【作者】 顾健；

【导师】 武高辉；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 博士

【摘要】 高速运动飞行器、运载器在运行过程中会遭受严重的振动和噪声困扰,为了解决上述问题,本文试图设计一种轻质、廉价的阻尼灌封材料,灌注到钢管中提高构件的阻尼减振特性,而不改变构件的原有结构。本文从材料设计的角度出发,设计和制备了廉价、轻质和高阻尼的空心球（粉煤灰空心微珠和Al₂O₃空心球）/环氧（EP）多孔材料。利用扫描电镜（SEM）、热重分析（TG）和动态力学分析（DMA）等手段系统研究了多孔材料的微观组织、热性能和阻尼性能,并分析了相关影响因素。通过敲击法和振动台法研究了空心球/环氧灌封钢管的阻尼减振规律。本文所用的粉煤灰空心微珠球径为74²06μm,主要成分为SiO₂和Al₂O₃;Al₂O₃空心球球径为0.5⁴mm。基体为90%环氧树脂和10%聚氨酯（90EP-10PU）。研究表明,随着空心球体积分数（V_f）和平均球径的增大,多孔材料密度下降。当空心微珠V_f为50⁷0vol.%时,材料的密度为0.80⁰.93g/cm³;当Al₂O₃空心球V_f为88vol.%时,多孔材料的密度可低至0.58⁰.62g/cm³。研究发现,经过偶联剂表面改性以后,空心微珠与基体界面结合良好,材料的破坏源于空心微珠自身断裂。当V_f为30⁵0vol.%时,空心微珠在基体中的分散性较好;当V_f>50vol.%后,空心微珠互相堆积造成了基体不连续,产生少量缺陷。随着空心微珠V_f和球径的增大,多孔材料的初始热分解温度和10%热失重对应的温度都升高。根据Arrhenius公式算得的氧化分解活化能也是逐渐增加,表明添加空心微珠后,多孔材料的耐热性得到改善。空心微珠/（90EP-10PU）多孔材料在变温（-40¹50℃）和变频（10⁸00Hz）条件下的阻尼性能研究表明,多孔材料的tanδ峰值介于0.628⁰.892之间,都高于基体（0.536）,且玻璃化转变温度（T_g）向低温偏移,高阻尼温域(ΔT_0.5)拓宽。在tanδ^f图中,随着频率的升高,tanδ衰减较慢,阻尼性能保持稳定,说明频率对多孔材料损耗因子的影响要小于温度对其的影响。tanδ与空心微珠V_f、球径和种类的相关规律研究表明:tanδ对于V_f存在一个峰值,当V_f为30vol.%时,tanδ峰值为0.892;随着空心微珠球径和种类的变化,tanδ峰值之间的变化值小于10%,说明空心微珠V_f对于多孔材料阻尼性能的影响要比球径和种类对其影响更明显。空心球/（90EP-10PU）灌封钢管结构阻尼因子（η）达到（5⁹）×10^-2,比钢管自身（7×10-3）提高了6¹2倍。随着阻尼层厚度增加,灌封钢管的η增大;随空心微珠Vf的增大,η先增大后减小,当空心微珠Vf为30⁵0vol.%时,灌封钢管的η达到峰值（8⁹）×10-2;模态阻尼与空心球球径和种类的相关性不明显（Δη<1%）。根据所建立的壳单元-体单元模型、选择固定-自由边界条件,采用模态应变能（MSE）法计算得到空心球/（90EP-10PU）灌封钢管的结构阻尼因子与测试值比较接近。空心球/（90EP-10PU）阻尼材料灌封Q235钢管后使钢管的一阶固有频率（f1）降低10³2Hz。f1随着空心球Vf的增加而增加,而与球径的相关性较小;f1随着阻尼层厚度的增加而降低。灌封钢管的阻尼特性与振动频率相关规律表明,在小于2 f1低频条件下,灌封钢管的减振传递率（T）大于1,不具有阻尼减振效果;在> 2 f1,250²000Hz范围内,T为0.15⁰.64,随着振动频率的增加缓慢升高,振动传递较钢管降低4.5⁰.5倍。灌封钢管阻尼特性取决于灌封阻尼材料的阻尼性能。当空心微珠Vf为30vol.%,球径为120μm时,多孔材料和灌封钢管的阻尼性能都达到最佳,此时灌封钢管的结构阻尼因子为8.82×10-2。更多还原

