引线键合系统键合工具振动特性研究

研究微电子封装超声引线键合系统键合工具的动态特性和摩擦行为,运用有限单元法建立了键合工具的动态接触模型,初步掌握微电子超声键合系统键合机理。通过对键合工具施加不同的加载频率和正压力的计算结果进行对比,定性地给出了键合过程中加载频率和正压力的变化对键合工具动态响应和摩擦应力的影响.研究结果表明:键合工具的加载频率偏离固有频率,键合工具针尖部分的幅值响应将迅速减小,同时摩擦应力的均值也相对减小;正压力增大,响应幅值将会相应减小;正压力增大到一定值时,幅值响应将会波动比较大,如果要得到适合的键合点尺寸的要求,同时保证键合质量,就必须选择合适的加载频率和正压力。     

半导体器件内引线键合强度的检测与分析

文章介绍了对半导体器件内引线拉力即键合强度的实际检测方法,并通过失效分析和具体数据计算,进一步说明了键合强度与管壳内部尺寸和引线材料等参数的关系,并指出了准确检测键合强度时应注意的事项。     

基于流固耦合的导叶式离心泵强度分析

运用顺序耦合和双向流固耦合方法对导叶式离心泵进行了强度分析。通过顺序流固耦合方法,对叶轮进行了静应力强度分析,并与双向流固耦合方法得到的结果进行了比较。同时,对双向流固耦合结果中最大等效应力节点A和最大变形区域的节点B在叶轮旋转一周过程中的等效应力变化的时域图以及频域图进行了分析。结果表明,最大等效应力出现在叶轮前盖板、叶片背面和叶轮出口边的交界处（节点A）;叶片进口边中部以及与前后盖板的交界处和叶片出口与后盖板的交界处这些地方有应力集中,可能发生强度破坏。后盖板出口处且正好在流道中部位置变形最大（节点B）,可能发生刚度破坏。对于静力学分析,顺序耦合与双向耦合的结果基本一致。节点A的变形量小于节点B,但交变应力的幅值却远大于节点B。疲劳裂纹的扩展速度主要取决于交变应力幅值的大小,因此,在节点A处更易发生疲劳破坏。计算结果对导叶式离心泵叶轮结构优化设计提供了有效依据。     

基于快速独立分量分析的模态振型识别方法研究

摘要：快速、准确地识别出结构的模态参数,特别是结构的振型是结构损伤精确识别与健康监测的重要前提。大多的模态参数识别时域方法都是从曲线拟合的角度或解算特征值的过程来实现。振型向量通过求解各阶模态的留数获得,这些方法依赖于模态频率与模态阻尼的识别。本文提出一种模态振型的直接提取方法,该方法基于快速独立分量分析技术,以模态响应之间的独立性构造目标函数,通过优化目标函数寻求振型向量的最优解,直接从结构自由响应或脉冲响应的数据矩阵中提取结构的振型向量。三自由度数值算例表明该方法有效,具有很高的识别精度且对测量噪声具有很好的鲁棒性。     

基于两被联件振动信号概率密度和PCA的螺栓松动识别方法研究

螺栓松动是一种常见且具有潜在危害的机械故障。考虑到螺栓松动会导致被联接件结合部动力参数发生变化,提出了一种基于两被联接件振动信号的松动识别方法。所提方法首先计算两信号的概率密度,并对概率密度曲线进行网格化处理生成概率矩阵,继而对概率矩阵进行主元分析(PCA),在合并两路信号经主元分析后所得投影矩阵之后,再次进行主元分析和投影。设计了两种识别方式,方式1首先按上述过程进行已知样本训练以得到各松动状态投影点,识别时根据所得投影点与各状态投影点间的欧式距离进行判断;方式2使用螺栓紧固状态时所得样本数据和现场实测数据直接按上述过程进行计算,并根据PCA特性设计了松动判别条件。试验验证表明所提方法能够准确区分不同松动状态,且识别方式2操作简便,无需故障样本,易于实际应用。     

