圆锥型压电换能器的动态设计与实验研究

对一种圆锥型夹心式压电换能器进行了动态设计与实验分析。利用有限元分析方法对换能器进行了动态设计,给出了该类压电换能器有限元建模方法,分析了换能器主要结构尺寸对振动模态、固有频率的影响。依据有限元分析结果,提出了一种基于数值分析的换能器优化设计方法,简化了设计过程。在数值分析的基础上,设计、研制了圆锥型夹心式压电换能器,并对压电换能器进行了性能测试。并将实验测试数据和有限元分析结果进行了对比,测试结果验证了数值分析与设计方法的合理性。     

Development of free vibration analysis algorithm for beam structures by combining Sylvester’s inertia theorem and transfer stiffness coefficient method

A new free vibration analysis method, which is called the Sylvester-transfer stiffness coefficient method (S-TSCM), is developed by combining Sylvester’s inertia theorem and the transfer stiffness coefficient method. In this paper, the free vibration analysis algorithm of a straight-line beam structure is formulated by S-TSCM. From the computation results of the free vibration analysis for the three types of beam structures, we confirm that S-TSCM is a very effective method. In particular, S-TSCM is superior to both the transfer stiffness coefficient method and the transfer matrix method in terms of computational accuracy and time. In the free vibration analysis for the beam structure with a large number of degrees-of-freedom, S-TSCM is superior to the finite element method in terms of computational time and storage.     

直齿轮系齿根裂纹损伤程度检测方法

为了实现直齿轮系裂纹损伤程度的检测,提出一种基于主成分分析(principal component analysis,简称PCA)及灰色理论相结合的方法。首先,建立直齿轮系动力学模型,通过仿真获得不同裂纹损伤程度下直齿轮系振动信号,基于现代信号分析方法(包括时域方法和频域方法),提取振动信号中齿轮损伤变化敏感的多个故障行为特征参数;其次,通过PCA方法与灰色关联分析算法对多维特征参数进行优化、降维;最后,用关联度表征裂纹损伤程度从而实现对直齿轮系裂纹故障的程度检测。由动力学模型的仿真数据的分析表明,运用笔者提出的PCA及灰色理论相结合的方法检测直齿轮系裂纹故障比直接对特征参数定阈值的检测方法关联度数值提高了16%,从而证明了该方法的有效性。     

小波包分析在图像消噪中的应用研究

小波包分析是在小波分析的理论基础上,可为信号提供更加精细的分析方法.因此根据图像特点、图像噪声特点,研究采用小波包分析对图像进行消噪处理的方法.实验表明,这种方法在图像消噪处理中是有效可行的.     

基于P方法的平板封头压力容器疲劳分析

压力容器的疲劳分析是压力容器设计、分析的重要环节。本文基于有限元分析的P方法对平板封头压力容器进行疲劳分析。通过与传统方法的对比,得出P方法更精确的结论,为压力容器的疲劳评定提供更可靠的依据。     

Nonintrusive frequency analysis for variable pairing on a distillation column

This paper describes a nonintrusive plant analysis technique for variable pairing that relies on power spectrum frequency analysis. The development of the method is described and guidelines for the implementation of the method are presented. Information gathered from the frequency analysis is used in variable pairing to ensure minimal impacts from unmeasured disturbances. Specifically, the nested epsilon decomposition method for variable pairing is used. This nonintrusive analysis method is implemented on a pilot plant distillation column. The results of the pilot plant test are used in the decoupling of a multiloop control system.     

幅值调制信号的双谱分析法

幅值调制现象是一种常见的机械故障现象.传统的分析方法有时域分析法和功率谱分析方法.这两种方法均具有对噪声敏感的缺点.本文在分析幅值调制信号模型和高阶统计量的基础上,提出了一种改进的双谱计算方法.理论及仿真分析结果表明,它对于幅值调制信号的分析,是颇为有效的.     

基于支持向量机的门式起重机主梁非概率可靠性分析

针对门式起重机主梁隐式极限状态函数的非概率可靠性分析,提出了一种基于支持向量机回归的主梁非概率可靠性分析方法。调试核函数,优化回归参数,使用训练后的支持向量机替代隐式极限状态函数。利用非概率集合理论中的区间分析法,引入尺寸比例因子,提出了基于支持向量机的起重机主梁非概率可靠性分析方法。最后用1个算例来验证本文方法,结果表明,该方法具有可行性、正确性和高精度的优点,并对其它工程结构的非概率可靠性分析具有一定的参考价值。     

VELOCITY ANALYSIS OF A PLANAR MECHANISM USING A METHOD FROM STATICS

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An efficient method to predict the heat transfer performance of a louver fin radiator in an automotive power system

A numerical method to efficiently predict heat transfer phenomena of a louver fin radiator was presented — multi-scale semimicroscopic heat exchange (SHE) method. This method consists of microscopic analysis and semimicroscopic analysis. To predict heat transfer characteristics of a louver fin element, the microscopic analysis employs modeling of the detailed geometry of a fin element. Numerical models for the heat transfer rate and flow friction derived from the microscopic analysis are then used for simulations of the full radiator model in semimicroscopic analysis. In the semimicroscopic analysis, conjugate heat transfer is analyzed for the domain with the radiator whose louver fin area is replaced by a porous media. The results with the proposed method show a good agreement with the experimental data. The proposed method can be used to predict flow and heat transfer characteristics of a realistic louver fin radiator with a reduced cost and sufficient accuracy.