【Abstract】 To solve the severe vibration and noise problem of high-speed moving aircraft and vehicle in their running process, my research attempts to design a lightweight and cheap damping encapsulating material, which can be poured into the steel pipes to enhance the structural damping characteristics but do not change the pipes’ original structure. In this dissertation, two types of hollow spheres （fly ash （FA） and Al₂O₃ hollow sphere（HS）） are filled into the modified epoxy to prepare the low cost, low density （0.58⁰.93g/cm3） and high damping porous composites. By means of scanning electron microscope（SEM）, thermogravimetric analysis（TG）, and dynamic mechanical analyzer（DMA）, the microstructure, thermal properties as well as damping properties of porous composites are investigated systematically. The modal damping characteristics and vibration damping characteristics of encapsulating pipes are measured by using the strike method and shaking table method for the first time.The particles size of the fly ash and Al₂O₃ hollow sphere used in my paper are 74²06μm and 0.5⁴mm. The matrix is 90% epoxy resin-10% polyurethane （90EP-10PU）. Research shows that the densities of the porous composites decrease linearly with the increasing Vf and particles size of cenosphere FA. When Vf is 50⁷0vol.%, the density of fly ash/（90EP-10PU） can reduce to 0.80⁰.93g/cm3. For the Al₂O₃ hollow spheres/（90EP-10PU） porous composites, their densities are 0.58⁰.62g/cm3 with the Vf of 88vol.%.The interface behavior between FA and the matrix is not a“free interface”, but a“weak bonding interface”when the FA is surface-modified by the silane coupling agent. When Vf is 30⁵0vol.%, the FA spheres are dispersed homogeneously in the matrix with farthing holes, and the fracture of the porous composites is caused by the rupture of FA spheres. When Vf>50vol.%, the defects are brought by the discontinuity of the matrix and the accumulation of FA spheres.Thermogravimetric （TG） test shows that the initial decompositions temperatures and the temperatures of 10% thermal weight loss for porous composites both enhance with increasing Vf and particles size of FA. The oxidative decomposition activation energies increase gradually, which indicates the heat resistance of the FA/（90EP-10PU） porous composites is improved.The damping properties of the FA/（90EP-10PU） porous composites in the temperature range from -40 to 150oC and in the frequency range from 10 to 800Hz are studied systematically. The peak values of loss factor（tanδ） are 0.628⁰.892, the glass transition temperatures（Tg） shift to low temperature, and the high damping temperature region（ΔT0.5） widen. In tanδ^f curves, the attenuation of tanδis more slowly with the increase of frequency, which indicate that the damping properties of porous composites can keep stable.The research on the change of tanδwith the volume fraction （Vf）, particles size and kinds of FA microspheres shows that there is a peak in the tanδ^Vf curves. When the Vf is 30vol.%, the peak values of tanδare 0.892. The variation of peak values of tanδis less than 0.1 with the change of particles size and kinds of FA microspheres. This indicates that the effect of fly ash Vf on the damping properties of porous composites is more important.The studies on modal damping characteristics of hollow spheres/（90EP-10PU） encapsulating Q235 pipes show that the structural damping factor（η） of the encapsulating pipes are （5⁹）×10-2, which is （6¹2） times higher than that of Q235 pipe. The effect of impulsive force on the modal damping characteristics is not significant. The thicker of the composites damping layers, the better of the modal damping characteristics. In addition, the effects of Vf, particles size and types of hollow spheres on modal damping characteristics are analyzed. Results reveal that theηincreases at first then decreases with increasing Vf of FA. When the Vf is 30⁵0vol.%, theηis （8⁹）×10-2.ηhas no obvious change（Δη<0.01） with the variation of particles size and types. The Modal Strain Energy（MSE） method belonging to the finite element software is applied to calculate the structural damping factors of the hollow spheres/（90EP-10PU） encapsulation pipes firstly. The results show that the calculation values are basically consistent with the experimental data by the establishment of shell-solid element model and selection of fixed-free boundary conditions.The studies on vibration damping characteristics of hollow spheres/（90EP-10PU） encapsulating Q235 pipes indicate that the first order natural frequency （f1） of Q235 pipe decreases by 10³2Hz with the addition of fly ash and Al₂O₃ hollow spheres. The natural frequencies of hollow spheres/（90EP-10PU） encapsulation pipes enhance with the increase of the Vf of hollow spheres, but which is changed little with the variation of the particles size; the natural frequencies of hollow spheres/（90EP-10PU） encapsulation pipes decrease with the increasing thickness of damping composites. The studies on the relationship between the vibration damping characteristics and the vibration frequency show that the vibration transmissibilities （T） of each encapsulating pipes are more than 1 when the frequency is less than 2^1/2 f1, which indicates that the encapsulating pipes have no damping effect in this frequency region. At the frequency of 250²000Hz, the T of each encapsulating pipes are 0.15⁰.64, which reveals that the T of each encapsulating pipes increase slowly, and the vibration transmission decrease 4.5⁰.5 times.The structural damping characteristics of encapsulating pipes depend on the damping properties of hollow spheres/（90EP-10PU） porous composites. Researches show that the fly ash/（90EP-10PU） porous composites and their encapsulating pipes both have the superior damping properties when the fly ash volume fraction is 30vol.% and particles size is 120μm.更多还原