约束型复合阻尼隔声板的隔声性能及其应用研究

约束型复合高阻尼隔声板具有良好的隔振、隔声性能,特别适用于对隔声结构的厚度有苛刻要求的场合。对影响约束型复合高阻尼隔声板主要结构参数的研究,有利于指导其设计、制造和应用选择。根据对约束型复合高阻尼隔声板隔声计算模型的计算与实验表明,当隔声板的面积减小时,其低频隔声量会随之增加;当隔声板阻尼层的厚度等量递增时,其隔声量也近似等比例地提高;当面板材料的弹性模量较小时,隔声板的低频和高频的隔声量都会变差;当隔声板阻尼层剪切模量较高时会导致隔声量偏低。     

玻璃纤维复合材料板隔声性能的研究

选择树脂基玻璃纤维复合材料板,测量其辐射效率和损耗因子,研究纤维排布方式及纤维用量的影响,结果表明,纤维正交和单向铺设对玻璃纤维板辐射效率的影响基本相同,纤维的用量在10%~70%变化时,也没有明显的变化;对损耗因子的影响,在160~1000Hz范围内,单向玻纤复合材料板的阻尼比正交排布的低,而在2000~8000 Hz范围两者基本相同的。在中低频范围内,正交排布比单向排布对阻尼的影响更加显著。通过测试复合材料和金属铁的隔声量,在160~8000Hz范围内,玻璃纤维复合材料板没有出现隔声谷。提出纤维复合材料板中纵波波速公式,计算复合材料板的隔声量,与测量结果吻合良好。     

柔性吸声隔音降噪纺织复合材料

柔性吸声隔音降噪纺织复合材料由于能够提供比传统纺织品更宽的吸声域,比传统降噪材料轻薄、柔软、透气和易加工而备受关注。开发基于纺织材料的聚合物复合材料是近年来噪声控制领域的热点研究方向之一。本文从新型纤维、降噪功能填料和柔性降噪纺织复合材料3个方面综述了国内外柔性吸声隔音纺织品的研究进展,并归纳总结了柔性降噪纺织品的制备方法,进一步对柔性吸声隔音降噪纺织品的发展趋势进行了展望。     

重质粒子/NBR-PVC微孔阻尼复合材料的制备及其隔声性能

为了制备一种轻质高效的隔声材料,本研究以丁腈橡胶（NBR）和聚氯乙烯（PVC）共混为主体材料,采用一步模压发泡工艺制备了重质粒子（HMP）/NBR-PVC微孔阻尼复合材料。通过SEM、动态力学分析和声阻抗管测试探究了橡塑比对HMP/NBR-PVC复合材料泡孔结构、阻尼性能和隔声性能等方面的影响,并进一步对其隔声机制进行了分析。研究结果表明：微孔结构的存在增加了声能量在材料内部传播过程中的衰减,提高了HMP/NBR-PVC复合材料的隔声性能。NBR与PVC质量比为50：50的HMP/NBR-PVC微孔阻尼复合材料具有良好的泡孔结构、力学性能和阻尼性能,其隔声指数高达28.1 dB。这种质轻、质软且易加工的橡塑微孔阻尼复合材料对新型隔声材料开发与应用具有一定的指导意义。     

低温环境下复合材料飞机壁板结构隔声特性研究

环境温度变化影响复合材料壁板的隔声性能,关系到飞机舱内噪声水平,是一个亟待研究的问题。文章开展常温和低温状态下的隔声建模方法研究,然后搭建常温和低温环境下的复合材料壁板结构隔声性能测试系统,实测结果和数值计算结果基本一致。最后通过大量隔声试验,获得复合材料壁板低温环境下的隔声性能特点,进一步分析温度从-40℃~40℃变化时复合材料壁板在50～10 000 Hz 1/3倍频程的隔声规律。试验结果表明,在中心频率为50~500 Hz时,复合材料壁板在低温环境下的隔声性能总体好于常温下的隔声性能,且温度对壁板隔声量的影响较大。     

An optimization of composite lattice cylinder using the approximate method

Recently, the approximate methods based on continuous models have been developed to perform structural analysis of composite lattice structures due to their relative simplicity and computational efficiency. This paper defines the modified effective stiffness considering the directionally dependent mechanical properties to an intersection of ribs and mode shape function of a composite lattice cylinder. It subsequently presents an approximate method based on the continuous model of conducting a buckling analysis of the composite lattice cylinder with various boundary conditions under uniform compression. This method considers the coupled buckling mode as well as the global and local buckling modes. The validity of the present method is verified by comparing the results of the finite element analysis. In addition, a parametric analysis is performed to investigate the effects of the design parameters on the critical load and buckling mode shape of the composite lattice cylinder based on the present method. Finally, we apply the present method to perform the optimization of a composite lattice cylinder for a high-speed vehicle to minimize the mass. Consequently, it is concluded that the present method is very suitable to optimization of composite lattice cylinders due to their relative simplicity and computational efficiency.     

