Accelerated life testing of nano ceramic capacitors and capacitor test boards using non-parametric method

Engineers are searching for a reliable method to determine the time-to-failure (TTF) data of the electronic systems as cheaper as possible. Reliability plays a vital role in electronic devices marketing & sales, product quality, etc. Accelerated Life Test (ALT) and Highly Accelerated Life Testing (HALT) are the latest methodology in the field of life testing of engineering systems. The ALT can be conducted at higher stress level to generate more failure data within short duration of time. The parametric method and non-parametric method are used to convert the accelerated test condition to actual condition. In this paper, the most widely used C0G and X7R nano ceramic capacitor is selected to generate the time-to failure data at accelerated condition and non-parametric method is used to convert the accelerated condition data into actual condition.     

测试不可靠条件下的诊断策略优化方法

提出了一种测试结果不可靠条件下的诊断策略优化生成方法.首先将描述测试可靠性的参数(检测概率和虚警概率)转换为误诊代价,将其与基于霍夫曼编码的测试费用评估函数相结合,构建了一种既考虑测试费用又考虑诊断精度的启发式评估函数,然后基于该启发式评估函数提出了一种不确定AO*算法.为了有效评估诊断策略的诊断精度,提出了一种测试性参挝数预计方法.最后应用案例验证了本方法,测试性预计结果表明本方法实现了诊断精度和测试费用的权衡.     

一种压电陶瓷叠堆执行器刚度测量方法研究

分析了压电陶瓷叠堆执行器(piezoelectric ceramic stack actuator,PCSA)的刚度及其与位移输出的关系。在此基础上,提出了一种通过分别测量PCSA在相同驱动电压下空载时和在给定刚度的弹性框架预紧时的位移输出量,并根据测得的位移输出量解算PCSA刚度的刚度测量方法,建立了相应的PCSA的刚度测量系统原理。通过分析和建立弹性框架的伪刚体模型、刚度方程和应力方程,以达到对弹性框架的刚度特性进行准确设计的目的。利用有限元仿真和实验对提出的PCSA刚度测量方法和建立的系统特性进行了验证和测试。仿真和实验结果表明,根据建立的刚度方程能够对弹性框架的刚度进行准确估计,提出的PCSA刚度测量方法能够实现PCSA刚度的测量。     

Dynamic analysis of multilayer ceramic capacitor for vibration reduction of printed circuit board

Owing to their high permittivity and volumetric efficiency, the demand for multilayer ceramic capacitors (MLCCs) has increased rapidly in recent times. Because of the electromechanical characteristics of BaTiO₃, MLCC vibrates, resulting in printed circuit boards (PCBs) generating acoustic noise. To construct an accurate finite element model of an MLCC, piezoelectric and electrostrictive coefficients were extracted and verified through experiments. The top cover layer thickness and bandwidth were chosen as design parameters to reduce the vibration of PCB. The simulation results indicate that the bandwidth and top cover layer thickness are highly related to the vibration in the top direction and the rotational moment generated from the head surface, respectively. Based on the analysis results, a novel MLCC was suggested and it exhibited reduced vibrational characteristics of PCB about 75 % compared with that of commercial MLCCs.

     

Analysis for deformation behavior of multilayer ceramic capacitor based on multiscale homogenization approach

Given the rapid improvements in the miniaturization, functionality, and efficiency of electronic products in recent years, the dielectric layers and electrodes of multilayer ceramic capacitors have become thinner, with the number of stacked layers also increasing. As a result, the deformation defects induced during manufacturing of the capacitors have increased. In this study, the deformation behavior of a multilayer ceramic capacitor composed of ceramic dielectric layers and Ni electrode layers during the compression process was analyzed numerically using the FEM. To analyze the deformation behavior of the capacitor, which consisted of several hundred laminated ceramic and Ni layers, in the plane direction, the material properties were represented by equivalent material properties based on the multiscale homogenization approach. Then, the deformation of the capacitor in the plane direction owing to the residual stress arising during the compression process was analyzed based on the calculated equivalent material properties. Finally, the possibility of a product defect with the size of the ceramic dielectric and electrode layers during the cutting process was predicted.     

