利用粘弹性阻尼结构研究聚氨酯的阻尼性能

合成了聚氨酯阻尼材料，并利用粘弹性阻尼结构研究了聚氨酯在0～1000Hz频率范围内的阻尼性能。分别讨论了云母填料含量、环境温度以及气泡对材料阻尼性能的影响。结果发现，填料较多的和不含气泡的材料的阻尼性能相对优异。随环境温度的升高，材料阻尼减振性能下降。     

高强度浇注聚酯型聚氨酯阻尼材料的研究

以不同种类的聚酯多元醇为软段,2,4-甲苯二异氰酸酯和3,3'-二氯-4,4'-二氨基二苯甲烷为硬段,合成了聚氨酯(PUR)阻尼材料.考察了不同软段结构、硫化温度和测试频率对PUR材料阻尼性能和力学性能的影响.结果表明,所制备的可室温硫化并具有优异力学性能的PUR阻尼材料,其拉伸强度达到12.9 Mpa,1 Hz时的tanδmax达到0.79,tanδ>0.3的阻尼温域达到45.5℃(-13.0～32.5℃).     

足球用聚氨酯材料的阻尼性能研究

人工草料及填充橡胶材料在制作过程中容易产生气泡,导致阻尼性能较差,影响足球弹性.为了解决这个问题,提出了足球用聚氨酯材料的阻尼性能研究.分析了不同分子链组成对聚氨酯分子结构和弹性的影响.利用阻尼结构研究了聚氨酯在0～800Hz频率范围内的阻尼性能,并分析了填料和气泡产生对阻尼性能影响.通过对性能分析发现,填料较多阻尼性...     

DOPO超分子作用硅橡胶阻尼材料多参数动态力学性能研究

将9,10-二氢--9氧杂-10-磷杂菲-10-氧化物(DOPO)接入多乙烯基硅油制得含DOPO的多乙烯基硅油,并用于白炭黑的改性。以苯基硅橡胶为基料,添加改性白炭黑制得具有超分子作用的硅橡胶阻尼材料。研究了阻尼材料在温度、频率、振幅多参数环境下的动态力学性能。结果表明:在实验范围内,材料的储能模量随着频率的增加而提高,随着温度、振幅的增加而减小,储能模量变化范围为0. 214～1. 57MPa;损耗模量随着温度的增加而减小、随着频率的增加而提高、随着振幅的增加而先增后减,变化范围为0. 0194～0. 303 MPa,损耗模量最大值在233 K、100 Hz、30μm处;损耗因子随着温度的升高而减小,随着频率、振幅的增加而增大,变化范围为0. 0855～0. 416。材料的储能模量及损耗模量在低温(280 K)、低振幅(50μm)、低频率(20 Hz)环境下变化幅度较大,且均在温度、频率、振幅增长后逐渐趋于稳定。     

橡塑阻尼材料的研究进展

介绍了橡塑阻尼材料的阻尼机理,重点介绍了丁基橡胶、硅橡胶、丁腈橡胶和聚氨酯改性制备阻尼材料的最新进展及应用,指出提高损耗因子、拓宽阻尼温域及频率范围是橡塑基高性能阻尼材料的研究方向.总结了橡塑阻尼材料在未来工程应用中的应用方向和发展趋势,为橡塑阻尼材料的应用研究提供参考和建议.     

短纤维增强苯基硅橡胶隔振器振动特性研究

以芳纶短纤维和苯基硅橡胶为原料制得硅橡胶阻尼材料,进一步制得隔振器,研究了芳纶短纤维含量对隔振器阻尼性能和隔振性能的影响。结果表明,在实验范围内,随着短纤维用量的增加,隔振器的阻尼性能先增后减,隔振器的阻尼因子在短纤维体积分数为6. 1%时达到最大值。在低频阶段,隔振器的振动响应量值均大于振动控制量值。随着短纤维的加入,阻尼材料的弹性模量持续增加引起隔振器刚度增加,从而导致隔振器共振频率增大。当短纤维体积分数为6. 1%时,隔振器在共振区的功率谱密度值最小,最大值仅为0. 104 g~2/Hz,同时隔振效率不仅没有降低,反而增加至68. 9%。     

氯化丁基橡胶阻尼材料动态力学性能的影响因素研究

利用DMA242热机械分析仪,研究了增粘树脂类型、高耐磨炉黑用量、测试频率等因素对氯化丁基橡胶阻尼材料动态力学性能的影响。结果表明,增粘树脂对材料动态力学性能具有显著影响,加入3^#增粘树脂材料的损耗因子峰值最大,损耗因子峰值温度最高;随着高耐磨炉黑用量增大,材料的损耗因子峰值降低、损耗因子峰值温度升高;随着测试频率由3．33Hz到1．66Hz逐渐减小,材料的损耗因子峰值温度逐渐降低,损耗因子峰值逐渐减小。     

