Fracture toughness and fatigue crack growth analysis of 7050-T7451 alloy thick plate with different thicknesses

The strength,fracture toughness and fatigue crack growth resistance of 7050-T7451 aluminum alloy plate with different thicknesses(35 mm and 160 mm) were investigated by means of optical microscope,scanning electron microscope and transmission electron microscope.The results show that thicker plate has lower strength and fracture toughness but higher fatigue crack growth resistance,by comparison to the thinner plate.The drop of strength is mainly attributed to grain coarsening in the thicker plate,and the increased degree of recrystallization results in the loss of KIC.However,the coarsened grains in the thicker plate make cracks deflected and closure effect enhanced due to surface roughness increased.For both of plates,in the fracture surface subjected plain strain,a transition from transgranular dimpled fracture to intergranular dimpled fracture is observed during the fracture process.     

废弃 ABS 电镀件表面金属退镀技术研究进展

ABS电镀件因其质轻、美观、耐腐蚀、耐磨损等优点而被广泛应用于汽车、玩具、卫浴和电器电子产品等领域。然而,随着这些产品报废量的增加,废弃ABS电镀件的数量也在逐年增加。因此,对废弃ABS电镀件进行表面金属镀层退镀处理,实现金属和非金属的资源化回收,受到人们越来越多的关注。总结了国内外ABS电镀件表面金属镀层退镀的研究,并分析了各种不同退镀方法的优缺点。     

汽车底盘的现代金属成形技术

随着汽车轻量化的发展,迫切需要开发一些新工艺来满足不降低汽车零部件性能而减轻零件的重量。汽车底盘作为支承、安装汽车各部件的总成,底盘零件是汽车的重要结构安全件,要求有良好的强度、刚度性能、抗疲劳性能及综合性能,其轻量化相对难度较大。主要针对广泛应用于汽车底盘的管材液压成形技术、半固态成形技术进行了介绍,并将这些技术的开发情况、应用情况、设备等情况进行了概述。     

KDF-2卷烟机高速接纸系统改造与实验研究

对某厂使用的KDF-2成型机的接纸系统的工作状态和存在的问题进行了分析,应用现代机械设计理论和PLC控制技术对现有的接纸系统进行结构和控制系统的改造,把机械无级变速箱传动改为由三个伺服电机独立驱动并采用PLC控制,把盘纸降速拼接改为高速拼接,从而有效地解决了更换盘纸带来的滤棒吸阻、重量在降速时波动大．影响设备使用效能等问题,改造后使滤棒吸阻,重量更容易控制,提升了设备性能。     

纳米陶瓷的制备成型技术研究

传统陶瓷材料因其具有耐高温、耐腐蚀、强度高、硬度大等优点,已成为人们普遍关注的对象．但传统陶瓷的脆性问题一直是阻碍陶瓷材料发展的主要因素之一,而由纳米晶组成的陶瓷材料则具有高韧性、低温超塑性等特点．文章重点分析了纳米晶陶瓷传统成形技术的研究现状及各种技术的优缺点,并探讨纳米晶陶瓷的制备成型技术发展方向,指出使用激光成型技术制备高性能纳米晶陶瓷零件是可以期待的．     

镁晶板-钢筋混凝土叠合楼板耐火性能试验研究

镁晶板—钢筋混凝土叠合楼板的下层为预制新型耐火材料镁晶板,上层为现浇钢筋混凝土板。为了研究镁晶板—钢筋混凝土叠合楼板在不同荷载比下的耐火性能及耐火等级,对3块叠合楼板试件进行ISO-834标准升温下的受火试验,得到叠合板不同位置的受火时间—温度曲线和受火时间—跨中位移曲线。试验表明,叠合板具有良好的耐火性能,耐火极限可达到1.5 h以上。利用有限元软件ABAQUS分析了试件的耐火性能,通过与试验结果对比,验证了模型的可靠性,进而采用模型考察荷载比、镁晶板厚度、混凝土保护层厚度、钢筋和混凝土的强度对叠合楼板耐火极限的影响。分析表明,荷载比和镁晶板厚度对叠合楼板耐火极限影响较大。基于参数分析结果,给出不同荷载比和不同镁晶板厚度叠合板的耐火极限。     

汽车牌照字符识别系统设计

随着交通事业的迅速发展,人工管理方式已不能满足实际的需求,针对这一问题,提出了汽车牌照字符识别系统设计,采用了数字图像处理技术、车牌定位技术、车牌字符分割技术、BP神经网络识别技术来解决车牌字符的识别问题,研究了图像预处理、边缘提取、车牌定位、字符分割、字符识别5部分内容,并给出了BP神经网络实现车牌字符的识别,实验表明,此方法能实现良好的定位精确度和较高的识别率.     

