粘弹性阻尼材料力学参数测试实验用双边附加自由结构阻尼试件设计方法研究

悬臂梁弯曲共振法测量粘弹性阻尼材料力学参数的实验中常以双边附加自由结构阻尼试件为实验对象。实验中试件设计的合理程度直接影响实验的测试精度。为了指导试件设计,通过灵敏度分析提出了影响系数的概念,并将其应用于分析试件的厚度比、共振频率比、密度比、损耗因子等参数的测量误差对粘弹性材料力学参数测试精度的影响中,进而对试件的设计提出一些有重要意义的技术规范。最后,基于悬臂梁弯曲共振法获取粘弹性材料力学参数的实验,分析了双边自由阻尼结构试件的适用范围。     

直接诺模图—描述粘弹性阻尼材料性能的新方法

将粘弹性阻尼材料涂刷、粘贴于薄板或壳体表面上组成复合阻尼结构,来增加机械结构的损耗因子.在设计粘弹性阻尼结构、预估其损耗因子时,材料的损耗因子和弹性模量是两个最主要参数。粘弹性材料是一种高分子材料,其应力、应变通常用复模量的关系来表示,即:     

海水介质对舰船粘弹性阻尼材料性能的影响研究

以典型的某牌号粘弹性阻尼材料为研究对象,分别在三亚试验站的全浸和仓储不同试验区带进行了长期自然海洋环境曝露试验,并对获得的老化周期为5年的试样进行了微观结构、力学、动态力学以及减振效果的测试和表征,并分析了海水介质对粘弹性阻尼材料老化性能影响的机制。      

考虑基底层阻尼的自由阻尼结构损耗因子修正公式

针对基底层阻尼不可忽略的自由阻尼结构,考虑基底层的拉伸变形,根据变形能理论和复刚度理论分别推导得到修正的损耗因子公式。而后利用ANSYS软件建立自由阻尼矩形板的实体模型并进行谐响应分析,分别通过变形能法和输入率法得到结构损耗因子的数值解。仿真对比表明,变形能法和复刚度法两种损耗因子修正公式的计算结果相吻合,结构损耗因子的两种有限元数值解均与修正公式的解析解相一致。研究表明,损耗因子修正公式是正确的,可用于一般基底层的自由阻尼类结构的损耗因子计算。     

阻尼材料对环肋柱壳稳态响应影响的分析

利用Ｆｌｕｇｇｅ壳体理论，讨论了敷设自由层粘弹性阻尼材料的环肋柱壳受周期性径向激励的稳态响应，用复模量形式计及基壳和粘弹性阻尼材料的损耗因子，并计入流固耦合作用，讨论了粘弹性阻尼材料的物理参数和厚度对其稳态响应的影响。     

船用压筋板的粘弹性阻尼处理

针对船用压筋板的局部阻尼处理和全部阻尼处理，本文考察了阻尼处理前后振动系统各特征值的变化，分析了阻尼处理对压筋板动态力学性能的影响，探讨了粘弹性阻尼材料抑制结构共振响应及宽频振动的有效性。     

夹芯复合材料结构阻尼特性研究

从粘弹性材料的本构关系出发,应用复特征值理论推导了夹芯复合材料结构阻尼的计算方法;同时基于能量损耗原理和阻尼的产生机理,研究了夹芯复合材料结构阻尼计算的模态应变能方法;提出了两种承载/减振夹芯复合材料结构模型,应用动态力学热分析方法测量了芯材的阻尼参数;应用两种阻尼计算理论和有限元数值分析相结合的方法研究了两种夹芯结构模型的损耗因子,并与试验结果进行了比较;分析了夹芯厚度对结构损耗因子的影响.     

材料阻尼模型综述

介绍了目前主要的几种材料阻尼模型,重点介绍了粘弹性材料阻尼模型.综述了各种模型的特点,适用范围.     

相位法测量仪的误差分析和实验研究

相位法以其测试精度高、测量频带宽的优点成为测量阻尼材料动态力学性能参数的一种重要方法。在对相位法测量原理研究的基础上,从理论上分析相位法测量仪中下夹持器质量的改变对测量阻尼材料杨氏模量结果的影响:在忽略下夹持器刚度和阻尼的影响时,下夹持器的质量越大,测量结果的误差也越大。最后,利用自行设计加工的测量装置进行实验研究,实验结果与理论分析基本一致。     

粘弹性高温阻尼材料研究进展

概述了粘弹性阻尼材料的阻尼机理,对粘弹性高温阻尼材料的研究现状及技术途径进行了分析讨论,并对其研究前景进行了展望。     

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.