Analytical method for prediction of weld line movement during stretch forming of tailor-welded blanks

Tailor-welded blanks (TWBs) consisted of metal sheets with different characteristics welded into a single flat blank prior to pressing in order to achieve the optimal material arrangement and weight reduction for cars, and to increase machine flexibility and process efficiency. The movement of weld line in TWBs is always a challenging issue during manufacturing process. In this research, a new analytical method for prediction of weld line movement in TWBs is developed. A comparison between the analytical results with those obtained from finite element simulation as well as the experimental data indicates good compatibility between the predictions of the developed method in the case of both weld line movement and dome height of TWBs. Furthermore, the developed analytical method can appropriately consider the effect of thickness ratio on both weld line movement and dome height. It was observed that weld line movement increases as thickness ratio enhances.     

Damage state assessment method for remanufacturing blanks based on magnetic and surface texture feature fusion

In order to improve the accuracy and efficiency of damage assessment, a novel method to evaluate the damage state for remanufacturing blanks based on the magnetic and surface texture feature fusion was developed. Through modeling of the magnetic and surface texture features, sample entropy parameters from the magnetic intensity and its gradients were extracted, and energy, entropy, contrast, and correlation parameters from surface texture were obtained. The two-layered feature fusion model comprised of the data layer and the index layer was established. In the data layer, parameters of the magnetic and surface texture features and their nonlinear mapping relationships with damage were obtained. In the index layer, the information fusion between the magnetic and surface texture features was carried out by Dempster-Shafer (D-S) evidence theory. Finally, fatigue test samples were selected to verify the feasibility of the proposed method. Results show that the method can be used to determine the damage states of the remanufacturing blanks, which provides theoretical and technical decision support for remanufacturability of the components.     

一种电容非介入式压力测量方法研究

非介入测量对液压系统的故障诊断与检测具有关键作用,研究了液压系统的电容非介入式压力测量的可行性,基于函数型连接神经网络建立了电容式压力测量的电容与压力的数学模型,在此基础上,设计了相应的电容非介入式压力测量实验平台,结合实验,得出实际液压系统中电容和压力确切的数学关系,也定性分析了液压油介电常数和温度的关系.仿真和实验结果表明,变介电常数电容法在液压管路压力非介入式测量中完全可行,为小管径液压系统的在线压力测量提供一种新的方法.     

A KPU-200 movable capacitor installation

A movable electrophysical capacitor installation with a 250-kJ maximum bank energy, which generates intense neutron pulses, is described. A current pulse generator with a capacitive energy storage forms the basis of the installation. When the initial voltage at the capacitor bank is up to 35 kV, the installation ensures a flow of current pulses with amplitudes of up to 2 MA in a gas-discharge plasma-focus chamber, which is filled with an equal-component deuterium-tritium (DT) mixture. Under these conditions, the chamber is capable of repeatedly generating single fast-neutron pulses with an energy of 14.1 MeV, a duration of ～70 ns, and an integral yield over 1013 neutrons/pulse.     

Nondestructive testing of the quality of blanks for the fabrication of hot-rolled strips using the acoustic-emission method

A method for predicting the quality of hot-rolled strips based on the results of recording acoustic-emission (AE) signals is proposed. Considering the development of flaws in a slab under the effect of technological loads during rolling as a process of the loss of the integrity of the slab material, the AE signals recorded in the course of diagnostic loading of experimental specimens are interpreted from the standpoint of a micromechanical model and the developed methodology for nondestructive testing of the strength of a material and quality estimation. The most informative diagnostic parameters and diagnostic features of the method are determined by comparing the results of the interpretation with the defect level of the obtained strip.     

压缩气体高压电容器电压系数测量方法

综述了压缩气体高压电容器电压系数测量的国内外研究状况。介绍了基于高压电容器电极结构、参数(如弹性模量)、安装精度等参数的测量估计其电压系数的间接测量法,分析了直接比较法、直流偏压法、双频法、倾斜法、冲击法等设计高压测试电路的方法,在实际工作电压下测试电压系数的直接测量法,其中重点解析了倾斜法。     

Upsetting with wall thinning for thick-walled anisotropic cylindrical blanks

The stress and strain state of the blank, the applied force, and the limiting possible shape change are investigated in upsetting with wall thinning for thick-walled anisotropic cylindrical blanks.     

