用光纤干涉仪检测I形复合材料梁腹板/翼缘连接处的分层

介绍了一种在超声回弹波频谱分析基础上用光纤干涉仪来检测I形复合材料梁腹板/翼缘连接处分层的方法,利用超声发射器在I形梁中产生应力波,用表面粘贴的光纤干涉仪来接收应力波产生的输出信号,对此信号进行频谱分析可找到I形梁的分层位置。理论分析和实验都表明了此方法探测复合材料梁腹板/翼缘连接处分层的可行性。     

变电站自动化系统中规约转换的分层结构

为了适应变电站自动化系统中各种规约的通用转换,减少软件的改动,介绍了一种采用三层结构的设计思想,层间接口定义完整后,若操作系统更新换代或软件功能升级时只需更改替换相应层内的内容,而保持接口不变,不会影响到相邻层的实现。该方法具有较高的应用价值。     

IC Surface Corrosion Inspection by C-Mode Scanning Acoustic Microscopy

C-mode scanning acoustical microscopy, C-SAM, is widely used in plastic package evaluations and for failure analysis. It permits to detect subsurface delaminations, cracks and pores （air bubbles） for different microelectronics packages. In this study, abnormality was observed in C-SAM daily test, the images showed no delaminations but inhomogeneities on the IC surface. Corrosion was found by optical microscope and scanning electron microscope after decapsulation. It can be revealed as the acoustic impedance is different between corrosion and normal area. The presence of inhomogeneities and discontinuities along ultrasonic waves＇ propagation paths inside the matter causes modifications in the amplitude and polarity of ultrasonic waves. However, C-SAM＇s capability in detecting IC surface corrosion has not been presented. The capability will be illustrated and the inspection mechanism will be discussed in this paper.     

Theoretical modelling of laminated composite plates

Formulation of appropriate governing equations, simpler than the three-dimensional equations of elasticity yet capable of predicting, fairly accurately, all important response parameters such as stress and strain, is attempted in modelling a structural component. Several theoretical models are available in the literature for the analyses of plates. The emergence of fibre-reinforced plastics as an attractive form of structural construction, added a new complexity to the modelling considerations of laminates by requiring the estimation of the interlaminar stresses and strains. In this paper, modelling considerations of laminated composite plates are discussed. The classical laminated plate theory and higher-order shear deformation models are reviewed to bring out their interlaminar stress predictive capabilities, and some new modelling possibilities are indicated. This work has been supported by the Aeronautics Research and Development Board, Ministry of Defence, Government of India.     

Influence of Matrix Ductility and Fibre Architecture on the Repeated Impact Response of Glass-Fibre-Reinforced Laminated Composites

This paper describes the results of falling weight impact tests on glass-fibre-reinforced laminates. The test program consisted of (i) falling weight impact tests for the determination of the penetration energy and the influence of laminate construction on damage development and (ii) repeated falling weight impact tests for the determination of the impact fatigue lifetime and damage development under repeated impact conditions at sub-penetration energy levels. The objective of this work is to compare the impact behaviour of cross-ply laminates based on a brittle unsaturated polyester resin and a more ductile vinyl ester resin system and two types of glass reinforcement, i.e. woven- and multiaxial non-crimp fabric. The penetration energy of the various composite laminates appeared to be mainly influenced by the type of reinforcement, whereas damage development during (repeated) impact is strongly influenced by both fibre architecture and resin. No significant effect of the different material parameters investigated on the number of impacts to penetration (impact fatigue lifetime) is observed. Especially when the repeated impact energy is normalised with respect to the penetration energy, all laminates showed similar behaviour.     

浅议半孤岛工作面掘进期的矿压监测与分析

济二煤矿43下04(北)工作面为一典型的半孤岛工作面,通过对该工作面特点的分析,制定了以顶板离层监测为主,支护质量监测与围岩表面位移监测为辅的监测方案,确定了离层变化较大的地段,提出了加强支护的措施,为今后工作面回采提供了必需的参考资料,对类似工作面的矿压观测积累了经验.     

Stress analysis of plastic IC package containing various interface delaminations using the boundary element method

The purpose of this paper is to carry out stress calculation of the integrated circuit (IC) plastic package under the remote loading or the pressure acting on the delamination surfaces by the boundary element method (BEM). Based on symmetrical property of the problem geometry and the loading, the corresponding fundamental solution can be obtained to further reduce the number of the boundary elements used in the discretization of the problems. Near the interface delamination tips, singular boundary elements are used to accurately obtain the stress intensity factors. For the pre-assumed delamination spaces, the corresponding stress distributions in each domain can be obtained so that the effect of the interface delamination on the stresses can be observed. In order to assure the rightness of the developed code, some special problems in which the analytical solutions are available are studied. The results show that the developed code can produce numerical results with high accuracy.     

Thermodynamics of a Stable Blister Delamination at Elevated Temperature

A new blister test using thermal expansion of an internal working gas trapped at a dissimilar interface between a thin polymer coating and a rigid adherend is developed to measure the adhesive strength at elevated temperature. The blister dimensions are measured by a thermomechanical analyser (TMA) and an optical microscope as a function of temperature. The thermodynamics is presented based on both linear elastic fracture mechanics and the ideal gas law.     

Delamination dynamics in through-thickness reinforced laminates with application to DCB specimen

Bridged crack models using beam theory formulations have proved to be effective in modeling quasi-static delamination crack growth under large scale bridging conditions in through-thickness reinforced structures. In this paper, beam theory is used to study dynamic mode I crack propagation in through-thickness reinforced laminar structures. In particular, steady state dynamic crack growth for a Double Cantilever Beam (DCB) loaded with a flying wedge is examined. The steady state crack propagation characteristics are mapped out in terms of controllable loading and material parameters including the crack velocity and the properties of the through-thickness reinforcement. For small crack velocities, the through-thickness reinforcement considerably enhances the delamination resistance of the structure. At higher velocities, the kinetic energy term dominates the overall energetics and the relative effect of the reinforcement on the delamination resistance is insignificant. The model suggests a simple fracture test for estimating the properties of the through-thickness reinforcement under dynamic loading conditions.