两种国际通用乒乓球拍底板木材的固有频率及其影响因素

以白梧桐、红桧两种国际通用乒乓板木材为试验材料,采用悬臂板一端固定的横向振动方法,研究木材试件的含水率、纹理角、树种、比模量与固有频率的关系。结果表明:木材试件固有频率随含水率的增加而降低,当含水率达到20%以上时,两种树种固有频率值的变化趋于缓和。在含水率变化范围内,白梧桐试件固有频率值在66～56 Hz之间变化,红桧试件固有频率值在76～60 Hz之间变化。白梧桐、红桧两种树种试件的固有频率均值分别为56.32和69.01 Hz,但白梧桐试件固有频率的稳定性高于红桧,且径切板试件的固有频率大于弦切板的固有频率。在相同尺寸、测试方法和条件下,两种树种试件的固有频率值与比模量的关系符合薄板振动理论推导出的固有频率解的形式; 红桧试件的比模量大于白梧桐试件的比模量。通过计算材料的弹性模量和密度,得出相应的比模量,从而可以判断出此材料的固有频率值。
As international common wood species for table tennis racket blade, Ayous and Cypress were chosen as the research objects. Based on acoustic and vibration theory of wood, the relationship among the natural frequency and moisture content, grain direction, wood species and specific modulus were studied by adopting transverse vibration method with cantilever fixed at one end. The results showed that the natural frequency of wood specimens decreased with the increased moisture content. With the moisture content rose up to more than twenty percent, the change of natural frequencies appeared to be moderating. Within the change range of moisture content, the natural frequency value of Ayous and Cypress ranged from 66 to 56 Hz,76 to 60 Hz respectively. The average natural frequencies of Ayous and Cypress were 56.32 and 69.01 Hz respectively, but the natural frequency stableness of Ayous is greater than that of Cypress. The natural frequency of the quarter-Asawn test specimens was greater than that of flat-sawn. Under the same dimension, testing method and condition, the relationship between the natural frequency and specific modulus matched the form of the natural frequency’s solution which could be deduced from the theory of plate vibration. The Cypress’s specific modulus was greater than that of Ayous. The natural frequency of material could be estimated by calculating the modulus of elasticity, density and specific modulus