Molybdenum-coated blanks for reliable frictional disks in oil-filled transmissions

Molybdenum-coated blanks for frictional disks in vehicle transmissions permit improvement in their performance. The coating is applied by plasma spraying.     

A voltage stabilizer on a storage capacitor

A voltage stabilizer on a storage capacitor is intended for converting constant unstabilized voltages into pulsed voltages with stabilized amplitudes in power supply circuits for lasers. The principle of operation of this stabilizer is based on preliminarily charging of the storage capacitor to a voltage intended for compensating for an alternating component of the input voltage. The proposed technical decision significantly increases the laser emission stability. A voltage U _out = 1000 ± 1 V was obtained across the storage capacior, and the stabilization coefficient was ～100.     

Evolutionary optimisation of hedging points for unreliable manufacturing systems

The production rates of manufacturing systems are notoriously difficult to control, since such systems are dynamic, uncertain and non-linear. However, the introduction of hedging-point policies for such systems has led to much progress in optimal production control. But the theoretical results so far obtained for such hedging-point policies are still far from complete, since the optimal hedging points (i.e., the optimal inventory levels) are analytically available only for simple systems and under restrictive assumptions. In this paper, an evolutionary stochastic optimisation procedure is proposed to estimate the short-run optimal hedging points for failure-prone manufacturing systems under crisp-logic control. This methodology is illustrated by examples and is validated by comparing the evolutionary results with the available analytical long-run solutions. The proposed evolutionary methodology is also shown to be capable of generating optimal hedging points for unreliable systems producing multiple products with different priorities. In addition, the relative merits of genetic algorithms, evolution strategies and adaptive evolution strategies in hedging-point optimisation are compared.     

矩形毛坯三块排样方式及其算法

采用线性规划和动态规划解决矩形毛坯排样问题。采用下料工艺简单的三块排样方式,用两条成T形的剪切线将板材分成三个矩形区域,每个区域中包含一个由同尺寸毛坯组成的规范块。实验计算表明,所述算法可解决大规模矩形套裁排样问题,能够有效提高材料利用率和简化下料工艺。     

A zone-layered trimming method for ceramic core of aero-engine blade based on an advanced reconfigurable laser processing system

Ceramic structural parts are one of the most widely utilized structural parts in the industry. However, they usually contain defects following the pressing process, such as burrs. Therefore, additional trimming is usually required, despite the deformation challenges and difficulty in positioning. This paper proposes an ultrafast laser processing system for trimming complex ceramic structural parts. Opto-electromechanical cooperative control software is developed to control the laser processing system. The trimming problem of the ceramic cores used in aero engines is studied. The regional registration method is introduced based on the iterative closest point algorithm to register the path extracted from the computer-aided design model with the deformed ceramic core. A zonal and layering processing method for three-dimensional contours on complex surfaces is proposed to generate the working data of high-speed scanning galvanometer and the computer numerical control machine tool, respectively. The results show that the laser system and the method proposed in this paper are suitable for trimming complex non-datum parts such as ceramic cores. Compared with the results of manual trimming, the method proposed in this paper has higher accuracy, efficiency, and yield. The method mentioned above has been used in practical application with satisfactory results.     

A setup for measuring the refractive index of a plane-parallel ceramic plate using the optical beam shift method

A setup for measuring the refractive indices of transparent solid samples of optical ceramics using shifts of a beam by a plane-parallel plate in a wavelength range of 400–1200 nm was developed. The minimum cross-sectional sizes of the investigated objects are 5–12 mm, and their thicknesses are 0.3–1.0 mm. A standard sample and a precise system for forming and recording optical signals equipped with a stepping motor with a step discreteness of <1 μm were used to improve the measurement accuracy of the refractive index. The cross-sectional size of the measuring beam is ?1 mm. The accuracy in determining the refractive index is ±0.004.