打孔闭孔泡沫铝的吸声能力

闭孔泡沫铝板具有一定的吸声性能,对闭孔泡沫铝板进行打孔处理后,其吸声效果显著提高.使用驻波管法测试不同打孔率以及在泡沫铝板背后设置不同厚度空腔时吸声系数和吸声频率的变化.测量结果表明:以适当的打孔率打孔后,吸声系数提高30%左右,打孔率过高,吸声系数反而降低;随着在泡沫铝吸声板后设置的空腔厚度的增加,吸声峰值向低频偏移.可通过改变打孔率和背后空腔深度来设计用于降噪的闭孔泡沫铝吸声结构.     

闭孔泡沫铝吸声性能的影响因素

利用熔体转移发泡法制备闭孔泡沫铝,从孔径大小、打孔率、背后空腔以及背后贴膜方面对其吸声性能进行研究.结果表明:孔径大的闭孔泡沫铝吸声系数要远好于孔径小的闭孔泡沫铝的吸声系数;打孔后闭孔泡沫铝吸声系数有了明显的提高,当分别打孔0.5%、1%和2%N,闭孔泡沫铝最高吸声系数从0.42分别增加到了0.53、0.75和0.96;打孔闭孔泡沫铝背后加空腔吸声曲线都表现出明显的亥姆霍兹共振器吸声特性,且随空腔厚度的不断增加,低频吸声系数逐渐增加,高频吸声系数逐渐降低,最高吸声系数向低频迁移;背后贴膜闭孔泡沫铝吸声特性曲线出现峰值吸声特征消失的现象,表现出吸声系数随频率增加而增加的特性.     

穿孔法改进泡沫铝的吸声性能

利用熔体发泡技术制备不同孔径和气孔率的泡沫铝,对不同气孔率的原始状态泡沫铝以及孔径为1.1 mm的穿孔泡沫铝的吸声性能进行研究。结果表明:未设置背腔时,原始状态泡沫铝的吸声性能不高,设置背腔后,由于泡沫铝中所含通透结构的作用,泡沫铝的吸声性能明显提高;穿孔泡沫铝的穿孔率在0.5%～1.0%范围,设置60～80 mm背腔时可使降噪系数超过0.42,比原始状态泡沫铝不设置背腔时的降噪系数高2倍左右;穿孔泡沫铝设置背腔后的吸声特性符合Helmholtz共振吸声的规律,但受到穿孔结构、泡沫铝原本存在的缺陷组成的通透结构和气泡孔在穿孔过程中被打开的小开口等因素的影响。     

泡沫铝吸声性能的研究

本文通过测试泡沫铝的吸声系数来研究泡沫铝的吸声性能。结果表明，泡沫铝具有较好的吸收性能，其吸声系数对于频率很敏感，大约在1000Hz时吸声系数出现一个峰值。吸声系数随孔结构的变化有一定的规律性。     

建筑用降噪泡沫铝合金的吸声性能研究

制备了3种特殊孔结构的Al-Si12泡沫铝,并研究了特殊孔结构对泡沫铝吸声吸能的影响。结果表明,与常规单一孔结构泡沫铝相比,特殊孔结构泡沫铝在高频区和低频区的吸声效果较强,而在中频区吸声效果相对较差。对于层状周期孔结构、层状梯度孔结构和宽孔径范围孔结构的泡沫铝,层状周期和层状梯度的层数越多或孔隙率越大,其吸声吸能越好。     

特殊孔结构ZA27合金泡沫的吸声性能

通过渗流铸造法制备宽孔径范围、层状梯度、层状周期3种特殊孔结构的ZA27合金泡沫,并对其吸声性能进行研究。结果表明:随频率的升高,低频区吸声系数增加,中频区吸声系数降低到一个最小值后上升,高频区吸声系数趋于平缓;宽孔径范围ZA27合金泡沫随孔径变化及孔隙率的增加吸声系数平均提高0.025层数多的层状梯度孔结构的吸声性能相对层数少的梯度孔结构平均提高0.037层数多的层状周期孔结构的吸声性能比层数少的周期孔结构平均提高0.027特殊孔结构ZA27合金泡沫在低频区的吸声性能优于特殊孔结构Al-Si12合金泡沫的。     

特殊孔结构Al-Si12泡沫铝的吸声性能研究

用渗流铸造法制备了3种特殊孔结构(宽孔径范围孔结构、层状梯度孔结构、层状周期孔结构)的Al-Si12泡沫,对其吸声性能进行了研究。结果表明,相同厚度下,层数多的层状梯度孔径结构泡沫铝的吸声性能优于层数少的梯度孔径结构泡沫铝;层数多的层状周期孔结构泡沫铝的吸声性能比层数少的周期孔结构泡沫铝的吸声性能略有提高;具有4层周期孔结构的Al-Si12泡沫铝样品具有较好的吸声性能,其平均吸声系数为0.82,比常规单一孔径结构的泡沫铝的平均吸声系数提高了0.21,其原因与扩张室结构、流阻及微型谐振腔有关。     

Ti40合金热压缩变形过程的开裂行为研究

用渗流铸造法制备了3种特殊孔结构(宽孔径范围孔结构、层状梯度孔结构、层状周期孔结构)的Al-Si12泡沫,对其吸声性能进行了研究.结果表明,相同厚度下,层数多的层状梯度孔径结构泡沫铝的吸声性能优于层数少的梯度孔径结构泡沫铝;层数多的层状周期孔结构泡沫铝的吸声性能比层数少的周期孔结构泡沫铝的吸声性能略有提高;具有4层周期孔结构的Al-Si12泡沫铝样品具有较好的吸声性能,其平均吸声系数为0.82,比常规单一孔径结构的泡沫铝的平均吸声系数提高了0.21,其原因与扩张室结构、流阻及微型谐振腔有关.     