基于广义形态分量分析的降噪技术研究

针对强噪声环境中有用信号提取的难题,提出了基于广义形态分量分析的降噪方法。通过引入虚拟观测信号,将一维观测信号扩展为多维虚拟观测信号,再通过广义形态分量分析,实现观测信号的盲源分离,从而达到降噪的目的。通过仿真信号和齿轮磨损故障振动实验信号的研究结果表明：广义形态分量分析技术能有效分离强背景噪声中的微弱信号,有效提取故障特征,其降噪性能优于传统的独立分量分析。     

基于模拟加载系统油压信号的自动测试与识别技术研究

在液压系统模拟加载与自动测试、识别过程中,工作装置油压波动信号是一种典型的非平稳信号。针对其影响因素多、不具备明显频域特征以及任何单一特征参量都无法对信号进行准确识别的难题,提出了对信号先进行状态分割,在分割基础上计算不同工作状态下的特征参量,并进行基于主成分分析(PCA)的特征提取方法,最后采用最小二乘支持向量机(LSSVM)构建多分类器,实现对工作装置6种不同工作状态的准确识别。实验结果验证了该方法的有效性,为同类液压系统的信号特征分析及模式识别提供了参考。     

基于主分量分析的声信号特征提取及识别研究

主分量分析(PCA)是统计学中分析数据的一种有效方法。研究了基于这种算法对四种战场目标的声信号进行特征提取,获得了低维的特征类器对声目标进行分类,分类结果准确率较高,均获得满意的实验效果     

基于改进形态分量分析的齿轮箱轴承多故障诊断研究

形态分量分析是一种基于信号形态多样性和信号稀疏表示的信号和图像处理方法,其主要目标是根据信号组成成分的形态差异性,选择合适的字典来分离信号。针对传统形态分量分析的字典选择和阈值选择的缺陷,提出了基于自适应字典选择和TH-MOM (Hard Threshold-MOM)的阈值更新策略,通过仿真信号和齿轮箱轴承多故障振动实验信号的研究结果表明：该方法不仅能将形态各异的多分量信号进行有效分离,提高了信噪比,而且提高了从强噪声环境中提取瞬态冲击特征的能力,能有效地识别轴承的故障类型和部位。     

基于共振峰的超声空化声发射信号分析

摘 要：为了简单有效地提取超声空化时频信息而估计空化强度,提出了应用基于全极点线性预测编码模型的共振峰分析方法进行分析,并使用其分析了19kHz超声作用下的空化场的声发射信号。将共振峰分析结果与常用的频谱分析和短时傅利叶分析结果进行了对比,发现共振峰分析方法更能从超声空化声发射信号的中提取出简单但关键的时频信息来。采用共振峰方法的分析结果表明,可以利用空化声发射的共振峰参数如基频频率和相对高频共振峰的幅值来分别反映超声空化的非线性振荡和瞬态空化,进而估计超声空化的强度。     

Interlaminar shear strength evaluation of curved composite samples

To assess the bonding quality between the different layers of composite rings fabricated by filament winding it is necessary to choose a useful shear test. A method for measuring the shear strength of thin curved samples is proposed herein. Stress distribution within the probe is calculated and evaluated by finite element method.     

高强度Fe-Ni膨胀合金丝材时效工艺研究

采用性能测试和显微组织分析手段，探讨了高强度低膨胀Fe—Ni合金丝材时效处理对合金膨胀系数及强度的影响规律。试验结果表明，采用较高温度时效（475℃），能够使碳化物能够呈弥散状析出，将有利于合金膨胀系数的控制，及合金强度的提高；而较低的时效温度（425℃）下，碳化物呈不均匀状析出，合金强化效果不明显，同时不利于膨胀系数的控制。     

HJ混凝土界面处理剂剪切强度的试验研究

为了提高混凝土界面处理剂的剪切强度，得到良好的剪切力学性能，文章研究了不同聚合物种类、掺量和不同灰砂比对界面处理剂剪切强度的影响，并分析了各自的作用机理。试验结果表明：不同聚合物种类具有不同的最佳掺量，可使得界面处理剂的剪切强度达到最高。     

Investigation of explosive welding parameters and their effects on microhardness and shear strength

The aim of this study was to investigate the strength of explosive welded metals with the same chemical compositions. Different welding interfaces (straight, wavy and continuous solidified-melted) were used with changing explosive welding parameters [stand-off distance (s), explosive loading (R) and anvils]. Joined metals were investigated under heat-treated and untreated conditions. Results on the microstructure, microhardness, tensile shear strength and bending tests are reported. According to the experimental results, the effect of the anvil on the explosive welding process was only the joining or not-joining performance. It was shown that the bonding interface changed from a straight to a wavy structure when the explosive loading and stand-off distance were increased. For wavy interfaces, when the explosive loading was increased the wavy length and amplitude increased. Results of tensile shear and bending tests showed that heat-treated specimens have more strength than untreated samples. According to tensile shear test results, straight and wavy interfaces had similar strength. In addition, in bending tests of untreated specimens it was shown that the bending zone had some cracks.     