泡沫铝材料对发电机噪声的隔音性能研究

采用泡沫铝材料对柴油发电机的混合频率噪音进行隔音处理,分析了发电机噪声的频谱特点,将不同孔结构、不同厚度、不同复合方式的泡沫铝材料应用于发电机外壳,并比较了隔音效果。研究结果表明,泡沫铝材料对于发动机的混合型噪音,在高频段有明显的隔音效果,而在低频段隔音效果不明显。闭孔泡沫铝在大于500Hz的高频段的隔音效果比开孔的好,而在63~125 Hz的低频段,开孔泡沫铝的隔音效果好。泡沫铝与钢板复合后,对于低频噪声隔音效果有明显的作用。保持泡沫铝与钢板间一定的空腔距离,隔音频率段明显降低。20 mm厚度的闭孔泡沫铝与钢板复合并保持20 mm的空腔距离,可降低10~20dB的噪音。     

噪声敏感建筑隔声与声舒适性要求

住宅声学性能将在心理、生理和社会上影响住户,声学舒适性是高要求敏感建筑设计和施工中的重要考虑因素。文章对比分析了中国和欧美等国家隔声指标和要求的差异,发现国内住宅空气声隔声指标比国外的指标要求低4～10 dB;楼板撞击声压级比国外的要求高3～25 dB,最大偏差达到-25 dB。考虑到城市化进程的不断推进,城镇居住密度和容积率的不断增大,以及多高层居住建筑的大量应用,以预期满意度50%～67%为目标,建议住宅声学设计标准在现有的标准和规范基础上提高5 dB左右,以期改善住宅的声学品质和住户的声学满意度,而后期开展相应的声学社会调查,改善居住声学环境是十分必要的。     

Cracked semi-infinite cylinder and finite cylinder problems

This work considers the analysis of a cracked semi-infinite cylinder and a finite cylinder. Material of the cylinder is assumed to be linearly elastic and isotropic. One end of the cylinder is bonded to a fixed support while the other end is subjected to axial tension. Solution of this problem can be obtained by superposition of solutions for an infinite cylinder subjected to uniformly distributed tensile load at infinity (I) and an infinite cylinder having a penny-shaped rigid inclusion at z = 0 and two penny-shaped cracks at z = ±L (II). General expressions for the perturbation problem (II) are obtained by solving Navier equations with Fourier and Hankel transforms. When the radius of the inclusion approaches the radius of the cylinder, the end at z = 0 becomes fixed and when the radius of the cracks approach the radius of the cylinder, the ends at z = ±L become cut and subject to uniform tensile load. Formulation of the problem is reduced to a system of three singular integral equations. By using Gauss–Lobatto and Gauss–Jacobi integration formulas, these three singular integral equations are converted to a system of linear algebraic equations which is solved numerically.     

Thermal performance of multilayer insulation around a horizontal cylinder

Thermal performance of multiplayer insulation (MLI) is affected by contact pressure between adjacent layers. In order to evaluate the thermal performance of the MLI fabricated in the horizontal cryostats of superconducting magnets, it is important to investigate the contact pressure in the MLI. In case of a horizontal cryostat, the MLI is wound around horizontal cylindrical surface and is compressed at the upper part of the cylinder due to the MLI self-weight. At first, a single thin film wound around the horizontal cylinder was analyzed to evaluate the contact pressure acting on the cylinder. The analysis has been extended to the multiply wound film around horizontal cylinder, in order to investigate the distribution of contact pressure between adjacent layers. By using experimental data obtained with a flat panel calorimeter, the results of this analysis have been applied to evaluate the thermal performance of MLI around a horizontal cylinder. And the non-dimensional contact pressure parameter P^* has been introduced as a useful parameter to evaluate and compare the thermal performance among different kinds of MLI.     

基于声学黑洞的复合隔声结构声学特性研究及试验

声学黑洞(Acoustic Black Hole,ABH)能够实现声波的聚集,通过粘贴阻尼层将其聚集的能量耗散,可有效降低声学黑洞复合结构的振动和声波的传递。针对中低频段噪声,设计了声学黑洞复合隔声结构,建立了其隔声量计算模型。研究了声学黑洞复合隔声结构的黑洞数量、黏弹性阻尼层、声学黑洞半径等参数对隔声性能的影响。研究结果表明：在160~1 000 Hz频率范围内,ABH能明显增加复合隔声结构的隔声性能,其传递损失在1/3倍频程内增加了1.9 dB。文中的研究结果为复合隔声结构的设计提供了借鉴。     

Continuous accretion of a composite cylinder

Summary A new model is derived for winding of a composite thick-walled cylinder with finite strains. Continuous growth of a cylinder is treated as a limit of successive accretion of built-up portions (thin-walled shells) consisting of a fiber bundles and resin. Due to preload of fibers, a gradient of pressure arises in the cylinder which causes resin flow. Nonlinear partial differential equations are developed which permit stresses and displacements in a wound cylinder to be determined with account for the material accretion and resin flow. At infinitesimal strains, these equations are reduced to a linear Volterra integral equation for pressure on mandrel. This equation is solved numerically to analyze the effect of material and structural parameters on stresses in a wound cylinder.     