复式河槽过流能力非线性研究

传统方法不能准确预测复式河槽过流能力。针对这一不足，本文采用系统动力学方法探寻复式河槽过流能力的计算。通过分析英国科学工程研究协会洪水水槽设(SERC-FCF)的大量的系列水槽实验成果，发现滩槽Darcy-Weisbach阻力系数比值随着相对水深的增加而减小。主槽阻力系数随着相对水深的变化而变化，呈抛物线分布。根据获得的阻力系数关系，运用系统动力学方法，建立了洪水漫滩后，复式河槽过流能力的系统动力学模型。计算结果表明：该模型能确定水位流量关系，其模拟值与实测值吻合较好，其相对误差的绝对值仅在3％左右。     

Convolutional Neural Network Based on Spatial Pyramid for Image Classification

A novel convolutional neural network based on spatial pyramid for image classification is proposed. The network exploits image features with spatial pyramid representation. First, it extracts global features from an original image, and then different layers of grids are utilized to extract feature maps from different convolutional layers. Inspired by the spatial pyramid, the new network contains two parts, one of which is just like a standard convolutional neural network, composing of alternating convolutions and subsampling layers. But those convolution layers would be averagely pooled by the grid way to obtain feature maps, and then concatenated into a feature vector individually. Finally, those vectors are sequentially concatenated into a total feature vector as the last feature to the fully connection layer. This generated feature vector derives benefits from the classic and previous convolution layer, while the size of the grid adjusting the weight of the feature maps improves the recognition efficiency of the network. Experimental results demonstrate that this model improves the accuracy and applicability compared with the traditional model.     

淮北平原地基分层与承载力的BP网络预测方法

针对淮北平原地质土成层性和不均匀性显著的特点,提出了多元互层地基分层和承载力分层计算的BP神经网络预测方法。以钻探取样、静力触探试验和螺旋板载荷试验、平板载荷试验原位测试结果进行对比,认为比贯入阻力ps值可以作为互层地基分层和地质土承载力预测的评价指标,并以此为基础采用BP神经网络的梯度下降算法和共轭梯度算法分别建立土质分层和承载力预测的模型,并将两种算法的计算结果进行了对比分析。结果表明：比贯入阻力值可作为淮北平原互层地基的土质分层和承载力预测的评价指标;BP神经网络的梯度下降算法和共轭梯度算法均对土质类型的识别和地基承载力的预测具有良好的效果,满足实际工程的精度要求,但是前者的计算效率明显低于后者。     

基于WNMF和聚焦点定位分析的多聚焦图像融合方法

在非负矩阵分解(NMF)图像融合方法的基础上,提出一种基于加权非负矩阵分解(WNMF)和聚焦点定位分析的多聚焦图像融合方法。该方法利用光学系统成像原理及点扩散函数在光学成像过程中的作用,判定多聚焦图像中的聚焦点的近似位置,并以此为基础构建一个权值矩阵,然后将加权非负矩阵算法应用于图像融合中,最后得到一幅各部分都聚焦清晰的图像。实验结果表明,通过本文提出的方法得到的融合图像效果优于普通的非负矩阵分解方法、小波变换法方法及拉普拉斯塔式方法。     

带扰流孔波纹板的传热和阻力特性

通过数值模拟方法分析DU-1（双皱纹型）波纹板通道内不同Re数下的温度场、速度场以及压力场,提出在DU-1板上开圆形扰流孔以增强传热效果. 针对波纹通道内波纹板和定位板与空气层传热接触面积的不同,拓展了单吹技术数学模型. 考虑扰流孔孔径、间距、位置以及排列方式4种影响因素,利用正交实验法对开扰流孔后DU-1板的传热和阻力特性进行系统研究,分析4种因素的影响规律. 利用综合平衡分析法得出提高DU-1板传热效果和降低流动阻力的最佳水平组合.通过试验验证发现,该带扰流孔DU-1波纹板相对于无扰流孔时传热特性增加19.87%,流动阻力减少24.53%.     

斜盘式锥齿少齿差减速器传动件加工新方法

对斜盘式锥齿少齿差行星减速器的一些重要传动元件的制造方案进行了系统研究和论证．主要包括内啮合锥齿轮副、输入轴-斜盘、歪轴的制造及装配、检测工艺等．通过引入内锥齿轮副鼓形齿修正等新工艺理论，为斜盘式锥齿少齿差行星传动的工业应用奠定了基础．     

对称型梯度功能材料的瞬态热应力强度因子

采用摄动法推导出无限大对称型梯度功能材料平板的一维非定常温度场及非定常热应力场的解析表达式 ,并采用权函数法计算了受热冲击的含双边裂纹的对称型梯度功能材料平板的瞬态热应力强度因子 .通过两种Al2 O3 TiC系梯度功能陶瓷平板表面冷却条件下的计算实例并与均质陶瓷材料对比 ,分析了材料的热 物理性能分布规律对瞬态热应力强度因子的影响 ,并提出高抗热震性梯度功能陶瓷的设计原则     