爆炸复合接头剪切强度测试方法研究

参照正交各向异性层压复合板层间剪切强度的测试方法，提出了用于测试爆炸复合接头复合界面剪切强度的3种方法；并建立三雏有限元模型，分别对3种测试方法进行模拟；最后分别对3种方法进行了测试试验．结果表明，3种试验方法均能有效测试爆炸复合接头的剪切强度，其中对称试件双切口拉伸法最适合实际应用．     

树脂基体对导电胶拉伸剪切强度影响分析

以不同环氧官能团数量的环氧树脂和不同添加量的固化剂为原料制备了导电胶,通过红外光谱、扫描电子显微镜等手段测试其结构和性能。结果表明,拉伸剪切强度随环氧官能团数目的增加而降低,其中双官能团的环氧树脂DER331所对应的树脂基体和导电胶的拉伸剪切强度最大,树脂基体为31MPa,导电胶为9MPa;随固化剂添加量的增加而增加,当环氧树脂和固化剂质量比为25∶7时,树脂基体为32MPa,导电胶为10MPa;与树脂基体的固化收缩率呈反比关系。     

Effect of openings on the behaviour and strength of R/C beams in shear

The effects of introducing a transverse opening on the behaviour and strength of reinforced concrete beams under predominant shear are presented and discussed in this paper. On the basis of observed structural response, some guidelines are suggested to classify the opening as “large” or “small”. For small openings, two types of diagonal tension failure have been identified, and a method of design using the current codes of practice is proposed. The method is illustrated by a numerical example.     

Ab initio DFT study of ideal shear strength of polytypes of silicon carbide

Ab initio density functional calculations are performed to investigate the ideal shear deformation of SiC polytypes (3C, 2H, 4H, and 6H). The deformation of the cubic and the hexagonal polytypes in small strain region can be well represented by the elastic properties of component Si₄C-tetrahedrons. The stacking pattern in the polytypes affects strain localization, which is correlated with the generalized stacking fault energy profile of each shuffle-set plane, and the ideal shear strength. Compressive hydrostatic stress decreases the ideal shear strength, which is in contrast with the behavior of metals. __________ Translated from Problemy Prochnosti, No. 1, pp. 8–13, January–February, 2008.     

Fatigue strength functions in shear loading of fabric conveyor belts

The fatigue behaviour of three types of fabric conveyor belt subjected to shear loading is studied. The fatigue phenomenon of belts is explained by the decrease of shear strength, which is determined as an ultimate angle initiating the lamination failure of the central rubber layers. Tests with precycling have shown that the permanent shear strength is diminished during precycling and can be modelled by power functions of the number of cycles, called fatigue strength functions (FSFs). Two main hypotheses of FSFs' existence and state equivalence are tested. A comparison between the proposed method and a linear damage accumulation rule is also carried out for two-level loading.     

Experimental investigation on the debonding strength in shape memory alloy wire reinforced polymers

The interfacial shear strength between the shape memory alloy (SMA) wire and epoxy matrix was evaluated experimentally using a single wire pull-out test. Moreover, the effect of pre-strain in SMA wires on the interfacial behavior was studied by pre-straining the SMA wires to 2% and 4% pre-strains. Experiments were conducted in both martensite and austenite phases of SMA. Results showed that pre-straining SMA wire in the martensite phase caused enhancement in interfacial shear strength due to recovery force generation. Further, 9.7% and 33% improvements in the interfacial shear strength were achieved at 2% and 4% of SMA pre-strain, respectively. However, the enhancement of interface behavior did not occur, when the SMA wires were subjected to pre-strain in the austenite phase.