受阻酚封端聚氨酯阻尼材料的结构与性能

分别设计合成了受阻酚AO-80和AO-2246封端聚氨酯预聚物,并经固化制得聚氨酯阻尼材料。采用傅里叶变换红外光谱、差示扫描热分析、扫描电镜表征了该材料的微观结构,并研究了受阻酚含量、受阻酚种类和聚醚相对分子质量对阻尼材料动态力学性能的影响。动态力学测试结果表明,所制得试样组分相容性较好,随着受阻酚用量的增加,最大阻尼因子增大,玻璃化温度升高,阻尼温域变宽;同质量比时,AO-2246封端所制得试样最大阻尼因子和损耗峰面积均高于AO-80体系;随着聚醚相对分子质量增加,试样的最大阻尼值增大,玻璃化温度降低,相容性变好。     

聚氨酯阻尼材料动态力学性能的研究

研究了聚氨酯阻尼材料的动态力学性能。实验结果表明,交联密度是影响聚氨酯阻尼材料损耗因子(tgδ)的重要因素,增加分子链中侧甲基(—CH_3)数目,有利于提高材料的损耗因子值,拓宽阻尼温域;加入片状填料可增大材料内部的剪切运动,使内耗值增大。     

高阻尼宽温域粘弹性硅橡胶复合材料的制备及性能研究

以硅橡胶和丁基橡胶为基体材料,成功制备出高阻尼宽温域粘弹性硅橡胶复合材料,最大损耗因子tanδmax>0.3≥0.7,损耗因子大于0.3的温度范围△Ttanδ≥100℃.同时研究了材料的力学性能、阻尼性能和相态结构.结果表明,在硅橡胶基质中,加入具有一定相容性的高阻尼丁基橡胶材料,可以显著提高体系的阻尼因子,拓宽有效阻尼温度范围.补强剂白炭黑的加入可以提高材料的机械力学性能,但对材料的阻尼性能产生一定的负面影响,通过加入一定量的硅烷偶联剂KH-845-5对白炭黑表面进行改性处理,可以部分有效解决这两种性能间的矛盾,达到高性能硅橡胶阻尼减振材料使用上的性能平衡.     

石墨烯/聚氨酯复合材料的制备及其力学性能分析

采用聚四氢呋喃作为软段,2,4-甲苯二异氰酸酯为硬段,MOCA为扩链剂,物理剥离的石墨烯(GNs)和硅烷偶联剂(APTES)改性的氧化石墨烯(GO)为填料合成了石墨烯/聚氨酯复合材料。通过溶胀平衡实验探究石墨烯与聚氨酯基体的相容性对力学性能的影响。结果表明,两种石墨烯的加入均能提高复合材料体系的交联密度。复合材料的拉伸强度均先增大后减小,损耗因子峰值增大。但改性GO能使阻尼温域拓宽,并且随着添加量的增加,改性GO组的体系交联密度、溶胀比、拉伸强度保持率等均优于GNs组。     

氢化羧基丁腈橡胶/AO-2246复合材料阻尼性能研究

以氢化羧基丁腈橡胶(HXNBR)为基体,加入极性有机小分子2,2'-亚甲基双-(4-甲基-6-叔丁基苯酚)(AO-2246)进行改性,制取了HXNBR/AO-2246复合材料,对其阻尼性能进行研究。结果表明,AO-2246质量分数在40%以内时,随其用量的增加HXNBR/AO-2246复合材料阻尼性能逐渐提高,在40%时状态最佳,此时损耗因子(tanδ)峰值为2.21,对应玻璃化转变温度(T_g)为24.9℃,tanδ>0.3的有效阻尼温域为32.6℃。HXNBR/AO-2246复合材料阻尼性能的提高是基于HXNBR中氰基(—CN)和羧基中的C=O与AO-2246中的羟基(—OH)形成了氢键网络作用,以及AO-2246较大侧基所带来的位阻效应。同时,随着AO-2246用量逐渐增加,小分子达到饱和并开始自聚结晶,材料出现两相结构,在AO-2246质量分数为50%时,过多的小分子使得材料阻尼性能下降,但对应Tg继续往高温方向移动。     

功能小分子对饱和橡胶/丙烯酸酯橡胶共混物阻尼性能的影响

研究了功能小分子对饱和橡胶/丙烯酸酯橡胶共混材料阻尼性能的影响,结果表明,受阻酚类功能小分子AO-80与1035FF并用可进一步提高饱和橡胶/丙烯酸酯橡胶共混材料的阻尼性能.功能小分子的损耗因子峰值温度对掺杂体系稳定性有重要影响,其峰值温度低于使用温度的掺杂体系具有稳定的阻尼性能.     