OFDM系统信道估计性能分析

介绍了OFDM系统中的信道估计技术,着重分析了基于导频插入的信道估计方法,叙述了基于最小二乘(LS)和线性最小均方误差(LMMSE)的信道估计方法,应用简化的LMMSE即SVD-LMMSE方法和卡尔曼滤波方法对信道进行估计,采用广义平稳非相关散射下的多径时变瑞利信道模型,对各个算法进行了仿真试验,得出不同算法下信道估计的误比特曲线,比较了各个算法的性能。仿真结果表明:基于MMSE准则的信道估计比基于LS准则的估计有更好的性能,但前者复杂度较高。     

钢水余热衬瓷层磨损机理

针对工业生产中摩擦磨损造成零件失效的现象,对材料表面耐磨损问题进行研究.采用钢水余热衬瓷技术,借助钢水散出的热量把陶瓷复合粉料烧结在铸钢件表面,形成了高耐磨性衬瓷层.磨损试验结果表明,衬瓷层磨损失重率是淬火45^#钢的1/80; 用SEM分析了涂层的显微组织,发现陶瓷颗粒比较均匀地分布在金属基体组织中,颗粒被基体金属紧紧包覆.分析认为,这些陶瓷颗粒承载着摩擦过程的大部分载荷,这种显微组织是耐磨性大幅度提高的重要原因之一.     

聚丙烯酸酯乳液改性水性聚氨酯性能的研究

采用4,4’-二苯基甲烷二异氰酸酯(MDI)合成了聚酯型阴离子水性聚氨酯(WPU)乳液,并与聚丙烯酸酯(PA)乳液共混制备出改性水性聚氨酯乳液,研究不同含量的PA对水性聚氨酯的结构和性能的影响。结果表明:复合乳液中PU和PA的相容性较好,共混改性后的PU/PA膜比纯的水性聚氨酯膜的耐水性能和耐热性能有明显的提高。     

Preparation and Characterization of Lignosulfonate Intercalated Layered Double Hydroxides and Their Application in Improving Ultraviolet Aging Resistance for Bitumen

In order to develop economically anti-ultraviolet(UV) aging additives to bitumen and extend the comprehensive utilization of lignin materials, lignosulfonate(LS) was selected to intercalate into layered double hydroxides(LDHs), then the LS intercalated LDHs(LS-LDHs) were applied to improve UV aging resistance of bitumen. With the characterization of X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, chemical analysis and scanning electron microscopy(SEM), LS was successfully intercalated into the galleries of LDHs. The ultraviolet and visible(UV-vis) absorbance curves showed LS-LDHs had excellent UV absorptive ability from 200 to 400 nm. Thermogravimetry and differential scanning calorimetry(TG-DSC) indicated LS-LDHs could have a good thermal stability during the processing of bitumen. Compared with the LDHs, the LS-LDHs exhibited better performance in UV aging resistance of bitumen.     

Dynamic response of ultralight all-metallic sandwich panel with 3D tube cellular core to shallow-buried explosives

The underbody of a vehicle system, either military or civil, is typically made of a relatively thin metallic plate, thus vulnerable to mine blast attacks. To improve the blast resistance, a multitude of protective structures have been proposed as attachments to the thin plate. In the present study, a novel ultralight all-metallic sandwich panel with three-dimensional(3D) tube cellular cores mounted to the vehicle underbody was envisioned as such a protective system. A metallic substrate(mimicking vehicle bottom)was placed above the proposed sandwich panel to construct a sandwich-substrate combinative structure. A series of sandwich panels having 3D tube cellular cores were fabricated via argon protected welding and laser welding. Mechanical responses of the combinative structure subjected to the denotation of 6 kg TNT explosives shallow-buried in dry sand were experimentally measured. Full numerical simulations with the method of finite elements(FE) were subsequently carried out to explore the physical mechanisms underlying the observed dynamic performance and quantify the effects of key geometrical parameters and connection conditions of the protective system. The performance of the proposed sandwich panel under shallow-buried explosives was also compared with competing sandwich constructions having equal mass. Finally, a preliminary optimal design of the 3D tube cellular core was carried out.     

全自适应阵列中的逆QR分解算法

提出了一种在全自适应阵列中的逆QR分解算法,给出了它的Sysrolic实现方法。该算法可以很容易地映射到Systolic结构上,仅需一个Systolic阵便能得到最佳权矢量。并且同QR分解算法一样,它是直接对数据矩阵进行处理,且变换采用酉阵,保持了很好的数值稳定性。