船体梁振动的反共振频率配置设计

基于船舶主机等主要激励,计算得到了船体梁的反共振频率,并提出了一种基于反共振频率配置的船体振动设计方法。该方法可将激励频率设置为反共振频率,通过对结构刚度修改或质量修改,使得船体的上层建筑或桅杆等重要部位在该反共振频率下振动响应为零,并可明显减小该频率下船体的振动响应。数值算例验证了所提出的反共振频率配置设计方法的有效性。     

计及二阶效应的梁杆系统动力响应分析方法研究

基于动力刚度法和有限元理论提出了一种考虑二阶效应计算梁杆动力响应的新方法。通过求解轴向力作用下Bernoulli-Euler 梁横向和轴向挠度自由振动微分方程,利用位移边界条件反解出待定系数,得到了动态精确形函数;使用经典有限元方法推导了考虑截面自身旋转惯量的质量阵和考虑二阶效应的刚度阵,该质量阵和刚度阵各元素均为轴力和圆频率的超越函数;建立了杆系结构瞬态动力学分析的动力平衡方程,给出了稳定和高效的求解方案。对几个典型的算例进行了计算分析,并与通用软件ANSYS 的计算结果进行了比较。计算结果表明:该分析梁杆系统动力响应的新方法具有较高的计算精度和效率,特别是能够准确地计入轴力对于梁杆动力响应的影响。     

考虑应变依赖性的硬涂层圆柱壳振动特性有限元分析

硬涂层材料的应变依赖性使分析硬涂层圆柱壳的振动特性成为一项具有挑战性的研究任务。通过自编有限元程序来解决考虑应变依赖性的硬涂层圆柱壳振动特性计算问题;在用多项式表征硬涂层材料应变依赖性的前提下,研发出一种4节点36自由度的复合单元来描述硬涂层圆柱壳结构,并确定了该单元的质量、刚度矩阵以及基础激励作用下的单元所受的载荷向量;在确定等效应变的基础上,提出了利用Newton-Raphson法求解硬涂层圆柱壳非线性振动响应及共振频率的计算流程;以Ni Co Cr Al Y+YSZ硬涂层圆柱壳为对象进行了实例研究,对其线性和非线性振动特性进行求解,其中将线性计算结果与ANSYS求解结果进行了比对以初步说明研发程序的合理性。硬涂层圆柱壳的非线性计算结果显示:随着激励幅度的增加,硬涂层圆柱壳显示软式非线性特点。     

Miura折叠超材料在简谐激励下的振动响应

折叠超材料基于折叠结构发展而来，具有超常的物理性能。应用ADAMS分析典型的三种结构模型，在力和位移两种简谐激励下，不同折痕刚度对Miura折叠超材料振动响应的影响。结果表明，单自由度结构的Miura模型在两种激励下频率响应类似，通过改变折痕刚度可以改变其共振频率，达到很好的低频隔振效果。多自由度模型可以通过增加堆叠数量降低共振频率。为Miura折叠结构的隔振设计提供一定理论参考。     

可调频液压式动力反共振隔振器动力学分析及优化设计

对直升机主减安装结构进行隔振设计的目的在于阻断叶率旋翼桨毂力向机体传递,从而降低机体振动水平。针对上述主减隔振问题,提出了一种反共振频率可调的液压式动力反共振隔振器,基于拉格朗日方程建立其动力学模型。动力学分析表明:通过调节空气弹簧的刚度可调节反共振频率。进一步保持反共振频率不变,采用遗传算法优化设计隔振器的结构参数,可得到更宽的隔振频带,且隔振器质量更轻。     

设备对船体结构的激励力及其应用研究

针对以不平衡力为主的设备台架试验激励力向实船的转换方法进行研究,推导给出了设备对船体结构的激励力公式,并提出了设备与船体耦合振动分析的简化方法。将设备-隔振器-安装基础视为多自由度振动系统,基于振动理论,建立了设备与安装基础耦合振动的分析模型,得到了设备向安装基础传递的激励力计算公式;在此基础上,给出了设备向船体结构传递激励力的计算公式,提出了设备与船体结构耦合振动分析的简化方法,并验证了方法的正确性。研究表明:设备对船体结构的激励力不仅与设备激励力密切相关,还与设备质量、隔振器刚度及阻尼、船体结构刚度等密切相关;所提的设备与船体结构耦合振动简化方法具有较高精度,可满足工程要求。     

Miura折叠超材料在简谐激励下的振动响应

折叠超材料基于折叠结构发展而来,具有超常的物理性能。应用ADAMS分析典型的三种结构模型,在力和位移两种简谐激励下,不同折痕刚度对Miura折叠超材料振动响应的影响。结果表明,单自由度结构的Miura模型在两种激励下频率响应类似,通过改变折痕刚度可以改变其共振频率,达到很好的低频隔振效果。多自由度模型可以通过增加堆叠数量降低共振频率。为Miura折叠结构的隔振设计提供一定理论参考。     

基于时域残余力向量特征分解的结构损伤识别方法研究

提出基于时域残余力向量的结构损伤识别方法。从结构振动方程出发,推导强迫振动条件下由结构动力响应求解时域残余力向量的表达式。时域残余力向量包含与损伤过程相关的时间信息,可以用来识别损伤发生的时刻。通过结点时域残余力向量值的变异系数建立损伤位置指标,识别损伤位置。建立结构残余力矩阵特征分解方法,特征分解获得的特征向量在损伤前后不发生改变,而特征值与单元刚度相关。因此,可以从特征值中提取单元刚度参数构建损伤程度参数,直接识别损伤程度。将时域残余力向量方法应用于武汉军山大桥模型的损伤识别,结果表明：提出的方法在单点激励和多点激励下均可高精度地识别出损伤发生的时刻、位置和程度。提出的方法通过对时域残余力向量特征分解提取损伤时刻、位置和程度指标,计算过程直观且精度高,避免了繁琐的时频变换、优化迭代等计算过程。     

城市轨道交通地下线振动源机理和频率特性EI北大核心CSCD

基于我国24个城市轨道交通地下线35个断面振动源的实测数据,分析了城市轨道交通地下线的振动源机理和时频特性,并利用钢轨、道床、隧道壁的实测振动数据识别车辆簧下质量和轨道耦合系统P2共振频率,导出扣件刚度;通过力锤敲击试验识别了轨道第1阶自振频率,导出扣件刚度。提出了P2共振和车轮磨耗激励频率是城市轨道交通环境振动和室内二次结构噪声的主要激励源之一,扣件垫板老化后刚度增大使P2共振频率提高,对二次结构噪声的贡献比对环境振动的贡献更为显著。Pined-Pined共振、轮轨粗糙度是城市轨道交通环境噪声和车内噪声的主要激励源。     

结构动力的反分析方法研究

本文以线性多自由度体系在随机荷载作用下振动响应的正分析为基础，建立了结构振动荷载谱的反分析方程，采用线性方程组最小二乘解法对诱发结构振动的激振力进行了求解，并求出相应的动荷载时间历程，从而是结合分析可地动力响应分布进行计算，籍高拱坝泄洪振动水弹性模型实验研究。对此反分析方法给予验证，计算结果与实验测试成果的合，事实说明，动力反分析地复杂结构体系在多振源或不确定动荷载作用下的动态特征研究有重要意义。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。