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This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew (PFGS) plates. The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate. A nonlinear finite element (FE) formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory (FSDT) in conjunction with von Karman’s nonlinear strain displacement relations. The governing equations of the PFGS plate are derived using the principle of virtual work. The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations. The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters. The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail. 相似文献
153.
Ian G.Crouch 《防务技术》2021,17(6):1887-1894
The ballistic performance, and behaviour, of an armour system is governed by two major sets of variables, geometrical and material. Of these, the consistency of performance, especially against small arms ammunition, will depend upon the consistency of the properties of the constituent materials. In a body armour system for example, fibre diameter, areal density of woven fabric, and bulk density of ceramic are examples of critical parameters and monitoring such parameters will form the backbone of associated quality control procedures. What is often overlooked, because it can fall into the User’s domain, are the interfaces that exist between the various products; the carrier, the Soft Armour Insert (SAI), and the one or two hard armour plates (HAP1 and HAP2). This is especially true if the various products are sourced from different suppliers.There are between 30 and 150 individual layers within a typical body armour system, and each of the interfaces between each of those layers will, in some way or another, contribute to the ballistic performance of the system. For example, consider the following interfaces/interlayers: (i) the frictional, sliding, inter-ply surfaces within a soft armour pack, and also between the pack and the carrier, (ii) the air-gaps that may develop within the soft armour pack, (iii) the interconnecting space between the soft armour pack and the hard armour plate, (iv) the nature of the interfaces between adjacent plies of a multiplied backing laminate, even in a highly compressed Ultra High Molecular Weight Polyethylene (UHMWPE) variant, (v) the interlayer between the ceramic and its substrate, within a HAP, and (vi) the geometrical fit between two hard armour plates within a stacked body armour system. This paper will provide a User-friendly overview of all such interfaces and provide unique guidance as to their criticality and influence. 相似文献
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In this research, mechanical stress, static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented. The kinematic relations are developed based on higherorder sinusoidal shear deformation theory. Thickness stretching formulation is accounted for more accurate analysis. The total transverse deflection is divided into bending, shear and thickness stretching parts in which the third term is responsible for change of deflection along the thicknes... 相似文献
156.
In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the fin... 相似文献
157.
Electrospinning is a simple technique used to fabricate polymeric nano-fibrous membranes. These nano-fibers have found a wide range of valuable applications in the biomedical field. However, it has not been utilized with solid high explosives yet. Herein, the electrospinning technique has been used to fabricate polystyrene(PS)/1,3,5-trinitro-1,3,5-triazinane(RDX) composite nanofibers. The governed electrospinning parameters, voltage, distance from the collector, flow rate, mandrel rotating speed... 相似文献
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本文介绍利用系数平面模型、回路波德图及二阶示性函数最小化技术实现跟踪系统人—机对话计算机辅助设计的方法。应用经典示性函数,将设计方案直接与适当的现行工程设计相联系,重点放在系数平面的通用区。结合具体实例,用示意图说明在系统发生变化的情况下,应用硬件反馈装置可减小性能的变化。利用观测器,以状态变量为基础的等效设计不会减小性能的变化。采用最小平方误差算法,可实现与性能指标相适应的低阶补偿器。 相似文献