橡胶阻尼及高阻尼材料研制

介绍了橡胶材料阻尼的一般原理、主要测试和表征方法，根据有关原理研制的阻尼材料在0～30℃和10～100Hz测试条件下具有高阻尼性能，用此阻尼材料制作的约束层阻尼结构样品，采用悬臂梁法测试(厚度比：冷拉钢板／阻尼材料／玻璃钢=2／6／2)具有高损耗因子。     

聚氨酯弹性材料阻尼性能的研究

利用粘弹性阻尼结构研究了聚氨酯阻尼材料在0～1000Hz范围内的阻尼性能。制备了不同填料含量的聚氨酯阻尼材料,并用它们构成两种粘弹性阻尼结构,分别测试了两种结构的加速度导纳曲线。测定了不同温度下结构上对应点的加速度导纳,研究结果表明,填料云母含量的增加有利于提高材料的阻尼减振性能,随着温度的升高,材料的阻尼减振性能呈下降趋势。     

高阻尼橡胶试验方法研究

研究高阻尼橡胶试验方法。结果表明:频率为1Hz时,动态力学分析仪(DMA)测试的试样tanδ在玻璃化温度(27℃)下达到峰值0.918,随频率升高,阻尼峰向高温方向移动;温度为25℃时,动态疲劳试验机测试的试样tanδ随着频率的增大先增大后减小,在频率为17Hz时达到最大值;动态疲劳试验机测试得到的tanδ较DMA测定值低;采用二片法剪切试验,频率为0.05Hz时等效阻尼比随剪应变的增大而增大。     

Very low frequency (down to 3 × 10 Hz) impedance measurements on a hanging mercury drop electrode

The authors describe an experimental set-up, using transfer function analysers, which allows for the impedance of a hanging mercury drop electrode to be measured at frequencies as low as 3 × 10⁻³ Hz, and for the low frequency limit of that impedance to be compared with the slope of the current-voltage curve. The device is applied to the reduction of the persulfate anion in a 1 M LiCl solution, in a region of potential where the current-voltage curve has a negative slope.     

Particle Size Measurement of Metallic Iron in Reduced Materials Based on Optical Image Analysis

The size of metallic iron particles in coal‐based reduced materials was measured by optical image analysis in three different reduced samples. The obtained data were analyzed by frequency and cumulative distribution. The results reveal that optical image analysis successfully measured the particle size of metallic iron in the reduced samples. The frequency distribution curves or cumulative passing percentage of metallic iron particles exhibit almost the same trend with respect to particle size. The quality of curve fitting indicates that the exponential decay function and Rosin‐Rammler equation represent well experimental data on frequency distribution and cumulative passing percentage, respectively.     

负压空气橡胶隔振器静态特性研究

设计了一种基于负压空气和帘线-橡胶复合气囊的全新低频隔振器,建立了有限元分析模型,得出的静态力学特性与试验结果吻合较好,验证了有限元模型的正确性;同时,研究了不同负压腔室压力大小下的特性曲线。结果表明,负压空气橡胶隔振器具有良好的低频隔振特性。     

Amplitude–frequency characteristics of polymer electro‐magnetic dynamic tri‐screw extrusion

The mechanism of plastic forming and processing in electromagnetic dynamic tri‐screw extruder is very sophisticated and the investigation of amplitude–frequency characteristic acts as the foundation of equipment design and the optimization of polymer processing parameters. A mathematical and analytical model of plastic forming in such extruder was developed and the results were nondimensional‐normalized. To validate the mathematical solutions experiments based on LDPE were carried out and the experimental vibration amplitude and vibration frequency curve was obtained. Three conclusions can be drawn herein: (1) the experimental results hold a good agreement with the calculations, and thus the feasibility of the proposed model is validated; (2) the possibility of resonance closely relates to polymer melt viscosity, rotating speed, and geometry parameters of the screw; (3) resonance of the tri‐screw extruder is seldom observed under normal conditions and there exists an inverse correlationship between vibration frequency and amplitude. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122:1778–1784, 2011     

Heat Transfer between Immersed Horizontal Tubes and Aerated Vibrated Fluidized Beds

Heat transfer coeffients between an immersed horizontal tube and an aerated vibrated fluldlzed bed are measured. There is a maximum value in the h-Г experlmental curve. The heat trander coefllcient increases with decreases in particle diameter in the fully fluidized region. The particle density has less effect on the heat transfer coetftclents. High smplltude and low frequency, or low amplitude and high frequency are favorable to heat transit. Exceedingly high gas veloclty is unfavorable to the surface-bed heat transfer. A model based on the ‘pocket‘ theory was proposed for predicting the surface-to-bed heat trausfer coefllclents in fully fluldlzed region. The predlctlons from the model were compared with observed data The reasonable fit suggests the adequacy of the model.     

