基于压力测量的发动机汽缸磨损寿命预测方法

对不同摩托小时的某型坦克发动机进行了实车检测试验,采用压力传感器测量了发动机汽缸压缩压力,分析了汽缸压缩压力随发动机使用时间的变化趋势。分析了汽缸套磨损的特点及对发动机使用寿命的影响。针对发动机汽缸磨损的非线性特点,建立了人工神经网络预测模型,实现了对坦克发动机汽缸使用寿命的预测。     

基于DM642的X264移植及优化

X264算法需要经过移植和优化才能满足实时处理的要求。文中首先分析了如何向DM642平台上移植X264代码,通过存储器优化、线性汇编改写等一系列优化措施实现了摄像头实时采集视频、编码及显示。最后完成了采集、回放独立编码运行于后台的Ping-Pong机制。实验表明,对CIF格式视频编码性能由优化前不足0.5帧/s达到20帧/s以上,此时PSNR下降不足3 dB。     

A Squared-Chebyshev wavelet thresholding based 1D signal compression

In this paper a square wavelet thresholding method is proposed and evaluated as compared to the other classical wavelet thresholding methods (like soft and hard). The main advantage of this work is to design and implement a new wavelet thresholding method and evaluate it against other classical wavelet thresholding methods and hence search for the optimal wavelet mother function among the wide families with a suitable level of decomposition and followed by a novel thresholding method among the existing methods. This optimized method will be used to shrink the wavelet coefficients and yield an adequate compressed pressure signal prior to transmit it. While a comparison evaluation analysis is established, A new proposed procedure is used to compress a synthetic signal and obtain the optimal results through minimization the signal memory size and its transmission bandwidth. There are different performance indices to establish the comparison and evaluation process for signal compression; but the most well-known measuring scores are: NMSE, ESNR, and PDR. The obtained results showed the dominant of the square wavelet thresholding method against other methods using different measuring scores and hence the conclusion by the way for adopting this proposed novel wavelet thresholding method for 1D signal compression in future researches.     

圆柱壳在轴向压力作用下的稳定性和振动特性

利用Hamilton原理得出轴向压力作用下圆柱壳位移增量的动力学方程,推导了方程的解析解。通过数值计算,分析了轴向压力作用下圆柱壳的临界屈曲压力随壳体长度变化的曲线,讨论了壳体几何参数(L,h)变化和轴向力幅值变化对振动频率影响的变化曲线。数值计算结果表明,圆柱壳的临界屈曲压力与失稳模态紧密相关;圆柱壳的自振频率随壳体的长度增加而下降,随壳体的厚度增加而提高;圆柱壳的自振频率和最低频率随轴向压力的增大而下降。     

FeAlCrNbB金属间化合物复合涂层的制备与表征

研究开发了一种FeAlCrNbB新型喷涂粉芯丝材,并结合自动化高速电弧喷涂工艺制备了该材料的复合涂层,分析了涂层的常规力学性能、组织结构和油润滑条件下的滑动摩擦磨损性能,并和常规FeAl涂层进行了对比。结果显示:FeAlCrNbB涂层具有相对较高的显微硬度和拉伸结合强度、低的孔隙率,组织致密,形成了由Fe-Al金属间化合物相、氧化物以及少量非晶和纳米晶组成的复合结构,由于这种复合结构的材料特征,使涂层具备较好的耐磨损性能。     

材料力学性能纳米压入测试仪器发展综述

综述了材料力学性能纳米压入测试仪器的发展现状。阐述了纳米压入测试技术的发展历程;从驱动、载荷测量和位移测量3方面对目前材料力学性能纳米压入测试仪器的基本结构进行了比较分析;介绍了材料力学性能纳米压入测试仪器集成技术,包括影响压入深度测量精度的集成技术、观测技术、大载荷模块和高温试验模块等;最后,对未来材料力学性能纳米压力测试仪器的发展趋势作了展望。     

悬空管道固有频率的计算

在地质灾害作用下,输油管道下方的土层下陷或流失会造成管道悬空。当悬空管道发生弯曲变形时,两端埋地管道要对悬空管道产生影响。利用埋设段和悬空管道的受力平衡条件联立求解出两段管道的弯曲变形,并且讨论了不同土壤刚度和管道轴向力条件下悬空管道振动的固有频率,并和工程上推荐使用的简支梁和两端固支梁的静动态特性进行比较。管道大幅振动或共振是管道破坏的重要原因,准确计算悬空管道的固有频率,对悬空管道的静力分析、振动分析以及输油管道的完整性评价都有非常重要的意义。     

T300和JC2#纤维增强C/SiC复合材料力学性能对比

以聚碳硅烷(PCS)为先驱体,采用聚合物浸渍裂解法(PIP)分别制备得到T300碳纤维和JC2#碳纤维增强C/SiC复合材料。JC2#C/SiC复合材料具有优异的力学性能,抗弯强度和断裂韧性分别达到662MPa和19.5MPa.m1/2;T300 C/SiC复合材料表现出低强度、高脆性,其抗弯强度和断裂韧性不足前者的四分之一。T300 C/SiC复合材料低性能的根本原因在于T300纤维在PCS裂解过程中性能严重下降,复合材料中纤维与基体间存在强界面结合是另一个影响因素。     

3mm波段混凝土屏蔽材料的研究

在混凝土中添加标准砂,钢纤维,铁晶矿砂,炭纤维毡,氧化锌晶须,铁氧体,乙炔碳黑,羰基铁粉等材料,制成了具有微波吸收性能的混凝土屏蔽材料,以期能探索一条大型建筑及军事掩体的电磁防护的新途径。在3mm波段范围内对混凝土屏蔽材料进行了初步的实验研究,研究了不同材料、不同掺量下电磁波的吸收衰减特性,并分析了它们之间的关系,为进一步的研究指明了方向。     

Effects of jute fibre content on the mechanical and dynamic mechanical properties of the composites in structural applications

Due to notable characteristics, sustainability concept and environmental issues, hybridisation natural with synthetic fibres to fabricate composites have been rapidly gaining market share in different applications (structural, military, aerospace and automotive vehicles). Compression, tension and fatigue tests of various stacking sequences of plain jute/carbon reinforced (PVB) polyvinyl butyral by hot hydraulic press technique were experimentally conducted. Six types of fabricated composites with various constituents (jute, carbon and their hybrids) were fabricated and tested. Notably, fatigue lifetime of hybrids increases with increasing the carbon content relative to the jute fibre content. On the other hand, Jute composites possess high strain compared to pure carbon composite, which gives an overall improvement in mechanical behaviours. Interestingly, H1 hybrid with Carbon/Jute/Carbon sequences offers similar fatigue stiffness behaviour of H3 hybrid with Carbon/Jute/Carbon/Jute sequences when subjected to cyclic loading. Carbon composite (C) exhibited the highest fatigue resistance, whiles jute composite (J) possessed the highest strain and semi brittle trends in both mechanical and fatigue performance. Results concluded that plain jute fibres could partially replace high-cost synthetic carbon fibres to produce more eco-friendly hybrids to be utilised in different composites industries.