足尺中密度纤维板振动模态分析
Analysis of the Vibration Modal of the Full-sized Medium Density Fiberboard

为了利用振动法无损检测足尺中密度纤维板整板的弹性模量，对足尺中密度纤维板的振动特性进行研究。为了求解足尺中密度纤维板在自由振动下的模态参数，对3种厚度的足尺中密度纤维板，分别进行计算模态分析和试验模态分析，并对其自由振动形式下，前3阶模态振型和频率进行对比和分析。结果表明：1)3种不同厚度的足尺中密度纤维板表现出了相同的振动模态形式：第一阶、第二阶振型都是沿着长度方向的弯曲振动，第三阶振型则是沿着宽度方向的弯曲振动；2)计算模态分析和试验模态分析所得到的频率结果有一定的差距，其中，第一阶模态计算频率稍小于试验频率，第二和第三阶模态计算频率均大于试验频率；但计算模态频率与试验模态频率间有很好的相关性，决定系数达到了0.981 6。
In order to nondestructively detect elastic modulus of the whole full-sized medium density fiberboard by using vibration method, this paper studied the vibration characteristics of the fiberboard. To solve modal parameters of the fiberboard in the condition of free vibration, the calculation modal analysis and experimental modal analysis of the full-sized medium density fiberboards with three kinds of thickness were conducted, respectively. The first three order modal vibration mode and frequency had also been compared and analyzed. The results showed as follows:1) the full-sized medium density fiberboards with three different thickness showed the same vibration modal form:both of the first and second order vibration modes had the bending vibration along the length direction, while the third order vibration mode had the bending vibration along the width direction; 2) the results of the frequency through calculated modal analysis and experimental modal analysis had a certain difference in frequency:the first order modal calculated frequency was slightly lower than the test frequency, and the second and third order modal calculation frequency was higher than their test frequency.There was a good correlation existing between calculated modal frequency and test modal frequency with the decision coefficient of 0.981 6