussed. It will be emphasized that the nature of displacement damage production plays an important role in the evolution of the global microstructure. Finally, a brief summary of the current status in the fields of computer simulations and theoretical modelling is presented in the form of concluding remarks. This revised version was published online in July 2006 with corrections to the Cover Date.     

再论标准和标准化的基本概念

本文是作者再次对标准和标准化的概念进行讨论。首先讨论的是标准化的目的、主体和对象。作者认为标准化的目的是控制、有序化和统一化;标准化的主体是人/机构;标准化对象可以是具体的或抽象的事物,也可以是它们的组合;任何事物都可以抽象地表达为实体(entity)。第二,作者讨论了标准和标准化的本质以及它们的作用;认为从内容角度看,标准是匹配问题解决方案,也是为标准化对象规定需要满足的要求;从实施角度看,标准是规则;标准化则是制定、实施、传播标准的过程;标准的作用是能够创建并组织现实世界,并能够为相关方建立互相交流和共同理解的基础;标准化的作用是对创新方案进行选择和简化,阻止现实世界过度无序化发展,形成复杂化和简化之间的平衡。第三,作者讨论了标准的记录形式、自愿/强制属性和时空范围,认为标准的记录形式有文件、样品、图形符号、物理表达等多种形式;标准具有选择的自愿性和实施的强制性;标准在时空范围内是有限的。文章的结尾给出了理解标准化概念的框架。