Design of ethylene-propylene-diene monomer foam and its double-layer composite for improving sound absorption properties via experimental method and theoretical verification

In this work, the ethylene-propylene-diene monomer (EPDM) foam was fabricated via 4-4′-oxobisbenzenesulfonyl hydrazide (OBSH) and phenolic resin (PF) in an effort to prepare the sound-absorbing composite which has excellent sound absorption at the medium and low frequency. For single-layer EPDM foams, cell morphology showed a certain pattern, causing the peak of the sound absorption coefficient move to a higher frequency and the peak value reached a maximum of about 0.75 as the OBSH content increased. In addition, with the foaming temperature increasing, the cell morphology had a different tendency and the peak of the sound absorption coefficient moved first to the higher frequency and then to the lower frequency due to the vulcanization reaction. Compared with the single-layer EPDM foams, the sound absorption curve of the double-layer composite made of the single-layer EPDM foam and pure EPDM sheet with cavities moved to a lower frequency by about 400 Hz. The theoretical calculation method was used to verify the accuracy of the experimental results. This work provided a simple approach to control the sound absorption property of EPDM foamed material and its double-layer composite through from an experimental and theoretical perspective.     

Nonlinear dynamic behavior of rubber compounds: Construction of dynamic moduli generalized master curves

The nonlinear dynamic behavior of a vulcanized rubber compound employed in the production of tires was investigated. The values of the dynamic storage modulus, E', and the loss factor, tanδ, were measured at different frequencies, temperatures and strain amplitudes. Data were subsequently analyzed and treated by an empirical method of frequency‐temperature‐deformation reduction that provided for E' and tanδ, respectively, a single master curve and the frequency‐temperature and frequency‐deformation shift factors. The E' trend, extrapolated at higher strain amplitudes on the basis of the master curves, resulted in good agreement with E' values obtained from direct experimental measurements.     

曲线拟合约束稀疏脉冲反演技术在薄储层中的应用研究

各种测井曲线对同一地质体有不同的地球物理场响应,它们之间存在一定的相关性,由于这种相关性非声波测井曲线可以拟合出声波曲线进行约束反演。本文以某陆相薄砂泥互层为例,针对原始声波测井曲线对薄砂体不敏感而伽玛测井曲线的高频成份对砂泥岩性变化敏感,同时与声波时差之间具有很好的相关性,利用小波多尺度分解对声波中的低频信息进行了提取,应用统计回归加低频的方法对曲线进行了重构。然后,在Jason里面用拟合曲线进行约束稀疏脉冲反演,拟合曲线反演显著地突出了所需的信息,有效地提高了对砂岩的识别能力。     

X-ray diffraction and computational studies of the modulus of silk (Bombyx mori)

X-ray diffraction with the assumption of uniform stress has been used for determining the crystal modulus of polymers. Values of the modulus of silk obtained previously using such an approach were found to be an order of magnitude lower than, those obtained by computational modeling. The differences are outside the limits of experimental and computational errors. This study re-examined the values in an improved manner. For the X-ray technique, moduli of different samples along the length of cocoon fibers were measured. The values obtained are 20-28 GPa depending on the crystallinity index and degree of orientation of the samples. For the computational calculation, the longitudinal acoustic mode (LAM) frequency of silk systems having three different c-axis dimensions were calculated. An acoustic dispersion curve was generated from the frequency values. The slope of the curve at the origin gave a crystal modulus of 13 GPa. A 3D-fluctuation analysis yielded an average modulus of approximately 16 GPa. These low values result from the out-of-plane torsioning of molecules in the β-pleated structure of the silk crystals. The experimental and computational results are in reasonable agreement with one another as well as with data reported in the literature for other pleated molecules.     

RHEOLOGICAL PROPERTIES OF SBS-ASPHALT COMPOSITES AT HIGH DEGREE OF MODIFICATION

Rheological properties of Styrene-Butadiene-Styrene (SBS)-Asphalt composites were studied as a function of the SBS concentration, frequency, and temperature. The experimental data were fitted by using the percolation model, aiming to predict the rheological behavior of this composite at any specific composition, temperature, and frequency. This was achieved through a WLF-type relationship that has been extended to allow composition to be considered. This extended WLF is conceptually supported by a free volume theory, allowing to generate master curves with shifts in temperature (Log aT) and in concentration (Log aC). The temperature-concentration displacements (Log aTC) and the concentration-temperature displacements (Log aCT) were well fitted, producing practically the same super-master curve, demonstrating that this model applies well to both types of shifts.