铝纤维复合板结构参数对吸声性能的影响规律

利用吸声材料降噪是治理变电站噪声污染的重要途径。以铝纤维、铝箔、铝板网为原料,采用冷轧法制备具有不同结构参数的铝纤维复合吸声板,采用阻抗管的标准测试方法检测铝纤维复合板吸声系数,研究材料的纤维板面密度、空腔厚度、纤维种类等参数对材料吸声性能的影响。结果表明:试验采用的铝纤维复合板具有优异的吸声性能,采用切削法纤维及面密度为484 g/m2的铝纤维复合板吸声性能最好;随空腔厚度的增大,吸声系数的峰值向低频段移动。     

穿孔板组合对电沉积泡沫镍吸声性能的影响

目前由穿孔板和多孔金属组成的多层吸声结构的吸声性能还没有充分的研究。本研究提出了一种由穿孔板和吸声材料进行多层穿插叠合的组合吸声结构,通过调整多孔金属吸声材料的叠合层厚度,改变穿孔板位置和数量的方法控制吸声效果。对测试结果与传递矩阵数学模型拟合计算的结果进行对比分析,从理论上探讨其吸声原理并比较其吸声性能的优劣。结果表明:用该方法可以极大提升泡沫镍材料的吸声效果,在这种组合结构中以加入三层穿孔板为最佳匹配,最佳匹配与传递矩阵模型公式的计算数据基本吻合。     

Sound absorption property of open-pore aluminum foams

The sound absorption property of aluminum foam was studied by testing its sound absorption coefficients using standing wave tube method. The open-pore aluminum foams were prepared by infiltration process, with pore size of 0.5 mm to 3.2 mm and porosity of 54.2% to 77%. The frequency of indicted sound wave was ranging from 125 Hz to 10 kHz. The results show that the average values of sound absorption coefficients are all over 0.4 and the aluminum foam has better sound absorption property, its coefficients is influenced by frequency and pore structure, and reaches the maximum at about 1 kHz, with increasing porosity and decreasing cell diameter the sound absorption coefficient values increase.     

Sound absorption property of open-pore aluminum foams

This paper presents a study on sound absorption property of aluminum foam by evaluating its sound absorption coefficients using standing wave tube method. Experimental results showed that the average values of sound absorption coefficients (over the test frequency range) are all above 0.4, which indicate very good sound absorption property of the aluminum foams. The sound absorption coefficient is affected by frequency and pore structure, and reaches its maximum value at around 1 000 Hz. With the increase of porosity and decrease of cell diameter, the sound absorption coefficient values increase.     

Sound absorption of several various nickel foam multilayer structures at aural frequencies sensitive for human ears

Using the three-dimensional reticular nickel foam as experimental material, the sound absorption performance was investigated for several various multilayer structures in the frequency range of 2000–4000 Hz, which is aurally sensitive for human ears. The results showed that the 7.5 mm-thick foam sample, which was formed by piling of 5-layer foam plate (thickness: 1.5 mm; porosity: 96%; average pore-diameter: 0.65 mm) could exhibit an excellent sound absorption effect at 4000 Hz, with the absorption coefficient about 0.8. Constituting alternate air gap with the total thickness of about 18.5 mm can greatly improve the absorption performance at relatively low frequencies of 2000–3150 Hz, with the absorption coefficient up to about 0.5 or more. In addition, the research showed that alternate piling up the perforated plate inside the foam plates can also achieve a quite good effect of sound absorption at relatively low frequencies.     

Sound insulation property of Al-Si closed-cell aluminum foam bare board material

Al-Si closed-cell aluminum foam bare boards of 1 240 mm×1 100 mm with different densities and thicknesses wereprepared by molten body transitional foaming process.The sound reduction index(R)of Al-Si closed-cell aluminum foam bareboards was investigated experimentally under different frequencies(100-4 000 Hz).It is found that sound reduction index(R)issmall under low frequencies,large under high frequencies and is controlled by different mechanisms.The sound insulation propertybasically conforms with the monolayer board sound insulation theory.The sound reduction index(R)increases with the even growthof thickness and density,but its rising trend is tempered.The single number sound reduction indexes(RW)of specimen with thicknessof 20 cm and density of 0.51 g/cm3are 30.8 dB and 33 dB respectively,which demonstrates good sound insulation property forlightmass materials.     

不锈钢纤维多孔材料的吸声性能

采用不锈钢纤维为原料制备不同孔隙性能的纤维多孔材料，采用驻波管法检测该纤维多孔材料的空气声吸收系数，研究材料的孔隙度、纤维直径以及材料厚度等参数对吸声性能的影响，同时研究在材料背后设置空气层以及空气层厚度对材料吸声性能的影响关系。结果表明：实验采用的不锈钢纤维多孔材料具有较好的吸声性能，材料的孔隙度越高、厚度越大、纤维越细，材料的吸声性能越好，在材料背后设置空气层可显著改善其低频吸声性能，材料背后的空气层厚度越大，材料的低频吸声性能越好。