用于微电子封装的高频压电超声换能器模态优化设计

研究了高频压电超声换能器的优化设计方法,基于四端网络方法和有限元分析软件ANSYS参数化建模,通过不断调节结构参数的大小对换能器进行优化,使工作频率在满足设计要求的前提下,实现了工作频率与其他非工作频率的分离。通过阻抗分析仪和多普勒激光测振仪对换能器进行测试,实验结果表明,该换能器工作频率为110.161 kHz,工作频率附近不存在非纵振模态和其它寄生的振动形式。

子波分解重构与EEMD在火山机构地震精细刻画中的应用研究

火山岩体有利相带的分布受火山机构主体控制,也是油气高产区和有利储层发育区,因此刻画火山机构很有意义。由于火山岩的形态多样,非均质强,地震资料一般信噪比低,反射能量弱,反射波连续性差,直接使用地震资料进行火山机构刻画存在着相当大的难度。集总经验模态分解(EEMD)和子波分解重构是当前研究较热的两种技术算法,其主要特点都是突出有效信号。这里尝试使用这两种方法分别对火山机构的地震数据进行分解研究,两种方法虽然本质不一,但效果类似,为火山机构的刻画提供了较为可靠的依据。

Modal analysis on transverse vibration of axially moving roller chain coupled with lumped mass

The modal characteristics of the transverse vibration of an axially moving roller chain coupled with lumped mass were analyzed.The chain system was modeled by using the multi-body dynamics theory and the governing equations were derived by means of Lagrange's equations.The effects of the parameters,such as the axially moving velocity of the chain,the tension force,the weight of lumped mass and its time-variable assign position in chain span,on the modal characteristics of transverse vibration for roller chain were investigated.The numerical examples were given.It is found that the natural frequencies and the corresponding mode shapes of the transverse vibration for roller chain coupled with lumped mass change significantly when the variations of above parameters are considered.With the movement of the chain strand,the natural frequencies present a fluctuating phenomenon,which is different from the uniform chain.The higher the order of mode is,the greater the fluctuating magnitude and frequency are.

Mechanism of zonal disintegration phenomenon in enclosing rock mass around deep tunnels

In order to study the mechanism of the zonal disintegration phenomenon(ZDP),both experimental and theoretical investigations were carried out.Firstly,based on the similarity law,gypsum was chosen as equivalent material to simulate the deep rock mass,the excavation of deep tunnel was modeled by drilling a hole in the gypsum models,two circular cracked zones were measured in the model,and ZDP in the enclosing rock mass around deep tunnel was simulated in 3D gypsum model tests.Secondly, based on the elasto-plastic analysis of the stressed-strained state of the surrounding rock mass with the improved Hoek-Brown strength criterion and the bilinear constitutive model,the maximum stress zone occurred in vicinity of the elastic-plastic interface due to the excavation of the deep tunnel,rock material in maximum stress zone is in the approximate uniaxial loading state owing to the larger tangential force and smaller radial force,the mechanism of ZDP was explained,which lay in the creep instability failure of rock mass due to the development of plastic zone and transfer of the maximum stress zone within the rock mass.Thirdly,the analytical critical depth for the occurrence of ZDP was obtained,which depended on the mechanical indices and stress concentration coefficient of rock mass.

部分水下弹性支承等截面梁柱的自由振动分析

研究浸入流体中自由端具有集中质量块的等截面弹性支承悬臂梁的横向自由振动。考虑由集中质量块引起的轴向力作用,建立了支承处弹性水平位移约束和转动约束耦合情形下悬臂梁横向自由振动数学模型。由于集中质量块的惯性力和惯性距,此模型的边界条件与固有频率相关。推导了梁自由振动的频率方程和振动模态的广义正交性条件。数值研究了水深、集中质量块质量、转动惯量、质心距以及弹簧耦合刚度等参数对悬臂梁固有频率和正则模态的影响。