Topology optimization of composite material plate with respect to sound radiation

In this paper, topology optimization of composite material plate with respect to minimization of the sound power radiation has been studied. A new low noise design method based on topology optimization is proposed, which provides great guidance for acoustic designers. The structural vibrations are excited by external harmonic mechanical load with prescribed frequency and amplitude. The sound power is calculated using boundary element method. An extended solid isotropic material with penalization (SIMP) model is introduced for acoustic design sensitivity analysis in topology optimization, where the same penalization is applied for the stiffness and mass of the structural volume elements. Volumetric densities of stiffer material are chosen as design variables. Finally, taking a simple supported thin plate as a simulation example, the sound power radiation from structures subjected to forced vibration can be considerably reduced, leading to a reduction of 20 dB. It is shown that the optimal topology is easy to manufacture at low frequency, while as the loading frequency increases, the optimal topology shows a more and more complicated periodicity which makes it difficult to manufacture.     

一种新型复合材料吸声的理论建模与仿真

建立了压电陶瓷/橡胶复合材料吸声的理论模型,给出了机电类比等效电路,数值仿真分析了材料参数变化时,电损耗效率和吸声系数的变化趋势.     

采用等效有限元模型的复合材料机翼结构优化

在机翼设计过程中,将等效有限元模型(EFEM)方法应用于考虑静力学和动力学要求的机翼结构优化。提出了"三步走"的结构优化策略,将一个多变量的复杂优化问题转换为一系列少变量的简单优化问题,对某支线客机的复合材料机翼进行了优化设计。首先以位移、静强度和颤振速度作为约束条件对机翼复合材料铺层比例进行优化;然后以静强度和结构稳定性作为约束,以最小化结构质量和结构效率作为优化目标,对各翼肋之间的加强壁板进行优化设计;最后再以位移和颤振速度为约束,对机翼结构总体刚度进行优化设计。结果表明:EFEM方法具有快速建模和计算量少的优点,采用"三步走"优化策略具有更高的效率,适用于初步机翼结构优化设计。     

尼龙66纤维/6061铝合金复合板静电植绒工艺及隔声性能

为研究不同植绒工艺条件下尼龙66纤维/6061铝合金复合板的植绒性能与隔声性能,首先,采用静电植绒工艺将6061铝合金板与尼龙66纤维复合,制成隔音复合板;然后,研究了植绒时间、植绒电压、极板间距以及胶黏剂涂覆量等工艺参数对植绒面密度和植绒纤维耐磨性能的影响;最后,利用混响室-消声室法研究了尼龙66纤维/6061铝合金复合板在不同入射声频下和不同纤维结构参数时的隔声性能。结果表明:在0~40s植绒时间范围内,随着植绒时间的延长,植绒面密度持续增大,而后保持不变;同时,在0~90kV电压范围内,随着电压的增加,植绒面密度连续增大,而后因极板间距不同植绒面密度增大或减小;植绒纤维的耐磨性能随胶黏剂涂覆量的增加而提高,但当涂覆量超过155g/m2后会产生气泡;当植绒时间为40s、植绒电压为90kV、极板间距为11.5cm且胶黏剂涂覆量为155g/m2时,尼龙66纤维/6061铝合金复合板的性能最好。该复合板具有较高的中高频隔声性能,隔声量在500~1 600Hz频率范围内满足6dB/倍频程规律;在2 000Hz后出现吻合效应。提高植绒面密度以及减小尼龙66纤维直径均可增大该尼龙66纤维/6061铝合金复合板的隔声量。研究结论可为建筑用新型隔音复合材料的开发与应用奠定基础。     

基于扩展有限元的钢瓶爆破数值仿真研究

金属钢瓶的爆破压力是其重要的安全技术指标,目前的数值计算方法不能有效对气瓶的爆破压力进行准确预测。提出了基于扩展有限元的数值计算方法对钢瓶的爆破进行了数值仿真,仿真结果表明该方法能准确预测钢瓶的爆破压力,可以为钢瓶工程设计和事故预防提供支撑。     

不同构造参数双层窗隔声性能试验研究

通过试验研究玻璃构造形式与规格、开启方式与密封形式、双层窗间距及窗框型材对双层窗隔声性能的影响,分析得出:玻璃构造形式与规格对双层窗的计权隔声量影响较小,其空气声隔声量频率特性曲线相近,低频共振频率主要出现在160~250 Hz范围;外平开/内推拉形式双层窗的隔声性能与双平开形式双层窗相当,均显著优于双推拉形式双层窗,且推拉窗采用包覆式密封条替换普通毛条,对提升外平开/内推拉形式双层窗的隔声量有一定效果;在相同条件下,当两层窗之间的间距大于90 mm时,双层窗构件的计权隔声量相近,隔声性能优于间距为80 mm的双层窗。