以石墨烯气凝胶为导电相的压电阻尼复合材料

阻尼材料在减振降噪领域有着极其重要的应用,而压电阻尼复合材料能够在普通阻尼材料摩擦损耗基础之上进一步引入力-电-热损耗,从而提高基体材料的阻尼性能,使其在主动和被动减震方面备受青睐。但是通常为了达到导电渗流阈值,需要添加大量的导电相。采用模板辅助氧化石墨烯自组装的方式制备了三维石墨烯气凝胶,以此作为导电相,以聚氨酯/聚甲基丙烯酸丁酯/聚甲基丙烯酸甲酯IPN共聚物作为基体,锆钛酸铅压电陶瓷作为压电相,制备了压电阻尼复合材料。三维石墨烯气凝胶的使用,由于其本身三维导电网络的存在,使得制备的压电阻尼复合材料可以在很低的导电相含量下达到导电渗流阈值,将压电陶瓷产生的电能转化为热能损耗掉,有效拓宽了基体材料的阻尼温域和提高了材料室温下的阻尼性能。     

AO-2246对聚氨酯阻尼及力学性能影响

聚氨酯(PU)中添加不同份数小分子AO-2246,研究了AO-2246对阻尼性能和力学性能的影响。结果表明,PU/AO-2246体系的损耗因子-温度(tanδ-T)曲线只有一个转变峰,是热力学相容体系,随着AO-2246添加份数的增多,聚氨酯的最大损耗因子tanδ_(max)及对应峰值温度均随之提高,tanδ最大可达到1.51。添加适量AO-2246会提高聚氨酯的拉断伸长率,但同时会降低其拉伸强度和硬度。     

工程用高性能溴化丁基/丁腈基阻尼材料的制备与性能

选择了溴化丁基橡胶(BIIR)与丁腈橡胶(NBR)共混改性来制备一种宏观均相、微观相分离的共混阻尼材料.制备出了在全部共混比范围内,力学性能均满足工程应用(拉伸强度≥12 M Pa,断裂伸长率≥500％)的橡胶阻尼材料,其中当BIIR/NBR共混比为80/20时,有效阻尼温域为-50到60℃.同时,在上述力学性能的约束下,研究了交联反应程度以及C5石油树脂的用量对阻尼因子的影响.随着硫磺用量从0.1份增加至3份,NBR富集相阻尼因子峰值对应的温度从10℃逐渐升高到60℃;在拉伸强度基本不变条件下,C5石油树脂能够拓宽有效阻尼(tanδ≥0.3)温域≥80℃.     

CIIR/AO-2246/PF复合材料的结构与阻尼性能研究

氯化丁基橡胶(CIIR)基体中添加了受阻酚AO-2246和酚醛树脂(PF),制备了CIIR/AO-2246/PF交联复合材料,并研究了其阻尼性能、力学性能和微观结构。结果表明:CIIR/AO-2246/PF交联复合材料的损耗因子-温度(tanδ-T)曲线只有一个单峰,是热力学相容体系,与纯的CIIR或CIIR/AO-2246交联体系橡胶相比,其tanδ峰明显向高温移动,最大损耗因子值及其对应温度都得到大幅度提高,且峰值增加到1.80左右,有效阻尼温域范围90℃以上。同时,AO-2246和PF的加入可以兼具提高CIIR基体材料力学性能,具有很好的实用价值。扫描电子显微镜(SEM)、差示扫描量热法(DSC)和傅里叶红外光谱(FTIR)的分析结果证明,AO-2246以无定形状态分散在CIIR/PF基体中,且AO-2246与基体CIIR之间形成了很强的分子间作用力,使材料的玻璃化温度大幅度上升。     

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)。