整板结构的古筝共鸣面板振动模态的研究

【目的】古筝的演奏效果除了与演奏者的技艺有关,与古筝本身的结构也有密不可分的联系。其中共鸣面板接收琴弦的振动并引起共振发声,是古筝发声过程中至关重要的一部分。本研究以整板结构古筝共鸣面板为研究对象,利用不同分析方法探讨其声学振动性能。【方法】采用ZSDASP信号采集分析软件对整板结构共鸣面板进行实验模态分析,得出各阶次共振频率及对应模态振型的特点和规律;并建立整板结构共鸣面板的三维模型,对其进行计算模态分析,验证计算模态分析应用于本研究的可行性。【结果】通过实验模态分析和计算模态分析均得出,随着振动阶次的升高,整板结构共鸣面板模态振型均趋于复杂,且对应的共振频率也逐渐增大;在实验模态结果中,(0,n)、(1,n)和(2,n)等阶次的共振频率较易识别;(0,n)阶对应的模态振型相对清晰易识别,但(1,n)、(2,n)中较低阶次对应的模态振型不明显;计算模态能够识别到的各阶频率所对应的振型为(1,n)和(2,n)阶,与实验模态结果相比缺少(0,n)阶,但计算模态分析得到的结果更具连续性,能够识别到(1,n)和(2,n)的所有阶次,而实验模态分析时个别阶次不够明显。【结论】将计算模态求解结果与实验模态结果进行对比分析得出,计算模态分析应用于整板结构古筝共鸣面板的振动模态研究具有一定的可行性。

锚定式整板支挡结构的试验研究

本文阐明了锚定式整板支挡结构的设计与施工,分析比较了墙面板内力计算方法,对土压力的分布图式也进行了探讨,并与实测结果进行了对比。由于荷载分布比较复杂,使得整体结构的内力分布也复杂化,故适当提高板的安全系数是有必要的。

A Study on the Effect of Welding Sequence in Fabrication of Large Stiffened Plate Panels

Welding sequence has a significant effect on distortion pattern of large orthogonally stiffened panels normally used in ships and offshore structures. These deformations adversely affect the subsequent fitup and alignment of the adjacent panels. It may also result in loss of structural integrity. These panels primarily suffer from angular and buckling distortions. The extent of distortion depends on several parameters such as welding speed, plate thickness, welding current, voltage, restraints applied to the job while welding, thermal history as well as sequence of welding. Numerical modeling of welding and experimental validation of the FE model has been carried out for estimation of thermal history and resulting distortions. In the present work an FE model has been developed for studying the effect of welding sequence on the distortion pattern and its magnitude in fabrication of orthogonally stiffened plate panels.